full funded jaw crusher

jaw crusher working principle

jaw crusher working principle

A sectional view of the single-toggle type of jaw crusher is shown below.In one respect, the working principle and application of this machine are similar to all types of rock crushers, the movable jaw has its maximum movement at the top of the crushing chamber, and minimum movement at the discharge point. The motion is, however, a more complex one than the Dodge motion, being the resultant of the circular motion of the eccentric shaft at the top of the swing jaw. combined with the rocking action of the inclined toggle plate at the bottom of this jaw. The motion at the receiving opening is elliptical; at the discharge opening, it is a thin crescent, whose chord is inclined upwardly toward the stationary jaw. Thus, at all points in the crushing chamber, the motion has both, vertical and horizontal, components.

It will be noted that the motion is a rocking one. When the swing jaw is rising, it is opening, at the top, during the first half of the stroke, and closing during the second half, whereas the bottom of the jaw is closing during the entire up-stroke. A reversal of this motion occurs during the downstroke of the eccentric.

The horizontal component of motion (throw) at the discharge point of the single-toggle jaw crusher is greater than the throw of the Dodge crusher at that point; in fact, it is about three-fourths that of Blake machines of similar short-side receiving-opening dimensions. The combination of favorable crushing angle, and nonchoking jaw plates, used in this machine, promotes a much freer action through the choke zone than that in the Dodge crusher. Capacities compare very favorably with comparable sizes of the Blake machine with non-choking plates, and permissible discharge settings are finer. A table of ratings is given.

The single-toggle type jaw crusher has been developed extensively. Because of its simplicity, lightweight, moderate cost, and good capacity, it has found quite a wide field of application in portable crushing rigs. It also fits into the small, single-stage mining operation much better than the slower Dodge type. Some years since this type was developed with very wide openings for reduction crushing applications, but it was not able to seriously challenge the gyratory in this field, especially when the high-speed modern versions of the latter type were introduced.

Due to the pronounced vertical components of motion in the single-toggle machine, it is obvious that a wiping action takes place during the closing strokes; either, the swing jaw must slip on the material, or the material must slip along the stationary jaw. It is inevitable that such action should result in accelerated wear of the jaw plates; consequently, the single-toggle crusher is not an economical machine for reducing highly abrasive, or very hard, tough rock. Moreover, the large motion at the receiving opening greatly accentuates shocks incidental to handling the latter class of material, and the full impact of these shocks must be absorbed by the bearings in the top of the swing jaw.

The single-toggle machine, like the Dodge type, is capable of making a high ratio-of-reduction, a faculty which enables it to perform a single-stage reduction of hand-loaded, mine run ore to a suitable ball mill, or rod mill, feed.

Within the limits of its capacity, and size of receiving openings, it is admirably suited for such operations. Small gravel plant operations are also suited to this type of crusher, although it should not be used where the gravel deposit contains extremely hard boulders. The crusher is easy to adjust, and, in common with most machines of the jaw type, is a simple crusher to maintain.

As rock particles are compressed between the inclined faces of the mantle and concaves there is a tendency for them to slip upward. Slippage occurs in all crushers, even in ideal conditions. Only the particles weight and the friction between it and the crusher surfaces counteract this tendency. In particular, very hard rock tends to slip upward rather than break. Choke feeding this kind of material can overload the motor, leaving no option but to regulate the feed. Smaller particles, which weigh less, and harder particles, which are more resistant to breakage, will tend to slip more. Anything that reduces friction, such as spray water or feed moisture, will promote slippage.

Leading is a technique for measuring the gap between fixed and moveable jaws. The procedure is performed while the crusher is running empty. A lead plug is lowered on a lanyard to the choke point, then removed and measured to find out how much thickness remains after the crusher has compressed it. This measures the closed side setting. The open side setting is equal to this measurement plus the throw of the mantle. The minimum safe closed side setting depends on:

Blake (Double Toggle) Originally the standard jaw crusher used for primary and secondary crushing of hard, tough abrasive rocks. Also for sticky feeds. Relatively coarse slabby product, with minimum fines.

Overhead Pivot (Double Toggle) Similar applications to Blake. Overhead pivot; reduces rubbing on crusher faces, reduces choking, allows higher speeds and therefore higher capacities. Energy efficiency higher because jaw and charge not lifted during cycle.

Overhead Eccentric (Single Toggle) Originally restricted to sampler sizes by structural limitations. Now in the same size of Blake which it has tended to supersede, because overhead eccentric encourages feed and discharge, allowing higher speeds and capacity, but with higher wear and more attrition breakage and slightly lower energy efficiency. In addition as compared to an equivalent double toggle, they are cheaper and take up less floor space.

Since the jaw crusher was pioneered by Eli Whitney Blake in the 2nd quarter of the 1800s, many have twisted the Patent and come up with other types of jaw crushers in hopes of crushing rocks and stones more effectively. Those other types of jaw crusher inventors having given birth to 3 groups:

Heavy-duty crushing applications of hard-to-break, high Work Index rocks do prefer double-toggle jaw crushers as they are heavier in fabrication. A double-toggle jaw crusher outweighs the single-toggle by a factor of 2X and well as costs more in capital for the same duty. To perform its trade-off evaluation, the engineering and design firm will analyze technical factors such as:

1. Proper selection of the jaws. 2. Proper feed gradation. 3. Controlled feed rate. 4. Sufficient feeder capacity and width. 5. Adequate crusher discharge area. 6. Discharge conveyor sized to convey maximum crusher capacity.

Although the image below is of a single-toggle, it illustrates the shims used to make minor setting changes are made to the crusher by adding or removing them in the small space between the crushers mainframe and the rea toggle block.

The jaw crusher discharge opening is the distance from the valley between corrugations on one jaw to the top of the mating corrugation on the other jaw. The crusher discharge opening governs the size of finished material produced by the crusher.

Crusher must be adjusted when empty and stopped. Never close crusher discharge opening to less than minimum opening. Closing crusher opening to less than recommended will reduce the capacity of crusher and cause premature failure of shaft and bearing assembly.

To compensate for wear on toggle plate, toggle seat, pitman toggle seat, and jaws additional shims must be inserted to maintain the same crusher opening. The setting adjustment system is designed to compensate for jaw plate wear and to change the CSS (closed side setting) of the jaw crusher. The setting adjustment system is built into the back frame end.

Here also the toggle is kept in place by a compression spring. Large CSS adjustments are made to the jaw crusher by modifying the length of the toggle. Again, shims allow for minor gap adjustments as they are inserted between the mainframe and the toggle block.

is done considering the maximum rock-lump or large stone expected to be crushed and also includes the TPH tonnage rate needing to be crushed. In sizing, we not that jaw crushers will only have around 75% availability and extra sizing should permit this downtime.

As a rule, the maximum stone-lump dimension need not exceed 80% of the jaw crushers gape. For intense, a 59 x 79 machine should not see rocks larger than 80 x 59/100 = 47 or 1.2 meters across. Miners being miners, it is a certainty during day-to-day operation, the crusher will see oversized ore but is should be fine and pass-thru if no bridging takes place.

It will be seen that the pitman (226) is suspended from an eccentric on the flywheel shaft and consequently moves up and down as the latter revolves, forcing the toggle plates outwards at each revolution. The seating (234) of the rear toggle plate (239) is fixed to the crusher frame; the bottom of the swing jaw (214) is therefore pushed forward each time the pitman rises, a tension rod (245) fitted with a spring (247) being used to bring it back as the pitman falls. Thus at each revolution of the flywheel the movable jaw crushes any lump of ore once against the stationary jaw (212) allowing it to fall as it swings back on the return half-stroke until eventually the pieces have been broken small enough to drop out. It follows that the size to which the ore is crushed.

The jaw crusher is not so efficient a machine as the gyratory crusher described in the next paragraph, the chief reason for this being that its crushing action is confined to the forward stroke of the jaw only, whereas the gyratory crusher does useful work during the whole of its revolution. In addition, the jaw crusher cannot be choke-fed, as can the other machine, with the result that it is difficult to keep it working at its full capacity that is, at maximum efficiency.

Tables 5 and 6 give particulars of different sizes of jaw crushers. The capacity figures are based on ore weighing 100 lb. per cubic foot; for a heavier ore, the figures should be increased in direct proportion to its weight in pounds per cubic foot.

The JAW crusher and the GYRATORY crusher have similarities that put them into the same class of crusher. They both have the same crushing speed, 100 to 200 R.P.M. They both break the ore by compression force. And lastly, they both are able to crush the same size of ore.

In spite of their similarities, each crusher design has its own limitations and advantages that differ from the other one. A Gyratory crusher can be fed from two sides and is able to handle ore that tends to slab. Its design allows a higher-speed motor with a higher reduction ratio between the motor and the crushing surface. This means a dollar saving in energy costs.

A Jaw crusher on the other hand requires an Ely wheel to store energy. The box frame construction of this type of crusher also allows it to handle tougher ore. This design restricts the feeding of the crusher to one side only.

The ore enters from the top and the swing jaw squeezes it against the stationary jaw until it breaks. The broken ore then falls through the crusher to be taken away by a conveyor that is under the crusher.Although the jaws do the work, the real heart of this crusher is the TOGGLE PLATES, the PITMAN, and the PLY WHEEL.

These jaw crushers are ideal forsmall properties and they are of the high capacity forced feed design.On this first Forced Feed Jaw Crusher, the mainframe and bumper are cast of special alloy iron and the initial cost is low. The frame is ribbed both vertically and horizontally to give maximum strength with minimum weight. The bumper is ruggedly constructed to withstand tremendous shock loads. Steel bumper can be furnished if desired. The side bearings are bronze; the bumper bearings are of the antifriction type.

This bearing arrangement adds both strength and ease of movement. The jaw plates and cheek plates are reversible and are of the best-grade manganese steel. The jaw opening is controlled by the position of an adjustable wedge block. The crusher is usually driven by a V-to-V belt drive, but it can be arranged for either V-to-flat or fiat belt drive. The 8x10 size utilizes a split frame and maybe packed for muleback transportation. Cast steel frames can be furnished to obtain maximum durability.

This second type of forced feed rock crusher is similar in design to the Type H listed above except for having a frame and bumper made of cast steel. This steel construction makes the unit lighter per unit of size and adds considerable strength. The bearings are all of the special design; they are bronze and will stand continuous service without any danger of failure. The jaw and cheek plates are manganese steel; and are completely reversible, thus adding to their wearing life. The jaw opening is controlled by the position of an adjustable wedge block. The crushers are usually driven by V-to-V but can be arranged for V-to-flat and belt drive. The 5x6 size and the 8x10 size can be made with sectionalized frame for muleback transportation. This crusher is ideal for strenuous conditions. Consider a multi jaw crusher.

Some jaw crushers are on-floor, some aboveground, and others underground. This in many countries, and crushing many kinds of ore. The Traylor Bulldog Jaw crusher has enjoyed world wide esteem as a hard-working, profit-producing, full-proof, and trouble-free breaker since the day of its introduction, nearly twenty years ago. To be modern and get the most out of your crushing dollars, youll need the Building breaker. Wed value the privilege of telling you why by letter, through our bulletins, or in person. Write us now today -for a Blake crusher with curved jaw plates that crush finer and step up production.

When a machine has such a reputation for excellence that buyers have confidence in its ability to justify its purchase, IT MUST BE GOOD! Take the Type G Traylor Jaw Crusher, for instance. The engineers and operators of many great mining companies know from satisfying experience that this machine delivers a full measure of service and yields extra profits. So they specify it in full confidence and the purchase is made without the usual reluctance to lay out good money for a new machine.

The success of the Type G Traylor Jaw Crusheris due to several characteristics. It is (1) STRONG almost to superfluity, being built of steel throughout; it is (2) FOOL-PROOF, being provided with our patented Safety Device which prevents breakage due to tramp iron or other causes of jamming; it is (3) ECONOMICAL to operate and maintain, being fitted with our well-known patented Bulldog Pitman and Toggle System, which saves power and wear by minimizing frictionpower that is employed to deliver increased production; it is (4) CONVENIENT to transport and erect in crowded or not easily accessible locations because it is sectionalized to meet highly restrictive conditions.

Whenever mining men need a crusher that is thoroughly reliable and big producer (which is of all time) they almost invariably think first of a Traylor Type G Jaw Crusher. By experience, they know that this machine has built into it the four essentials to satisfaction and profit- strength, foolproofness, economy, and convenience.

Maximum STRENGTH lies in the liberal design and the steel of which crushers parts are made-cast steel frame, Swing Jaw, Pitman Cap and Toggles, steel Shafts and Pitman rods and manganese steel Jaw Plates and Cheek Plates. FOOLPROOFNESS is provided by our patented and time-tested safety Device which prevents breakage due to packing or tramp iron. ECONOMY is assured by our well-known Bulldog Pitman and Toggle System, which saves power and wear by minimizing friction, the power that is used to deliver greater productivity. CONVENIENCE in transportation and erection in crowded or not easily accessible locations is planned for in advance by sectionalisation to meet any restrictive conditions.

Many of the worlds greatest mining companies have standardized upon the Traylor Type G Jaw Crusher. Most of them have reordered, some of them several times. What this crusher is doing for them in the way of earning extra dollars through increased production and lowered costs, it will do for you! Investigate it closely. The more closely you do, the better youll like it.

how to properly install and use jaw crusher | hxjq

how to properly install and use jaw crusher | hxjq

Jaw Crusher is a kind of mining equipment used for primary and secondary crushing. It is widely used in medium-sized crushing of various ores and bulk materials in mining, smelting, building materials, highway, railway, water conservancy, and chemical industries. It has a wide variety and a wide range of uses, making it the perfect choice for mining and quarrying.

Of course, for the customers, in addition to the brand and quality of jaw crusher, the installation and use methods also make them particularly concerned. In order to meet the needs of users and help them solve the most concerned issues, we will talk about how to install and use it next.

From its basic structure, we can easily see that its structure is complicated with many parts. Therefore, during the installation, the user should pay more attention to it and must be installed under the guidance of the manufacturer's technical personnel and in conjunction with the installation and use instructions of the equipment. Pay more attention to the details to ensure that nothing is lost.

Since the working area of the jaw crusher is mostly mountainous, it is necessary to thoroughly investigate whether the topography of the mine is suitable for concrete piling before installation, and according to the site topographic conditions, foundation soil conditions, pile arrangement, and length, and pile frame factors such as ease of movement determine the piling order, and it should also be considered that the depth of the piles should be basically the same, and the foundation soil is even and tight.

The jaw crusher is mainly installed on the concrete foundation. Therefore, the stability of the foundation will affect the stability of the machine. If the foundation is stable, the vibration will be less during the production process, and the equipment can stably run. If not, the jaw crusher will easily generate loud noise and vibration when it is working, which not only affects the production process but also causes the equipment to break away from the foundation. It will have a bad influence on service life, and more importantly, cause personal safety hazards for workers, so the pouring of the foundation is very important.

The jaw crusher is installed on the concrete foundation. In order to reduce vibration and hum, a layer of hardwood, rubber or other vibration-absorptive material should be placed between the frame and the concrete. The horizontal and vertical levels of the frame mounted on the wooden base shall be in accordance with the requirements, and the backing between the frame foot and the soil shall be flat, uniform and stable. Before installing, the sliding bearing is researched and placed and then placed in the bearing housing. The horizontal value and the eccentricity deviation value are measured by the level meter. If the inner diameter is within the allowable range, the eccentric shaft can be placed on the bearing.

Before the shaft and bearing assembly, the sliding bearing needs to be researched and then placed in the sliding bearing housing, and the horizontality and coaxiality of the placement are detected by the level meter. If the measurement result meets the requirements, then install the eccentric shaft on the bearing and check the fit between the shaft and the bearing by applying red dan powder on the journal.

If the surface of the plain bearing is too high, further scraping is required until the high point between the contact surfaces disappears. Finally, a certain amount of lubricating oil is applied between the bearing housing and the bearing to reduce shaft wear. The contact area between the eccentric shaft sliding and the frame should be no less than 80%, and the gap between them should be less than 0.07 mm.

The rod bolt should be assembled after the main bearing and the eccentric shaft are ground. Before assembly, check it carefully, and then use the crane to place the rod bolt slightly lower than its normal position in the crusher. Wash the upper and lower bearings of the rod bolt and lubricate them with thin oil, and then install the bearing, main shaft, upper bearing, and upper shell. Lifting the rod bolt, then install the bolts and tighten them. The bracket should be added when the oil leakage occurs due to poor fitting. When conditions permit, it is best to assemble the complete set of rod bolts and main shaft outside and load them into the frame once with the crane.

The smash or installation of toggle plate can be removed by loosening the tension spring nut, removing the spring, and then using a chain or a wire rope to tie the lower part of the movable jaw plate, and then pulling the wire rope with the driving, so that the movable jaw is close to the fixed jaw, and the rear toggle plate automatically drop off, just inverted repeat the above steps in the installation.

The movable jaw plate is assembled by using the pre-assembled parts, that is, the movable jaws, the movable shaft, the movable dental plate, and the bracket are assembled in advance, and then hoisted in the frame by a crane. The sliding bearing is first ground and placed in the frame bearing housing to measure the deviation of the slope and the coaxiality. Then apply oil to the bearing and journal surfaces and place the movable jaw in the bearing.

The dental plate is the fastest worn part of the crusher and requires frequent replacement. The dental plate is fixed on the front wall and the movable jaw by bolts or wedges. The contact surface must be straight, and no lifting phenomenon is allowed. Otherwise, it should be solved in time. Since the inside of the front wall of the frame is not machined, it is better to lay a layer of the soft metal gasket between the back of the fixed dental plate and the forearm of the frame to ensure that the two are closely fitted.

The above is the installation method for the parts of the jaw crusher. However, in order to make the equipment run stably and maximize the benefits for the user, in addition to the correct installation of the jaw crusher, the rational use is also crucial, which is related to whether the assembled jaw crusher will run in long-term stable production and create a constant value for customers.

Before the jaw crusher is started, the equipment must be thoroughly inspected, for example, to check if the connecting bolts are loose; whether the protective cover of the pulley and the flywheel is intact; whether the tension of the V-belt and the tension spring is appropriate; whetherallthe oil is filled; whether the lubrication system is integrated; whether the electrical equipment and signal system are normal, etc. In addition, before starting the crusher, the oil pump motor and cooling system should be started first. After 3-4 minutes, when the oil pressure and flow indicator are normal, the motor of the crusher can be started.

During operation, attention must be paid to increase ore uniformly, and the ore is not allowed to be filled with crushing chambers. The maximum size of the ore should not be greater than 0.85 times the width of the ore. At the same time, the non-crushing objects such as the shovel teeth of the shovel and the drill bits of the rig are strictly prevented from entering the crusher. Once it is found that these non-broken objects enter the crushing chamber and pass through the discharge port of the machine, the relevant personnel should be immediately notified to take them out in time to avoid entering the next section of the crusher, causing serious equipment accidents;

During the operation, you should always pay attention to prevent the large nuggets from getting stuck in the feeding port of the crusher. If it happens, be sure to use iron hooks to turn the ore; if it needs to be taken out of the crushing chamber, special equipment should be used. It is strictly forbidden to carry out these tasks by hand;

If the crushing chamber is blocked, the ore should be suspended. After the ore in the crushing chamber is broken, the ore can continue to be fed, but the crusher is not allowed to stop running at this time;

Regular inspections should be taken to observe the working conditions and bearing temperatures of the various components of the crusher by means of viewing, listening, and touching. Usually, the bearing temperature must not exceed 60 to prevent the alloy bush from melting or being burnt tile accident. When it is found that the bearing temperature is very high, do not stop the operation immediately. Effective measures should be taken to reduce the bearing temperature in time, such as increasing the oil supply, forced ventilation or water cooling. After the bearing temperature drops, it can be stopped for inspection and troubleshooting;

When the crusher stops, it must be stopped in the order of the production process. First of all, it is necessary to stop feeding the mine. After the ore in the crushing chamber is completely discharged, the crusher and the belt conveyor should be stopped, and then is the motor of the oil pump. It should also be noted that the crusher suddenly stops for some reasons. Before the accident is processed and ready to drive, the accumulated ore in the crushing chamber must be removed. The installation of the jaw crusher and the method of use directly affects the quality of the finished product and the smooth progress of production. Mastering the correct installation and use of the jaw crusher is an effective guarantee for improving the efficiency of crushing work and product quality.

rock crushing

rock crushing

An objective of the present contract is to provide a concept for the design of a portable underground hard rock crusher in order to insure that future development will lead to maximum utilization by industry. The preceding section has concluded that the industry can indeed use such a machine and that, within desired performance and dimensional parameters defined by this study, no standard crushers are suitable for handling hard rock.

As indicated in Section 3, and stated in standard references such as (5),and (6), hard rock of large feed dimensions is best handled by jaw and gyratory crushers. This conclusion is of little value for present purposes unless we can determine fundamentally why these machines, and only these machines, are satisfactory. Using this knowledge, then, we stand a much better chance of devising satisfactory new concepts.

The following section describes three new crusher concepts, one of which, though earlier thought to be an attractive new concept, can be discarded (for hard rock) because it clearly does not have the third fundamental characteristic mentioned above.

In view of the strong, and perhaps obvious, conclusion that portable crushers will accentuate the need for breaking occasional oversize feed fragments, some thoughts on handling this problem are also presented.

Each of the following subsections presents a new crusher concept for hard-rock, portable, underground applications. The first, which will be rejected, is discussed in part to illustrate the importance of the previously noted fundamental characteristics of successful hard rock crusher concepts. The third, on the other hand, indicates that, while valid for reasonably conventional concepts, it would be inappropriate and restrictive to apply such conventional design criteria to unconventional concepts.

Based on the successful development of the RAPIDEX conical reamer, a skewed rolling element crusher was conceived using the same principles. The conical reamer is a roller cutter device which s self-advancing by virtue of its wedge-like shape and skewed rollers. A crusher using the principles would be essentially inside out, and it would self-feed rock fragments between the rollers.

Figure 13 is a sketch of basic concept, which consists of opposed rollers arranged in a row of V shaped pairs. The rollers are powered (i.e., rotated) and skewed (tilted forward) such that a rock fragment placed within the V will be simultaneously propelled forward and drawn downward until it is crushed. Product size is determined by the (adjustable) axial space between rollers. Downward and outward flow of product would provide quick clearing of smaller material, thus allowing effective crushing of larger material carried forward between the rollers.

While all of these features would be desirable, it was noted that a large fragment could simply fall downward between two V sections rather than feed downward gradually as intended. From this position a fragment would then be driven forward and crushed substantially in a single, large compaction, in violation of the third listed desirable characteristic of a hard rock crusher. Large downward motion between rollers could be avoided, or at least reduced, by placing baffles between rollers, but this would also stop the free discharge of undersize materialone of the major claimed virtues of the concept.

In conclusion, the V roller crusher is judged to be unsuitable for hard rock crushing. It would be suitable, and would provide a good, free flowing design, for coarse crushing of softer of friable materials that can now be handled by conventional roll crushers.

The jaw crusher, either Blake or overhead eccentric as appropriate. is the conventional machine most nearly satisfactory for the subject hard rock portable application. It is entirely satisfactory in terms of crushing performance feed size, hard rock capability, reduction ratio, product characteristics, throughput, and economy. However, it cannot meet the necessary installed dimension requirements, particularly with regard to headroom. Although basic crusher dimensions (i.e., the jaws themselves) are not too bad, the conventional top feed arrangement requires much too much headroom, particular if slabby material (which would have to be vertically oriented) is to be handled.

It is appropriate, then, to search for a horizontal feed jaw-crusher concept. One obvious approach, tipping a basically conventional jaw crusher on its edge, (i.e. with the eccentric shaft vertical has been attempted in this country, and several such units are said to be in use in an iron mine hematite) in Europe. All use a horizontal chain conveyor travelling just beneath the lower edge of the jaws to move material through the machine. Although this configuration obviously does work, it must do so at some sacrifice in performance. It seems clear that a feed mechanism working only at one edge of the jaws must be at a disadvantage relative to the uniform (gravity) feed of the standard upright configuration. In fact, gravity acting transverse to the horizontal throughflow causes a downward migration of finer material, thus encouraging early choking in the vicinity of the chain conveyor.

The rotary jaw crusher, to be described, employe a curved flow path in an attempt to both decrease the vertical dimension of the jaws themselves and provide for horizontal feed without the above problems, it achieves uniform feed distribution across the jaws, with at least a portion of this being gravitational, while avoiding transverse migration of material within the jaws. It uses no conveyor within the crushing zone (although for low headroom applications a conveyor may be used to feed the crusher.)

Figure 14a illustrates a typical jaw crusher profile in simplest schematic form neglecting curved non-choking jaw features, all of which can be provided later as necessary. After Me Grew let us assume that the included angle between jaw faces is 200, that is. a small value for hard rock. Then, for vertical jaws having a 30 inch inlet and a 6 discharge, the bare jaw height must be 69 inches. (Recall the striking uniformity of conventional machine heights noted in Section 3.)

Figure 14b illustrates a schematic of an equivalent jaw crusher in which inlet and discharge dimensions and mean path length (hence convergence angle) are preserved while wrapping the mean path around a 180 curve. For these dimensions, the curved path results in a decrease of 7 inches in height (assuming for the moment a circular mean path). While this is not an enormous saving in itself, the configuration does provide horizontal feed, and this is a substantial improvement. Other advantages will become evident as the concept is further described.

Crushing motion of the curved jaw machine may be provided by several means, the most obvious of which would be oscillation of the external jaw (the right-hand element in Figure 14b) against a stationary internal member. Jaw motion may be maximum at the discharge, in a Blake-type action, or near the inlet, in an overhead eccentric type action, depending upon the choice of the designer. However, it is believed that neither of these will provide the best design.

Figure 15 illustrates what we shall call a rotary jaw crusher having the preferred inner element crushing motion. A cylindrical inner element is driven in an orbiting motion by a central eccentric shaft, essentially identical to that of an overhead eccentric crusher. It is expected that this orbiting motion will require less force than would oscillation of the outer elements, and less force than is required by conventional jaw designs. The latter must subject their entire rock charge to crushing forces simultaneously as the jaws converge everywhere at the same time. Furthermore, with conventional gravity feed of reasonably graded material, it is virtually certain that rock fragments will in fact be tightly lodged throughout the converging crushing zone as the crushing stroke commences. In contrast, the orbiting cylinder of the rotary jaw crusher produces only a local zone of maximum convergence which travels through the rock charge. Hence, although crushing the enclosed rock charge in approximately 180 of eccentric motion (like conventional designs), it does not crush the entire charge simultaneously. The rotary jaw eccentric bearing should thus see a force that is reasonably uniformly spread through 180, rather than the conventional force which rises to a peak at the end of 180.

Orbiting motion of the inner element provides one more major advantage if the motion is in the forward direction illustrated in Figure 15. In this case, the crushing action moves through the rock charge in the flow direction providing a peristaltic pumping action to assist throughput.

With regard to throughput, disruption of the simple straight through gravity flow of conventional designs is clearly the major drawback of the rotary design. Refering to the limiting 180 design of Figure 15, gravity feed will be effective only in the middle half of the passage. Feed can no doubt be enhanced in the inlet quarter of the passage by stuffing this region with a forcing conveyor feed, but no such assistance is available in the discharge region.

With the peristaltic action described above, it is quite possible that no throughput problems will be encountered particularly if the discharge region is cut back as discussed below. However, if difficulties are encountered, it is expected that rotation of the cylindrical inner element about its own axis will be very effective in urging material through the crusher. If simple feed enhancement

is all that is desired, rotary drive via a torque source that acts when large crushing forces are absent would suffice. On the other hand, perhaps considerably more rotary torque would benefit crushing action as well, via shearing forces on the rock (like those of an overhead eccentric design). In fact, one might consider a family of designs which distribute orbiting and rotating power differently for different rocks: ranging from pure orbiting on one extreme to pure rotary (i.e., a single sledging roll crusher) on the other.

Rotation of the inner element (either freely or driven) also provides for balanced wear between the two jaw surfaces, since the full circumference of the inner element is about equal to the total length of the outer jaw. Obviously, both jaws would be provided with replaceable wear surfaces. It may also be beneficial to use different surfaces (for example ribbed or smooth), depending on the proportions of crushing and shearing desired.

Although complete rotary jaw crusher design is beyond the scope of this study. Figure 16 illustrates schematically a more complete concept. Refering back to Figure 15, clearly the greatest throughput problems will occur near the discharge, where neither gravity nor force feed are effective, and where choking would be most likely to occur in a straight (i.e., continuously converging) design in any case. Proven methods, described by McGrew, can be used to design non-choking discharge regions to ease this problem, but it may also be necessary to simply move the crusher discharge point up as shown in Figure 16 to completely eliminate the problem. Furthermore, since the complete crusher must incorporate a discharge conveyor, the higher discharge point (and correspondingly higher inlet) may not result in an overall taller machine if it allows the elevated conveyor placement illustrated in Figure 16.

The rotary jaw crusher concept has been described in schematic form and certain of its important advantages have been cited. Other advantages are also derived from the curved mean path geometry. In summary, the following features are expected to be of special advantage in portable, low head room, hard rock crushing applications:

Section 9.2 discusses the use of impact hammers, probably hydraulically actuated, to break occasional abnormally large material feeding the portable crusher. If suitable means are developed for impact breaking occasional large pieces, then it would be a logical extension of that development to attempt automated breakage of all unbeltable material particularly when the latter constitutes a reasonably small fraction of total production. Such development should follow that of the occasional oversize breaking system (particularly its automated actuation) and, although no overall concept is presented here, the idea is suggested as a goal of impact breakage systems. It would seem to promise extreme portability together with the ability to handle widely varying feed dimensions.

Obviously, an impact breaker has to be strong, but meaningful strength parameters for an impacting machine are quite different from those of a conventional machine which uses essentially static forces and brute strength. For example, an impact bit cannot be blunt, at least in the same sense as a crusher jaw, but other design features, like assuring proper orientation, can compensate for this.

In contrast to conventional machines, an impact breaker definitely should not have a limited motion, since the rock to be broken cannot be well restrained at the time of impact. Thus, the second conventional characteristic actually is not correct for this particular unconventional approach. Finally, since an impact breaker would be intended to produce major fracture in a single blow, the third conventional characteristic is also simply not appropriate in this case.

In summary, fundamental characteristics of successful conventional hard rock crushers have been noted. It is believed that these are very useful in judging the suitability of new concepts utilizing the same basic crushing means, but they are not appropriate, and should not be restrictively used, in judging concepts utilizing different crushing or breaking principles.

As concluded in Section 8, breaking of oversize feed material will be increasingly important as crusher dimensions are reduced to enhance portability. Indeed, the importance of feed size in crusher design suggests that the handling of oversize should be considered an integral part of the hard rock portable crusher development program. Hence, although impact breaker design and application in general are beyond the scope of this study, it is appropriate to discuss breaker problems and features insofar as they relate to portable crusher development. Although oversize feed may be handled at a variety of locations, that most directly related to crusher development would be immediately upstream of the crusher, and it is primarily this location that will be considered.

Ideally, the device should run without an operator, breaking all oversize material without interrupting throughput. The following are, very briefly, the major problems that can be expected in the development of such a system.

The first problem will be to identify those fragments which are oversize. Once located, each oversize fragment must be properly positioned relative to the hammer, by moving either the rock, or the hammer, or perhaps both. Preferably, if slabby material is being handled, proper positioning will also include advantageous orientation of the rock. When properly positioned, the hammer should strike the rock with enough energy to fracture the piece in a single blow. If the rock does not fracture, or if fragments are still oversize, this must be quickly determined and another blow struck. Proper support of the oversize rock at impact is important, both to promote effective energy transfer from the impacting device, and to insure that impact does not damage the supporting machinery. In view of the variability of rock size and shape, and the possibility of its motion upon impact, the impacting memeber must be capable of sustaining glancing, or even entirely missed, blows without damage.

Many of these problems are already handled to some degree by present feeder units. For example, the typical feeder that utilizes a chain flite conveyor to pull material from the bottom of a surge bin generally extracts small material first. In slabby material the larger fragments are usually well oriented, with the maximum dimension parallel to the conveyor motion, and the minimum dimension normal to the conveyor surface. Combined with suitable gates, sensing devices, and hammers, it is not unreasonable to expect that such a feeder can be equipped to automatically reduce all feed material to a size which can be handled by a portable crusher. It can also be expected that considerable development effort and operating experience will be required before untended operation of such a system becomes routine.

Handling oversize material is a very important mine problem in general, and worthy of considerable attention. The preceding example, though selected because it relates directly to portable crusher design, illustrates many of the problems that might be expected in the development of any automated impact type breaker system, whether it be applied at a draw point, over a grizzly or on a feeder conveyor, and many of the comments in the following subsection are thus of general interest.

In a complete study of handling oversize material it would not be appropriate to assume that hydraulically actuated impact devices represent the best or only breaking means. For the purpose of this crusher study, we shall limit this discussion to such devices simply because they are the most nearly suitable of todays readily available means. That is not to say, however, that a typical off the shelf hydraulic demolition tool is ideally suited to this task.

For the hard rock, portable crushers contemplated in this study, fragments having minimum dimensions of the order of 30 inches would be considered oversize. It is desireable to break such a fragment in a single blow if possible, both to minimize positioning and holding problems and to avoid throughput interruptions, and because it is more efficient. One manufacturer suggests that this requires 1000 to 3000 foot pounds per blow, obviously depending on rock properties. This same manufacturer has found that repeated blows of too little energy tend to drill holes in large fragments without causing fracture.

In view of the generally poor confinement of target fragments and likely positioning errors at the time of impact, an efficient impactor should be capable of delivering an effective blow throughout a rather long stroke perhaps as long as 12 inches. In this sense, the typical demolition hammer, although certainly the most suitable off the shelf item, is not ideal.

Depending upon overall system design, rapid automatic blow capability may not be required. Thus the rapid cyclic action of a conventional hammer may be economically omitted in favor of a simpler design that triggers discrete blows after proper hammer position is established.

These two features, very long stroke and discrete blows, suggest that it may be appropriate to reexamine the hurled bit or projectile bit (after reference 8) concept. As the name indicates, this device uses a one-piece bit-piston which is (hydraulically) hurled directly against the rock without the internal metal-to-metal impact of conventional struck bit designs. The major virtue of the hurled bit concept is the substantial reduction of peak stress within the steel for a given rock stress),which in turn, for a given blow energy, permits the use of a lighter machine at higher impact velocities. Many of the admitted design difficulties of the concept have to do with rapid sequencing, a feature that may not be required in this application. Furthermore, with proper actuator design, the hurled bit breaker is compatible with very long effective strokes.

Single blow breaking, although fast and efficient, does have one obvious drawback: the required high blow energy may cause damage to the supporting structure. Figure 17 illustrates a novel concept in which the oversize fragment is struck from below, with reaction coming solely from the inertia of the fragment itself, rather than the surrounding machinery. This figure also illustrates a simple gating arrangement which might be used to trigger the impact. Such a design might well use multiple fixed impactors triggered by multiple gates (for example, spread across the width of the feed conveyor) to avoid the complexities of moveable components. The assembly would also require means to contain fragments.

There is a need, often cited by others, for a better method of controlling oversize, independent of the existance or use of portable crushers. One grizzly-drift block cave mine is experimenting with a low profile crawler mounted impactor, capable of servicing several drifts and many drawpoints, and results to date are promising. The Maysville Operation at Dravo Lime is also using an impactor, mounted on a tractor, to service their portable jaw crushers and all the working faces.

Non room and pillar mines using mechanized (non-slusher) face haulage have a common characteristic; namely, the ability to load quite large muck and haul it to a few (relative to production sites) dump points. Grizzlies at the dump pocket represent one method of filtering out problem-causing muck, but the oversize remains, to be handled by costly secondary means. These mines may not be able to convert existing rail systems to belts and (if they existed) crusher, but they can consider automatic, untended devices at the pockets to break oversize.

A successful pocket breaker must be funded (i.e., justified) by savings derived from increased productivity (fewer disruptions), reduced secondary breakage costs, reduced ore pass and chute maintenance, reduced spillage and wear in main haulage, and, perhaps, reduced ore pass costs (size). While these effects are far

reaching, no single item predominates, none are easily estimated, and it is clear that the pocket breaker must be very simple and inexpensive. Impact breakers represent only one potential solution, and since they may not be the most satisfactory or economical, we should consider other means.

Muck at the pocket may have major dimensions exceeding six feet and minor dimensions approaching three feet. Discharge from the pocket breaker should be in the minus 20 to minus 26 inch range in order to eliminate downstream problems (and to enhance eventual conversion to low profile crushers). The tonnage requiring breakage, and the reduction ratio, are therefore quite small, indicating that the pocket breaker need not run all the time. A simple jaw, or a vise, perhaps actuated by cylinders, driven by a source of high peak (but low average! power, might be sufficiently simple. Shafts and bearings could be eliminated in favor of less expensive pivots. Servicing should be simple, and the pocket should be useable even if the breaker is not functioning, perhaps by automatically (passively) shunting aside the very large oversize.

Obviously the portable crusher must include some sort of hopper or surge bin to accommodate this highly unsteady delivery, and the hopper design must be compatible with the low head room restrictions and the dumping geometry of the load-haul-dump (or other) haul equipment within those restrictions. Present machines, both the coal feeder-breaker type in use and the horizontal jaw crushers that have been tested, are one-piece machines that feed from the hopper via a chain type conveyor. The feed conveyor also travels through, and is an integral part of, the crushing mechanism.

In soft materials like coal, potash, and trona, feeder-breakers are often self-propelled, offering the ultimate in portability. Applications in harder materials have not enjoyed this degree of portability, although size alone has not been the major problem. Rather, portability has been substantially restricted because of costly and time consuming site preparations deemed necessary in the heavy duty applications. For example, rather extensive foundation structures, requiring subgrade excavation, have been used to avoid damage caused by impact from discharging haul vehicles, and to accomodate the discharge belt. Furthermore, in a wet application any sub-grade excavation must allow additional room to accomodate drainage and clean out functions. Complications such as these make it abundantly clear that the desired hard rock portable crusher should require essentially no site preparation, or at least no site excavation.

After some thought it becomes clear from the foregoing that the desired portable crusher might better consist of a least two independent pieces: a hopper-feeder unit, and a crusher-discharge unit. The former can be virtually identical to the simple, proven hopper end of present machines. The latter, being independent of the present integral feed conveyor, cannot be identical to the present machines. Several significant advantages may be derived from this multiple piece approach:

The hopper envisioned in this discussion is a very simple device, similar to the present crushing equipment except that the feed conveyor would be inclined to accept input at the necessary low level while discharging into the top of the crusher. With gravity feed into the crusher, and either a large inlet for the latter or a simple chute arrangement between the two, the hopper feeder need not be fastened to, or even precisely located, relative to the crusher. This would permit easy set-up and it may provide for much simpler protection against impacts from haul vehicles. For example. Figure 18 illustrates schematically a set-up having the following features:

Actual layout of the equipment is, of course, dependent upon a variety of mining conditions. The sketch is intended to suggest one possiblity, and to illustrate the flexibility inherent in a two-piece design.

Modular assemblies, which offer interesting advantages in this simple two-piece concept, are virtually a necessity if additional crusher features are to be provided. For example, if oversize feed is to be broken on the feed conveyor, as discussed in

a preceding section, it is unlikely that a one piece hopper-feeder-breaker-crusher design will be either portable or maintainable. Furthermore, it has been suggested that feed scalping be employed to avoid additional crushing of already beltable material. Suitable equipment for this feature is well within the present state of the art, and development of a one-piece integrated unit is not only not necessary: it may well be undesirable.

In view of the conclusions reached in this Applications Study, presented in Section 8, and reviews of present equipment together with new concepts presented in Section 9, three recommendations are made for further design, development, and testing of a portable hard rock crusher.

It is recommended that a program be initiated to develop a hard rock, low head room, portable crusher of the rotary jaw crusher type. It is believed that this concept is the simplest available based on proven hard rock crushing principles, and therefore, it is the best concept for full development.

Although the machine should ultimately be designed within those parameters cited in Section 8, early experimental work can profitably be done on a smaller prototype of perhaps 20-inch critical inlet dimension. The purpose of this experimental phase of the development would be to establish (above ground) proper jaw shape, eccentric motion, and rotary motion to assure proper feed. Once this is assured, full scale underground prototype development could be undertaken with confidence.

It has been concluded that feed scalping to avoid unnecessary crushing of beltable material would enhance the performance and capacity of any portable crusher. It is not believed that provision of this feature will require an elaborate development program: therefore, initiation of such a program at this time is not recommended, However, when a full scale prototype crusher design is undertaken, it is recommended that feed requirements be defined in suitable terms to permit procurement of a suitable feed system for use in early field tests.

It is recommended that a program be undertaken, in parallel with crusher development, for the development of suitable means for breaking oversize feed material. This program can be divided into three major subprograms and, in view of the widespread occurance of the problem (it has been cited by others), and the variety of possible applications, it is recommended that all three sub-programs be undertaken simultaneously. They are:

a fundamental model of an industrial-scale jaw crusher - sciencedirect

a fundamental model of an industrial-scale jaw crusher - sciencedirect

In this study, an analytical perspective is used to develop a fundamental model of a jaw crusher. Previously, jaw crushers were modelled in regard to certain aspects, for example, energy consumption (Legendre and Zevenhoven, 2014) or kinematics (Oduori et al., 2015). Approaches to date have been mainly property specific. In this work a physical modelling approach has been used to derive the modules, which are based on established facts of comminution machines, from the literature. A modelling methodology mainly inspired by Evertsson has been applied (Evertsson, 2000). The modules are divided into kinematics, flow, breakage, capacity, pressure and power. Each module has been derived and tested decoupled from the other modules to provide increased transparency of the module and its behaviour. The results of the modelling are presented for a baseline case of one industrial-scale jaw crusher and compared to manufacturer data. Future work will include validation and DEM simulations.

on oscillations of a vibratory jaw crusher with asymmetric interaction of the jaws with the processed medium | jve journals

on oscillations of a vibratory jaw crusher with asymmetric interaction of the jaws with the processed medium | jve journals

Vibroengineering PROCEDIA, Vol. 25, 2019, p. 83-88. https://doi.org/10.21595/vp.2019.20831 Received 26 May 2019; accepted 5 June 2019; published 25 June 2019

Panovko Grigory, Shokhin Alexander, Lyan Ilya On oscillations of a vibratory jaw crusher with asymmetric interaction of the jaws with the processed medium. Vibroengineering PROCEDIA, Vol. 25, 2019, p. 83-88. https://doi.org/10.21595/vp.2019.20831

This paper is devoted to the problem of providing the required synchronous modes of oscillations of a jaw crusher with self-synchronizing inertial vibration exciters. The described mathematical model of the crusher takes into account the mechanical properties of the medium being processed and the possible asymmetry of its contact with the crushers working bodies the jaws. A numerical analysis of synchronous modes of crusher vibrations with different asymmetries of the initial location of the processed medium relative to the jaws is done. It is shown that for given oscillation excitation frequencies, the non-simultaneous contact of the processed medium with the jaws can lead to a change in the types of synchronous vibrations of the jaw crusher.

One of the problems of creating efficient vibratory jaw crushers with two movable jaws, which oscillations are excited by self-synchronizing inertial vibration exciters, is the provision of synchronous jaws antiphase oscillations [1-3]. The type of synchronization of the exciters rotation and the jaws oscillation forms have a mutual influence on each other and are determined by the mechanical parameters of the system, the processed mediums characteristics, the electric drives parameters of vibration exciters and their rotation frequency [3, 4]. When studying the dynamics of such crushers, it is especially difficult to take into account the interaction of the jaws with the medium being processed [2, 5, 6]. In mathematical models used in common computational practice, this interaction is usually taken into account in the form of viscous friction forces [5, 7, 8]. At the same time, factors excluded from consideration, such as non-simultaneous contact of the jaws with the processed medium, its elastic properties, as well as the vibro-impact nature of its interaction with the crushers jaws, can have a significant influence on the systems dynamics.

This paper is devoted to identifying the effect of non-simultaneous interaction of jaws with the processed medium, taking into account their impact contact, on the exciters self-synchronization and jaws movement.

The solution of the problem is based on the analysis of the vibrating jaw crushers dynamics with two movable jaws that perform straight horizontal oscillations excited by two inertial vibration exciters installed on each of the jaws. The design scheme of such a crusher is shown in Fig. 1. The crushers body is modeled by a solid body of mass m1, elastically attached to a fixed base. The jaws are modeled by identical solids with mass m2. The jaws are attached to the crushers body with the identical elastic elements. It is assumed that all elastic elements have linear stiffness and damping characteristics with coefficients c0, c1 and b0, b1, respectively. On each of the jaws the same unbalance vibration exciter is fixed, driven by an asynchronous motor of limited power whereas me and r each vibration exciters imbalanced mass and eccentricity, J adduced moment of inertia of the vibration exciters asynchronous motor, Lj torque of the jth vibration exciters electric motor (j= 1, 2) described by the static characteristic [9]. The friction in the bearings of the unbalance shafts is taken into account in the form of the moments Rj of dry frictions forces (not shown in Fig. 1).

Between the jaws there is a processed medium modeled by a solid body m3 with two (one on the left and one on the right) identical elastic elements, with stiffness and viscosity coefficients c2 and b2, respectively, providing one-way interaction with each of the jaws. In addition, the body m3 is attached to a fixed base by a linear elastic element with stiffness and viscosity coefficients c3 and b3, respectively, which ensures that the modeled medium returns to its initial position only when there is no contact with the jaws. In this way, the inflow of a new unprocessed part of the medium through the crushers fixed loading window into the working space between the jaws is simulated. In the initial state, the working bodies can be installed with a gap (pre-tension) relative to the contact elements, which is given by the values 1 and 2.

Displacements of the bodies are described by coordinates xi (i= 1, 2, 3, 4) of their centers of mass, measured from their equilibrium position. The positions of the debalances are described by the angles of rotation j (j= 1, 2), measured from the negative direction of the axis Ox.

n = m n / m 2 ( n = 1,3 ) , e=me/m2, 0=c0/c1, 2=c2/c1, 3=c3/c1, 2=b2T*/m2, 0=b0/b1, 2=b2/b1, 3=b3/b1, yi=xi/X* dimensionless coordinates, X*=r0, r0 given eccentricity initial value, T*=m2/c1 time scale:

where Mc and sc critical torque and slip of the asynchronous motor, j=1 denotes direction of the motors rotation, sj=(j0-j)/j0, 0=e/p synchronous speed of rotation of the electric motor, e frequency of the supply voltage, p number of pole-pairs of the electric motor, R~j=fj2sign(j), f coefficient of dry friction, dots indicate differentiation by dimensionless time =t/T*. The presented equations system allows to analyze the crushers motion, taking into account the non-simultaneous impact of the jaws on the processed medium and their impact contact.

The system oscillations were simulated numerically in Matlab using standard functions for integrating differential equations with the condition to accurately determine the time of the beginning and the end of the jaws contact with the processed medium.

At the first stage, the frequency ranges of synchronous exciters rotation and jaws motion were determined in the absence of the processed medium (the standard task of studying the frequency ranges of the exciters synchronous rotation and the crushers vibration modes with the aim of selecting its operating modes). For this, the frequency of the supply voltage e was set, which discretely increased in the range of 0.1 e 2.5 with a step e= 0.5 and an exposure at each step during = 400 sufficient to achieve steady-state oscillations of the system (the law of change e is shown in Fig. 2). In this case, in the considered frequency range e, the maximum torque of the engine was considered to be a constant value. The calculations were carried out with the following system parameters: 1= 2, 3= 0.05, = 0.03, 01= 0.1, 14=1, 30= 0.5, 0= 1, 2= 10, 3= 1, Mc= 100, sc= 0.2, f= 0.001, d= 0.61, L*=0.005, 1=-1, 2=1.

In Fig. 3 and Fig. 4 the results of calculating the rotational velocity of the inertial exciters j and the mutual phase shift of the rotation between the exciters as a function of time are shown, respectively. The value of = 180 corresponds to the synchronous antiphase rotation of the exciters debalances, which causes the antiphase oscillations of its jaws required for the crushers normal operation. When = 0, the debalances rotate in phase, exciting the common-mode oscillations of the crushers jaws. One can see from Fig. 2 and Fig. 4 that the required synchronous modes of the debalances rotation and, accordingly, oscillations of the crusher are realized in the ranges of supply voltage frequencies e[0.8, 1.2] and e[1.85,2.5]. Fig. 2 and Fig. 3 show the relationship between the power supply frequency and the rotational velocities of the debalances. It also can be seen that in the indicated ranges of the supply voltage frequency, the debalances rotate with the same angular velocity in absolute value. When approaching the second and third resonant frequencies (2*= 0.976, 3*= 1.445), the rate of change of an average rotational velocity of the debalances decreases at the same rate of change in the power supply frequency (Fig. 3). The passage through the resonance is accompanied by a jump in the rotational velocity of the debalances, as well as a change in the type of their synchronous rotation and the jaws oscillation form. These effects are associated with a slip in asynchronous motors and the interaction of the oscillating system with vibration exciters.

To analyze the possible influence of non-simultaneous contact of the jaws with the processed medium on the exciters synchronization and the jaws vibrations, the crushers oscillations were simulated with a gradual change in the initial gap ~1 between the left jaw and the corresponding contact element of the processed medium for a given value of power supply frequency. The gap varied in the range of 0.1 ~1 0.4 with a step ~1= 0.1 and an exposure at each step for =400 (the law of change of the gap ~1 is shown in Fig. 5). At the same time, the initial gap between the right jaw and the right contact element of the medium did not change and, to ensure the initial contact symmetry, it was assumed to be ~2= 0.1. The study was carried out for different frequencies of the supply voltage in the range of e[1.85, 2.5], in which a exciters synchronous antiphase rotation occurs (after the third resonance). The frequency range e[0.8,1.2] between the first and second resonances was not considered, because at these frequencies the developed forces are usually not sufficient to destroy the material, and therefore it is not used in common practice.

In Fig. 6-9 graphs of the change in the mutual phase shift of between the debalances obtained at supply voltage frequencies e={1.85, 2.0, 2.2, 2.4} are presented. It can be seen that at frequencies e={1.85, 2.0} (see Fig. 6 and Fig. 7), the exciters synchronization is broken when the gap ~1= 0.4 is reached. In this case, the mutual phase shift between the debalances does not stabilize with time. In turn, this leads to a violation of the required oscillation synchronous antiphase mode of the crushers jaws. When e= 2.2 (see Fig. 8), a synchronization violation occurs when ~1= 0.3. When e= 2.4 (see Fig. 9), synchronization is violated when ~1= 0, while the mode of antiphase oscillations of the crushers jaws is maintained up to ~1=0.2 (i.e., up to = 1200). Thus, with an increase in the excitation frequency, a decrease in the contact asymmetry of the processed medium with the crushers jaws is observed, at which a violation of the required exciters synchronization and, accordingly, oscillations of the jaws occurs.

The simulation results presented in this paper clearly demonstrate the possibility of violation of the debalances synchronous rotation and, accordingly, oscillations of the crushers jaws when the contact interaction conditions with the processed medium are changed due to jaws non-simultaneous contact with the processed medium. It is shown that with an increase in the excitation frequency, a decrease in the contact asymmetry of the processed medium with the crushers jaws is observed, at which a violation of the required synchronous rotation of the unbalances and, accordingly, oscillations of the jaws occur. Such changes in the contact interaction conditions can occur directly during the crushers operation, and they must be taken into account when assigning its operating modes.

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