GB2056880A

GB2056880A - Comminuting apparatus

Info

Publication number: GB2056880A
Application number: GB8027031A
Authority: GB
Original assignee: MEYER AG J
Current assignee: MEYER AG J
Priority date: 1979-08-27
Filing date: 1980-08-19
Publication date: 1981-03-25
Also published as: FR2464096B3; DE3009106A1; DE3009106C2; CH640752A5; IT1132454B; FR2464096A1; IT8024251A0

Abstract

The roller 1, 2 of a roller crusher are driven by respective hydrostatic drives 12, 13, 14; 22, 23, 24. When a lump of rock causes jamming, control means 6 controlled by the oil pressure, causes the reversal of the rollers for a predetermined time and then reintroduces forward rotation of the rollers. Between the forward and reverse rotations there may be a stoppage for a predetermined period during which maximum operating pressure is maintained so as to give the rollers a longer opportunity to crush the lump of rock which is causing jamming. Thus the machine may be protected from damage and its productivity may be increased in the absence of any breakdown. Cleaning combs (7 Fig. 3 not shown) and lateral cleaning openings 8 may be provided. To prevent an output funnel 9 from clogging it may be constructed as a vibrating conveyor. <IMAGE>

Description

SPECIFICATION A roller crusher and a method for its operation The invention relates to a roller crusher particularly for claystone and a method for its operation.

Roller crushers are usually driven by mechanical gearings which transmit the drive movement originating from a motor to the rollers. Hydrocouplings are also used in many cases and serve to overcome the mass inertia when starting up. These hydrocouplings are in fact ascribed a certain protective action when very high forces arise on the crusher teeth.

However, these hydrocouplings are not usually able to fulfill the hopes placed on them because the vibration effect prevents this.

Therefore, couplings are regularly used with shearing bolts as a protective device. In the case of claystone containing large amounts of rock however, overloading occurs repeatedly and relatively frequently and this overloading results in the bolts shearing off so that the crusher has to be brought to a standstill.

Therefore, the operating personnel often incorporate fairly strong shearing bolts and this eventually destroys the gearings and the shafts.

In general, it may be said that the known roller crushers clog relatively rapidly with claystone, more particularly if crushing takes place at the quarry or in the mine and if relatively thin and slurry-like rock is supplied to the crusher as may be the case in winter and when the weather is poor. However, it is just this crushing in the mine or in the quarry which provides the advantage whereby it is possible to pre-mix rock and store it in the meantime for ageing without the problems involved when crushing in the processing operation.

The object underlying the invention is to overcome the existing problems and to create a roller crusher with which claystone may be crushed cleanly and without any large interruptions in operation.

According to a first aspect of the present invention there is provided a roller crusher having contra-rotating crushing rollers driven by reversible hydrostatic drive means, wherein automatic means are provided for temporarily reversing the direction of rotation of the rollers and reintroducing the former direction of rotation of the rollers after a predetermined period of reverse rotation has expired.

The actuating means is preferably actuated by means serving a predetermined maximum pressure of the hydrostatic drive means. Timing means are preferably provided for determining a delay during said maximum pressure is maintained and the rollers remain substantially stationary, before the reverse rotation occurs.

The crusher rollers may have crusher teeth which are generally sawtooth shaped, the front edges of the teeth may be formed as wedge-shaped blades.

Clogging of the roller crusher may be reduced by providing the cleaning combs only in the upper region. If, nevertheless, natural clogging occurs, then it may be eliminated by the provision of the lateral and upper cleaning openings. Clogging itself may be avoided almost completely in the case of very unfavourable operating conditions if an outlet funnel or hopper constructed like a vibrating conveyor is provided.

According to a second aspect of the present invention there is provided a method of operating a roller crusher having contra-rotating crushing rollers driven by reversible hydrostatic drive means wherein when at least one of the roller drives reaches a predetermined maximum pressure of its drive fluid the roller drives are stopped and reverse movement of the rollers is introduced automatically for a predetermined period and then advance of the rollers is resumed automatically again.

In a preferred method the maximum pressure of the roller drive is maintained for a predetermined period before the reversal movement is introduced.

A preferred embodiment of a roller crusher in accordance with the present invention will now be described with reference to the accompanying drawings, of which, Figure 1 shows a side view of a roller crusher in accordance with the invention with part of the side cladding and part of the drive motor removed; Figure 2 shows a plan view of this roller crusher with part of the inlet funnel omitted; and Figure 3 shows a section which is enlarged as compared to Fig. 1 in a plane vertical to the crusher rollers.

The roller crusher shown in the drawings has two crushing rollers 1, 2 in parallel with each other and provided in each case with crushing teeth 10, 20. These crushing teeth 10, 20 mesh in passing as the crushing rollers 1, 2 rotate while they overlap in the view according to Fig. 3.

The crushing teeth 10, 20 each have a steep and blade-like front edge 101, 201, a gradually inclined rear edge 102, 202 and between these a relatively long top edge 103, 203 which runs in a substantially peripheral direction. During normal forward drive in the direction of the arrows shown in Fig. 3, the front edges 101, 201 of the crushing teeth 10, 20 meet at the stone which is to be crushed. During reverse movement, jammed lumps or fragments of stone and other material are raised by the inclined rear edges 102, 202 and moved. The long edges 103, 203 assist the teeth considerably in terms of service life even if it is not sure why this is.

In the region of the crushing teeth 10, 20 the shafts 11, 21 of the crushing rollers 1, 2 are polyfonal, ensuring safe positive connection of the crushing teeth 10, 20, these teeth being formed on disc or plate members, with the shaft. These shafts 11, 1 2 are pivotally mounted in the support 3 of the roller crusher and are under the direct action of hydromotors 12, 22. The latter are supplied with pressure oil through pipes 13, 23 from pumps 14, 24. The pumps 14, 24 are in turn driven by a gearing 4 of the diesel engine 5.

The latter may be replaced by some other engine or motor.

Pressure control means indicated by box 6 is provided in the pipes 13, 23 or on the pumps 12, 22 and/or on the hydromotors 11, 21. This pressure control means encompasses an overpressure valve which limits the pressure absolutely and thus prevents any overloading. Furthermore, a pressure switch is present which stops the drive when a maximum operating pressure of the oil is reached.

In preferred manner, this maximum operating pressure is maintained while stationary for a time of a few seconds, so that any late effect could still break a lump jammed in the device.

Only after this waiting period which may be selected by means of a timing element has expired is the reversal of the rollers introduced by the activated changeover means. This reversal lasts a few seconds, depending on a timing element and afterwards forward rotation of the rollers is started again automatically.

Since the hydromotors act directly on the crushing rollers, the mass which is to be stopped is almost zero because the rollers are made stationary by the "jammed" lumps, while the monitoring of the oil pressure by the control means allows momentary interruption of the drive action. The diesel engine and the pumps may continue to operate or may be stopped. Their mass no longer has any effect.

In order to prevent the roller crusher from becoming clogged, only upper cleaning combs 7 (Fig. 3) are provided. If clogging still occurs despite the outlet funnel or hopper 9 being formed as a vibrating conveyor, cleaning may be carried out easily via the lateral openings 8.

A conveyor belt 90 transports the crushed material away.

In roller crushers it is known to drive the two rollers at revolution speeds of less than 50 rotations per minute and to drive them at different revolution speeds. This basic principle may be used successfully in roller crushers according to the present invention. A roller speed of 3 or 25 rotations/min for example for one or other of the rollers has proved advantageous.

In the hydrostatic drive of the rollers, there is on the one hand an overpressure valve limiting the pressure adsolutely and on the other hand there is a switch controlled by the pressure which stops advance of the rollers as soon as a predetermined maximum operating pressure is achieved. In contrast to the con ventional drives, the hydrostatic drive may act directly on each roller so that an instantane ous effect occurs in the described pressure limitation. Therefore, overloading is not a dan ger.

Automatic changeover means, preferable af ter a certain period of time which the maxi mum pressure is maintained while stationary, introduce a reversing movement of the rollers which reversal is maintained for several sec onds and in any case several rotations of the rollers until normal operation is resumed again automatically. If "jamming" occurs, this proc ess may be repeated several times.

The lumps or fragments which cause "Jamming" are not only released but may also be brought into a different position dur ing reversal.

The fact that the maximum pressure is maintained momentarily before reversal while the the crusher is stationary does in fact success- fully prevent the overloading known in other crushers. Moreover it does not release the "Jammed" lumps as rapidly as in conven tional crushers so that the pressure continues to have an effect and has an opportunity to crush a lump or fragment which would with stand the same pressure in the case of a short term effect.

A device in accordance with the invention and its method of operation may effectively eliminate completely the interruptions of oper ation which are feared and which are due to overloading, so that they have a much greater useful effect.

The above described arrangement of the crusher teeth is favourable to this effect and the tooth blades favour the effect and service life of the teeth and other crusher members.

Claims

1. A roller crusher having contra-rotating crushing rollers driven by reversible hydro static drive means, wherein automatic means are provided for temporarily reversing the dii rection of rotation of the rollers and reintro ducing the former direction of rotation of the rollers after a predetermined period of reverse rotation has expired.

2. A roller crusher according to Claim 1 wherein the automatic means is actuated by means serving a predetermined maximum pressure of the hydrostatic drive means.

3. A roller crusher according to claim 2 and comprising a timing element for determin ing a delay, during which said maximum pressure is maintained and the rollers remain substantially stationary, before the reverse ro tation occurs.

4. A roller crusher according to any pre ceding claim wherein drive force limiting means is provided for limiting the pressure of the hydrostatic drive means.

5. A roller crusher according to Claims 1 to 4 wherein said automatic means, said pressure-sensing means, said timing element and said drive-force limiting means are constituted by a single device.

6. A roller crusher according to any preceding claim wherein each crushing roller has a respective directly-acting hydraulic drive mechanism.

7. A roller crusher according to any preceding claim wherein the crushing rollers have crusher teeth.

8. A roller crusher according to Claim 7 wherein the crusher teeth are saw-tooth shaped, each having a top edge which extends substantially peripherally between a steep front edge and a gradually inclined rear edge.

9. A roller crusher according to claim 7 or 8 wherein each of the crusher teeth has a front edge formed as a wedge-shaped blade.

1 0. A roller crusher according to any preceding claim and having upper cleaning combs.

11. A roller crusher according to Claim 10 and having lateral cleaning openings beneath the cleaning combs.

1 2. A roller crusher according to any preceding Claim and having an outlet funnel which is formed as a vibrating conveyor.

1 3. A roller crusher substantially as herein described with reference to the accompanying drawings.

1 4. A method of crushing claystone, employing a roller crusher according to any preceding claim.

1 5. A method of operating a roller crusher having contra-rotating crushing rollers driven by reversible hydrostatic drive means wherein when at least one of the roller drive reaches a predetermined maximum pressure of its drive fluid the roller drives are stopped and reverse movement of the rollers is introduced automatically for a predetermined period and then advance of the rollers is resumed automatically again.

1 6. A method according to claim 1 3 wherein the maximum pressure of the roller drive is maintained for a predetermined period before the reversal movement is introduced.

1 7. A method of operating a roller crusher substantially as herein described with reference to the accompanying drawings.

1 8. A method of crushing claystone according to any of Claims 1 5 to 1 7.