GB2118689A - Improvements in hydraulic control devices for use with mining apparatus - Google Patents

Abstract

A compact hydraulic control device for use with mining apparatus is composed of a block 2 containing tappet-operated valves 3. A multi-part cam shaft 6, 7 serves to selectively operate the valves by displacing the tappets 5 through cams 8, 9 and by manual control. To automatically restore at least part of the cam shaft 6, 7 to its neutral position as a 'dead man's' restoring system use is made of a piston member 11 which is subjected to hydraulic force to act on a cam 9 of the cam shaft part 7. <IMAGE>

Description

SPECIFICATION Improvements in hydraulic control devices for use with mining apparatus The present invention relates to hydraulic control devices particularly, but not solely, for use with mining apparatus such as roof supports.

In mineral mining it is known to provide a number of control valves in a common block and to actuate the valves selectively with tappets by partly-rotating part of a composite cam shaft with the aid of a manual lever outside the block. On release of the lever the cam shaft part is automatically restored to a neutral non-operative position by a 'dead-man's handle' type restoration system. UK patent 2 037 858 describes a known device.

In this known device the restoration system is in the form of a pair of spring-loaded push rods engaging on a special cam of the multi-part cam shaft. Since each relatively rotatable part of the cam shaft needs a special cam and a pair of pushrods the device is relatively complex and costly and there is a need for a simpler arrangement.

A general object of the present invention is to provide an improved form of control device.

In contrast to the device described in the aforementioned UK patent 2 037 858, the restoration system of the present invention essentially comprises a hydraulically-operated piston member which engages on a cam which is preferably used to actuate one of the tappetoperated control valves.

According to the invention a hydraulic control device comprises a housing, a plurality of individual control valves operated by tappets, manually-operable rotatable cam shaft means for displacing the tappets to operate the valves and an automatic restoration system for acting on the cam shaft means to restore at least part of the cam shaft means back into a neutral position when manually-reieased; wherein said restoration system includes a piston member guided for movement in the housing to engage on a cam of the cam shaft means and means for exposing the piston member to hydraulic pressure fluid to cause the piston member to act on said cam and perform said restoration. The piston member can be relatively small and sealed for sliding in a bore radial to the cam shaft means.The cam on which the piston member engages, preferably by way of a frusto-conical end region, can also serve to actuate one or more tappets associated with the control valves. This cam may have a cam surface shaped so that the piston member exerts a restoration force thereon which is at a maximum when the part of the cam shaft means carrying the cam has been manually partly-rotated from the neutral position to maximum extent commensurate with operation of said at least one tappet-operated valve. The part-rotation of the cam shaft means part between the neutral and control-valve-operating positions is typically through an angle of 450 or thereabouts. This normal movement should not include any dead centre position where the restoration force is zero.

The piston member can be provided with a stem or the like which serves to actuate a simple ball-valve to expose the piston member to pressure fluid only when the piston member is itself displaced by the associated cam when the cam shaft means part is moved to operate one or more of the control valves. As is known from UK patent 2 037 858, the cam shaft means can be composed of a number of parts each independently rotatable with the aid of a hand lever and provided with several cams to actuate the tappets of a series of valves in sequence. In the case of this arrangement each such part would have its own hydraulically-operated piston member for restoration as described. The hydraulic fluid for acting on the piston member can be supplied to a stepped bore containing the ball valve and stem and coaxial with the bore containing the piston member.A source of pressure fluid can be connected in common to the ball valve, held closed by a spring when the cam shaft means part is on its neutral position, and to the individual control valves. Conveniently, in a mining installation a main pressure fluid feed line can supply the pressure fluid.

The invention may be understood more readily, and various other features of the invention may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing wherein: Figure 1 is a sectional side view of a hydraulic control device made in accordance with the invention; and Figure 2 depicts part of the device shown in Figure 1 on a somewhat larger scale.

The hydraulic control device shown in the drawing and generally designated 1 is similar to that described in UK patent 2 037 858.

As shown in the drawing, the device has a main block or housing 2 in which are disposed a plurality of borings and individual control valves 3 located in stepped bores 4. The valves 3 are constructed as cartridges which form easily replaceable and interchangeable units screwed or otherwise fitted in the block 2. The valves 3 are actuated by means of tappets 5 which are displaced by means of multi-part cam shaft means rotatably mounted in the housing 2. The cam shaft mean inciudes a central spindle 6 surrounded by a coaxial sleeve 7. Manually-operated levers (not shown) accessible externally of the housing 2 serve to partially rotate the spindle 6 and/or the sleeve 7.

The sleeve 7 and the spindle 6 are provided with cams which serve to actuate the individual tappets 5 associated with the valves 3 and groups of valves 3. Figure 1 partly depicts just two such cams 8, 9 fitted to the sleeve 7. The cam 8 controls the tappet 5 of the valve 3 illustrated therebeneath, while the cam 9 controls another valve 3 (not shown) arranged in alignment with the illustrative valve 3. Figure 1 shows the cam 8 moved into a position in which the valve 3 has been operated by means of its tappet 5 engaging on the cam surface 10. In this position, the valve 3 is opened to permit the passage of hydraulic pressure fluid through the valve 3. To reach this position, the cam 8 and the lever at the end of the sleeve 7 have been moved through an angle of about 450 in relation to a neutral position in which the valve 3 is closed.It is preferable to provide a positive lock to hold the sleeve 7 and parts rotatable therewith in its neutral position. This can be achieved with the aid of a spring-loaded detent 22 which inter-engages with one of the respective cams 8, 9. As shown the cam 9 has a groove or notch 23 in its surface which engages with the spring-loaded detent 22.

In order to restore automatically the cam 8 and the sleeve 7 to the neutral position on release of the lever mounted to the sleeve, a biasing or 'dead-man's handle' restoring system is provided.

This system includes a piston member 11 which is slidably guided in a bore 12 in the block 2 extended radially to the sleeve 7. The piston 11 is provided with a seal 13 slidably engaging with the surface of the bore 1 2 and a frusto-conical end part 20. The piston 11 has a stem 14 which extends within a stepped bore 1 5 forming an outer continuation ef the bore 12. A valve 1 6 is located in the bore 15. The valve 16 is in the form of a spring-loaded non-return valve with a closure element or ball 17 urged on a seating 19 by the action of a compression spring 18.

The valve 16 is also constructed as cartridge screwed or otherwise fixed into the boring 12, 1 5 in the block 2. The boring 15 is in communication with a further bore (not shown) leading to a source of pressure-fluid. If the sleeve 7 occupies it neutral position the valve 16 is held close by virtue of the spring 1 8 and consequently the piston 11 is not subjected to hydraulic pressure. As shown in Figure 2, the cam 8 has a cam surface 10, 10' designed to displace both the tappet 5 and the piston 11 when the sleeve 7 is partially rotated by operation of its lever.If the sleeve 7 is pivoted by means of its lever from the neutral position to the control position in which the valve 3 in question is operated by means of its tappet 5 then the piston 11 is displaced by means of the cam 8 engaging on the shaped end part 20 of the piston 11. The displacement of the piston 11 causes the stem 14 to lift the ball 1 7 off the seating 19 against the force of the spring 1 8. The valve 16 consequently opens and the piston 11 is subjected to hydraulic pressure fluid on its face adjacent the bore 1 5 which supplements the force of the spring 1 8. On release of the lever, the piston 11 subjected to pressure fluid and the force of the spring 1 8 is designed to act on the cam surface 10 to pivot the sleeve 7 back into the neutral position.When the sleeve 7 re-adopts the neutral position the piston 11 will have moved to the left of Figure 1 to an extent sufficient to allow the valve 16 to close again. Figure 2 in fact shows the cam 8 in the position in which the valve 3 has been operated after the sleeve 7 has been moved through an angle of 450 from the neutral position. In this operating position, the end part 20 of the piston 11 engages on a convex portion 10' of the cam surface 10 whereby the cam 8 is itself subjected to a restoring moment by virtue of the radial force on the piston 11. The cam surface 10 is shaped so that the restoring moment provided by the piston 11 is at a maximum when the lever used to move the sleeve 7 has been pivoted to its outermost operating position, i.e. when the valve 3 has changed state.In addition during the part-rotation of the sleeve 7 between the neutral and operating positions no dead centre position in which the restoring moment is zero can prevail. A dead centre position is present however as shown in Figure 2 at 21 but this is located at an angle X in the region 1 20 beyond the control position where the valve 3 is fully operated.

As in the described arrangement US patent specification 4310027 where there are a number of valves or pairs of valves controlled by separate cams on its own independently rotatable part of the cam shaft means, one cam of each set of cams would be associated with its own hydraulicallyoperated restoration piston 11 to bring about the automatic restoration of the appropriate section of the cam shaft means to the neutral position and the detent 22 can be provided for each such section.

The device as shown and described can be used with various hydraulic mineral mining appliances, such as roof supports, and the valve 1 6 can be connected to the main pressure-fluid feed line which is also connected to the individual control valves 3.

Claims (11)

1. A hydraulic control device comprising a housing, a plurality of individual control valves operated by tappets, manually-operable rotatable cam shaft means for displacing the tappets to operate the valves and an automatic restoration sytem for acting on the cam shaft means to restore at least part of the cam shaft means back into a neutral position when manually-released; wherein said restoration system inciudes a piston member guided for movement in the housing to engage on a cam of the camshaft means and means for exposing the piston member to hydraulic pressure fluid to cause the piston member to act on said cam and perform said restoration.

2. A device according to claim 1, wherein the piston member is slidably and sealably guided for displacement in a bore extending radially to the cam shaft means.

3. A device according to claim 1 or 2, wherein the piston member has a frusto-conical end part for engaging with a cam surface of said cam.

4. A device according to claim 1,2 or 3, wherein the piston member is provided with a stem which is displaced to actuate another valve when the cam shaft means part is partly rotated manually at least one of the tappet-operated control valves, said stem and said other valve constituting at least in part said means for exposing the piston member to hydraulic fluid.

5. A device according to claim 4, wherein the other valve has a spring-loaded ball of which is displaced off a seating by displacement of the stem of the piston member when the piston member is itself displaced by said cam.

6. A device according to claim 5, wherein said other valve is mounted in a stepped bore coaxial with the bore containing the piston member and the stepped bore is connected to a source of pressure fluid which is also connected to the tappet-operated valves.

7. A device according to any one of claims 1 to 6, wherein the cam shaft means is composed of relatively-rotatable parts each being independently manually-controlled with its own hand lever and having a plurality of cams for actuating several tappet-operated valves and wherein each part has its own automatic restoration system comprising said hydraulicallyoperated piston member.

8. A device according to any one of claims 1 to 7 and further comprising a spring-loaded detent device for locking said at least part of the cam shaft mean in its neutral position.

9. A device according to any one of claims 1 to 8, wherein the cam engaged by the piston member also actuates at least one of the tappetoperated valves.

10. A device according to claim 9, wherein the cam has a cam surface shaped so that the piston member exerts a restoration force thereon which is at a maximum when the part of the cam shaft means carrying the cam has been manually partly rotated from the neutral position to maximum extent commensurate with operation of said at least one tappet-operated valve.

11. A coritrol device substantially as described with reference to, and as illustrated in the accompanying drawing.