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 the aid of tappets by partially rotating a part of a composite cam shaft with the aid of a manual lever accessible from 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 of restoration system.

#U.S. Pat. No. 4,310,027 issued Jan. 12, 1982 and assigned to the same assignee as this application, describes a known device and this patent is herein incorporated by a reference. U.S. patent application Ser. No. 485,243 filed Apr. 15, 1983 and also assigned to the same assignee as the present application also describes another form of device related to the present invention.

#An embodiment of the invention will now be described, by way of example only, reference to the accompanying drawings, wherein:

#FIG. 1 is a sectional side view of a hydraulic control device constructed in accordance with the invention;

#FIG. 2 is a sectional end view of the device shown in FIG. 1; and

#The hydraulic control device shown in the accompanying drawings and generally designated 1 is similar in many respects to that described in U.S. Pat. No. 4,310,027. As shown in the drawings, the device has a main block or housing 2 in which are disposed a plurality of borings and individual control valves 3 located in adaptive stepped bores 4. The valves 3 are constructed as cartridges which form easily replaceable and interchangeable units screwed or otherwise fitted into the block 2. The valves 3 are actuated by means of tappets 5 conveniently forming parts of the cartridges and which are displaced by multi-part cam shaft means rotatably mounted in the housing or block 2. The cam shaft means includes a central spindle 6 surrounded by coaxial sleeves 7, 8. The spindle 6 and the sleeves 7, 8 project outwardly from one end of the block 2 and manually-operable levers 9, 10 and 11 are mounted to the components 6, 7 and 8, respectively, in order to permit partial rotation of the spindle 6 and/or the sleeves 7, 8 about their common rotational axis. The sleeves 7, 8 and the spindle 6 are provided with cams 12 each of which serves to actuate the individual tappets 5 associated with one of the valves 3 or a group of valves 3. In order to restore automatically the spindle 6 and the sleeves 7, 8 into a neutral position, a biasing, or "dead-man's handle" restoring system is provided. As represented in FIGS. 2 and 3 this system is composed of piston and cylinder assemblies mounted in the block 2, again as easily replaceable cartridges fitted into bores thereof. The spindle 6 and the sleeves 7, 8 are provided with additional cams 13 of which is subjected to the action of a pair of the piston and cylinder assemblies arranged parallel to one another. FIG. 2 depicts the assemblies pertaining to the cam 13 of the spindle 6 and one of the assemblies is shown on a somewhat larger scale in FIG. 3.

#Each piston and cylinder assembly has a piston 14 slidably guided within a cylinder 15 and the piston rod 16 which leads from one end of the cylinder 15 through a seal as shown. The piston rod 16 carries a push rod 17 conveniently connected thereto as a push-on or snap-fit connection 18. At the end of the cylinder 15 remote from the piston rod 16 there is a closure in the form of a threaded end piece 19 which is engaged within a threaded bore within an end region of the cylinder 15. This end region also has an external screw thread 20 which enables the entire assembly to the detachably engaged with a similar screw-thread within a reception bore 21 in the block 2. As shown in FIG. 2, when a pair of piston and cylinder assemblies are engaged within the bores 21 a shoulder of the end region of each assembly engages on a face of the block 2 and the closures 19 are accessible.

#The cylinder 15 of each assembly has radial bores 22 which lead from an internal working chamber 24 of the cylinder 15 to the exterior via a recessed intermediate portion 23 of the cylinder 15. These bores 22 thereby establish connection between the internal chamber 24 and a further external chamber formed between the recessed part 23 and the surrounding wall of the bore 21 in the block 2. These external chambers can be maintained under a constant pressure by appropriate connection with a source of pressure medium and in this way the piston 14 are all subjected to this pressure via the internal chambers 24. Conveniently, the external chamber can lead to a hydraulic pressure line within the block which forms an input to the valves so that the chambers 24 contain hydraulic fluid when the piston rods 16 are extended as shown in FIG. 2. Further bores 25 lead from the exterior of each cylinder 15 to an annular chamber in the cylinder 15 adjacent the rod 16. Sealing rings or gaskets are provided on the exterior of the cylinder 15 between the outlets of the bores 25, 22 and also between the inner end of the cylinder 15 and the outlets of the bores 25.