Hydraulic controller
This invention relates to a hydraulic controller which may be used, for example, to control the supply of pressure fluid to hydraulic ram cylinders of self-advancing mine-roof supports. 
     One type of hydraulic controller comprises a controller casing, a rotatably mounted master valve (i.e. flow-directing member) containing a check valve which can be pushed open by a tappet displaceable by movement of a manually operable control arm, and a spring-loaded tubular sealing plunger which by rotation of the rotary master valve can be selectively moved into sealing register with any one of a plurality of connecting bores concentrically disposed about the controller axis in a bottom plate of the controller casing and leading to the several ram cylinders, the underside of the rotary master valve body being formed with an annular recess providing communication between the non-selected connecting bores and a return line. 
     The controller described above serves to control the admission of high pressure hydraulic pressure fluid to the several ram cylinders from a central point. When the control arm is hingeably raised it will cause the rotary master valve to deliver the high pressure fluid through the check valve in the body of the master valve to a selected connecting bore and thence to the associated ram cylinder. This arrangement permits pressure to be supplied to all the ram cylinders in the support system in any desired sequential order. However, it has been found that it would be desirable to perform some operations, such as the retraction of ram cylinders, by fluid at a lower pressure acting on a small annular piston face. This is desirable firstly because the bearing supporting the thrust of a ram cylinder can generally sustain a greater load than the bearing which takes up the tension, and secondly because the speeds of retraction and advance of an actuator operated from a low pressure line will be slower and thus more suitable for some purposes because of the reduced rate of supply. The lower pressure could be obtained from the high pressure line through a reducing valve to give better metering for the controlling action. However, since conventional controllers are only suitable for controlling a restricted pressure range, the employment of a low pressure line in addition to a high pressure line would necessitate the provision of two separate controllers of the known type. 
     When advancing or controlling other functions of the selfadvancing system it may be advantageous if two functions, such as extending both the advancing ram cylinder and the roofbar cylinders, can be performed at the same time for the purpose of keeping the roofbar in sliding contact with the roof during advance of the supports by admitting low pressure into the roofbar cylinders. This would require the two controllers to be operated at the same time, a necessity calling for a considerable amount of skill. 
     It is therefore an aim of the present invention to provide a hydraulic controller which may be used for controlling the supply of a high pressure fluid source and a lower pressure fluid source to hydraulic rams, which controller has a pair of inlets and several outlets, and incorporates a safety device which in use of the controller will prevent one or more of the outlets from being connected to the source of high pressure fluid. 
     With this aim in view, the invention is directed to a hydraulic controller comprising a casing having a pair of inlets and a plurality of outlets, and a flow-directing member rotatable in the casing to each of a plurality of positions for directing liquid from the inlets to selected ones of the outlets by way of a pair of passages extending through the flow-directing member, each passage being connected at its inlet end to a respective one of the two casing inlets, and being connected at its outlet end to a selected one of the casing outlets according to the selected position of the flow-directing member, each passage being associated with a respective one of a pair of valves mounted in the flow-directing member and movable between passage-opening and passage-closing positions, the controller having locking means which operate in at least one of the selected positions of the flow-directing member to prevent movement of a first one of the valves to its passage-opening position. 
     In use of the controller, a source of high pressure hydraulic fluid will be connected to that one of the casing inlets which communicates with the passage containing the first valve, and a source of low pressure hydraulic fluid will be connected to the other casing inlet. In each selected position of the flow-directing member in which the locking means operate, it is not possible to open the first valve so that high pressure fluid cannot be supplied to the outlet of the passage which is closed by the first valve. 
     The control of the supply of high pressure and low pressure jointly by a single controller is of great advantage when the controller is used to control the mining apparatus described above, since it greatly simplifies control of roof supports comprising a large number of ram cylinders and hydraulic actuators. 
     It is preferred that each controller valve has a manually-controlled operating arm by means of which the valve can be opened, the two control arms being operable selectively either separately or simultaneously. This enables operation of two ram cylinders to be controlled simultaneously or individually at will. 
     The locking means may include a first locking pin slidable in the flow-directing member and biased towards a locking position from which it is forced to retreat during opening of the first valve, the arrangement being such that, when the flow-directing member is in a position in which the locking means operate, the pin is prevented from retreating from its locking position by a stop carried by the casing. The stop may be detachably carried by the casing, and the casing may be adapted to carry detachably a stop in each position with which the first locking pin is aligned in the said selected positions of the flow-directing member. By an appropriate disposition of the stops which can be easily exchanged, the controller can be adapted to select which operations can be performed exclusively with low pressure. Conveniently the said locking means also operate when the flow-directing member is in an intermediate position between adjacent ones of the said selected positions. 
     It is advantageous if the control arms are biased towards an inoperative position, and means are provided for retaining one or both of the operating arms in a valve-opening position after it has been released by an operator. This enables for instance the face conveyor to be held up against the coal face by the appropriate ram cylinder for an extended period of time. 
    
    
     An embodiment of hydraulic controller according to the invention will now be more particularly described by way of example and with reference to the drawings, in which: 
     FIG. 1 is a part longitudinal section of a hydraulic controller, according to the invention, the lower portion containing the connections being represented in an external elevational view; 
     FIG. 2 is a longitudinal section of the controller in FIG. 1, but the section is taken on the line A--A; 
     FIG. 3 is a cross section of the controller in FIG. 1, the section being taken on the line B--B; and 
     FIG. 4 is a view of the control unit from above. 
    
    
     The cylindrical interior of the external casing 1 of a hydraulic controller contains a rotatably mounted master valve 2 which serves to direct the supply of hydraulic fluid to appropriate ones of ram cylinders, not shown, of self-advancing supports in a mine. The master valve is thus a flow-directing member. The body of the master valve is formed with a cylindrical neck 4 which is rotatable in a bottom plate 3 of the controller casing, a main body part 5 which slidably bears on an annular internal flange 6 projecting into the interior of the controller casing 1, and an upper part 7, the parts 4, 5 and 7 being rotatable as a single unit. The part 7 is surmounted by a bearing head 8 rotatable with the valve 2 and containing two axially aligned parts of a divided shaft 9 fitted with two parallel manually operable control arms 10a/b which are operable separately or simultaneously. The axis of the shaft 9 is laterally offset from the axis of rotation of the valve 2. 
     A total of fifteen different supply and return pipes lead to the hydraulic controller, their connections 11, 12a to 12m, and 14 all being located on the bottom plate 3 to permit the flexible pipelines to be placed with the greatest economy in space. The connection 11 for a high pressure line is situated in the extension of the axis of rotation of the valve 2 on the underside of the bottom plate 3. The twelve connections 12a to 12m (12j is not used) for pipelines leading to the several ram cylinders are disposed concentrically about the connection 11. A low pressure line and the return line lead to connections 13 and 14 respectively on the side of the controller casing. 
     On diametrically opposite sides of its axis of rotation the lower part 5 of the rotary valve 2 contains two check valves 17a/b each comprising a valve seat 15a/b for a spring-loaded valve cone 16a/b. Each valve 17a, 17b serves to close a respective one of two passages through valve 2. The check valve 17a communicates with the low pressure connection 13 and the valve 17b with the high pressure connection 11. From connection 11 of the high pressure line a coaxial duct 18 leads to a short radial bore 19 beneath the high pressure check valve 17b. The low pressure check valve 17a communicates through an axial duct 20 and an annular groove 21 in the neck 4 of the rotary master valve 2 with a radial duct 22 leading to connection 13 of the low pressure line. Of the two control arms 10a/b which are affixed to the two halves of the shaft 9 in the bearing head 8 of the rotary valve 2, and which can be independently or jointly operated, one control arm 10a is associated with the low pressure check valve 17a and the other 10b with the high pressure check valve 17b. In order to open the check valves 17a/b the control arms 10a/b must be pivoted from the horizontal into the vertical. This causes eccentric members 23a/b mounted on the corresponding halves of the shaft 9 to depress thrust members 24a/b located coaxially with the check valves 17a/b and adapted to co-operate with tappets 25a/b which push the check valves 16a/b off their seats 15a/b. The hydraulic fluid in the high and low pressure lines will then flow separately through the annular valve chambers 26a/b and transverse ducts 27a/b to spring-loaded slidable tubular plungers 28a/b located on diametrically opposite sides of part 7 of the rotary valve 2. In any selected control position of the rotary master valve 2 these tubular plungers will be pressed into sealing contact with the end faces surrounding bores 29a to m which lead to a pair of the connections 12a to m on diametrically opposite sides of the master valve axis, thus providing a path for the hydraulic high and low pressure fluids to flow through the selected ones of connections 12a to  m to the respective ram cylinders. The bores 29a to m which are not selected are connected by an annular channel 30 under the body of the rotary valve 2 and through an angle duct 31 in the bottom plate 3 of the casing 1 to the connection 14 of the fluid return line. 
     In the described arrangement the master valve 2 can be turned into any desired position of control and each of the twelve connecting bores 29a to m can be connected to the outlet ends of the two passages through the valve 2 connected to the high pressure and low pressure supply. In order to arrange that for functional or constructional reasons some connecting bores 29l to m can be supplied only with low pressure and never with high pressure, the upper portion 7 of the rotary valve 2, in radial bores 32a/b, contains radially slidable locking pins 33a/b of different lengths in respect of each check valve 17a/b. 
     When the check valves 17a/b are closed the inner convex heads of the locking pins 33a/b engage trapeze-section peripheral grooves 34a/b in the thrust members 24a/b. The locking pins are biased by compression springs 35a/b supported by sleeves 36a/b embracing the smooth stem of the locking pins 33a/b which in turn have conically tapered outer ends. In each selectable control position these sleeves snap into engagement with holes 37a to m provided in the casing 1 at equidistant peripheral intervals. The angular disposition of the holes 37a to m agrees with the angular disposition of the connecting bores 29a to m. Into the outer holes 37a to m, there are inserted, from the outside, locking screws 38a/b of different lengths, longer locking screws 38a which serve as stops being screwed into those ones of holes 37a to m which are associated with connecting bores 29a to m that are to be supplied only with low pressure fluid, whereas shorter screws 38b are screwed into those ones of holes 37a to m which are associated with connecting holes 29a to m that are to be supplied selectively with high pressure or with low pressure fluid. The holes 37a to 37m are thus in part occupied by locking screws, so that they form recesses into which ends of the locking pins may move. The recesses closed by the longer locking pins are of course shallower than the other recesses closed by the shorter pins. The length of the locking pins 33a/b which are displaceable radially outwards against the locking screws 38a/b is appropriately chosen. The locking pin 33a associated with the low pressure check valve 17a is shorter than the locking pin 33b associated with the high pressurecheck valve 17b and the length of both locking pins 33a/b is also so chosen that the thrust pins 24a/b cannot be displaced to open the check valves whilst the rotary master valve 2 is in an intermediate position between two selectable operating positions which are determined by the positions of the connecting bores 29a to m. If the valve 2 is turned into a wrong position, then the long locking pin 33b which is associated with the high pressure side will face a stop comprised by a long locking screw 38a associated with the low pressure side, and the thrust pin 24b cannot then be displaced for opening valve 17b. The control arm 10b will therefore be locked. 
     The pin 33a only serves as a locking pin in intermediate positions of the valve 2, in which case the end of pin 33a engages the casing which forms an abutment. The screws 38b do not prevent either valve from being opened, and thus serve mainly as dust caps. 
     The several connections to the ram cylinders are identified on the casing by suitable symbols (not shown). Preferably the cylinders are connected to the hydraulic controller in the order in which they are required to function so that the appropriate connections are established in series. Pairs of cylinders which are to be simultaneously supplied one with high pressure and the other with low pressure are connected to the hydraulic controller at two of the connections 12a to m angularly separated by 180°. The control arms 10a/b are used to turn the valve 2 into its several operative positions and the click of the spring-loaded sleeves 36a/b into engagement with a pair of the holes 37a to m indicates that an operating position has been reached. For jointly opening the check valves 17a/b the control arms 10a/b are together hingeably raised from their horizontal off-position into their vertical on-position. The control arms 10a/b can also be individually operated in any desired order. Since the eccentric members 23a/b are in an unstable equilibrium position when the check valves are open, the control arms 10a/b will return into their off-positions of their own accord. 
     However, if a control arm 10a or 10b is required to remain in an on-position for any length of time it can be retained in this position by an arresting pin, such as the pin 39 located in the bearing head 8 of the rotary valve 2 at the level of the shaft 9, the arresting pin being slidably pushed into engagement with a bore 40 which extends through the axis of rotation of the shaft 9. A spring-loaded sleeve 41 surrounding the arresting pin 39 and containing a peripheral groove 42 is moved towards the eccentric shaft 9. A tappet 43 which engages this groove and which retreats into a recess 44 in the casing 1 when the sleeve 41 is depressed will then engage the end of the sleeve 41 and retain it in its inwardly displaced position. Renewed pressure releases the self-locking arrestor and allows it to return into its normal position.