Patent GB-1090698-A (GB)
Title: Fluid load positioning device
IPC: B24B47/06
Filed: 1966-06-20
Abstract: 1,090,698. Machine tool details; grinding. A. A. ROTHROCK. June 20, 1966, No. 27371/66. Headings B3B and B3D. [Also in Divisions B5 and F1] A fluid pressure actuated variable stroke piston 20, Fig. 1, suitable for positioning a tool or load 26 has its rod 22 projecting through one end of a cylinder 18 which is open to a pressure fluid supply 28 whilst the large area end of the cylinder is connected to the rod end through a restricted conduit 36, 50, 52, to a return reservoir 32 through a conduit 60, 62 having a relief valve 56 therein and to supply 28 or return 32 through a selector valve 38 when moved from the neutral position shown, and the rod 22 is secured by an arm 66 and a sleeve 72 to a releasable latch 76 which is slidably mounted parallel to the cylinder 18 on support means 10 secured to said cylinder 18, and on which member 10 is slidably mounted a frame member 98 having spaced stops 102 which identify positions to which the rod 22 may be moved and held and which stops are releasable by a movable abutment 96 on the latch member 76; the frame member 98 also carrying a rod 64 by which the relief valve 56 may be held on its seat. Corresponding to stops 102 which may be spaced say one inch apart are fixed contacts 114 bearing on a movable endless two-part belt 116, 118 separated by an insulated spacer 120 and connected to the terminals of a selector switch 134. In operation and assuming the rod 22 is to be moved to the left say one stop, brush 136 of selector switch 134 is moved counterclockwise to abut the next contact, a main switch 138 is closed to complete a circuit from a main supply line L2 through the selected contact 114, the belt portion 116, a fixed collector contact 110, a relay coil 104, a normally closed contact C of a relay coil 108 to the supply terminal L1. Activation of relay 104 opens its normally closed contact C to break circuit of relay 108 and closure of contact B of relay 104 completes the circuit of a solenoid 94 which actuates a rack- and-pinion means 84, 78 for retracting the latchpin 96 from its associated stop 102. The pinion 78 carries a finger 82 which then closes a switch 106 to complete a circuit from the supply terminal L1 through the closed contact B of relay 104, the switch 106, closed contact A of relay 104 and a solenoid 40 for shifting the control valve 38 to the left to the supply terminal L2. The large area end of cylinder 18 is thus connected to reservoir 32, the piston 22 thus moves to the left drawing with it the load 26, the latch 76 and the belt 116, 118, the spacer element 120 of which is mechanically connected to the latch 76. When element 120 abuts the fixed contact 114 to which selector switch 136 is connected the circuit of relay 104 is broken, associated contacts A, B, C return to the position shown, thus de-energizing the latch control solenoid 94 and the valve solenoid 40. In practice the piston 20 and latch 76 proceed beyond the desired stop and are returned by pump delivery bled through restriction 52 to the larger end of the cylinder. In the event of said return movement to the right resulting in the latch pin 96 moving frame 98, the rod 64 carried thereby allows relief valve 56 to open and thus stabilizes the piston 20 at the desired position. To move the piston 20 say two stops to the right from the set point first established, brush 136 is moved clockwise to the contact next adjacent the position shown in Fig. 1 and upon closing main switch 138 latch solenoid is first energized followed by valve solenoid 46 and these solenoids are de-energized when spacer element 120 reaches the selected fixed contact 114. Valve 38 is thus returned to the position shown. It is also possible to displace the piston to a fraction of the space between stops. To this end the frame 98 carrying said stops 102 is itself displaced by a further frame 148 which is positioned by compressed air actuated piston- and-cylinder devices 152, 156.