Patent GB-1406987-A (GB)
Title: Hydraulic actuator
IPC: D04B15/94
Filed: 1971-08-04
Abstract: 1406987 Hydraulic actuators T P PRIESTLEY and J D GARSIDE 3 Aug 1972 [4 Aug 1971] 36572/71 Heading F1D [Also in Division D1] An hydraulic actuator comprises a first cylinder 3 with ports 19, 22 at or adjacent to its ends and port means 20, 21 intermediate its ends controlled by double-acting piston 11 operable to displace an actuating member 12 between two end positions and a second cylinder 5 connected end to end to the first and containing a piston 5 and having a port 17, a probe 6 extending between the cylinders to prevent the pistons from approaching one another too closely, ports 19, 22, 21, and 17 being connected to progressively adjustable valve means 41, 43, 42, 40 whereby they are connected in a predetermined sequence to a source of pressurized hydraulic medium and to exhaust. A bobbin 33 rotated by a shaft 34 has two part circumferential grooves 45A, 45B; 46A, B; 47A, B; 48A, B; aligned with each port 40, 41, 42, 43 in casing 30. A circumferential groove 44 connected with a port 39 connected to a source of fluid under pressure is connected to one of each pair of grooves the other being connected by a bore 49 to an axial bore 38 connected to atmospheric pressure. Ports 17, 18 in cylinder 2 are connected to port 40 and atmosphere respectively and ports 19, 21, 22 and 20 in cylinder 3 are connected respectively to ports 41-43 and atmosphere. The grooves and ports are so arranged that, in the first quadrant of movement of bobbin 33, pistons 5, 11 move fully to the right and piston 11 is separated from probe 6. In the second quadrant piston 11 moves to the left and abuts probe 6. In the third quadrant the pistons 5, 11 move fully to left and rod 12 is fully retracted. Member 12 "dwells" in the fourth quadrant. One valve may operate several actuators. The displacements may be applied to the needles of a knitting machine which are moved to knitting, tuck and miss positions. The machine may be circular, V-bed or oval cylinder. In a stationary cylinder machine eight or more sets of ports may be provided corresponding to set 40 to 43 equally spaced round casing 30 so that rotation of bobbin 33 causes the pressures and exhausts to appear at each set of ports in turn. To increase the possible number of actuators still further the valve may be extended by the addition of further grooves e.g. it may have four sets of four pairs of part circular grooves and sixteen sets of four ports for each set of grooves making 256 in all. The grooves are arranged in sixteen lines but the associated grooves are offset to produce successive operation of the actuators. If the needles "dwell" as they are lowered there must be two needles per feed but, if they move directly up and down, there may be one feed per needle. For patterning, to cause needles to miss pulses must not reach ports 17 and 19 and to cause needles to tuck pulses must not reach port 19. Solenoid valves are too slow so that a system of separate paths between each port and four ports in the valve casing is used consisting of manifold blocks 53 to 56, blocks 53 and 54 being connected to blocks 57 to 60 and 61 to 64.