Patent GB-683870-A (GB)
Title: Control mechanism for fluid pressure operated presses
IPC: D06F71/06
Filed: 1951-05-21
Abstract: 683,870. Ironing-presses. AMERICAN LAUNDRY MACHINERY CO. May 21, 1951. No. 11845/51. Class 138 (ii). Control mechanism for the fluid-pressure operating motor 14 of a pressing-machine comprises means biasing an inlet valve 39 to closed position and an exhaust valve 32 to open position, the exhaust valve being movably mounted in a chamber 33 which also contains a piston 31, operator operated means for supplying fluid pressure to the outer face of the piston 31 to move it to close the exhaust valve and open the inlet valve, means for supplying fluid pressure to the operating motor 14 when the inlet valve is open and the exhaust valve closed, means controlled by the motor 14 for supplying fluid pressure to the exhaust valve to keep it closed and to the inner face of the piston 31 to move it away from the exhaust valve, and operator operated means for opening the exhaust valve and closing the inlet valve. In the example the controlling mechanism comprises three valve devices A, B and C two of which, A, B, are combined as a single unit Fig. 2, (not shown). The exhaust valve 32 has an axial stem which is slidable in a cavity in the piston 31. The valve 32 carries sealing rings 32a, one on each side of an annular exhaust passage 34 leading to the atmosphere. Between valves 32, 39 is a longitudinally grooved rod 38 slidable in a passage 37. Valves 32, 39 are biased to open and closed positions respectively by a spring 40. Inlet valve 39 works in a chamber 41 connected by a passage 42 and adjustable needle valve 43 to a branch 24 of a passage 22 in the valve device A. Compressed air is admitted to passage 22 through a supply pipe 19, chamber 20 and filter screen 21. A second branch 23 of passage 22 leads through a pipe 25 to a valve 26 having an exhaust port 27 and operated by a pivoted manual 28. When valve 26 is open, pressure flows through a pipe 29 to a similar valve C operated by a manual 28a, and thence through a pipe 30 to the chamber 33. Operation. Fig. 1 shows all parts in idle position. By simultaneously depressing the manuals 28, 28a air flows from supply pipe 19 through valves A, C to chamber 33, moving the piston 31, valve 32, rod 38 and valve 39 to the left. Opening of inlet valve 39 allows air to flow from passage 22 through branch 24 to chamber 41 and through a pipe 44 to the pressure side of a piston 15 in motor 14. Piston 15 and its rod 16 move toggles 17 to close the press 13, 11. If either manual 28 or 28a is released before the press is fully closed the motor 14 is opened to exhaust through passage 34, and the press opens. When the piston 15 passes a port in the side of the cylinder, pressure is communicated through a pipe 45, a chamber 46 and passage 51 to the chamber 33. The manuals 28, 28a may now be released. Piston 31 is returned to its original position, but the exhaust valve 32 remains closed, the pressure in the chamber. 33 being greater than the combined fluid and spring pressures tending to open it. The press remains closed until a manual 48 is depressed, thus opening chamber 33 to exhaust through an exhaust valve 47 and pipe 50. Valves 32, 39 return to their original positions and the pressure in motor 14 escapes through pipe 45 and valve 47 or outlet 34, and through pipe 44 to chamber 37 and outlet 34. If manual 48 is released before piston 15 moves back past the pipe 45, re-actuation of the valve mechanism is prevented by the non-piston form of valve 32 and the passage 34, now uncovered. Instantaneous release of valve 32 is ensured by making the entrance port M of chamber 46 substantially smaller than the outlet port N, e.g. area of port N should be four times area of port M.