| 摘要 |
781,733. Step-by-step conveyers. KING, Ltd., G. W. May 16, 1956 [May 26, 1955], No. 15281/55. Class 78 (1). A conveyer system comprises a movable unit 14 adapted to support individual load carriers 10 on rollers 18 and movable forwards and backwards along a track 17 and means 40 to prevent reverse movement of any carrier present on the unit during its reverse movement. Each unit may comprise an articulated train of carriages, one of which is reciprocated by a double-acting fluid-pressure actuated ram 19. The device for preventing backward movement comprises a series of plates 40 which are supported by parallel rails 39 and are displaceable freely in a vertical direction. As a carrier 10 moves forward, the sloping end of its top 11 engages in succession the sloping bottoms of the plates 40 and forces them upward. On the return movement of a unit 14, the other sloping end of the top 11 engages the vertical face of the end plate of the series and does not displace it. The end plate, therefore, acts as a stop to retain the carrier. The cylinder 20 of the ram 19 is fixed to one of the carriages and its pistonrod 22 is anchored at 23 to the track 13. Admission of fluid to the ends of the cylinder is controlled by a plate valve, the movable member 24, Fig. 4, of which is attached to an operating arm 25 movable between limiting stops 26, 27. The arm 25 is coupled by a spring 28 to an actuating lever 29 movable between stops 30, 31 in such a manner that when the lever 29 has moved a predetermined amount from one limiting position, the spring will cause the arm 25 to snap over into its alternative limiting position. The lever 29 is actuated by the carriage as the latter approaches the limit of its movement in either direction. In order to ensure that the valve will be actuated in such a way that the motion at the beginning and ending of the ram stroke in each direction will be uniformly accelerated or retarded, a control device, Fig. 5, is mounted on a stationary part of the system with its plunger 32 projecting into the path of two oppositely inclined ramps at, or adjacent to, opposite ends of the cylinder. The control device comprises a cylindrical casing having an inlet port 33 and an exhaust port 34. A member having a central passage 35 provides communication between the ports. A ball 36 is urged on to its seating at the end of the passage by a spring 37 which bears against a piston 38 associated with the plunger 32. As the cylinder nears the end of its stroke, it will depress the plunger and the piston 38 will progressively mask the port 34 to damp the flow of exhaust fluid. When the cylinder reverses, the spring will raise the piston gradually and the motion will accelerate progressively. Specifications 701,610, 719,888 and 763,943 are referred to. |
