Patent GB-687302-A (GB)
Title: Apparatus for loading and unloading vehicles
IPC: B60P1/44
Filed: 1950-08-08
Abstract: 687,302. Vehicle fittings for loading; load-handling machines. PHIL WOOD INDUSTRIES, Ltd. Aug. 8, 1950. [Aug. 8, 1949] No. 19731/50. Classes 78 (iii) and 78 (iv). A tailgate loader of the kind which consists of a platform 16, Fig. 1B connected to a vehicle for movement between ground level and the floor of the vehicle, which platform may be pivoted into a vertical position to form the tailgate of the vehicle, is characterised by an operating linkage consisting of spaced arms 15 pivoted at one end on a horizontal axis on the platform and at the other end secured to a torque member 13 mounted for rotation on the vehicle to raise and lower the platform, levers 20 pivoted between their ends on a shaft 18 parallel to and spaced from the torque member, one end of each lever being linked at 23 to the platform at a point 25 above said axis on the platform and nearer to the torque member than said axis, and the other end cooperating with cam &c. means 14 for limiting pivoting of the levers under the weight of the platform. As shown, two fluid pressureactuators 39, 44, Fig. 3, are provided, one, 39 for raising and lowering the platform 16, while the other rotates the shaft 18 against the weight of the platform to pivot the latter into the vertical position. The torque member 13 consists of a cylindrical shaft mounted in bearings 12 on the chassis and is rotated to raise the platform through a chain 32 secured to and passing round a quadrant 27 secured to member 13 and coupled at its other end by an adjustable U-shaped shackle 37 to the piston rod 38 of cylinder 39. A crank arm 46, Fig. 3, which extends forwardly with respect to the vehicle is secured to shaft 18 and coupled at its forward end to the piston rod 45 of actuator cylinder 44, so that as the piston rod is drawn into the cylinder 44 by pressure applied to the front of its piston, shaft 18 is rotated clockwise to lift roller 26 away from the cam 14 and pivot platform 16 into the vertical position. The fluid pressure system, Fig. 7, is controlled by a valve 53 consisting of a valve bore 54 and a spool 55 having two operative lands 76, 77 which is longitudinally slidable into four operative positions by means of a bell crank 56 and linkage coupling the latter to an operating lever 64, Fig. 1B. The positions of lever 64 for the various operations indicated on Fig. 1B correspond to the positions of spool 55 so that when lever 64 is in the "pivot position" shown the spool 55 is in its highest position. Fig. 7 shows spool 55 in the next lower or "raise position". Fluid from a pump 49 driven from a take off on the vehicle gear box is delivered to the inlet 72 of the valve 53 and passes between lands 76, 77 and along pipe 79 to cylinder 39 where it acts on the front of the piston 80 to raise the platform until, when fully raised, fluid escapes through a pipe 83 and passes above land 77 in the valve and via passage 87 to the double outlet 73, 74 which returns it to the pump. A further pipe 85 ensures that the rear of the piston is always connected to the outlet, the movement being positively stopped by an extension 89 of the piston engaging end wall 90 of the cylinder. To hold the platform in an intermediate position spool 55 is lowered one position corresponding to the "hold position" of lever 64 whereby land 77 blocks the passage 78 leading to pipe 79 and thus isolates the latter. In the lowest position of spool 55 corresponding to the "lower position" of lever 64 land 77 comes below passage 78 so that pipe 79 communicates with the outlet, and land 76 is below a passage leading to outlet 73 so that fluid is shortcircuited from inlet 72 to outlet 73. Platform 16 thus drops slowly under its own weight. In each of these positions pipe 83 communicates with the outlet, and a pipe 92 leading to the front of the piston 93 in cylinder 44 and in communication with pipe 83 is therefore also in communication with the outlet. In the "pivot position" however land 77 cuts off pipes 83 and 92 from the outlet while fluid passes between the lands along pipe 79 into cylinder 39, thence from cylinder 39 via pipes 83 and 92 to cylinder 44, fluid passing from the rear of piston 93 through pipe 96 to the outlet, so that piston 93 is retracted to pivot the platform into the vertical position for use as a tail board. Lever 64 is prevented from being moved into the "pivot position" unless the platform is fully raised by a hook 42, Fig. 1A, which is pivoted at 66 and coupled by a lever 67 and lost motion linkage 68 to a crank 59 forming part of the linkage between lever 64 and the valve 53. As shown the platform is fully raised and hook 42 has dropped between the limbs of shackle 37, whereby lever 64 can be moved to the "pivot position". When lever 64 is moved into the lower" position" hook 42 is raised by the lost motion linkage so as to allow the piston rod 38 to extend below the hook during lowering. With the piston rod thus extended hook 42 is prevented from dropping between the limbs of shackle 37, and this causes the lost-motion linkage 68 to prevent movement of lever 64 into the "pivot position". Specification 687,340 is referred to.