Patent GB-932279-A (GB)
Title: Improvements in or relating to hydraulic control mechanism
IPC: B60P1/16
Filed: 1962-05-10
Abstract: 932,279. Hydraulic apparatus. LIBERECKE AUTOMOBILOVE ZAVODY, NARODNI PODNIK. May 10, 1962 [May 10, 1961], No. 18034/62. Class 69 (2). An hydraulic control mechanism for tipping the body of an automobile or trailer comprises a control lever 1, a distributing mechanism 14, a working cylinder 36, and a floating piston 26 which is axially slidable in a cylinder 35 of the distributing mechanism with one face adjacent the end face of a distributing member 9 of the mechanism and the other face connected by a return line 21 to a valve chamber 22 of an end valve 23 for the working cylinder, the piston being provided with a by-pass channel 27 adapted to be closed by a non-return valve 28 actuated against the pressure of a spring 29 by a fluid pressure impulse within the return line resulting from actuation of the end valve when the body reaches an extreme position whereby the piston moves the distributing member to a position wherein the fluid supplied by a pump 13 is by-passed from a pressure line back to a tank 15. The distributing mechanism 14 is mounted on the tank 15 and has a bore communicating with the tank by means of passages 16, 17 and a relief valve 18. The bore is also connected by a line 19 to the discharge from the pump 13 and to the valve chamber 22 of the working cylinder 36 by a line 20. A line 21 leads from the valve chamber 22 to the cylinder 35 containing the floating piston 26. The control lever 2 is normally retained in position "A" by a spring 5 urging an end 4 into an aperture in a bush 3. In the position "A," the distributing member 9 is in the position shown connecting the lines 19 and 20 to the passages 16, 17, respectively, and a clutch 12 is disengaged so that the pump is inoperative. The bodywork of the automobile is tipped by lifting the lever to disengage the end 4 from the aperture in the bush and moving it to the position " C," the linkage 7, 8, 10, 11 engaging the clutch 12 to drive the pump and the member 9 moving to an extreme right-hand position determined by abutment of the floating piston against an end wall of the cylinder 35 so that the discharge line 19 is connected to the line 20 leading to the valve chamber 22 and working cylinder 36; the by-pass passage 22 enables fluid in the end of the cylinder 35 to pass through a passage 24 in the member 9 to the passage 17 and tank. When the bodywork reaches its extreme position, the end valve 23 is actuated and a pressure pulse acts through line 21 on the non-return valve 28 which moves against the spring 29 to close the by-pass passage 27. The closing of the non- return valve causes the fluid pressure in line 21 to move the piston 26 to its left and the member 9 to an intermediate position, the lever 1 also moving to a corresponding position " B." In the intermediate position, the line 20 is blocked, so that the bodywork is hydraulically locked in its upper position, and the line 19 is connected to the passage 16 to unload the pump. Movement of the lever 1 to its initial position "A" disconnects the clutch 12 to stop the pump and connects line 20 through passages 24, 17 to the tank to permit the bodywork to be lowered by gravity. Two working cylinders 36, one for the automobile and the other for its trailer, may be provided, a selector valve in the line 20 directing fluid to one or the other.