GB1275636A - Hydraulic control system - Google Patents

Abstract

1275636 Earth-working ILSBO INDUSTRIER AB 5 June 1969 [6 June 1968] 28483/69 Heading E1F A tool holder pivotally mounted on control arms of a crane, or loader is kept at a set angle to the ground, as the control arms are pivoted, by means of a supervisory unit 16-23 which in response to movement of the control arm permits passage of fluid to valve 25 which directs fluid to the appropriate side of a hydraulic ram connected between the tool holder and arms. Wire 15 of a Bowden cable is connected to a control rod 16 of the supervisory unit and is so disposed around pulleys on the pivotal shafts of the arms and of the tool holder that a change in the angle of the tool holder from the set angle causes movement of the control rod. During raising of the arms by a second hydraulic ram, return fluid from the ram is normally diverted from screw 28 through channel 34, chamber 53, 54 and channel 33. Movement of control rod 16 opens a passage between chambers 40 and 39 and allows some of the return fluid to pass along pathway 35, 39, 40, 45, to throttling disc 26 of valve 25. The pressure created at the disc causes the plunger of the valve to move to connect channel 53 to channel 55 instead of channel 54. From channel 55 the fluid passes to the ram to adjust the position of the tool holder. When the arms are being lowered return fluid from the second ram passes through screw 29 and, through a one-way valve means, passes through channel 49 to chamber 38. Movement of the control rod in the opposite direction links chamber 38 with chamber 37 and, through channel 44, with chamber 40. A higher pressure is created this time at throttling disc 26 because the return fluid is at a higher pressure so that the plunger of the valve connects chamber 54 with chamber 58 and thus directs pressure fluid from screw 28 to screw 32 leading to the first ram.