| 摘要 |
1413766 Hydraulic control circuits ROBERT BOSCH GmbH 30 Nov 1973 [4 Dec 1972] 55739/73 Heading F1P An hydraulic control circuit, Fig. 1, comprises valves 16, 17 which control rams 13, 12 and influence a control line 32 and a changeover valve 35 which is spring-loaded to a first position in which it connects a line 37 to a reservoir 47 and closes a supply line 31 and has an alternative position in which it connects the supply line 31 to the line 37. The circuit controls the raising and tilting of the side loading wall of a lorry. To tilt the wall outwards valve 17 is moved to position 25. The pump 45 is inoperative so no fluid flows through the control line and valve 35 is therefore in the position shown. Thus, chamber 54 of ram 12 is connected to the reservoir through ducts 56, 39, 21 and the weight of the wall causes outward tilting, forcing fluid out of chamber 51 and drawing it into chamber 54. If this does not happen, due to the lorry standing on a slope, after a delay a cam 27 operates a switch 28 and starts a motor 26 which operates the pump 45. Fluid flows through the control line 32 and the pressure drop caused by a throttle 33 operates the changeover valve 35. This supplies pressure fluid to chamber 54 of ram 12 and tilts the side wall. A pressure limiting valve 29 determines the pressure available. To tilt the side wall inwards the valve 17 is moved to position 24. Cam 27 starts the pump 45 and pressure fluid is delivered to chamber 51 of ram 12 to tilt the side wall. In this position the control line 32 is interrupted so valve 35 is in the position shown and fluid from chamber 54 returns to the reservoir. The hoisting ram 13 is controlled by the valve 16 in a similar way. Lowering is almost always due to the weight of the load but the pump 45 may be switched on if required. Fig. 2 shows a modification in which a pressure limiting valve 63 determines the lower pressure required for tilting the side wall outwards and lowering the load than for hoisting and tilting the side wall inwards. Fig. 3, (not shown), illustrates a circuit in which the changeover valve has three positions instead of two and a cam for controlling the pump.
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