Patent GB-876727-A (GB)
Title: Hydraulic power transmission systems
IPC: B66F9/22
Filed: 1959-08-25
Abstract: 876,727. Fork-lift trucks. CLARK EQUIPMENT CO. Aug. 25, 1959 [Oct. 29, 1958], No. 28975/59. Class 78 (3). [Also in Groups XXIX and XXXI] An hydraulic system for a vehicle, such as a fork-lift truck, having a prime mover 60, an hydraulic motor 74 and an accumulator 72, comprises pressureresponsive means 92 operatively associated with the accumulator to cause a first pump 62 to charge the accumulator when the prime mover is in motion and a second pump 30 to charge the accumulator when the prime mover is at rest. The motor 74 is arranged to operate the steering mechanism 86 of the vehicle when a valve 78 is actuated and is connected to the accumulator by a line 76 and to a sump 18 by a line 91. The accumulator is charged by the pump 62 when the prime mover 60 is connected by a switch 13 to a power supply 14 and is actuated by a control means 61 associated with forward and reverse switches 124, 126 ; the pump 62 is of the type which, irrespective of its direction of rotation, always has its output connected to a conduit 66 leading to the accumulator. Auxiliary motors 26 and 35, 36, operative to lift and tilt the load, respectively, are supplied with liquid pressure from pumps 16, 30, respectively, driven by a motor 12. The output from the pump 16 passes through a conduit 22 to a control valve 24 operable by a lever 25 to connect the output from the pump to the motor 26 or to the sump 18. The output from the pump 30 passes through a conduit 32 to a valve 34 controlled by a lever 40 to connect the output to one or other of conduits 38, 39 leading to the motors 35, 36 or a conduit 45 leading to the sump. The pump 16 supplies fluid to the motor 26 only but the output from the pump 30, in addition to operating the motors 35, 36, can pass from a port 46 in the valve 34 to a conduit 48 and a solenoid-controlled valve 54 which, when open, connects the supply from the pump 30 to a conduit 56 leading to the conduit 22 of the motor 26 and, when closed, connects the supply to the accumulator 72. The solenoid of the valve 54 is controlled by a gauge 92 responsive to the pressure in the accumulator 72 and, in addition to connecting the output from the pump 30 to the accumulator or conduit 22, also controls the output from the pump 62 in a similar manner. When the prime mover is operated by closing the switch 13 and operating the control means 61, the pump 62 charges the accumulator, which then serves as the primary fluid source for the steering motor 74, until the pressure-responsive gauge 92 is actuated to operate the valve 54 and connect the output from the pump 62 to the line 22 to supplement the output from the pump 16 if the motor 26 is operated by movement of the lever 25 which is interlocked with a switch 122 to energize a coil 114 controlling a switch 112. When the prime mover is inoperative, the accumulator can be charged when the pressure therein falls to a predetermined value by the action of the pressure-responsive gauge automatically closing the valve 54 and starting the motor 12 so that the pump 30 supplies the accumulator through the port 46. Operation of either of the control levers 25, 40, which are interlocked with the switch 122, when the prime mover is inoperative, starts the motor 12 so that the pumps 16, 30 supply fluid pressure to the motors 26, 35, 36, as desired. The prime mover may be an internal combustion engine and serve to charge the battery 14 when the vehicle is at rest. Specification 876,726 is referred to.