Patent GB-947761-A (GB)
Title: Improvements relating to mechanically-propelled vehicles
IPC: B60K17/10
Filed: 1958-11-07
Abstract: 947,761. Motor vehicle hydraulic transmissions. RELIANCE TRUCKS Ltd., and G. W. MARSHALL. Feb. 1, 1960 [Nov. 7, 1958], No. 35900/58. Heading B7H. [Also in Division F2] A vehicle, which may be a three-wheeled material-handling vehicle, is propelled from a prime mover through an hydraulic pump and motor, there being a variable relief valve connected to the delivery of the pump for adjusting the maximum delivery pressure and thereby the power output of the motor. There may be two motors coupled to the same or different wheels and control means to provide series and parallel connections to the pump delivery which may be manually or automatically operated in response to the torque demanded from the motors. As shown, a single steerable wheel of a three-wheel vehicle may be driven by one or two hydraulic motors 24 which (if there are two) are attached one each side of the wheel to plates 28 upon the fork members 4 in which the wheels are pivoted upon an axle 15. A spigot 13 rotates in a housing 14 and legs 3 depend therefrom, the fork members 4 being carried by the legs 3 upon pivots 5 incorporating friction discs 6 and pressure plates 7, the fork members also being supported by springs 10. The motor 24 drives the wheel 2 through a chain and sprockets 30, 31 and the other motor, 25, not shown, similarly drives sprocket 35. The plates 26 pivot upon bolts 27 and may be locked in position by bolts 28 co-operating with arcuate slots 29, a position adjusting screw 32 being provided. A sprocket 19 attached to the spigot 13 beneath the vehicle frame 1 is connected by a chain to a sprocket upon a vertical steering shaft, not shown. The motors 24 and 25 may be driven from a pump 37 connected to an internal-combustion engine 38. The pump delivers to a manifold 39 in parallel with a pressure relief valve 40 which acts as a speed control and is operated by a pedal 41 interconnected through links 38a, 38b with the prime mover throttle control. Alternatively, or additionally, the prime mover throttle may be controlled in response to hydraulic pressure changes in the manifold 39. The manifold is connected to a direction control valve 42 providing forward, neutral and reverse positions and to a " change over " valve 43 from which the motors 24 and 25 may be driven in series or in parallel. A return line 36a connects the manifold 39, the pressure relief valve 40 and a relay valve 61 to the reservoir 36 through a filter 86. Auxiliary apparatus mounted on the vehicle, e.g. the lifting device of a fork-lift truck the jib of a crane, or a winch, which is driven by an hydraulic motor may be operated from the manifold 39 under the control of a valve 83 through a line 82. A pressure relief valve 84 and pressure gauge 85 are provided. The changeover valve 43, Fig. 5, has ports 46 and 48 connected to the inlet ports of motors 24 and 25 respectively, ports 47 and 49 connected to the exhaust ports of the motors 24 and 25 respectively, a fluid supply connection 44 and return connection 45. The valve spool 50 has annular grooves 56 and 57 and a bore 60, and in the position shown connects the motors in series, the fluid route being through 44, 56 and 46, motor 24, 47, 59, 60, 48, motor 25 and return, 49, 45. When the spool is moved to the left, 46 and 48 are connected in parallel through the annulus 56 and similarly the annulus 57 connects 47 and 49. The spool 50 may be manually operated by a mechanical connection at one end, or by a manually operated fluid supply acting upon a piston 51 (a return spring 54 being provided) or by a fluid supply dependent upon the output of the pump 37 under the control of a relay valve 61. The relay valve 61 is connected by the line 62 to the pump and by the lines 63 and 71 to the connection 55 (Fig. 5) of the valve 43, a return 72 to the reservoir being provided. A shuttle 64 has oppositely extending tubular pieces 65 and 66 having radial bores 68 and 70 respectively. A spring 74 acting between a piston 75 and a collar 73 urges the shuttle to the right. A non-return valve 81 and a passage 77 controlled by a needle valve 78 by-passing the piston 75 are provided. When the pressure in the line 62 connected to the pump delivery line reaches a certain value, the shuttle 64 moves to the left and fluid passes through tube 65, passages 68 and line 71 to operate the valve 43 to put the motors in parallel. When the pressure falls to a certain value, the shuttle moves to the right under the action of spring 74, and, under the action of spring 54, the valve 43 returns the motors to the series connection. Owing to the provision of the valve 81, by-pass 77, and the differing diameters 80 and 79 on the shuttle member, a hunting motion is prevented. The piston 75 and by-pass 77 prevent the occurrence of surges. The pump 37 is a positive displacement pump.