Patent GB-433281-A (GB)
Title: Improvements in steering mechanism for endless track vehicles
IPC: B62D11/18
Filed: 1933-11-06
Abstract: 433,281. Hydraulic transmission of power. DIAMANT, S., FALCHI, A., and ROCCA, E., 36, Via XX Settembre, Genoa, Italy. Nov. 6, 1933, No. 30792. Void [Abridged as open to inspection under Sect. 91 of the Acts, Dec. 8, 1934]. [Class 69 (ii)] [See also Group XXXI] An endless-track vehicle is steered by driving each endless track independently of the other through hydraulic transmission means providing infinitely variable ratios between the driving and the driven shafts. In the construction shown the propeller shaft 1, Fig. 14, drives a transverse shaft 7 through bevel gearing, and the shaft 7 drives the endless tracks (not shown), through two hydraulic variable speed and reversing gears 9, 11 and pinions 10, 12. Each hydraulic gear is normally out of action so that there is a direct drive from the shaft 7 to the pinions 10, 12. The gears are controlled by valves operated alternatively by the steering hand wheel through cables 13, 14 levers 21, 22 and valve rods 31, 32, the valves being normally held in the direct drive position by springs 29<1>, 30<1>. When one of the valves is operated by its cable 13 or 14 the corresponding pinion 10 or 12 is driven at a reduced speed, and finally may be reversed if the gear casing 33 is held by a separately-controlled brake 74. The cables 13, 14 may be simultaneously operated to reverse the drive to the pinions 10, 12. Each hydraulic gear comprises a driving shaft 7, Figs. 1-3, a driven shaft 63, an outer cylindrical casing 33 concentric with shaft 7, an inner cylindrical casing 34 eccentric to shaft 7, and sliding vane pistons 43, 431 fixed respectively on the driving and driven shafts. The casing 34 is divided into pump and motor compartments by a partition 35 and the horseshoe - shaped space between the outer and inner casings is divided first into two parts by a longitudinal partition 52, 60, Figs. 3 and 8, one of the parts being a chamber 37 while the other part is again divided into two chambers 38, 39 by a transverse wall 36. The gear is controlled by a slidable valve 55, Figs. 1 and 11 working between the wall 52 and an adjacent wall 53 at the pump end of the casing, the valve being formed with an end port 59 and side ports 57, 58 co-operating with ports 56 formed in the walls 52, 53. Ports 48<11>, 49 are formed in the pump part of casing 34 and ports 50, 51 in the motor part. When valve 55 is in the normal position shown in Fig. 11 the ports 56 are closed by the valve, no liquid can circulate, and the pistons 43, 431 and casing 33 are all locked together to give a direct drive. As the valve 55 is moved to the left the ports 56 are gradually opened and liquid is circulated by the pistons in the three chambers 37 ... 39, the shaft 63 being driven at a reduced speed, until finally, when the valve ports 57, 58 are fully open to the ports 56, the liquid circulates idly and no drive is transmitted. To reverse the drive the casing 33 is held stationary by its brake 74 and the valve is moved to its farthest left position, as shown in Fig. 13, one port 56 being closed by the valve while the other is still fully open to valve port 58. In this position, with the piston 43 rotating in clockwise direction, liquid is forced through the ports 48<11>, ports 56, 58 and 59 to the motor chamber 38 and through ports 50 to rotate the piston 431 in counterclockwise direction, passing back to the pump chamber through ports 51 and the chamber 37.