FR1511685A - Hydraulic transmission for road vehicles - Google Patents

Abstract

1,140,482. Controlling hydrostatic transmissions. HAKO-WERKE HANS KOCH & SOHN. 3 Jan., 1967 [3 Jan., 1966], No. 389/67. Headings F2C and F2D. In an open circuit hydrostatic transmission including an axial piston pump 2, a hydrostatic motor 5, an adjustable throttle valve 7 in the pump suction line 3, and, between the pump and the motor, a reversing slide valve 9 which in a neutral position interconnects the motor forward and reverse drive lines 26, 27, the valves 7, 9 are mechanically coupled to a common adjusting means so that the throttle valve 7 is closed when the reversing valve 9 is in neutral, and the throttle valve 7 is opened simultaneously with the connection of the pump pressure line 4 with the motor forward or reverse drive line 26 or 27. The pump pressure line 4 is provided with a pressure limiting valve 8 discharging to the system sump 1. As shown in Fig. 2, the valves 7, 9 are housed in a block 11 mounted on the sump 1, with their longitudinal axes parallel. Valve 7 comprises a piston 18 slidable in a sleeve 12 having ports 16 communicating with the pump suction line 3. The sleeve 12 opens at one end into the sump 1 and at the other end into a chamber 14 connected by a line 15 to the sump 1, so that movement of the piston 18 in either direction from a central position closing the ports 16 connects the suction line 3 with the sump. A piston rod 40 of the piston 18 is pivoted at 41 to a lever 34 secured to a shaft 35, and springs 42 centre the piston 18 to its closed position. Valve 9 comprises a spool 28, 29 connected by a link 33 to the lever 34 and slidably supported by radial limbs 30 in a sleeve 13 having ports 24, 25 leading to the motor lines 26, 27 respectively, and ports 20a, 20b leading via a gallery 21 to the pump pressure line 4 (Fig. 3, not shown). With the spool in its central, neutral position, a land 19 partly covers ports 20a, 20b and lands 31, 32 are clear of the ends of sleeve 13 so that chamber 14, lines 26, 4, 27, and sump 1 are all interconnected by the valve. Movement of lever 34 clockwise connects line 3 to chamber 14, line 27, via port 25, to sump 1, and line 4, via ports 20a, 24 to line 26, while closing port 20b and the top of sleeve 13. Anticlockwise movement connects line 3 to sump 1, line 26, via port 24, to chamber 14, and line 4, via ports 20b, 25 to line 27, while closing port 20a and the bottom of sleeve 13. In a road vehicle, e.g. a street sweeper, shaft 35 is connected to a pedal (39) (Fig. 5, not shown) rocked forward or backward for forward or reverse drive respectively, with simultaneous throttle valve 7 control.