Patent GB-785915-A (GB)
Title: Improvements in and relating to an automatic control device for a gear box
IPC: F16H61/02
Filed: 1956-05-14
Abstract: 785,915. Change-speed gearing. COMPAGNIE DE PONT-A-MOUSSON. May 14, 1956 [May 16, 1955], No. 14890/56. Class 80 (2). Automatic control means for epicyclic fourspeed and reverse gearing A driven from an engine M through an hydraulic coupling C and operated by pressure-fluid servomotors V1, V2, V3, V4 for forward and VR for reverse speeds, comprises a spring-loaded pilot valve 45 controlled by fluid supplied by a pipe 29 from a pump E via an engine-driven centrifugal governor valve 97 at a pressure dependant on the engine speed, and a distributer valve 15 selectively connecting the servomotors V1, V2, V3, V4, VR through pipes 7, 8, 9, 10, 11 to exhaust 12 or to a pipe 3 leading from the pump E, the valve 15 being moved during forward drive by three pressure-fluid servomotors W1, W2, W3 supplied through pipes 42, 43, 44 from the pump E via pipes 31, 32 and the valve 45, the servo W1 acting through a pawl 58 co-operating with ratchet grooves 27 on valve 15 to move the latter to the left for successive single-step upshifts, the servo W2 acting through a pawl 58a co-operating with ratchet grooves 28 on valve 15 to move the latter to the right for successive single-step downshifts, and the servo W3 acting through a one-way connection 69a on a fork 24 to move valve 15 to the right for downshift direct from fourth or third speed to first speed. In the neutral position of valve 15, which is one step to the right of the position shown in Fig. 1, the servos V1, V2, V3, V4, VR are all connected to exhaust 12. From this position, valve 15 is moved by a manual knob 25 acting on the fork 24, either further to the right to reverse position, in which servo VR is connected to pipe 3 and the servos W1, W2, W3 are ineffective, or leftwards to the first-speed position shown in Fig. 1 in which servo V1 is connected to pipe 3. With the engine idling, valve 45 is in its extreme leftwards position, in which pipe 3 is connected to exhaust 37 through a branch 41, the pressure.in pipes 29, 31, 32 being prevented from falling below a minimum value by a check valve 3a. As the engine is accelerated, valve 45 moves to the position shown in Fig. 1 when the pressure in pipe 29 reaches a value p2, closing the pipe 41, so that pressure builds up in pipe 3 and the vehicle moves off in first speed. On further acceleration, pressure in pipe 29 reaches a value p3 and valve 45 moves further to the right, connecting pipe 42 to pipe 31. Servo W1 is thus energized and moves to the left, moving valve 15 one step to the left to exhaust servo V1 and energize servo V2, so establishing second speed. Engine M consequently slows down, pressure in pipe 29 drops and valve 45 returns to the Fig. 1 position in which servo W1 is exhausted at 38 and moves back to the right, valve 15 being held by a ball catch 21a. When pressure in 29 again reaches p3; change to third speed is established, and so on. Similarly, if on deceleration the pressure in pipe 29 drops below p2 to p1, valve 45 moves left, causing servo W2 to be energized and successive downshifts are established. If, however, violent deceleration causes the pressure to drop below p1, valve 45 moves to its extreme leftwards position in which pipe 44 is connected to pipe 32, causing servo W3 to be energized to shift valve direct to first-speed position and pipe 3 to be exhausted at 37 so as to enable the engine to idle. A cock 33 may be closed to render servos W1, W2, W3 inoperative and allow manual speed changing by the knob 25. The single valve 45 may be replaced by a pair of parallel spring-loaded valves both subjected to the pressure in pipe 29. An additional spring-loaded valve 111, Fig. 10, having a lost-motion connection 115, 116 to the accelerator pedal 118, may be inserted in pipes 42, 43. During normal travel of the vehicle, valve 111 occupies its leftwards position, in which pipes 42, 43 connect with pipes 42a, 43a leading to servos W1, W2. If, however, accelerator 118 is released, valve 111 is moved to the right to the position shown, in which both pipes 42, 43 are connected to pipe 43a and pipe 42a is closed, so that if the speed increases the gear changes down.