Patent GB-832615-A (GB)
Title: Improvements relating to control mechanisms for change speed gearing
IPC: F16H63/30
Filed: 1956-03-15
Abstract: 832,615. Change-speed control. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd., KIRK, W. A., KERSHAW, J. W. G., and FLEWELLEN, H. E. G. Aug. 10, 1956 [Aug. 11, 1955; March 15, 1956], Nos. 23142/55 and 8090/56. Class 80 (2). Gear change in a vehicle multi-speed box is effected by a shift finger 14, Fig. 1, in a gearbox 13 which is operated by a gear lever 11 through a longitudinally movable coupling shaft 12, which shaft includes at 15 a lostmotion connection which initiates a timed cycle of disengagement and re-engagement of a fluid-pressure operated clutch during the gearchange operation. The lost-motion connection 15 comprises, Fig. 2, a male part 15b sliding within a female part 15a and centred therein by a spring 27. A cam swell 43 on the part 15b is adapted on relative movement in either direction to part 15a to actuate a lever 41 with one-way catches 44a, 44b to open a pilot valve 36 controlling the escape of pressure fluid from a flexible hose 74 which is connected to a main control valve 46 for the clutch operating mechanism. The valve 46 (see Fig. 3), comprises a main valve member 54 controlling the supply of pressure fluid from an inlet port 48 past a valve seat 56 to an outlet port 58 coupled by a pipe 72 to the clutch operating motor (not shown). The valve member 54 is controlled by a piston 51 with a hollow stem 59 which is acted upon on its lower side by the inlet pressure in a chamber 47 and on its upper side by the inlet pressure through a choke orifice 52. The hollow stem 59 forms an exhaust passage from the outlet 58 to an outlet 63 and has on its lower end a tip 65 engageable with grooves 66, 67, 68 or 69 on the coupling shaft 12 where it passes through the body of the valve 46. In operation, with the gear lever 11 in neutral the pilot valve 36 is closed, the pressure above and below control piston 51 is equalized and a spring 70 holds the tip 65 of stem 59 in locking engagement with the shaft 12. To select and engage a gear the gear lever is moved laterally as may be required to transmit unimpeded rotation through the shaft 12 to the shift finger 14 and then moved forwards or backwards to effect longitudinal movement. The right-hand end of the shaft 12 is prevented from moving immediately because of the locking of the tip 65 in grooves 66-69 to the male part 15b of the connection 15 moves relatively to the female part 15a so that pilot valve 36 is operated. This valve releases the pressure through an outlet 73 and flexible pipe 74 from above the control piston 51 which thereupon rises to release the tip 65 from its groove and to seat the top of the stem 59 against the valve member 54 which simultaneously closes the outlet 58 from exhaust through the stem and opens it to fluid pressure from the inlet 48. The clutch is thereupon released and continued movement of the gear lever and shaft 12 is allowed to move the shift finger 14 to effect the desired movement of the selected gear member. The lost-motion connection 15 is centralized by its spring to close the pilot valve 36 which results in pressure building up above piston 51 through orifice 52 to move the piston and stem 59 downwards to close valve 54, open outlet 58 to exhaust for clutch re-engagement controlled by an orifice 64 and to re-engage tip 65 with another of the grooves 66-69 to lock the engaged gear. The grooves 66-69 may be provided to allow for more than one gear in either the forward or backward movement to the gear lever, by different amounts, one a single wide groove 68 may serve for two gear positions. During a change from one gear to another the cycle of clutch disengagement and re-engagement may occur twice if a pause is made in the neutral position as required by boxes of the sliding mesh type but for boxes of the syncromesh and epicyclic types the gear lever may be moved quickly from one position to another so that time for only one cycle of clutch operation is allowed.