Patent GB-474934-A (GB)
Title: Improvements in change-speed gears
IPC: F16H61/02
Filed: 1936-07-31
Abstract: 474,934. Variable - speed gearing. TENNANT, W. J. (Maybach-Motorenbau Ges.) July 31, 1936, No. 21313. [Class 80 (ii)] In a variable-speed gear having dog-clutches, the sliding members of which are connected in pairs, a retarding device common to certain clutch members and an accelerating device common to certain other clutch members are provided, these devices being controlled by members operated by the pairs of sliding clutch members to produce synchronization at each speed change. In the form shown in Fig. 1, the gear comprises three constant mesh gear pairs 1 ... 6, the gear 1 being fast on the driving shaft 13 and the gear 5 on the driven shaft 14. The lay-shaft comprises two sections 15, 16. The section 15 carries the gear 2 and the sliding clutch member 10, and the section 16 carries the gear 6 and the sliding clutch member 12. The gears 3, 4 are loose and carry clutch teeth 9<1> ... 12<1>. The driving shaft carries a slidable clutch member 9 and the driven shaft a clutch member 11. The sliding clutch members 9, 10 are interconnected by a rocking lever 7 and the members 11, 12 by a lever 8. It will be seen from the relative sizes of the gear-wheels that in the various gearchanges 9 will be moving faster than 9<1>, 10 slower than 10<1>, 11<1> slower than 11, and 12<1> faster than 12. To effect synchronization, the driving shaft 13 is retarded by a brake 58 or accelerated by opening the engine throttle valve 70. The brake 58 is operated directly by a servomotor 56, and the throttle 70 by a servomotor 63 acting through a bell-crank 66 and links 67, 69. The servomotors 56, 63 are operated by pressure-fluid, which passes from a reservoir 50 past a pair of valves 18, 19 connected to the clutch members 12, 10 respectively, and through conduits 53, 60 interrupted by an interlocking valve 77 so arranged that when pressure enters one of the conduits it is led by a branch 83 or 84 to one end of the valve to displace it laterally and exhaust the other conduit, so that only one servomotor at a time can be operated. Fig. 1 shows the parts in fourth gear position, when an overdrive is obtained through the gears 3, 4, 6, 5. Fig. 4 shows the valves in the third speed position, when direct drive is obtained through clutch members 9, 9<1> and 11, 11<1>. When the valve 18 moves to the left from the third speed to the fourth speed position, it moves quickly at first as the clutch 11, 11<1> comes out of engagement. It passes through a position in which the passage 60 is energized from the supply pipe 51 through space 39 in the valve 19, branched port 46, space 27 in valve 18, and port 44, but this energization does not last long enough to operate the accelerator motor 63. When the bevelled ends of the clutch members 12, 121 have come into engagement, the valve 18 slows up and its space 26 begins to connect. the branched port 46 to port 43 to energize the conduit 53 and operate the brake. The braking continues throughout that part of the engaging movement in which baulking is possible due to the chamfer of the teeth. The space 26 then connects the conduit 53 to exhaust through port 42, space 37 in valve 19, and port 48, and the engagement is completed without further braking. A similar effect occurs when the valve 19 is movedto the left. When either valve moves to the right, the motor 63 is energized to produce acceleration. In the change from second to third speed, the members 9, 9<1> and 11, 111 both have to be engaged. The valve 18 is thus moved to the right and the valve 19 to the left. During these movements both conduits 53, 60 are, therefore, energized, but owing to the fact that the interlocking valve 77 is urged to the right by a spring 78, this valve remains at first in the right-hand position and pressure is supplied to the brake-motor 56 alone until the clutch members 9, 9<1> have passed the baulking position. The conduit 53 is then exhausted as explained above, and the pressure in conduit 60 and branch 84 can now move valve 77 to the left to allow motor 63 to be operated to produce the acceleration necessary to complete the engagement of members 11, 11<1>. In a modification (not shown), the valves 18, 19 are arranged in separate casings and are acted on directly by gear-shifting servomotors. Further pairs of clutches with further control valves, and/or interlocking valves may be employed. The brake and accelerator motors may be actuated by engine or other suction. The retarding device may also be arranged to disengage the main clutch and brake that member of the clutch which is connected to the gear.