Patent GB-534470-A (GB)
Title: Improvements in coupling means in gearing having helical-tooth wheels
IPC: F16H3/12
Filed: 1939-08-19
Abstract: 534,470. Clutches ; variable speed and reversing gears. SINCLAIR, H., and CLERK, R. C. Aug. 19, 1939, Nos. 23998/39 and 10765/40. [Class 80 (ii)] In a positive clutch comprising a first member, a second member rotatable with respect to the first member, an intermediate member in driving connection with the second member and slidable under the action of torque into and out of meshing engagement with the first member, and a subsidiary ratchet drive between the first and intermediate members to synchronise them to allow them to engage without shock, the intermediate member is provided with exterior helical teeth co-operating with helical teeth on one of the other members to effect the sliding movement of the intermediate member. Figs. 1, 2 and 5, show the application of such clutches to a marine reversing gear. A shaft 10 normally driven in the direction shown has fixed to it a first member 11 having double helical teeth 12, the left half of which cooperates with internal teeth 15 on an intermediate member 13 rotatable and slidable on the shaft 10 and having left hand helical teeth meshing with right hand helical teeth on a gear 21 on the driven propeller shaft 22. A pawl 16 pivoted to the side of the gear 11 co-operates with the teeth 15 when the clutch is disengaged. The right half of the teeth 12 similarly cooperate with teeth 19 on a gear 17 having right hand helical teeth meshing with left hand helical teeth on a gear 23 on a shaft 24 geared to the wheel 21 to drive the shaft 22 in the reverse direction. A pawl 20 on the gear 11 co-operates with the teeth 19. The clutches are held in engagement by sliding thrust blocks 27, 27R actuated by pivoted wedge blocks 29, 29R which are connected together by linkage 38, 38R, 34 and actuated by the gear control lever 40, Fig. 5. which is fixed to the shaft 33. The locking lever 44 of the lever 40 is connected to a piston valve 60, which, whenever the lever 40 is unlocked, admits pressure fluid to a cylinder 57 to cause application of brake shoes 50 to a brake drum 46 on the driving shaft 10 to bring the shaft to rest and thereafter to turn the drum against the action of a spring 54 to give a short reversing movement to the shaft 10, this being permitted by the employment of a hydraulic coupling between the engine and the shaft 10. When the lever 40 is in neutral position, both clutches are disengaged and the blocks 29, 29R are in such position that the pawls 16, 20 ratchet idly over the teeth 15, 19. To put in forward gear, the lever 44 is actuated to release lever 40 this action causing the shaft 10 to be reversed. The pawls 16, 20 then engage a tooth 15, 19 to turn the gears 13, 17 at the same speed as the gear 11 and the reaction of the helical teeth on the gears 13, 21, and 17, 23 assisted by that of the teeth 15, 19 on the pawls 16, 20 moves both gears 13, 17 into mesh with the gear 11 without shock. Further reverse movement of the shaft 10 is now prevented. The lever 40 is now moved to the forward position to move the blocks 29, 29R to the fully operative and fully inoperative positions respectively and the lever 44 is moved to locking position This allows the cylinder 57 to exhaust, the brake is released and the shaft 10 again rotates in the forward direction. The reaction of the teeth of the gears 17, 23 causes the withdrawal of the gear 17 from the gear 11 into the position shown in Fig. 1 in which the pawl 20 is clear of the teeth 19. In changing from forward to reverse the wedge surface 30 on the block 29R moves the gear 17 sufficiently to bring the teeth 19 into mesh with the pawl 20. The back turning of the shaft 10 maintains the teeth 15 and 12 in engagement and brings the teeth 17 and 12 into engagement. The blocks 27, 27R are then moved into the fully inoperative and operative positions respectively and, upon locking of the lever 40, the gear 13 slides out of mesh with the gear 11. Fig. 7 shows a two speed gear embodying the clutch and comprising low and high speed gear wheels 92. 93 having right hand helical teeth meshing with left hand'helical teeth on gear wheels 94, 95 fixed to the driven shaft 91. The wheels 92, 93 are rotatable and slidable on the driving shaft 90 and are connected for simultaneous sliding movement by a flange 104. A helical gear 98 fixed to the shaft 90 co-operates with internal teeth 101. 96 on the wheels 92, 93 and is provided with pawls 103, 100 also co-operating with the teeth 101, 96. Thrust blocks 105, 106 held by locking blocks 107, 108 are also provided. The blocks 107, 108 are vertically slidable and are urged to locking position behind the blocks 105. 106 by spring pressed arms 116, 117 pivoted on a shaft 118 to which is fixed a control lever and a two armed lever having at each end a pin 121 engaging in a slot in the adjacent arm 116, 117. To put the mechanism into low gear from the position shown, the shaft 118 is turned to allow the block 107 to be pressed by its spring arm 116 into contact with the edge of the block 105 and to lower the other block 107 or 108 into the inoperative position. Upon rotating the shaft 90 in the direction shown, the pawl 103 engages a tooth 101 and the gears 92, 98 engage cleanly under the reaction of the helical teeth. The arm 116 then raises the block 107 to lock the thrust block 105. In this position the pawl 100 is clear of the teeth 96. To change to high gear. the shaft 118 is turned to withdraw the block 107 and to move the block 108 into engagement with the block 106. The shaft 90 is now retarded and the inertia of the load causes the wheel 92 to overrun the shaft 90 so that it moves to the left under the reaction of the helical teeth. carrying the wheel 93 with it until the teeth 96 ride over the pawl 100. When the speed of the shaft 90 is less than that of the gear 93, the pawl 100 engages a tooth 96 and the wheels 93. 92 move to the left under the reaction of the helical teeth until the teeth 96 mesh with the gear 98. The block 108 then moves upward into locking position. Fig. 10 shows a four speed gear for driving a shaft 140 in either direction and suitable as a locomotive gear. The shaft 130 is driven by an internal combustion engine through a hydraulic coupling and has fixed to it a first speed driving wheel P1 second and third speed driving wheels P2, P3 are fixed to sleeves 149, 162 rotatable and slidable on the shaft 130 and provided with toothed flanges 150. 163 provided with clutch teeth 151, 164 and the sleeves are rotatable in members 156, 172 having teeth 158, 175 cooperating with teeth 159, 174 on members fixed to the gear casing. The members 156, 172 are connected by links to arms on a rock shaft actuated by the gear changing lever and the arrangement of the teeth 158, 159. 174 and 175 is such that in first gear the teeth mesh together as shown, in second gear the teeth 174, 175 are still in mesh but the member 156 is moved to the right so that the ends of the teeth 158 engage the ends of the teeth 159, and in third and fourth gear, both members 156. 172 are moved to the right so that the ends of the sets of teeth engage. The fourth speed gear P4 is free on a sleeve 169 splined to the shaft 130 and this sleeve and the gear P1 have internal clutch teeth 145, 167, to co-operate with the clutch teeth 164, 151. Synchronizing pawls 152, 153. 165, 166 are pivoted to the sides of the flanges 151, 164 and co-operate with the teeth 145, 167. The gears P1 .... P4. have helical teeth as shown and mesh with secondary gears S1 ... S4. Gears S2, S3 and S4 are fixed to a shaft 134 and the gear S1 is slidable and rotatable on the shaft and has a flange 146 provided with clutch teeth 147 for co-operation with internal clutch teeth 161 on the gear S2. A synchronizing' pawl 148 is mounted on the side of the flange 146 to cooperate with the teeth 161. A slidable ganging bar 196 has an arm 197 engaging in a groove in the member 156. an arm 199 for operative engagement with a flange 200 on the member 172 and an arm 201 projecting down to one side of the flange 146. The gear S3 meshes directly with a loose gear 190 on a shaft 137, the gear S4 drives through an idle gear, a gear 193 loose on the shaft 137 and a slidable clutch 194 connects the gears 190, 193 for direct or reverse drive of the shaft 137 which is connected by bevel gearing to the shaft 140 driving the locomotive. The gear P4 is rigid with the casing 176 of a normally open friction clutch 178 which may be closed by fluid pressure controlled by the lever which controls the speed of the engine. With the engine idling, the torque on the shaft in direction of the arrow shown tends to rotate the wheel P1. As the wheel S2 is held from rotating by the pawl 148 this wheel slides to the left under the effect of reaction on the helical teeth and the clutch teeth 147 mesh cleanly with the teeth 161. The engine is now accelerated and drive is effected through wheels P1, S1 S2 and S3 or S4 according to the position of the clutch 194. As the shaft 130 is rotating faster than the wheels P2, P3 these wheels are moved to the left by the reaction of their helical teeth and the pawls 152, 166 are clear of the teeth 145, 167. To change to second speed, the engine control lever is moved into position to reduce the engine speed and to close the clutch 178 and the gear lever is urged by the operator towards second position. As speed of shaft 130 falls below that of shaft 134, the reaction of the teeth of wheels P1, Sl moves S1 to the right disconnecting its clutch teeth and. by engagement of flange 146 with arm 201 moving ganging bar 196 to the right to disconnect the teeth 158, 159 and to bring pawl 152 into the path of the teeth 145 When the speed of the shaft 130 falls below that of the wheel P2 this wheel moves to the right until the pawl 153 is brought into the path of the teeth 145. This movement of the wheel P2 causes the bar 196 to move P3 to the right until the pawl 166 is in the path of the teeth 167. The