Patent GB-344402-A (GB)
Title: Improvements in an automatic change speed gear
IPC: F16H61/02
Filed: 1929-09-03
Abstract: 344,402. Variable - speed gearing. TRAIRUP, M. K. DE, Adelaide House, King William Street, London. Sept. 3, 1929, No. 26722. [Class 80 (ii).] Clutches, friction and free-wheel,. ; shaft couplings.- An automatic variable-speed gear comprises a series of separate shafts 3, 4, 5 each corresponding to a speed and having freely mounted on them toothed wheels 13, 14, 17 respectively, clutched to their shafts by separate centrifugally operated friction clutches 20, 22, 23. Fixed to the shafts 4, 5 are toothed wheels 15, 18 and freely mounted on the driving shaft 3 is a compound wheel 19 attached to the aligned driven shaft 30. Clutches 21, 23 have long connecting links to their centrifugal weights k and are engaged centrifugally thereby through spring and are engaged centrifugally thereby through springs n which press together the driving friction plates p, whereas clutches 20, 22 have short pivot links and are disengaged centrifugally. Initially the clutch springs are so chosen that clutches 20, 22 are engaged giving first speed through train 13, 14, 15, 19. With increase in speed clutch 22 disengages and 23 engages giving second speed through train 13, 17, 18, 19. A connecting lever y makes these clutches interdependent. With further speed increase clutch 20 disengages and 21 engages yielding direct drive. These clutches are made interdependent by an axial connection and the centrifugal device for clutch 21 may be omitted. The shafts may be arranged at the cornets of a triangle and additional shafts may be journalled around the driving shaft 3. In the latter case, lever y is replaced by a selecting disc or cam drum to hold inoperative speeds out of engagement and each centrifugal clutch has three positions, out-in-out, such as have the clutches 21 and 23. The centrifugal weights k of the clutches are held inwards by radial tension springs passing centrally through a slotted or cranked part of the shaft and stops may limit outward travel of the weights. These springs may be weak and under considerable initial tension so that the weights will be returned at a much lower speed than that at which they fly outwards, thereby preventing undesired speed changes when the engine speed falls on changing up. To prevent at will undesired changing down such as when descending a hill with the throttle closed a stop may be provided on the interconnecting lever, disc or drum between the clutches. A device for permitting a free-wheel action to prevent changing down when the throttle is only momentarily closed is shown in the lower part of Fig. 4 and in Fig. 3. This comprises a spring-engaged plate friction clutch 11 engaged by rollers h<1> between the driving- plate 9 and a plate 10 which has a facial doublecam surface and a central recess wherein the roller rests, the engaging spring 12 being under no compression and the clutch being disengaged. For driving, the roller is moved out of the recess by a manual control to permit it to run up one side of the incline and engage the clutch. During overrunning with the roller in the recess, this manual control may be operated to permit the roller to run up the opposite incline whereby the engine may be used as a brake. The shoulder on the driving side of the recess may be dispensed with so that engagement is automatic in the driving direction. In a modification the free-wheel clutch is engaged by a screw-and-nut device and engagement of the friction surfaces takes place positively in both directions, the intervening space permitting a temporary overrun. This clutch is mounted on a parallel driving-shaft. An epicyclic reverse gear is shown in the lower part of Fig. 4 and comprises a slidable member e for locking a planet carrier 7 to a driving-shaft 1 giving solid forward drive, or to the casing giving reverse drive. In a simpler two-speed form of the change-speed gear, the normally fixed fulcrum pivots of the centrifugal clutches are made slidable on their shafts and are held in by a strong spring manually compressable to put both gears out of action.