Patent GB-638748-A (GB)
Title: Improvements in power transmitting mechanism particularly for use as a motor vehicledifferentia l driving mechanism
IPC: F16H37/08
Filed: 1947-01-17
Abstract: 638,748. Differential gearing; change-speed gear. ALLIS-CHALMERS MANUFACTURING CO. Jan. 17, 1947, Nos. 1613 and 1614. Convention dates, Jan. 19, 1946, and Dec. 28, 1946. [Class 80 (ii)] A driving and steering mechanism for a motor vehicle comprises a main differential transmitting power to two relatively rotatable driving shafts, and an auxiliary differential having a 'steering power input, the gear ratios being such that the overall ratio between the steering input and a driving shaft, with the main planet cage stationary, is larger than unity, and the ratio between one output element of the auxiliary differential and its input element, with the other output element stationary, is less than unity. The engine of a track laying vehicle drives through a main clutch and a hydraulic coupling to a three speed and reverse gearbox 31 and thence through a spur planet differential to the track sprocket reduction gear shafts W.X., the planets A1 of the differential having superimposed a torque from a controllable reversing gear 103 driven through a shaft 22 from power take-off gearing between the main clutch and the fluid coupling. Change-speed gear. The shaft 43 driven from the fluid coupling has gears 45, 48 for high and second speeds fixed for rotation therewith and a low and reverse gear 56 slidable thereon. The gears 45, 48 are in constant mesh with gears 46, 49 rotatably mounted on the driven shaft 44, the gear 49 being in one-way clutch connection 53 with the shaft when the selector gear 54 is engaged with the outer race 52 of the one-way clutch, and being in rigid connection when the double clutch member 47 is clutched to the gear 49. The high speed is engaged by clutch 47 engaging the gear 46, and low speed by sliding gear 56 to engage with gear 54. Further axial movement of the gear 56 will engage it with the reverse countershaft 57. Reversing gearing. The reversing gear 103, Figs. 3 and 6, comprises a driving shaft 22, driven from the engine, having a driving hub 117 secured to an outer clutch drum 119 to which are splined the driving plates of two clutches 121, 122 with a pressure member 137 interposed. The driven plates of the two clutches are splined respectively to drums 127, 129 secured to bevel gears 123, 126 meshing with bevel pinions 124 mounted for rotation about a stationary spider 132. The gear 123 is splined to the end of a quill shaft 112 having rigid therewith a brake drum 157 and a bevel pinion 113 meshing with a bevel gear 99. Actuation of the shift collar 144 causes engagement of either of the clutches 121 or 122, for forward and reverse drive, through the levers 139 and the shift rails 138, the movement of the collar being effected by a steering control lever (not shown) which is interconnected with a lever 171 controlling a band brake 158. When the control lever is in the neutral position the band 158 is held in frictional engagement with the drum 157 by two springs 163, 166 which hold the ends 159, 161 against the cam 168 slidably mounted for rotation with the shaft 162. Movement of the control lever to engage one or other of the clutches, rotates the shaft 162, through the lever 171, and thus releases the brake 158, 157. Differential gearing. The drive from the change speed gear 31 passes from the shaft 44 through a bevel pinion 87 to the bevel gear 83 rigid with the spider Z of the differential, the spider being journalled in the bearing 69 supported by the gear casing 32, and having a service brake drum 84. The spider comprises two covers 61, 71 joined by a spacer 59 in which are journalled the co-axial sun gears B.C. rigid with the driven shafts W.X. and in which are also journalled three pairs of interengaging differential pinions Al, A2. The pinions A1 meshing with the sun gear B and pinions A2, and the pinions A2 meshing with the pinions A1 and the sun gear C to form a spur planet differential. Spur gears D are rigidly mounted on the spindles of the planet gears A1 and these spur gears mesh and support a spur gear E, integral with one end of a sleeve E mounted with clearance about the shaft X. A second gear E2 on the other end of the sleeve E meshes with a gear F1 of a countershaft F, carried on a spindle 91 rigid with the casing 32, the other gear F2 of the countershaft meshing with a gear G1 on a sleeve G. A gear G2 on the other end of the sleeve G meshes with one planet gear H1 of a pair H mounted on a spindle 97 in a planet cage Y rigid with the bevel gear 99. The other planet gear H2 meshes with a gear K rigid with the driven shaft X. There are three of each gear pair F, H and the sleeve gears E, G. are supported by the tooth contacts of the engaging gears at three points on their circumference. The gears E2 and K are made equal in pitch diameter to F1 and H2 respectively and the gears E2, F1, G and GI are greater in pitch diameter than the gears E1 F2 and G2 respectively so that the overall ratio of the gearing between the sleeve E and the shaft X when the bevel gear 99 is stationary is equal to unity ; this condition provides equal rotational speeds and directions of rotation of the shafts Y.X. Under these conditions, with the brake 158 engaged, the sleeve E is held stationary and thus the differential is locked to prevent overspeeding of one driven shaft X or Y should the resisting torque on that shaft decrease. When a second torque is applied to the planet pinions H by the reversing gear 103, this torque is transmitted by the gear train H, G, F, E, D to the planet pinions A1 of the differential, and through the action of the differential produces torques of opposite senses in the shafts W.X. If the vehicle is stationary, that is with the change speed gear 31 in neutral and the brake 88 applied, it will execute a pivot turn about its vertical centreline as the tracks will move at equal speeds in opposite directions, the direction of the turn being determined by the direction of the torque applied by the reversing gear 103. When the change speed gear 31 is applying a torque to the differential spider Z, the brake 88 being released, and the reversing gear 103 is applying a second torque to the pinions A1, these two torques will be superimposed by the differential and cause a difference in relative speeds of the shafts W.X. to provide turns of greater radius, the radius being dependant upon the relative speeds of the bevel gears 87 and 113. In a second embodiment the engine drives through a hydraulic torque converter to two aligned shafts, one providing a main drive through a two speed and reverse countershaft gear actuated by hydraulic clutches to the planet carrier of a differential gear, and the other providing a steering drive through a hydraulically controlled forward and reverse gear to a sun gear concentre but free to rotate independently of one of the driven shafts. A second sun gear is similarly located with respect to the other driven shaft and is fixed to a stationary part of the gear casing. The two sun gears mesh with planets meshing with a pair of annulus gears joined together for free relative rotation with respect to the remainder of the gear system. The plar.et gears are journalled on the sun gears of the bevel differential, for orbital movement, which sun gears are in driving connection with the driven shafts. Other modifications show equivalent differential and epicyclic trains to the first modification, but with the epicyclic trains external to the differential gear. Yet another modification shows the gear arrangement of the first modification with the two sun gears selectively braked or driven from a second torque shaft.