Patent GB-598377-A (GB)
Title: Torque transmitting mechanism
IPC: F16D11/10
Filed: 1945-05-31
Abstract: 598,377. Claw clutches; change-speed gear. TIMKEN-DETROIT AXLE CO. May 31, 1945, No. 13716. Convention date, July 13, 1944. [Class 80 (ii)] In order to make it more difficult to obtain asynchronous engagement of a clawclutch or detent, for use in a countershaft or planetary two-speed vehicle-axle drive, the meshing teeth, e.g. 36, 38 and 37, 41, Fig. 4A, (double-clutch shown), have plain sharp-cornered unchamfered end-surfaces 36a, 38a, and 37a, 41a, which, prior to engagement, abut in a common radial or conical surface of revolution, and the circumferential tooth-clearance or back-lash 381 when engaged is very small (of the order of 0.002 to 0.030 inches), the design being such as to so correlate the backlash, the area of the tooth end-faces, the engaging pressure, and the mass of the clutchcollar, that, under engaging pressure, the tooth end-faces slide frictionally and silently over each other in either direction until the parts are synchronised, as by manipulating the engine-throttle, whereupon shockless engagement takes place. Dimensional and pressure data for this purpose are quoted. Preselected vacuum-operated shifts are executed by manipulation of the accelerator - pedal only, without use of the clutch, and the vehicle speedometer-drive ratio is also suitably changed by a mechanical or vacuum interconnection with the axle ratio-shift control. The two-speed axle shown in Fig. 1 comprises freely-mounted wheels 26, 27, which can be selectively clutched to a bevel-driven countershaft 22 by a double claw-clutch 34, described below, and are in constant mesh with wheels 28, 29, fast to the usual differential-carrier 13 from which project driven axle-shafts 11, 12. Apart from the fact that it comprises claw-clutch and detent teeth 226, 228 modified as described below, the direct-and-over-drive planetary axle shown in Fig. 14 is the same as that described in Specification 361,382, comprising a planetcarrier 195 secured to the usual driving bevel ring=gear 182; a ring-gear 202 secured to the usual driven differential spider 204, with its projecting axle-shafts 211, 212; and a freely - mounted reaction - sun 215 carrying a splined clutch-detent sleeve 220 for locking the sun to the carrier at 226 for direct-drive, or to the fixed casing at 228 for overdrive. In the countershaft form, Fig. 1, the double clutch comprises axially spaced sets of straight teeth 36, 37, Figs. 3, 4A, and 6A, in a collar 34 which slides on the driving countershaft 22, which has co-operating axially-spaced sets of teeth 31, 32. When the collar 34 is moved to the left, Fig. 4A, the collar-teeth 36 engage similar teeth 38 on the end of the freely-mounted low-speed pinion 26, and drive is transmitted, in the direction of the arrows, from the countershaft-teeth 31, through the collar-teeth 37 and 36 to the clutch-teeth 38 of the pinion. When moved to the right, the collar-teeth 36 occupy a gap between the shaft-teeth 31, 32, whilst the collar-teeth 37 engage the shaft-teeth 32 and also the teeth 41 on the end of the high-speed pinion 27 which latter is thus clutched to the shaft 22. The backlash in the low-speed clutching-teeth 36, 38 is very small (0.002 inches), whilst that between the high-speed clutching-teeth 37, 41 is greater (0.020 to 0.030 inches). In addition the teeth 36 are symmetrically 0.030 to 0.040 inches wider than the teeth 37, to facilitate preselective operation by ensuring that the collar- and shaft-teeth 36, 31 will co-operate positively to prevent disengagement in either direction until the torque-load is removed. Thus, in the lowspeed position, Fig. 4A, the clutch-collar has been loaded for rightward axial movement towards the high-speed position by operation of the preselector control described below, but even if the axial loading is sufficient to overcome drive-torque toothfriction, the butting engagement at 31a of the corners of the teeth 31, 36 positively prevents such movement until drive-torque is removed, as by release of the acceleratorpedal which thus causes the preselected shift to be executed. A similar action occurs at the opposite corners 31b of the teeth 36, 31, as shown in Fig. 6A to block the return leftward movement of the collar towards the low-speed from the high-speed position shown. In the form shown in Fig. 14 an equivalent positive release stop for the clutch detent teeth 226, 228 is provided by making all the teeth slightly T-shaped as shown in Fig. 20. The clutch-collar 34 is accurately located in each of its engaged positions by three radially spring-loaded balls 45, Fig. 3, which act on the bevelled ends of three of the collar-teeth 36, 37 to thrust the collar axially against the end-face of the appropriate clutched pinion 26 or 27. Thus, in each engaged position, T-shaped slippers 46, pivoted in an actuating-fork 48, can be arranged to be just out of axial contact with the sides of their groove 35 in the clutch-collar 34, to prevent rubbing. For this purpose adjustment of the engaged positions of the shift-fork 48 is provided by eccentric-headed stop-pins 57, Fig. 1, which, after being turned to adjust the limit positions of an arm 55 on the fork rockshaft 49, are force fitted in the fixed casing. The selector-clutch rockshaft 49 is actuated by engine-suction energising a single or double-acting diaphragm 62, Fig. 11, or piston, linked at 64 to the rockshaft, a loading-spring 67 being preferably provided in both cases to ensure automatic selection of low-speed if the power fails. In addition the rate of the spring 67 ensures that the load applied to disengage a clutch may be approximately four times that applied to engage a clutch. In Fig. 14, the rod 275 of the double-acting piston 277, which is not spring-biased, acts in both directions on the spherical end 254 of the clutchdetent shift-lever 250 through internal springs. The engine-suction is controlled by a simple piston-valve operated through a Bowden wire by a preselector-knob on the vehicle dashboard. The interconnected selector-control of a two-speed speedometer drive is operated either by a direct Bowden-wire connection 125, Fig. 1, with the selector-clutch rockshaft 49, which acts in both directions on the speedometer ratio-shift control through springs, or by a spring-biassed single-acting suction-operated diaphragm teed into the same line 68, Fig. 11, as that which operates the selector-clutch diaphragm 62. Specification 587,312 and U.S.A. Specifications 2,071,165 and 2,183,667 also are referred to. The Specification as open to inspection under Sect. 91 states also that the line generating the surfaces of revolution in which the tooth end-faces lie may be curved and refers to U.S.A. Specifications 1,719,188 and 1,891,678. This subjectmatter does not appear in the Specification as accepted.