Patent GB-602323-A (GB)
Title: Improvements in or relating to variable ratio power transmission mechanism
IPC: F16H61/02
Filed: 1944-12-29
Abstract: 602,323. Change-speed gearing. HOBBS, H. F. Dec. 29, 1944, No. 26104. [Class 80 (ii)] Relates to change-speed gearing of the kind in which, in some ratios, an epicyclic gear 30, 31, 32 is used to distribute the drive differentially from a driving shaft 10 to an aligned driven shaft 34 simultaneously through two paths of different ratio, and including two selectively operable nested friction disc-clutches 25, 26, one, 26, of which drives one side-wheel 32 of the epicyclic gear, which drives the driven shaft 34 through change-speed countershaft gearing 38, and the other, 25, of which drives the planet-carrier 30 which distributes the drive differentially between the one side-wheel 32 and the other side-wheel 31, which is secured direct to the driven shaft 34. According to this invention, both the disc clutches 25, 26, which are hydraulically actuated, can also be engaged simultaneously to lock the epicyclic gear for direct-drive. The countershaft path provides two forward ratios between the sidewheel 32 and the driven shaft 34 via wheels 43, 40, 42, 44 or 43, 40, 41, 45, the latter being introduced by dog-clutching a sliding splined wheel 44 synchronously with a loose wheel 45. These two ratios are effective alone, using the disc-clutch 26 and also differentially with direct-drive, using the disc-clutch 25, providing four reduced ratios in addition to direct-drive using both clutches together. A sliding idler 46 provides a single reverse. In addition to the single rear housing-bearing 36, the driven shaft 34 is supported only by the usual clutch pilot-bearing 35. The disc-clutch '25 may be of greater diameter than 26 to compensate for its greater torque load in direct-drive. Striker forks for the wheels 44, 46 are operated mechanically through pins, e.g. 55, Fig. 3, by a rotary cam-selector 52, one end 51 of which has ports coacting with a surrounding housing 68 to form a distributer-valve supplying pressure-oil selectively to and from spaces behind flexible diaphragms 13, 14 operating the disc-clutches 25, 26. Upshifts involving engagement and disengagement of the dogclutch 44, 45 may be facilitated by temporarily engaging both disc clutches 25, 26 together, to unload and thus permit disengagement of the sliding gear or clutch teeth, and also to synchronize the dog-clutch prior to engagement, as described in Specification 602,319. Alternatively, as described in Specification 603,316, the ratio involving engagement of the dogclutch may be made equal or nearly so, to what would be the next lower ratio. The synchronizing-ring 75 may then be omitted. Where both clutches are temporarily engaged for this purpose, the cam-selector 52 may have a lost-motion connection with the part 51 and control the oil-supply suitably for engaging both clutches in the upshift direction only. To provide a free-wheeling effect at low speeds only, the pressure-supply to and/or exhaust from the friction clutches is controlled by a separate valve, which is spring-closed by release of the vehicle accelerator-pedal to exhaust both clutches 25, 26, and the pressuresupply is speed-responsive and applies a friction grip to the valve so as to render the spring ineffective to close the valve above a predetermined speed. The valve may also be closed by applying the vehicle hand-brake. An additional small pedal may be provided in place of the usual vehicle clutch-pedal so as to permit closing of the valve only when the small pedal is depressed. A pressure-duct is provided for lubrication and the rotating disc-clutch housing carries blades 90 for picking up and distributing oil which collects in a surrounding fixed channel 91. Specification 549,988 also is referred to.