Patent GB-805970-A (GB)
Title: Improvements in centrifugal clutches, in particular for automobile vehicles
IPC: F16D43/08
Filed: 1955-03-30
Abstract: 805,970. Friction clutches. GRAVINA, M. March 30, 1955 [Feb. 23, 1955], No. 9329/55. Class 80 (2). To provide engine push-start and stationary engine braking on a vehicle driven through a centrifugal main clutch, the said clutch is automatically engaged at zero engine speed by auxiliary means, such as springs 22, which are independent of both the driven portion of the clutch and the main centrifugal mechanism and can be rendered inoperative by first and second control means, the first of which is ineffective as long as the engine is not to be run but becomes effective in response to starting of the engine, as by auxiliary centrifugal means, or in preparation for starting the engine, as by actuating the ignition or start control, whilst the second control means is manually actuated at will. In Fig. 7 (not shown), only, the clutch is of the directly centrifugally engaged type, but in all other examples is of the Gravina indirect centrifugal type (Specification 586,910). In Fig. 1 an output clutch disc 5 is clamped to an input flywheel 1 by applying axial engaging force to a presser plate 2 by centrifugal masses 7 acting through a cam-plate 9, thrust bearing 10 and springs 12, and pivoted on a floating carrier 13 which, for centrifugal clutch engagement, is frictionally clutched to input 1 by a plate 15 loaded by springs 17, to drive the masses 7, and for clutch disengagement is held stationary by energizing an electromagnetic brake winding 18 which collapses the masses 7 and. permits springs 4 to release the main clutch. At rest and sub-idle engine speeds, auxiliary springs 22 act directly on the presserplate 2 to effect light clutch engagement at only sufficient strength to permit the engine to be turned by motion of the vehicle. When the engine starts, input-mounted auxiliary centrifugal masses 24 compress the auxiliary springs 22 to release the clutch, which is subsequently re-engaged at a higher speed by the main centrifugal masses 7. To permit free initial movement of the vehicle even though in gear, the main clutch-release brake-winding 18 can be energized to attract the clutch-brake disc 15, which, through lost-motion pins 23, compresses the auxiliary springs 22 independently of the auxiliary masses 24, thus releasing the main clutch. In operation such temporary energizing of the clutch-release winding is manually effected by the driver moving into a gear position the usual two-part yielding gear-shift lever 21, and retaining pressure on the lever to maintain clutch release until after the vehicle is in motion, whereupon the driver releases his pressure on the shift-lever, which breaks the release circuit and permits the clutch to engage by the auxiliary springs 22 to turn the engine. 19 is a series switch operated by the usual engine ignition switch. In Fig. 5, not shown, the pins 23 are attached to a separate collar movable by a manual lever or pedal for compressing the auxiliary springs 22 for clutch release independently of the main masses 7. The lever may be mounted on the gear-shift lever and act through a pneumatic servo. In Fig. 6, not shown, the pins 23 are secured to an armature plate attracted by a separate electromagnet normally energized for clutch release, but de-energized by a switch opened by operating the engine-start control, or opening the engine ignition switch. No auxiliary masses are provided, this being the only release control for the auxiliary springs 22. In the direct-acting centrifugal clutch, Fig. 7, not shown, the pins 23 are retractable by auxiliary masses such as 24, Fig. 1, and also by a separate electromagnet energized only by closure of a hand- or foot-operated switch.