Patent GB-257701-A (GB)
Title: Improvements in or relating to one way clutches
Filed: 1925-06-27
Abstract: 257,701. Carling, W. T. June 27, 1925. Clutches, ratchet.-In freewheel clutches for use in variable-speed and other constant-mesh gearing on motor-vehicles, an element normally rotating with one clutch member is, to a limited extent, angularly displaced and replaced by friction with the other clutch member accordingly as one or other member is running faster, and when so displaced prevents engagement of the clutch, means being provided for manually holding the clutch in the disengaged condition. Pawls 4, carried in pockets 1<b> in an enlargement 1<a> of the driving-shaft 1, coact both with ratchet teeth 2b in the hub 2<a> of a loose driven wheel 2 and with like teeth in a mask 3 having rotational freedom limited by the engagement of a lug 2<c> on the wheel with the ends of a gap 3b in the mask. The pawl pivots 4<a> are retained by channels 5<b> in sleeves 5, 5<a> secured to the shaft 1, the mask 3 being displaced by friction with the sleeve 5<a> so that it holds the pawls out of action when the wheel 2 overruns. The friction between the parts 3, 5a may be augmented by a spring or pad. The part of each pawl nose engaging the mask is bevelled to facilitate re-engagement. As applied to constant-mesh variable-speed gearing, the gear-lever operates, for each gear, a collar 6 provided with a nose 6a entering the gap 3<b> and having a notch 6b to receive a projection 2d on the lug 2<c>. When the lowest gear is engaged, the collars 6 of higher-ratio gear are in the position shown in Fig. 3. To change to a higher gear, the engine ;s slowed down, for instance, by automatically reducing the fuel supply during the first movement of the lever, as described in Specification 234,238, and spring-pressure is applied to the collar 6 of the selected gear. While the shaft 1 is still running faster than the gear 2, the projection 2<d> engages the notch 6b, preventing withdrawal, but as soon as the gear 2 overruns, the lug 2<c> moves to the position shown in Fig. 3, the collar 6 is withdrawn, and, on speeding up the shaft 1, the mask 3 moves to the position shown in Fig. 1, permitting engagement of the clutch without shock. Similar procedure is adopted in changing down. The clutch may be used also in the direct drive. In a modification, a spring-pressed axially-slidable driving-member, having facial ratchet teeth, engages ratchet teeth concentrically disposed on the gear-wheel and mask, which is of cylindrical form and frictionally contacts with the driving- member. The driving-faces of the ratchet teeth are inclined to facilitate engagement. The invention may, as shown in Fig. 15, be applied to the control of the epicyclic gear described in Specifictaion 194,152, wherein one-way drive depends on the irreversibility of a worm-gear in the train. The tapered notch 2b in the hub of the " unlocking " sun-gear 2 has, in the position of the parts shown, sufficient play on the driving-key 1<a> to cause the worm to lock, but, on taking up the play by a tapered nose 6<a> on the collar 6, the worm is freed. Withdrawal of the nose 6<a> while the driving-shaft 1 is turning faster than the planet housing 3 is prevented by engagement of a projection 6b with a recess 2<c>, the sun-wheel 2 being retarded by friction with the hub 3a of the housing 3. The Provisional Specification describes a form wherein the lug is carried by the mask and engages a slot in the driven member, which is secured to a shaft.