Patent GB-338503-A (GB)
Title: Improvements in and relating to friction ratchet or detent mechanism, and brakes comprising the same
IPC: F16D41/00
Filed: 1929-07-16
Abstract: 338,503. Furness, J. A. July 16, 1929. Compensating for wear; force-transmitting mechanism; personal actuation; blocks and shoes acting on drums. -A device permitting relative movement between two members in one direction only comprises two eccentrically mounted discs or the like 17, 22 and spring 20 constraining one disc 22 to follow the other disc 17 when it is rotated in one direction, in this case anticlockwise, and thereby secure a degree of engagement between the two discs to prevent relative motion thereof under stresses tending to constrain the disc 17 to move in the reverse direction. This device is used to adjust brake mechanism automatically and in Fig. 3 the disc 17 is connected by a link 14 and pin and slot connection 15, 16 to the shoe 9 of an internal expanding brake. When the brake is released the pin 16 engages one end of the slot 15 and tends to move the disc 17 in the direction which is prevented by the engagement of the discs 22 which therefore act as a stop. When wear occurs, the pin 16 engages the other end of the slot 15, on operation of the brake, and moves the disc 17 which is held in its new position by the disc 22. The device is' shown arranged to adjust the position of a brake rod in which is provided a slot engaging a pin on the disc 17. In the modification shown in Fig. 11 for adjusting the release position of the cam lever 51 the discs 58. 62 are constrained to move in opposite directions bv spiral springs 61, 66. On wear occuring the pir and slot connection 55 moves the disc 58 clockwise leaving the disc 62 free to rotate clockwise to a new position. A pawl 68 engages teeth on the disc 58 should the springs 61, 66 break. Tn a further modification for adjusting brake linkage two levers are pivoted on the nivot of one of the eccentrically mounted discs and one of the levers operates, by means of a pawl and ratchet, the other lever which is provided with a pin engaging a slot in the disc. In some modifications the brake pedal is' shown operatively connected with the brake rodding by means of a pawl engaging a ratchet sector connected to the brakes and mounted on the same pivot as the pedal. A spring thus returns the pedal to the same position irrespective of the adjustment of the brakes. In this modification the return of the brake pedal and brakes may not synchronize and the brakes may seize and the pedal still return. To avoid this the arrangement shown in Figs. 3, 7, 8, and 9 is used. The brake lever 95, having a pull-off spring 96, is provided with a disc 97 eccentrically mounted on a pivot 98 and associated with a disc 99 eccentrically mounted on a pivot 100. This arrangement allows relative movement of the discs in the anticlockwise movement of the lever 95 only. Pivots 98, 100 are mounted in a plate 103 having a lever 104 connected to the brake and mounted on the pivot 98 which is fixed to the vehicle frame. Associated discs 108, 112 are also mounted on the pivots 98, 100 allowing relative movement when the disc 112 is moved in an anticlockwise direction. A pin 114 fixed to the disc 97 passes through a slot 113 in the disc 112 and a slot 115 in a link 116 connected to the disc 108. Movement of the lever 95 in the clockwise direction will move the plate 103 to apply the brakes by means of the engagement of the discs 97, 99 until a pin 118 on the disc 112 engages a stop 119 fixed on the pivot 98 and moves this disc and by means of the spring 110 the disc 108 in an anticlockwise direction. On return movement the lever 95 and the disc 97 move alone until the pin 114 moves in slots 113 and 115 until it engages the left hand end of the slot 113 and moves the plate 103 and the brake mechanism positively to return position by means of the link 116 and engagement of the discs 108, 112. Arms 120, 121 on the discs 99, 108 are provided for releasing the engagement of the discs should this be desired. This mechanism is shown modified to allow automatically for wear. A further disc is eccentrically pivoted on the pivot 98 having a pin and slot connection with the plate 103 and an arm connected by a spring with an arm on a disc eccentrically mounted on a pivot fixed on the vehicle frame. The pin and slot provides a stop for and allows movement of the plate 103 until wear takes place when the discs are moved to a new position. An arrangement for holding a brake lever in the " on " position comprises an eccentrically mounted segmental member 136 secured to the lever 133 co-operating with another eccentrically mounted segmental member 138. The member 138 is caused to follow the member 136 when the lever is moved clockwise to apply the brakes by means of the spring 140 and co-operation of these members prevents anticlockwise movement of the lever until the member 138 is released from the member 136 by a link 144 pivoted to an extension of the member 138 and having a pin and slot connection 142 with the lever, and operated by a lever 148 engaging a pin 147 on the link. The invention may be applied to epicyclic gears. The shoes 9, 10, Fig. 3, are expanded by a lever 34 pivoted to one shoe and engaging a slot in the other shoe.