Patent GB-190728546-A (GB)
Title: Improvements in Brakes
Inventor: FREUND EDWIN
Filed: 1907-12-28
Granted: 1908-12-28
Abstract: 28,546. Freund, E. Dec. 28. Brakes.-In brakes employing the drag of the brake shoe to increase the braking pressure, a movable yoke is interposed between the brake - operating members and the brake shoes, and is held in the position into which it is moved to bring the shoes into contact with the braking-surface, so as to take the strain or reaction on the parts due to the increased brake pressure when the drag takes place. The invention is shown applied to track brakes, but is applicable also to wheel brakes of vehicles. The brake block i, Fig. 1, and the yoke e are formed with corresponding inclined surfaces, and the yoke e is connected by a link f to a bell-crank lever f, f<1>, secured to a transverse shaft c. A ratchet p is also secured to the shaft, and is engaged by a pawl p<1>. When the block i is lowered on the track, the drag of the block causes it to slide relatively to the yoke, and the pawl p<1> prevents the shaft c from turning to release the brake. The drag of the block is limited by an adjustable stop a<3>. In another form, T-shaped rockers n<1>, n<3>, Fig. 2, are interposed between the yoke e and the shoe i. The yoke e is connected by a link f<1> to an arm f, keyed to the shaft c and carrying a pawl p<2>, gearing with the teeth of a ratchet-pulley p<1>, loose on the shaft c and surrounded by a brake band operated by a spring p<6> as descrioed in Specification No. 23,395, A.D. 1906. When the tension on the operating-cord q is relaxed, the spring p<6> tightens the brake band p<3> and holds the pulley stationary. The block i and yoke e are lowered, the pawl p<2> trailing over the ratchet teeth. The rockers n<1>, n<2> are tilted by the drag of the block i, and the reaction of the block is taken by the engagement of the pawl p<2> with the stationary ratchet. The drag of the block is limited by bell-crank levers a<3>, a<4>, which are connected by cords to the lower end of the lever q<1>, and also to an operating-cord q<3>. The cord q<3> is provided with a stop t<1> to limit the movement of the bell-crank levers. To release the brake, the operating-cord q<1> is pulled, freeing the pulley p<1>, and thus enabling the yoke to be raised by the cord f<2>, whereupon the block i is centred by the bell-crank levers a<3>, a<4>, which move into the position shown in dotted lines. In another arrangement, applied to electromagnetic brake shoes, the blocks are connected by a transverse beam k, Figs. 5 and 7, and a rocker n is placed between the yoke e and the beam k. The yoke e is connected at its corners by links g to arms f<1>, f<2>, the pair of arms f<1> being secured to the shaft c, while the pair of arms f are loose on the shaft d. The arms f<1>, f<2> are formed with toothed sectors gearing with one another. On the shafts c, d are fixed toothed sectors g<1>, g<2> provided with lugs c<4>, c<5> engaging, with play, between double lugs d<4>, d<5> carried by sectors d<1>, d<2> loose on the shafts c, d respectively. The sectors g<1>, g<2> are engaged by pawls h<1>, h<2>, and the sectors d<1>, d<2> by pawls i<1>, i<2>. The sectors g<1>, g<2> carry grooved pulleys c<7>, c<8>, to which are attached the cords c<1>, c<2> for lifting the blocks i off the track through the links e<1>, e<2>. On the shaft c is keyed a sector p gearing with a sector q carried by a transverse shaft h. At the opposite end of the shaft h are a number of pawls s engaging with ratchet teeth u formed on the face of a brake pulley t adapted to be held stationary by a brake strap (not shown). In operation, when the pulls c<1>, c<2> are released, and the pawls h<1>, h<2> are lifted by the cords k<1>, k<2>, the weight of the blocks causes them to be lowered on the track. The lugs c<4>, c<5> engage with the upper member of the double lugs d<4>, d<5> and carry round the sectors d<1>, d<2>, the pawls i<1>, i<2> trailing, if necessary, over the teeth. The sector p also turns the shaft h, and the pawl s slips over the teeth on the pulley t. The yoke e is held against upward movement by the engagement of the pawls s with the stationary pulley t, and any tilting of the rocker n causes the pressure of the blocks i on the rails to be increased. To release the brakes, the cords c<1>, c<2> are pulled to raise the blocks off the track, and the distance of this movement is limited by the amount of play of the lugs c<4>, c<5> between the double lugs d<4>, d<5>. Any wearin the blocks is automatically compensated for by the movement of the pawls i<1>, i<2> over one tooth of the sectors d<1>, d<2>, during the application of the brake. In order to limit the drag of the brake shoes during application, a lever x engaging in a slot in the brake beam, is keyed to the shaft d, and is provided with an extension y having stepped teeth adapted to be engaged by a spring bolt z. The operating-cords k<1>, k<2> for lifting the pawls h<1>, h<2> to allow the brake to go on, are so interconnected with the cord attached to the bolt z that the bolt is withdrawn one step before the pawls are lifted. If greater brake pressure is required, the bolt z may be with drawn farther. In another arrangement, instead of a central rocker, as described, a rocker at each end of the beam is used, These rockers are inclined upwardly towards one another and operate to prevent lateral movement of the brake beam ; for lateral movement to one side causes the rocker on that side to become more vertical, thereby applying more pressure to the beam and returning it to its central position.