Patent GB-511035-A (GB)
Title: Improvements in brakes
IPC: F16D65/58
Filed: 1938-01-07
Abstract: 511,035. Adjusting brake shoes. BENDIX AVIATION CORPORATION. Jan. 7, 1938, No. 526. Convention date, Jan. 11, 1937. [Class 103 (i)] Adjustment of brake shoes or of the effective length of a pair of shoes is effected by a member that is adjusted relatively to a shoe by contact with the brake drum, expansion of which thus does not affect the adjustment. Fig. 1 shows a servo-shoe brake in which when the brake is applied by the cylinder 222 one of the shoes 212, 214, dependent upon the direction of drum rotation, engages the anchor 216 and the other shoe anchors through the first. The release position of the shoe 212 is determined by the engagement with a stop 224 of a pair of levers 226 pivoted at 228 on either side of the shoe and held in position relatively to the shoe by pawls 236, 237 and ratchet teeth 234. As wear of the friction lining occurs, the levers are moved relatively to the shoe by contact of lugs 229 on the levers with the drum and the return position of the shoe is thus adjusted. The provision of two pawls permits of a relatively fine adjustment. In the servo-shoe brake shown in Fig. 3 both the return position of the shoe 412 and the effective length of the shoes 412, 414 is adjusted so that no adjustment of the applying means is necessary. The shoe 412 is positioned by a lever 426 pivoted thereon and normally engaging a stop 424. The lever is held in adjusted position by engagement of a projection 436 thereon with a rotatable cam 434 on the shoe. When, due to wear, the lever is displaced by the drum contact 429, the cam is turned by a spring 435 to take up the clearance between the cam and the projection and during release a lever 450 pivoted at 452 on the shoe 412 and on which shoe 414 abuts at 454, is turned by engagement of a lever 440, pivoted on lever 426, with a stop 441 thus increasing the effective length of the two shoes. A spring urged cam 446 on shoe 412 holds lever 450 in adjusted position. In a modification, levers similar to levers 426, 450 are held in position by engagement of pawls thereon with a member secured to shoe 412. In Fig 4, levers 526, 540, 550 pivoted on shoe 512, have cam surfaces ' 527, 534 and 556 engaging respectively a stop 524, lever 527 and lever 540. Wear of the shoe 512 effects displacement of the lever 526 relatively to the shoe 512 by the drumcontact 529, permitting during release, rocking of the lever 540 by a spring 535 whereby the lever 550 is rocked by the projection 544 to increase the effective length of the shoes, the position of the shoe 512 also being adjusted. The Specification as open to inspection under Sect. 91 describes also the following :-In Fig. 1, (Cancelled, not shown) the lever 226 is replaced by a rod slidable in guides on the shoe and arranged at its ends to contact the drum and a stop, and held in adjusted position on the shoe by a ratchet and pawl. In Fig. 2 (Cancelled, not shown) the slidable rod instead of being normal to the drum is oblique thereto, to give a finer adjustment. The shoes are mounted on fixed pivots in this case. In Fig. 8 (Cancelled), each shoe such as 714 of a servo-shoe brake anchors on a stop 716 by a rod 726 slidable in guides 728, 731 on the shoe and adjustably held by a pawl 736. As the lining wears, the rod is moved by contact of the end 729 with the drum, to increase the effective length of the shoe. In Fig. 7 (Cancelled, not shown), each shoe of a servo-shoe brake anchors on a stop through a lever pivoted on the shoe and having a drum-contact. Adjustment of the lever on one shoe is effected by wear when the brake is applied with the opposite shoe anchored. In Fig. 9 (Cancelled), a cam 834 is connected to the shoe 812 by a spring 835 so as to move with the shoe but if the shoe movement exceeds the clearance between a fixed pin 824 and an oversized hole in the cam the shoe moves away from the cam which is then turned by the spring thus adjusting the shoe. In a modification, Fig. 11 (Cancelled, not shown), the cam is replaced by a lever having a cam face engaging the shoe. In Fig. 10 (Cancelled, not shown), a lever pivoted on the shoe has a slot engaging a fixed pin 924 whereby the lever and thus the shoe is adjusted when the shoe movement exceeds the clearance between the pin and one end of the slot, the lever being held in adjusted position by a friction pawl engaging a cam face on the lever. Fig. 12 (Cancelled) shows a servo-shoe brake with means for automatically adjusting the effective length of the shoes and whereby the force transmitted from the primary to the secondary shoe is reduced. A lever 1162 pivoted at 1160 is engaged respectively by extensions 1166, 1170 of the shoes 1114, 1112 and a lever 1174 pivoted on the lever 1162 is engaged by extensions 1178, 1182 of the shoes. The upper end of lever 1174 is normally held in contact with a cam 1134 pivoted on lever 1162, by a spring 1148 which tends also to turn the cam. When the brake is applied with clockwise rotation of the drum, the torque of the shoe 1114 is applied to the shoe 1112 through the lever 1162 at a reduced value. If wear of the lining occurs, clearance between a lug 1184 on the lever 1174 and the extension 1182 of shoe 1114 is taken up so that the lever is moved out of contact with the cam 1134 which then turns to adjust the length of the connection between the shoes. In a modification Fig. 14 (Cancelled, not shown), the adjustment for wear is effected by a link supported by a link on the shoe 1114 and connected to the lever 1174 and arranged to contact the drum so as to move this lever as wear occurs. Fig. 13, (Cancelled, not shown), shows a further modification in which levers corresponding to the levers 1162, 1174 are connected by pins and slots to the shoes and in which the cam corresponding to the cam 1134 is manually adjusted. This subject matter does not appear in the Specification as accepted.