Patent GB-535131-A (GB)
Title: Improvements in or relating to liquid pressure braking systems
IPC: F16D65/22
Filed: 1939-06-07
Abstract: 535,131. Hydraulic brakes. CLEVELAND, F. J. (Bendix Aviation Corporation). June 7, 1939, No. 16722. [A Specification was laid open to inspection under Sect. 91 of the Acts, Dec. 11, 1939.] [Class 103 (i)] Improvements in hydraulic cylinders, for internal expanding brakes, of the kind comprising a pair of pistons comprise (1) a stop device in the cylinder bore which serves as an anchorage abutment for the shoes and (2) the provision of a restricted passage for the liquid between compartments of the cylinder to cushion to return movement of one of the pistons in the case of a self-energizing type of brake. Fig. 4 shows a brake of this type comprising a pair of shoes, 712, 714 connected together at the lower ends by a floating adjustable screw-device. The upper shoe ends are engaged by pistons 734, 736 which normally abut on a stop ring 744 within the cylinders. A partition provided with a restricted port 762 is disposed between the ring and one of the pistons. Pressure supply and bleed ports are disposed at 766, 764 respectively. In addition to the release spring 736 connected to both shoes an unbalancing spring 770 may be provided for the shoe 714. If the brake is applied with the drum rotating in the normal direction indicated by the arrow only the piston 734 is displaced, the shoe 712 anchoring on the shoe 714 which in turn anchors through the piston 736 against the stop ring 744. If however the drum is turning in the opposite direction, the piston with the end of shoe 712 initially leaves the ring 744 as before-but as soon as the shoes engage the drum this piston returns to the ring and the cushioning action due to the forcing of the liquid through the port 762 prevents objectionable click and shock. The shoe 712 thus anchors against the ring and the piston 736 and corresponding end of the shoe 714 are displaced outwardly. The stop for the shoes instead of being disposed within the cylinder may be arranged for instance above the cylinder. In Fig. 3, the stop is formed by an integral partition 644 and the restricted passage 662 in the cylinder wall, the inlet and bleed ports being at 666, 664. A brake is also shown in which two cylinders are provided disposed respectively between the upper and lower ends of a pair of shoes so that each shoe encloses at one end or the other on a stop in the cylinder bore, according to the direction of drum rotation. The restricted passage is not provided in this case. The Specification as open to inspection under Sect. 91 comprises also the following subject matter:-A brake system for a mine car comprises a master cylinder and an operating lever therefor mounted on an end wall of the vehicle the lever being arranged on the outer side of the wall, The master cylinder is connected to a pair of brake cylinders disposed one at each side of the vehicle and each between a pair of wheels, brake blocks for which are respectively connected by push rods to the two pistons of the cylinders. The pistons have inwardly extending axial projections which normally abut on a perforated plate within the cylinder to limit the inward movement of the piston. The master cylinder may extend vertically into a reservoir within which is a crank arm for operating the piston. Lubrication of the piston is effected by the provision of an annular groove therein which normally communicates with the reservoir by radial grooves in the upper end of the cylinder which projects into the reservoir. A passage leading from the lower end, of the cylinder to the reservoir contains a non-return valve which may open to permit flow from the reservoir to the cylinder during the return stroke of the piston. In the horizontal master cylinder shown in Fig. 7 (Cancelled) the piston is adapted to yield to accommodate expansion and contraction of the liquid when the brake is applied, the operating lever for the piston rod being held in applied position by retaining means. For this purpose the piston rod comprises telescopic parts 151, 124 connected by a pin and slot 132 and urged apart by a pre-compressed spring 128 which yields only slightly when the brake is applied. The piston rod includes a third part 126 slidable with respect to part 124 and adjustable by turning a nut 140 which screws on part 126, relative rotation of the two parts being prevented by a pin 136. A non-return valve 186 permits flow from the reservoir 148 to the cylinder during the return stroke of the piston. The piston of the master cylinder shown in Fig. 10 (Cancelled) comprises two relatively slidable parts 470, 452, the part 470 carrying a valve 474 which normally opens a passage 466, 468 between the cylinder and the reservoir 426 but closes it upon initial downward movement of the piston effected by the arm 484 which is (connected by link 480 to the part 470. The relative movement of the piston parts is limited by a pin and slot 476. This master cylinder is shown as mounted on a motor car, the reservoir 426 being connected by pipe 432a to a supply tank. This subject-matter does not appear in the Specification as accepted.