Hydraulically operated hand brake - service brake system for railway cars

Claim 1

A fluid operated brake system for a railway car comprising a. two sets 1, 1a of hydraulic brake cylinders 2 having separate actuating circuits 28, 28a and common locking and unlocking circuits 7, 8, 8a and 9, 11, 11a; b. a hydraulic hand brake control unit 3 including a reservoir 14 and manually operated means 15, 16 for withdrawing fluid from the reservoir and delivering it under pressure selectively to either one of two control lines 12, 13 while permitting return flow from the remaining line to the reservoir; c. the first control line 12 being connected with the locking circuit 7, 8, 8a, and the second control line 13 being connected with the unlocking circuit 9, 11, 11a; d. a pair of hydraulic translating units 6, 6a each of which includes a cylinder 29 or 29a containing opposed working chambers 32, 33 or 32a, 33a separated by a reciprocating piston 31 or 31a, and by-pass means 34, 35 or 34a, 35a which interconnects said chambers and allows flow only from the first 32 or 32a to the second 33 or 33a, e. the first working chambers 32, 32a of the translating units being connected with the first control line 12, and the second working chambers 33, 33a of the units being connected, respectively, with the actuating circuits 28, 28a; f. service brake apparatus including means 4 for producing a pneumatic command signal of selected magnitude, and a pair of air-to-hydraulic boosters 5, 5a connected, respectively, with the actuating circuits 28, 28a and serving to develop in those circuits hydraulic pressures proportional to said pneumatic command signal; g. each booster being of the double-acting slack-compensating type, the first 5 serving to transfer fluid between one actuating circuit 28 and the reservoir 14 of said control unit 3 and the other serving to transfer fluid between the other actuating circuit 28a and a separate reservoir 14a; and h. fluid transfer means 58, 59, 59a interconnecting the two reservoirs 14, 14a and serving automatically to allow flow between them as needed to equalize their fluid levels but to interrupt flow from either when the fluid level therein decreases to a predetermined minimum elevation 61.