Patent GB-982477-A (GB)
Title: Improvements in railway vehicle vacuum brake apparatus
Inventor: LARSSON INGMAR VALENTIN
IPC: B60T13/46
Filed: 1963-10-25
Abstract: 982,477. Vacuum brakes for rail vehicles. SVENSKA AKTIEBOLAGET BROMSREGULATOR. Oct. 25, 1963, No. 42119/63. Heading F2F. In vacuum braking apparatus for rail vehicles of the kind in which " empty " and " load " brake cylinders of the two-chamber vacuumsuspended type are provided, the lower chamber of the " empty " cylinder being responsive to rise of pressure in a brake pipe at all times for applying a brake and the lower chamber of the " load " cylinder being connected to the brake pipe via a valve operated by a load-responsive servomotor so that it acts as a one-way valve isolating the chamber from rising pressure in the brake pipe under light load conditions and is permanently open under heavy load conditions of the vehicle so that in these conditions both cylinders apply the brake, a second servomotor is provided which is controlled conjointly with the first servomotor to open a valve connection between the upper and lower chambers of the " load cylinder when the valve is in the position wherein the lower chamber is isolated from rising pressure in the brake pipe. As shown, an admission valve 3 connects brake pipe 1 directly to the lower chamber of " empty " cylinder 2 and via first servomotor 6, release valve 7, second servomotor 8 and intermediate pipe connections 4 to the lower chamber of " load " cylinder 5. The upper chamber of each cylinder is connected to the lower chamber via a one-way valve 11, so that vacuum can be retained in the upper chamber and the brake applied by raising the pressure in the train pipe. Such pressure rise is communicated direct to the lower chamber of cylinder 2, and via a controllable one-way valve 15 and chamber 14 of servomotor 6, and chambers 17, 20 of valve 7 and servomotor 8 to the lower chamber of cylinder 5. The valve 15 has a lostmotion connection with a diaphragm controlled by the pressure in a control chamber 12 which, together with that in the control chamber 21 of servomotor 8 is determined by a load-responsive valve structure having a hollow plunger 26 acting on a spring-loaded valve element in a chamber 25, such that under light loading of the vehicle chamber 12 communicates with atmosphere via chamber 23 and under heavy loading of the vehicle it communicates with chamber 14 via a one-way valve 27. As a result valve 15 prevents a rise in pressure in pipe 1 from being communicated to the lower chamber of cylinder 5 under light loading conditions while allowing air to pass towards the pipe 1 to maintain vacuum in chamber 14. Under heavier loading the diaphragm in valve structure 6 pulls valve 15 away from its seat to allow a rise in pressure to be communicated to cylinder 5 for increasing braking force. If during operation under light loading condition air leaks into the lower chamber of cylinder 5 no braking action occurs because the atmospheric pressure in control chamber 21 of servomotor 8 causes valve 22 to be open, interconnecting upper and lower chambers. Valve 22 closes under spring loading when chamber 21 is connected to the brake pipe. In a second embodiment (Fig. 2, not shown) the system is simplified by dispensing with the separate manual release valve 7, a handle instead being fitted to valve 22 to enable it to be manually operated. Also the one-way valve 27 is dispensed with by connecting chamber 25 with the upper chamber of cylinder 5 instead of with chamber 14.