Patent ID: 6520599
Filing Date: 2003-02-18
Classification: B60T

Abstract:
A backup system for pneumatically backing up an electronic system of compensating for load in applying brakes on a railcar truck equipped with brake pipe controlled brake equipment, said brake equipment including a main reservoir pipe, a brake pipe and a truck control valve, said backup system comprising:(a) a control reservoir; (b) a selector volume; (c) a displacement volume in communication with a distribution network; (d) a quick service valve having a pilot port connected to said distribution network such that said quick service valve disconnects said distribution network and a dispersal network when pressure at said pilot port exceeds a trigger level; (e) a release control valve having a pilot port linked to said brake pipe such that when said brake pipe pressure exceeds a threshold level said release control valve disconnects said selector volume from said control reservoir and vents said selector volume; (f) a variable load valve having a supply port in communication with said distribution network, a control port in communication with said distribution network, a load weigh port for receiving pressure indicative of load borne by said railcar, and an emergency port for receiving pressure via an emergency network; said variable load valve providing from an output port thereof (I) a first load compensated pressure in response to pressure at said control and said load weigh ports and (II) a second load compensated pressure in response to pressure at said control, said load weigh and said emergency ports; (g) a main relay valve having a supply port linked to said main reservoir pipe and a control port connected to said output port of said variable load valve; said main relay valve for providing from an output port thereof an output pressure proportional to the pressure acting on said control port thereof; (h) a main control valve comprising an emergency valve and 3-way valve, said emergency valve linking said emergency network to atmosphere as long as said brake pipe pressure stays above an emergency level below which said emergency valve links said emergency and said distribution networks; said 3-way valve having a first pilot port in communication with said brake pipe and a second pilot port communicating with said control reservoir; and (i) a main transfer valve for operating in (I) a piloted state wherein said truck control valve is disconnected from said output port of said main relay valve and is linked to said main reservoir pipe thereby placing said main control valve in a cut-out mode and (II) an unpiloted state wherein said truck control valve is linked to said output port of said main relay valve thereby placing said main control valve in a cut-in mode of operation wherein said main control valve assumes one of: (I) a release state wherein said brake pipe pressure increases relative to pressure in said control reservoir causing said 3-way valve (a) to link said brake pipe and said control reservoir thereby allowing said control reservoir to pressurize and (b) to link both said distribution and dispersal networks to atmosphere thereby exhausting said displacement volume, said pilot port of said quick service valve and said supply and said control ports of said variable load valve thus preventing said main relay valve from outputting said output pressure; (II) a service state wherein said brake pipe pressure drops relative to pressure in said control reservoir yet remains above said emergency level causing said 3-way valve (a) to disconnect said brake pipe and said control reservoir and when said brake pipe pressure falls below said threshold level said release control valve links said control reservoir with said selector volume and (b) to link said dispersal network with said brake pipe and said main reservoir pipe with said distribution network thereby allowing pressure to build within said displacement volume and against both said pilot port of said quick service valve and said supply and said control ports of said variable load valve whereupon said quick service valve disconnects said distribution and dispersal networks to prevent pressure in said main reservoir pipe from exhausting via said brake pipe and whereupon said variable load valve outputs said first load compensated pressure thus causing said main relay valve to output to said truck control valve said output pressure proportional to said first load compensated pressure; and (III) an emergency state wherein said 3-way valve continues operating according to said service state yet said brake pipe pressure falls below said emergency level causing said emergency valve to link said emergency network with said distribution network and allow pressure from said main reservoir pipe to build against said emergency port thereby causing said variable load valve to output said second load compensated pressure thus causing said main relay valve to output to said truck control valve said output pressure proportional to said second load compensated pressure.