Control valve device with service and emergency limiting valves

A fluid pressure controlled vehicle brake apparatus comprising, in combination:

• (a) a normally charged brake pipe, variations of the fluid pressure in which are effective to control brake applications and brake releases on the vehicle,
• (b) an auxiliary reservoir normally charged to the pressure carried in said brake pipe,
• (c) a second reservoir normally charged to the pressure carried in said brake pipe,
• (d) fluid pressure operated braking means for effecting a brake application on the vehicle,
• (e) a fluid pressure operated brake control valve device comprising:
• (i) valve means having a supply valve and an exhaust valve operable to effect the supply of fluid under pressure from said auxiliary reservoir to said fluid pressure operated braking means and the release of fluid under pressure from said fluid pressure operated braking means to atmoshpere,
• (ii) a stem coaxially arranged with respect to said valve means for effecting the operation thereof,
• (iii) a first movable abutment subject on one side to the pressure of fluid in said brake pipe and subject on the opposite side to the pressure in one of said reservoirs, said first movable abutment being operatively connected to said stem to effect its movement in one direction in response to a reduction in brake pipe pressure on said one side relative to the pressure in one of said reservoirs on said opposite side to cause one end of said stem to operate said vale means to effect the supply of fluid under pressure from said auxiliary reservoir to said braking means to cause a brake application on the vehicle,
• (iv) reservoir charging valve means carried on and so operable by said first movable abutment in response to said reduction in brake pipe pressure as to cut off charging of one of said reservoirs and in response to an increase in the pressure in said brake pipe to the pressure in one of said reservoirs to enable charging of one of said reservoirs, and
• (v) a second movable abutment that may be selectively subject on one side to the fluid under pressure supplied by said valve means to said braking means or to atmospheric pressure and subject constantly on the opposite side to atmospheric pressure, said second movable abutment being so connected to said valve stem as to, when subject on said one side to fluid under pressure supplied to said braking means, effect movement of said stem in a direction opposite said one direction in response to the force of fluid under pressure acting on said second abutment in said opposite direction slightly exceeding the fluid pressure force acting in said one direction on said first movable abutment, said first movable abutment being responsive to a subsequent increase in brake pipe pressure on said one side thereof to effect further movement of said stem in said opposite direction to cause said valve means to establish a venting communication whereby the fluid under pressure supplied to said braking means is released to atmosphere, and operation of said reservoir charging valve means to enable charging of one of said reservoirs, and
• (f) selectively positionable means that, while in one of two positions, enables said opposite side of said first movable abutment to be subject to the pressure in said auxiliary reservoir, and said one side of said second movable abutment to be subject to atmospheric pressure, thereby to enable said first abutment, in response to variations of brake pipe pressure on said one side thereof, to operate said brake control service valve device in the manner of a direct release control valve device, and, while in the other of its two positions, enables said opposite side of said first movable abutment to be subject to the pressure in said second reservoir, and said one side of said second movable abutment to be subject to the pressure in said fluid pressure operated braking means, thereby to enable said first and second abutments, in response to variations of brake pipe pressure on said one side of said first abutment, to operate said brake control service valve device in the manner of a graduated release control valve device, wherein the improvement comprises:
• (g) a lost-motion connection between said supply valve and said exhaust valve to enable shifting of said supply valve relative to said exhaust valve to a valve closed position,
• (h) biasing means for subjecting said supply valve to a force acting in a valve closing direction,
• (i) fluid pressure operated abutment means operable in response to the supply of fluid under pressure to both sides thereof to render said biasing means effective to subject said supply valve to the biasing force of said biasing means and in response to the supply of fluid under pressure to only one side thereof to render said biasing means ineffective to subject said supply valve to the biasing force of said biasing means,
• (j) means for simultaneously subjecting said one side of said fluid pressure operated abutment means and said supply valve to the fluid under pressure supplied by said supply valve to said fluid pressure operated braking means, and
• (k) fluid pressure operated valve means operable in response to the fluid under pressure in said brake pipe to subject the other side of said fluid pressure operated abutment means to the fluid under pressure supplied to said fluid pressure operated valve means and in response to the absence of fluid under pressure in said brake pipe to subject said other side of said abutment means to atmospheric pressure whereby said supply valve is selectively subject cojointly to the fluid under pressure supplied to said braking means and the force of said biasing means or solely to the fluid under pressure supplied to said braking means accordingly as fluid under pressure is present in or absent from said brake pipe thereby limiting the pressure obtained in said braking means when effecting a service brake application to a value less than that obtained in said braking means when effecting an emergency brake application.