This invention relates to a continual quick service valve device operative sequentially with each successive brake pipe pressure reduction over the entire service application range of brake pipe pressure reductions to effect "quick service" transmission through a train brake pipe of a pressure reduction wave. Fluid under pressure heretofore released from the quick action chamber of a conventional brake control valve device to atmosphere upon effecting a service reduction of brake pipe pressure is supplied to one side of an abutment to cause it to open a quick service valve that establishes a communication between the train brake pipe and a quick service volume. This abutment also constitutes a snap-acting valve for controlling flow between the quick service volume and atmosphere and simultaneously effecting a change in its effective area. Consequently, so long as the one side of this abutment is subject to fluid under pressure released from the quick action chamber, it successively deflects in opposite directions to operate the quick service valve for controlling flow from the train brake pipe to the quick service volume and simultaneously, acting as a valve, repeatedly first cuts off flow from the quick service volume to atmosphere and thereafter releases to atmosphere the fluid under pressure supplied to this volume from the train brake pipe. Means are provided for constantly releasing to atmosphere at a restricted rate the fluid under pressure supplied to the one side of the abutment so that upon movement of the brake control valve device from its service to its lap position, the repeated operations of the continual quick service valve device are terminated. However, upon any subsequent movement of the brake control valve device from its lap position to its service position in response to a manually effected further reduction of brake pipe pressure, this continual quick service valve device will operate in the manner described above to repeatedly first vent fluid under pressure from the brake pipe to the quick service volume and thereafter release this fluid under pressure from this volume to atmosphere until the brake control valve device returns to its lap position.
A brake accelerator has a control chamber connected through a throttle orifice to a brake line. The brake system includes a control valve in which is an emergency brake piston one side of which is subjected to brake line pressure and the other side of which is subjected to pressure in the control chamber. The emergency brake piston, as a function of a pressure drop in the brake line, opens a brake line outlet valve so that air flows from the brake line through an inlet valve. The inlet valve is held by a control piston in its open position at the start of a pressure drop in the brake line and the air is flowed into a chamber to form a control pressure. The control pressure acts on the control piston to open an outlet valve for tapping or drawing off the air from the chamber and to close the inlet valve in such a manner that after a predetermined period of time when the pressure in the chamber has dropped below a predetermined value the control piston will be returned by a spring to its initial position so that a limited quantity of pressure fluid is drawn from the brake line by the accelerator.
An accelerated application valve having a cyclic mode of operation during one phase of which a local quick service reduction of brake pipe pressure occurs and a steady state mode of operation during which a continuous local quick service reduction of brake pipe pressure is achieved. The specific mode of operation is dictated by a control signal that varies with the degree of service brake application called for, this control signal being the "breather" pressure at the ABD/ABDW Control Valve emergency portion.
An emergency valve device for a direct release triple valve for use in braking systems is proposed and which for rates of fall of brake pipe pressure below a given rate permits a discharge via a restriction to atmosphere of quick action chamber reference pressure but for higher rates this discharge cannot keep up with the rate of fall of brake pipe pressure and the valve device moves further cutting off the restriction and produces a servo action to operate a vent valve connected to the brake pipe and produce an emergency application by connecting the emergency reservoir to the brake cylinders.
A fluid brake control system is provided including a brake control pipe and a control valve comprising a quick action chamber and an emergency slide valve operable from a normal to a service brake position in response to service reduction in brake pipe pressure, the emergency slide valve having a fluid pressure differential operated abutment disposed between a first pressure chamber within a housing on one side of the abutment subject to pressure of the quick action chamber, and a second pressure chamber contained in a housing cover on the other side of the abutment connected by a passage to the brake pipe. The cover includes quick action control apparatus including a quick action poppet type valve operably connected to the abutment for actuation of the quick action valve by the abutment from a normally closed to an open position in response to the operation of the abutment in one direction to a service braking position. The quick action poppet type valve vents fluid from the brake pipe when it is opened.
A valve arrangement is provided for giving a continuous quick service facility in a triple valve controlling rail vehicle brakes in response to brake pipe pressure reductions. The arrangement comprises a pressure responsive member which responds to more than a predetermined brake pipe pressure reduction in relation to a reference pressure to operate a pulsator which discharges repetitive pulses of air from the brake pipe for as long as the pressure reduction persists.
