Wabco Westinghouse Fahrzeugbremsen Gmbh

Wabco Fahrzeugbremsen Gmbh

Hans-Joachim Schulz

Erich Reinecke

Karl-Heinz Deike

Wolfgang Pohl

Jurgen Sandmann

A brake pressure control valve for regulating the braking pressure in the trailer brake system of a tractor-trailer vehicle, so as to develop the trailer brake pressure to a preset level ahead of the braking pressure in the tractor brake system during a pilot phase of brake operation. The preset level of this advance trailer brake pressure can be selected by an adjustable member that forms a part of the auxiliary valving that controls the point at which the pilot phase of operation is terminated. A limit stop is cooperatively arranged with this adjustable member in order to provide a means for limiting the point beyond which the auxiliary valving is activated, to thereby prevent the advance trailer brake pressure from exceeding a specified safe maximum value.

Trailer control valve device for the trailer brakes of a tractor-trailer

An apparatus is disclosed for the control of brake pressure in a trailer pulled by a tractor. The apparatus includes a two-circuit controllable relay valve as the trailer control valve. The first circuit is controlled by the brake valve of the tractor with the pressure from the brake apparatus of such tractor. The second circuit can be optionally-connected to a distribution valve with a pressure medium source with a specified pressure or with atmosphere. Activation of the distribution valve is controlled so that the distribution valve connects the second circuit with the pressure medium source before or at the beginning of the activation of the first circuit. With this apparatus, the brake pressure can be increased in the brake apparatus of the trailer prior to increase of the brake pressure in the brake apparatus of the tractor. The level of brake pressure increased first in the brake unit of the trailer can be regulated by a set screw acting on the trailer control valve.

Apparatus for the control of brake pressure

This invention relates to a brake pressure control valve and, more particularly, to a tractor-trailer control valve which includes a differential pressure surface relay piston that on one hand is acted upon by the control pressure from a control chamber and on the other hand by modulated pressure from a working chamber. The brake pressure control valve includes a first combination inlet and outlet valve which works together with the relay piston whereby the working chamber can be pressurized and vented via the first inlet and outlet valves. An auxiliary control chamber which is defined by the differential surfaces of the relay piston is connectable either to the working chamber or to the control chamber via second inlet and outlet valves. The pressure control surface of the relay piston is located opposite the working surface that is acted upon by control pressure in the control chamber. The pressure control surface can be enlarged by the pressure surface of the auxiliary control chamber. Thus, it is possible to modulate a pressure with an initial relatively sharp rise which is followed by a less gradual increase. In order to have a substantially equal characteristic curve during brake pressure decrease as well as during brake pressure buildup, and in order to reduce the hysteresis of the brake pressure control valve, the auxiliary control chamber is no longer vented into the working chamber but is directly vented to the atmosphere. The fluid pressure supply of the inlet valve is separated from the fluid pressure exhaust of the outlet valve of the second combination inlet and outlet valve.

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Wedemark, Germany

Hans-Joachim Schulz