Fishing – trapping – and vermin destroying
Patent
1997-04-24
2000-09-19
Hepperle, Stephen M.
Fishing, trapping, and vermin destroying
137312, 137332, F16K 1107
Patent
active
061203025
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a reversing valve for a multiple-circuit brake system for a motor vehicle in accordance with the preamble of claim 1.
DE 4,030,361 A1 and the parallel EP O,477,519 Al describe an electropneumatic brake system that uses a relay valve (9 in the only figure) in order to switch between electrically-controlled and pneumatically-controlled brakes. Generally, with electropneumatic brakes, it must be guaranteed that at least a conventional pneumatic braking function remains fully preserved in the event of the failure of the electrical control or of other electrical components. For this purpose, a driver brake valve has an electrically component, namely, a sensor that scans the position of the brake pedal, and a brake request signal proceeds to the electrical control. Said signal then transmits electrically actuating signals in accordance with preselected parameters to proportional valves, which inject the actual pneumatic brake pressure into the brake cylinder. The driver brake valve also has a purely pneumatic component, which controls brake pressure purely pneumatically, as a function of the position of the brake pedal. The overriding brake circuit is the electrical brake circuit. However, if it fails, there is an automatic reversal to the purely pneumatic brake. The relay valve used in the aforementioned publications for reversal is, in principle, a seat valve, which has a complicated construction and consequently is expensive.
In addition, reversing valves of the aforementioned type also are used in a brake system having two pneumatic brake circuits with the task of, for normal operating conditions, routing the overriding brake circuit to a corresponding actuator, and, for nonstandard operating conditions, routing the secondary brake circuit. Since two brake circuits that are independent of each other are joined in this valve, it must be guaranteed that any possible leakage between the circuits is ventilated to atmospheric pressure. Therefore, in principle, this type of reversing valve can be used: safety, a pneumatic circuit operates only in the event of the failure of the electrical circuit and
In an paper by Jurgen Wrede and Heinz Decker, "Brake by Wire for Commercial Vehicles", published at the "International Truck and Bus--Meeting and Exposition, Toledo, Ohio, Nov. 16-19, 1992, (published in SAE TECHNICAL PAPER SERIES No. 922,489), an electropneumatic brake system is described on p. 5, for which decoupling of the two pressures of the two circuits is carried out by means of a relay valve having a double seal and a vented inner chamber.
SUMMARY OF THE INVENTION
The purpose of the invention is to create a reversing valve which has a simple construction and operates reliably over a long operating life.
This problem is solved by means of the features indicated in claim 1. Advantageous configurations and improvements of the invention are to be taken from the subclaims.
Generally, a reversing valve in accordance with the invention is conceived as a sliding valve, which enables a very simple construction consisting of a piston with seals, preferably O-rings, a pull-back spring and a housing that comprises several drilled holes. The two circuits are relieved by means of a double seal with an air hole to the outside. Forming a reversing valve as a sliding valve results in a very low switching pressure, since the O-ring seals have only a limited amount of friction. In addition, the switching pressure supplied by the first circuit is practically independent from the pressure prevailing in the second circuit.
Since the double seal slides along a drilled hole of the housing when the valve is shifted, in order to guarantee a decoupling of the two circuits and a venting to the atmosphere, the life of the valve depends on the wear of the double seal. An improvement of the invention consequently provides for the piston of the valve to be provided with wing-like guide blades and for control pressure for reversing the valve to be guided such that a flow pulse impinges
REFERENCES:
patent: 1849702 (1932-03-01), Bard
patent: 2124274 (1938-07-01), Nichols
patent: 2631001 (1953-03-01), Griswold
patent: 4002374 (1977-01-01), Horowitz
patent: 4067348 (1978-01-01), Davis
patent: 4506697 (1985-03-01), Marchant
patent: 4711392 (1987-12-01), Kidouchi et al.
Wrede et al., Brake by Wire for Commercial Vehicles, SAE International, Warrendale, PA, Nov. 16-19, 1992, pp. 1-11.
Fries Ansgar
Vollmer Otto
Hepperle Stephen M.
Knorr-Bremse Systeme fur Nutzfahrzeuge
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