Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Reexamination Certificate
2000-02-07
2001-09-11
Oberleitner, Robert J (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
C303S071000
Reexamination Certificate
active
06286912
ABSTRACT:
This invention relates to pneumatically-operated braking systems for vehicles and in particular to supply dump valves for systems of the kind for use in tractor-trailer combinations.
Known pneumatically-operated braking systems for tractor-trailer combinations embody a safety feature, typically called a “supply dump valve”, that is operative to limit the loss of air stored in an air reservoir of the vehicle should a pneumatic control line between the tractor and trailer become ruptured or otherwise damaged. By restricting the loss of supply air the operation of the trailer emergency relay valve is brought about. The supply dump valve itself can usually be integrated into the trailer control valve which is fitted to the tractor. A trailer control valve for controlling operation of the brakes on the trailer under the control of an electronic braking system (EBS) is usually connected to the trailer through flexible couplings otherwise known as “Suzies”. The supply dump valve acts substantially to bring about the operation of the trailer emergency relay valve and hence the application of the trailer brakes.
Conventionally the supply dump valve comprises a differential pressure actuated valve which only moves when a pressure differential acts across it. Known valves are fitted to both conventionally actuated pneumatic braking systems as well as electronically controlled braking systems. As the supply dump valve only ever operates when a failure in the trailer control line occurs, the supply dump valve is classified as a redundant feature. This means that the integrity of the dump valve should be checked by some means to ensure that if a fault within the valve is detected, the system can inform the operator at a stage before the valve is required actually to function. Alternatively it can be arranged so that the valve is actually partially operated during normal operation so as to “work” whereby to reduce the possibility of the valve elements either sticking or seizing when the dump valve is required to perform the function for which it is intended.
In one known construction the supply dump valve is made of a differential area supported by a spring so that on each and every brake application a differential force is generated by the application of brake pressure across a differential piston. This causes the piston and a seal acting between the piston and a bore in which it works to be exercised. A problem with this arrangement is that typically the valve would not move until substantial brake pressure, perhaps between two and three bar, had been applied. Since most vehicle stops fall within a range of 0-0.2 g which require less than 3 bar, typically only 0.5 to 1 bar, the valve does not move and thus is not exercised reliably. In fact it is unlikely, in a vehicle not subjected to substantial braking action, such as is experienced in near continuous motorway driving, for sufficient force required to exercise the supply dump piston to be generated, except on only a few occasions.
According to one aspect the invention provides a supply dump valve for a pneumatically-operated braking system for vehicles comprising a piston of differential outline adapted to work in a stepped bore in a housing, characterised in that a supply pressure acting upon differential areas causes the piston to move in a direction to take up a small built in clearance, thereby earthing out the piston against a spring, and in which operation of a park brake causes a pressure rise in a delivery line to said valve in turn to cause the piston to move in an opposite direction until it engages with a stop so that actuation of the park brake causes the piston to be exercised.
This ensures that the piston is exercised at least once on each and every journey.
Preferably the piston is of substantial diameter.
After release of the park brake the piston is seated upon the spring and upon application of the park brake the pressure in the delivery line drives the supply piston into engagement with the stop.
Should a leak in the trailer control line occur, then the pressure in the valve control chamber will drop causing the piston to move in a direction to throttle the line between the reservoir and the valve.
One embodiment of our invention is illustrated in the accompanying drawings which is a cross section through a supply dump valve for a pneumatically-operated braking system for a vehicle of the tractor-trailer combination type.
REFERENCES:
patent: 3525555 (1970-08-01), Meyer et al.
patent: 3572846 (1971-03-01), Cruse
patent: 3580646 (1971-05-01), Ternent
patent: 3685870 (1972-08-01), Jensen
patent: 3778119 (1973-12-01), Kersting
patent: 3809441 (1974-05-01), Klimek
patent: 3832015 (1974-08-01), Beck et al.
patent: 3861761 (1975-01-01), Siebold et al.
patent: 3892444 (1975-07-01), Durling
patent: 4653811 (1987-03-01), Fauk et al.
patent: 4679865 (1987-07-01), Ulrich et al.
patent: 30 44 228 A 1 (1982-03-01), None
patent: 2280535 (1975-07-01), None
patent: 2310250 (1976-05-01), None
Carlson Gaskey & Olds P.C.
Meritor Heavy Vehicle Systems LLC
Oberleitner Robert J
Torres Melanie
LandOfFree
Pneumatically-operated braking system for vehicles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pneumatically-operated braking system for vehicles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pneumatically-operated braking system for vehicles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439952