Spring-applied, pressure-released brakes are useful, for example, in construction vehicles or other vehicles that require an automatic braking in the event of an engine failure. In order to tow the vehicle for service, the brakes must be released. Most brake release systems require an alternate pump and associated valves on each vehicle with the fluid from the alternate pump being controlled by the brake valve on the vehicle. The alternate pump on each vehicle add cost to the vehicle and the spool of the brake valve is a known path for fluid leakage thus requiring an alternate pump of a larger capacity than is actually needed. The present brake release mechanism provides an isolating mechanism that is effective to isolate a work port of a brake valve from a valving element in a housing. The isolating mechanism is adapted to connect with an alternate source of pressurized fluid and adapted to direct the pressurized fluid to a brake for release thereof. The isolating mechanism and the alternate source of pressurized fluid are adaptable to several vehicles thus eliminating the need of the alternate pump and associated valves on each vehicle. Furthermore, the alternate source is smaller in capacity since the leakage in the brake valve during towing is eliminated.
A mechanical emergency and parking brake system, for vehicles of the type having a power steering pump, includes a check valve having an input port coupled to the pump outlet and an output port coupled to hydraulically deactuated spring brakes through brake lines. A pilot check valve has its inlet port coupled to the input port of the check valve and an output or return port coupled to the power steering gear. The pilot port of the pilot check valve is coupled to the output port of the check valve so that the pilot check valve opens only when the pressure at the output port of the check valve is above a chosen pressure. This allows hydraulic fluid to flow from the pump, through the pilot check valve, through the power steering gear and to the reservoir. To reapply the brakes, the operator actuates a valve which disconnects the brake ports from the output port of the check valve and connects the brake lines to the reservoir. This occurs when the operator wishes to set the brakes when stopped or in emergency situations. If desired, a pressure release valve can be fluidly connected to the output port of the check valve to limit the pressure at the output port.
The driving device comprises a hydraulically shiftable friction coupling and a friction brake by means of which an input can be connected to a gear and which perform the function of a parking brake wherein an auxiliary release device comprising an adjustable accumulator piston and gear shift pistons interacting therewith separate friction coupling and friction brake thus interrupting the drive train; the accumulator cylinder of the auxiliary release device is connected to a supply tank via a connecting line and is provide with a blocking device which cuts off the connection to the supply tank when the auxiliary release device is actuated.
A brake release apparatus for a vehicle equipped with a spring-applied hydraulically-released brake system. The apparatus includes a tow hook attached to the vehicle and operably connected to a hydraulic cylinder so that a towing force on the tow hook actuates the hydraulic cylinder. The hydraulic cylinder is connected to transmit a hydraulic pressure to the vehicle brakes, releasing the brakes to permit towing. A spring returns the tow hook to its original position when the towing force is removed, thereby permitting the spring-activated brakes to be reapplied.
A vehicle brake system includes a check valve having an input port coupled to a fluid pump outlet and an output port coupled to hydraulically deactuated spring brakes through brake lines. A pilot check valve has a pilot port, an inlet port coupled to the input port of the check valve and a return port coupled to the fluid reservoir. The pilot port is coupled to the output port of the check valve so the pilot check valve opens only when the output port is pressurized. This allows hydraulic fluid to flow from the pump, through the pilot check valve and to the reservoir. To set the brakes when stopped or in emergency situations the operator actuates a valve which dumps the fluid in the brake lines into the reservoir. A second pilot check valve has its pilot port connected to a brake pedal actuated master cyinder, its inlet connected to the brake line and its outlet connected to the reservoir. Pressing on the brake pedal connects the brake line to the reservoir through a variable restriction so to allow the spring brakes to be applied in the modulated manner of service brakes.
A simple hand held carbon dioxide applicator having a pressurized carbon dioxide cartridge is used to release spring applied hydraulically released brakes. The hydraulic line extending between the hydraulic pump and the brake control valve is provided with a first coupler of a quick coupling with the corresponding second coupler being hydraulically positioned between the hydraulic line and the pump. An auxiliary line is provided having an auxiliary coupler identical to the second coupler so that the auxiliary line can be attached to the first coupler. The auxiliary line is also provided with a gas check valve in the form of a schraeder valve to which the hand held carbon dioxide applicator is pneumatically coupled.
