This invention relates to a transmission disconnect arrangement generally and more particularly to a disconnect arrangement which will place the transmission of a vehicle in a neutral condition in response to application of the service brakes or the application of a spring-apply, pressure-release parking brake system.
It is known in the prior art to provide means to disconnect the transmission, that is to effectively place the transmission in neutral, in response to application of the service brakes. Normally on certain types of vehicles, such as rubber tired loaders, it has been found desirable to provide two brake pedals, one of which engages the service brakes while maintaining the transmission in whatever condition the operator has placed it, and the other pedal applies the service brakes while simultaneously disconnecting the transmission. The latter situation not only introduces braking to the vehicle but interrupts any drive from the engine to the wheels. Such a system is shown in U.S. Pat. No. 4,088,208 issued to Frederick R. Goode on May 9, 1978.
It is also desirable to disconnect the transmission from the parking brake if such a vehicle is engaged. That is to prevent the operator from inadvertently damaging the parking brake by attempting to drive the vehicle with the parking brake engaged. This arrangement has also been provided in the prior art. However, such arrangements have been with a parking brake which is not of the fail-safe type. A fail-safe type parking brake, one that is applied whenever the air pressure is lost, such as through a broken hose or a malfunction in some component of the air system in the vehicle, is highly desirable. However, because it is of the fail-safe type, it lacks the signal pressure normally available on the conventional type of parking brake needed to actuate the transmission disconnect.
It is therefore an object of the present invention to provide a fail-safe type parking brake system which is capable of actuating the transmission disconnect when the parking brake is applied.
It is also an object of this invention to provide a transmission disconnect which is actuated by a signal emanating from either the service brakes or from the release of a spring-apply parking brake.