1. Field of the Invention
The present invention relates to a parking brake interlock.
2. Statement of the Problem
Many vehicles include pneumatic systems, including air brake systems. Air brake systems are often used for large, heavy vehicles. Advantageously, an air brake system offers advantages such as suitability for large vehicles, chaining between multiple units (such as truck trailers and rail cars, for example), reliability and simplicity, and safety due to automatic brake deployment in the event that air pressure is lost.
Most heavy vehicles possess a parking brake. The parking brake can be deployed when the vehicle is not moving and prevents the vehicle from moving. The parking brake can be deployed when the engine of the vehicle is either running or stopped. The parking brake remains deployed even when the vehicle is not generating any air pressure.
A parking brake system often includes a manually operated valve that is manipulated by the operator of the vehicle. A push-pull valve is one common type of parking brake valve. The parking brake valve is typically mounted on a dashboard or other operator panel of the vehicle.
It is possible for a parking brake valve to be accidentally or unintentionally deployed. For example, the operator could bump the parking brake while entering, exiting, or otherwise moving around in a cabin of the vehicle. In addition, a passenger can manipulate the parking brake valve when the operator is not ready for it to be released.
A prior art approach has been to provide an interlock that prevents release of the parking brake unless the operator steps on and deploys a service brake of the vehicle. As a consequence, the vehicle will not move when the parking brake is released.
In the prior art, an interlock valve is connected to the service brake system. The prior art interlock relays air from the service brake system to the parking brake system and is located upstream of the parking brake valve. Consequently, unless the service brake is deployed, the prior art parking brake system does not receive any air.