Patent ID: 7770984

Claim:
A tracked vehicle comprising: a frame; a pair of friction drive track assemblies that each include a drive wheel and an idler wheel, with the idler wheels shiftably mounted to the frame, said pair of track assemblies each including a track belt entrained about a respective drive wheel and a respective idler wheel; a pair of hydraulic actuator assemblies that each include a hydraulic cylinder, said hydraulic cylinders each operably attached to the respective idler wheel to tension the corresponding track belt in response to a hydraulic pressure within the hydraulic actuator assembly and thereby maintain frictional driving engagement between the drive wheel and track belt, said pair of hydraulic actuator assemblies each including an accumulator in fluid communication with a respective hydraulic cylinder; a reservoir of hydraulic fluid; a pump in fluid communication with the reservoir to pump a pressurizing flow of hydraulic fluid from the reservoir to the hydraulic actuator assemblies; a pair of relief valves that are each fluidly interconnected between a respective hydraulic actuator assembly and the reservoir and are operable to selectively permit hydraulic fluid to drain from the respective hydraulic actuator assembly to the reservoir when the pressure in the respective hydraulic actuator assembly exceeds a predetermined maximum pressure; a single charging valve that is fluidly interconnected between the pump and the hydraulic actuator assemblies, with the single charging valve operably coupled to both actuator assemblies to permit the pressurizing flow of hydraulic fluid to be pumped from the pump to the actuator assemblies; and a pair of pressure switches that are each associated with a corresponding frictionally engaged drive wheel and track belt and fluidly coupled to a respective hydraulic actuator assembly to sense the corresponding hydraulic pressure therein and thereby monitor frictional engagement between the corresponding drive wheel and track belt, said pressure switches being operably coupled to the single charging valve to open the charging valve when either one of the sensed hydraulic pressures of the hydraulic actuator assemblies is less than a predetermined minimum pressure, with the charging valve thereby fluidly connecting both actuator assemblies to the pump so that hydraulic fluid is available to be supplied to both actuator assemblies whenever either switch senses a drop of hydraulic pressure below the predetermined level.