Abstract: A hydraulic drive system for a vehicle includes a pressurizing circuit and a working circuit. The pressurizing circuit incorporates a pump driven by a prime mover having a nominal horsepower rating. The prime mover is either shut off or idled when the pressure sensed within the pressurizing circuit is within a desired range and run at an optimum high RPM range when the pressure falls below the desired range. At least one accumulator is provided in the pressurizing circuit. The working circuit includes a plurality of motors for driving at least one vehicle wheel and a motor control valve arrangement which isolates one or more motors from the flow of pressurized fluid while deactivated and drives the motors while activated. As vehicle speed increases and drive resistance decreases, the number of motors propelling the vehicle is progressively reduced. A flow control valve alters flow to the motors.

Abstract: A hydraulic drive system for a vehicle includes a pressurizing circuit and a working circuit that are interconnected by suitable valving. The pressurizing circuit incorporates a fixed displacement pump which is driven by a prime mover having a nominal horsepower rating. The prime mover is shifted between an idling speed when the pressure sensed within the pressurizing circuit is within a desired range and an optimum high RPM range when the pressure within the pressurizing circuit falls below the desired range. At least one accumulator is provided in the pressurizing circuit. The working circuit includes a plurality of motor units for driving the vehicle wheels and a plurality of motor control valves which can be placed in a de-activated position to isolate the associated motor unit from the flow of pressurized fluid and an activated position wherein the motor unit aids in driving the vehicle.

Abstract: A pool heating and circulating system incorporates an internal combustion engine that drives a pump for developing a flow of water. The internal combustion engine has associated therewith an exhaust pipe which is connected to a heat exchanger. An outlet of the pump is also connected to the heat exchanger such that the water extracts the heat generated by operation of the internal combustion engine. The water flowing out of the heat exchanger is then delivered to a filter and a return line. A heat insulating shield is provided about the exhaust pipe to shield the exhaust pipe from excess exposure to cool air. A bypass line can be provided between the outlet of the pump and the heat exchanger so that water can bypass the heat exchanger and flow directly to the return line and filter when it is determined that the pool water temperature is at a desirable temperature. A valve is actually positioned in the bypass line to vary the flow through the heat exchanger.