Abstract: An arrangement for heating the operator's cabin of a machine driven by an internal combustion engine utilizes the engine oil as a heating medium as it is pressurized by a hydraulic pump and is elevated in temperature as it passes through a throttling element. To accelerate the heating of the internal combustion engine, the return line from the space heat exchanger into which the heated engine oil flows is located upstream of the engine lubricating points. To increase the heat supply to a portion of the engine oil, the hydraulic pump located downstream of the lubricating-oil feed pump suctions away, for the purpose of limiting the flow, some of the engine oil flowing through the main oil distribution system of the engine.

Abstract: Apparatus for heating the cabin of a vehicle operated by an internal combustion engine. The apparatus includes a pump for circulating hot oil from the engine sump and a heat exchanger for heating cabin air with heat from the oil. A throttle valve is mounted downstream from the pump to heat the oil and provide a source of heat particularly during warm-up periods. Also the apparatus includes an adjustable flow apportioning valve for selectively and adjustably dividing the flow of oil downstream from the throttle valve into two separate streams. The heat from one of the separate streams is then recycled directly into the oil at the pump suction. This arrangement maximizes the efficient useage of the heat generated in the throttle for cabin heating purposes. Also disclosed is an improved throttle valve for use in connection with the heating apparatus.