Abstract: A drive unit for a compressor which is used in a heat pump. The drive unit includes a fuel-injection internal combustion engine which is coupled with the compressor and a starter associated with said engine and is fed from multiphase electric power supply lines. The starter is connected to the electric power supply by means of a switch. The starter is constructed as an electromagnetic drive motor having a stator and a rotor secured to the engine crankshaft and serving at least partly as a flywheel. The coil windings on the stator are fed current from the power source.

Abstract: A heating system for a building utilizing a heat pump having a condenser which is driven by an internal combustion engine. The internal combustion engine drives an additional aggregate, such as a brake, for the purpose of generating additional heat which is added to the main heat carrier in the heating network in the building. The circulating system for the additional heat generating aggregate is self-contained and separate from the heating network of the building.

Abstract: A signal indicating device for an internal combustion engine. The internal combustion engine has a sound absorbing shell surrounding the engine body. An air intake pipe is mounted on the engine and an air intake filter is mounted on the inlet end of the air intake pipe. The signalling device is provided to indicate the degree of contamination of the air filter. The signaling device can be a visual signal or an audible signal.

Abstract: An improvement in an injection internal combustion engine having at least one fuel injection pump therein which is connected to the fuel supply tank through a suction conduit having a check valve connected in circuit therewith. Fuel which is not injected into the internal combustion engine is returned to the supply tank through another check valve located in a separate conduit from the suction conduit. The check valve in the separate conduit, when it is in its seated position, permits a small flow of fuel between the injection pump and the separate conduit.