A conventional method for providing either engine drive or electric motor drive for a refrigerant compressor, such as that which might be used with a self-contained transportable refrigeration unit to preserve a perishable cargo during transit, includes a prime mover, such as an internal combustion engine driving the compressor through a centrifugal clutch, or the compressor may be alternately belt driven by an electric motor.
One example of such a dual drive mechanism to be employed as part of a transportable refrigeration unit, where an internal combustion engine, an electric motor, a refrigerant compressor, and a clutch are all disposed in an in-line arrangement, is to be found in the patent to L. T. Sellstrom, U.S. Pat. No. 2,667,761, issued February, 1954. With the foregoing arrangement, each of the engine, the motor, and the compressor is provided with a respective shaft, with the engine shaft and the motor shaft being connected by a drive coupling and the motor shaft and the compressor shaft also being connected by a drive coupling. In addition to the plurality of drive shafts and drive couplings, the necessity of the number of bearings that would be required for this type arrangement can prove to be both uneconomical in terms of manufacture and compactness.
Another example of a prime mover-electric motor dual drive mechanism can be found in the patent to G. Lagerstrom, U.S. Pat. No. 3,404,529, issued October, 1968, wherein both power sources may drive a common drive shaft, and bearing means are provided whereby the rotor of the electric motor may rotate on the common drive shaft. However, by the nature of the foregoing arrangement, a dual clutch and bearing arrangement is required which consequently may also become uneconomical in terms of manufacture and compactness.