Thermal overload protective system

#The present invention relates to a thermal overload protection system, and is particularly concerned with the use of such a system in connection with the valving of a compressor.

#Thermal overload systems are known and usually comprise a temperature sensitive element disposed to be influenced by the temperature of the region to be protected with the temperature sensitive element being operative to, for example, control an electric circuit or the like which will initiate compensatory action. Such compensatory action, in the case of a compressor, may consist of turning off the compressor drive motor.

#Such thermal overload protective systems, at least in connection with compressors, have heretofore disposed a temperature sensitive element directly in the flow path of the gas being compressed and this will, of course, involve the provision of a sealing arrangement in the vicinity of the heat sensitive element to prevent leakage of gas.

#The exact nature of the present invention will become more clearly apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which:

#FIG. 1 is a side elevation view partly broken away of a compressor and drive motor combination.

#FIG. 2 is a view looking in at a cross-section of a valve and cylinder head assembly from the compressor side thereof.

#Referring to the drawings somewhat more in detail, a motor driven compressor arrangement according to FIG. 1 may comprise an outer housing 10 in the upper housing 14 of which there is mounted the electric drive motor while in the lower housing 12 of which there may be mounted the compressor with the compressor consisting, for example, of four radial pistons displaced 90.degree. from one another in the circumferential direction and likewise displaced axially from one another. Each piston is reciprocable in a respective cylinder and the outer end of each cylinder is closed by a respective valve plate and head assembly 16 having inlet and outlet passages for the gas being compressed by the compressor.

#According to the present invention, at least one cylinder head is provided with a blind hole 18 bored therein into which is inserted a thermistor (PTC sensor) 20. This sensor is electrically connected by cable means 22 to control component 24 which controls the supply of energy to the drive motor.

#FIGS. 2 through 4 show details in respect of the cylinder head and the valving pertaining thereto. In FIG. 2, which is a view looking at the cylinder head and the valve plate from the compressor side, it will be seen that the valve plate, identified by reference numeral 26, has circumferentially distributed inlet ports 28 and inwardly therefrom the circumferentially distributed outlet ports 30.