PURPOSE: To provide a changeover device for a reciprocative vacuum pump working also as compressor in a simple configuration, with which the compressing and evacuating operations can be accomplished without generating an overload condition.
CONSTITUTION: A vacuum pump body 1 is furnished with a sealed chamber 7 being in communication with a cylinder 2 via a communication hole 23 and a valve system 24 which opens and closes the communication hole 23. The valve system 24 is actuated to put the chamber 7 in communication with the cylinder 2, and thereby the cavity capacity in the compressing operation is enlarged, so that acquisition of a compressed air with a specified pressure can be managed without use of any major power, which allows a motor from getting into an overloaded state. According to this constitution, in which enlargement of the cavity capacity is accomplished by provision of the pump body 1 with sealed chamber 7 and valve mechanism 24, it is not required to construct the whole device in a complicated structure, which permits preventing he motor from becoming overloaded state using a compact configuration.
SHIODA HARUTSUGU
KONNO YOSHIO
