Abstract: A portable electric fastener driving apparatus includes a unique fastener driving element operatively connected to the piston of an air spring which is charged to provide energy for driving fasteners. The air spring is charged by a unique jacking and release system including a drive gear selectively engaging a rack on the driving element to move the piston and compress the air spring. Motive power for the jacking apparatus is provided by a motor, preferably remote from the driver apparatus and connected thereto by a flexible drive cable. Control apparatus is included.

Abstract: Improved valve apparatus for expansible chamber devices, such as reciprocating piston compressors, includes in a preferred embodiment, a chamber having two chamber intake ports, each normally closed by a respective valve member. A first valve member is biased to close a first port, and a second member is more forcefully biased to close a second port which is larger in cross-sectional area than the first port. The first valve member opens the first port in response to an intake pressure differential less than that which will open the second port. Subsequently, and upon increased intake pressure differential, the second valve member opens the second port and reduces the working pressure affecting the first valve. This permits the first valve to positively close its port at or near the end of the suction stroke of the piston, the second valve also closing its port due to the more forceful bias.