Rotary chucking cylinder for machine tool

Claim 1

In a rotary chucking cylinder for operating a chucking tool of a lathe or other machine tool comprising an outwardly closed cylinder having front and rear walls, each of said walls having a central bore, a piston axially slidable in and rotatable with said cylinder and dividing the inside thereof into two chambers, a shaft coaxially with said piston and having a front section and a rear section secured to the opposite sides of said piston and axially slidable in said central bores of said walls, sealing means between said walls and said shaft sections for sealing said chambers, said rear shaft section having a pair of channels extending from a point near the rear end of said shaft longitudinally through said entire rear shaft section and through at least a part of said piston, said rear shaft section having a part projecting to the outside of said cylinder, nonrotatable supply and discharge means connected to said outwardly projecting part of said rear shaft section and movable in the axial direction with said shaft for alternately supplying a fluid pressure medium to one of said channels and for alternately discharging the return flow of said medium from the other channel, a valve unit mounted adjacent said piston and extending diametrically to said shaft and comprising a pair of check valves each having a valve chamber, the wall of each of said valve chambers having a first bore forming a valve seat and a second bore, said first bore of a first of said valve chambers being adjacent to and communicating with the front end of a first of said channels, and the second bore of said first valve chamber communicating with one of said cylinder chambers, said first bore of the second valve chamber being adjacent to and communicating with the front end of the second channel, and the second bore of said second valve chamber communicating with the other cylinder chamber, a valve member in each of said valve chambers and movable radially to the axis of said shaft, and a spring acting upon each of said valve members and tending to press said valve member upon its valve seat so as to close said first bore leading to the front end of the associated channel, a central control chamber intermediate said two valve chambers and valve seats, a small control piston slidable back and forth within said control chamber toward said two valve chambers and having a tappet pin projecting from each end adapted to hit against and lift that valve member off its seat toward which said control piston is moving, said front ends of said two channels terminating into said control chamber adjacent to the opposite ends thereof and at the opposite sides of said control piston, whereby when said pressure medium is supplied through a first of said channels into said control chamber, it lifts said first valve member off its seat and then passes through said first valve chamber to one of said cylinder chambers, while at the same time said pressure medium acts upon said control piston so that its tappet pin hits against and lifts said second valve member off its seat and thereby permits the pressure medium contained in said other cylinder chamber to flow out of the latter and back through said second valve chamber and said other channel; said chucking cylinder having the improvement comprising a hub on and coaxial to said shaft directly adjacent to said piston, said hub having a diameter larger than said two shaft sections and smaller than said piston, said hub having a transverse bore extending diametrically through said hub so that its axis and the axis of said shaft intersect substantially at right angles, saiD valve unit being inserted into said transverse bore before said shaft and piston is inserted into said cylinder and having a total length substantially equal to the length of said bore and the diameter of said hub, and a locking ring slipped over the peripheral surface of said hub from the free outer end thereof and covering the outer ends of said transverse bore and substantially engaging with the opposite outer ends of said valve unit.