Lubricating means for gas-operated cylinders

In combination, a cylinder, a piston in said cylinder dividing it into a working chamber adjacent the head end of the cylinder and an idle chamber adjacent the rod end of the cylinder which vary inversely in size in response to reciprocation of the piston in the cylinder, said piston having a rod extending axially through said idler chamber and outwardly beyond the rod end of the cylinder for connection with a force-applying means for displacing the piston in a direction toward the head end of the cylinder, port means adjacent the head end of the cylinder for introducing gas under pressure to said working chamber for displacing the piston in a direction toward the rod end of the cylinder, means defining a lubricant chamber interposed between said port means and said working chamber and through which the gas from said port means is directed to said working chamber, an air-permeable, lubricant-impregnated material in said lubricant chamber, said lubricant chamber having a wall provided with a plurality of apertures through which said gas is adapted to flow from said lubricant chamber to the working chamber, a valve plate cooperating with said apertured wall for blocking said apertures when the gas pressure in the working chamber is equal to or exceeds the pressure at said port means and means for causing the gas to bypass said lubricant chamber when the gas flow is from the working chamber toward said port means.