Air-hydraulic blind-riveting tool with short reset time

A tool for setting a blind rivet, said tool comprising:

• a housing forming an air chamber, a liquid-filled hydraulic chamber adjacent thereto, and a liquid-filled working chamber communicating with said hydraulic chamber;
• a working piston in said working chamber and carrying a chuck for grasping a mandrel of a blind rivet, said piston being displaceable in said working chamber between a ready position wherein a mandrel can be fitted into said chuck and an actuated position wherein said chuck is retracted;
• an air piston in said air chamber subdividing same into a front compartment and a rear compartment and displaceable between a front position of maximum volume of said rear compartment and minimum volume of said front compartment and a rear position of minimum volume of said rear compartment and maximum volume of said front compartment, said housing being formed at the front end of said front compartment with a first throughgoing hole for gas flow between same and the atmosphere and at the rear end of said rear compartment directly in a wall thereof with a second throughgoing hole for gas flow between same and the atmosphere;
• a hydraulic piston carried on said air piston and displaceable in said hydraulic chamber between an advanced position pressurizing said hydraulic chamber and corresponding to said front position of said air piston and a retracted position corresponding to said rear position of said air piston;
• first valve means for admitting, when actuated, pressurized air into said rear compartment and thereby displacing said air piston into said front position, displacing said hydraulic piston into said advanced position, and displacing said working piston into said actuated position;
• second valve means on said wall in said second hole and responsive to air pressure for blocking air flow from said rear compartment out through said second hole when said first valve means is actuated to admit compressed air to said rear compartment and for opening and allowing air flow from said rear compartment out through said second hole when said first valve means is not actuated, said air chamber being generally cylindrical and said housing having an end cap constituting a rear wall of said air chamber, said second valve means being provided in said end cap;
• and a spring braced between said housing and said working piston and urging same into said ready position, whereby displacement of said working piston from said retracted position into said ready position by said spring absent actuation of said first valve means automatically displaces said air piston into said rear position and forces air out of said rear compartment through said second hole, said second valve means including:
• a valve seat formed at said second hole,
• a valve disk sealing engageable over said seat to block gas flow from said rear compartment,
• a valve spring braced between said housing and said disk and urging same away from said seat,
• an abutment element, said valve spring normally pressing said disk against said element, said element being formed with at least one gap for air flow through said second hole when said disk lies against said element, and
• a tubular spring housing fixed in said end cap and formed with a shoulder having said seat, said spring housing having an inner diameter greater than the outer diameter of said disk, said element being a washer having a plurality of angularly spaced and radially outwardly extending tabs engaging the inner wall of said tubular housing.