Locking device for hydraulic actuator

In a hydraulic actuator which includes a moveable rod extending from the actuator housing, an automatic infinite-position rod locking device comprising:

• a radially contractible locking ring of strong material having a cylindrical inner surface for gripping the rod when the locking ring is contracted and having an axially inclined outer surface;
• means for securing the locking ring around the rod in a position fixed axially in at least one direction with respect to the actuator housing;
• a ring-contracting member around the locking ring and having an inner surface which is axially inclined at the same angle as the outer surface of the locking ring for cooperating with and engaging that surface;
• spring means for applying an axial biasing force to the ring-contracting member in the direction of axial inclination, the angle of axial inclination of the cooperating tapered surfaces of the locking ring and the ring-contracting member being less than 15.degree. to permit a relatively small axial biasing force from the spring means to exert a relatively large gripping force by the locking ring on the rod, and at least one of the cooperating tapered surfaces of the locking ring and the ring-contracting member has a stable dry anti-friction material preventing metal to metal contact thereon;
• hydraulic pressure means for applying an axial force to the ring-contracting member in the direction opposite the biasing force from the spring means;
• and
• means for reducing the pressure in the hydraulic pressure means so that the biasing force from the spring means automatically causes the ring-contracting member to slide axially on the locking ring and thereby cause the locking ring to contract and grip the rod.

In a hydraulic actuator which includes a moveable rod extending from the actuator housing and the hydraulic actuator includes a head, cap and cylindrical wall, all held together by a plurality of bolts which extend beyond the head, an automatic infinite-position rod locking device comprising:

• a radially contractible locking ring of strong material having a cylindrical inner surface for gripping the rod when the locking ring is contracted and having an axially inclined outer surface;
• means for securing the locking ring around the rod comprising surfaces butting against both ends of the locking ring to prevent the locking ring from moving in both axial directions with respect to the actuator housing;
• a ring-contracting member around the locking ring and having an inner surface which is axially inclined at the same angle as the outer surface of the locking ring for engaging that surface;
• spring means for applying an axial biasing force to the ring-contracting member in the direction of axial inclination, the spring means comprising:
• a first plate secured to the bolts in a fixed position and through which the rod extends;
• a cylindrical spacer through which the rod extends and having one end against the first plate and the other end providing one of the surfaces against which one end of the locking ring butts;
• a second plate through which the cylindrical spacer extends;
• a spring positioned around the cylindrical spacer with one end against the second plate and the other end against one end of the ring-contracting member;
• and
• adjusting screws threaded into the first plate and engaging the second plate for adjusting the axial position of the second plate along the cylindrical spacer and thereby adjust the axial force applied to the ring-contracting member by the spring;
• hydraulic pressure means for applying an axial force to the ring-contracting member in the direction opposite the biasing force from the spring means;
• and
• means for reducing the pressure in the hydraulic pressure means so that the biasing force from the spring means automatically causes the ring-contracting member to slide axially on the rocking ring and thereby cause the locking ring to contract and grip the rod.