Locking device for hydraulic actuator

Claim 2

In a hydraulic actuator which includes a movable rod extending from the actuator housing, an 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 axially fixed in only 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; screw means for applying an axial force to the ring-contracting member in the direction of inner surface inclination, which is the one direction in which the locking ring is axially fixed with respect to the actuator housing, to cause the ring-contracting member to slide axially on the locking ring thereby causing the locking ring to contract and grip the rod, and the angle of inclination of the cooperating tapered surfaces of the locking ring and the ring-contracting member is too high to result in self-tightening and produces a larger axial disengaging component force than the frictional resistance force on the inclined surfaces, whereby the locking device is not actuated by rod movement in the direction opposite the direction of axial force provided by the screw means and the locking device is self-releasing upon release of the axial force provided by the screw means.

Claim 3

The rod locking device of claim 1, wherein the hydraulic actuator is a hydraulic cylinder having a reciprocatably driven rod extending from the hydraulic cylinder housing, and the locking device locks the rod against axial movement.

Claim 4

The rod locking device of claim 1, wherein the hydraulic actuator is a rotary actuator having a rotatably driven rod extending from the actuator housing, and the means for securing the locking ring also secures the locking ring against rotational movement with respect to the actuator housing to enable the locking device to lock the rod against rotational movement and comprising slots in the locking ring and in the ring-contracting member and a key within the slots for preventing rotation of the locking ring within the ring-contracting member.

Claim 5

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° 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.

Claim 6

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° 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.

Claim 7

The rod locking device of claim 4, wherein the means for securing the locking ring comprises a surface butting against the thicker end of the locking ring to prevent the locking ring from moving in the direction of the surface.

Claim 8

The rod locking device of claim 4, including a hydraulic pressure source for the hydraulic actuator and wherein the means for reducing the hydraulic pressure is interconnected to the hydraulic pressure source of the hydraulic actuator to automatically reduce the hydraulic pressure in the locking device when the pressure in the actuator is reduced, whereby the rod is automatically locked in position if pressure is lost in the actuator.

Claim 9

The rod locking device of claim 4, wherein the hydraulic actuator is a hydraulic cylinder having a reciprocatably driven rod extending from the hydraulic cylinder housing, and the locking device locks the rod against axial movement.

Claim 10

The rod locking device of claim 4, wherein the hydraulic actuator is a rotary actuator having a rotatably driven rod extending from the actuator housing, and the means for securing the locking ring also secures the locking ring against rotational movement with respect to the actuator housing to enable the locking device to lock the rod against rotational movement and comprises rotational locking means between the locking ring and the ring-contracting member and rotational locking means between the ring-contracting member and the actuator housing.

Claim 11

The rod locking device of claim 7, wherein the means for securing the locking ring comprises surfaces butting against both ends of the locking ring to prevent the locking ring from moving in both axial directions.

Claim 12

The rod locking device of claim 4, wherein the locking ring is made of metal.

Claim 13

The rod locking device of claim 1, wherein the outer surface of the locking ring consists essentially of an axially inclined surface and the inner surface of the locking ring grips the rod over the full axial dimension of the locking ring when contracted.

Claim 14

The rod locking device of claim 4, wherein the outer surface of the locking ring consists essentially of an axially inclined surface and the inner surface of the locking ring grips the rod over the full axial dimension of the locking ring when contracted.

Claim 15

The rod locking device of claim 11, wherein the locking ring has a slot extending the full axial dimension of the locking ring.

Claim 16

The rod locking device of claim 4, wherein the hydraulic pressure means includes a hydraulic chamber formed by a ring-like shaped cavity in a head extension placed against the hydraulic actuator and a circular extension of the ring-contracting member which reciprocably slides in the cavity, and seals for preventing the leakage of hydraulic fluid from the cavity, which seals are not in contact with the rod, and the locking ring inner surface is in direct contact with the rod without provisions for lubricants therebetween when the locking ring grips the rod.

Claim 17

The rod locking device of claim 4, wherein the relationship between the inner surface of the locking ring and the rod and between the outer surface of the locking ring and the inner surface of the ring-contracting member causes the locking ring to be self-tightening and self-releasing.

Claim 18

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.

Claim 19

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.

Claim 20

The rod locking device of claim 15, further including a cylindrical sleeve around each bolt for positioning the first plate, the cylindrical sleeves each being flattened on the outer surface facing the rod, whereby a larger spring can be positioned around the cylindrical spacer and between the bolts.

Claim 21

The rod locking device of claim 1, wherein the hydraulic actuator includes a head, cap, and cylindrical wall, and held together by a plurality of bolts which extend beyond the head, and the ring-contracting member includes a plurality of openings through which each extends one of the plurality of bolts, and the screw means comprises a plurality of nuts, each of which is threaded on one of the plurality of bolts and engages one end of the ring-contracting member to apply axial force to the ring-contracting member when the nuts are tightened.