| CPC F15B 15/1466 (2013.01) [F15B 2015/1495 (2013.01); F15B 2015/206 (2013.01)] | 19 Claims |
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13. A fluid power actuator comprising:
a housing comprising:
a cylinder,
an end cap to seal a blind end of the cylinder, and
a rod end cap to guide a piston rod relative to the cylinder;
a piston rod assembly comprising:
a piston that travels within the cylinder in response to fluid pressure within the cylinder, the piston having a nut, and
the piston rod connecting the piston to an external load using a piston rod end, the piston rod being hollow to allow a screw to be partially or fully located inside the piston rod; and
a screw and nut assembly comprising:
the screw that couples the blind end of the cylinder to the nut, wherein the screw extends in part or in whole inside the piston rod, the screw and nut assembly being constructed to be non-self-locking and arranged to control movement of the piston relative to the housing, and
a brake that controls a position of the nut relative to the screw;
a load sensor that measures an axial load that the screw imposes on the housing and provides a load signal indicating the axial load; and
an electronic controller coupled with the load sensor and a fluid power pressure-controlled system that adjusts the fluid pressure on at least one side of the piston to adjust the axial load, wherein the electronic controller is constructed and arranged to:
receive, from the load sensor, the load signal indicating the measured axial load that the screw imposes on the housing, and
based on the load signal, direct an increase in the fluid pressure on a particular side of the piston, the increase in the fluid pressure on the particular side decreasing the axial load that the screw imposes on the housing;
wherein the screw includes an outer shaft portion disposed on an outer side of the housing, the brake being constructed and arranged to engage the outer shaft portion to restrict rotation of the screw relative to the nut.
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