Orthopedic simulator with integral load actuators
Inventors
Schulz, Bradley D. • Leska, Sr., Paul J. • Willis, Dennis J. • Fahrendorff, Harold F.
Assignees
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Publication Number
US-7762147-B2
Publication Date
2010-07-27
Expiration Date
Abstract
An orthopedic simulator is provided with a plurality of test stations for each holding a test specimen. A plurality of load actuators are provided, with a respective load actuator for each of the test stations. The load actuators are substantially frictionless and configured to apply loads to the test specimens at the test stations.
Core Innovation
The invention relates to an orthopedic simulator for applying loads to a test specimen, having multiple test stations. Each test station includes an integral, substantially frictionless load actuator that applies vertical load and, where provided, torsional or rotational load to the test specimen, and the simulator is configured to enable consistent and accurate loading across the test stations.
The actuator uses a seal-less hydrostatic piston that floats within a housing on hydrostatic bearings. Hydraulic fluid ports in the piston housing use hydraulic fluid pressure to control piston extension and retraction relative to the housing, thereby moving associated specimen holders, and the piston can be arranged to support piston rotation to provide rotational loading.
The simulator further includes specimen containment modules for remote handling and contamination reduction, and a centralized manifold for hydraulic or plumbing distribution. Each station can include built-in hydraulic shutoff via built-in hydraulic valves to stop individual actuators without stopping the overall machine, and motion is provided with multi-degree-of-freedom links and gimbals using low-lash bearings, with an x-y slide assembly supporting shear loading in low friction and lockable or floating modes.
Claims Coverage
The document includes four independent claims (clm-00001, clm-00010, clm-00014, clm-00015) that focus on hydrostatically floated piston actuators for load application, multi-station test machines with vertical and rotational loading, and independent per-station shutdown of actuator assemblies.
Hydrostatically floated piston with hydraulic pressure-controlled extension and retraction
A testing apparatus with a housing containing a piston axially slidable within the housing, where at least one hydrostatic bearing floats the piston relative to the housing and hydraulic fluid ports in the piston housing use hydraulic fluid pressure to control piston extension and retraction with respect to the housing, to move a first specimen holder toward and away from a second specimen holder.
Two-station test machine applying vertical and rotational loads through longitudinally movable, rotatable pistons and linkage rotation
A test machine with first and second test stations, each having a specimen holder assembly, and with a plurality of actuator assemblies that apply vertical load forces and rotational load forces through pistons movable along a longitudinal axis and rotatable about the longitudinal axis, where an actuator coupled to the plurality of pistons through a linkage assembly rotates the plurality of pistons to provide the rotational load forces.
Multi-station test machine with separately turn-off capable actuator housings
A test machine with a plurality of test stations and a plurality of actuator assemblies positioned relative to the test stations to apply vertical load forces and rotational load forces through pistons movable along a longitudinal axis, where each actuator housing has a device to turn off one of the actuator assemblies separately from one or more other actuator assemblies.
Dual-mode load test apparatus using linear piston motion plus piston rotation for specimen-relative rotation
A test apparatus having a first specimen holder and a second specimen holder, a housing with a piston coupled to the first specimen holder, one or more hydrostatic bearings between the piston and the housing, a first actuator assembly configured to actuate the piston along a longitudinal axis to move the first specimen holder toward or away from the second, and a second actuator assembly configured to rotate the piston about the longitudinal axis to rotate the first specimen holder relative to the second.
Across the independent claims, the core claim coverage centers on hydrostatically supported pistons in actuator housings with hydraulic fluid pressure controlling piston extension and retraction, and on test machine architectures that apply both vertical and rotational load forces through pistons that can be moved along a longitudinal axis and rotated, with optional per-actuator assembly turn-off capability and multi-station arrangements.
Stated Advantages
Minimizing friction-induced error by substantially frictionless extension and retraction.
Consistent and accurate vertical loading across stations by using hydraulic fluid port pressure to control piston extension and retraction.
Per-station shutdown by stopping individual actuators without halting the overall machine.
Documented Applications
Orthopedic wear/fatigue testing simulator architecture for applying loads to orthopedic specimens, including an ISO 18192 wear testing spinal implant wear test machine.
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