Orthopedic simulator with integral load actuators

• US 20070169562A1
• Filed: 01/05/2007
• Published: 07/26/2007
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: MTS Systems Corporation (Illinois Tool Works Inc.)
• Original Assignee: MTS Systems Corporation (Illinois Tool Works Inc.)
• Inventors: Schulz, Bradley D., Fahrendorff, Harold F., Willis, Dennis J., Leska, Paul J.
• Granted Patent: US 7,762,147 B2
• Time in Patent Office: Days
• US Class Current: 73/798
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/468 Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76
• CPC Class Codes: G01N 2203/0222 Temperature
• CPC Class Codes: G01N 2203/0246 Special simulation of "in situ" conditions, scale models or dummies

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.

Claims

1. An integral load actuator comprising:

a housing;

a piston axially slideable within the housing;

hydrostatic bearings that float the piston; and

hydraulic fluid ports in the piston housing, with hydraulic fluid pressure in the hydraulic fluid ports controlling substantially frictionless extension and retraction of the piston with respect to the housing.

2. The actuator of claim 1, wherein the actuator is entirely seal-less.

3. The actuator of claim 2, wherein the piston is rotatable around a central longitudinal axis of the piston with extremely low torsional friction.

4. The actuator of claim 3, wherein the actuator includes a hydraulic shut-off valve that shuts off hydraulic pressure to the hydraulic fluid pressure ports.

5. The actuator of claim 4, further comprising thrust bearings at the axial ends of the housing.

6. An orthopedic simulator, comprising:

a plurality of test stations for each holding a test specimen; and

a plurality of load actuators, with a respective load actuator for each of the test stations, the load actuators being substantially frictionless and configured to apply loads to the test specimens at the test stations.

7. The simulator of claim 6, wherein the load actuators are hydraulically driven.

8. The simulator of claim 7, wherein the load actuators are simultaneously driven by hydraulic pressure to provide equal loads on the plurality of test specimens at the test stations.

9. The simulator of claim 8, wherein each load actuator has an individual shut-off valve to turn off the load actuator separately from the other load actuators.

10. The simulator of claim 9, wherein each load actuator is a vertical load actuator configured to apply vertical loads to a test specimen.

11. The simulator of claim 10, wherein each load actuator includes a housing and a piston axially slidable with the housing, hydrostatic bearings that float the piston, and hydraulic fluid ports that admit hydraulic fluid under pressure to control extension and retraction of the piston with respect to the housing.

12. The simulator of claim 11, wherein each load actuator is entirely seal-less.

13. The simulator of claim 12, wherein each piston is axially rotatable substantially frictionlessly.

14. The simulator of claim 13, wherein each load actuator has thrust bearings at the axial ends of the housing.

15. A spinal implant wear test machine, comprising:

a plurality of test stations configured to hold test specimens in position for application of vertical load forces on the test specimens; and

a plurality of vertical load actuators positioned relative to the test stations to apply the vertical load forces to the test specimens, each load actuator having a piston that is movable with extremely low linear friction to apply the vertical load forces.

16. The machine of claim 15, wherein the plurality of load actuators are commonly hydraulically driven to provide equal vertical loading of the test specimens across all of the load actuators.

17. The machine of claim 16, wherein the load actuators are hydrostatic and completely seal-less.

18. The machine of claim 17, wherein each load actuator has an individual shut-off valve to turn off the load actuator separately from the other load actuators.