Systems of recording piston rod position information in a magnetic layer on a piston rod

• US 7,034,527 B2
• Filed: 10/25/2005
• Issued: 04/25/2006
• Est. Priority Date: 05/06/2003
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Low, Thomas P., Clark, C. Bruce, Pelrine, Ronald E., Eckerle, Joseph S., Smith, Chris
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US11/258,308
• Publication Number:
  US 20060038556A1
• Time in Patent Office: 182 Days
• Field of Search: 324/207.25, 324/213
• US Class Current: 324/207.25
• CPC Class Codes: F15B 15/2846 using detection of markings, e.g. markings on the piston rod
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: F16F 9/3221 of piston rods
• CPC Class Codes: F16F 9/3292 Sensor arrangements
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G11B 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: H01F 10/16 containing cobalt H01F10/126 , H01F10/13 take precedence

Abstract

Described are systems of recording piston rod position information in a magnetic layer on the piston rod. A piston rod moving with respect to a cylinder has a magnetically hard layer formed thereon to provide a recording medium. A magnetic pattern is recorded in the magnetically hard layer. A magnetic field sensor senses the recorded magnetic pattern while the piston rod is moving with respect to the cylinder and generates signals in response to the magnetic pattern that are used to determine an instantaneous position of the piston rod.

Claims

1. A piston rod position sensing system, comprising:

a cylinder;

a piston rod arranged in the cylinder for movement with respect thereto;

a magnetically hard layer formed on the piston rod to provide a recording medium, a magnetic pattern being recorded in the magnetically hard layer; and

a magnetic field sensor located in the cylinder to sense the recorded magnetic pattern while the piston rod is moving with respect to the cylinder and to generate signals in response to the sensed magnetic pattern that are used to determine an instantaneous position of the piston rod.

2. The piston rod position sensing system of claim 1, further comprising a magnetically soft layer disposed between the magnetically hard layer and the piston rod.

3. The piston rod position sensing system of claim 1, further comprising a non-magnetic layer disposed between the magnetically hard layer and the piston rod.

4. The piston rod position sensing system of claim 1, further comprising a protective layer disposed on the magnetically hard layer.

5. The piston rod position sensing system of claim 4, wherein the protective layer includes chromium.

6. The piston rod position sensing system of claim 1, wherein the magnetically hard layer includes cobalt.

7. The piston rod position sensing system of claim 1, wherein the magnetic pattern includes a plurality of binary codes, each binary code being uniquely associated with one piston rod position.

8. The piston rod position sensing system of claim 1, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending along a length of the piston rod and diverging away from the first magnetized line.

9. The piston rod position sensing system of claim 8, wherein an area bounded by the first and second magnetized lines is magnetized.

10. The piston rod position sensing system of claim 1, further comprising circuitry for computing one of a velocity and a direction of motion of the piston rod from readings of the magnetic pattern.

11. A cylinder, comprising:

a piston;

a rod extending axially from the piston; and

a magnetically hard layer formed on the piston rod to provide a recording medium for magnetically storing bits of information along a length of the rod.

12. The cylinder of claim 11, further comprising a magnetic pattern recorded in the magnetically hard layer.

13. The cylinder of claim 12, wherein the magnetic pattern includes a plurality of binary codes, each binary code being uniquely associated with one position along a length of the piston rod.

14. The cylinder of claim 12, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending helically along a length of the piston rod.

15. The cylinder of claim 14, wherein an area between the first and second magnetized lines is magnetized.

16. The cylinder of claim 11, further comprising a magnetically soft layer disposed between the magnetically hard layer and the magnetic substrate of the rod.

17. The cylinder of claim 11, further comprising a non-magnetic layer disposed between the magnetically hard layer and the surface of the piston rod.

18. The cylinder of claim 11, further comprising a protective layer disposed on the magnetically hard layer.

19. The cylinder of claim 18, wherein the protective layer includes chromium.

20. The cylinder of claim 11, wherein the magnetically hard layer includes cobalt.