Position measuring device

• US 4,982,508 A
• Filed: 06/22/1989
• Issued: 01/08/1991
• Est. Priority Date: 06/29/1988
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Weiss, Josef, Schopf, Reinhold, Schmitt, Walter, Nelle, Gunther
• Primary Examiner(s): Haroian, Harry N.
• Application Number:
  US07/370,273
• Time in Patent Office: 565 Days
• Field of Search: 33/DIG. 19, 33/702, 33/703, 33/704, 33/705, 33/706, 33/707, 33/708
• US Class Current: 33/702
• CPC Class Codes: G01B 5/0014 due to temperature on machine tools B23Q11/0003
• CPC Class Codes: G01D 2205/50 Grounding or electrostatically shielding a position sensor or encoder
• CPC Class Codes: G01D 5/34761 Protection devices, e.g. caps; Blowing devices

Abstract

A position measuring device including a scale carrier member and a scanning device for scanning the scale. A temperature difference is generated between the scale carrier member and/or the scanning device, on the one hand, and a housing surrounding the scale carrier member and the scanning device, on the other hand. The temperature difference ensures that condensate is always precipitated on the colder housing.

Claims

1. In a position measuring device including a scale carrier member for a scale and a scanning device for scanning the scale, the improvement comprising means for generating a temperature difference between one of the scale carrier member and the scanning device, on the one hand, and the immediate surrounding of the scale carrier member and the scanning device, on the other hand, for producing a condensate.

2. The position measuring device according to claim 1, wherein the means for generating the temperature difference comprises heating means for the scale carrier member.

3. The position measuring device according to claim 2, wherein the scale carrier member comprises heating lines for supplying heating energy.

4. The position measuring device according to claim 1, wherein the means for generating the temperature difference comprises heating means for the scanning device.

5. The position measuring device according to claim 1, wherein the means for generating a temperature difference is a heating line in the scale.

6. The position measuring device according to claim 2, wherein the heating means comprises means for adjusting the dimensions of the scale carrier member.

7. The position measuring device according to claim 4, wherein the scanning device comprises heating lines, and sliding contacts for supplying heating current to the heating lines.

8. The position measuring device according to claim 2, the heated scale carrier member having ends, comprising fastening elements for tightly clamping the ends of the scale carrier member.

9. The position measuring device according to claim 8, comprising supply lines for supplying the heating current through the fastening elements.

10. The position measuring device according to claim 1, comprising means for enclosing the position measuring device.

11. The position measuring device according to claim 10, wherein the means for enclosing the position measuring device is a housing, the means for generating the temperature difference being cooling means for the housing.

12. The enclosed position measuring device according to claim 11, wherein the cooling means comprises at least one thermocouple for creating at least one cold pole on the housing.

13. The enclosed position measuring device according to claim 12, wherein the thermocouple is a Peltier element.

14. The enclosed position measuring device according to claim 11, wherein the housing defines at least one cooled condensation space.

15. The enclosed position measuring device according to claim 14, wherein the condensation space is adapted to be cooled by a coolant circulation system of a machine on which the position measuring device is mounted.

16. The enclosed position measuring device according to claim 14, comprising at least one Peltier element for cooling the condensation space.

17. The enclosed position measuring device according to claim 14, wherein the condensation space includes means for cooling the space by means of CO₂ snow.

18. The enclosed position measuring device according to claim 11, comprising a moisture exchanger on the housing.

19. The enclosed position measuring device according to claim 14, comprising a moisture exchanger in the condensation space.

20. The enclosed position measuring device according to claim 18, wherein the moisture exchanger is a wick.

21. The enclosed position measuring device according to claim 19, wherein the moisture exchanger is a wick.

22. The enclosed position measuring device according to claim 10, comprising means for chemically binding condensate produced by the temperature difference.

23. The enclosed position measuring device according to claim 10, comprising means for physically binding condensate produced by the temperature difference.

24. The enclosed position measuring device according to claim 23, wherein the means for physically binding the condensate comprises exchangeable silica gel capsules.

25. The enclosed position measuring device according to claim 14, wherein a single condensation space is provided for a plurality of position measuring devices.

26. The enclosed position measuring device according to claim 10, wherein the means for enclosing the position measuring device comprises an inner housing having a low thermal conductivity and an outer housing having a high thermal conductivity.

27. The enclosed position measuring device according to claim 26, wherein the inner housing is of plastic material and the outer housing is of aluminum.

28. The enclosed position measuring device according to claim 26, wherein the inner housing defines openings for compensating vapor pressures between the inner housing and the outer housing.

29. The enclosed position measuring device according to claim 26, wherein the outer housing defines openings for discharging condensate.

30. The enclosed position measuring device according to claim 26, wherein the inner housing and the outer housing comprise longitudinal slots, sealing lips being arranged in the shape of a V for sealing the longitudinal slots, and a drive member extending through the longitudinal slots for connecting the scanning device to an assembly member.

31. The enclosed position measuring device according to claim 30, wherein the longitudinal slots are arranged in alignment with each other, wherein the drive member extending through the longitudinal slots is a straight member.

32. The enclosed position measuring device according to claim 30, wherein the longitudinal slots are offset at an angle relative to each other, wherein the drive member extending through the sealing lips is a member which is bent several times.

33. The enclosed position measuring device according to claim 26, the outer housing having an interior, the inner housing having fastening elements for fastening the inner housing to the interior of the outer housing.

34. The enclosed position measuring device according to claim 33, wherein the fastening elements comprise projections on the inner housing and adjusting screws on the outer housing for contacting the inner housing.

35. The position measuring device according to claim 1, wherein the means for generating the temperature difference comprises a thermal insulating unit.

36. The position measuring device according to claim 1, wherein the means for generating the temperature difference comprises a temperature adjusting unit.

37. The position measuring device according to claim 35, comprising a housing for the carrier member including the scale and for the scanning device, wherein the thermal insulating unit is an outer insulating layer which surrounds the housing.

38. The position measuring device according to claim 35, comprising a housing for the carrier member including the scale and for the scanning device, wherein the thermal insulating unit is an inner insulating layer on inner surfaces of the housing.

39. The position measuring device according to claim 35, wherein the thermal insulating unit comprises a housing for the carrier member including the scale and for the scanning device, wherein the housing has a low thermal conductivity.

40. The position measuring device according to claim 36, wherein the temperature adjusting unit comprises a U-shaped middle portion having two ends and bores extending in longitudinal direction, plate-shaped end portions arranged at the two ends of the middle portion, each end portion defining at least one collection bore, wherein the temperature adjusting unit surrounds a housing for the carrier member including the scale and for the scanning device.

41. The position measuring device according to claim 36, wherein the temperature adjusting unit forms a housing for the carrier member including the scale and for the scanning device.

42. The position measuring device according to claim 36, wherein the temperature adjusting unit is composed of several individual members.

43. The position measuring device according to claim 37, wherein the housing defines a longitudinal slot, two pairs of sealing lips being provided for sealing the longitudinal slots, a drive member of a material having a low thermal conductivity for the scanning device extending through the sealing lips.

44. The position measuring device according to claim 40, wherein the housing defines a longitudinal slot, two pairs of sealing lips being provided for sealing the longitudinal slots, a drive member of a material having a low thermal conductivity for the scanning device extending through the sealing lips.

45. The position measuring device according to claim 35, wherein the thermal insulating unit is composed of several individual members.

46. The position measuring device according to claim 45, wherein the individual members have different lengths.

47. The position measuring device according to claim 40, comprising means for conducting liquid through the bores of the middle portion such that the liquid flows through the bores alternatingly in different directions.

48. In a position measuring device including a scale carrier member for a scale and a scanning device for scanning the scale, the improvement comprising means for generating a temperature difference between the scale carrier member and the scanning device, on the one hand, and the immediate surrounding of the scale carrier member and the scanning device, on the other hand, for producing a condensate.

49. The position measuring device according to claim 48, wherein the means for generating the temperature difference comprises heating means for the scale carrier member.

50. The position measuring device according to claim 49, wherein the scale carrier member comprises heating lines for supplying heating energy.

51. The position measuring device according to claim 48, wherein the means for generating the temperature difference comprises heating means for the scanning device.

52. The position measuring device according to claim 48, wherein the means for generating a temperature difference is a heating line in the scale.

53. The position measuring device according to claim 49, wherein the heating means comprises means for adjusting the dimensions of the scale carrier member.

54. The position measuring device according to claim 53, wherein the scanning device comprises heating lines, and sliding contacts for supplying heating current to the heating lines.

55. The position measuring device according to claim 48, the heated scale carrier member having ends, comprising fastening elements for tightly clamping the ends of the scale carrier member.

56. The position measuring device according to claim 55, comprising supply lines for supplying the heating current through the fastening elements.