Length measuring device

• US 8,448,347 B2
• Filed: 10/13/2009
• Issued: 05/28/2013
• Est. Priority Date: 10/31/2008
• Status: Active Grant

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Affa, Alfred, Haunreiter, Johannes
• Primary Examiner(s): GUADALUPE, YARITZA
• Application Number:
  US13/125,638
• Publication Number:
  US 20110209352A1
• Time in Patent Office: 1,323 Days
• Field of Search: 33702-708
• US Class Current: 33/706
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices

Abstract

A length measuring device for measuring a relative position of two objects, the length measuring device including a scale in a housing and a scanning unit displaceable in a measuring direction X relative to the scale and the housing, wherein the scanning unit is disposed inside the housing and including a heat-generating electrical component. The length measuring device further including a thermal conduction path designed for transferring heat generated at the heat-generating electrical component to the housing.

Claims

1. A length measuring device for measuring a relative position of two objects, the length measuring device comprising:

a scale in a housing;

a scanning unit displaceable in a measuring direction X relative to said scale and said housing, wherein said scanning unit is disposed inside said housing and comprising a heat-generating electrical component; and

a thermal conduction path designed for transferring heat generated at said heat-generating electrical component to said housing.

2. The length measuring device as defined by claim 1, wherein said thermal conduction path is formed by a thermally conductive element;

and

wherein said thermally conductive element is coupled highly thermally conductively to said heat-generating electrical component and said thermally conductive element extends onward to said housing, in such a way that said thermally conductive element faces said housing with a slight gap so that heat generated at said heat-generating electrical component is transferred via said thermally conductive element to said slight gap and via said slight gap to said housing.

3. The length measuring device as defined by claim 2, wherein a two-dimensional region of said thermally conductive element is disposed facing an inner wall of said housing with said slight gap.

4. The length measuring device as defined by claim 3, wherein said two-dimensional region has an area of at least 200 mm², with a slight gap of less than 1 mm.

5. The length measuring device as defined by claim 4, wherein said two-dimensional region is a heat-conducting sheet metal.

6. The length measuring device as defined by claim 3, wherein said two-dimensional region is a heat-conducting sheet metal.

7. The length measuring device as defined by claim 2, wherein a portion of said thermally conductive element comprises an electrically insulating material.

8. The length measuring device as defined by claim 2, wherein said heat-generating electrical component is disposed on a circuit board;

and

said thermally conductive element comprises;

a first portion that leads from said heat-generating electrical component through said circuit board; and

a second portion that leads to said slight gap.

9. The length measuring device as defined by claim 8, wherein said first portion comprises a through hole plating.

10. The length measuring device as defined by claim 1, wherein said heat-generating electrical component is a sensor chip comprising:

scanning sensors for scanning said scale and generating scanning signals; and

an electrical circuit that processes said scanning signals into a measured position value.

11. The length measuring device as defined by claim 10, wherein said measured position value is furnished bit-serially by said sensor chip as an output signal in a form of a multi-digit digital code word.