Length measuring apparatus

• US 5,205,049 A
• Filed: 09/26/1991
• Issued: 04/27/1993
• Est. Priority Date: 10/05/1990
• Status: Expired due to Term

• Current Assignee: RSF Elektronik GmbH (Dr. Johannes Heidenhain GmbH)
• Original Assignee: RSF Elektronik GmbH (Dr. Johannes Heidenhain GmbH)
• Inventors: Rieder, Heinz, Schwaiger, Max
• Primary Examiner(s): Will, Thomas B.
• Application Number:
  US07/766,635
• Time in Patent Office: 579 Days
• Field of Search: 33/703, 33/705, 33/704, 33/700, 33/706, 33/707, 33/708
• US Class Current: 33/703
• CPC Class Codes: G01D 5/347 using displacement encoding scales

Abstract

A length measuring apparatus comprises a measuring device for detecting the position of a marker along a measuring path. The measuring device and the marker are encapsulated in a hermetically sealed housing. A follow-up device is provided for moving the marker to a predetermined position of registration relative to a detectable point, which is disposed outside the housing and is movable along a path which is parallel to and laterally aligned with the measuring path. The follow-up device comprises a device for establishing a non-contacting link between the detectable point and the marker. To provide such an apparatus which has a relatively simple design and a low susceptibility to disturbance and can achieve a high accuracy of measurement. The apparatus comprises a strip that is trained around reversing end pulleys and has a course that extends along the measuring path. The marker is carried by the course. The strip is adapted to be driven by the follow-up device and is provided with a measuring scale and in the housing extends past a stationary reader for reading the measuring scale.

Claims

1. In a length measuring apparatus for indicating the position of a detectable point on a member movable to move said detectable point along a first linear path, which apparatus comprises

a hermetically sealed housing,

a marker mounted within said housing to be movable along a predetermined linear measuring path having opposite ends,

said housing being adapted to be mounted so that said measuring path is parallel to and laterally aligned with said first path,

follow-up means for moving said marker along said measuring path to a predetermined position of registration relative to said detectable point, which follow-up means comprises means for establishing a non-contacting link between said detectable point and said marker, and

measuring means mounted within said housing for indicating the position of said marker along said measuring path,

the improvement comprising

two rotatably mounted rollers disposed in said housing beyond opposite ends of said measuring path and a strip extending between and around said rollers in contact therewith and having a tensioned course which extends along said measuring path and carries said marker,

said follow-up means comprises drive means operatively connected to said strip and operable to move said marker by means of said strip along said measuring path, and means for detecting the extent and direction of any deviation of said marker from said predetermined position of registration relative to said detectable point, the detecting means transmitting a control signal to the drive means to move the strip and keep the marker at the predetermined position of registration relative to the detectable point.

2. The improvement set forth in claim 1, wherein said drive means are operatively connected to said strip by means of at least one of said rollers.

3. The improvement set forth in claim 2, wherein

said strip consists of an endless belt trained around said two rollers, and

said drive means are operatively connected to one of said rollers.

4. The improvement set forth in claim 2, wherein said

strip is wound on both said rollers and

said drive means are operatively connected to both said rollers.

5. The improvement set forth in claim 2, wherein

said measuring means comprises a resolver operatively connected to said one roller which is operatively connected to said drive means.

6. The improvement set forth in claim 5, wherein said resolver is incorporated in said one roller.

7. The improvement set forth in claim 1, wherein

the tensioned course of said strip is provided with a measuring scale extending along said measuring path, forming part of said measuring means,

said measuring means further including a stationary reader for reading said measuring scale being mounted within said housing and

said tensioned course provided with said measuring scale extends past said reader.