LINEAR MOTION ENCODER

• US 3,867,037 A
• Filed: 08/29/1973
• Issued: 02/18/1975
• Est. Priority Date: 08/29/1973
• Status: Expired due to Term

• Current Assignee: Litke E. David
• Original Assignee: Litke E. David
• Inventors: Litke, E. David
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Godwin, Paul K.
• Application Number:
  US05/392,816
• Time in Patent Office: 538 Days
• Field of Search: 356/169,172 250/237 33/125C,1R
• US Class Current: 356/619
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/02 for measuring length, width or thickness G01B11/08 takes precedence
• CPC Class Codes: G01D 5/347 using displacement encoding scales

Abstract

An electro-optical encoder providing uniform high sensitivity measurement of the magnitude and direction of linear motion along a travel path. A scale is arranged for motion along a longitudinal track within an encoder housing and relative to a reticle fixed in the housing. The effects of shaft misalignment are minimized by a coupler which is resilient in directions transverse to the axis of scale travel, while being rigid along the axis of travel as the scale moves along a grooved track within the housing.

Claims

1. An electro-optical linear encoder comprising:

an elongated housing having a defined linear travel path therealong;

an elongated rigid scale within said housing and having a plurality of alternately light responsive and non-responsive segments in parallel array along the longitudinal axis of one surface thereof, said scale being movable longitudinally within said housing;

reticle means including a reticle fixed within said housing and having a plurality of alternately light responsive and nonresponsive segments formed in a parallel array along a longitudinal axis of one surface thereof, the length of said reticle means along said longitudinal axis being less than the length of said elongated scale;

sealing means affixed to said housing for substantially isolating the interior of said housing from the external environment;

means for mounting said scale and reticle means for relative motion therebetween and along a longitudinal travel path within said housing and including;

a drive member extending through said sealing means into said housing and arranged for bidirectional movement therethrough and for longitudinal motion relative to said reticle means; and

means operative to couple said scale to said drive member in rigid relationship along the longitudinal axis of relative motion of said scale and in resilient relationship in at least one plane transverse to said longitudinal axis;

means in said housing for directing light onto said scale and said reticle to provide a sensible fringe pattern; and

sensor means within said housing for detecting said fringe pattern and for providing electrical signals in response thereto.

2. An electro-optical linear encoder according to claim 1 and further comprising at least two bearing members affixed to respective top and bottom edges of said scale, said bearing members having at least one bearing surface contacting said housing and for mounting said scale in said housing to permit motion of said scale only along said longitudinal travel path.

3. An electro-optical linear encoder according to claim 1 and further including restoring means coupled to said drive member and operative to restore said scale to a desired position in the absence of a driving force.

4. An electro-optical linear encoder according to claim 2 wherein said at least one bearing surface of said bearing members includes a friction reducing material.

5. An electro-optical linear encoder according to claim 1 wherein said reticle means includes means for adjustably mounting said plurality of alternately light responsive and non-responsive segments in predetermined orientation relative to said alternately light responsive and non-responsive segments on said scale to provide a desired fringe pattern.

6. An electro-optical linear encoder according to claim 1 wherein said sealing means is disposed at one end of said housing, and said drive member extends along an axis parallel to said scale.

7. An electro-optical linear encoder according to claim 1 including first and second gauge means connected to said drive member and said housing and operative to measure a distance therebetween.

8. An electro-optical linear encoder comprising:

an elongated housing having a defined linear travel path therealong;

an elongated scale within said housing and having a plurality of alternately light responsive and non-responsive segments in parallel array along the longitudinal axis of one surface thereof, said scale being movable longitudinally within said housing;

reticle means including a reticle fixed within said housing and having a plurality of alternately light responsive and non-responsive segments formed in a parallel array along a longitudinal axis of one surface thereof;

sealing means affixed to said housing for substantially isolating the interior of said housing from the external environment;

means for mounting said scale and reticle means for relative motion therebetween and along a longitudinal travel path within said housing and including;

a drive member extending through said sealing means into said housing and arranged for bidirectional movement therethrough and for longitudinal motion relative to said reticle means; and

means operative to couple said scale to said drive member in rigid relationship along the longitudinal axis of relative motion of said scale and in resilient relationship in at least one plane transverse to said longitudinal axis and comprising a selectively resilient member coaxially disposed within a recess in said drive member to permit transverse motion of said coupling means within said recess;

means in said housing for directing light onto said scale and said reticle to provide a sensible fringe pattern; and

sensor means within said housing for detecting said fringe pattern and for providing electrical signals in response thereto.

9. An electro-optical linear encoder comprising:

an elongated housing having a defined linear travel path therealong;

an elongated scale within said housing and having a pluraliTy of alternately light responsive and non-responsive segments in parallel array along the longitudinal axis of one surface thereof, said scale being movable longitudinally within said housing;

reticle means including a reticle fixed within said housing and having a plurality of alternately light responsive and non-responsive segments formed in a parallel array along a longitudinal axis of one surface thereof;

sealing means disposed in a wall of said housing parallel to said scale for substantially isolating the interior of said housing from the external environment;

means for mounting said scale and reticle means for relative motion therebetween and along a longitudinal travel path within said housing and including;

a drive member extending along an axis orthogonal to said scale and through said sealing means into said housing and arranged for bidirectional movement therethrough and for longitudinal motion relative to said reticle means; and

means operative to couple said scale to said drive member in rigid relationship along the longitudinal axis of relative motion of said scale and in resilient relationship in at least one plane transverse to said longitudinal axis;

means in said housing for directing light onto said scale and said reticle to provide a sensible fringe pattern; and

sensor means within said housing for detecting said fringe pattern and for providing electrical signals in response thereto.

10. An electro-optical linear encoder comprising:

an elongated, sealed, rigid housing having a defined linear path therealong;

an elongated rigid scale, shorter than said housing and disposed for linear travel within said housing along said path and having a plurality of alternately light responsive and non-responsive segments in parallel array along the longitudinal axis of one surface thereof;

reticle means including a reticle adjustably mounted for precise rotational alignment in said housing in a predetermined fixed spaced relationship with said scale, said reticle having a plurality of alternately light responsive and non-responsive segments formed in a parallel array along a longitudinal axis of one surface thereof, the length of said reticle means along said longitudinal axis being less than the length of said elongated scale;

sealing means affixed to said housing for substantially isolating the interior of said housing from the external environment;

means for mounting said scale and said reticle and along a longitudinal travel path within said housing and including;

a drive member extending through said sealing means into said housing and arranged for bidirectional movement through said sealing means and for longitudinal motion relative to said reticle means; and

means operative to couple said scale to said drive member in rigid relationship along the longitudinal axis of relative motion of said scale and in resilient relationship in at least one plane transverse to said longitudinal axis and comprising a selectively resilient member coaxially disposed within a recess in said drive member to permit transverse motion of said coupling means within said recess;

means in said housing for directing light onto said scale and said reticle to provide a sensible fringe pattern; and

sensor means within said housing for detecting said fringe pattern and for providing electrical signals in response thereto.

11. An electro-optical linear encoder according to claim 10 and further including:

a reticle support member containing said reticle and being adjustably positionable for precise rotational alignment with respect to said scale;

at least one shim disposed between an outer surface of said housing and the confronting outer surface of said reticle holding member for determining the spatial separation between said reticle and said scale.

12. An electro-optical linear encoder according to claim 10 wherein said sealing means is disposed in a wall of said housing parallel to said scale and said drive member extends along an axis orthogonal to said scale.

13. An electro-optical linear encoder according to claim 10 wherein said sealing means is disposed at one end of said housing and said drive member extends along an axis parallel to said scale.