SEALED LINEAR ENCODER

• US 3,816,003 A
• Filed: 03/12/1973
• Issued: 06/11/1974
• Est. Priority Date: 03/12/1973
• 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:
  US05/340,067
• Time in Patent Office: 456 Days
• Field of Search: 356/169,170 250/239,237G 33/125C
• US Class Current: 356/395
• CPC Class Codes: G01D 5/34753 Carriages; Driving or coupling means

Abstract

An electro-optical encoder providing uniform high sensitivity measurement of the magnitude and direction of linear motion even under adverse industrial conditions. A scale and reticle are arranged for relative motion and enclosed by a housing having a seal which allows lengthwise travel of a narrow blade coupled to the reticle without allowing foreign matter to enter the encoder. The effects of externally caused vibrations are minimized by a biased coupler which maintains the reticle in uniform engagement with the scale as it moves longitudinally relative to the scale along a track, formed by the scale surface and a smooth surface of the housing.

Claims

1. An electro-optical linear encoder comprising:

an elongated rigid housing;

an elongated scale, within said housing, having a plurality of alternately light responsive and non-responsive segments in parallel array along the longitudinal axis of one surface thereof and at least one first bearing surface thereon parallel to said longitudinal axis, along which an associated reticle means is caused to relatively move;

said housing providing a second bearing surface parallel to said longitudinal axis lying in a plane intersecting the plane of said at least one;

first bearing surface along which said associated reticle means is caused to relatively move;

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

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

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

elongated resilient sealing means affixed to and disposed longitudinally of said housing for substantially isolating the interior of said housing from the external environment; and

means for mounting said scale and reticle means for relative motion therebetween and along a longitudinal travel path within said housing defined by said first and second bearing surfaces and including;

a blade member extending through said resilient sealing means into said housing and arranged for longitudinal motion relative to said scale; and

coupling means including means operative to provide a biasing force to said reticle means, urging said reticle means into engagement with said first and second bearing surfaces and providing force components in the plane perpendicular to said longitudinal travel path;

said coupling means operative to couple said reticle means to said blade member in fixed relationship along said longitudinal travel path and resiliently in at least one plane transverse to said longitudinal travel path.

2. An electro-optical encoder according to claim 1 wherein said resilient sealing means includes first and second pairs of confronting strips of resilient material forming a double seal along the length of said housing.

3. An electro-optical encoder according to claim 1 wherein said resilient sealing means includes confronting strips of resilient material of closed cell foam construction resistant to the absorption of foreign matter.

4. An electro-optical linear encoder according to claim 1 wherein said reticle means includes:

a reticle holding member having at least two bearing surfaces including a first bearing surface in confronting association with said second Bearing surface, of said housing, and a second bearing surface in confronting association with said at least one first bearing surface of said scale;

said reticle holding member being adapted for relative motion along said travel path.

5. An electro-optical linear encoder according to claim 1 wherein said reticle means includes:

a reticle holding member adapted for relative motion with respect to said scale and along said travel path;

said reticle being mounted on said reticle holding member and having said parallel array of alternately light responsive and non-responsive segments in spaced confronting relationship with the parallel array of alternately light responsive and non-responsive segments on said scale;

said sensor means being mounted on said reticle holding member for detection of light passing through said respective parallel arrays.

6. An electro-optical linear encoder according to claim 1 wherein said plurality of alternate light responsive and non-responsive segments are alternately light transmissive and opaque.

7. An electro-optical encoder according to claim 1 having guide means in said blade member and cooperative with a confronting groove along the length of said housing to prevent said reticle means from becoming misaligned in the event that the blade is temporarily not otherwise fixed externally to said housing in a suitable position relative to said housing.

8. An electro-optical linear encoder according to claim 5 wherein said light directing means includes:

at least one light source; and

a light source mounting bracket;

said light source mounting bracket being affixed to said reticle holding member for positioning of said at least one light source on the side of said scale opposite from said reticle holding member and in spaced registration with respective parallel arrays of alternately light responsive and non-responsive segments of said scale and reticle and with said photosensors.

9. An electro-optical linear encoder according to claim 8 wherein said sensor means includes a plurality of photosensors arranged in parallel spaced relationship and operative to provide an output voltage in response to light received from said arrays.

10. An electro-optical linear encoder according to claim 1 wherein grooves are provided within said housing and disposed along the longitudinal axis thereof and wherein said sealing resilient means are disposed within said grooves.

11. An electro-optical linear encoder according to claim 1 wherein said scale and said reticle each include at least first and second parallel arrays of alternately light responsive and non-responsive segments;

said first and second parallel arrays representing respective first and second measuring systems and wherein said encoder is operative to provide at least first and second output indications of relative movement expressed in accordance with said measuring systems.

12. An electro-optical linear encoder according to claim 1 wherein said means operative to provide a biasing force to said reticle means comprises a member having a first elongate portion extending generally in parallel spaced relation to the longitudinal axis of said reticle means and a second elongate portion shorter than said first portion and extending generally transversely to the longitudinal axis of said reticle means.

13. An electro-optical linear encoder according to claim 12 wherein said reticle means includes an angled projection coupled to said second elongate portion and operative to resolve said biasing force applied to said reticle means into components urging said reticle means into engagement with said first and second bearing surfaces.