Coordinate positioning apparatus

• US 4,777,818 A
• Filed: 06/25/1986
• Issued: 10/18/1988
• Est. Priority Date: 05/04/1984
• Status: Expired due to Term

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: McMurtry, David R.
• Primary Examiner(s): Noland, Tom
• Application Number:
  US06/882,972
• Time in Patent Office: 846 Days
• Field of Search: 73/1 J, 73/1 R, 33/503, 33/556, 33/558, 33/559, 33/561
• US Class Current: 73/1.79
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 3/30 Bars, blocks, or strips in which the distance between a pair of faces is fixed, although it may be preadjustable, e.g. end measure, feeler strip
• CPC Class Codes: G01B 7/004 for measuring coordinates of points

Abstract

A device for checking the accuracy of coordinate positioning apparatus which includes a support, a head and components for measuring the coordinate position of the head relative to the support. The device comprises a bar, a connecting member movably securable to the support, a first universal pivot for supporting the bar at one end on the connecting member, a second universal pivot adapted for establishing a universal pivotable connection between the other end of the bar and the head, and a switch for producing a signal responsive to the head attaining a predetermined location in a coordinate field of the apparatus.

Claims

1. A method of checking the accuracy of orthogonal coordinate positioning apparatus, said apparatus comprising a support, a head supported for three-dimensional movement relative to said support, and continually operable measuring means for measuring the position of said head in terms of three orthogonal coordinates, said method comprising the steps of

providing a test bar having a given fixed length;

universally pivotally connecting one end of said bar to said support and the other end of said bar to said head;

automatically and sequentially moving said head through a plurality of stand-off locations situated about the connection of said bar to said support, said bar undergoing a corresponding angular movement by virtue of its connection to said head;

upon attainment of each said stand-off location moving said head relative to said one end of said bar into a test location; and

at each said test location measuring the coordinate position of said head as determined by the length of said bar between the ends thereof.

2. A method according to claim 1 comprising automatically generating a signal responsive to said head attaining any said test location ahd effecting a reading of said measuring means in response to said signal.

3. A method according to claim 1 wherein the movement of said head takes place relative to said bar.

4. A method according to claim 1 wherein said signal is generated in response to attainment of any said test position during said movement.

5. A device for checking the accuracy of coordinate positioning apparatus, said apparatus comprising a support, a head supported for three-dimensional movement relative to said support, and means for measuring the coordinate position of said head relative to said support, wherein said device comprises

a bar;

a connecting member removably securable to said support;

first universal pivot means for supporting said bar at one end thereof on said connecting member;

second universal pivot means adapted for establishing a universal pivotal connection between the other end of said bar and said head; and

switch means for producing a signal responsive to said head attaining a predetermined location in a coordinate field of said apparatus.

6. A device according to claim 5 wherein said switch means for producing said signal comprise electric circuit means provided on said head, a member supported on said head for relative movement between first and second positions, means responsive to said member moving between said first and second positions for changing the electrical state of said circuit means, and means for moving said member between said positions in response to the relative movement between said head and said first pivot means.

7. A device according to claim 5 including lost-motion means arranged to permit relative motion between said head and said first pivot means while said head is connected to said bar, and means responsive to said relative motion for producing said signal.

8. A device according to claim 7 wherein said lost-motion means comprise an element connected to said head, a guide means provided on said bar and arranged to guide said element for universal pivotal motion relative to said bar and for linear motion thereon in the direction of the length thereof.

9. A device according to claim 8 comprising an abutment provided on said bar and engageable by said element during said linear motion thereof, and means responsive to said element engaging said abutment for producing said signal.

10. A device according to claim 8 including means permitting disengagement between said element and said guide means.

11. A device according to claim 8 including confronting surface means provided respectively on said element and said guide means, said surface means being configured to constitute a kinematic support between said element and said bar.

12. A device according to claim 7 wherein said lost-motion means comprise means defining a pair of surfaces extending in the direction of the length of said bar and being convergent in the direction transverse to the length of said bar, and a spherical element situated between said convergent surfaces and connected to said head.

13. A device according to claim 5 wherein said first pivot means comprise a head provided on one of said bar and said mounting, and a socket provided on the other one of said bar and said mounting and being engageable with said head.

14. A device according to claim 13 wherein one of said socket and said head constitutes a spherical surface and the other one of said socket and said head comprises three surface elements adapted to engage said spherical surface.

15. A device according to claim 13 wherein said head constitutes a spherical surface and is provided on said mounting.

16. A device for checking the accuracy of coordinate positioning apparatus, said apparatus comprising a support, a head supported for three-dimensional movement relative to said support, and means for measuring the coordinate position of said head relative to said support, said device comprising

a bar;

a connecting member removably securable to said support;

first universal pivot means for supporting said bar at one end thereof on said connecting member;

second universal pivot means adapted for establishing a universal pivotal connection between said other end of the bar and said head;

lost motion means provided on said bar for accommodating relative motion of said first and second pivot means between first and second positions spaced in the direction of the length of the bar; and

switching means for producing a signal responsive to said first and second pivot means attaining one of said positions.

17. A device for checking the accuracy of coordinate positioning apparatus having a support, a head supported for three-dimensional movement relative to said support, and means for measuring the coordinate position of said head relative to said support, said device comprising

a bar;

a connecting member removably securable to said support;

first universal pivot means for supporting the bar at one end thereof on said connecting member;

second universal pivot means adapted for establishing a universal pivotal connection between the other end of said bar and said head;

lost motion means provided between the second pivot means and said other end of the bar, said lost motion means including first and second relatively movable members adapted to accommodate relative motion of the first and second pivot means between first and second positions, and further including a stop provided at one of said members for engagement by the other member for limiting said relative motion; and

a switch adapted for producing a signal responsive to said engagement.

18. A device for checking the accuracy of coordinate positioning apparatus having a support, a head supported for three-dimensional movement relative to said support, and means for measuring the coordinate position of said head relative to said support, said device comprising

a bar;

a first connecting member connectable to said support;

first universal pivot means for connecting said one end of the bar to said first connecting member;

a second connecting member connectable to said head;

second universal pivot means for connecting the other end of said bar to said second connecting member;

lost motion means provided on said bar for accommodating relative motion of said first and second pivot means between first and second positions spaced in the direction of the length of said bar; and

switch means for producing a signal responsive to said first and second pivot means attaining one of said first and second positions.

19. A device according to claim 18 wherein said switch means is provided at said second connecting member.

20. The method of using the apparatus and device claimed in claim 19 comprising the steps of:

(a) securing said first connecting member to said support;

(b) securing said second connecting member to said head;

(c) moving said head by means of said first and second universal pivot means to adopt the second one of said positions;

(d) moving said head by means of said first and second universal pivot means to adopt the first of said positions thereby generating said signal; and

(e) measuring the coordinate position of said head at the instant said signal is generated.

21. The method of using the apparatus and device claimed in claim 18 comprising the steps of:

(a) securing said first connecting member to said support;

(b) securing said second connecting member to said head;

(c) moving said head by means of said first and second universal pivot means to adopt the second one of said positions;

(d) moving said head by means of said first and second universal pivot means to adopt the first of said positions thereby generating said signal; and

(e) measuring the coordinate position of said head at the instant said signal is generated.

22. A device for checking the accuracy of coordinate positioning apparatus, said apparatus comprising a support, a head movable relative to said support, a stylus having an end connecting to said head and a free end portion, and means for generating a signal when a force is applied to said free end portion, said device comprising

a bar;

first pivot means for supporting said bar at one end thereof on said support for universal pivotal motion relative thereto;

means defining two guide surfaces provided at the other end of said bar and extending in the direction of the length thereof; and

second pivot means permitting universal pivotal motion between said guide surfaces and said free end portion, said guide surfaces being engageable with said free end portion at opposite sides thereof so as to be slidable relative thereto in the direction of the length of the bar thereby allowing relative motion of said first and second pivot means between first and second positions; and

a stop provided at an end of the guide surfaces for engagement by said free end portion thereby effecting said force.

23. The method of using the apparatus and device claimed in claim 22 comprising the steps of:

(a) securing said first connecting member to said support;

(b) securing said second connecting member to said head;

(c) moving said head by means of said first and second universal pivot means to adopt the second one of said positions;

(d) moving said head by means of said first and second universal pivot means to adopt the first of said positions thereby generating said signal; and

(e) measuring the coordinate position of said head at the instant said signal is generated.

24. A device for checking the accuracy of coordinate positioning apparatus, said apparatus comprising a support, a head moveable relative to said support, a stylus having one end connected to said head and a spherical sensing element provided at the other end, and means for generating a signal when a force is applied to said sensing element, said device comprising

a bar;

first pivot means for supporting the bar at one end thereof on said support for universal pivotal motion relative thereto;

a pair of elongate guide members provided at the other end of said bar, said guide members being spaced apart so as to be engageable along guide surfaces thereof with said stylus at opposite sides thereof, second pivot means permitting universal pivotal motion between the guide surfaces and the spherical sensing element, the guide surfaces being also engageable with said spherical sensing element so as to be slidable thereon in the direction of their length thereby allowing relative motion of said first and second pivot means between first and second positions, said guide surfaces also being supportable on said spherical sensing element so as to allow said universal pivotal motion by virtue of the spherical shape of said sensing element; and

a stop provided at an end of said guide surfaces for engagement by said sensing element thereby effecting said force.

25. A device according to claim 24 wherein said stop is fixed in relation to the bar, and said means for sensing said force is provided at said one end of the stylus.

26. The method of using the apparatus and device claimed in claim 25 comprising the steps of:

(a) securing said first connecting member to said support;

(b) securing said second connecting member to said head;

(c) moving said head by means of said first and second universal pivot means to adopt the second one of said positions;

(d) moving said head by means of said first and second universal pivot means to adopt the first of said positions thereby generating said signal; and

(e) measuring the coordinate position of said head at the instant said signal is generated.

27. The method of using the apparatus and device claimed in claim 24 comprising the steps of:

(a) securing said first connecting member to said support;

(b) securing said second connecting member to said head;

(c) moving said head by means of said first and second universal pivot means to adopt the second one of said positions;

(d) moving said head by means of said first and second universal pivot means to adopt the first of said positions thereby generating said signal; and

(e) measuring the coordinate position of said head at the instant said signal is generated.

28. Coordinate positioning apparatus adapted for checking the accuracy thereof comprising

a head supported for three-dimensional movement relative to said support;

means for measuring the coordinate position of said head relative to said support;

a bar;

first universal pivot means connected between one end of said bar and said support;

second universal pivot means connected between the other end of said bar and said head;

lost motion means for accommodating relative motion of said first and second universal pivot means between positions spaced in the direction of the length of said bar; and

switch means for producing a signal responsive to said first and second pivot means attaining one of said positions.