Six axis machine tool

• US 5,354,158 A
• Filed: 02/20/1992
• Issued: 10/11/1994
• Est. Priority Date: 09/01/1989
• Status: Expired due to Fees

• Current Assignee: Kearney & Trecker Corp. (Maxcor, Inc.)
• Original Assignee: Kearney & Trecker Corp. (Maxcor, Inc.)
• Inventors: Sheldon, Paul C., Ostby, Lyle D., Konkel, Bruce P., Kirkham, Edward E.
• Primary Examiner(s): BRIGGS, WILLIAM R
• Application Number:
  US07/835,949
• Time in Patent Office: 964 Days
• Field of Search: 409/145, 409/164, 409/80, 409/131, 409/132, 409/183, 409/201, 409/204, 409/212, 409/216, 409/235, 29/36, 29/39, 29/40, 408/129, 408/130, 408/234, 408/236, 901/21, 901/22, 901/23, 901/28, 901/29, 434/29, 434/58, 248/371, 248/398, 248/631, 248/652, 248/653, 248/654, 414/735, 74/479
• US Class Current: 409/201
• CPC Class Codes: B23Q 1/5462 with one supplementary sliding pair
• CPC Class Codes: B23Q 11/0032 Arrangements for preventing or isolating vibrations in parts of the machine B23B29/022, B23D47/005 take precedence; means for damping or suppressing vibrations, in general F16F
• CPC Class Codes: B23Q 17/24 using optics or electromagnetic waves
• CPC Class Codes: B23Q 5/40 by feed shaft, e.g. lead screw
• CPC Class Codes: B25J 17/0216 comprising a stewart mechanism
• CPC Class Codes: B25J 9/1623 Parallel manipulator, Stewart platform, links are attached to a common base and to a common platform, plate which is moved parallel to the base
• CPC Class Codes: G05B 19/231 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: G05B 19/4015 going to a reference at the beginning of machine cycle, e.g. for calibration
• CPC Class Codes: G05B 19/4086 Coordinate conversions; Other special calculations
• CPC Class Codes: G05B 2219/41309 Hydraulic or pneumatic drive
• CPC Class Codes: G05B 2219/41481 Divide command, block in subcommands, subblocks
• CPC Class Codes: G05B 2219/49257 Six or more linear drives to position x y z table
• CPC Class Codes: Y10T 403/32008 Plural distinct articulation axes
• CPC Class Codes: Y10T 403/32606 Pivoted
• CPC Class Codes: Y10T 403/32861 T-pivot, e.g., wrist pin, etc.
• CPC Class Codes: Y10T 403/32918 fork and tongue
• CPC Class Codes: Y10T 408/91 Machine frame
• CPC Class Codes: Y10T 409/304536 including means to infeed work to cutter
• CPC Class Codes: Y10T 409/307672 Angularly adjustable cutter head
• CPC Class Codes: Y10T 409/308512 Compound angular adjustment
• CPC Class Codes: Y10T 409/309576 : Machine frame

Abstract

A machine such as a machine tool includes a pair of spaced platforms. One platform (11, 31, 185, 72, 159, 142) may mount an operator such as a tool in a spindle and the other platforms (10, 20, 180, 170, 144, 163) may mount an object such as a workpiece. The spaced platforms are joined by six powered and extensible legs (20-25, 40-45, 64-69, 145-150, 166, 182-84, 187-89) joined to the respective platforms by universal joints. The length of the legs is individually manipulated to vary the position of the platforms and, therefore, the object and operator relative to each other in six axes. The powered legs may be hydraulic cylinders (20-25) or recirculating ball screw driven (195, 197, 198). The distance between the spaced platforms may be measured by separate extensible instrument arms (130, 131, 171) which join the platforms. The instrument arms may use a digital position device (238, 240) to measure the extension and contraction of the instrument arms or may use a laser interferometer (267) for that purpose. The changes in the length of the instrument arms may be used to generate signals that control the extension and contraction of the powered legs. A method is also disclosed for converting part program coordinate block instructions into instructions for varying the length of the powered legs.

Claims

1. A machine tool for locating a tool relative to a workpiece, comprising the combination of:

a pair of spaced supports, the tool being located with respect to one of the supports and the workpiece being located with respect to the other of the supports;

six leg members with each leg member being joined at a first point to one of the supports and being joined to the other support at a second point that is spaced along the leg member from the first point, the six leg members being arranged in circumferentially sequential pairs with the leg members of certain of the pairs crossing each other; and

means for individually manipulating at least certain of the leg members to vary the position of the points of such leg members relative to each other.

2. A machine tool in accordance with claim 1 together with control means for coordinating said manipulating means for at least some of the leg members.

3. A machine tool in accordance with claim 1 wherein a first of said supports defines a base for the machine tool and the other support is held above the first support by the six leg members.

4. A machine tool for locating a tool relative to a workpiece, comprising the combination of:

a pair of spaced supports, the tool being located with respect to one of the supports and the workpiece being located with respect to the other of the supports;

six leg members with each leg member being joined at a first point to one of the supports and being joined to the other support at a second point that is spaced along the leg member from the first point, the six leg members being arranged in circumferentially sequential pairs with the leg members of certain of the pairs crossing each other; and

means for individually manipulating at least certain of the leg members to vary the position of the points of such leg members relative to each other, wherein one of said supports is suspended beneath the other support by the six leg members.

5. A mechanism for locating an operator relative to an object, comprising the combination of:

an operator support and an object support spaced from each other;

six leg members with each leg member being joined at one point to one of the supports and being operatively connected to the other support at another point that is spaced along the leg member from the one point,

the areas in the two supports circumscribed by the junctions of the leg members in each support being substantially the same; and

means for individually manipulating at least certain of the leg members to vary the position of the points of such leg members relative to each other to thereby alter the position of the operator with respect to the object.

6. A mechanism in accordance with claim 5 together with means for sensing the changes in positions of the points of the leg members;

and

control means responsive to the sensing means, said control means coordinating said manipulating means.

7. A mechanism for locating an operator relative to an object, comprising the combination of:

an operator support and an object support spaced from each other;

six leg members with each leg member being joined at one point to one of the supports and being operatively connected to the other support at another point that is spaced along the leg member from the one point,

the areas in the two supports circumscribed by the junctions of the leg members in each support being substantially the same;

means for individually manipulating at least certain of the leg members to vary the position of the points of such leg members relative to each other to thereby alter the position of the operator with respect to the object, the mechanism further including means for sensing the changes in positions of the points of the leg members; and

control means responsive to the sensing means, said control means coordinating said manipulating means, wherein the six leg members are arranged in pairs with the leg members of each pair crossing each other.

8. A machine tool for locating a tool relative to a workpiece, comprising the combination of:

an upright rising from a base;

a pair of spaced platforms, the tool being fixed with respect to one of the platforms and the workpiece being fixed with respect to the other of the platforms, a first of the platforms being supported on said upright;

six powered extensible legs connecting the platforms and suspending the second platform from the first platform; and

vibration dampening means in the support of the first platform to said upright.

9. In a machine tool, the combination comprising:

a first platform adapted to mount a tool;

a second platform adapted to mount a workpiece;

six linearly extensible legs each pivotably mounted adjacent one end to the first platform and each pivotably mounted adjacent the other end to the second platform, the pivot mountings in each platform circumscribing an area, and the areas in each of the two platforms being substantially the same; and

means for individually varying the length of each leg to alter the position of the first platform and the tool with respect to the second platform and the workpiece.

10. A machine tool in accordance with claim 9, wherein the pivot mountings for the legs attached to the first platform are disposed adjacent three points defining a triangle and the pivot mountings for the legs attached to the second platform are disposed adjacent three points defining a second triangle, and the two triangles and the six legs generally define edges of an octahedron.

11. A machine tool in accordance with claim 9, wherein the pivot mountings of the legs to the platforms define the corners of a six-sided polygon in each platform.

12. A machine tool in accordance with claim 9 wherein said tool is a cutting tool mounted in a spindle attached to the first platform, and the second platform defines a fixed base for the machine tool and mounts a workpiece support that mounts the workpiece.

13. A machine tool in accordance with claim 9 wherein the first platform defines a fixed base for the machine, and the second platform is moved relative to the first platform.

14. In a machine tool having a tool holder and a workpiece support, the combination of:

an upright rising from a base that is fixed with respect to the workpiece support;

a platform mounting the tool holder;

six linearly extensible legs, three of said legs connecting the platform to the upright and three of said legs connecting the platform to the base; and

means for individually varying the length of each leg to alter the position of the tool holder with respect to the workpiece support.

15. A mechanism for locating an operator relative to an object, comprising:

a pair of supports, the operator being located with respect to one of the supports and the object being located with respect to the other support;

six powered and controllable extensible legs connecting the supports together in spaced relation;

an actuator for each leg for individually extending and contracting the length of the leg; and

a control for the leg actuators to coordinate the operation of the actuators to vary the position of the operator relative to the object, the control including sensing means for determining the length of each of the six legs, the sensing means including a plurality of extensible instrument arms connected between the supports independent of the legs and in a fixed relation to the legs so that a change in length of the legs alters the relationship between the supports which translates into changes in length of the instrument arms.

16. A mechanism in accordance with claim 15 wherein the instrument arms each include a sensor providing a signal proportional to changes in length of said instrument arm.

20. A mechanism in accordance with claim 15 wherein there are six instrument arms with one arm associated with each powered leg.

21. A mechanism in accordance with claim 20 wherein the six powered legs are arranged in pairs with the legs of each pair crossing each other, and the six instrument arms are arranged in pairs with the arms of each pair crossing each other.

17. A mechanism for locating an operator relative to an object, comprising:

a pair of supports, the operator being located with respect to one of the supports and the object being located with respect to the other support;

six powered and controllable extensible legs connecting the supports together in spaced relation;

an actuator for each leg for individually extending and contracting the length of the leg;

a control for the leg actuators to coordinate the operation of the actuators to vary the position of the operator relative to the object, the control including sensing means for determining the length of each of the six legs, the sensing means including a plurality of extensible instrument arms connected between the supports in a fixed relation to the legs so that a change in length of the legs alters the relationship between the supports which translates into changes in length of the instrument arms;

wherein the instrument arms each include a sensor providing a signal proportional to changes in length of said instrument arm, wherein each instrument arm includes two telescoping parts each joined respectively with one of said supports.

18. A mechanism in accordance with claim 17 wherein the sensor comprises a scale rod connected to one of the telescoping parts and a read head connected to the other telescoping part to provide a digital signal of the movement of the read head along the scale rod.

19. A mechanism in accordance with claim 17 wherein the sensor comprises a laser interferometer associated with one of the telescoping parts and a retro-reflector associated with the other part.

22. A machine tool for locating a tool relative to a workpiece, comprising:

a base;

a pair of spaced platforms, the tool being located with respect to one of the platforms and the workpiece being located with respect to the other of the platforms, a first of the platforms being supported by the base;

six powered extensible legs connecting the second platform to the first platform;

a manipulating mechanism to control the extension of at least some of the extensible legs; and

a vibration isolation device cooperating with the base and the first of the platforms to alleviate detrimental vibration.

23. The machine tool of claim 22, wherein the vibration isolation device includes a resilient member disposed intermediate the base and the first of the platforms.

24. In a machine tool having a tool holder and a workpiece support, the combination comprising:

a tool holder platform locating the tool holder;

a workpiece support platform locating the workpiece support;

six powered and controlled extensible legs connecting the platforms together in spaced relation, each of the legs being joined to the workpiece support platform at one point along the length of the leg and being joined to the tool holder platform at a second spaced point along the length of the leg;

an actuator for each leg for individually extending and contracting the length of the leg; and

a control for the leg actuators to coordinate the operation of the actuators to vary the position of the tool holder relative to the workpiece support, said control including sensing means for determining the length of each of the six legs,

the sensing means including a plurality of extensible instrument arms connected between said platforms in a known relation to the legs so that a change in length of the legs alters the relationship between the platforms which translates into changes in length of the instrument arms,

wherein each powered leg includes two telescoping parts, one of which is joined to the tool holder platform and the other of which is joined to the workpiece support platform.

25. A machine tool in accordance with claim 24 together with means preventing the two telescoping parts from rotating with respect to each other, one of the connections of each leg to a platform having three degrees of freedom of motion and the other connection of the leg to the other platform having two degrees of freedom of motion.

26. A mechanism for joining spaced platforms, comprising:

six legs connecting the platforms together, each of the legs being joined at one point to one of the platforms and being operatively connected to the other platform at another point that is spaced from the one point;

the six legs being arranged in circumferentially sequential pairs with the legs of each pair crossing each other; and

a manipulator mechanism configured to manipulate at least certain of the legs to vary the positions of the points of such legs relative to each other to thereby alter the position of the platforms with respect to each other.

27. A mechanism for locating an operator relative to an object, comprising:

a pair of spaced supports, the operator being located with respect to one of the supports and the object being located with respect to the other support; and

six extensible legs joining the supports, each leg comprising a ball screw rod and a nut tube surrounding the rod and joined thereto by recirculating balls, a first yoke assembly mounted with the ball screw rod to connect the leg to a first of said supports, and a second yoke assembly mounted to the nut tube to connect the leg to the second of said supports, and a motor connected to rotate said ball screw rod.

28. A mechanism in accordance with claim 27 wherein each yoke assembly includes a pair of forks rotatably attached to side faces of a support cube, one of the forks being connected to a respective support and the other fork being connected to the leg, said cube having a central opening to receive the screw rod.

29. A mechanism in accordance with claim 27, together with a protective tube surrounding said ball screw rod and proximity switches on said protective tube and nut tube to provide a signal when the ball screw rod has reached the limits of acceptable motion with respect to the nut tube.

30. A method of locating an operator relative to an object, comprising the steps of:

fixing the operator relative to a first support;

mounting the object relative to a second support;

connecting the supports together by six leg members each being joined at one point along its length to one of the supports and being operatively connected to the other support at a point that is spaced along the leg member from the one point;

locating the junctions of the leg members with the supports such that the areas circumscribed by the junctions in each of the two supports is substantially the same; and

manipulating the leg members to vary the position of the points of such leg members relative to each other to thereby provide three linear degrees of motion and three rotational degrees of motion, or any combination thereof, to the operator relative to the object.

31. A mechanism for locating an operator relative to an object, comprising the combination of:

a pair of supports spaced from each other, the operator being located with respect to one of the supports and the object being located with respect to the other of the supports;

six leg members with each leg member being joined at one point to one of the supports and being operatively connected to the other support at another point that is spaced along the leg member from the one point,

the six leg members being arranged in adjacent pairs with the leg members of certain of the pairs crossing each other; and

a manipulator mechanism configured to manipulate at least certain of the leg members to vary the position of the points of such leg members relative to each other to thereby alter the position of the operator with respect to the object.