Thermal polymer clamping tool

• US 6,522,953 B1
• Filed: 08/26/1999
• Issued: 02/18/2003
• Est. Priority Date: 09/08/1998
• Status: Expired due to Fees

• Current Assignee: TCAM Power Workholding LLC
• Original Assignee: TCAM Power Workholding LLC
• Inventors: Schneider, Edward T.
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): RODRIGUEZ, PAUL L
• Application Number:
  US09/383,834
• Time in Patent Office: 1,272 Days
• Field of Search: 605/27, 605/28, 269/25, 269/157, 700/60, 700/114, 700/159, 700/169, 700/275, 700/281, 700/299, 700/160, 700/260, 700/261
• US Class Current: 700/275
• CPC Class Codes: B25B 1/06 Arrangements for positively actuating jaws
• CPC Class Codes: B25B 1/18 motor driven, e.g. with fluid drive, with or without provision for manual actuation
• CPC Class Codes: F15B 21/06 Use of special fluids, e.g. liquid metal; Special adaptations of fluid-pressure systems, or control of elements therefor, to the use of such fluids

Abstract

A workpiece is held between a movable clamping element (56) and a stationary clamping element (52). During setup, a hex drive (58) is rotated to move a traveler (100) which is connected to the movable clamping element along a threaded shaft (80). The threaded shaft is supported at one end through a spring retainer nut (88), a spring (86), and a bearing (82). After the movable clamping element engages the workpiece, the spring is compressed, limiting the amount of clamping force applied to the workpiece. The retainer nut (88) is selectively moved through the use of the tool to a selectable position along the threaded shaft (80) to adjust the spring compression, hence the clamping force. After initial setup, an electrochemical actuator (110) is actuated to melt a polymer, forcing a piston assembly (118, 120) and a bearing (84) to shift the threaded shaft (80) longitudinally against the spring, moving the clamping elements apart a short distance to release or receive a workpiece. The electrochemical actuator is then deactivated, allowing the spring to expand, clamping the workpiece between the clamping elements with the selected force. This enables an operator to load a workpiece manually into a vise (12) at a loading station (14). An automatic controller (30) controls a plurality of the vises, a moving table (10), a plurality of machine tools (18), and optionally, a robotic workpiece repositioning station (20).

Claims

1. A clamping device comprising:

first and second clamping elements, at least one of which is movable between an open position for receiving a workpiece and a clamped position for holding the workpiece;

a polymeric actuator for controlling movement of the at least one clamping element between the open and clamped positions, the polymeric actuator including;

a housing which defines a polymer containing chamber;

a polymer disposed in the chamber which expands and contracts under heating and cooling;

a driving element movably mounted in fluid communication with the chamber for extending and retracting as the polymer expands and contracts, the driving element being connected with at least one of the clamping elements for driving the elements toward one of the open and clamped positions as the polymer expands.

2. The clamping device as set forth in claim 1 wherein:

a first of the clamping elements is mounted on a follower which is threadedly received on a threaded shaft; and

,

the polymeric actuator is connected with the shaft for moving the shaft longitudinally.

3. The clamping device as set forth in claim 2 further including:

a spring element connected with the shaft for biasing the shaft against the polymeric actuator.

4. The clamping device as set forth in claim 3 further including:

a compression adjustment for adjusting the spring element to adjust an amount of force which the spring exerts on the threaded shaft.

5. The clamping device as set forth in claim 4 wherein the polymeric actuator is connected with the shaft to push the at least one clamping element toward the open position and the spring is connected with the threaded shaft to push the at least one clamping element towards the clamped position, adjustment of the spring compression adjusting an amount of pressure with which the clamping elements grip the workpiece.

6. The clamping device as set forth in claim 1 wherein the polymeric actuator is connected with at least one of the clamping elements for driving the clamping elements toward the clamping position.

7. The clamping device as set forth in claim 1 wherein the polymeric actuator further includes:

a generally circular bore defined in the housing;

a drive element receiving port within which the drive element is slidably mounted;

a substantially circular bobbin carrying an electrical heater, the bobbin being disposed eccentrically within the bore to define an annular polymer receiving chamber which is thicker toward the drive element receiving port and thinner opposite the driving element receiving port.

8. The clamping device as set forth in claim 7 wherein the bobbin includes annular grooves to provide larger capacity flow channels for the polymer.

9. The clamping device as set forth in claim 1 further including:

an electrical heater element for electrically heating the polymer to change the polymer from a solid phase to a liquid phase.

10. The clamping device as set forth in claim 9 wherein the electric heating element is constructed of a positive temperature coefficient wire such that changes in its resistance are indicative of polymer temperature, and further including:

displacement sensors for sensing displacement of the drive element; and

,

an indicator light system for indicating when a selected clamping force has been achieved based on the sensed displacement and the polymer temperature.

11. The clamping device as set forth in claim 9 further including:

a foot pedal switch connected between the electrical heater element and a source of electrical power for controlling actuation of the polymeric actuator.

12. The clamping device as set forth in claim 9 further including:

a computerized controller connected with the electrical heater element and at least one metal removal tool for coordinately controlling clamping of the workpiece and at least one metal removal operation on the clamped workpiece.

13. The clamping device as set forth in claim 1 wherein the clamping elements include:

at least one stationary element for engaging first and second workpieces;

first and second movable clamping elements for engaging the first and second workpieces;

a common carrier member for carrying the first and second movable clamping elements;

a force equalizing means supported by the carrier and connected between the first and second movable clamping elements for equalizing the force applied to the first and second workpieces.

14. The clamping device as set forth in claim 13 wherein the force equalizing means includes:

a rocker element pivotally mounted to the carrier, the rocker element having a pair of arms disposed to opposite sides of a pivot, each of the arms being connected with one of the first and second movable clamping elements.

15. The clamping device as set forth in claim 1 wherein the polymeric actuator further includes:

a bore defined in the housing, the driving element being received through a port connected with the bore;

a bobbin disposed eccentrically within the bore to define an annular polymer receiving chamber which is thicker toward the driving element receiving port and thinner opposite the drive element receiving port;

a heater in thermal communication with the polymer for selectively expanding the polymer.

16. A clamping device comprising:

first and second clamping elements, at least one of which is movable between an open position for receiving a workpiece and a clamped position for holding the workpiece;

an electrically controlled actuator for controlling movement of the at least one clamping element between the open and clamping positions, wherein the electrically controlled actuator includes;

a housing which defines a polymer containing chamber;

a polymer disposed in the chamber which expands and contracts under heating and cooling;

an electrical element thermally connected with the polymer for controlling expansion and contraction of the polymer; and

a driving element movably mounted in fluid communication with the chamber for extending and retracting as the polymer expands and contracts, the driving element being connected with at least one of the clamping elements for driving the element toward one of the open and clamped positions as the polymer expands.

17. The clamping device as set forth in claim 16 wherein:

a first of the clamping elements is mounted on a follower which is threadedly received on a threaded shaft;

the electrically controlled actuator is connected with the shaft for moving the shaft longitudinally; and

a spring element is connected with the shaft for biasing the shaft against the electrically controlled actuator.

18. A clamping method comprising:

mechanically biasing first and second clamping elements toward each other with a clamping force;

thermally expanding a polymer to move the clamping elements apart against the mechanically biased clamping force;

placing a workpiece between the clamping elements;

cooling and contracting the polymer such that the clamping elements are mechanically biased together to clamp the workpiece with the clamping force.