Positioning workpieces by clamping devices

Patent metadata

Field	Value
Publication number	US-10016865-B2
Application number	US-201414325435-A
Country	US
Kind code	B2
Filing date	Jul 8, 2014
Priority date	Jul 17, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

Methods, devices, and systems for positioning workpieces for processing. In one aspect, a clamping device includes two clamping elements and a servo drive provided for the clamping elements. The servo drive is operable to first move at least one of the clamping elements toward the other of the clamping elements such that the clamping elements are transferred into a clamping start position in which the clamping elements are positioned on opposite sides of a workpiece arranged therebetween and in which the clamping elements do not apply a force to the workpiece or apply a force to the workpiece that is smaller than a clamping force, and subsequently urge the clamping elements toward one another from the clamping start position to an operational state, in which the clamping elements apply the clamping force to the workpiece.

First claim

What is claimed is:

1. A workpiece clamping device, comprising:
a carrying structure;
two clamping elements forming a clamping element pair and being located opposite one another on the carrying structure, wherein each of the clamping elements is provided with a guide slide and wherein each of the guide slides is guided on a guide arm of the carrying structure along a clamping axis and has a control pin protruding from a rear side of the guide slide; and
a servo drive that forms a positioning drive having:
a drive motor mounted on the carrying structure;
an adjusting ring that is rotatably mounted on the carrying structure and has two connecting members located diametrically opposite one another on the adjusting ring, each of the connecting members having a connecting member slot extending along the clamping axis and each of the connecting member slots guiding the control pin provided on the guide slide of one of the clamping elements along the clamping axis; and
a numerical control device configured to control the drive motor of the servo drive to rotate the adjusting ring including the connecting member slots and to thereby displace the control pins that are guided in the connecting member slots, the guide slides from which the control pins protrude, and the clamping elements provided with the guide slides, synchronously and in opposite directions along the clamping axis, such that the clamping elements thus are positioned relative to one another along the clamping axis,
wherein the drive motor of the servo drive is controlled by the numerical control device to:
first move the clamping elements toward one another into a pre-determined clamping start position in which the clamping elements are positioned on opposite sides of a workpiece arranged therebetween and in which the clamping elements do not apply a force to the workpiece or apply a force to the workpiece that is smaller than a clamping force that is pre-determined based on a stiffness of the workpiece,
subsequently urge the clamping elements toward one another from the pre-determined clamping start position to an operational state, in which the clamping elements apply the pre-determined clamping force to the workpiece, and
when the force applied by the clamping elements on the workpiece reaches the pre-determined clamping force, stop moving the clamping elements.

2. The workpiece clamping device of claim 1 , wherein the clamping elements are positioned such that, in the operational state, the clamping elements are located opposite one another on the opposite sides of the workpiece and each apply a respective clamping force to the respective side of the workpiece along a line of application of the respective clamping force, and such that, when the clamping elements are in the clamping start position, any force applied by the clamping elements along the line of application of the respective clamping force is less than the respective clamping force in the operational state.

3. The workpiece clamping device of claim 1 , wherein the clamping elements are arranged to define a clearance between the clamping elements and the workpiece in the clamping start position, and
wherein the servo drive is operable to move the clamping elements toward one another from the clamping start position into an operational position associated with the operational state.

4. The workpiece clamping device of claim 3 , wherein the servo drive is configured to move the clamping elements into the clamping start position at a higher speed than from the clamping start position into the operational position.

5. The workpiece clamping device of claim 1 , wherein the servo drive includes a device controller responsive to at least one of the force applied by the clamping elements to the workpiece or the position of the clamping elements during a relative movement of the clamping elements into an operational position associated with the operational state and configured to move the clamping elements as a function of the at least one of the force or the position.

6. The workpiece clamping device of claim 1 , wherein the carrying structure is rotatable about an axis of rotation.

7. The workpiece clamping device of claim 6 , wherein the servo drive includes a servomotor supported on the rotatable carrying structure.

8. The workpiece clamping device of claim 1 , wherein the servo drive includes a pneumatic servo drive with a pneumatic servomotor as the drive motor, and wherein the pneumatic servomotor includes a pneumatic piston-cylinder unit.

9. The workpiece clamping device of claim 8 , wherein the servo drive includes a pressure regulating unit and a valve unit that are configured to control a pressure in a chamber of a cylinder of the pneumatic piston-cylinder unit, and
wherein the numerical control device is configured to control the pressure regulating unit and the valve unit.

10. The workpiece clamping device of claim 1 , wherein data indicative of the clamping start position of the clamping elements is stored in the numerical control device.

11. The workpiece clamping device of claim 1 , wherein the numerical control device includes a first part that is close to the servo drive and a second part that is remote from the servo drive, and
wherein the second part of the numerical control device defines at least one operating mode in accordance with which the first part of the numerical control device controls the servo drive for at least one of moving the clamping elements into the clamping start position and transferring the clamping elements into the operational state.

12. The workpiece clamping device of claim 11 , wherein the at least one operating mode includes at least one of a force-controlled mode and a displacement- and thus position-controlled actuation of the clamping elements of the clamping device.

13. The workpiece clamping device of claim 11 , wherein the clamping elements are configured to clamp a workpiece in the form of a tube, and wherein the at least one operating mode is defined based on a wall stiffness of the tube resulting from a wall thickness of the tube.

14. The workpiece clamping device of claim 13 , wherein the workpiece clamping device is configured for clamping a thick-walled tube, by the second part of the numerical control device being configured to define a force-controlled mode for the first part of the numerical control device, in which the servo drive is force-controlled.

15. The workpiece clamping device of claim 13 , wherein the workpiece clamping device is configured for clamping a thin-walled tube, by the second part of the numerical control device being configured to define a displacement- and thus position-controlled mode for the first part of the numerical control device, in which the servo drive is displacement- and thus position-controlled.

16. A workpiece processing system, comprising:
a workpiece processing device; and
a workpiece clamping device comprising:
a carrying structure;
two clamping elements forming a clamping element pair and being located opposite one another on the carrying structure, wherein each of the clamping elements is provided with a guide slide and wherein each of the guide slides is guided on a guide arm of the carrying structure along a clamping axis and has a control pin protruding from a rear side of the guide slide; and
a servo drive that forms a positioning drive having:
a drive motor mounted on the carrying structure;
an adjusting ring that is rotatably mounted on the carrying structure and has two connecting members located diametrically opposite one another on the adjusting ring, each of

Assignees

• Trumpf Werkzeugmaschinen Gmbh Co Kg

Inventors

• Linder Bernd
• Popp Torsten
• Gaiser Bernd

Classifications

• B23B2231/14

  Chucks with clamping force limitation means · CPC title

• B25B5/147

  for pipes · CPC title

• B23Q3/064

  for holding elongated workpieces, e.g. pipes, bars or profiles · CPC title

• Y10T29/49998

  Work holding · CPC title

• B23B31/16141

  using fluid-pressure means to actuate the gripping means · CPC title