JP2013244585A - Clamping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clamping device that can be prevented from being operated defectively due to a sputter by magnetically adsorbing the sputter by a sputter magnetically adsorbing means which is not deformed in clamping.SOLUTION: A clamping device 10 includes an accommodation hole 21b formed in a locating pin 21, an opening 21c which is formed in the locating pin 21 and opens the accommodation hole 21b to the outside, and a clamp arm 23 which protrudes to the outside of the locating pin 21 from the opening 21c at a clamp position and clamps a workpiece W seated at a seating part 22b. Furthermore, the clamping device 10 has an air cylinder which is coupled to the clamp arm 23 through an output rod and moves up and down the clamp arm 23. Then the clamping device 10 has a magnet 30 provided above the output rod and as a different body from the clamp arm 23.

Description

  The present invention relates to a clamp device that includes a clamp arm that projects out of a locating pin from an opening at a clamp position and clamps a workpiece seated on a seat, and a drive source that moves the clamp arm up and down.

  For example, when welding a workpiece such as a panel material in an automobile production line, the workpiece is positioned by a clamp device. In the clamp device, if spatter generated during welding enters the clamp device, an operation failure occurs in the clamp device. Therefore, in order to prevent the operation failure, invasion of spatter is prevented. An example of such a clamping device is Patent Literature 1. As shown in FIG. 7, the clamp device 80 includes an air cylinder 81, a support cylinder 82 supported by the air cylinder 81, and a locate pin 83 supported by the support cylinder 82. A long hole space 84 is formed in the locate pin 83, and an escape hole 85 communicating with the long hole space 84 is formed. A clamp lever 86 is accommodated in the long hole space 84 and the internal space 82a in the support cylinder 82 so as to be movable up and down. The clamp lever 86 is operatively connected to the air cylinder 81.

  The guard member 87 for preventing the intrusion of spatter is made of a leaf spring, the clamp side tip 87a is fixed to the clamp 86a at the tip of the clamp lever 86, and the lower end 87b is fixed inside the escape hole 85. . The guard member 87 can be deformed in accordance with the movement of the clamp lever 86. When the workpiece 90 is clamped by the clamp lever 86, the seating surface 83a of the locate pin 83 and the clamp portion 86a are in close contact with the workpiece 90, respectively. Further, the guard member 87 is deformed, and the guard member 87 and the clamp lever 86 block the communication between the outside and the space on the support tube 82 side, thereby preventing spatter from entering the clamp device 80.

JP 2009-248255 A

  In the clamping device 80 of Patent Document 1, the guard member 87 is deformed at the time of clamping and prevents spatter from entering the clamping device 80. For this reason, if the deformation of the guard member 87 is repeated due to the long-term use of the clamping device 80, the guard member 87 is deteriorated or damaged, and the spattering prevention function by the guard member 87 is lowered. There is a risk of malfunction of the device 80 occurring.

  It is an object of the present invention to provide a clamping device capable of preventing malfunction due to sputtering by magnetizing sputtering by sputtering magnetizing means that does not deform during clamping.

  In order to solve the above-mentioned problems, the invention described in claim 1 includes a locating pin that is inserted into a clamp hole formed in a work and positions the work, a support cylinder that supports the locating pin at an upper portion, and the locating pin. A seating portion on which the workpiece positioned by the seating can be seated, a receiving hole formed in the locate pin, an opening formed in the locate pin and opening the receiving hole to the outside, the receiving hole, and the support In the internal space of the cylinder, it is provided so as to be movable up and down, and is provided so as to be able to advance and retreat from the opening.At the forward-side clamp position, the work projecting from the opening to the outside of the locating pin A clamp arm to be clamped and connected to the clamp arm via a power transmission mechanism, A drive source for downward, on the upper side than the power transmission mechanism, and the said clamp arm and summarized in that with a sputtering magnetic attraction means comprising a magnetic material which is disposed separately.

  According to this, even when spatter enters the clamping device through the opening during welding of the workpiece, the spatter is magnetized on the sputter magnetizing means above the power transmission mechanism. Therefore, it is possible to prevent the spatter from reaching the power transmission mechanism, and it is possible to prevent the drive source from malfunctioning due to the spatter. Since the sputter magnetizing means is separate from the clamp arm, even if the clamp arm moves to clamp the workpiece, the sputter magnetized means will not be deformed and the clamp arm will not contact. . Therefore, even if the clamping device is used for a long period of time, the sputter magnetizing means is not damaged or deformed, and the sputter magnetizing function by the sputter magnetizing means can continue to be exhibited.

  According to a second aspect of the present invention, in the clamping device according to the first aspect, the sputter magnetizing means is a magnet provided on an inner surface of the support cylinder, and the support cylinder is in sliding contact with the magnet. The gist of the invention is that a discharge plate is provided for removing spatter magnetized on the magnet from the magnet.

According to this, it is possible to remove spatter from the magnet by the discharge plate and prevent spatter from accumulating on the magnet.
The gist of the invention described in claim 3 is that, in the clamp device according to claim 2, the discharge plate is interlocked with the clamp arm.

According to this, at the time of operation of the clamp device, the spatter can be continuously removed from the magnet by the discharge plate, and the spatter can be prevented from being deposited on the magnet.
A fourth aspect of the present invention is summarized in that, in the clamping device according to the first aspect, the sputter magnetizing means is an electromagnet.

  According to this, when the clamp device is operated, the electromagnet is magnetized and the spatter is magnetized, and after the operation of the clamp device is finished, the electromagnet is made non-magnetic and the sputter can be dropped from the electromagnet. Therefore, spatter can be efficiently removed from the electromagnet.

  According to the present invention, sputtering can be magnetized by the sputtering magnetizing means that does not deform during clamping, thereby preventing malfunction due to sputtering.

Sectional drawing which shows the clamp apparatus of 1st Embodiment. The fragmentary sectional view which shows the state which clamped the workpiece | work with the clamp lever. The fragmentary sectional view which shows the clamp apparatus of 2nd Embodiment. In 3rd Embodiment, (a) is a fragmentary sectional view which shows the state which advanced the discharge | emission plate, (b) is a fragmentary sectional view which shows the state which sputtered with the discharge | emission plate. The fragmentary sectional view which shows the clamp apparatus of 4th Embodiment. The fragmentary sectional view which shows another example of a clamp apparatus. The figure which shows background art.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the clamp device 10 is provided with an air cylinder 11 as a drive source at a lower portion thereof. The lower end (base end) of the support cylinder 12 is fixed to the upper end (front end) of the air cylinder 11. In the air cylinder 11, a piston 15 is accommodated in a bottomed cylindrical cylinder body 14 constituting an outer shell so as to be slidable along the axial direction of the cylinder body 14 (the vertical direction indicated by arrow Y in FIG. 1). ing. An annular rod cover 14 a is attached to the cylinder body 14 on the side of the support cylinder 12.

  The piston 15 divides the internal space of the cylinder body 14 into a first pressure action chamber 16 on the rod cover 14 a side and a second pressure action chamber 17 on the bottom side of the cylinder body 14. Air is supplied to and discharged from the first pressure working chamber 16 through a first fluid supply / discharge port (not shown) formed in the cylinder body 14. On the other hand, air is supplied to and discharged from the second pressure working chamber 17 through a second fluid supply / discharge port 18 formed in the cylinder body 14. An output rod 19 extending from the piston 15 toward the first pressure action chamber 16 is connected to the central portion of the piston 15. A seal member 14 c that prevents air leakage from between the inner peripheral surface of the rod cover 14 a and the output rod 19 is attached to the inner peripheral surface of the rod cover 14 a. In the support cylinder 12, a pair of air blow holes 12g through which air can be blown are formed above the rod cover 14a so as to face each other.

  A cylindrical locating pin 21 is supported on the upper end of the support cylinder 12, and a rusted cylindrical cover member 22 is externally mounted on the locating pin 21. The locate pin 21 is provided so as to penetrate the inside of the cover member 22 and extend in the axial direction (vertical direction). The locate pin 21 is integrally provided with a flange portion 21a having a rectangular shape in plan view at the outer peripheral portion of the lower end (base end) thereof, and the flange portion 21a is supported by the upper end of the support cylinder 12. Further, in the locate pin 21, an accommodation hole 21 b extending in the axial direction (vertical direction) of the locate pin 21 is formed.

  The accommodation hole 21 b communicates with the internal space 12 a of the support cylinder 12. An opening 21 c is formed in the peripheral wall of the locate pin 21, and the opening 21 c opens toward the outside of the locate pin 21 above the upper end surface of the cover member 22. Note that, on the peripheral wall of the locate pin 21, the opposite side of the opening 21 c is not open, and is closed by the peripheral wall of the locate pin 21.

  A flange portion 22 a having a substantially circular shape in plan view is provided on the outer periphery of the lower end (base end) of the cover member 22. The upper end surface (front end surface) of the cover member 22 is located on the lower end (base end) side of the locate pin 21 and is configured as a seating portion 22b on which a workpiece is seated. The seating portion 22b is formed in an annular shape in plan view.

  An output rod 19 of the air cylinder 11 protrudes from the internal space 12 a of the support cylinder 12. The lower end (base end) of the clamp arm 23 is rotatably connected to the upper end (front end) of the output rod 19. In the present embodiment, the output rod 19 constitutes a power transmission mechanism that transmits the power of the air cylinder 11 to the clamp arm 23. The upper side of the clamp arm 23 extends into the accommodation hole 21 b of the locate pin 21. A clamp piece 24 extending in a hook shape in a direction orthogonal to the central axis of the locate pin 21 is formed at the upper end portion (tip portion) of the clamp arm 23. The clamp arm 23 is accommodated in the accommodation hole 21b of the locate pin 21 so as to be able to appear and retract.

  The clamp arm 23 is formed with a guide hole 25 extending in the axial direction of the clamp arm 23 at a substantially central portion in the axial direction. Guide pins 26 having both ends fixed to the support cylinder 12 are inserted into the guide holes 25. The guide hole 25 is formed so as to extend obliquely in the direction opposite to the protruding direction of the clamp piece 24 from the lower end side to the upper end side of the clamp arm 23 as a whole.

  On the inner peripheral surface of the support cylinder 12, a magnet 30 (magnetic material) as a sputter magnetizing means is mounted below the opening 21 c of the locate pin 21 and above the output rod 19. The magnet 30 has an annular shape, and the clamp arm 23 is inserted inside the magnet 30 so as to be movable up and down without contacting the magnet 30. That is, when the clamp arm 23 moves up and down, the clamp arm 23 is not in contact with the magnet 30.

Next, the operation of the clamping device 10 will be described.
As shown in FIG. 1, in a state where the clamp device 10 is waiting for the workpiece W to be inserted, the clamp arm 23 is in the raised position and is waiting in an unclamped state. At this time, the first fluid supply / discharge port is opened to the atmosphere, and air is supplied to the second fluid supply / discharge port 18.

  As shown in FIG. 2, the locate pin 21 is inserted into a clamp hole Wa formed in the workpiece W. When the peripheral edge of the clamp hole Wa of the workpiece W is seated on the seat 22b, air is supplied to the first pressure working chamber 16 via the first fluid supply / discharge port, and the second fluid supply / discharge port. The air in the second pressure working chamber 17 is discharged from 18. Then, the piston 15 and the output rod 19 are lowered, and the clamp arm 23 is lowered as the output rod 19 is lowered. Then, when the guide hole 25 is in sliding contact with the guide pin 26, the clamp piece 24 advances from the opening 21 c while the clamp arm 23 is lowered, and protrudes outward from the locate pin 21.

  Then, the peripheral edge of the clamp hole Wa of the workpiece W is clamped between the clamp piece 24 of the clamp arm 23 and the seating portion 22b. Then, air is supplied from the first fluid supply / discharge port, and the state where the workpiece W is clamped by the clamping device 10 is maintained. Thereafter, the workpiece W is welded in a state where the workpiece W is clamped. Spatter S generated during welding of the workpiece W enters the accommodation hole 21b from the opening 21c opened to the retracting side of the clamp arm 23 in the opening 21c. Even if the spatter S enters the accommodation hole 21 b, the sputter S is magnetically attached to the magnet 30 positioned on the retreat side of the clamp arm 23 by the magnetic force of the magnet 30, and air that is lower (back side) than the magnet 30. Spatter S is prevented from reaching the cylinder 11 side.

According to the above embodiment, the following effects can be obtained.
(1) In the clamping device 10, the magnet 30 is mounted on the inner peripheral surface of the support cylinder 12 above the output rod 19 of the air cylinder 11, and the sputter S can be magnetized by the magnet 30. For this reason, even when the spatter S enters the support cylinder 12 through the opening 21c during welding of the workpiece W, the sputter S is magnetically attached to the magnet 30 before the air cylinder 11, and the sputter S is applied to the air cylinder 11. Can be prevented from reaching. For this reason, it is possible to prevent the sputter S from entering the air cylinder 11 and entering between the output rod 19 and the seal member 14c. As a result, it is possible to reliably prevent air leakage by the seal member 14c and prevent the air cylinder 11 from malfunctioning. And the magnet 30 is arrange | positioned in the position away from the clamp arm 23, and even if the clamp arm 23 moves in order to clamp the workpiece | work W, the magnet 30 does not deform | transform and the clamp arm 23 does not contact. . Therefore, even if the clamp device 10 is used repeatedly, the magnet 30 is not damaged or deformed, and the magnet adhesion function of the sputter S by the magnet 30 can be continuously exhibited.

  (2) Since the magnet 30 is formed in an annular shape and arranged so as to extend over the entire circumferential direction of the inner circumferential surface of the support cylinder 12, the sputter S is sputtered by the magnet 30 at any position in the circumferential direction in the internal space 12a. Can be magnetized.

(3) Since the magnet 30 only needs to contact the clamp arm 23, it is not necessary to set the dimension thereof with high accuracy, and the manufacturing cost of the clamp device 10 can be reduced.
(4) Since the clamp arm 23 moves up and down without coming into contact with the magnet 30, the clamp arm 23 can be prevented from being deformed while exhibiting the function of magnetizing the sputter S by the magnet 30.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted or simplified.

  As shown in FIG. 3, the support cylinder 12 has a pair of communication holes 12d formed at positions facing each other across the internal space 12a. A magnet (magnetic body) 40 serving as a sputter magnetizing means is inserted into each of the communication holes 12d. The magnet 40 can be inserted into and removed from the communication hole 12d. The magnet 40 is formed of a magnetized part 40a on the inner space 12a side (tip side) and a base part 40b on the base end side. The magnetized part 40a has a diameter smaller than the diameter of the communication hole 12d and is formed thinner than the base part 40b. For this reason, when the magnetized part 40a is drawn into the communication hole 12d, a gap is formed between the magnetized part 40a and the communication hole 12d. The base 40b is formed to have a diameter slightly smaller than the diameter of the communication hole 12d, and the base 40b is supported so as to be slidable in the communication hole 12d.

  In the clamp device 10, the magnet 40 is used in a state where the magnetized portion 40a is exposed in the internal space 12a. Then, the spatter S generated during welding of the workpiece W enters the accommodation hole 21b from the opening 21c opened to the retreat side of the clamp arm 23 in the opening 21c. Even if the spatter S enters the accommodation hole 21 b, the sputter S is magnetically attached to the magnetized part 40 a by the magnetic force of the magnet 40, and the sputter S is prevented from reaching the air cylinder 11 side that is behind the magnet 40. . Further, when the clamp device 10 is stopped, the magnet 40 can be extracted from the communication hole 12 d and removed from the support tube 12, and the sputter S magnetically attached to the magnetized portion 40 a can be removed from the magnet 40.

Therefore, according to the second embodiment, in addition to the same effects as (1) and (4) of the first embodiment, the following effects can be obtained.
(5) The magnet 40 can be inserted into and removed from the support cylinder 12 and is detachable. For this reason, the magnet 40 can be removed from the outside of the support cylinder 12, and the sputter S can be removed from the magnet 40 at a position different from the clamping device 10.

  (6) The magnetized portion 40a of the magnet 40 is formed to have a diameter smaller than the diameter of the communication hole 12d. For this reason, when the magnet 40 is pulled into the communication hole 12d in order to remove it from the support cylinder 12, the magnetized portion 40a can be separated from the inner peripheral surface of the communication hole 12d. Therefore, it is possible to prevent the sputter S magnetically attached to the magnetized portion 40a from being scraped off by the inner surface of the communication hole 12d when passing through the communication hole 12d.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted or simplified.

  As shown in FIG. 4A, in the support cylinder 12, a pair of discharge holes 12 f are formed above the upper surface of the magnet 30 at positions facing each other with the internal space 12 a interposed therebetween. The clamp arm 23 is provided with an annular discharge plate 41. The discharge plate 41 has a long hole 41a. The clamp arm 23 can be moved forward and backward in the long hole 41a.

  As shown in FIG. 4A, when the clamp arm 23 moves forward and is positioned at the clamp position, the clamp arm 23 pushes the discharge plate 41 on the forward side to advance the discharge plate 41. On the other hand, as shown in FIG. 4 (b), when the clamp arm 23 is retracted and positioned at the unclamping position, the clamp arm 23 pushes the discharge plate 41 on the retract side to retract the discharge plate 41. ing. That is, the discharge plate 41 moves forward or backward in conjunction with the clamp arm 23. The discharge plate 41 is made of a nonmagnetic material (for example, synthetic resin). Further, the discharge plate 41 is supported on the magnet 30 and is slidable on the upper surface of the discharge plate 41.

  In the clamping device 10, the sputter S generated during welding of the workpiece W enters the accommodation hole 21 b from the opening 21 c opened to the retracted side of the clamp arm 23 in the opening 21 c. Even if the spatter S enters the accommodation hole 21b, the sputter S is magnetically attached to the upper surface of the magnet 30.

  As the clamp arm 23 advances, the discharge plate 41 advances. Then, on the magnet 30 positioned on the backward side of the clamp arm 23, the discharge plate 41 moves in a direction in which the contact area with the upper surface of the magnet 30 decreases. Then, when the clamp arm 23 moves backward because the clamping device 10 shifts to the unclamped state, the sputter S that is magnetically deposited on the magnet 30 positioned on the backward side of the clamp arm 23 is directed toward the discharge hole 12f by the discharge plate 41. Extruded.

Therefore, according to the third embodiment, in addition to the same effects as (1) and (4) of the first embodiment, the following effects can be obtained.
(7) A discharge plate 41 that interlocks with the forward and backward movement of the clamp arm 23 is provided. Then, when the clamp arm 23 moves backward when shifting to an unclamped state where welding is not performed, the sputter S magnetically attached to the magnet 30 can be pushed out from the magnet 30 by the discharge plate 41. And the sputter | spatter S extruded from on the magnet 30 is discharged | emitted by the discharge hole 12f. Therefore, by providing the discharge plate 41 interlocked with the clamp arm 23, the sputter S can be continuously removed from the magnet 30 when the clamp device 10 is operated, and the spatter S is prevented from being deposited on the magnet 30. Can do.

(Fourth embodiment)
Next, a fourth embodiment embodying the present invention will be described with reference to FIG. In addition, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted or simplified.

  As shown in FIG. 5, the sputter magnetizing means provided on the support cylinder 12 is an electromagnet 44. The electromagnet 44 is signal-connected to the controller 46 via a wiring 45. During the operation of the clamping device 10 (during clamping and unclamping), the controller 46 magnetizes the electromagnet 44 and magnetizes the sputter S. On the other hand, after the operation of the clamping device 10 is finished, the controller 46 makes the electromagnet 44 non-magnetic and causes the magnetized sputter S to fall off the electromagnet 44. Thereafter, air is blown into the support cylinder 12 from one air blow hole 12g, and the sputter S is discharged out of the support cylinder 12 from the other air blow hole 12g.

Therefore, according to the fourth embodiment, in addition to the same effects as (1) and (4) of the first embodiment, the following effects can be obtained.
(8) The electromagnet 44 is provided in the clamp device 10. During the operation of the clamping device 10, the electromagnet 44 was magnetized to magnetize the sputter S, and after the operation of the clamping device 10 was finished, the electromagnet 44 was made non-magnetic and the sputter S was dropped. Therefore, the sputter S can be efficiently removed from the electromagnet 44.

In addition, you may change the said embodiment as follows.
In the third embodiment, the discharge plate 41 is linked to the clamp arm 23. However, the discharge plate 41 may not be linked to the clamp arm 23. Then, when the sputter S is deposited on the magnet 30, the sputter S may be removed from the magnet 30 by manually moving the discharge plate 41.

  In the first embodiment, only one magnet 30 is provided in the axial direction of the support cylinder 12, but a plurality of magnets 30 may be provided in the axial direction of the support cylinder 12 as shown in FIG. In other embodiments, a plurality of magnets 40 and electromagnets 44 may be provided in the axial direction of the support cylinder 12. In this case, the magnetic force of the upper magnets 30 and 40 and the electromagnet 44 is preferably made larger than the magnetic force of the lower magnets 30 and 40 and the electromagnet 44.

  With this configuration, the sputter S is almost magnetized by the upper magnets 30 and 40 and the electromagnet 44, and the sputter S not magnetized by the upper magnets 30 and 40 and the electromagnet 44 is converted into the lower magnets 30 and 40. In addition, the electromagnet 44 can be magnetized. Therefore, the spatter S reaching the air cylinder 11 can be eliminated by providing the magnets 30 and 40 and the electromagnet 44 in a plurality of stages.

  In each embodiment, the magnets 30 and 40 and the electromagnet 44 are provided over the entire circumferential direction of the inner peripheral surface of the support cylinder 12, but the magnets 30, 40 and the electromagnet 44 are only a part in the circumferential direction of the support cylinder 12. May be provided. Further, the magnets 30 and 40 may be provided separately in the circumferential direction of the support cylinder 12.

In the embodiment, the magnets 30 and 40 and the electromagnet 44 are provided on the support cylinder 12, but the magnets 30 and 40 and the electromagnet 44 may be provided on the locate pin 21 or the cover member 22.
In the embodiment, the magnets 30 and 40 and the electromagnet 44 are provided in the support cylinder 12 as the sputtering magnetizing means. However, the support cylinder 12 may be the electromagnet and the support cylinder 12 may be the sputtering magnetizing means.

In the embodiment, the air cylinder 11 is embodied as a drive source, but may be embodied in another fluid pressure cylinder such as a hydraulic cylinder instead of the air cylinder 11.
In the embodiment, the power transmission mechanism is embodied in the output rod 19 of the air cylinder 11, but is not limited thereto. When the drive source is changed to the electric motor, the ball screw of the electric motor may be used as the power transmission mechanism.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) The clamping device according to any one of claims 1 to 4, wherein, in the locate pin, an opposite side of the opening with the accommodation hole interposed therebetween is closed.

  (B) The clamp device according to claim 2 or 3, wherein a plurality of the magnets are provided in an axial direction of the support cylinder.

  S ... Spatter, W ... Workpiece, Wa ... Clamp hole, 11 ... Air cylinder as drive source, 12 ... Support cylinder, 12a ... Internal space, 19 ... Output rod as power transmission mechanism, 21 ... Locate pin, 21b ... Housing hole , 21c: opening, 22b: seating portion, 23: clamp arm, 30, 40: magnet as sputtering magnetizing means, 41: discharge plate, 44: electromagnet as sputtering magnetizing means.

Claims (4)

A locate pin that is inserted into a clamp hole formed in the workpiece and positions the workpiece;
A support cylinder for supporting the locate pin on the top;
A seating portion on which the workpiece positioned by the locate pin can be seated;
A receiving hole formed in the locate pin;
An opening that is formed in the locate pin and opens the accommodation hole to the outside;
The seating hole and the inner space of the support cylinder are provided so as to be movable up and down, and are provided so as to be able to advance and retract from the opening. A clamp arm for clamping the workpiece seated on the part;
A drive source connected to the clamp arm via a power transmission mechanism and moving the clamp arm up and down;
And a sputter magnetizing means made of a magnetic material provided above the power transmission mechanism and separately from the clamp arm.   The sputter magnetizing means is a magnet provided on the inner surface of the support cylinder, and is provided on the support cylinder so as to be slidable with respect to the magnet so as to remove spatter magnetized on the magnet from the magnet. The clamping device according to claim 1, wherein a discharge plate is provided.   The clamp device according to claim 2, wherein the discharge plate is interlocked with the clamp arm.   The clamping apparatus according to claim 1, wherein the sputter magnetizing means is an electromagnet.