JP2017217744A - Collet chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain machining accuracy by surely clamping a workpiece at a proper position where the workpiece is seated on a stopper without deforming the workpiece.SOLUTION: A collet chuck 1 includes: a collet 4 which performs an expanding and contracting operation in a workpiece W abutting on a stopper 20 so that the workpiece W can be clamped/unclamped in a chuck body 2 provided with a stopper 20 for positioning the workpiece W on a front face; and a draw bar 3 which advances and retreats at a center of the collet 4, contracts the collet 4 according to the advancing so that the collet performs an unclamping operation and expands the collet 4 according to the retreating so that the collet performs a clamping operation. The collet 4 is slidably provided in a longitudinal direction by a prescribed stroke adjustable by a shoulder bolt 27 and is energized at an advancing position by a stroke by a coil spring 33 in the unclamping state.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a collet chuck that is attached to a main shaft such as a lathe and clamps an inner peripheral surface of a workpiece.

A collet chuck for clamping the inner peripheral surface of the workpiece is attached to a main spindle such as a lathe. As this collet chuck, as disclosed in Patent Document 1, a holder link is provided in the chuck cover through which a center mandrel penetrates and can be moved back and forth in the axial direction by an actuating device. A structure in which a plurality of chuck parent claws are connected so as to be expandable and contractable in the radial direction and urged in the contraction direction and a reference metal (stopper) is provided on the chuck cover is known. With this structure, when the holder link is retracted by the actuator while the workpiece is in contact with the reference surface of the reference gold and positioned in the axial direction, the chuck parent pawl that contacts the center mandrel expands while retracting. The inner peripheral surface is clamped while the workpiece is pulled backward.
Further, in Patent Document 2, an expander having a tapered surface on the outer periphery of the front end is provided at the axial center in the cylindrical portion so as to be movable back and forth in the axial direction via a tow rod, and a plurality of expanders are provided on the outer peripheral side of the expander. A collet chuck provided with a collet that can be expanded and contracted is disclosed. In this collet chuck, when the expander is retracted in a state where the work is brought into contact with the tip (stopper) of the cylindrical portion and positioned, the collet expands to clamp the inner peripheral surface of the work.

Japanese Patent No. 4133636 Japanese Patent No. 2740939

The retractable collet chuck that clamps while pulling the workpiece as in Patent Document 1 can obtain a high clamping force. However, when clamping a workpiece with a relatively thin wall thickness in the axial direction, the workpiece is distorted and machining accuracy is increased. May decrease. Therefore, it is necessary to set the stopper position so that the workpiece does not deform.
On the other hand, a stationary collet chuck that clamps a positioned workpiece as it is as in Patent Document 2 is unlikely to be deformed like a retractable type, but depending on the shape of the workpiece or the shape of the collet, it may be in close contact with the stopper. In some cases, proper clamping cannot be performed.

  Accordingly, an object of the present invention is to provide a collet chuck capable of maintaining machining accuracy by reliably clamping at an appropriate position for sitting on a stopper without deforming the workpiece.

In order to achieve the above-mentioned object, the invention according to claim 1 clamps / unclamps a workpiece by expanding / contracting the workpiece in a chuck body provided with a stopper for positioning the workpiece on the front surface within the workpiece in contact with the stopper. The collet chuck is equipped with a possible collet and a draw bar that moves forward and backward at the center of the collet, contracts the collet as it moves forward, unclamps, and expands the collet as it moves backward to clamp it. And
The collet is provided so as to be slidable in the front-rear direction with a predetermined adjustable stroke, and in an unclamped state, the collet is urged to a forward position in the stroke.
According to a second aspect of the present invention, in the configuration of the first aspect, the urging means is a coil spring that presses the collet from the rear by an elastic force.
According to a third aspect of the present invention, in the configuration of the first aspect, the urging means is a piston that presses the collet from the rear by fluid pressure.

According to the first aspect of the present invention, the collet is provided so as to be slidable in the front-rear direction with a predetermined adjustable stroke, and is biased to the forward movement position by the biasing means, so that the workpiece can be drawn and clamped. Unnecessary pull-in is regulated. Therefore, the workpiece can be reliably clamped at an appropriate position for sitting on the stopper without deforming the workpiece, and the machining accuracy can be maintained.
According to the second aspect of the present invention, in addition to the effect of the first aspect, the collet biasing means is a coil spring, so that the collet can be easily biased to the forward position.
According to the third aspect of the present invention, in addition to the effect of the first aspect, the urging means of the collet is a piston, so that the drawing force of the workpiece can be easily adjusted by the fluid pressure.

It is a front view of a collet chuck (work is in a clamped state). It is the sectional view on the AA line of FIG. It is an AA line sectional view showing the unclamped state of a work. It is explanatory drawing of a collet. It is sectional drawing in the same AA line as FIG. 1 of the collet chuck of the example of a change (a workpiece | work is a clamped state).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view showing an example of a collet chuck, FIG. 2 is a sectional view taken along the line AA, and the right side of FIG. The collet chuck 1 includes a draw bar 3 that can be moved back and forth in the axial direction by a hydraulic mechanism (not shown) at the shaft center of a chuck body 2 attached to a main shaft such as a lathe. A collet 4 that expands and contracts by moving back and forth is provided.
The chuck body 2 includes an adapter 5 that is fixed to the front surface of the main shaft, a guide 6 that is attached to the adapter 5 and has a rear through-hole 7 in the draw bar 3 at the shaft center, and is attached to the adapter 5 and that has the draw bar 3 at the shaft center. It has a mandrel body 8 having a front through-hole 9, a chuck body 10 attached to the mandrel body 8, and a work locator 11 attached to the front side of the chuck body 10 via a front plate 10a.

The mandrel body 8 includes a flange 12 that is fixed to the adapter 5 with bolts 13, 13,... And a mandrel 14 that projects forwardly from the center of the flange 12, and the flange 12 is threaded in the radial direction. An anti-rotation bolt 15 to be joined, and a locking rod 17 that protrudes into the front through-hole 9 by the anti-rotation bolt 15 and engages a long groove 16 provided on the outer periphery of the draw bar 3 are provided.
The chuck body 10 has a disk shape having a center hole 18 through which the mandrel 14 of the mandrel body 8 coaxially passes, and is fixed to the flange 12 with bolts 19, 19,. In the center hole 18, the rear part that is the outer side of the base of the mandrel 14 has a larger diameter than the front part.

The work locator 11 is provided with stoppers 20, 20... For positioning the workpiece on the front surface on concentric circles, and is fixed to the front surface of the front plate 10 a which is fixed to the front of the chuck body 10 with bolts 21, 21. .
The draw bar 3 passes through the rear through hole 7 of the guide 6 and the front through hole 9 of the mandrel body 8, and an outer tapered surface 22 is formed on the outer periphery of the front end protruding from the mandrel 14 so as to expand forward. Yes.

As shown in FIG. 4, the collet 4 is a cylindrical body that projects in a tapered manner like the mandrel 14, and includes a flange portion 23 at the rear end. Further, an inner tapered surface 24 is formed on the inner periphery of the front end of the collet 4 so as to expand toward the front in accordance with the outer tapered surface 22 of the draw bar 3. Further, the collet 4 is formed with six slits 25, 25,... Radially from the front end to the front side of the flange portion 23, and is divided into six chuck claws 26, 26,. ing.
The collet 4 is externally mounted on the mandrel 14 in the center hole 18 of the chuck body 10, the flange portion 23 is disposed on the flange 12 of the mandrel body 8 at equal intervals in the circumferential direction, and a step portion 28 is provided in the intermediate portion. .. Are fixed coaxially with the mandrel 14 from the front by three stepped bolts 27, 27.

  Here, the step portion 28 of each stepped bolt 27 is formed so that the axial dimension is longer than the thickness of the flange portion 23, and the front end of the step portion 28 is the flange 12 in a state where the flange portion 23 is loosely inserted. It is in contact with the front surface. Therefore, in a state where the stepped bolt 27 is screwed into the flange 12, the collet 4 has a retracted position where the flange portion 23 contacts the flange 12 and an advanced position where the flange portion 23 contacts the head 29 of the stepped bolt 27. It is supported so that it can move back and forth with a stroke between. The base outer peripheral surface 30 of the mandrel 14 and the inner peripheral surface 31 of the flange portion 23 are equal diameter portions that do not taper, and the inner peripheral surface 31 of the flange portion 23 is in sliding contact with the outer peripheral surface 30 of the mandrel 14. However, the back-and-forth movement of the collet 4 is guided. The stroke of the collet 4 moving back and forth is changed to a stepped bolt 27 having a different length of the stepped portion 28, or a washer or the like is interposed between the flange 12 and the stepped portion 28, or between the stepped portion 28 and the head 29. Can be adjusted.

In addition, the flange 12 of the mandrel body 8 at the rear of the flange portion 23 has bottomed holes 32, 32,... That open forward at six locations in the circumferential direction between the stepped bolts 27, 27 at substantially equal intervals. In each bottomed hole 32, coil springs 33 as urging means are accommodated in a compressed state, and the flange portion 23 is urged forward by an elastic force.
Reference numeral 34 denotes a seal member that is externally mounted on the outer periphery of the front end of the collet 4 and seals between the work locator 11 and the collet 4 by being located within the inner diameter of the work locator 11 regardless of the front and rear positions of the collet 4.

  In the collet chuck 1 configured as described above, in the unclamped state in which the draw bar 3 is advanced, the inner tapered surface 24 of the collet 4 is radiated as shown in FIG. It is not pressed in the direction, and the chuck claws 26, 26. Therefore, the collet 4 is urged to an advanced position where the flange portion 23 contacts the head 29 of the stepped bolt 27 by the elastic force of the coil springs 33, 33.

  From here, for example, when clamping a work W having a thin disk shape and having a through hole W1 at the center, the work W is brought into contact with the stopper 20 of the work locator 11 and the chuck claws 26 of the collet 4 are arranged on the inner peripheral surface of the through hole W1. , 26... Are positioned at positions where the front ends are inserted, and the draw bar 3 is moved backward in that state. Then, when the outer taper surface 22 is retracted, each chuck claw 26 to which the inner taper surface 24 is pressed is expanded to clamp the inner peripheral surface of the through hole W1 of the work W, and the collet is retracted along with the retraction of the draw bar 3. 4 is also retracted and retreats against the elastic force of the coil springs 33, 33..., So that the work W clamped on the collet 4 is pressed against the stopper 20 of the work locator 11.

Then, as shown in FIG. 2, when the flange portion 23 comes into contact with the flange 12 of the mandrel body 8, the collet 4 stops retreating, and the work W is no longer drawn and the clamping is completed. Therefore, the workpiece W can be machined by rotating the spindle.
When the workpiece W is unclamped after the machining of the workpiece W, if the draw bar 3 is advanced as described above, the collet 4 released by the advancement of the outer tapered surface 22 is moved to the coil springs 33, 33,. Since it advances to the advance position by the elastic force, the workpiece W is unclamped and can be taken out.
The pulling force of the workpiece W by the collet 4 is determined by the difference between the thrust of the draw bar 3 and the thrust of the coil spring 33. Further, since the amount of the workpiece W drawn by the collet 4 is determined by the slide amount of the collet 4, it can be appropriately set according to the workpiece W by changing the slide amount of the collet 4.

Thus, according to the collet chuck 1 of the above-described form, the collet 4 is provided so as to be slidable in the front-rear direction with a stroke adjustable by the stepped bolt 27, and in the unclamped state, the coil springs 33, 33,. By energizing to the advance position in the stroke, even if the workpiece W is pulled in and clamped, excessive pulling is regulated. Therefore, the workpiece W can be reliably clamped at an appropriate position for sitting on the stopper 20 without deforming the workpiece W, and the machining accuracy can be maintained.
In particular, here, the urging means of the collet 4 is the coil spring 33 that presses the collet 4 from the rear by elastic force, so that the collet 4 can be easily urged to the forward position.

The elastic force of the coil spring (the urging force to the collet) can be rotated by a tool or the like from the rear surface of the collet chuck by screwing an adjustment screw to the bottom of the bottomed hole on the rear side of the coil spring, for example, by replacing the coil spring itself. It can also be adjusted by changing the compression length of the coil spring by screwing the adjusting screw.
The number and arrangement of the coil springs and the number and arrangement of the stepped bolts are not limited to the above forms, and can be changed as appropriate.

  Further, the urging means is not limited to the coil spring, but may be a piston that presses the collet 4 by fluid pressure such as hydraulic pressure. FIG. 5 shows an example. In this collet chuck 1A, a piston 40 is provided in each bottomed hole 32 so as to be movable back and forth, and a pressurizing chamber 41 is formed at the rear thereof. On the other hand, a pressure oil supply passage 42 through which pressure oil is supplied from the outside is formed at the axial center of the draw bar 3, and the outer groove 44 provided on the outer peripheral surface of the draw bar 3 and the inner periphery of the rear through hole 7 of the guide 6. A ring-shaped passage 43 communicating with the pressure oil supply passage 42 is formed between the inner groove 45 provided on the surface. The ring-shaped passage 43 communicates with the pressurizing chamber 41 through communication passages 46 and 47 provided in the guide 6 and the flange 12. Other configurations are the same as those in FIGS.

Therefore, in the unclamped state in which the draw bar 3 moves forward, the pressure oil supplied to the pressure oil supply passage 42 is supplied to the pressurizing chamber 41 via the ring-shaped passage 43 and the communication passages 46 and 47, so that the piston 40 Is pushed forward, and the collet 4 is urged to an advanced position where the flange portion 23 abuts against the head portion 29 of the stepped bolt 27.
When the work W is clamped from here, the work W is brought into contact with the stopper 20 of the work locator 11 so that the front ends of the chuck claws 26, 26,. The draw bar 3 is moved backward in the positioned state. Then, when the outer taper surface 22 is retracted, each chuck claw 26 to which the inner taper surface 24 is pressed is expanded to clamp the inner peripheral surface of the through hole W1 of the work W, and the collet is retracted along with the retraction of the draw bar 3. 4 is also retracted and retreats against the bias of the pistons 40, 40..., So that the work W clamped on the collet 4 is pressed against the stopper 20 of the work locator 11.

Then, when the flange portion 23 comes into contact with the flange 12 of the mandrel body 8, the collet 4 stops retreating, and no further drawing of the workpiece W occurs and the clamping is completed. Therefore, the workpiece W can be machined by rotating the spindle.
When the workpiece W is unclamped after the machining of the workpiece W, if the draw bar 3 is advanced as described above, the collet 4 released by the advancement of the outer tapered surface 22 is moved to the piston 40, 40,. Since the work moves forward to the forward movement position by the urging force, the work W is unclamped and can be taken out.
The pulling force of the workpiece W by the collet 4 is determined by the difference between the thrust of the draw bar 3 and the thrust of the piston 40. Further, since the amount of the workpiece W drawn by the collet 4 is determined by the slide amount of the collet 4, it can be appropriately set according to the workpiece W by changing the slide amount of the collet 4.

Even in the collet chuck 1A, even if the workpiece W is pulled and clamped, the pulling more than necessary is restricted. Therefore, the workpiece W can be reliably clamped at an appropriate position for sitting on the stopper 20 without deforming the workpiece W, and the machining accuracy can be maintained.
In particular, here, the biasing means of the collet 4 is the piston 40 that presses the collet 4 from the rear by hydraulic pressure, so that the pulling force can be easily adjusted by changing the hydraulic pressure.
In this modified example, the number and arrangement of the pistons can be changed as appropriate, and the fluid pressure applied to the pistons can be compressed air instead of pressurized oil.

  1, 1A ··· Collet chuck 2 ··· Chuck body 3 · · Drawbar 4 · · Collet 8 · · Mandrel body 10 · · Chuck body 11 · · · Work locator 12 · · · Flange 13, 19 ··· Bolt, 14 ·· Mandrel, 18 ·· Center hole, 20 ·· Stopper, 22 ·· Outer taper surface, 23 ·· Flange, 24 ·· Inner taper surface, 25 ·· Slit, 26 ·· Chuck claw, 27 ·· Stepped bolt, 28 ·· Stepped portion, 29 ·· Head, 32 ·· Bottomed hole, 33 ·· Coil spring, 40 ·· Piston, 41 ·· Pressurizing chamber, 42 ·· Pressure Oil supply path, W ... work, W1 ... through hole.

Claims (3)

In a chuck body provided with a stopper for positioning a workpiece on the front surface, a collet capable of clamping / unclamping the workpiece by expanding and contracting in the workpiece abutting on the stopper, and advancing and retreating at the center of the collet, A collet chuck provided with a draw bar that contracts the collet as it moves forward and performs an unclamping operation, and expands the collet as it moves backward and performs a clamping operation;
The collet chuck is provided so as to be slidable in the front-rear direction with a predetermined adjustable stroke, and in an unclamped state, the collet is urged to an advanced position in the stroke.   The collet chuck according to claim 1, wherein the biasing means is a coil spring that presses the collet from behind by an elastic force.   The collet chuck according to claim 1, wherein the biasing means is a piston that presses the collet from behind by fluid pressure.

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