Retractable chuck

Abstract

To provide a pull-in type chuck capable of strengthening gripping force on a workpiece by preventing displacement of a master jaw.SOLUTION: In a pull-in type chuck, when a plunger 20 is moved backward, respective master jaws 30 are guided by an inclined guide hole α2 and a plurality of jaws 40 approach to each other, thus placing the chuck in a chucked state in which a workpiece W arranged between the plurality of jaws 40 is gripped, and when the plunger 20 is moved forward, the respective master jaws 30 are guided by the inclined guide hole α2 and the plurality of jaws 40 separate from each other, thus placing the chuck in a non-chucked state in which gripping of the workpiece W is released. A back-up part α3 that abuts from outward to a rear end part of the master jaw 30 in the chucked state is provided on the inner peripheral side of a peripheral wall part 12 of a body 10.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a draw-in type chuck used for gripping a workpiece with a machining apparatus such as a lathe.

Background Art

[0002] In machining apparatuses such as lathes, a workpiece to be machined is gripped by a chuck. FIG. 2 of Patent Document 1 discloses a draw-in type chuck in which a shaft 5 (master jaw) and a plunger 4 are assembled to a chuck body 1 (body). The master jaw 5 is inserted into an inclined guide hole formed in the front wall portion of the body 1. A claw 6 (jaw) for chucking the workpiece W is attached to the front end portion of the master jaw 5, and the rear end portion of the master jaw 5 is engaged with the plunger 4. As shown in FIG. 5 of the same document, a plurality of sets of the master jaw 5 and the jaw 6 are provided and arranged rotationally symmetrically with respect to the body 1.

[0003] In the draw-in type chuck of Patent Document 1, when the plunger 4 is moved rearward (opposite side to the workpiece W) from the state shown in FIG. 3 of the same document, each master jaw 5 is guided by the inclined guide hole, and the plurality of jaws 6 approach each other, so that, as shown in FIG. 4 of the same document, the workpiece W is in a chucked state. On the other hand, when the plunger 4 is moved forward (towards the workpiece W side) from the state shown in FIG. 4 of the same document, each master jaw 5 is guided by the inclined guide hole, and the plurality of jaws 6 move away from each other, so that, as shown in FIG. 3 of the same document, the workpiece W is in a non-chucked state where the gripping is released.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a retractable chuck having the structure described above, the gripping force on the workpiece can be increased by increasing the force pulling in the plunger. However, as shown in Figure 1 of this application, when the plunger 20 is moved backward to form a chuck, under certain conditions, the rear end of the master jaw 30 may bend outward with point P1 as the pivot point (see the dashed line in the figure). As a result, the retraction force F1 transmitted from the plunger 20 to the master jaw 30 is consumed by the displacement of the master jaw 30, which limits the increase in the gripping force F2 of the workpiece W. There was also the problem that it was difficult to secure a wide stroke range (the stroke range of the plunger 6) that could properly grip the workpiece W.

[0006] In this regard, even with the retractable chuck of Patent Document 1, if the master jaw 6 is made thicker, it can be made less likely for the master jaw 6 to be displaced. However, in this case, the dimensions of the retractable chuck become larger, and the weight also increases. In lathes and the like, the workpiece W is rotated by rotating the retractable chuck, and if the weight of the retractable chuck increases, the centrifugal force acting on the retractable chuck increases, and the loss of gripping force due to that centrifugal force increases. For this reason, it becomes difficult to rotate the retractable chuck at high speed.

[0007] This invention was made to solve the above problems and provides a retractable chuck that can prevent displacement of the master jaw and strengthen the gripping force of the workpiece. Another objective of this invention is to provide a retractable chuck that can secure a wide stroke range for properly gripping the workpiece. Furthermore, another objective of this invention is to realize such a retractable chuck without increasing the size or weight of the device. [Means for solving the problem]

[0008] The above issues are, A body having a front wall portion in which multiple inclined guide holes are formed, and a peripheral wall portion that surrounds the space behind the front wall portion (hereinafter referred to as the "cavity portion"), A plunger positioned in the cavity of the body, which is movable in the front-to-back direction, A master jaw is inserted into each inclined guide hole, with its rear end engaged with the plunger, The jaws attached to the front end of each Master Jaw Equipped with, When the plunger is moved backward, each master jaw is guided by the inclined guide hole, and as the multiple jaws move closer to each other, the workpiece placed between the multiple jaws is gripped, creating a chuck state. When the plunger is moved forward, each master jaw is guided by the inclined guide hole, and the multiple jaws separate from each other, resulting in a non-chucked state where the workpiece is released. It is a retractable chuck, A retractable chuck characterized by having a backup portion that contacts the rear end of the master jaw from the outside when it is in the chuck state, provided on the inner circumference of the peripheral wall of the body. This is solved by providing [a solution].

[0009] In the retractable chuck of the present invention, the rear end of the master jaw is supported from the outside by a backup part when the chuck is engaged. This prevents the rear end of the master jaw from bending outward when the chuck is engaged, and allows most of the retraction force transmitted from the plunger to the master jaw to be used for gripping the workpiece. Therefore, it is possible to increase the gripping force of the workpiece without increasing the thickness of the master jaw. In addition, it is possible to secure a wide stroke range in which the workpiece can be properly gripped. Furthermore, since the dimensions of the retractable chuck can be reduced and the weight reduced, it becomes possible to rotate the retractable chuck at high speed when using it on a lathe or the like.

[0010] In the retractable chuck of the present invention, it is preferable to attach a sealing ring to the outer circumference of the master jaw to seal the gap between the inclined guide hole and the outer circumference of the master jaw. This is because if workpiece chips or cutting fluid enter the body through the gap, malfunctions such as the retractable chuck not functioning properly may occur, and sealing the gap can suppress the occurrence of such malfunctions.

[0011] However, if a seal ring is attached to the outer circumference of the master jaw, there is a risk that the seal ring may get caught on the body and be damaged or cut when assembling the master jaw to the body (when inserting the master jaw from the rear end of the inclined guide hole). For this reason, it is preferable to provide a recess to allow the seal ring to escape when inserting the master jaw in the area between the inclined guide hole and the backup portion on the inner circumference of the peripheral wall of the body. This makes it less likely for the seal ring to get caught on the body (especially on the inner surface of the peripheral wall of the body, in the area located behind the inclined guide hole) when inserting the master jaw.

[0012] However, in the retractable chuck of the present invention, since a backup portion is provided on the inner circumference side of the peripheral wall portion of the body, even if a recessed portion is provided in the area between the inclined guide hole and the backup portion as described above, when assembling the master jaw to the body (when inserting the master jaw from the rear end side of the inclined guide hole), there is a risk that the seal ring may get caught around the backup portion until it reaches the area where the recessed portion is provided (while the seal ring is overlapping the backup portion). For this reason, it is preferable to provide a notch on the outer circumference of the front end side of the master jaw, and to have a structure in which the master jaw can be moved to the opposite side from the backup portion inside the inclined guide hole while the seal ring overlaps the backup portion during master jaw insertion (while the front end side of the master jaw is inserted into the inclined guide hole). This makes it possible to prevent the seal ring from getting caught around the backup portion.

[0013] In the retractable chuck of the present invention, the manner in which the master jaw and the plunger engage is not particularly limited. However, if the area around the engaging portion of the master jaw or plunger has a complex structure, it becomes difficult to increase the rigidity of the area around the engaging portion of the master jaw, etc., and that part may become more susceptible to displacement. For this reason, it is preferable to make the area around the engaging portion of the master jaw, etc., as simple as possible. Specifically, it is preferable to provide an engaging projection on the outer circumference of the plunger, and an engaging recess on the outer circumference of the rear end side of the master jaw, on the side opposite to the backup portion, and to engage the master jaw with the plunger by fitting the engaging projection into the engaging recess. [Effects of the Invention]

[0014] As described above, the present invention makes it possible to provide a retractable chuck that can prevent displacement of the master jaw and strengthen the gripping force of the workpiece. It also makes it possible to provide a retractable chuck that can secure a wide stroke range for properly gripping the workpiece. Furthermore, it makes it possible to realize such a retractable chuck without increasing the size or weight of the device. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view of a conventional retractable chuck, showing how the master jaws are displaced when the chuck is in the chuck position, cut across a plane containing the center line L1. [Figure 2] This is a cross-sectional view of the retractable chuck of this embodiment when it is in the non-chucked state, cut by a plane including the center line L1. [Figure 3] This is a cross-sectional view of the retractable chuck of this embodiment when it is in the chucked state, taken by cutting it through a plane containing the center line L1. [Figure 4]FIG. is a cross-sectional view taken along a plane including the center line L1, showing a state in which a master jaw is inserted into the inclined guide hole of the body in the draw-in type chuck of the present embodiment, when the seal ring on the outer peripheral portion of the master jaw is in the first region. [Figure 5] FIG. is a cross-sectional view taken along a plane including the center line L1, showing a state in which a master jaw is inserted into the inclined guide hole of the body in the draw-in type chuck of the present embodiment, when the seal ring on the outer peripheral portion of the master jaw is at the boundary between the first region and the second region. [Figure 6] FIG. is a cross-sectional view taken along a plane including the center line L1, showing a state in which a master jaw is inserted into the inclined guide hole of the body in the draw-in type chuck of the present embodiment, when the seal ring on the outer peripheral portion of the master jaw is at the boundary between the second region and the third region. [Figure 7] FIG. is a cross-sectional view taken along a plane including the center line L1, showing a state in which a master jaw is inserted into the inclined guide hole of the body in the draw-in type chuck of the present embodiment, when the seal ring on the outer peripheral portion of the master jaw is in the third region. [Figure 8] FIG. is a cross-sectional view taken along a plane including the center line L1, showing a state in which the master jaw is displaced when the draw-in type chuck of the present embodiment is in the chucked state. [Figure 9] FIG. shows the vicinity of the front end of the master jaw (without notch) in the draw-in type chuck. [Figure 10] FIG. shows the vicinity of the front end of the master jaw (with notch) in the draw-in type chuck.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Preferred embodiments of the retractable chuck of the present invention will be described in more detail with reference to the drawings. Figures 2 and 3 are cross-sectional views of the retractable chuck of this embodiment, cut along a plane containing the center line L1. Figure 2 shows the retractable chuck in the un-chucked state (the state in which the workpiece W is released), and Figure 3 shows the retractable chuck in the chucked state (the state in which the workpiece W is gripped). In the following description, for convenience of explanation, the upper side of each drawing (the side on which the workpiece W is placed) will be referred to as the "front" side, and the lower side of each drawing (the side opposite to the side on which the workpiece W is placed) will be referred to as the "rear" side.

[0017] The retractable chuck of this embodiment is used to grip a workpiece in a machining device such as a lathe. As shown in Figure 2, this retractable chuck comprises a body 10, a plunger 20, a master jaw 30, and a jaw 40. In Figure 2 and other figures, only one set of master jaws 30 and jaws 40 is depicted, but in reality, multiple sets are arranged to surround the workpiece W. In this embodiment, three sets of master jaws 30 and jaws 40 are arranged rotationally symmetrically around the center line L1. The workpiece W is gripped by its outer circumference by the jaws 40.

[0018] Body 10 is used to assemble the various components that make up the retractable chuck. Body 10 consists of a front wall portion 11 on the workpiece W side, a peripheral wall portion 12 that surrounds the space (cavity portion α1) behind the front wall portion 11, and a rear wall portion 13 that covers the rear of the peripheral wall portion 11. A locator 70 for positioning the workpiece W in a direction along the center line L1 is positioned further in front of the front wall portion 11. An inclined guide hole α2 is formed in the front wall portion 11. This inclined guide hole α2 penetrates in a direction inclined with respect to the center line L1. The inclined guide hole α2 is for guiding the master jaw 30. For this reason, the inclined guide hole α2 is provided in multiple locations, similar to the master jaw 30. Of the body 10, the front wall portion 11 and the peripheral wall portion 12 are formed integrally, but the rear wall portion 13 is attached to the peripheral wall portion 12 in a detachable manner. When assembling parts such as the plunger 20 to the body 10, the rear wall section 13 is removed. This rear wall section 13 is also called the "rear body".

[0019] The plunger 20 is positioned in the cavity α1 of the body 10 so as to be movable in the front-rear direction (parallel to the center line L1). The rear end of the plunger 20 is connected to a plunger driving means (not shown) for moving the plunger 20 in the front-rear direction. In this embodiment, a drawbar (not shown) is used as the plunger driving means, and the driving force of the drawbar is transmitted to the plunger 20 by screwing the rear end (threaded portion) of the draw screw 50 attached to the plunger 20 into the drawbar. Engaging projections 21 are formed on the outer circumference of the plunger 20 for engaging with the rear end of the master jaw 30. These engaging projections 21 are provided at locations corresponding to each master jaw 30 (in this embodiment, three locations that are rotationally symmetrical around the center line L1).

[0020] The master jaw 30 is for transmitting the driving force transmitted from the drawbar (plunger driving means) to the plunger 20 to the jaw 40. A mounting recess 32 is provided on the inward-facing surface (the surface facing the center line L1) at the front end of each master jaw 30. The jaw 40 is mounted in this mounting recess 32 with its protrusion inward (towards the center line L1). As already mentioned, multiple sets of master jaws 30 and jaws 40 are arranged, and these master jaws 30 are each inserted into the inclined guide holes α2 of the body 10.

[0021] Insertion of the master jaw 30 into the inclined guide hole α2 is usually performed from the rear end side (hollow α1 side) of the inclined guide hole α2, as shown in Figures 4 to 7. This is because the mounting recess 32 is formed at the front end of the master jaw 30, and the cross-sectional area of ​​the front end of the master jaw 30 is smaller than that of the rear end, making it easier to insert the master jaw 30 from the lower end side of the inclined guide hole α2. Figures 4 to 7 are cross-sectional views taken by a plane including the center line L1, showing the insertion of the master jaw 30 into the inclined guide hole α2 of the body 10 in the retractable chuck of this embodiment. Figure 4 shows the case when the seal ring 60, which will be described later, is in the first region β1, Figure 5 shows the case when the seal ring 60 is at the boundary between the first region β1 and the second region β2, Figure 6 shows the case when the seal ring 60 is at the boundary between the second region β2 and the third region β3, and Figure 7 shows the case when the seal ring 60 is in the third region β3.

[0022] Furthermore, in this embodiment, a seal ring 60 is attached to the outer circumference of the master jaw 30. This seal ring 60 is fitted into a groove that is provided in an annular shape along the outer circumference of the master jaw 30. This seal ring 60 seals the gap between the inner surface of the inclined guide hole α2 and the outer surface of the master jaw 30. Therefore, chips from the workpiece W, cutting fluid, etc. are less likely to enter the body 10 through this gap.

[0023] Furthermore, each master jaw 30 is provided with an engagement recess 31 at its rear end. The engagement projection 21 of the plunger 20 engages with this engagement recess 31. In this embodiment, after assembling the master jaw 30 to the body 10 and inserting the plunger 20 into the cavity α1, the plunger 20 is twisted around the center line L1 to engage the engagement projection 21 with the engagement recess 31. At the engagement point between the engagement projection 21 and the engagement recess 31, the movement of the master jaw 30 in the front-rear direction (parallel to the center line L1) relative to the plunger 20 is restricted. In contrast, the movement of the master jaw 30 in the lateral direction (perpendicular to the center line L1) relative to the plunger 20 is not particularly restricted.

[0024] Therefore, when the plunger driving means is driven from the non-chucked state shown in Figure 2 to move the plunger 20 backward (pull the plunger 20 backward) as shown in Figure 3, the master jaw 30 is also pulled backward within the inclined guide hole α2. The inclined guide hole α2 is inclined with respect to the center line L1 such that its rear end is closer to the center line L1 than its front end. Therefore, as the master jaw 30 moves backward within the inclined guide hole α2, it moves inward (towards the side approaching the center line L1). At this time, the jaw 40 also moves inward, and the workpiece W is gripped by the jaw 40, resulting in a chucked state. In the chucked state, the engagement of the engaging projection 21 with the engaging recess 31 deepens.

[0025] On the other hand, when the plunger 20 is moved forward from the chuck state shown in Figure 3 (the plunger 20 is pushed forward), the master jaw 30 is pushed forward by the plunger 20 and moves forward within the inclined guide hole α2, as shown in Figure 2. Because the inclined guide hole α2 is inclined as described above, as the master jaw 30 moves forward within the inclined guide hole α2, it moves outward (away from the center line L1). At this time, the jaw 40 also moves outward, and the grip of the workpiece W by the jaw 40 is released, resulting in an unchucked state. In the unchucked state, the engagement of the engaging projection 21 with the engaging recess 31 becomes shallower.

[0026] Thus, in a retractable chuck, the chuck state is achieved when the master jaw 30 is retracted backward by the plunger 20 (Figure 3), and the non-chuck state is achieved when the master jaw 30 is pushed forward by the plunger 20 (Figure 2). However, in conventional retractable chucks, as shown in Figure 1, when in the chuck state, the rear end of the master jaw 30 bends outward with point P1 as the pivot point, which presents a problem in that it is difficult to increase the gripping force of the workpiece W. In this regard, in the retractable chuck according to the present invention, as shown in Figure 3, a backup part α3 is provided on the inner circumference side of the peripheral wall 12 of the body 10 that contacts the rear end of the master jaw 30 from the outside (opposite side from the center line L1) when in the chuck state.

[0027] Therefore, as shown in Figure 8, the rear end of the master jaw 30 when it is in the chuck state is supported from the outside by the backup part α3, which suppresses bending of the rear end of the master jaw 30. Figure 8 is a cross-sectional view taken by cutting through a plane including the center line L1, showing how the master jaw 30 is displaced (or hardly displaced) when the retractable chuck of this embodiment is in the chuck state. The dashed line in Figure 8 represents the bending of the rear end of the master jaw 30 that would be assumed if the backup part α3 were not present. Therefore, most of the retraction force F1 transmitted from the plunger 20 to the master jaw 30 is exerted on gripping the workpiece W. Thus, it is possible to increase the gripping force F2 of the workpiece W without making the master jaw 30 thicker. In addition, it is possible to secure a wide stroke range (stroke range in the front-rear direction of the plunger 20) in which the workpiece W can be properly gripped. Furthermore, since the dimensions of the retractable chuck can be reduced and the weight reduced, it is also possible to rotate the retractable chuck at high speed.

[0028] Furthermore, in this embodiment, a support portion 14 is provided on the body 10 at a location outside the front end of the master jaw 30. When the jaw 40 grips the workpiece W, a reaction force (reaction force of the gripping force F2) is applied from the workpiece W to the jaw 30, and this reaction force may cause the front end of the master jaw 30 to bend outward. The support portion 14 supports the front end of the master jaw 30 from the outside, thereby suppressing the bending of the master jaw 30. This support portion 14 is provided in a state that protrudes forward from the front wall portion 11 of the body 10.

[0029] Incidentally, as described above, if the seal ring 60 is attached to the outer circumference of the master jaw 30, as shown in Figures 4 to 7, when the master jaw 30 is inserted from the rear end side of the inclined guide hole α2, there is a risk that the seal ring 60 may get caught on the body 10 and be damaged or cut. There is also a risk that the seal ring 60 may fall out of the groove on the outer circumference of the master jaw 30. For this reason, in this embodiment, a recessed portion α4 is provided in the body 10 to allow the seal ring 60 to escape. This recessed portion α4 is provided in the area between the inclined guide hole α2 and the backup portion α3 on the inner circumference side of the peripheral wall portion 12 of the body 10 (second region β2 in Figures 4 to 7). This allows the seal ring 60 to escape into the recessed portion α4 when it moves through the second region β2. Therefore, damage to or detachment of the seal ring 60 can be prevented.

[0030] However, as described above, if a backup portion α3 is provided on the inner circumference side of the peripheral wall portion 12 of the body 10, even if a hijacking portion α4 is provided in the area between the inclined guide hole α2 and the backup portion α3, there is a risk that the seal ring 60 may get caught around the backup portion α3. For this reason, in this embodiment, as shown in Figure 4, while the seal ring 60 overlaps with the backup portion α3 (when the seal ring 60 moves through the first region β1), the master jaw 30 can be moved to the opposite side of the backup portion α3 (towards the center line L1) inside the inclined guide hole α2. Looking at Figure 4, it can be seen that the center line L3 of the master jaw 30 is located inward (towards the center line L1) than the center line L2 of the inclined guide hole α2. For this reason, the seal ring 60 can be moved in the first region β1 without coming into contact with the backup portion α3.

[0031] Specifically, it is as follows: As already mentioned, the front end of the master jaw 30 is provided with a mounting recess 32 for attaching the jaw 40. In conventional retractable chucks, the front end of the master jaw 30 has a shape like a cylinder with a part cut off, as shown in Figure 9(a), and its horizontal cross-section (cross-section cut by a plane perpendicular to the center line L1 (Figure 1)) is partially elliptical. As shown in Figure 9(b), this elliptical portion occupies more than half of the cross-section of the inclined guide hole α2, so even though the front end of the master jaw 30 has a mounting recess 32, there is almost no play in the inclined guide hole α2 (it is almost impossible to move it horizontally in the inclined guide hole α2). Figure 9 shows the vicinity of the front end of the master jaw 30 (without the notch) in a retractable chuck.

[0032] In this embodiment, as shown in Figure 10(a), a notch α5 is provided on the outer circumference of the front end of the master jaw 30. A pair of these notches α5 are provided on both sides of the mounting recess 32. Therefore, as shown in Figure 10(b), when the front end of the master jaw 30 is inserted into the inclined guide hole α2, the front end of the master jaw 30 can be moved horizontally within the inclined guide hole α2. Accordingly, as shown in Figure 4, when the front end of the master jaw 30 is inserted into the inclined guide hole α2, if the seal ring 60 is positioned so that it overlaps with the first region β1 where the backup portion α3 is located, the master jaw 30 can be moved towards the center line L1 side of the retractable chuck (right side of the page in Figure 4), and the seal ring 60 can be prevented from hitting the backup portion α3. Figure 10 shows the vicinity of the front end of the master jaw 30 (with the notch α5) in a retractable chuck.

[0033] As the master jaw 30 is further inserted into the inclined guide hole α2 from the state shown in Figure 4, the entire portion of the master jaw 30 with the mounting recess 32 is inserted into the inclined guide hole α2, as shown in Figure 5. From this point onward, the master jaw 30 cannot be inserted further into the inclined guide hole α2 unless it is moved back from the side of the centerline L1 of the retractable chuck to the side of the peripheral wall 12 of the body 10. For this reason, in Figure 5, the centerline L3 of the master jaw 30 is aligned with the centerline of the inclined guide hole α2. At this time, as shown in Figure 5, the seal ring 60 is moved towards the side of the peripheral wall 12 of the body 10, but the seal ring 60 has reached the second region β2 where the hilt portion α4 is provided. Therefore, when the seal ring 60 is in the second region β2, the seal ring 60 can be released by the hilt portion α4.

[0034] Subsequently, as shown in Figure 6, when the seal ring 60 reaches the lower end of the inclined guide hole α2 (the boundary between the second region β2 and the third region β3), the seal ring 60 receives force almost uniformly from the inner circumference of the inclined guide hole α2 thereafter, so that no localized force is applied to the seal ring 60, the master jaw 30 can be inserted smoothly (Figure 7). Once the master jaw 30 has been inserted into the inclined guide hole α2, the jaw 40 (Figure 2) is attached to the front end of the master jaw 30, and the plunger 20 (Figure 2) is inserted into the cavity α1 of the body 10 to engage the engaging projection 21 with the engaging recess 22. After that, the rear side of the body 10 is covered with the rear wall 13 (rear body), and the assembly of the retractable chuck is completed.

[0035] The retractable chuck according to the present invention described above can be used in various applications where it is necessary to grip a workpiece W. In particular, it can be suitably used in workpiece processing equipment that processes a workpiece W, and can be especially suitably used in lathes that perform cutting while rotating the workpiece W. [Explanation of Symbols]

[0036] 10 Body 11 Front wall 12 Peripheral wall section 20 plungers 21 Engagement protrusion 30 Master Joe 31 Engaging recess 40 Joe 60 sealing rings α1 cavity α2 Inclined Guide Hole α3 Backup Unit α4 Nusumi section α5 notch Double job

Claims

1. A body having a front wall portion in which multiple inclined guide holes are formed, and a peripheral wall portion that surrounds the space behind the front wall portion (hereinafter referred to as the "cavity portion"), A plunger positioned in the cavity of the body, which is movable in the front-to-back direction, A master jaw is inserted into each inclined guide hole, with its rear end engaged with the plunger, The jaws attached to the front end of each Master Jaw Equipped with, When the plunger is moved backward, each master jaw is guided by the inclined guide hole, and as the multiple jaws move closer to each other, the workpiece placed between the multiple jaws is gripped, creating a chuck state. When the plunger is moved forward, each master jaw is guided by the inclined guide hole, and the multiple jaws separate from each other, resulting in a non-chucked state where the workpiece is released. It is a retractable chuck, A backup portion is provided on the inner circumference of the peripheral wall of the body, which contacts the rear end of the master jaw from the outside when it is in the chuck state. A sealing ring for sealing the gap between the inclined guide hole and the outer surface of the master jaw is attached to the outer circumference of the master jaw. A retractable chuck characterized in that a recess for relieving the seal ring when inserting the master jaw, which is inserted from the rear end side of the inclined guide hole, is provided in the section from the rear end opening of the inclined guide hole to the backup section on the inner circumference side of the peripheral wall of the body.

2. A notch is provided on the outer circumference of the front end of the master jaw. The notch allows the master jaw to be moved to the opposite side of the backup portion within the inclined guide hole while the seal ring overlaps the backup portion during master jaw insertion. The retractable chuck according to claim 1.

3. An engaging projection is provided on the outer circumference of the plunger. An engagement recess is provided on the outer circumference of the rear end of the master jaw, on the side opposite to the backup portion. The master jaw engages with the plunger by fitting the engaging projection into the engaging recess. The retractable chuck according to claim 1.

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