WO2002057039A1

WO2002057039A1 - Chuck

Info

Publication number: WO2002057039A1
Application number: PCT/IL2001/001181
Authority: WO
Inventors: Hanoch Guy
Original assignee: E T M Precision Tool Manufacturing Ltd
Current assignee: E T M Precision Tool Manufacturing Ltd
Priority date: 2001-01-17
Filing date: 2001-12-19
Publication date: 2002-07-25
Anticipated expiration: 2003-07-17
Also published as: IL140936A0

Abstract

A chuck (10) comprising a holder body (12) having a shank portion (14), a gripping flange (16) having a thread (50), and a chuck sleeve (18) having a tapered outer circumferential surface (20) whose diameter (D) decreases forwardly. A clamp sleeve (32) having a thread (74) is fitted onto the chuck sleeve (18) such that the clamp sleeve is rotatable and axially movable relative to the chuck sleeve. The clamp sleeve having a tapered inner circumferential surface (33) whose diameter decreases forwardly. A plurality of needle rollers (30), are disposed between the outer circumferential surface (20) of the chuck sleeve (18) and the inner circumferential surface (33) of the clamp sleeve (32). The needle rollers incline in the circumferential direction at a predetermined angle (β) with respect to the axis (A) of the chuck. The clamp sleeve is rotated to cause the needle rollers to revolve spirally about the axis of the chuck. Upon threadingly engaging the thread (50) of the clamp sleeve (32) with the thread (74) of the holder body, a rear axial abutment surface (54) of the clamp sleeve (32) is forcibly pressed against a front axial abutment surface (46, 64, 82) of the holder body.

Description

CHUCK

FIELD OF THE INVENTION

The present invention relates to a chuck for chucking a cutting tool and more particularly to a chuck in which a clamp sleeve is fitted onto the outer circumference of a chuck sleeve of a holder body via needle rollers, and in which, through rotation of the clamp sleeve in a clamping direction, the diameter of the chuck sleeve is reduced in order to tightly chuck a desired tool.

BACKGROUND OF THE INVENTION

A conventional chuck as disclosed, for example, in U.S. Patent No. 6,105,974 to Matsumoto will be described with reference to Figs. 1, 4 and 5.

As shown, a tool chuck 10, having an axis A, has a holder body 12. The holder body 12 has a tapered shank portion 14 to be inserted into a spindle of a machine tool (not shown), a gripping flange 16 formed at the larger-diameter end of the tapered shank portion 14, and a chuck sleeve 18 that extends from the end surface of the flange 16 opposite the tapered shank portion 14 and co-axially therewith. A tapered surface 20 on the outer circumference of the chuck sleeve 18 forms an angle 0 with the axis A such that the diameter of the surface 20 decreases toward the forward end portion 22 thereof. A roller retaining sleeve 24 is fitted co-axially onto the outer circumference of the chuck sleeve 18 with a clearance therebetween. The diameter of the roller retaining sleeve 24 decreases toward the forward end 26 thereof at the same rate as that of the tapered surface 20 of the chuck sleeve 18. The roller retaining sleeve 24 is held by a retainer ring 28 provided on the outer circumference of the forward end portion 22 of the chuck sleeve 18 such that the roller retaining sleeve 24 is prevented from coming off the chuck sleeve 18.

In the roller retaining sleeve 24, a plurality of needle rollers 30, each having an axis B, are disposed to form a plurality of rows. The needle rollers 30 are fitted into the roller retaining sleeve 24 in such a manner that the needle rollers incline in the circumferential direction at a predetermined angle β (see Fig. 4) with respect to the axis A of the chuck 10. Each of the needle rollers 30 has a first diameter Dl greater than the wall thickness L of the roller retaining sleeve 24, so that the portion of each needle 30 projecting inward from the inner circumferential surface 25 of the roller retaining sleeve 24 is in contact with the tapered surface 20 of the chuck sleeve 18, while the portion of each needle roller 30 projecting outward from the outer circumferential surface 27 of the roller retaining sleeve 24 is in contact with the inner circumferential surface of a clamp sleeve 32.

The clamp sleeve 32 is adapted to decrease the diameter of the chuck sleeve 18 for tightly chucking a desired tool. The clamp sleeve 32 is fitted onto the outer circumference of the chuck sleeve 18 via the needle rollers 30 held by the roller retaining sleeve 24. The clamp sleeve 32 has a tapered inner circumferential surface 33 whose diameter decreases from the end facing the flange 16 toward the forward end portion 34 of the clamp sleeve 32. A sealing/retaining ring 36 is attached to the rear portion of the inner circumference of the clamp sleeve 32 adjacent to the flange 16. The sealing/retaining ring 36 is in contact with the outer circumferential surface of the chuck sleeve 18 so as to provide a sealing function. The sealing/retaining ring 36 also abuts the rear end surface of the roller retaining sleeve 24 in order to prevent the clamp sleeve 32 from coming off the chuck sleeve 18.

In a conventional chuck having the above-described structure, when a tool 38, having a shank 40, is to be chucked, a spring collet 42 is fitted onto the shank 40 of the tool 38, and the shank 40 of the tool, together with the spring collet 42, are inserted into the cylindrical bore 19 of the chuck sleeve 18. When the clamp sleeve 32 is rotated clockwise, as shown by the arrow F in Figs. 3 and 4, each needle roller 30 in contact with the tapered inner surface 33 of the clamp sleeve 32 revolves spirally, about the axis A, along the outer surface of the chuck sleeve 18 while rotating about its own axis B. Thus, the roller retaining sleeve 24 moves toward the flange 16, while rotating, in accordance with the revolution of the needle rollers 30, and at the same time the clamp sleeve 32 also moves toward the flange 16. The movements of the roller retaining sleeve 24 and the clamp sleeve 32 toward the flange 16 reduce the clearance between the tapered inner surface 33 of the clamp sleeve 32 and the tapered outer surface 20 of the chuck sleeve 18, so that the clamp sleeve 32 strongly presses the tapered outer surface 20 of the chuck sleeve 18 via the needle rollers 30 in order to reduce the diameter of the chuck sleeve 18. As a result, the shank 40 of the tool 38 inserted into the cylindrical bore 19 of the chuck sleeve 18 is clamped and held by the chuck sleeve 18 via the spring collet 42.

When the clamp sleeve 32 in a clamped state is rotated counterclockwise, it forces, by means of the sealing/retaining ring 36, the roller retaining sleeve 24 to rotate counterclockwise and move forwardly toward the forward end of the chuck sleeve 18. The forward movement of the roller retaining sleeve 24 together with the forward movement of the needle rollers 30 retained therein release the pressure applied on the chuck sleeve 18 so that the chuck sleeve restores its original diameter. By that, the clamping force applied to the tool 38 is released, and the tool 38 can be removed from the chuck, sleeve 42.

A chuck of the kind described above has various disadvantages. When rotating the clamp sleeve 32 clockwise in a clamping direction, the largest clamping force applied on the tool shank 40 is obtained when the rear face 44 of the clamp sleeve 32 reaches the front face 46 of the flange 16. At this position, since there is no element that forcibly joins the rear face 44 of the clamp sleeve to the front face 46 of the flange, further tightening of the clamp sleeve 32 will cause its slipping around the axis A of the chuck without exerting additional join force between the rear face 44 of the clamp sleeve and the front face 46 of the flange, and, without increasing the clamping force applied on the tool 38 by the chuck 10.

Since the rear face 44 of the clamp sleeve 32 is not forcibly joined to the front face 46 of the flange 16, the effective diameter of the chuck is limited to the external second diameter D2 of the chuck sleeve 18 at a rear portion thereof. The term "effective diameter" refers herein to the smallest diameter in which failure of the chuck due to overload may occur. The limitation of the effective diameter limits the functioning of the chuck, since, despite the fact that the chuck encounters a very strong clamping force upon the tool inserted therein, the chuck is limited by the radial cutting forces applied on the tool during machining. Since the rear face 44 of the clamp sleeve 32 is not forcibly joined to the front face 46 of the flange 16, the radial cutting forces applied on the tool 38 during machining, together with vibrations of the entire system including machine, tool and workpiece, cause separation of the rear face 44 of the clamp sleeve 32 from the front face 46 of the flange 16. Due to the fact that the inner surface 33 of the clamp sleeve 32 and the external surface 20 of the chuck sleeve 18 taper forwardly, the movement of the clamp sleeve 32 will cause it to move forwardly and decrease the clamping force applied by the chuck sleeve 18 on the tool shank 40. It is an object of the present invention to provide a chuck that significantly reduces or overcomes the aforementioned disadvantages.

It is a further object of the present invention to provide a strong and rigid chuck having a large effective diameter and an overall size the same as of a conventional chuck.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a chuck (10), having an axis (A), comprising: a holder body (12) having a shank portion (14) for insertion into a spindle of a machine tool, a gripping flange (16) formed at one end of said shank portion and having a front face (46), and a chuck sleeve (18) that extends from said flange in a direction away from said shank portion and co-axially therewith, said chuck sleeve having a tapered outer circumferential surface (20) whose diameter (D) decreases from a rear end of said chuck sleeve adjacent said flange toward a forward end (22) of said tapered outer circumferential surface (20); a clamp sleeve (32) fitted onto the tapered outer circumferential surface (20) of said chuck sleeve (18) such that said clamp sleeve is rotatable and axially movable relative to said chuck sleeve, said clamp sleeve having a tapered inner circumferential surface (33) whose diameter decreases from a rear end of said clamp sleeve adjacent to said flange toward a forward end (34) of said clamp sleeve; and a plurality of needle rollers (30), each having an axis (B), disposed between the outer circumferential surface (20) of said chuck sleeve (18) and the inner circumferential surface (33) of said clamp sleeve (32), said needle rollers inclining in the circumferential direction at a predetennined angle (β) with respect to the axis (A) of the chuck, said clamp sleeve being rotated to cause said needle rollers to revolve spirally, about the axis (A) of the chuck, along the outer circumferential surface of said chuck sleeve, at a given pitch, while rotating about their own axes in order to decrease or restore the diameter of said chuck sleeve; characterized in that said clamp sleeve (32) is provided with a third thread (74) and said holder body (12) is provided with a first thread (50) that is located forward of said gripping flange, whereupon threadingly engaging said third thread with said first thread a rear axial abutnent surface (54) of said clamp sleeve (32) is forcibly pressed against a front axial abutment surface (46, 64, 82) of said holder body.

Preferably, said third thread and said first thread having a pitch the same as the given pitch.

Further preferably, each of said third thread and said first thread being a two-start-thread. Typically, said third thread is located at a rear portion of said clamp sleeve.

Further typically, said third thread being an internal thread and said first thread being an external thread.

Generally, a rear face (54) of the clamp sleeve (32), constituting a rear axial abutment surface, forcibly pressing against a front face (46) of the gripping flange (16), constituting a front axial abutment surface.

If desired, said rear axial abutment surface of said clamp sleeve and said front axial abutment surface of said holder body are ground.

According to a specific embodiment of the present invention, said first thread (50) is provided on a protrusion (58) extending forwardly from said front face (46) of said flange (16).

Preferably, said protrusion (58) is separated from said chuck sleeve (18) by a peripherally extending slot (59) having a rear surface (61), said rear surface (61) of said slot (59) being located forwardly with respect to said front face (46) of said flange (16). Further preferably, said rear surface (61) of said slot (59) is located forwardly with respect to said axial abutment surface (64) of said holder body (12).

Typically, the clamp sleeve (32) is further provided with a radially outwardly extending protrusion (70) in a rear portion of the clamp sleeve; said front axial abutment surface (64) of the gripping flange (16) is located forward than said front face (46) of the gripping flange, an axially extending second thread (66) extending between said front axial abutment surface (64) of the gripping flange and the front face (46) of the gripping flange; a securing ring (48) having a fourth thread (49) in a rear portion thereof and a radially inwardly extending protrusion (52) in a front portion thereof; wherein upon threadingly engaging said fourth thread with said second thread, said radially inwardly extending protrusion (52) of said securing ring securing said radially outwardly extending protrusion (70) of said clamp sleeve (32) thus preventing said clamp sleeve from being excessively un-clamped.

If desired, said securing ring (48) is further provided with a sealing ring (53) between an inner surface of said securing ring and an outer surface (35) of said clamp sleeve.

Preferably, the needle rollers (30) are retained within a roller retaining sleeve (24) that tapers forwardly at a same rate as the outer circumferential surface (20) of the chuck sleeve (18).

In accordance with the present invention there is further provided a chuck (10), having an axis (A), comprising: a holder body (12) having a shank portion (14) for insertion into a spindle of a machine tool, a gripping flange (16) formed at one end of said shank portion and having a front face (46), and a chuck sleeve (18) that extends from said flange in a direction away from said shank portion and co-axially therewith, said chuck sleeve having a tapered outer circumferential surface (20) whose diameter (D) decreases from a rear end of said chuck sleeve adjacent said flange toward a forward end (22) of said tapered outer circumferential surface (20); a clamp sleeve (32) fitted onto the tapered outer circumferential surface (20) of said chuck sleeve (18) such that said clamp sleeve is rotatable and axially movable relative to said chuck sleeve, said clamp sleeve having a tapered inner circumferential surface (33) whose diameter decreases from a rear end of said clamp sleeve adjacent to said flange toward a forward end (34) of said clamp sleeve; and a plurality of needle rollers (30), each having an axis (B), disposed between the outer circumferential surface (20) of said chuck sleeve (18) and the inner circumferential surface (33) of said clamp sleeve (32), said needle rollers inclining in the circumferential direction at a predetennined angle (β) with respect to the axis (A) of the chuck, said clamp sleeve being rotated to cause said needle rollers to revolve spirally, about the axis (A) of the chuck, along the outer circumferential surface of said chuck sleeve, at a given pitch, while rotating about their own axes in order to decrease or restore the diameter of said chuck sleeve; characterized in that said chuck sleeve (18) is provided with a fifth thread (85) near said forward end portion (22) of said outer circumferential surface (20) and a securing nut (84) is provided with a sixth thread (86), whereupon threadingly engaging said sixth thread (86) with said fifth thread (85) a rear surface of said securing nut (84) forcibly pressing said forward end (34) of said clamp sleeve thereby securing said clamp sleeve.

Preferably, upon mutual rotation of said securing nut (84) with said clamp sleeve (32), a rear axial abutment surface (54) of said clamp sleeve (32) is forcibly pressed against a front axial abutment surface (46, 64, 82) of said holder body.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: Fig. 1 is a cross-sectional side view of a prior art chuck;

Fig. 2 is a perspective view of a chuck according to the present invention; Fig. 3 is an exploded perspective view of the chuck of Fig. 2; Fig. 4 is an enlarged side view of the encircled portion in the roller retaining sleeve of Fig. 3; Fig. 5 is a cross-sectional view along line V-V in Fig. 4;

Fig. 6 is a cross-sectional side view of the chuck of Fig. 2;

Fig. 7 is an exploded cross-sectional partial side view of the chuck of Fig. 6;

Fig. 8 is a rear perspective view of the clamp sleeve of Fig. 3; Fig. 9 is a partial cross-sectional schematical side view of a second embodiment of a chuck according to the present invention;

Fig. 10 is a partial cross-sectional schematical side view of a third embodiment of a chuck according to the present invention;

Fig. 11 is a partial cross-sectional schematical side view of a fourth embodiment of a chuck according to the present invention;

Fig. 12 is a partial cross-sectional schematical side view of a fourth embodiment of a chuck according to the present invention; and

Fig. 13 is a partial cross-sectional schematical side view of a fourth embodiment of a chuck according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Attention is first drawn to Figs. 2 to 8 that describe a chuck according to the present invention. Since the chuck of the present invention is similar to the prior art chuck described with respect to Fig. 1, like parts will be designated with like numerals.

As shown, a tool chuck 10, having an axis A, has a holder body 12. The holder body 12 has a tapered shank portion 14, tapering toward a rear portion 15 of the chuck 10, to be inserted into a spindle of a machine tool (not shown), a gripping flange 16 formed at the larger-diameter end of the tapered shank portion 14, and a chuck sleeve 18 that extends forwardly toward a front portion 17 of the chuck 10 from a front face 46 of the flange 16 opposite the tapered shank portion 14 and co- axially therewith. The chuck sleeve 18 has a sleeve root 47 that is located forwardly than the front face 46 of the flange 16. The chuck sleeve 18 has a centrally located and axially extending cylindrical bore 19 for receiving therein a shank 40 of a tool 38. A tapered surface 20 on the outer circumference of the chuck sleeve 18 forms an acute angle Ot with the axis A such that the diameter of the surface 20 decreases toward the forward end portion 22 thereof. According to a specific embodiment of the present invention, the angle Ot is of 1°.

The body 12 of the chuck 10 is provided with a first thread 50 and a second thread 66 both of which are located forwardly than the front face 46 of the flange 16 and located between the front face 46 and the sleeve root 47. The first thread 50 is provided on the peripheral surface of a cylindrical protrusion 58. The first thread 50 has a given first pitch PI and is preferably a two-start-thread for a reason that will be described later. The protrusion 58 extends forwardly from a protrusion root 60, located forwardly from the front face 46, and terminates in an axially directed front surface 62. According to a preferred embodiment of the present invention, the protrusion 58 is radially outwardly located with respect to the chuck sleeve 18 and co-axial therewith. The protrusion 58 is separated from the chuck sleeve 18 by a peripherally extending slot 59 having a rear surface 61. The rear surface 61 of the slot 59 is located forwardly with respect to the front face 46 of the flange 16. The slot 59 provides the protrusion 58 with flexibility with respect to the chuck sleeve 18 for a purpose that will be described later.

A peripherally extending cylindrical step 68 is located radially outwardly with respect to the protrusion 58 and forwardly with respect to the front face 46 of the flange 16. A peripherally extending and axially directed surface 64 of the step 68 constitutes a front axial abutment surface of the holder body 12. Preferably, the axial abutment surface 64 is ground. The second thread 66 is provided on the peripheral surface of the step 68 and it extends axially forwardly from the front face 46 and co-axially with the axis A of the chuck 10. Preferably, the rear surface 61 of the slot 59 is located forwardly with respect to the axial abutment surface 64.

A roller retaining sleeve 24 is fitted co-axially onto the outer circumference of the chuck sleeve 18 with a clearance therebetween. The diameter of the roller retaining sleeve 24 decreases toward the forward end 26 thereof at the same rate as that of the tapered surface 20 of the chuck sleeve 18. The roller retaining sleeve 24 is held by a retainer ring 28 provided near the forward end portion 22 of the tapered surface 20 such that the roller retaining sleeve 24 is prevented from coming off the chuck sleeve 18. In the roller retaining sleeve 24, a plurality of needle rollers 30, each having an axis B, are disposed to form a plurality of rows. The needle rollers 30 are fitted into the roller retaining sleeve 24 in such a manner that the needle rollers incline in the circumferential direction at a predetermined angle β (see Fig. 4) with respect to the axis A of the chuck 10. Each of the needle rollers 30 has a first diameter Dl greater than the wall thickness L of the roller retaining sleeve 24, so that the portion of each needle 30 projecting inward from the inner circumferential surface 25 of the roller retaining sleeve 24 is in contact with the tapered surface 20 of the chuck sleeve 18, while the portion of each needle roller 30 projecting outward from the outer circumferential surface 27 of the roller retaining sleeve 24 is in contact with an inner circumferential surface 33 of a clamp sleeve 32.

The clamp sleeve 32 is adapted to decrease the diameter of the chuck sleeve 18 for tightly chucking a desired tool. The clamp sleeve 32 is fitted onto the outer circumference of the chuck sleeve 18 via the needle rollers 30 held by the roller retaining sleeve 24. The clamp sleeve 32 has a gripping portion 21 in the outer periphery 35 of the clamp sleeve for being manually rotated with respect to the axis A. On the gripping portion 21, a plurality of equally peripherally distributed recesses 23 are provided for receiving therein an external locking/unlocking key (not shown) of the clamp sleeve 32.

The outer periphery 35 of the clamp sleeve 32 terminates, in a rear portion thereof, in a peripherally and radially outwardly extending retaining protrusion 70. The retaining protrusion 70 has a third diameter D3 that is greater than a fourth diameter D4 of the outer periphery 35 adjacent the retaining protrusion 70. The third diameter D3 is also greater than any other diameter measured on the outer periphery 35 of the clamp sleeve 32.

The clamp sleeve 32 has a tapered inner circumferential surface 33 whose diameter decreases from the end facing the flange 16 toward the forward end portion 34 of the clamp sleeve 32. The diameter of the inner circumferential surface 33 decreases at the same rate as that of the tapered surface 20 of the chuck sleeve 18. A peripherally extending and axially directed rear surface 54 of the clamp sleeve 32 constitutes an axial abutment surface of the clamp sleeve. Preferably, the axial abutment surface 54 is ground.

Radially inwardly and axially forwardly of the axial abutment surface 54, a substantially cylindrical cut-out 72 terminates in the tapered inner circumferential surface 33. The cut-out 72 has a third thread 74 in the periphery thereof. The third thread 74 has a second pitch P2 that is equal to the first pitch PI of the first thread 50 and is a two-start-thread as the first thread 50. The third thread 74 extends axially forwardly from the axial abutment surface 54 and tenninates in a peripherally extending radial slot 75 having a peripheral wall 76 and a front wall 77. The peripheral wall 76 is located radially outwardly with respect to the third thread 74. Sealing rings 29 and 31 are attached to the chuck sleeve 18 near the forward end portion 22 of the tapered surface 20, rearward to the retainer ring 28, to obtain sealing between the tapered surface 20 of the chuck sleeve 18 and the tapered inner circumferential surface 33 of the clamp sleeve 32.

A sealing/retaining bushing 37, of an L-shaped cross-section, is inserted in the cut-out 72 and between the tapered surface 20 of the of the chuck sleeve 18 and the tapered inner circumferential surface 33 of the clamp sleeve 32 to provide a sealing function therebetween. A front end 39 of the bushing 37 abuts the rear end 41 of the roller retaining sleeve 24. The radially extending portion 43 of the bushing 37 is inserted within the slot 75, abutting the peripheral wall 76 and the front wall 77 of the slot 75, and thereby preventing the clamp sleeve 32 from coming off the chuck sleeve 18.

In order to chuck the shank 40 of the tool 38, a spring collet 42 is fitted onto the shank 40 of the tool 38, and the shank 40 of the tool, together with the spring collet 42, are inserted into the cylindrical bore 19 of the chuck sleeve 18. When the clamp sleeve 32 is rotated clockwise, as shown by the arrow F in Figs. 3 and 4, each needle roller 30 in contact with the tapered inner surface 33 of the clamp sleeve 32 revolves spirally about the axis A, along the outer surface of the chuck sleeve 18 while rotating about its own axis B. Thus, the roller retaining sleeve 24 moves toward the flange 16, while rotating, in accordance with the revolution of the needle rollers 30, and at the same time the clamp sleeve 32 also moves toward the flange 16, in a revolution having a third pitch P3. The movements of the roller retaining sleeve 24 and the clamp sleeve 32 toward the flange 16 reduce the clearance between the tapered inner surface 33 of the clamp sleeve 32 and the tapered outer surface 20 of the chuck sleeve 18, so that the clamp sleeve 32 strongly presses the tapered outer surface 20 of the chuck sleeve 18 via the needle rollers 30 in order to reduce the diameter of the chuck sleeve 18. As a result, the shank 40 of the tool 38 inserted into the cylindrical bore 19 of the chuck sleeve 18 is clamped and held by the chuck sleeve 18 via the spring collet 42. The first pitch PI of the first thread 50 and the second pitch P2 of the third thread 74 are, preferably, made equal to the third pitch P3 of the revolution of the clamp sleeve 32 with respect to the axis A of the chuck. In a specific embodiment of the present invention, the third pitch P3 equals to 3 mm per revolution. During the clockwise rotation of the clamp sleeve 32 in a clamping direction, since the first pitch PI and the second pitch P2 are equal to the third pitch P3, the clamp sleeve 32 encounters no resistance by the first thread 50. In a case where the first pitch PI and the second pitch P2 slightly differ from the third pitch P3, then, due to the flexibility of the protrusion 58, no undesired stresses are induced on the first thread 50, the chuck sleeve 18, the clamp sleeve 32, the roller retaining sleeve 24 and the needle rollers 30. When the axial abutment surface 54 of the clamp sleeve 32 abuts the front axial abutment surface 64 of the body 12, then, further tightening of the clamp sleeve 32 causes to forcibly pressing the axial abutment surface 54 against the front axial abutment surface 64, and, safety locking of the clamp sleeve 32 thus preventing self release of the clamp sleeve.

Since the first thread 50 and the third thread 74 are two-start-thread each, it is guaranteed that when coming into abutment between the axial abutment surface 54 and the front axial abutment surface 64, these surfaces remain parallel to each other without possibility of an un-desired tilting of the clamp sleeve 32 with respect to the axis A of the chuck 10.

The forcibly pressing of the axial abutment surface 54 against the front axial abutment surface 64 causes that the effective diameter of the chuck 10 is, practically, the third diameter D3 of the protrusion 70. Hence, the chuck 10 according to the present invention is much stronger and rigid than a conventional chuck while having an overall size the same as of a conventional chuck.

For securing and sealing of the clamp sleeve 32, a securing ring 48, having a fourth thread 49 in a rear internal circumference thereof, is threadingly engaged upon the second thread 66 of the body 12. The securing ring 48 is engaged until its axially directed rear surface 51 abuts the front face 46 of the flange 16. The securing ring 48 has a peripheral radially inwardly extending protrusion 52 in a front portion thereof. A sealing ring 53 is retained within the protrusion 52 for providing sealing against the outer periphery 35 of the clamp sleeve 32. An internal peripheral recess 55 is defined between the fourth thread 49 and the protrusion 52. The protrusion 52 has an internal fifth diameter D5 that is greater than the fourth diameter D4 of the outer periphery 35 of the clamp sleeve 32, but smaller than the third diameter D3 of the retaining protrusion 70 of the clamp sleeve 32. Therefore, when the clamp sleeve 32 is rotated counterclockwise in an un-clamping direction, the retaining protrusion 70 can freely move within the recess 55 until it reaches the protrusion 52, so that the clamping sleeve 32 is secured against over un-clamping.

When the clamp sleeve 32 in a clamped state is rotated counterclockwise, it forces, by means of the sealing/retaining bushing 37, the roller retaining sleeve 24 to rotate counterclockwise and move forwardly toward the forward end of the chuck sleeve 18. The forward movement of the roller retaining sleeve 24 together with the forward movement of the needle rollers 30 retained therein release the pressure applied on the chuck sleeve 18 so that the chuck sleeve restores its original diameter. By that, the clamping force applied to the tool 38 is released, and the tool 38 can be removed from the chuck sleeve 42.

Figs. 9 to 13 show, respectively, second to sixth embodiments of a chuck according to the present invention, showing schematically the relative disposition between the flange 16 and the clamp sleeve 32. In these drawings, the clamp sleeve 32 contracts the chuck sleeve 18 through the rollers 30 in the same manner as in Figs. 1 to 8.

In Fig. 9, the clamp sleeve 32 abuts a front face 46 of the flange 16. The first thread 50 is provided on the chuck sleeve 18 and is located between the front face 46 of the flange 16 and the tapered outer circumferential surface 20 of the chuck sleeve 18.

In Fig. 10, the thread engagement between the clamp sleeve 32 and the body 12 is provided near the forward end portion 22 of the tapered outer circumferential surface 20.

In Fig. 11, the clamp sleeve 32 is not provided with a third thread. Instead, a securing nut 84 is threadingly engaged on a fifth thread 85 provided near the forward end portion 22 of the tapered outer circumferential surface 20. By means of the securing nut 84, the axial abutment surface 54 of the clamp sleeve 32 is forcibly pressed against the front face 46 of the flange 16, and the clamp sleeve 32 is secured against undesired loosening.

In Fig. 12, the clamp sleeve 32 abuts a front abutting surface 80 of the flange

16. However, in this embodiment, the first thread 50 is provided on a protrusion 81 extending forwardly from the front face 46 of the flange 16 and is an internal thread, in contrary to it being external thread in the previous embodiments.

Accordingly, the third thread 74 of the clamp sleeve 32 is an external thread.

Fig. 13 is similar to Fig. 12, however, in this embodiment, the axial abutment surface 54 of the clamp sleeve 32 is located forwardly than the third thread 74, in contrary to it being rearwardly to the third thread in the previous embodiments. Accordingly, the axial abutment surface of the body 12 is located on the front end 82 of a protrusion 83 that protrudes forwardly from the front surface 46 of the flange 16.

Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims

CLAIMS:

1. A chuck (10), having an axis (A), comprising: a holder body (12) having a shank portion (14) for insertion into a spindle of a machine tool, a gripping flange (16) formed at one end of said shank portion and having a front face (46), and a chuck sleeve (18) that extends from said flange in a direction away from said shank portion and co-axially therewith, said chuck sleeve having a tapered outer circumferential surface (20) whose diameter (D) decreases from a rear end of said chuck sleeve adjacent said flange toward a forward end (22) of said tapered outer circumferential surface (20); a clamp sleeve (32) fitted onto the tapered outer circumferential surface (20) of said chuck sleeve (18) such that said clamp sleeve is rotatable and axially movable relative to said chuck sleeve, said clamp sleeve having a tapered inner circumferential surface (33) whose diameter decreases from a rear end of said clamp sleeve adjacent to said flange toward a forward end (34) of said clamp sleeve; and a plurality of needle rollers (30), each having an axis (B), disposed between the outer circumferential surface (20) of said chuck sleeve (18) and the inner circumferential surface (33) of said clamp sleeve (32), said needle rollers inclining in the circumferential direction at a predetermined angle (β) with respect to the axis (A) of the chuck, said clamp sleeve being rotated to cause said needle rollers to revolve spirally, about the axis (A) of the chuck, along the outer circumferential surface of said chuck sleeve, at a given pitch, while rotating about their own axes in order to decrease or restore the diameter of said chuck sleeve; characterized in that said clamp sleeve (32) is provided with a third thread (74) and said holder body (12) is provided with a first thread (50) that is located forward of said gripping flange, whereupon threadingly engaging said third thread with said first thread a rear axial abutment surface (54) of said clamp sleeve (32) is forcibly pressed against a front axial abutment surface (46, 64, 82) of said holder body.

2. A chuck according to claim 1, wherein said third thread and said first thread having a pitch the same as the given pitch.

3. A chuck according to claim 1, wherein each of said third thread and said first thread being a two-start-thread.

4. A chuck according to claim 1, wherein said third thread is located at a rear portion of said clamp sleeve.

5. A chuck according to claim 1, wherein said third thread being an internal thread and said first thread being an external thread.

6. A chuck according to claim 1, wherein a rear face (54) of the clamp sleeve (32), constituting a rear axial abutment surface, forcibly pressing against a front face (46) of the gripping flange (16), constituting a front axial abutment surface.

7. A chuck according to claim 1, wherein said rear axial abutment surface of said clamp sleeve and said front axial abutment surface of said holder body are ground.

8. A chuck according to claim 1, wherein said first thread (50) is provided on a protrusion (58) extending forwardly from said front face (46) of said flange (16).

9. A chuck according to claim 8, wherein said protrusion (58) is separated from said chuck sleeve (18) by a peripherally extending slot (59) having a rear surface

(61), said rear surface (61) of said slot (59) being located forwardly with respect to said front face (46) of said flange (16).

10. A chuck according to claim 9, wherein said rear surface (61) of said slot

(59) is located forwardly with respect to said axial abutment surface (64) of said holder body (12).

11. A chuck according to claim 1, wherein the clamp sleeve (32) is further provided with a radially outwardly extending protrusion (70) in a rear portion of the clamp sleeve; said front axial abutment surface (64) of the gripping flange (16) is located forward than said front face (46) of the gripping flange, an axially extending second thread (66) extending between said front axial abutment surface (64) of the gripping flange and the front face (46) of the gripping flange; a securing ring (48) having a fourth thread (49) in a rear portion thereof and a radially inwardly extending protrusion (52) in a front portion thereof; wherein upon threadingly engaging said fourth thread with said second thread, said radially inwardly extending protrusion (52) of said securing rmg securing said radially outwardly extending protrusion (70) of said clamp sleeve (32) thus preventing said clamp sleeve from being excessively un-clamped.

12. A chuck according to claim 9, wherein said securing ring (48) is further provided with a sealing ring (53) between an inner surface of said securing ring and an outer surface (35) of said clamp sleeve.

13. A chuck according to claim 1, wherein the needle rollers (30) are retained within a roller retaining sleeve (24) that tapers forwardly at a same rate as the outer circumferential surface (20) of the chuck sleeve (18).

14. A chuck (10), having an axis (A), comprising: a holder body (12) having a shank portion (14) for insertion into a spindle of a machine tool, a gripping flange (16) formed at one end of said shank portion and having a front face (46), and a chuck sleeve (18) that extends from said flange in a direction away from said shank portion and co-axially therewith, said chuck sleeve having a tapered outer circumferential surface (20) whose diameter (D) decreases from a rear end of said chuck sleeve adjacent said flange toward a forward end (22) of said tapered outer circumferential surface (20); a clamp sleeve (32) fitted onto the tapered outer circumferential surface (20) of said chuck sleeve (18) such that said clamp sleeve is rotatable and axially movable relative to said chuck sleeve, said clamp sleeve having a tapered inner circumferential surface (33) whose diameter decreases from a rear end of said clamp sleeve adjacent to said flange toward a forward end (34) of said clamp sleeve; and a plurality of needle rollers (30), each having an axis (B), disposed between the outer circumferential surface (20) of said chuck sleeve (18) and the inner circumferential surface (33) of said clamp sleeve (32), said needle rollers inclining in the circumferential direction at a predetermined angle (β) with respect to the axis (A) of the chuck, said clamp sleeve being rotated to cause said needle rollers to revolve spirally, about the axis (A) of the chuck, along the outer circumferential surface of said chuck sleeve, at a given pitch, while rotating about their own axes in order to decrease or restore the diameter of said chuck sleeve; characterized in that said chuck sleeve (18) is provided with a fifth thread (85) near said forward end portion (22) of said outer circumferential surface (20) and a securing nut (84) is provided with a sixth thread (86), whereupon threadingly engaging said sixth thread (86) with said fifth thread (85) a rear surface of said securing nut (84) forcibly pressing said forward end (34) of said clamp sleeve thereby securing said clamp sleeve.

15. A chuck according to claim 12, wherein upon mutual rotation of said securing nut (84) with said clamp sleeve (32), a rear axial abutment surface (54) of said clamp sleeve (32) is forcibly pressed against a front axial abutment surface (46, 64, 82) of said holder body.