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Title:
STRUCTURE OF JAW FOR A SELF-CENTERING CHUCK AND METHOD THEREOF
Document Type and Number:
WIPO Patent Application WO/2016/067216
Kind Code:
A1
Abstract:
A structure of jaw (100) for a self-centering chuck (200) of machines tools having a rotation axis x and a radius r and comprising at least one slide (210) that is arranged to move in a radial direction on the chuck (200), passing between a close position to the rotation axis x and a spaced position from the rotation axis x. The structure of jaw (100) comprises a block (110) integrally connected to the slide (210) at a fastening face (111), in such a way that the block (110) is moved integrally to the slide in order to block a workpiece (300). The structure of jaw (100) also comprises a tightening portion (120) engaged in a removable way to the block (110) at an engagement housing (112) of the block (110), said tightening portion (120) having a tightening face (121) facing towards the center 0 of the chuck (200) and having a distance d from the rotation axis x. The tightening portion (120) protrudes cantilever by the block (110) opposite to the fastening face (111). In particular, when the slide (210) is in the spaced position it is d ≥ r, in such a way that the structure of jaw (100) can block a workpiece (300) having a transversal width at least equal to r.

Inventors:
PISANI PIETRO (IT)
Application Number:
PCT/IB2015/058311
Publication Date:
May 06, 2016
Filing Date:
October 28, 2015
Export Citation:
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Assignee:
RACCORDERIA PIACENTINA DI PISANI PIETRO & C S N C (IT)
International Classes:
B23B31/16
Foreign References:
DE2848342A11980-05-14
US4960285A1990-10-02
US5524910A1996-06-11
US6478311B12002-11-12
JPH0355107U1991-05-28
US3679221A1972-07-25
US4706973A1987-11-17
US4960285A1990-10-02
Attorney, Agent or Firm:
CELESTINO, Marco (Viale Giovanni Pisano 31, Pisa, IT)
Download PDF:
Claims:
CLAIMS

1. A structure of aw (100) for a self-centering chuck (200) of machines tools, said chuck (200) having a rotation axis x and a radius r and comprising at least one slide (210) that is arranged to move in a radial direction on said chuck (200), passing between a close position to said rotation axis x and a spaced position from said rotation axis x ,

said structure of aw (100) comprising:

- a block (110) integrally connected to said slide (210) at a fastening face (111), in such a way that said block (110) is moved integrally to said slide in order to block a workpiece (300);

- a tightening portion (120) engaged in a removable way to said block (110) at an engagement housing (112) of said block (110) , said tightening portion (120) having a tightening face (121) facing towards the center 0 of said chuck (200) and having a distance d from said rotation axis x ;

characterized in that said tightening portion (120) protrudes cantilever from said block (110) opposite to said fastening face (111),

and in that when said slide (210) is in said spaced position there is d > r , in such a way that said structure of jaw (100) can block a workpiece (300) having transversal width equal to 2r.

2. The structure of aw (100), according to claim 1, wherein said engagement housing (112) is a housing formed on a front face (113) opposite to said fastening face (111) and said tightening portion (120) has an engagement end (122) with a shape complementary to said engagement housing (112) .

3. The structure of aw (100), according to claim 2, wherein said engagement end (122) has a parallelepiped shape and said engagement housing (112) is a prismatic groove arranged to receive said engagement end (122) .

4. The structure of jaw (100), according to claim 2, wherein said engagement end (122) has a cylindrical shape and said engagement housing (112) is a circular- shaped hole configured to receive said engagement end (122) .

5. The structure of jaw (100), according to claim 1, wherein said tightening portion (120) is made of a soft metal material.

6. The structure of jaw (100), according to claim 1, said tightening portion (120) is made of a material selected from the group consisting of: mild steel, brass, aluminum.

7. The structure of jaw (100), according to claim 1, wherein said tightening face (121) comprises at least a grip portion (121') previously machined by chip removal for adapting to the shape of a workpiece.

8. The structure of aw (100), according to claim 2, wherein said tightening portion (120) is blocked in said engagement housing (112) by means of a screw coupling.

9. The structure of aw (100), according to claim 8, wherein said screw coupling provides radial screws and axial screws.

10. A method for making a structure of jaw (100) said method comprising the steps of:

- predisposition of a metal block (110);

- creation on said metal block (110) of an engagement housing (112) ;

- predisposition of a tightening portion (120);

- removable connection of said tightening portion (120) on said metal block (110) at said engagement housing (112) .

Description:
TITLE

STRUCTURE OF JAW FOR A SELF-CENTERING CHUCK AND METHOD

THEREOF

DESCRIPTION

Field of the invention

The present invention relates to the field of machine tools .

In particular, the invention relates to a clamp for self-centering chucks for precision machining on the lathe.

Description of the prior art

There are self-centering chucks for lathe having clamps or jaws. The clamps are mounted on the slides of the chuck, normally three, which move thanks to a tightening mechanism that causes a synchronous radial movement towards the axis of the lathe or away from the axis of the lathe.

There are clamps so-called "hard", normally made in steps, to adapt to various classes of diameters of the workpieces . They are indeed of hard material in order to not deform due to the strong tightening stresses on the workpiece. Typically they are indented and can leave marking on the workpiece. They are not the subject of the present patent.

So called "soft clamps" are made instead of a soft material and are made with a curvature equal to the workpiece, in order to grip the workpiece with more precision and higher contact surface and not leave markings on the workpiece. Soft clamps are a block substantially parallelepiped, with a face of prismatic coupling that is used for coupling to the respective slide.

They are machined on a face next to the prismatic face, that is the one that faces radially on the workpiece.

Changing the machining process, the soft clamps previously machined become unusable in most cases. In some cases they can be reprocessed for a limited number of times, then they have to be thrown away.

Every time they are thrown away, much material is thrown away too, about the 80-90%.

Realizing the clamps all of soft steel also the prismatic coupling parts may wear more quickly. For this reason there are soft clamps made by a hard material with non-removable inserts made in soft material, i.e. brass. They are very expensive and in any case they do not solve the other problems .

A possible solution is presented by US4960285, which describes a structure of jaw composed by a block integrally connected to the slide and by a tightening portion of the workpiece, of limited size, which can be withdrawn and replaced independently from the rest of the clamp. Such portion can be made of soft steel, in order to adapt to the workpiece. When the portion becomes unusable, it is replaced without the need to replace the entire clamp. Such a solution, however, has the drawback of allowing the machining of only workpieces having a transversal dimension much lower than the nominal diameter of the chuck. This is because the tightening portion, as it is configured in the solution provided by US4960285, is necessarily connected to the block close to the center of the chuck. Therefore, in order to receive a workpiece having a transversal width greater than or equal to the nominal diameter of the chuck, the slide should slide outwards up to leave from its own guide, and this is obviously not possible.

Furthermore, the tightening portion has a vertical size substantially comparable to the height of the rest of the block, not allowing the possibility to operate workpieces having a longitudinal dimension bigger than the other ones, such as ducts or the like, since they would be subject to bending moments too high.

The structure of aw presented in US4960285, therefore, is not very much adaptable to the machining of workpieces having transversal or longitudinal dimensions very different to each other. This involves the need to use chucks of different diameter according to the size of the workpiece, with evident economic expenditure.

Summary of the invention

It is therefore a feature of the present invention to provide a structure of jaw for self-centering chucks that allows a steady machining of workpieces having sizes very different from each other, without changing the size of the chuck itself.

It is also a feature of the present invention to provide a structure of jaw for self-centering chucks that provides the presence of clamps that do not cause on the workpiece permanent deformation owing to the tightening.

It is still a feature of the present invention to provide such a structure of jaw that provides the presence of clamps that do not have to be entirely replaced when they wear out.

It is then a feature of the present invention to provide such a structure of jaw that provides a quick and easy interchangeability of the type of clamp suitable for the specific machining.

It is a further feature of the present invention to provide such a structure of jaw that provides the presence of clamps that inhibit the bending a workpiece if it has an elongated shape and is connected cantilever to the chuck.

It is, furthermore, a feature of the present invention to provide a method for making the above described structure of j aw .

These and other objects are achieved by a structure of jaw for a self-centering chuck machines tools, said chuck having a rotation axis x and a radius r and comprising at least one slide that is arranged to move in a radial direction on the chuck, running between a close position to the rotation axis x and a spaced position from the rotation axis x ,

said structure of aw comprising:

- a block integrally connected to the slide at a fastening face, in such a way that the block is moved integrally to the slide in order to block a workpiece;

- a tightening portion engaged in a removable way to the block at an engagement housing of the block, said tightening portion having a tightening face oriented towards the center 0 of the chuck and having a distance d by the rotation axis x ,

whose main feature is that the tightening portion protrudes cantilever from the block opposite to the fastening face,

and that when the slide is in the spaced position it is d≥r , in such a way that the structure of jaw can block a workpiece having transversal width equal to 2r.

The structure of jaw according to the present invention allows therefore, on the contrary of the prior art, to adapt the chuck to workpieces having transversal dimensions very different from each other, and especially it makes it possible to operate workpieces with a transversal dimension substantially equal to the nominal diameter of the chuck. In particular, the engagement housing is a housing formed on a front face opposite to the fastening face and the tightening portion has an engagement end with a shape complementary to the engagement housing.

Advantageously, the engagement end has a parallelepiped shape and the engagement housing is a prismatic groove arranged to receive the engagement end.

Alternatively, the engagement end has a cylindrical shape and the engagement housing is a hole with circular cross section which is configured to receive the engagement end.

Advantageously, the tightening portion is made of a soft metal material.

In particular, the tightening portion is made of a material selected from the group consisting of: mild steel, brass, aluminum.

In particular, the tightening face comprises at least a grip portion previously machined by chip removal for adapting to the shape of a workpiece.

Advantageously, the tightening portion is blocked in the engagement housing by means of a screw coupling.

In particular, the screw coupling provides radial screws and axial screws.

According to another aspect of the invention a method for making structure of aw comprises the steps of:

- predisposition of a metal block; - creation on the metal block of an engagement housing;

- predisposition of a tightening portion;

- removable connection of the tightening portion on the metal block at the engagement housing engagement.

Brief description of the drawings

Further characteristic and/or advantages of the present invention are more bright with the following description of an exemplary embodiment thereof, exemplifying but not limitative, with reference to the attached drawings in which:

- Fig. 1 shows a structure of aw of the prior art mounted on a self-centering chuck;

- Fig. 2 shows in lateral view a first exemplary embodiment of the block and of the tightening portion of the structure of aw according to the present invention;

- Fig. 3 shows in an exploded view the exemplary embodiment of the block and of the tightening portion Fig. 2;

- Fig. 4 shows in frontal view the exemplary embodiment of the structure of jaw of Fig. 2;

- Fig. 5 shows in an exploded view a second exemplary embodiment of the block and of the tightening portion;

- Fig. 6 shows in frontal view the exemplary embodiment of the structure of jaw of Fig. 5. Description of a preferred exemplary embodiment

In Fig. 1 is shown a structure of jaw of the prior art for a self-centering chuck 200, where the chuck 200 comprises three slides 210 radially sliding on the chuck 200 and that can be blocked in a predetermined radial position.

The structure of jaw 100 comprises a block 110 for each slide 210, and each block 110 comprises a respective fastening face 111 for fastening by means of bolts 115 to a respective slide 210, in such a way that the blocks 110 can be moved integrally to the respective slides for blocking a workpiece 300 to be machined.

In particular, the chuck 200 has a rotation axis x and a radius r and the slides 210 move on the chuck 200 along a radial direction, passing between a close position to the rotation axis x and a spaced position from the rotation axis x .

With reference to Fig. 2, the structure of jaw 100, according to the present invention, also comprises a tightening portion 120 and each block 110 comprises a engagement housing 112 at which is engageable in a removable way the tightening portion 120, such that the latter protrudes cantilever from the block 110 opposite to the fastening face 111.

In particular, with reference even to Figs. 2 and 3, in a first exemplary embodiment each tightening portion 120 has a substantially parallelepiped shape and the engagement housing 112 on the block 110 consists of a prismatic groove made on a front face 113, opposite to the fastening face 111, said groove arranged to receive a parallelepiped engagement end 122 of the tightening portion 120 that engages in a removable way by means of screws 125 and 126.

In particular, with reference to Fig. 4, the tightening portion 120 has a tightening face 121 oriented towards the center 0 of the chuck 200 and located at a distance d by the rotation axis x. In Fig. 4, the slide 210 is in spaced position and d= r . This way, the structure of aw 100 can block a workpiece 300 having transversal width equal to 2r.

Furthermore, in an exemplary embodiment of Fig. 4, the tightening face 121 comprises a grip portion 121' with a circular shape that allows the tightening of a cylindrical workpiece 300.

With reference to Figs. 5 and 6, in a second exemplary embodiment, the engagement housing 112 on the block 110 consists of a circular hole made on the front face 113 and arranged to receive a cylindrical engagement end 122 of the tightening portion 120.

The foregoing description some exemplary specific embodiments will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt in various applications the specific exemplary embodiments without further research and without parting from the invention, and, accordingly, it is meant that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realize the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.