EP3638451A1

EP3638451A1 - Clamping element for positioning and/or fixing a workpiece or tool

Info

Publication number: EP3638451A1
Application number: EP19708104.5A
Authority: EP
Inventors: Horst Knäbel
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-07
Filing date: 2019-03-01
Publication date: 2020-04-22
Also published as: WO2019170556A1; EP3536448A1

Abstract

In order to position and/or fix a workpiece (3) or tool, a clamping element (1) comprising a plurality of supporting webs (4) and a plurality of elastic intermediate members (5) is proposed, wherein the clamping element (1) can be opened out or pushed together by stretching or compressing the elastic intermediate members (5). The supporting webs (4) and the elastic intermediate members (5) are connected integrally and endlessly together. The clamping element (1) has been produced by the 3D method.

Description

Clamping element for positioning and / or fixing a workpiece or tool

The present invention relates to a clamping element for positioning and / or fixing a workpiece or tool, comprising a plurality of support webs and a plurality of elastic intermediate members, wherein the clamping element can expand or compress by stretching or compression of the elastic intermediate members. Particularly in the case of mechanical finishing and final inspection of workpieces which must be picked up and clamped on one of their reference surfaces, it is important to position, fix and tension them very precisely and exactly reproducibly so that they can be dimensionally, formally and be able to manufacture or measure correctly. This requires clamping devices that are characterized by their high form and positional accuracy as well as their high dimensional stability.

The same is true when clamping tools. Only with a precisely positioned tool can the expected dimensional stability of a workpiece to be machined be achieved. In addition, a runout deviation leads to uneven stress on the tool and thus to a reduction in tool life.

The publication DE 482 024 C discloses a tensioning element which is formed by a conical sleeve with longitudinal slots. Through the longitudinal slots, the sleeve is divided into contiguous segments. The longitudinal slots extend in the longitudinal direction over part of the radial dialen extension of the sleeve and are directed radially inward or radially outward. The segments have the same outer and inner contour as the sleeve. At the beginning of a clamping process, the segments are applied to the workpiece or tool. During clamping, the segments are displaced against each other and deformed in the transitional area formed by the adjacent slots. The radial offset as well as this deformation have a negative effect on the adjacent surfaces and on the concentricity and promote wear. A comparable problem also exists in a clamping sleeve known from EP 2 813 306 A1, in which a plurality of segments distributed regularly over the circumference of the clamping sleeve are provided. The segments are interconnected. The clamping sleeve has a plurality of grooves. First grooves go from the outer surface of the sleeve inside. Furthermore, second outgoing from an inner circumferential surfaces grooves are provided. Between the first and the second grooves material bridges remain.

There are also known clamping elements in which the elastic intermediate members are formed as vulcanized onto the support webs intermediate layers. The number of support webs and the intermediate links is usually limited to 3 to 6 per clamping element for manufacturing reasons. Rubber or rubber-elastic plastics are generally used as the material for these intermediate layers.

It is considered disadvantageous that these intermediate layers as well as their connection with the support bars, which mostly consist of tool steel, do not permanently against numerous liquids and are useful only in a limited temperature range, prone to swelling, and subject to a natural aging process, and that the greater thermal expansion of the intermediate layers relative to the metallic support webs leads to the increase of uncontrollable stresses in the vulcanization zones.

When using such, for example, concentric clamping element, which is used as a sleeve-shaped body between a tapered receiving mandrel or a cone-shaped receiving sleeve and a workpiece or tool designed as a support element, the concentricity achievable thereby with a limited clamping range is at best 5 to 10 pm. When using the full clamping range, the achievable concentricity decreases progressively as a result of the pressure surface displacement described below.

Furthermore, commercially available clamping elements in the form of concentric sleeves are known, one shell surface of which is cylindrical and the other cone-shaped. These one-piece clamping elements, usually made of tool steel, have no elastic intermediate members over which the clamping element would expand or collapse. These clamping elements have only in alternation of two end faces outgoing slots, which may, however, extend only so far that the sleeve segments formed by the slots, a kind of support webs, at least on one end still remain connected to each other via so-called bridge webs. The disadvantage of such tensioning elements is that the sleeve segments, when fixing or tensioning a workpiece or a tool, due to the flexural rigidity of the bridge. Depending on the rigidity and hardness of the interacting parts, the webs are forced out of the parallel position to their reference axis and deformed in an uncontrolled manner and radially bent over their length. Since the pressure surface of the sleeve segments is displaced from the center to one of the edges, which is much less precise, the concentricity also deteriorates uncontrollably to the same extent.

Here, too, the attainable concentricity decreases progressively when the full clamping range is used.

The present invention is therefore based on the object to provide a clamping element that offers significant advantages in terms of dimensional stability and concentricity accuracy as well as the resistance to media, temperature and aging compared to such previously known clamping elements.

To achieve the object, it is proposed according to the invention in a tensioning element according to the type described at the outset that the tensioning element is produced in a 3-D process. The 3-D process is preferably a laser fusion process or another metallic printing process. The elastic intermediate members of the inventive clamping element have a thickness between 0.2 mm and 0.8 mm. The tensioning element is also distinguished by the fact that the intermediate elements are arranged at a distance from the outer lateral surface as well as from the inner lateral surface of the support webs (4) and connected integrally and endlessly to the support webs. When such a clamping element according to the invention with a conical lateral surface for clamping a workpiece or tool is moved axially towards a conically lateral surface of a supporting element, the supporting webs of the clamping element slide on the surface of the supporting element until its opposite, for example cylindrical, shell element surface comes to rest against the workpiece or to the tool. Since the elastic intermediate links are designed in such a way that they are stretched or compressed uniformly, the surfaces of the support webs originally running parallel to the reference axis and a reference system continue to be aligned in parallel and the support webs themselves remain free of any transverse forces. The reference system is a reference system according to ISO 5459: 1981.

It is also possible to design the inner and outer lateral surface of a clamping element according to the invention cylindrically and to provide it on both sides with conical centering bevels. With such an arbitrarily long clamping element, for example, workpieces very easily and very accurately record, clamp, edit and / or measure between the tips of a turning or grinding machine and a corresponding measuring device, even if the workpieces, as usual, not exactly concentric trained Chamfers. Moreover, it is also possible to perform these clamping elements as step elements, similar to a step mandrel, as well as to reduce the diameter of the clamping element on both sides by a corresponding amount in order to machine the workpiece on all sides to be able to measure. Another advantage of the invention is to produce very narrow clamping elements and use for such tasks too can be eroded as well as existing clamping elements subsequently to the desired length. In this way, it is possible, for example, to produce clamping elements with a diameter of 16-60 mm and a width of 3 to 12 mm.

If the clamping process is carried out by means of tapered conical surfaces, the workpiece or tool is clamped non-positively in the case of clamping systems, but only with limited form fit. This is because, during the tensioning process, the radii of the touching conical surfaces change. If the support webs of the clamping element are moved toward the outer surface of a growing support element, the adhesion is displaced from the center to the edge zones of the support webs. In contrast, the adhesion is again shifted from the edge zones of the support webs toward the center when the support webs meet the mantle surface of a tapered support element.

In order to minimize the influence of this unalterable relationship, it is proposed according to the invention to minimize the carrier web width striking a conical support surface and to increase the number of support webs of a clamping element as far as possible or to make the radii of the meeting parts such that the outer one is larger than the inner one.

As tests and the following calculation show, it is possible in a tensioning element according to the invention, the resulting radial gap between the colliding surfaces of the support webs and the To reduce support element and thus to keep the runout below 1 gm.

To determine the gap A, the following relationship can be used

A = r - R + (R ^A 2 - b ^A 2) ^A 0,5 - (r ^A 2 - b ^A 2) ^A 0,5 if for r the smaller radius, for R the larger radius and for b the hal - BE web width is used.

This is useful and also practicable, since it depends less on large clamping forces than on a high concentricity and good reproducibility in the clamping elements according to the invention, which are particularly intended for mechanical finishing and production control.

But it is also possible to provide clamping elements with much wider webs, if for the support member accordingly has narrow protruding formed support surfaces. The outline edges of such narrow support surfaces can be produced easily and very precisely.

Such a clamping element according to the invention can be produced very simply and inexpensively as a blank by laser melting, which after hardening or tempering preferably only has to be ground in a contact stress on its contact surfaces, ie inside and outside and one of its end faces to the highest possible, preferably Almost 100 percent coaxiality of the inner and outer contours of such a clamping element to achieve. The material used to date was tool steel 1.2709, which can be easily heat-treated and coated. In the course of this rapidly evolving technology, it can be assumed that in the foreseeable future, other high quality and even more suitable materials will be available for the production of such clamping elements. However, it is also possible to equip such a clamping element blank with, for example, hard metal webs and then to finish it as described above.

Experiments have shown that it is still possible to go down to 0.4 mm with the wall thickness of the elastic intermediate links and thus clamping ranges, with a corresponding clamping diameter and the corresponding number of supporting webs and elastic intermediate links, of 0.1 to reach 0.5 mm.

Further preferred embodiments of the invention are disclosed in claims 2 to 10.

In particular, it is proposed that the elastic intermediate members are formed so that the support webs are connected to each other in the outer and inner regions. Preferably, the clamping element is formed so that the outer and / or the inner circumferential surface is provided with a thread. In this Form of the clamping element, this can be part of a special clamping device.

For the formation of the clamping element is proposed that the inner and outer lateral surface and one of its two end faces are mechanically finished in one and the same setup.

In order to improve the functionality of the clamping element, the clamping element can be sealed over its flat end faces.

A clamping element according to the invention is preferably produced in the 3D printing process, preferably in the laser melting process.

The invention and further advantages thereof will be explained in more detail below with reference to the embodiments illustrated in the drawings. Show

1 is an end view of a clamping element on a conical support member for clamping a formed as a gear wheel workpiece,

2 shows an enlarged section of the region A of FIG. 1, FIG. 3 shows a plan view of a further, second embodiment of a tensioning element,

4 shows a sectional view along the line a-a through the clamping element according to FIG. 3, FIG.

5 shows a sectional view along the line bb through the clamping element according to FIG. 3, FIG. 6 shows a sectional view along the line cc through the clamping element according to FIG. 5, FIG.

7 is a perspective view of the clamping element of

3,

8 is a plan view of a further, third embodiment of a clamping element,

9 is a sectional view along the line d-d through the clamping element of FIG. 8,

10 is a sectional view along the line e-e through the clamping element of FIG. 8,

11 shows a sectional view along the line g-g through the tensioning element according to FIG. 10, FIG.

Fig. 12 is a perspective view of the clamping element of

8,

13 shows an end view of a clamping element for receiving between the tips of a machining or measuring machine with a workpiece designed as a bevel gear,

14 is a sectional view along the line h-h through the clamping element of FIG. 13,

15 is a sectional view along the line j-j through the clamping element of FIG. 13,

Fig. 16 is a perspective view of the clamping element of

Fig. 13.

FIGS. 17 and 18 are schematic diagrams for explaining the form-locking deviation when cone-shaped surfaces meet. surfaces with different radii and the resulting gap A,

19 to 22 differently shaped, meander-shaped intermediate members as connection of adjacent support webs,

Fig. 23 is a clamping element with elastic intermediate members, the

Connect support bars inside and outside,

24 is a perspective view of a clamping element with an external thread,

Fig. 25 is a perspective view of a clamping element with an internal thread

26 is a plan view of a clamping element with inserts,

27, the clamping element of FIG. 26 in section,

28 is a plan view of another clamping element with Ein 1a- gen,

FIG. 29 shows the clamping element according to FIG. 28 in section, FIG.

FIG. 30 shows a blank, shown in longitudinal section, for the embodiment of the tensioning element according to FIGS. 28 and

Fig. 31, the blank of FIG. 30 in section transverse to the longitudinal axis. The clamping element 1a shown in Figures 1 and 2, which is located between a conical support member 2 and a gear formed as a workpiece 3, has as an example at a clamping diameter of 40 mm over ten support webs 4 and ten elastic intermediate members 5, in this case are evenly distributed over the circumference of the clamping element la. In a further preferred embodiment not shown in the figures, however, it is also possible to tangentially connect a plurality of support webs to one another via flexurally elastic bridges and to arrange the elastic intermediate members in any order between them. In that regard, in each case an elastic intermediate element can be arranged between two or more support webs which are connected to one another.

The elastic intermediate links 5 are preferably meander-shaped connections between two adjacent support webs. They can be variously profiled, as illustrated for example in FIGS. 1, 2, 3, 7, 7, 10, 12, 19, 20 to 29 as being of the same kind throughout, or as shown in FIG. 22, as mirror images arranged one behind the other and arranged one behind the other designed structures to be executed.

The support webs 4 connected to the elastic intermediate members 5 have a relatively wide back 4 a to the workpiece 3, while the webs 4 b of the support webs 4 resting against the support element 2 are made deliberately narrow. As already mentioned, the width of the webs 4b influence the achievable concentricity. The ridges 4 a form part of an outer jacket surface 9. The ridges 4 b form part of an inner jacket surface 10.

When tightening the clamping element la and / or the support member 2 are moved axially as far as each other until the support webs 4 with your back 4a, the workpiece 3 and 4b with their webs connect the support member 2 non-positively. As shown in FIGS. 1 and 2, it is possible to cover the elastic intermediate links 5 via so-called segment strips 6 to the outside. These segment strips 6 are preferably made of thin spring band steel and pushed over the entire length of the clamping element la in the recesses provided 4c of the support webs. The segment strips 6 are then applied to the outer shoulders of the recesses 4c of the support webs 4 and are based on the central curvature 5a of the elastic intermediate members 5 from. However, it is also possible to use specially produced plastic strips, and / or to fill the cavities, which are at least partially formed by the meander-shaped structures, with a filling material. The tensioning element 1b of FIGS. 3 to 6 essentially corresponds to the tensioning element 1a of FIGS. 1 and 2. The only difference is that the support webs 4 of the tensioning element 1b have an end shoulder 7. These shoulders 7 serve to actuate the clamping element 1b axially by means of a corresponding device, not shown here, during clamping and unclamping of a corresponding workpiece 3.

The clamping element 1c of FIGS. 8 to 12 also essentially corresponds to the clamping element 1a of FIGS. 1 and 2. The difference here is that the elastic intermediate links 5 of the clamping element 1c are designed in the form of a meander forming a double loop. In this embodiment, the support webs 4 do not have any shoulders 7 at the front and no corresponding device for relaxing the workpiece 3 is required, since the webs 4b of the support webs 4 and the support element 2 have a much steeper cone to prevent self-locking to be able to exclude when relaxing the workpiece 3.

FIG. 13 shows a further embodiment similar to FIG. 1. The difference is that, in this embodiment, no separate support element 2 is required, since the clamping element 1 d is hereby received between the tips of a machining or measuring machine. and on the other hand that the outer diameter of the clamping element ld is reduced on both sides to such an extent that the workpiece 3 which is geometrically related to its bore can be machined or measured all around in one clamping. The elastic intermediate members 5 of this clamping element ld are performed in a similar manner as that of the clamping element la and covered by means of segment strip 6 to the outside. In this case, so-called sealing disks 8, which are supported on the tips of the processing machine, serve to seal the clamping element 1.

By appropriate corresponding to the end faces of the clamping elements la and lb face plates, the interior between the completely closed clamping elements la and lb according to Figures 1 to 7 and the associated support elements 2 hermetically sealed and thus dust-free. The reference numerals 2 to 8 relate to the parts of all embodiments and are therefore added to the individual figures only as needed. To clarify the form-fitting deviation in the meeting of conical surfaces with different radii and the resulting gap A can be made to the schematic diagrams of FIG. 17 and 18. The distance A shown there between the curved surfaces, or in other words the gap A results from the relationship

A = r - R + (R ^A 2 - b ^A 2) ^A 0.5 - (r ^A 2 - b ^A 2) ^A 0.5

In which

r the smaller radius,

R is the larger radius and

b half the bridge width

are.

Fig. 23 shows a further embodiment of a chip element according to the invention. In this embodiment, two elastic intermediate members 5 'and 5 "are provided, which connect two adjacent support webs 4' and 4" with each other. Here, the elastic intermediate member 5 'connects the support webs 4' and 4 "in an outer region. The elastic intermediate member 5 "connects the support webs 4 'and 4" in an inner area. In other words, the elastic intermediate member 5 'is adjacent to the outer circumferential surface 10 and the elastic intermediate member 5 "is adjacent to the inner circumferential surface. 9 FIG. 24 shows a perspective view of a clamping element with an external thread 11. This example is a conical external thread, but this is not mandatory. The external thread 11 may also be cylindrical.

In Fig. 25, a clamping element is shown with an internal thread 12. This is a cylindrical internal thread 12. The clamping element has a conical outer contour. To increase the wear resistance of the clamping element, it is advantageous if the support webs are at least partially formed of a wear-resistant material. According to Figure 26, the support webs 4 deposits 13, 14. The inserts 13 are arranged on the outside and the inserts 14 inside in the support webs. The inserts 13, 14 are preferably in particular soldered carbide insert. The inserts 13, 14 are used in this case provided in the supporting webs Aussparrungen. The inserts 13, 14 preferably extend over the entire axial extent of the support webs 4. Fig. 28 and Fig. 29 show a further embodiment of a clamping element with inserts 15. In this embodiment, the inserts 15 extend over an entire height of the support webs 4th

To form the tensioning element according to FIG. 28, a blank or semi-finished product 16 is provided. This is shown in FIGS. 30 and 31. The blank 16 has at its end faces in each case an auxiliary ring 17, 18. An auxiliary ring 17 is connected directly to the front side of the support webs 4. The other auxiliary ring 18 is connected by webs 19 on the front side and thus directly to the support webs 4. Each support bar 4 has a recess 20, in each of which an insert 15 can be introduced. The inserts 15 are preferably cemented carbide inserts which are preferably brazed to the support webs 4. After soldering the inserts and the finishing of the clamping element, the auxiliary rings 17 and 18 and the webs 19 are removed.

Finally, it should also be pointed out that other clamping elements, regardless of their shape, round or square, as well as other machine components produced using the innovation according to the invention, such as centering and sliding bearings, braking, stretching and compensating elements and the like. subject to this protection claim.

Although the technology of modern 3D manufacturing processes has proven advantageous for all these elements, other materials and methods of manufacture can be used therefor.

LIST OF REFERENCE NUMBERS

1 clamping element in general

la clamping element of FIGS. 1 and 2

lb clamping element of Fig. 3 to 7

1c clamping element of FIGS. 8 to 12

ld clamping element of FIGS. 13 to 16

2 support element

2a supporting surface of the clamping element

3 workpiece (tool)

4 carrying bridge

4 'carrying bridge

4 "support bar

4a back of the support bar 4

4b Bridge of the carrying bridge 4

4c recess of the support web. 4

5 elastic intermediate member

5 'elastic intermediate member

5 "elastic intermediate link

5a buckle of the elastic intermediate member. 5

6 segment strips

7 shoulder

8 sealing washer

9 outer surface of the support webs

10 inner lateral surface of the support webs

11 external thread

12 internal thread 13 deposit

14 deposit

15 deposit

16 blank

17 auxiliary ring

18 auxiliary ring

19 footbridge

20 recess for the insert

Claims

claims

1. clamping element (1) for positioning and / or fixing a workpiece (3) or tool, comprising a plurality of support webs (4), each having an inner and an outer lateral surface (10, 9) and a plurality of elastic intermediate links (5), in which the tensioning element (1) can be expanded or compressed by stretching or compression of the elastic intermediate links (5), characterized

that the clamping element is produced in a 3-D method, that the elastic intermediate members (5) have a thickness between 0.2 mm and 0.8 mm, and

that the intermediate members (5) spaced from the outer surface (9) and the inner surface (10) of the support webs (4) are arranged and connected to the support webs (4) in one piece and endless.

Second clamping element (1) according to claim 1, characterized in that

in that the elastic intermediate links (5) are designed in such a way that the supporting webs (4) can be placed parallel to a reference system of the clamping element (1) against the surfaces facing them.

3. clamping element (1) according to claim 1 or 2, characterized in that in each case an elastic intermediate member (5) between two or more interconnected support webs (4) is arranged.

4. Clamping element (1) according to one of the preceding claims, characterized characterizes the elastic intermediate links (5) are designed as a meander-shaped connection of the carrier webs (4).

5. clamping element (1) according to one of the preceding claims 1 to 4, characterized

in that the support webs (4) are designed such that the maximum gap (A) resulting during the fixing and / or tensioning operation, between the curvature of the end face on the webs (4b) of the support webs (4) and the support surface (2a) of the support element (2) is smaller than the allowable runout.

6. clamping element (1) according to one of the preceding claims 1 to 5, characterized

the elastic intermediate links (5 ', 5 ") are designed such that the carrier webs (4', 4") are connected to one another in the outer and in the inner region.

7. Clamping element (1) according to one of the preceding claims 1 to 6, characterized

that the outer and / or the inner lateral surface (9, 10) with a

Thread is provided.

8. Clamping element (1) according to one of the preceding claims 1 to 7, characterized

that their inner and outer circumferential surfaces (9, 10) and one of their two end faces are mechanically finished in one and the same clamping.

9. tensioning element (1) according to at least one of the preceding claims, characterized in that

that the clamping element is produced in the laser melting process.

10. clamping element (1) according to at least one of the preceding claims, characterized

in the case of parts which come into contact with one another during a tensioning operation, the support webs (4) and the support element (2) are formed such that the respective outer radius is greater than the inner radius.