DE102009049451B3 - Clamping element for shrink tensioning of bodies of drilling tool, has circular joint element that is arranged between base body and closed tension ring and is fixed to both base and tensioning ring - Google Patents

Abstract

The element (1) has a circular joint element (5) that is arranged between a base body (3) and a closed tension ring (6) and is fixed to both the base and the tensioning ring. Interrupts are formed on a circumference of the joint element. A wall thickness of the joint element constantly decreases along a section in a direction of the tension ring. The joint element tapers partially both in an inner diameter and an outer diameter in a direction of the tension ring. The Clamping element is made of chrome steel.

Description

The invention relates to a clamping element for shrinking clamped bodies with an oval clamping circumference, comprising a base body and a closed clamping ring and a clamping device comprising a clamping element for shrinking and clamping means for heating the clamping element.

A clamping element and a clamping device of the aforementioned type for tools, in particular for a drilling tool, are from the DE 199 15 412 A1 known. The tool holder disclosed therein has at its free end an open sleeve portion which forms the clamping ring. The sleeve portion is integrally supported on a base body having a coupling element for connecting a shaft or spindle. In order to be able to clamp a tool, the tool holder in the area of the sleeve section is heated inductively up to 450 ° C, for example. The tool is inserted into the heated sleeve section. The sleeve section, which has an undersize at room temperature with respect to the outer circumference of the tool, shrinks on cooling on the tool and fixes it frictionally. The tool holder is solid as a whole, in order to ensure the mechanical stability in the overall device with clamped tool can. Due to the relatively small circumference of the tool holder must be selected with said 450 ° C, a relatively high temperature in order to effect a sufficient opening of the sleeve portion can. In this case, special measures are necessary to avoid unwanted high heating of the inserted tool. Due to the compact design for small diameter tools, the tool holder can handle the large temperature fluctuations without damage. The problem, however, is the small diameters at the given absolute expansion or shrinkage of the sleeve section, because of such a procedure is only possible in the usually very tightly tolerated tools. If a workpiece to be machined is clamped in a clamping device corresponding to the aforementioned prior art, the necessary tolerances are generally not reached. The choice of higher temperatures to achieve a higher expansion usually prohibits, since too high heating, z. B. on the AC1 temperature, adversely affect the material properties of the clamping sleeve. In addition, the high temperature load of the workpiece in contact with the clamping body and the associated influences on the material properties of the workpiece would be disadvantageous. Finally, the known geometries for many materials generate too high stresses in the workpiece to be clamped.

For the application of tools or workpieces of larger diameter, for example, more than 600 mm, the application of the shrinkage stress is usually not provided. The associated recordings would have to be made large accordingly. Sufficient heating of the overall device would be too time consuming.

During turning, workpieces are usually clamped with three-jaw chucks. These have the advantage of being geometrically unambiguous and self-centering. For large diameters, however, the force application points of a three-jaw chuck are far apart, so that high circumferential moments are introduced during clamping in the workpiece and the workpieces can be greatly deformed during clamping.

For operations with low accuracy requirements, large diameter three-jaw chucks with pendulum jaw pads are used but are limited in stability. For high accuracy requirements, for example in engine construction, the workpiece clamping is usually no longer radially, but with the help of special devices in the axial direction. These devices require alignment with the concentricity and severely limit the accessibility of the workpiece during machining, since they partially enclose the workpiece in principle.

It is now an object of the present invention to provide a clamping element and a clamping device of the type mentioned are available, which are also suitable for clamping chucks larger scope.

In a clamping element of the type mentioned, this object is achieved by the characterizing features of claim 1.

An arranged between the clamping element and the base body and fixed to the clamping ring hinge element can absorb elastically generated differences between the clamping ring and body in the radial thermal expansion. Furthermore, the heating can be essentially limited to the clamping ring. At the same time, the annular geometry of the joint element ensures sufficient stability of the clamping in the radial direction, which prevents undesired lateral translations when loaded by process forces. In addition, an undesirable high heat transfer to the body can be largely avoided with a suitable wall thickness of the joint element.

A high temperature gradient forms between the clamping ring and the main body when the heat energy necessary for heating the clamping ring is input essentially solely into the clamping ring. The particular for large clamped body with diameters of z. B. more than 600 mm usually solid body of the clamping element does not need to be heated, whereby a considerable energy saving is given.

For a given temperature gradient, the joint element causes, seen in the lateral cross section, each section of the clamping ring during its heating and shrinking relative to the base body each performs a movement with rotational component, since the body hardly or at least not to the same extent radially expands as the clamping ring. The joint element thus makes it possible for a base body that is not or only slightly heated, its dimensions so not or only slightly changes, the union of two per se contradictory effects, namely both for inserting or releasing the body to be clamped necessary widening and holding the body, so blocking the movement relative to the body.

It is advantageous that reduce the necessary for a sufficient opening of the clamping ring temperatures with increasing diameter of the workpiece or tool to be clamped. With a workpiece diameter of 600 mm are sufficient with suitable clamping ring material, eg. As iron, and suitable geometry 100 ° C. Nevertheless, considerable mechanical stresses are generated in the joint element or in the transition regions between the joint element and the clamping ring or base body, even at these temperatures due to the temperature gradient to the base body, which is generally at room temperature. However, with suitable geometry of the joint element, these stresses can be well absorbed even at relatively high clamping ring temperatures, that is, even with smaller workpiece or tool diameters.

The annular joint element may be formed closed over its circumference, whereby the joint element can be formed correspondingly stable.

But it is also possible to provide interruptions in the circumference of the annular joint element. Thus, separate webs are present between clamping ring and body, whereby the elasticity of the joint element can be increased.

It may be advantageous to provide a steadily decreasing wall thickness in the joint element at least along a partial stretch in the direction of the clamping ring. As a result, a small cross section is created in the transition to the clamping ring, whereby the heat conduction is reduced in the direction of the body. At the same time a sufficient stability can be ensured. The decrease in wall thickness can z. B. be proportional to the root of the distance between the body and clamping ring, whereby a uniform stress distribution can be achieved.

Furthermore, it may be advantageous to design the clamping element in such a way that the hinge element tapers at least in regions both in the inner diameter and in the outer diameter in the direction of the clamping ring. This means that the walls of the joint element are inclined in their course to the clamping ring to the longitudinal axis of the clamping element. This tendency causes when cooling the clamping ring, that this not only biases in the radial direction, but at the same time receives an axial component of movement in the direction of the body. As a result, a Niederzughalterfunktion is given for the clamped workpiece.

In its geometry, the clamping ring corresponds to the shape of the clamping circumference of the body to be clamped. In most cases, the chuck circumference will be circular as a special case of the oval shape. Accordingly, the clamping ring in these cases is to make circular. Alternatively, however, even with appropriate geometry of the body to be clamped elliptical or generally egg-shaped clamping rings are conceivable, wherein the joint element has an adapted thereto annular shape.

Furthermore, the clamping element can be designed such that the base element has a bearing surface for an object to be clamped.

The clamping element may advantageously consist of chrome steel. Furthermore, the clamping element can be formed in one piece. In this case, the joint element is designed as a solid-body joint. However, it is also conceivable to fix the joint element releasably on the clamping ring and / or on the base body. The fixation of the joint element on the clamping ring or on the base body can also be pivotally.

Furthermore, the clamping element can also be designed so that the inner diameter of the clamping ring is at room temperature at least 50 mm, preferably at least 100 mm. The advantages of the clamping element affected here become particularly relevant for larger bodies to be clamped.

The joint element preferably has a length of 5 mm to 40 mm, more preferably 10 to 20 mm. The wall thickness is preferably 0.5 mm to 5 mm, more preferably 1 mm to 2 mm. In this case, the wall thickness of the transition to the clamping ring to the transition to the body continuously increase, preferably by at least 10% and at most 100%, more preferably by at least 30% and at most 60%. The inner wall of the joint element should have an angle of 20 ° to 85 °, preferably from 25 ° to 70 °, more preferably from 35 ° to 55 ° to the plane perpendicular to the longitudinal axis of the clamping element from the base body to the longitudinal axis.

In a clamping device of the type mentioned, the aforementioned object is achieved by the characterizing features of claim 11. It can be provided that the means for heating the clamping element for inductive heating of the clamping ring are suitable. However, the heating can alternatively also be carried out with resistance or flame. Inductive heating, however, has precise controllability, contact-free energy coupling and generally homogeneous heating to the advantage. Thus, an inductor can remain stationary while the clamping element is rotated.

The clamping device may further comprise an adapter unit which serves to adapt to different diameters of workpieces or tools to be clamped. It may be an adapter ring that can be hung in the clamping ring. The adapter ring may advantageously be at least partially interrupted on its circumference so that it can yield to the shrinking process of the clamping ring.

In the following, advantageous embodiments will be illustrated with reference to figures. It shows

1 : a section of a clamping element in cross section,

2 : a clamping element in cross-section ( 2a ) and in oblique supervision ( 2 B ) and

3 : the clamping element according to 2 in a detailed view.

4 an adapter ring,

5 : an enlarged section of the adapter ring according to 4 and

6 : the adapter ring according to 4 and 5 mounted in a clamping element.

1 shows in cross section fragmentary a clamping element 1 with a clamped workpiece 2 , The clamping element 1 includes a main body 3 with a support surface 4 for the workpiece 2 , At the base body 3 is an annular joint element 5 fixed in one piece, on which in turn a clamping ring 6 also integrally connected. For clamping the workpiece 2 becomes the clamping ring 6 preferably inductively heated. An induction coil, not shown here, can for this purpose the clamping ring 6 include at a distance, so that even with expansion of the clamping ring 6 no physical contact is made with the induction coil. The induction coil is preferably to be arranged so that it is essentially alone on the clamping ring 6 acts on its outer surface 7 Eddy currents are generated which cover the entire clamping ring 6 heat to the desired temperature. Due to the given during heating longitudinal expansion of the clamping ring 6 becomes the clamping ring 6 extended to a diameter corresponding to that of the workpiece to be clamped 2 exceeds.

The joint element 5 is provided with a relatively small wall thickness D, which extends over the length L of the joint element 5 to the clamping ring 6 even reduced. This provides the hinge element 5 a relatively small cross section, whereby the heat conduction from the clamping ring 6 to the main body 3 is correspondingly low. Thus, the main body 3 barely warmed up, reducing the energy input to widen the clamping ring 6 can be kept low. In the configured as a solid-body joint element 5 creates a temperature gradient, which causes the joint element 5 on the one hand, the expansion movement of the clamping ring 6 follows and on the other to the not or only barely expanding body 3 remains fixed. In its longitudinal extent L, the joint element is to the longitudinal axis of the clamping element 1 inclined so that the clamping ring 6 when heating in addition to the diameter expansion movement in the axial direction of the body 3 experiences away.

After that, the workpiece becomes 2 on the support surface 4 placed. Inductive heating of the clamping ring 6 is set shortly before or after placement or during placement of the workpiece 2 completed. The cooling clamping ring 6 shrinks to the workpiece 2 ,

During the Aufschrumpfbewegung the clamping ring completes 6 due to the inclination of the joint element 5 a movement in the axial direction of the body 3 to. The combined shrinking and axial movement makes the workpiece 2 automatically radially centered and axially defined bearing surface 4 pulled down. The workpiece 2 is curious now. The voltage is thus fault-tolerant, reproducible and stable. The tension is over the joint element 5 and the applied friction between the workpiece 2 and clamping ring 6 very stiff. The workpiece 2 can z. B. by turning or milling, but also with roughing processes with very large mechanical forces are processed at the same time high precision. For workpiece machining is the main body 3 connected to a machine tool, not shown here. The clamping forces are over a relatively large contact surface 8th between clamping ring 6 and workpiece 2 introduced so that only very low local stresses are transmitted to the workpiece by clamping. When relaxing, the workpiece deforms 2 compared to other systems to a lesser extent.

After machining the workpiece 2 becomes the clamping ring 6 reheated. Due to the extent given by the clamping ring 6 becomes the workpiece 2 released and can be removed. For inductive heating of the clamping ring 6 to release the workpiece 2 is on a sufficiently large temperature gradient between clamping ring 6 and workpiece 2 to ensure that a safe separation of the parts is made possible.

Due to the elongated, tapered geometry of the joint element 5 The resulting stresses in the thermal expansion of the clamping ring 6 spread over a large area and thus large openings of the clamping ring 6 allows for low material stress. Furthermore, the geometry of the joint element 5 the heat flow from the clamping ring 6 into the main body 3 inhibited, leaving only a small heat output for opening the clamping ring 6 is required. The curvature-free, stretched geometry of the joint element 5 ensures a stiff and stable storage of the workpiece.

At room temperature, the inner diameter of the clamping ring 6 opposite to the workpiece to be clamped 2 an undersize, which should correspond to an inner diameter after the tolerance field P corresponding to a workpiece having an outer diameter of the tolerance field h. The radial clamping force of the device is governed by the rules of shrink joints and must be designed accordingly. The clamping force can on the one hand on the size of the undersize of the clamping ring 6 On the other hand, be adjusted over its cross-sectional area, wherein an increase in the cross-sectional area of the clamping ring 6 at a given undersize leads to higher clamping forces. The axial clamping action can be via the inclination of the joint element 5 and over whose length L and wall thickness D are set.

The clamping element 1 allows the clamping of workpieces 2 with comparatively large diameters. The thus required large circumferential length of the clamping ring 6 causes only comparatively low heating temperatures for the clamping process and the relaxation process are required. As a rule, with diameters of more than 500 mm the workpiece is sufficient 2 Temperatures below 200 ° C for easy opening of the clamping ring 6 out. Thus, an adverse thermal stress on the workpiece 2 be avoided.

For the in 1 geometry with a workpiece outer diameter of 640 mm and a cross-sectional area of the clamping ring portion of 85 mm ² , an induction power of 10 kW over a period of 10 seconds for heating to 200 ° C has been found to be an opening of about 2 mm above the Diameter to realize. Thus, a simple handling when inserting the workpiece 2 by planting the workpiece 2 on an inner side of the clamping ring 6 and then allowed to cool. Since the clamping element the workpiece 2 clamps self-centering, eliminating a time-consuming alignment of the workpiece 2 on the concentricity. The clamping process can be carried out very quickly by means of induction heating. So z. B. opening in less than 10 seconds. The cooling of the system for the clamping process can also be accelerated by a machine tool usually present coolant lubricant system and also realized in 10 seconds.

As material for the clamping element 1 a tempered chrome steel was used. The clamping element 1 in the above example is made of a single piece, rotationally symmetric and therefore relatively easy to produce. Thus, the manufacturing cost of the clamping element 1 low. The clamping ring 6 had an undersize of 300 μm across the diameter. A separation of the workpiece was possible from a temperature of 70 ° C. As dimensions of the joint element at room temperature have a length L of about 15 mm, a continuously increasing wall thickness D of 1.1 mm at the transition to the clamping ring 6 up to 1.5 mm at the transition to the main body 3 and an angle α of 50 ° between hinge element 5 and the plane of the bearing surface 4 proved to be advantageous.

In the in 1 illustrated example of the clamping element 1 is the joint element 5 Completely closed.

2a and 2 B show on the one hand in a cross section, on the other in oblique view and 3 in an enlarged section an alternative clamping element 9 with a basic body 10 and a clamping ring 11 , The clamping ring 11 gets from one to the main body 10 fixed and in the circumferential direction regular interruptions having joint element 12 held, consisting of numerous equidistantly arranged joint element parts 13 consists. The joint element parts 13 in turn are from one on the main body 10 fixed base piece 14 , one on the clamping ring 11 fixed ring piece 15 and one each the base piece 14 with the associated ring piece 15 connecting joint piece 16 composed. The ring pieces 15 are with their associated links 16 made in one piece. Furthermore, the joint piece 16 swiveling on the associated base piece 14 hinged. This is a special mobility of the respective joint element part 13 given, whereby material stresses even at high temperature differences between clamping ring 11 and basic body 10 in the transition area between the base body 10 and joint element 12 can be avoided. The main body 10 has a support surface 17 on, on the one clamped and not shown here workpiece through the clamping ring 11 in interaction 11 with the joint element 12 is held down.

The 2a to 3 further show radially into the body 10 introduced retaining grooves 18 for receiving fixation elements, not shown here, for fixing the body 10 serve on a machine body, also not shown here.

4 shows an adapter ring 19 in an overall view and 5 in an enlarged section. The adapter ring 19 is used to adapt to slightly different Einspannumfänge between the workpiece to be clamped (in the 4 to 6 not shown) and the clamping ring 6 of the clamping element 1 used. One in the clamping ring 6 hinged adapter ring 19 is in 6 shown.

The adapter ring 19 is from an axially oriented fitting part 20 and a perpendicularly extending holding part 21 assembled in one piece. adjusting portion 20 and holding part 21 have common Ausgleichsnuten 22 on holding the holding part 21 each complete and the fitting part 20 except for one end area 23 pull through, the end area 23 So forms a closed ring (see 5 ). The holding part 21 thus consists of the adjacent Ausgleichsnuten 22 separated holding part elements 24 that z. B. can be generated by a Abkantprozess. To every clamping element 1 can be a set of adapter rings 19 present, which are different wall thicknesses in the fitting part 20 differ.

The outer radius of the end area 23 of the fitting part 20 each to a clamping element 1 belonging adapter ring 19 is greater at room temperature than the inner diameter of the clamping ring 6 , Should now one in the 4 to 6 not shown workpiece are clamped, the radius in the clamping area is too low to the clamping ring 6 to be clamped securely, first, the clamping ring 6 widened. Subsequently, the fitting for a workpiece to be clamped adapter ring 19 in the clamping ring 6 hooked by the holding part 21 on the clamping ring 6 is hung up. Due to the expansion of the clamping ring 6 can the adapter ring 19 introduce without further ado. Subsequently or simultaneously, the workpiece to be clamped on the support surface 4 of the clamping element 1 placed in the orientation provided for clamping. When cooling and thus shrinking of the clamping ring 6 becomes the adapter ring 19 applied to the workpiece, not shown here. The necessary radius reduction in the adapter ring 19 is through the compensation grooves 22 allows. The end area 23 of the fitting part 20 is located below the clamping ring 6 ,

LIST OF REFERENCE NUMBERS

1

clamping

2

workpiece

3

body

4

bearing surface

5

joint element

6

clamping ring

7

outer surface of the clamping ring

8th

contact area

9

clamping

10

body

11

clamping ring

12

joint element

13

Joint element part

14

base piece

15

banjo

16

joint piece

17

bearing surface

18

retaining groove

19

adapter ring

20

adjusting portion

21

holding part

22

equalizing groove

23

end

24

Holding part element

Claims (17)

Clamping element for shrinking bodies to be clamped ( 2 ) with an oval clamping circumference, comprising a base body ( 3 ) and a closed clamping ring ( 6 ), characterized by an intermediate body ( 3 ) and clamping ring ( 6 ) and arranged on the base body ( 3 ) as well as on the clamping ring ( 6 ) fixed, annular joint element ( 5 ). Clamping element according to claim 1, characterized in that the annular joint element ( 5 ) is closed over its circumference. Clamping element according to claim 1, characterized in that the annular joint element ( 5 ) has interruptions on its circumference. Clamping element according to one of the preceding claims, characterized in that the wall thickness of the joint element ( 5 ) at least along a partial stretch in the direction of the clamping ring ( 6 ) decreases steadily. Clamping element according to one of the preceding claims, characterized in that the joint element ( 5 ) at least partially both in the inner diameter and in the outer diameter in the direction of the clamping ring ( 6 ) rejuvenated. Clamping element according to one of the preceding claims, characterized in that the clamping ring ( 6 ) is circular. Clamping element according to one of the preceding claims, characterized in that the basic body ( 3 ) a support surface ( 4 ) for the body to be clamped ( 2 ) having. Clamping element according to one of the preceding claims, characterized in that the clamping element ( 1 ) consists of chrome steel. Clamping element according to one of the preceding claims, characterized in that the clamping element ( 1 ) is integral. Clamping element according to one of the preceding claims, characterized in that the inner diameter of the clamping ring ( 6 ) at room temperature at least 50 mm, preferably at least 100 mm. Clamping device comprising a clamping element ( 1 ) for shrinking, and means for heating the clamping element, characterized in that a clamping element ( 1 ) is provided according to one of claims 1 to 10. Clamping device according to claim 11, characterized in that the means for heating the clamping element ( 1 ) for inductive heating of the clamping ring ( 6 ) are suitable. Clamping device according to claim 11 or 12, characterized by at least one for insertion into the clamping ring ( 6 ) provided adapter unit ( 19 ). Clamping device according to claim 13, characterized in that the adapter unit ( 19 ) is annular. Clamping device according to claim 13 or 14, characterized in that the adapter unit ( 19 ) at least two for placing the adapter unit ( 19 ) on the clamping ring ( 6 ) provided suspension elements ( 24 ) having. Clamping device according to one of claims 13 to 15, characterized in that the adapter unit ( 19 ) has interruptions in the circumferential direction. Clamping device according to claim 16, characterized in that the interruptions in the axial direction are not continuous.

Images