DE102004043303B4 - Clamping system for machining centers - Google Patents

Abstract

Clamping element (1) for frictional and positive clamping of workpieces to be machined in a machining center, in particular a milling machine, with a clamping body (2), which can be positioned via fastening means (3) and positioning means (4) positionable on a machine table of the machining center and a Support surface (5) for supporting the workpiece to be machined from above and a contact surface (6) for the defined lateral abutment of the workpiece, and with respect to the clamping body (2) movably mounted clamping piece, taken with the workpiece to be machined and relative to the machine table can be fixed, characterized in that the clamping piece is designed as a clamping claw (7) having a claw edge (8) for deforming engagement in the workpiece surface, that the clamping claw (7) relative to the clamping body (2) about a pivot axis (9) pivoted, that is a Vorschubelemen t (10) is provided, with which the clamping claw (7) by means of a feed movement from a starting position about the pivot axis (9) can be pivoted their storage, and that a return element (11) is provided, with which the clamping claw (7) against the direction (12) of the advancing movement of the advancing element (10) can be pivoted back into its starting position, wherein the clamping claw (7) in a cavity (14) of the clamping body (2) is arranged in the direction of action of the clamping claw (7) is open, and a cover (15) is provided, with which the cavity (14) with the clamping claw (7) is covered, wherein the return element (11) comprises a spring element whose spring force on the clamping claw (7) In acting in a manner that when the feed element (10) is not actuated, a pivoting of the clamping claw (7) takes place in its initial position, and wherein the spring element is designed as a compression spring and on a direction (1 2) of the feed movement parallel pressure axis (13) acts linearly on the clamping claw (7), wherein the compression spring is arranged so that the pivot axis (9) of the clamping claw (7) skewed to the pressure axis (13) and to the axial direction (12) the feed movement between the pressure axis (13) and the axial direction (12) of the feed movement runs.

Description

The invention relates to a clamping element for the frictional and positive clamping of workpieces to be machined in a machining center, in particular a milling machine, with a clamping body, which can be positioned via fastening means and positioning on a machine table of the machining center and a support surface for supporting the workpiece to be machined has above and a contact surface for the defined lateral abutment of the workpiece, and with a relative to the clamping body movably mounted clamping piece, with which the workpiece to be machined taken and can be fixed relative to the machine table.

Such clamping element are known per se, for example, from the brochure "Device Systems", 1990 edition, the company Erwin Halder KG, Achstetten-Bronnen.

When processing metallic workpieces in machining centers, such as CNC milling machines, the work piece blank must be positioned as accurately as possible relative to the machine table of the machining center and then securely fixed before starting the machining by means of a system of clamping elements. For the processing of cuboid continuous casting or chill casting blanks a clamping of the workpiece with a certain distance from the machine table is required so that the blank can be processed without damaging the machine table and also also leaves room for the metal chips always accumulating during machining. For this purpose, the blank is braced, for example between the jaws of a vise, with a jaw stationary and the other is relatively linearly movable. The jaws have flat surfaces for accurate positioning of the blank to be clamped. However, in particular cast blanks practically never usable, defined smooth clamping surfaces. Therefore, in such cases, first at least two clamping surfaces must be milled to the blank in order to clamp it defined behind between the flat surfaces of the clamping jaws of the vise can. The additional processing time for the milling of such clamping surfaces is depending on the size of the blanks and their contour between half an hour and generates considerable additional costs in manufacturing.

If the blanks have particularly irregular contours, more than two clamping surfaces may be required. It may also happen that the vise is not large enough or geometrically insufficient receptive to aufzuspannen the blank. In this case, clamps are often used. But this is only possible if the Spannpratzen the machining of the workpiece do not stand in the way. The use of clamping claws is particularly difficult in the case of workpieces in which breakthroughs have to be made or where machining from several sides is required.

With a complete three-dimensional milling of the workpiece or even with a required full-surface milling from above, all clamping systems acting from above can not be used. In such cases, only the use of flat tensioners could help so far, but in such a clamping then no drilling through of the workpiece is possible without damaging the immediately underlying machine table, so that several complex Umspannungen for processing a single workpiece were required.

Schreyer, K .: "Workpiece tensioner (devices)", third improved and expanded edition, Berlin, Springer-Verlag, 1969, pages 111 to 125 discloses clamping elements with a clamping lever designed as a clamping piece, which is designed to hold the workpiece securely cutting-like. The clamping lever is pivotally mounted relative to the clamping body about a pivot axis and can be pivoted by means of a feed movement from a starting position about the pivot axis of its mounting. Further, a return element is provided in the form of a compression spring, with which the clamping lever can be pivoted back against the direction of the feed movement of the feed element to its original position.

The article by Blanpain, E .: "PREPARATION DE L'USINAGE DE PIECES CLAMEES SUR TABLE" in: MACHINE MODERNE, June 1954, pages 9 to 12, discloses a clamping lever with a sharp edge which is pivotally mounted relative to a clamping body of a clamping element is. Further, this document discloses a clamping lever without sharp edge, on the lower arm a feed element and on the upper arm engages a return element.

Object of the present invention is to provide technically simple and inexpensive to produce clamping means, which are also favorable for the single piece machining and for small batches and allow both a frictional connection and a positive connection between the workpiece and clamping means and can be used to save time without prior milling of clamping surfaces. With the clamping means according to the invention and large workpieces for multilateral processing are to be securely clamped in the machining center, wherein in the clamping operation on low tensile forces The workpiece should be exercised to ensure a firm grip even with strong vibrations.

According to the invention this object is achieved by a clamping element according to claim 1.

With a clamping system consisting of at least three, usually four clamping elements according to the invention a virtually arbitrarily shaped workpiece blank can be clamped easily from all sides in a machining center even for the most complicated, three-dimensional processing, all processing steps can be made in a single setup, without that at the same time the machine table of the machining center is endangered. The pivotable clamping claws are moved by means of the feed elements against the blank to be clamped until the claw edge deformingly engages the surface of the workpiece. This allows a secure positive connection. In addition, on the opposite of the pivotable clamping claw fixed clamping body a flat support surface and a likewise flat contact surface for the defined lateral abutment of the workpiece are provided. However, a prior milling of clamping surfaces in the workpiece is eliminated because already ensure the clamping claws for a defined and secure grip. When unclamping the machined workpiece, the advancing element is withdrawn and the return element returns the pivotable clamping claw to its original starting position (or any intermediate position), so that engagement of the claw edge in the tool surface is released.

Particularly preferred is an embodiment of the clamping element according to the invention, in which the advancing element can perform a linear advancing movement against the clamping claw. The feed effect could also be generated by a curved feed motion, but a linear motion is mechanically much easier to accomplish.

In a particularly advantageous development of this embodiment, the feed element comprises a threaded pin, preferably with a fine thread, which on the one hand allows a particularly accurate feed movement, on the other hand acts self-locking especially during vibration during workpiece machining.

Alternatively, in other developments of the embodiment described above, the feed element also comprise a hydraulic piston which can automate the feed and return movement and also perform with high accuracy, with the feed movement and larger forces can be applied to clamp the blank.

A particularly preferred further development of this embodiment provides that the spring element is designed as a compression spring and acts linearly on the clamping claw on a pressure axis parallel to the direction of the feed movement, wherein the compression spring is arranged so that the pivot axis of the clamping claw askew, especially at right angles between the pressure axis and the axial direction of the feed movement runs. Therefore, the compression spring exerts a constant pressure on one side of the clamping claw, so that upon retraction of the advancing element, a pivoting in the direction of the retracting advancing element is automatically effected. The compression spring is particularly easy to install and requires no special mechanical attachment points on the clamping claw, but can be stored in a simple blind hole in the clamping body.

In an alternative development, the spring element is designed as a tension spring and acts on a parallel to the direction of feed movement pull axis on the clamping claw, wherein the tension spring is arranged so that the pivot axis of the clamping claw askew, especially at right angles to that of the traction axis and the axial direction of the feed motion spanned plane extends and that the traction axis and the axial direction of the feed movement on the same side with distance from the puncture point of the pivot axis lie through this plane. Since in this case the return element with respect to the pivot axis on the same side as the feed element, the arrangement can be made more compact overall, but requires special attachment points between tension spring and clamping claw on the one hand and tension spring and clamping body on the other.

It is advantageous that the clamping claw is arranged in a cavity of the clamping body, which is open in the effective direction of the clamping claw to the workpiece to be machined, and that a cover is provided, with which the cavity is covered with the clamping claw. In this way, the movable clamping claw and especially its swivel bearing is optimally protected against soiling and mechanical damage from almost all sides.

Preferably, the cover comprises a spring plate which is fixed on the clamping body and the clamping claw covers resiliently upwards. If the clamping claw escapes at its pivoting upward, the spring plate can yield back resiliently.

Particularly preferred is a development in which the cover is removably mounted by means of a fastening screw on the clamping body. In this way, the clamping body can be easily replaced after removing the cover.

In simple developments, the cover can also be glued to the clamping body, in particular with a common metal adhesive. Although this type of connection is particularly easy to effect, but not always completely reversible.

To protect the clamping claw and cover, it is advantageous if the clamping claw on its side facing the cover has a radius which is designed so that when a movement of the clamping claw around its pivot axis despite spatial proximity to the cover prevents abutment of the clamping claw on the cover becomes.

Also preferred is an embodiment of the clamping element according to the invention, in which the positioning means for positioning the clamping body relative to the machine table of the machining center comprise a sliding block, which is preferably screwed to the clamping body. The sliding block can be used for the purpose of positioning in one of the usually existing in machine tables of machining centers parallel longitudinal grooves or in a groove of a corresponding intermediate piece. When using screws for fastening the sliding block on the clamping body and sliding blocks of different sizes can be easily installed.

Alternatively, in other embodiments of the clamping element according to the invention, the positioning means for positioning the clamping body relative to the machine table of the machining center comprise a feather key. This also makes it possible to make a precise positioning of the clamping element relative to the machine table.

In a further preferred embodiment of the tensioning element according to the invention, the fastening means for reversibly fixing the tensioning body relative to the machine table of the machining center may comprise at least one, preferably two, threaded assemblies.

Advantageously, the screws of the screw assemblies in developments of this embodiment on bevelled surfaces of the clamping body from above operable. The bevel of the surfaces on the one hand saves material and thus weight, on the other hand facilitates the slope and the insertion and actuation of the screws, because it provides better access to the screws.

In a further embodiment of the invention, an intermediate plate is provided which can be arranged between the clamping body and the machine table of the machining center. This can on the one hand cause height variations when clamping the blank over the machine table of the machining center, on the other hand can be done in this way a clamping also perpendicular to the grooves extending in the machine table grooves.

Finally, in a further preferred embodiment of the clamping element according to the invention, a defined lateral stop for the workpiece to be machined is provided on the clamping body. This makes it possible to achieve a particularly high accuracy when clamping the workpiece.

Advantageously, the lateral stop is reversibly screwed to the clamping body. Thus, the lateral stop can also be screwed as needed on the other side of the clamping body or omitted altogether.

Further features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention with reference to the figures of the drawing, which shows details essential to the invention, and from the claims. The individual features may be implemented individually for themselves or for a plurality of combinations in variants of the invention.

In the schematic drawing embodiments of the invention are shown, which are explained in more detail in the following description.

• 1 einen vertikalen Längsschnitt durch ein erfindungsgemäßes Spannelement mit Zwischenplatte in schematischer Darstellung; und
• 2 einen vertikalen Schnitt rechtwinklig zum Schnitt nach 1.

Show it:

• 1 a vertical longitudinal section through an inventive clamping element with intermediate plate in a schematic representation; and
• 2 a vertical section perpendicular to the section to 1 ,

That in the 1 and 2 schematically illustrated clamping element 1 for non-positive and positive clamping of workpieces to be machined in a machining center has a clamping body 2 on top of the fastener 3 , in particular screws, for which in the drawing only the through holes are drawn, as well as positioning means 4 , shown schematically in the drawing as sliding blocks, can be positioned positionable on a machine table of the machining center. Furthermore, the clamping body 2 a support surface 5 for supporting the workpiece to be machined from above and a contact surface 6 for the defined lateral application of the workpiece. One opposite the clamping body 2 movably mounted clamping piece, with which the workpiece to be machined can be taken and fixed relative to the machine table, is as a clamping claw 7 executed, which is a claw edge 8th For deforming engagement in the workpiece surface has. The clamping claw 7 is opposite the clamping body 2 about a pivot axis 9 pivoted. There is also a feed element 10 provided, which will preferably be designed as a linearly movable threaded pin with fine thread, and with which the clamping claw 7 by means of a feed movement from an initial position about the pivot axis 9 their storage can be pivoted. Finally, it is also a return element 11 provided, which is designed in the present case as a compression spring, with which the clamping claw 7 against the direction 12 the feed movement of the feed element 10 can be pivoted back in its starting position or any intermediate position. For this purpose, the compression spring of the return element 11 arranged so that its pressure axis 13 parallel to the direction 12 the feed movement of the feed element 10 runs, wherein the pivot axis 9 the clamping claw 7 right-angled between the pressure axis 13 and the axial direction 12 the feed movement pierces the plane spanned by the two axes level.

The clamping claw 7 is in a cavity 14 of the clamping body 2 arranged in the direction of action of the clamping claw 7 open to the workpiece to be machined. At the top is the cavity 14 with a cover 15 covered, which includes a spring plate, which on the clamping body 2 is detachably mounted by means of a fastening screw, for which a threaded hole 19 indicated in the drawing.

Furthermore, the clamping claw 7 on her cover 15 facing side a radius 16 on, which is designed so that during a movement of the clamping claw 7 around its pivot axis 9 despite the proximity to the cover 15 an abutment of the clamping claw 7 to the cover 15 is avoided.

The cavity 14 in which the pivotable clamping claw 7 is included, as well as one on the opposite side of the clamping element 1 in the clamping body 2 attached further cavity 14 ' serve the accessibility of fastening screws for the fasteners 3 from above. The corresponding side surfaces 17 . 17 ' of the clamping body 2 are beveled for better accessibility and also to save material.

For height variation of the clamping over the machine table as well as for the possibility of a perpendicular to the groove direction of the machine table extending parallel grooves in the embodiment shown in the drawing is an intermediate plate 18 provided between the clamping body 2 and the machine table of the machining center can be arranged. The intermediate plate 18 in turn can intervene by means of sliding block in the grooves of the machine table.

Not shown in the drawing is a defined lateral stop for the workpiece to be machined, which has threaded holes 20 . 20 ' on the clamping body 2 can be screwed.

LIST OF REFERENCE NUMBERS

1

clamping element

2

tensioning body

3

fastener

4

positioning

5

bearing surface

6

contact surface

7

clamping claw

8th

gripping edge

9

pivot

10

feed element

11

return element

12

Direction of the feed movement

13

pressure axis

14.14 '

cavity

15

cover

16

radius

17.17 '

bevelled surfaces

18

intermediate plate

19

Threaded hole for cover

20.20 '

Tapped holes for lateral stop

Claims (16)

Clamping element (1) for frictional and positive clamping of workpieces to be machined in a machining center, in particular a milling machine, with a clamping body (2), which can be positioned via fastening means (3) and positioning means (4) positionable on a machine table of the machining center and a Support surface (5) for supporting the workpiece to be machined from above and a contact surface (6) for defined lateral abutment of the workpiece, and with a relation to the Clamping body (2) movably mounted clamping piece, with which the workpiece to be machined taken and can be fixed relative to the machine table, characterized in that the clamping piece is designed as a clamping claw (7) having a claw edge (8) for deforming engagement in the workpiece surface in that the clamping claw (7) is pivotably mounted relative to the clamping body (2) about a pivot axis (9), that a feed element (10) is provided, with which the clamping claw (7) is moved by means of a feed movement from an initial position about the pivot axis (9 ) can be pivoted their storage, and that a return element (11) is provided, with which the clamping claw (7) against the direction (12) of the advancing movement of the advancing element (10) can be pivoted back to its original position, wherein the clamping claw (7 ) is arranged in a cavity (14) of the clamping body (2), in the direction of action of the clamping claw (7) to be processed We Rückstück is open, and a cover (15) is provided, with which the cavity (14) with the clamping claw (7) is covered, wherein the return element (11) comprises a spring element whose spring force on the clamping claw (7) in a Acts that when the feed element (10) is not actuated pivoting of the clamping claw (7) to its initial position, and wherein the spring element is designed as a compression spring and on a to the direction (12) of the feed motion parallel pressure axis (13) linearly on the clamping claw (7) acts, wherein the compression spring is arranged so that the pivot axis (9) of the clamping claw (7) skewed to the pressure axis (13) and to the axial direction (12) of the feed movement between the pressure axis (13) and the axial direction (12 ) of the feed movement runs. Clamping element after Claim 1 , characterized in that the advancing element (10) can perform a linear advancing movement against the clamping claw (7). Clamping element after Claim 2 , characterized in that the feed element (10) comprises a threaded pin, preferably with a fine thread. Clamping element after Claim 2 , characterized in that the advancing element (10) comprises a hydraulic piston. Clamping element according to one of Claims 1 to 4 , characterized in that the compression spring is arranged so that the pivot axis (9) of the clamping claw (7) at right angles to the pressure axis (13) and to the axial direction (12) of the feed movement. Clamping element according to one of Claims 1 to 5 , characterized in that the cover (15) comprises a spring plate which is fixed on the clamping body (2) and the clamping claw (7) covers resiliently upward. Clamping element according to one of Claims 1 to 6 , characterized in that the cover (15) is removably mounted by means of a fastening screw on the clamping body (2). Clamping element according to one of Claims 1 to 7 , characterized in that the cover (15) with the clamping body (2) is glued. Clamping element according to one of Claims 1 to 8th , characterized in that the clamping claw (7) on its the cover (15) side facing a radius (16) which is designed so that upon movement of the clamping claw (7) about its pivot axis (9) despite spatial proximity to Cover (15) abutment of the clamping claw (7) to the cover (15) is avoided. Clamping element according to one of the preceding claims, characterized in that the positioning means (4) for positioning the clamping body (2) relative to the machine table of the machining center comprise a sliding block, which is preferably screwed to the clamping body (2). Clamping element according to one of Claims 1 to 9 , characterized in that the positioning means (4) for positioning the clamping body (2) relative to the machine table of the machining center comprise a feather key. Clamping element according to one of the preceding claims, characterized in that the fastening means (3) for reversibly fixing the clamping body (2) relative to the machine table of the machining center comprise at least one, preferably two Schraubverbände. Clamping element after Claim 12 , characterized in that the screws of the screw assemblies on bevelled surfaces (17, 17 ') of the clamping body (2) are operable from above. Clamping element according to one of the preceding claims, characterized in that an intermediate plate (18) is provided, which can be arranged between the clamping body (2) and the machine table of the machining center. Clamping element according to one of the preceding claims, characterized in that the clamping body (2) is provided a defined lateral stop for the workpiece to be machined. Clamping element after Claim 15 , characterized in that the lateral stop is reversibly screwed to the clamping body (2).

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