This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2021 119 935.2, filed Jul. 30, 2021; the prior application is herewith incorporated by reference in its entirety.
The invention relates to a clamping chuck for clamping tools having a tool shank, including a sleeve portion which is open at its free end, is preferably composed of electrically conductive material and forms a tool-holding fixture for frictionally locking fixing of the tool shank in a press fit by shrink-fitting. The invention also relates to a method of using the clamping chuck for high-speed cutting, in particular for high-speed milling, and a tool-clamping system including at least one tool-clamping chuck and a shank tool.
Clamping chucks in the form of shrink-fit chucks are very well established in practice because they can apply very high holding forces with little effort. In addition, they provide the possibility of holding the clamped tool with a high degree of flexural rigidity in such a way that the tool is precisely guided and produces highly accurate geometry on the workpiece during the cutting operation. At the same time, however, they frequently clamp the tool shank in a very rigid or hard manner, as a result of which vibration problems gain in significance.
The quality of the clamping of a shank tool is of great importance for the machining quality to be achieved by the tool and frequently also for the tool life.
That is all the more true of high-speed cutting of metals, in particular at a cutting speed of more than 800 m/min or even more than 1100 m/min.
The quality of the clamping also depends, inter alia, on how well vibrations which may occur can be damped. A substantial source of such vibrations can be, for example, the rapid change in the number of milling cutting edges currently in engagement in a chip-removing manner with the workpiece. They may result, for example, in considerably adverse torsional vibrations.
Other vibrations that are, however, likewise damaging can result from the tendency of a shank tool, and in particular of an end milling cutter, to roll during operation. Rolling is understood as meaning the slight elastic deformation of the shank that recurs with each revolution and changes locally in the course of the revolution due to contact with the workpiece under the load of the feed.
It is accordingly an object of the invention to provide a shrink-fit tool-clamping chuck with novel damping, a method of using the chuck and a tool-clamping system, which overcome the hereinafore-mentioned disadvantages of the heretofore-known chucks, methods and systems of this general type and which can apply large clamping forces and at the same time can deal better with vibrations which occur.
With the foregoing and other objects in view there is provided, in accordance with the invention, a tool-clamping chuck for clamping tools having a tool shank, including a sleeve portion which is open at its free end and is composed of preferably electrically conductive material. The sleeve portion forms a tool-holding fixture for the frictionally locking fixing of the tool shank in a press fit by shrink-fitting. According to the invention, the tool-clamping chuck is distinguished not least in that the sleeve portion—preferably at any rate over the entire axial length of the tool-holding fixture—is formed of an inner sleeve and an outer sleeve which receives the latter in the operationally ready state, is joined thereto without play, and which is preferably likewise composed of an electrically conductive material.
This configuration results in a considerable reduction in the tendency of the tool-clamping chuck for damaging vibrations.
The boundary layer at which the inner sleeve and the outer sleeve are in contact with each other in the region of the tool-holding fixture appears to be responsible for this. Not least, if metal strikes against metal, damping occurs or there is a reduced capability of transmitting vibrations. This appears not least to apply whenever the inner sleeve and the outer sleeve are in non-releasable contact with each other during normal operation, for example are pressed together, in particular because they are already pressed together prior to the clamping of a tool shank and the associated prevention of expansion, and the pressing together thereof is increased further by the clamping of the tool shank.
Furthermore, the outer sleeve can then moreover be supported axially on the clamping chuck basic body, which can be realized, for example, by using a fastening flange on the outer sleeve and a complementary annular shoulder on the clamping chuck basic body. That is to say, the fastening flange or the outer sleeve is supported axially on the clamping chuck basic body.
This configuration also contributes to a significant reduction in the tendency of the tool-clamping chuck for damaging vibrations.
The above description of advantageous refinements of the invention includes numerous features that are presented in some cases collectively in combination in the individual dependent claims. Those features may however expediently also be considered individually and combined to form further meaningful combinations.
Even though some terms are used in each case in the singular or in conjunction with a numeral in the description and/or in the patent claims, it is not the intention for the scope of the invention to be restricted to the singular or the respective numeral for those terms. Furthermore, the words “a” or “an” are to be understood not as numerals but as indefinite articles.
The characteristics, features and advantages of the invention described above, and the manner in which these are achieved, will become clearer and more comprehensible in conjunction with the following description of the exemplary embodiments of the invention that will be explained in more detail in conjunction with the drawing(s)/figure(s) (identical components and functions have the same reference signs in the drawings/figures).
The exemplary embodiments serve to explain the invention and do not restrict the invention to combinations of features indicated therein, not even with respect to functional features. In addition, features suitable for this purpose of any exemplary embodiment can also be considered explicitly in isolated form, can be removed from one exemplary embodiment, introduced into another exemplary embodiment to supplement the latter and/or can be combined with any of the claims.
Referring now to the figures of the drawings in detail and first, particularly, to
At its end facing away from the coupling, the tool-clamping chuck 1 forms a sleeve portion 4. A tool-holding fixture 5 which holds the shank of the tool is implemented inside the sleeve portion. In the axial direction behind the tool shank, the sleeve portion forms an outlet region 6 which is not used by the tool shank or for holding of the latter. Coolant can be introduced through the outlet region, this being stated with reference to the further figures where this is partially disclosed.
This sleeve portion 4 is constructed in such a manner and used in such a way that it can hold a tool shank in a press fit in such a way that the tool shank neither rotates nor is pulled out or slips in the axial direction, at any rate substantially, in relation to the tool holder during work with the tool. The details of the shrinking process and of the corresponding construction of the tool-clamping chuck are described in German Patent Application DE 199 15 412 A1, corresponding to U.S. Pat. Nos. 6,712,367 and 6,991,411, which are hereby fully incorporated in the subject matter of this disclosure and the features of which may therefore possibly be relied on to restrict the current claims.
The tool-clamping chuck 1 according to the invention differs therefrom in respect of its sleeve portion 4 in that the sleeve portion 4 is constructed in two layers, at any rate along the axial region in which it forms the tool-holding fixture 5, and often even furthermore beyond the region of the outlet 6, as can be seen herein in
It is constructed in two layers by including an inner sleeve 7 and an outer sleeve 8. The two sleeves for their part are preferably composed of metal or steel, but preferably of different types of steel.
In one embodiment, the clamping chuck basic body 2 can be composed of different materials. Thus, the end 3 can be composed, for example, of steel, and the inner sleeve 7, which is constructed on the end 3, for example by an additive process, can be composed of a different material, e.g. aluminum.
The inner sleeve 7 and the outer sleeve 8 are connected to each other without play. This freedom from play generally also exists whenever the tool-clamping chuck 1 is still not clamping a shank, but rather is waiting unused at room temperature for its next use.
Not always, but generally and therefore particularly advantageously, the inner sleeve 7 and the outer sleeve 8 are connected to each other by a press fit. They are thereby particularly intimately in contact, with high, vibration-damping friction. The press fit can come about by the inner sleeve 7 having a conical outer circumferential surface, at least along most of the axial length of the tool-holding fixture 5.
The outer sleeve 8 then has a correspondingly conical inner circumferential surface which is complementary with respect thereto.
The outer sleeve 8 is pushed or pressed in the axial direction onto the inner sleeve 7. This can take place by using a shrinking operation and/or preferably by the further configuration shown in
In the present case, the annular shoulder 28 bears, at an appropriate location, blind holes which are provided with an internal thread. In this way, by tightening clamping screws 10, axial pressing between the conical surfaces of the inner sleeve 7 and the outer sleeve 8 can be achieved.
In this connection,
The centering section 8a, which has already been discussed, will now be discussed once again. The inner sleeve 7 or the clamping chuck basic body 2 assigned thereto likewise has a complementary centering section 7a. The structure with regard to the centering sections is selected in such a manner that the outer sleeve 8, when pushed onto the inner sleeve 7, comes to lie there with its centering section 8a on the assigned centering section 7a, even before the pressing between the inner sleeve and the outer sleeve begins. This quite considerably facilitates the pressing with the aid of the screws already discussed.
It is also notable that it has proven particularly advantageous if a transition section 12 is provided between the centering section and the actual sleeve portion, as can readily be seen in
In this transition section 12, the outer sleeve 8 and the inner sleeve 7 are not in contact, even though they are completely fitted and ready for use. Advantageously, the same applies correspondingly to a region which is in the vicinity of the flange 9 and which is identified by reference sign 13 in
Further interesting details emerge from
This exemplary embodiment is distinguished in that it is equipped with tool cooling.
For this purpose, cooling lubricant is typically introduced from the machine tool through the coupling, which is constructed in this way as an HSK coupling, into the interior of the tool-clamping chuck. In the present case, the introduction advantageously takes place into the outlet region 6.
In this exemplary embodiment, the outlet region 6 is connected to at least one further cooling duct by radially outwardly running bores 14, or at least one individual bore of this type. This further cooling duct is formed by the fact that, for example, in the outer sleeve 8, at least one coolant groove 15 running substantially in the axial direction is formed, as
A sealing ring or an O-ring 20 is provided between the outer surface of the inner sleeve and the inner surface of the outer sleeve, specifically in such a manner that it is placed in an annular groove 27 provided in the outer surface of the inner sleeve, so that the coolant does not penetrate further inward between the inner sleeve and outer sleeve.
Instead of the conical pressing between the inner sleeve 7 and the outer sleeve 8, pressing as shown in
Further features also emerge from the other figures which are attached, that is
An interesting variant which can be seen, for example, in
Furthermore,
The variant according to
As is also shown, for example, in
A further interesting variation which is shown in
Another interesting variation which is shown in
For the sake of completeness, it should be stated that all of the features shown in the figures may be important to the invention individually or in combination, or may be at least beneficial for the invention and should therefore also be claimed at the given time.
The inner sleeve and the outer sleeve, due to their corresponding structure, can preferably both act actively (and not only transmitting/forwarding an externally generated radial pressure) in producing the press fit, as referred to at various locations within the scope of this disclosure. In some cases, the outer sleeve predominantly or substantially takes on the active production of the press fit.
By way of general significance, it is stated that protection may also be claimed for the following structure at a given time:
The tool holder basic body forms an inner sleeve 7, which is fixed thereto in one piece and preferably formed integrally or cast integrally therewith, and an outer sleeve 8 which is pushed thereon, is produced physically separately therefrom and which applies the entire, the substantially entire or the predominant part or optionally and advantageously at least 85% or 70% or 60% of the pressing force holding the tool shank.
In other words, protection can also be claimed for a construction in which no longer the tool holder basic body or clamping chuck basic body as such, but rather for the first time a shrink-fitting body, which is pushed thereon but is separate, produces the thermally generated shrink-fitting pressure, to the above-mentioned extent. In an extreme exception (but also claimed if needed), even with simple interposition of a sleeve which is then only passive and is not substantially involved in the active production of the shrink-fitting pressure and which may then be the inner sleeve, and a damping interposition between the tool shank and the outer sleeve generating a press fit for the latter.
For all of the variants, a crucial optional criterion from the aspect of damping may be that the outer sleeve and the inner sleeve are connected to each other substantially only in a frictionally locking and not form-locking manner (at any rate as seen in the circumferential direction).
This particular claim disclosure can advantageously be combined with others of the claims presented herein and/or parts thereof and/or with fragments of the description or features of the figures.
The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.
Number | Date | Country | Kind |
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10 2021 119 935.2 | Jul 2021 | DE | national |