Pre-stressing damping system

Abstract

A tool holder having a tool receptacle for chucking a tool shaft by frictional engagement, in which the tool receptacle comprises a plurality of annular clamping surfaces spaced apart from one another, which are intended for retaining the tool shaft by nonpositive engagement and are embodied on the inner circumference of a tube part, and the tube part has a recess in the material for varying its clamping action; the recess in the material is embodied by a plurality of annular channels extending in the circumferential direction, which are each separated from the tool receptacle by a resilient wall portion, which on its side facing away from the channel embodies the respective clamping surface.

Claims

1. A tool holder having a tool receptacle for chucking a tool shaft by frictional engagement, the tool receptacle comprising: a plurality of annular clamping surfaces spaced apart from one another, which are intended for retaining the tool shaft by nonpositive engagement and are embodied on an inner circumference of a tube part, and the tube part has a recess in a material for varying its clamping action, and the recess in the material is embodied by a plurality of annular channels extending in a circumferential direction, which are each separated from the tool receptacle by a resilient wall portion, which on its side facing away from a respective channel embodies a respective clamping surface, wherein a depth of each channel, measured in a radial direction, is <0.1 mm, and with increasing load, the resilient wall portion braces itself on a tube part located behind the resilient wall.

2. The tool holder of claim 1, wherein the resilient wall portion is thin-walled in the radial direction and has a wall thickness <2 mm, and in addition a width of the channel that is spanned by the resilient wall portion, which separates the channel from the tool receptacle, is greater, by at least 25%, than a width of the clamping surface that is embodied on the resilient wall portion, in each case viewed in a direction of a longitudinal axis of the tool holder.

3. The tool holder of claim 2, wherein the width of the respective channel, measured in a direction of an axis of rotation, is greater by a factor of at least 10 than the depth of the channel measured in the radial direction.

4. The tool holder of claim I, wherein the depth of each channel, measured in the radial direction is <0.075 mm.

5. The tool holder of claim 1, wherein the tube part is embodied in two parts and comprises one tubular portion and a bush fixed in the tubular portion, and one or more grooves that definitively form the channels are machined in an outer circumferential surface of the bush.

6. The tool holder of claim 5, wherein the channels are filled with a substance selected from the group consisting of: a nonferrous metal, copper, a nonmetal, plastic, a fluid, and oil.

7. The tool holder of claim 5, wherein the bush is produced from a high-damping metal.

8. The tool holder of claim 5, wherein the bush, on its face end toward a free end of the tool holder, is welded to the tool holder, and the bush is thin-walled and has a wall thickness <2.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an overview of the first exemplary embodiment.

(2) FIG. 2 shows a section through the tube part of the first exemplary embodiment.

(3) FIG. 3 shows a detail of FIG. 2.

(4) FIG. 4 shows an overview of the second exemplary embodiment.

(5) FIG. 5 shows a section through the tube part of the second exemplary embodiment.

(6) FIG. 6 shows a detail of FIG. 5.

(7) FIG. 7 shows a section along the axis of rotation through a collet, which represents a third exemplary embodiment of the invention and which is distinguished by the channels machined integrally into it.

(8) FIG. 8 shows a view of the collet of FIG. 7 from the front.

(9) FIG. 9 shows a front view of a collet which represents a fourth exemplary embodiment; this is a collet with a bush thrust into it.

(10) FIG. 10 shows a vertically extending section through the collet of FIG. 9.

(11) FIG. 11 shows the collet of FIG. 9 in a different position.

(12) FIG. 12 shows a vertically extending section through the collet of FIG. 11.

(13) FIG. 13 shows an enlarged detail of the tube part that can be seen in FIGS. 10 and 12.

(14) FIG. 14 shows a front view of a collet, which represents a fifth exemplary embodiment of the invention; this is a collet with an inserted bush of a different design.

(15) FIG. 15 shows a vertically extending section through the collet of FIG. 14.

(16) FIG. 16 shows the collet of FIG. 14 in a different position.

(17) FIG. 17 shows a vertically extending section through the collet of FIG. 16.

(18) FIG. 18 shows an enlarged detail of the tube part that can be seen in FIGS. 14 and 16.

(19) FIG. 19 shows a very greatly enlarged detail of the bush of the invention; this detail is preferably representative of all the bushes described in the exemplary embodiments, including the bushes that are shown in FIGS. 20 and 21.

(20) FIG. 20 shows the axial section through a milling cutter that is equipped with the bush of the invention.

(21) FIG. 21 shows a side view of the milling cutter of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(22) FIG. 1 shows a tool holder 1 in the form of a shrink-fit chuck. The reference symbol L designates the axis of rotation of the tool holder about which the tool holder rotates when being used as intended.

(23) Shrink-fit chucks are capable of chucking the shafts of tools in especially hard fashion, depending on the structural type. In many cases this is advantageous, but in all those cases in which a softer chucking is opportune, the shrink-fit chucks are especially predestined for the use of the invention.

(24) As can be seen best from FIGS. 2 and 3, this tool holder 1 has a tool receptacle 3 in the interior of its tube part 4.

(25) The tube part 4 in this exemplary embodiment is not embodied in one piece; instead, it comprises the tubular portion 5, usually embodied as an integral component of the tool holder 1, and the bush 6 retained in this tubular portion 5.

(26) As a rule, this bush 6 is inseparably joined to the tubular portion 5, for instance by a weld seam, not shown in the drawings, which connects the free face end of the bush 6 to the face end of the tubular portion 5.

(27) The bush 6 is provided on its outer circumference with a plurality of first annular grooves 7, preferably continuous in the circumferential direction, which are each separated from one another by an annular land 8. The annular grooves are self-contained. As soon as the bush 6 is mounted as intended in the tubular portion 5, the bush 6 and the tubular portion 5 together form a tube part 4, which has a recess in the material in the form of a plurality of corresponding annular channels 9. See particularly FIG. 3. It shows that the annular channels 9 formed definitively by the first annular grooves 7 are each separated from the actual tool receptacle by a wall portion 10 that yields resiliently in the radial direction. This wall portion closes the annular channels 9 off from the tool receptacle, so that there is no direct connection between the annular channels 9 and the circumferential surface of the tool shaft to be chucked; instead, there is a separation by the aforementioned wall portion 10.

(28) Because the wall portions 10 are yielding in the radial direction, the tool shaft is more softly chucked. Unlike channels or bores that extend for instance essentially in the direction parallel to the axis of rotation L in the tube part, the uninterrupted, circumferentially extending annular channels 9 ensure that the rigidity with which the tool shaft is chucked relative to the forces exerted on it in operation is identical in all directions and therefore not dependent on the rotary position at the time of the tool holder. According to the invention, this provides for especially quiet operation.

(29) In this exemplary embodiment, it is especially favorable that the inner circumferential surface of the bush 6 is not a continuously uniform cylindrical jacket face. Instead, on its inner circumferential surface, the bush 6 also bears annular grooves in the form of the second annular grooves 11. Between them, they form annular clamping surfaces 12, which as intended rest against the circumference of the tool shaft. They fix the tool shaft by nonpositive engagement and thus transmit at least the predominant portion of the torque, to be exerted in operation, to the tool shaft.

(30) Preferably, the clamping surfaces 12 are positioned and designed in a defined manner, namely as shown also in FIG. 3, but see also FIG. 19.

(31) The clamping surfaces 12 are each embodied on the inner circumference of a resiliently yielding wall portion 10. The applicable clamping surface 12 is thus entirely surrounded in the circumferential direction by a cavity in the form of the channel 9, and thus is hollow and is therefore capable of escaping or moving elastically resiliently in the radial direction.

(32) The various dimensions that are relevant to the channels of the invention and the bush of the invention can be best explained in conjunction with FIG. 19:

(33) Preferably, the width BS, measured parallel to the axis of rotation L, of each of the clamping surfaces 12 is less than the width B1, measured in the same direction, of the respective channel 9 formed by a first groove 7, which channel spans the elastic wall portion 10.

(34) As can be seen, the bush is embodied in thin-walled fashion; its wall thickness W is preferably less than 2.5 mm and even better less than 1 mm.

(35) It is especially favorable for each of the channels 9, or at least the predominant number of the channels, to be embodied such that the width B1 of the applicable channel 9 is substantially greater than the depth T1 measured in the radial direction. In such an embodiment, the resiliently yielding wall portion 10 can as needed be compressed until it is virtually a block; that is, whenever in operation, for whatever reason, especially strong forces must be exerted suddenly, the resiliently yielding wall portion 10 can be braced in the radially outward direction. This prevents the chucking of the tool shaft from becoming too soft to be capable of withstanding all the loads occurring in operation.

(36) As best seen in conjunction with FIG. 2, the tool holder adjoining the bush 6 is preferably provided with the safelock thread structure 13 already mentioned above.

(37) FIG. 4 shows a further tool holder 1 in the form of a shrink-fit chuck. The base body of this tool holder is equivalent to the tool holder shown in FIG. 1. In this exemplary embodiment as well, the tube part 4 is not embodied in one piece.

(38) In a distinction from the first exemplary embodiment just described, the tool holder here is equipped with a bush that, with the first grooves mounted on its outer circumference, does not form a plurality of channels, each self-contained in the circumferential direction, but instead two continuous channels 9 extending uninterruptedly, which each wind more than three times around the tool receptacle opening, each along its own helical line. Here, the channels 9 thus form an arrangement that can be called a two-course thread.

(39) In this embodiment as well, the annular channels 9 are each separated from the actual tool receptacle by a wall portion 10 that yields resiliently in the radial direction and closes off the annular channels 9 from the tool receptacle.

(40) Here again, the resiliently yielding wall portion bears the actual clamping surface 12, so that once again the clamping surface is hollow. Thus in this exemplary embodiment, there are two clamping surfaces, which here, however, in contrast to the first exemplary embodiment, are not embodied in the form of a plurality of circular rings, but in the form of two helical lines, which are arranged in the manner of a two-course thread and likewise wind several times around the axis of rotation L of the tool holder.

(41) Preferably, in this exemplary embodiment as well, the width BS, measured parallel to the axis of rotation L, of each of the clamping surfaces 12 is less than the width B1, measured in the same direction, of the channel 9 that spans the wall portion 10; again, see FIG. 19 that is representative for this exemplary embodiment as well.

(42) Because of the provisions just described, the chucking of the tool shaft is softer, in this exemplary embodiment as well.

(43) With regard to the dimensioning of the channels 9 or (when a bush is used) of the first and second grooves 7, 11 and of the clamping surfaces 12 as well as the wall thickness W of the bush 6, what is said above for the first exemplary embodiment logically applies to the second exemplary embodiment as well.

(44) FIGS. 7 and 8 show a third exemplary embodiment of the invention, which, however, is used here not to vary the chucking characteristic of a shrink-fit chuck but rather to vary the chucking characteristic of a collet 15. This collet is press-fitted by a cap nut in the direction of the axis of rotation L into a conical seat engaging its outer circumference and thus keeps the tool shaft in a force fit.

(45) Advantageously, here again the collet is equipped with the safelock thread structure 13 already mentioned above.

(46) The channels 9 of the invention, in this exemplary embodiment, are embodied in the form of a plurality of circular-annular channels extending in the circumferential direction, whichas in the first exemplary embodimentare closed off toward the side of the tool receptacle by resiliently yielding wall portions 10. The channels are cut into by the slits 14, extending through the wall of the collet 15 and lending it the requisite compressibility, but otherwise are self-contained. Unless the ensuing explanation of the special features of this exemplary embodiment says otherwise, the channels 9, the resiliently yielding wall portions 10, and the clamping surfaces 12 are preferably embodied, located and dimensioned as described above for the first exemplary embodiment; see again FIG. 19, whose illustration applies here accordingly.

(47) The special feature of this exemplary embodiment is that the channels of the invention are not produced here with the aid of a bush that is thrust into the collet and fixed there, but instead that the channels are embodied integrally in the one-piece collet.

(48) Such an embodiment of the channels can be accomplished more simply by producing the collet using a powder metallurgical method.

(49) FIGS. 9 through 13 show a fourth exemplary embodiment of the invention. In this exemplary embodiment as well, the invention is used to vary the chucking characteristic of a collet 15.

(50) However, this exemplary embodiment is closely related to the first exemplary embodiment, because here again, the channels 9 of the invention are produced in such a way that the bush 6, already described in detail in conjunction with the first exemplary embodiment, and which on its outer circumference bears first grooves 7, is inserted into a collet 15 instead of into a shrink-fit chuck. As in the first exemplary embodiment, the bush is self-contained in the circumferential direction, and thus has no lengthwise slit.

(51) For the location, embodiment and dimensioning of the channels, the resilient wall portions, and the clamping surfaces, what is said for the first exemplary embodiment is also applicable.

(52) Here, the thin-walled nature of the bush 6 already described above has an especially favorable effect, which ensures that the retention force of the collet is not significantly reduced, even though the bush 6 has no longitudinal slit.

(53) FIGS. 14 through 18 show a fifth exemplary embodiment of the invention.

(54) This exemplary embodiment is closely related to the second exemplary embodiment, because the channels 9 of the invention are produced here in such a way that the bush 6, already described in detail in conjunction with the second exemplary embodiment, is inserted into a collet 15 instead of into a shrink-fit chuck. For the location, embodiment and dimensioning of the channels, the resilient wall portions, and the clamping surfaces, what is said for the second exemplary embodiment therefore applies as well.

(55) Here again, the thin-walled nature of the bush 6 has a favorable effect.

(56) FIGS. 20 and 21 show that the invention can easily also be put to use retroactively, without having to make changes in the tool holders.

(57) For that purpose, the bushes 6 already used in the context of the exemplary embodiments described above are used, which are preferably also designed as already described above, and in particular regarding the design of the grooves 7 and 11, the resilient wall portions 10, and the clamping surfaces 12. The bushes 6 can have a plurality of circumferentially extending grooves 7 and 11 on the outside and optionally on the inside, respectively, or instead can have the spiral groove or grooves also described above.

(58) Expediently, such a bush 6 is fixed on the tool shaft 17 permanently by shrink-fitting and/or local welding.

(59) The bush 6 here is dimensioned such that after the fixation it has a maximum outside diameter that is at least essentially or preferably entirely equivalent to one of the current rated diameters for tool shafts to be chucked in tool holders, so that the tool provided with the bush can be routinely chucked into one of the standard tool holders.

(60) To achieve this, the tool shaft, on its end remote from the tool cutting edges, can have a portion of reduced diameter, so that a bush whose maximum outside diameter is equivalent to the actual shaft diameter of this tool can be thrust onto the tool shaft.

(61) Alternatively, the bush is thrust onto the tool shaft the diameter of which is not reduced and is then dimensioned such that its maximum outside diameter, after the fixation, is equivalent to the rated shaft diameter of a larger tool, so that the tool together with the bush can be inserted into the standard tool holder actually intended for this larger tool, without having to make changes to the tool holder.

(62) In general it should be noted, as an example in terms of the bush shown in FIG. 19 but applying to all the exemplary embodiments, that by suitable design of the bush, the vibration and damping behavior can be varied and adapted. This can happen above all by means of the positioning and dimensioning of the annular grooves 7 and 11.

(63) In FIG. 19, the grooves are made such that a clamping surface 12 is created that is located entirely above the groove 7. By changing the width and depth of the grooves 7 and 11, the rigidity of the bush can be varied. The narrower the clamping surface 12 becomes, and the more the clamping surface 12 is positioned only in the area of the middle of a groove 7, the softer clamping becomes. Conversely, the clamping can become harder if the clamping surface 12 is so wide that it fits all the way over the groove 7 and goes beyond the groove at the edges and is not hollow there.

(64) The grooves 7 and 11 can furthermore overlap one another in such a way that the clamping surface 12 is braced on two adjacent grooves 7. As a result, a relatively soft and resilient clamping can be achieved, in any case whenever the two adjacent grooves are very close together.