Prior Art Within the field of ch p removing machining there are tool couplings of the general kind defined above in several different applications, however, usually in turning tools of different type. Thus under the trade name COROMANT CAPTE0 (Manufacturer: Sandvik AB, Sweden) boring bars are marketed, said boring bars having such couplings. The holder constitutes for instance a bar for a cutting head mountable in a multi- purpose lathe, said cutting head having one or more machining elements in the shape of exchangeable inserts. In connection with previously known boring bars of this kind a first ser- ration is provided at an essentially planar inner end surface of the cutting head, while a co-operating second serration is provided at an external or free end surface of the bar. In order to bring the serrations into engagement with each other several loose screws are used as clamping means, said screws having heads and being tightened in axial threaded holes that open in the serrated surface at the free end of the bar. More precisely, in this end surface four equidistant separated holes are recessed, of which the two upper permanently receive screws that are inserted through holes in the cutting head and the two lower may receive a screw that is located in one or the other of the threaded holes depending on if the cutting head in question is of a left-hand type or a right-hand type.

By the presence of the above-mentioned serrations in the two end surfaces of the bar and the cutting head respectively, said serrations being urged against each other, a very reli-

able, torque resistant connection is achieved between the bar and the cutting head. This in turn guarantees that the active insert is given and maintains a correct position. However, a disadvantage in connection with the previously known tool cou- pling is that the exchange of the cutting head is complicated and time-consuming. Thus, not less than three screws must ini- tially be loosened and then again tightened to complete a tool exchange; what might take several minutes. The tool exchanges become especially difficult in such cases when the screws are hard to reach and/or have chips, dirt, grease deposits or the like in their key recesses. Under such circumstances the ope- rational shutdowns for tool exchanges may be very time-consu- ming and expensive. Further, there is a risk that screws are lost since they must be loosened completely in order to allow dismounting of the cutting head.

Tool couplings using co-operating serrations in combina- tion with screws as clamping means are further known from WO 93-10929 and BE 3 026 513. Even if the number of screws for fastening the adapter to the holder in these cases are reduced to one and two respectively, the operation to initially loosen a comparatively long screw and then again tighten said screw, after a tool exchange has been effected, results in that the exchange takes comparatively long time. Also in this case the screws may be lost.

Objects and Features of the Invention The present invention aims at removing the shortcomings mentioned above in connection with previously known tool coup- lings of the type in question and at providing an improved coupling. Thus, a primary object of the invention is to create a tool coupling by means of which the necessary tool exchanges are effected in a quick and simple way. A further object is to create a tool coupling that makes it possible to design one and the same holder in such a way that it may be used in a flexible way not only for co-operation with different types of adapters, but also for positioning adapters in several diffe- rent positions. Still a further object of the invention is to create a tool coupling where there is no risk of losing said clamping means.

According to the invention at least the primary object is attained by means of the features defined in the characte- rizing part of claim 1. Preferred embodiments are furthermore defined in the dependent claims.

Further Elucidation of Prior Art In an especially preferred embodiment defined in claim 3 the present invention uses a clamping mechanism that is previ- ously known from SE 8502263-0 (publication number 447 712).

However, this known tool coupling includes no serrations at all and especially there is no holder having several serra- tions that may cooperate with different adapters or adapters positioned in different ways.

Brief Description of the Drawings In the drawings: Figure 1 is a perspective exploded view showing a tool coup- ling comprising a holder and an adapter in the shape of a cutting head, said holder as well as the adapter being schematically illustrated, Figure 2 is a partial longitudinal section through the tool coupling in a condition where the adapter is connec- ted with the holder, Figure 3 is a cross-section along A-A in figure 2, Figure 4 is a partial, enlarged cross-section showing a pre- ferred geometrical shape of an individual serration, Figure 5 is a perspective exploded view illustrating how a separate spacing body may be incorporated in the tool coupling, Figure 6 is a perspective exploded view showing a second, alternative embodiment of the holder of the coupling, and Figure 7 is a similar exploded view showing a further, deve- loped embodiment of the holder.

Detailed Description of Preferred Embodiments of the Invention In figures 1-3 reference numeral 1 designates a holder and reference numeral 2 designates an adapter. The holder 1,

in practice called a basic holder, includes a rear portion 3 that is intended to be connected to a machine tool, for instance a multi-purpose lathe, and a forward portion 4, to which the adapter 2 is to be connected. The adapter in turn is constituted by a cutting head having at least one seat 5 for receiving a cutting insert or a machining element (not shown) for chip removing machining. At a rear end surface of this cutting head (hidden in figure 1) a first serration 6 is pro- vided (see also figure 2). A corresponding serration 7 is pro- vided at a forward end surface of the essentially cylindrical holder 1. This forward end surface extends perpendicular to the central longitudinal axis of the holder.

So far described the disclosed tool coupling is in all essentials previously known on one hand from commercially available couplings of the type COROMANT CAPTOO and on the other hand from WO 93-10929 and BE 3 026 513 respectively.

In accordance with the present invention a first hole 8 is recessed in the holder 1, said hole 8 opening in the serra- tion 7, and a second hole 9 is recessed in the holder 1, said second hole 9 extending transverse to said first hole 8. Pre- ferably the second hole extends at a right angle to the first hole. In the second hole 9 a clamping mechanism of quick coup- ling type is accommodated, the features of said clamping mechanism being described more in detail with reference to figures 2 and 3. Said clamping mechanism is generally desig- nated by reference numeral 10.

A pulling member, generally designated by reference numeral 11, projects from the serration 6 at the rear side of the adapter, said pulling member being intended to be inserted into the hole 8, more precisely in order to co-operate with the clamping mechanism 10. Although it is feasible to design the pulling member 11 as an integral part of the adapter itself, it is preferred to manufacture the same in the shape of a separate body that is connected with the frame of the adapter, for instance via a thread coupling. Thus in figure 2 it is indicated how the essentially plug-shaped pulling member in the area of one of its ends has an external thread that is tightened in an internal thread in a central hole in the adap- ter, this providing a thread coupling 12. In the area of its

opposite end the pulling member is provided with two shank- like portions 13,13'that are separated by a slot 14. Each one of these shank-like portions has upper and lower sets of serrated projections 15 that are defined by wedge surfaces 16 that are inclined relative to the axial extension of the plug.

The clamping mechanism 10 comprises in a known way (see SE 8502263-0) a screw 17 having axially separated, external threads 18,18'of reverse type, i. e. one is a left-hand thread and the other one is a right-hand thread. These threads are in engagement with internal threads in holes in two nut bodies 19,19'that are axially moveable to and fro in the through-going hole 9 in the holder. As is evident from figure 3 the intermediate, an unthreaded portion 17'of the screw 17 is located between the two shanks 13,13'of the pulling mem- ber 11, said unthreaded portion 17'extending between the two threaded portions 18,18'. The two sides of the nut bodies 19, 19'facing each other are provided with serrated projections 20 that are analogous with the serrated projections 15 in the sense respect that each one has two inclined wedge surfaces 21. Since one of the two threads 18,18'of the screw 17 is a right-hand type thread and the other one is a left-hand type thread, the two nut bodies 19,19'will approach each other when the screw is rotated in one direction and are distanced from each other when the screw is rotated in the opposite direction. In order to enable rotation of the screw, key recesses 22 (for instance of the Allen key type) are provided in each of the two opposite ends of the screw. This means that the screw may be rotated by means of a key that can be applied to an arbitrary end of the screw. This may in practice facili- tate the operation of the screw when the holder is mounted in a narrow space where only one side of the holder is access- ible.

From figure 3 is evident how each nut body 19,19'is guided by means of a pin 23 that engages an axial groove 24 in the body. The pin 23 allows the nut body to move axially at the same time as a rotation of the same is prevented when the screw is rotated. In this connection it should be pointed out that special sealings (not shown) may be arranged between the outer side of the individual nut body and the inner side of

the hole 9, more precisely in order to prevent liquid leakage from the central, axial hole 8. In such a way the last-men- tioned hole may be used for feeding cooling liquid to the cut- ting head.

Reference is now made to figure 4 that illustrates a preferred embodiment of the individual serration 6,7. This serration comprises several oblong ridges or beads 25 which are parallel relative to each other and separated by grooves 26. The top of the individual bead 25 is upset, preferably by having a planar surface 27 of a considerable width. Each groove 26 is essentially V-shaped in cross section by being defined by two inclined flank surfaces 28,28'and a rounded bottom 29. The angle v° between the flank surfaces 28,28'is acute and should be within the interval 45-75°. In the dis- closed example the angle v = 60 «. The height of the ridges should in practice be within the area 0,3-1,0, preferably 0,5- 0,75 mm. When the ridges of one of the serrations engage the grooves of the other serration the tops of the ridges should not contact the bottom of the grooves in order to guarantee that the respective ridges are effectively wedged into the adherent grooves. As is evident from figure 1 the serration 7 extends over the entire annular surface that is defined bet- ween the central hole 8 and the periphery of the cylindrical holder portion 4. In a corresponding way the serration 6 extends over the entire surface that is defined between the central pulling plug 11 and the cylindrical envelope surface of the cutting head 2.

When the cutting head 2 is to be connected with the holder 1 the clamping mechanism 10 is initially so adjusted that the pulling plug 11 may be received. This is effected by having the screw 17 rotating in the direction that makes the nut bodies 19,19'spacing from each other a suitable dis- tance. In the next step the pulling plug 11 is inserted into the hole 8 and pushed to an inner end position where the two shank portions 13,13'are located on both sides of the middle portion 17'of the screw simultaneously as the serrated pro- jections 20 of the nut bodies are at least approximately loca- ted in the area between two corresponding serrated projections 15 of the shank portions 13,13'. In this condition the screw

is rotated in the opposite direction and the nut bodies are approaching each other. In doing so, the inwardly facing wedge or flank surfaces 16 of the serrated projections 15 will abut analogous, outwardly facing wedge or flank surfaces 21 of the serrated projections 20 in order to urge, by edge action, the pulling plug 11 in a direction into the hole when the nut bodies are further tightened against each other. This in turn makes the ridges of the serration 6 to be urged into the grooves of the serration 7 and to be wedged therebetween by a large force. Between the cutting head and the holder a torque resistant connection is achieved, said connection having a high reliability.

When the cutting head is to be removed from the holder in connection with a tool exchange the nut bodies 19,19'are distanced from each other and then the cutting head may be removed from the holder.

Apart from providing a robust and reliable connection between the cutting head and the holder the tool coupling according to the invention has the advantage that the clamping mechanism always follows the holder without having to be remo- ved from the same, as is the case with detachable screws.

Thus, the nut bodies 19,19'are permanently maintained in the transverse hole 9 and they can only be moved to the outer end positions that are defined by the pins 23. Another advantage is that the screw 17, included in the clamping mechanism, and the key recesses 22 in the screw 17 are located at a consider- able distance from the cutting insert of the cutting head. In practice this means that chips that are loosened by the cut- ting insert do not tend to get stuck in the key recesses and complicate the screwing.

Reference is now being made to figure 5 showing how a certain spacing body 30, if needed, may be applied between the holder 1 and the cutting head 2. This spacing body may be cylindrical or tubular and has at opposite ends serrations of which a first one 6'surrounds a pulling member 11'while the other one 7'surrounds a first hole 8'in the spacing body.

Analogous to the previous embodiment the spacing body includes a transverse hole 9'in which a clamping mechanism 10', of the same design as previously described, is accomodated. From

figure 5 it should be evident that the spacing body 30 may be connected with the holder 1 by means of the pulling member 11' and the clamping mechanism 10 accomodated in the holder, and that the cutting head 2 is allowed to be connected with the spacing body by means of the pulling member 11 and the clam- ping mechanism 10'accomodated in the spacing body. With the help of this spacing body the cutting head 2 and the associa- ted cutting insert may be located at a considerable distance from the basic holder. This distance is of course defined by the length of the spacing body.

In figure 6 an embodiment is illustrated where the holder 1 comprises two opposite serrations 7A, 7B, more pre- cisely serrations that are provided on opposite sides of the holder. In the disclosed example the two serrated surfaces are parallel to each other, although it is also feasible to locate them at an angle relative to each other, for instance diver- ging in a direction rearwards from the forward front surface.

In this case the adapter 2'constitutes a blade or disc shaped frame--having a seat 5'for an insert of the kind used for e. g. parting operations. Said frame has, on one side, a serration 6, from which a pulling member 11, of the kind previously described, projects. The pulling member 11 may be received in hole 8 that opens in the serration 7A and extends to the transverse hole 9 of the clamping mechanism 10. In an analo- gous way a hole (non-visible) extends from the serration 7B to the transverse hole 9. In other words the hole 9 is common for the two holes 8 that open in the serrated surfaces 7A, 7B and thus the same clamping mechanism 10 may be used for fastening of an adapter regardless if the adapter is applied on one side or the other of the holder.

In figure 7 an especially preferred embodiment of the invention is illustrated where the holder 1, apart from the serrations 7A, 7B on opposite sides, also has a third serra- tion 7C at the front surface of the holder. In this embodiment the adapters may, for instance any one of the adapters 2,2' that are exemplified in the drawing, be applied to the holder in one of the three different positions. This means that the holder forms a universal basic holder having flexible applica- tion possibilities.

Feasible Modifications of the Invention The invention is not solely restricted to the embodi- ments described and disclosed in the drawings. Thus it is possible to apply the invention in connection with both hol- ders as well as adapters of a different physical shape than the ones exemplified. It is also feasible to use other types of clamping mechanisms than the one exemplified in figures 2 and 3 although this one is preferred in practice. Thus it is feasible to resort also to other clamping mechanisms that use wedge action, i. e. mechanisms that include one or more wedge surfaces that upon axial displacement in the transverse hole cause a pulling member to move axially in the first hole by co-operation with analogous wedge surfaces of the pulling mem- ber. It is also feasible to use clamping mechanisms that work with eccentric bodies.