Milling tool

Abstract: A cutter head (1) is equipped with cassettes (6) and cutting inserts (17) which can be fastened by means of one or more clamping wedges (7, 7a). On the rear side of the individual cassette there is a serration which co-operates with a serration (14) in a rear wall of a recess (5) for the cassette. A bottom wall (10) in the recess is divided into a plurality of part walls (10', 10''), which are spaced-apart by a first abutment surface (21) against which an analogous second abutment surface (22) on the cassette can be pressed. Thanks to this design, the cassette may be rapidly and simply mounted in a basic position in which it is held with good stability.

Description: Technical Field of the Invention This invention relates to a milling tool of the type that comprises a body rotatable around a central geometric axis, which body has a peripheral envelope surface extending between opposite end surfaces in which envelope surface recesses are provided which open outwards, each one of which is defined by a front wall, a rear wall and a bottom wall and has the purpose of receiving a machining element which carries a cutting insert as well as at least one clamping wedge arranged in the recess for fixing the machining element, which clamping wedge can be tightened by means of a clamping screw in engagement with a threaded hole which opens into the bottom wall of the body, the rear wall of the recess has a first serration arranged to co-operate with an analogous second serration on a rear side of the machining element, while the front wall is smooth in order to co-operate with a similar smooth, front surface on the clamping wedge, and a rear contact surface on the clamping wedge and a front contact surface on the machining element both being smooth in order to allow a substantially radial displacement of the clamping wedge in relation to the machining element in connection with the clamping thereof. Prior Art A milling tool of the above generally mentioned kind is previously known from EP 0548036 A1. In this case, the individual machining element, which is in the form of a cassette having a detachable cutting insert, is insertable in the appurtenant recess from either side of the body or cutter head, the desired positional determination of the cassette taking place by manual fine adjustment before the clamping wedge is finally tightened. It is true that the possibility of applying a locator pin on the interior of the cassette intended to engage into a countersink in the bottom wall of the recess is outlined, but since this countersink has a larger diameter than the locator pin, a determined, exactly defined axial starting position for the cassette, when this is to be mounted in the recess, is not obtained. The work of finely adjusting the cassette manually in connection with the assembly is difficult and time-consuming. Another inconvenience of the design of the known tool is that it has only a limited ability to resist minor breakdowns of the type that easily may arise when the cassettes together with the cutting inserts are submitted to instantaneous impacts or shock loads. Therefore, even if total breakdowns can be avoided, frequently so much damage arises on, above all, the cassettes that these have to be discarded and replaced. Furthermore, each individual cutting insert is attached to the appurtenant cassette by means of a screw which incorporates a screw head, said screw extends through a through hole in the cutting insert and which is fastened in a threaded hole in the cassette. The fact that the design not only includes a clamping wedge for fixing the cassette, but also a special clamping screw for fixing the cutting insert in the cassette, means, in practice, that the tolerance chain between, on the one hand, the tool body together with the rotation axis thereof and, on the other hand, each one of the several cutting inserts becomes extensive. This entails, among other things, that the precision in the adjustment of the cutting insert in relation to the tool body (which in practice should be less than 1/100 mm) may easily be lost or become unsatisfactory, e.g. when the cutting inserts are to be replaced or indexed or when the cassette, for one reason or another, has to be dismounted and remounted. A tool according to the preamble of independent claim 1 is known through US 4474512 A. Objects and Features of the Invention The present invention aims at obviating the above mentioned inconveniences of the previously known milling tool and at providing an improved milling tool. Therefore, a primary object of the invention is to provide a milling tool in which the machining elements, in particular such machining elements which are in the form of cassettes having detachable cutting inserts, can be located in a simple way in an exactly defined operating position in relation to the tool body in connection with the assembly. In other words, it should be possible to mount the machining elements rapidly without necessarily having to finely adjust them manually. Another object is to provide a milling tool with a good ability to resist at least minor incidents, which could cause breakdowns in connection with impacts or shock loads of an instantaneous character, which may occur. In particular, the machining element or the cassette should be able to resist such loads without being seriously damaged or displaced from its basic position. Another object of the invention is to provide a milling tool that is suitable for operation at very high rotational speeds, e.g. all the way up to the range of 20 000-30 000 revolutions/minute. According to the invention, at least the primary object is attained by the features defined in claim 1. Preferred embodiments of the invention are furthermore defined in the dependent claims. Brief Description of the Appended Drawings In the drawings: Fig 1 is a perspective exploded view showing a part of a milling tool according to the invention, a number of cassettes and cutting inserts belonging to the tool being illustrated distanced from the body of the tool, Fig 2 is a perspective view of an individual cutting insert included in the tool, Fig 3 is an additional perspective view showing an alternative embodiment of the cutting insert, Fig 4 is a partial, schematic side view showing a cassette, a cutting insert and a clamping wedge in a first functional state, Fig 5 is a side view corresponding to fig 4 showing said components in a second functional state, Fig 6 is a third side view showing a third functional state, Fig 7 is a perspective exploded view corresponding to fig 1 showing an alternative embodiment of the invention, Fig 8 is an enlarged detailed view illustrating a means for fine adjustment of cassettes, more precisely shown in a first position, and Fig 9 is a detailed view corresponding to fig 8 showing the adjustment means in a second functional state. Detailed Description of Preferred Embodiments of the Invention In fig 1, a body in the form of a cutter head is generally designated 1, which is rotatable around a central geometric axis (not shown). In the example, the body 1 is delimited by a peripheral, envelope-like surface 2, which extends between opposite end surfaces 3, 4 of which the first-mentioned one consists of a front side in the vicinity of which the tool cutting insert is located, while the last-mentioned one consists of a rear side to which a rotatable spindle or the like (not shown) is connected in a suitable way. Recesses 5, which open outwards, are provided in the envelope surface 2, the purpose of these recesses is to accommodate cassettes 6, as well as at least one clamping wedge 7. Each separate recess 5 (see also fig 4-6) is delimited by a front wall 8, a rear wall 9 and a bottom wall generally designated 10. The clamping wedge 7 co-operates with and is possible to clamp by means of a screw 11 which is in engagement with a threaded hole 12 which opens into the bottom wall 10 of the recess 5. More precisely, the screw 11 is of the type, which includes a right-hand thread as well as a left-hand thread, separated therefrom via a waist portion. Of these threads, one is in engagement with the hole 12 in the tool body, while the other one is in engagement with a threaded, through hole 13 in the clamping wedge 7. The two male threads on the screw 11 have a certain play in relation to the female threads of the holes 12, 13. The existence of double threads on the screw 11, makes it possible to attain, in a known way per se , a function whereby the clamping wedge 7 may be displaced in relation to the body with an increased, e.g. doubled, speed in comparison with one single simple thread in connection with rotation of the screw in either direction of rotation. The rear wall 9 of the recess 5 has a first serration generally designated 14 which is arranged to co-operate with an analogous, second serration 15 on a rear side of the cassette 6. In this connection, it should be pointed out that the concepts "front" and "rear" walls, respectively, are related to the direction of rotation of the tool which is outlined by means of the arrow A. Thus, viewed in the direction of rotation of the tool, the serration 15 is provided on the rear side of the cassette which is turned from a front side in which a seat 16 for a cutting insert 17 is provided. The front wall 8 of the individual recess 5 is (at least partially) smooth and suitably plane in order to co-operate with a likewise smooth and plane, front surface 18 on the clamping wedge 7. A rear contact surface 19 (see also fig 4-6) on the clamping wedge 7 is likewise smooth and plane so as to co-operate with a front, plane and smooth contact surface 20 on the cassette 6. Thanks to the fact that said surfaces 8, 18, 19 and 20 are smooth, the clamping wedge may, without obstacle, be displaced substantially radially in relation to the tool body and the cassette so as to wedge the latter. Although the serrations 14, 15 advantageously are of a known type, it is, however, worth pointing out that they are formed generally as ridges which are spaced-apart by intermediate grooves. As may be seen in fig 1 in combination with fig 4, the individual serration or tooth surface thus includes a set of long narrow, straight and mutually parallel ridges which may engage the grooves in the second serration. The ridges as well as the grooves are of a triangular cross-sectional shape, the free cams of the ridges being bevelled so that the ridges do not touch the bottom in the co-operating grooves when the serrations are brought to engagement with each other. This means that each separate ridge in one of the serration is wedged very steadily between a pair of surrounding ridges in the other serration. In other words, a plurality of wedge joints are obtained in the interface between the cassette and the tool body. In practice, the nose angle between the flank surfaces of the individual ridges (and the corresponding angle between the side surfaces of the individual groove) may amount to approx. 65°. Advantageously - though not necessarily - the serration 14 extends all the way along the axial length of the recess 5, i.e. between the end surfaces 3, 4, in a similar manner the serration 15 extend along the entire length of the cassette 6. As far as the milling tool shown in the drawings has been described hitherto, the same, is in all essentials, previously known from EP 0548036 A1. As a matter of form, before the features of the tool characteristic for the invention are described in more detail, it should be pointed out that the two different embodiments of cutting inserts which are shown in fig 2 and 3 are at the same time illustrated in fig 1. More precisely, the cutting insert 17 according to fig 2 is shown together with a cassette 6 which in a certain aspect differs from the two cassettes 6 which house a cutting insert 17' of the type that is shown in fig 3. In practice, only cassettes together with cutting inserts of one and the same uniform type are used on the milling tool, but for reasons of space, it has been chosen to illustrate the two different types of cutting inserts and cassettes in one and the same drawing figure. According to the invention, the bottom wall 10 of the individual recess 5 is divided into at least two part walls 10', 10'' located at different radial distances from the rotation axis of the tool body, which part walls are spaced-apart by a first abutment surface 21 turned towards the cutting insert. Said abutment surface 21 extends at an angle, suitably perpendicularly, to the serration 14 in the rear wall of the recess and has the purpose of co-operating with an analogous, second abutment surface 22 on the cassette 6. It also extends perpendicularly to the part wall 10'. The second abutment surface 22 extends correspondingly on one hand perpendicularly to the serration 15 of the cassette (strictly speaking perpendicularly to the axial extension of the ridges and the grooves), and, on the other hand, perpendicularly to a first plane surface 23 on the interior of the cassette as well as a second plane surface 24 (see fig 5) thereon. Said first abutment surface 21 extends along the entire width of the recess 5 in the area of the bottom thereof. In an analogous way, the second abutment surface 22 extends along the entire width of the cassette at the interior thereof. In the embodiment example shown, the bottom part wall 10'' transforms into an angled part wall 10'''. This angled part wall 10''' extends perpendicularly to the front wall 8 of the recess, at the same time as the part wall 10'' extends perpendicularly to the rear wall 9 provided with the serration 14. The angle between the front and rear walls 8, 9 should in practice be within the range of 25-35°. From this follows that the angle between the part walls 10'' and 10''' is within the range of 145-155°. It should also be mentioned that a threaded hole 25 opens into the part wall 10''' this hole is for a clamping screw 26 to a second clamping wedge 7a, which has the purpose of only clamping the cassette 6, but not the cutting insert 17, When the cassette 6 is mounted in the recess 5, the same may, in a rapid and simple manner, be positioned in a predetermined basic position merely by the simple measure of bringing the serrations 14, 15 to slide along each other until the abutment surface 22 is pressed against the abutment surface 21. Due to the fact that the abutment surface 21 on the tool body (also in the cases when this is made of aluminium) as well as the abutment surface 22 on the cassette (most often of steel) may be formed with high accuracy, the cassette may be mounted in a simple way in an exactly defined basic position which can be repeated with ease and is consistent for all cassettes and recesses of the tool. Another substantial advantage of the invention is that the cassette in the wedged or clamped state thereof, according to fig 6, is held with extremely good stability, not only by the numerous and large-faced wedge joints in the serrations 14, 15, but also by the fact that the abutment surfaces 21, 22 are comparatively large and in complete surface contact with each other. Thus, the serrations 14, 15 counteract, in a effective way, any tendency to radial displacement of the cassette at the same time as the clamping wedge counteracts tendencies of the cassette to tip, and the abutment surfaces 21, 22 counteract tendencies of the cassette to turn around an imaginary, radially directed geometric axis. The milling tool may be provided with means to enable fine adjustment of the cassette in relation to the body. In fig 1 such a means is exemplified in the form of a separate key 27, serving as an adjusting element, which is insertable in a cylindrical, through bore 28 in the cassette. The key includes a cylindrically shaped shaft 29, which at a free end transforms into an eccentric body 30 which may be brought to engagement with an elongated countersink 31 in the bottom part wall 10''. Therefore, by turning the key, the cassette may be given fine, axial movements in relation to the tool body, while the two clamping wedges are moderately tightened. To be able to make fine adjustments to the cassette, e.g. within a thousandth or hundredth of a millimetre, it is important in such cases when tolerance deviations are found in connection with manufacture, as well as in such cases where the cassette unexpectedly would be displaced from the basic position thereof, e.g. as a consequence of shock loadings. In fig 4-6, a preferred embodiment of the invention is illustrated in which the cutting insert 17 is detachably mounted in the seat 16 of the cassette 6. More precisely, the cutting insert may be clamped in the seat with one and the same clamping wedge 7 that is used for fixing the cassette 6. In order to enable this, the clamping wedge is provided with an outer, secondary contact surface 32, which is displaced backwards in relation to the inner contact surface 19 co-operating with the corresponding contact surface 20 of the cassette 6. In fig 4, the clamping wedge 7 is shown in an outer, inactive position in which the cassette 6 as well as the cutting insert 17 may be removed from the recess 5. In fig 5, the clamping wedge 7 is shown in a provisionally clamped intermediate position in which the inner contact surface 19 of the clamping wedge has boarded the contact surface 20 of the cassette. In this state, the cassette 6 is fixed in the given position thereof by the fact that the serrations 14, 15 are wedged up in each other. However, here the cutting insert 17 is still only loosely inserted into the seat 16. In fig 6, the clamping wedge 7 takes a final tightened, inner end position in which the secondary contact surface 32 has been pressed against the plane front side of the cutting insert. The cutting insert 17' shown in fig 3 differs from the simpler cutting insert according to fig 2 by having a countersink in the front side thereof with a cross-section flute 33 in the shape of a V, into which a male projection (not shown) provided on the clamping wedge having a secondary contact surface 32 may engage. On the underside of the cutting insert, a female recess 34 is provided with the shape of a truncated cone. A male member 35 (see at top right in fig 1), having a smaller diameter than the recess 34, may engage therein. By means of the countersink 33 and the recess 34 together with the two male members engaging therein, the cutting insert 17' is secured against centrifugal forces. In other words, it is ensured that under no circumstances will the cutting insert be exposed to the risk of being thrown out of the appurtenant seat in such cases when the milling tool is driven at a very high rotational speeds. Reference is now made to fig 7, which illustrates an alternative embodiment of the invention in which a cassette designated 6' co-operates with a separate support element 36 in the extension of the cassette. The support element 36 has a length that (for a given thickness of the cutter head) in the main corresponds to the length difference between the previously described cassette 6 and the shorter cassette 6', according to fig 7. Like the cassette 6', the support element 36 has a rear serration 15 for engagement with the serration 14. A threaded, through hole 37 for a screw 38 extends axially through the support element 36. At the end thereof turned towards the cassette 6', the screw 38 has a flat head 39. At the opposite end, there is a seat 40 having a polygonal cross-section shape for the receipt of a key, e.g. an Allan key. A male member 41 is provided on the interior of the support element 36, it has the shape of a cylindrical stud and is intended to co-operate with a female recess 42 in the part wall 10''. This recess 42 has more precisely an elongated shape. In fig 8, the adjustment screw 38 is shown in an inactive state in which the head 39 of the screw is housed in a countersink 43 in the end surface 44 of the support element that is turned towards an opposite end surface 45 on the cassette 6'. In this state, the abutment surface 22 of the cassette is pressed against the abutment surface 21 in the bottom wall of the recess; i.e. the cassette takes the basic position thereof. If the need arises to make a fine adjustment to the cassette and the cutting insert 17 thereof, e.g. as a consequence of a breakdown or the like, the screw 38 may be used for this purpose. On activation, it ensures that the stud 41 abuts distinctly against one end of the seat 42 at the same time as the second clamping wedge 7a clamps the support element 36. With the cassette 6' only provisionally fastened - due to the fact that the first clamping wedge 7 is only loosely tightened - the cassette may be displaced axially by turning the screw 38. In fig 9 this is shown in an exaggerated way for the sake of clarity. In practice, however, it most cases it is a question of moving the screw axially some hundredths or tenths of a millimetre, more precisely by turning the screw only fractions of a revolution. For this purpose, the screw 38 should have a small thread pitch. When the cassette has been adjusted into the desired, exact position, the clamping wedge 7 is finally re-tightened while fixing the cassette together with the appurtenant cutting insert. Feasible Modifications of the Invention The invention is not solely restricted to the embodiments described and shown in the drawings. Thus, the invention may also apply to such machining elements which include cutting inserts 17 or similar cutting insert members, e.g. diamond chips, which are integrated with a cassette-like carrier. In other words, the cutting insert member is, in such cases, permanently united to the carrier, e.g. by being soldered thereto. What is essential however is that the machining element includes a cutting edge.

Claims: Milling tool comprising a body (1) rotatable around a central geometric axis, which body has a peripheral envelope surface (2) extending between opposite end surfaces (3, 4) in which envelope surface recesses (5) which open outwards are provided, each one of which is defined by a front wall (8), a rear wall (9) and a bottom wall (10) and has the purpose of receiving a cutting insert carrying machining element (6, 6') as well as at least one clamping wedge (7) arranged in the recess for fixing said element, which clamping wedge is possible to clamp by means of a clamping screw (11) in engagement with a threaded hole (12) in the body (1) which opens into the bottom wall (10), the bottom wall (10) of the individual recess (5) being divided into at least two part walls (10', 10") located at different radial distances from the axis of rotation, which part walls are spaced-apart by a first abutment surface (21) that is made as an integrated unit with the body (1), the first abutment surface (21) having the purpose of cooperating with an analogous second abutment surface (22) on the machining element (6, 6'), more precisely with the purpose of holding the same in an exactly defined position in relation to the tool body (1), the front wall (8) being smooth in order to co-operate with a similar smooth, front surface (18) on the clamping wedge (7), and a rear contact surface (19) on the clamping wedge and a front contact surface (20) on the machining element both being smooth in order to allow a substantially radial displacement of the clamping wedge in relation to the machining element in connection with the clamping thereof, characterized in that the rear wall (9) of the recess (5) has a first serration (14) arranged to co-operate with an analogous second serration (15) on a rear side of the machining element, that the first abutment surface (21) extends at an angle in relation to the serration (14) in the rear wall (9) of the recess (5) and that the second abutment surface (22) is made as an integrated unit with the cutting insert carrying machining element (6, 6'). Milling tool according to claim 1, characterized in that said angle between the first abutment surface (21) and the serration (14) in the rear wall (9) of the recess (5) is right-angled, and the angle between the second abutment surface (22) and the serration (15) of the machining element likewise being right-angled. Milling tool according to claim 1 or 2, characterized in that the first abutment surface (21) extends along substantially the entire width of the recess (5) in the area of the bottom thereof. Milling tool according to any one of the preceding claims, characterized in that the same comprises means (27, 38) so as to, if required, enable fine adjustment of the position of the machining element (6, 6') in relation to the tool body (1), more precisely by axial displacement of the serrations (14, 15) in relation to each other from the starting position which the machining element (6) occupies when the two abutment surfaces (21, 22) are in contact with each other. Milling tool according to claim 4, characterized in that said means comprises a bore (28) with a circular cross-section extending substantially radially through the machining element (6), as well as a countersink (31) in the bottom part wall (10'') which is situated on the largest radial distance from the axis of rotation, a separate adjusting element (27), including a shaft (29) with a circular cross-section and an eccentric body (30) at a free end thereof, being insertable in the bore so as to - with the eccentric body (30) engaging the countersink (31) and with the clamping wedge (7) only loosely tightened - by turning in relation to the bore, guarantee an axial displacement of the machining element from said starting position. Milling tool according to claim 4, characterized in that a separate support element (36) with a serration (15), which is in engagement with the serration (14) in the rear wall (9) of the recess (5), is arranged in the axial extension of the machining element (6) and that a second clamping wedge (7a) is arranged to clamp the support element, said fine adjustment means comprising a screw (38) arranged in a threaded, through hole (37) in the support element (36). Milling tool according to claim 6, characterized in that the support element (36) co-operates with the tool body (1) via a mechanical connection of the male/female type (41, 42), which guarantees that the support element in connection with a possible fine adjustment of the machining element (6) may take an immovable end position independently of the degree of tightening of the second clamping wedge (7a).

Inventors: QVARTH INGEMAR, QVARTH, INGEMAR
Applicants: SANDVIK INTELLECTUAL PROPERTY, SANDVIK INTELLECTUAL PROPERTY AB
Application year: 1999
Main classification: B23C5
IPC codes: B23C5