TOOL ELEMENT

Abstract: A tool element (10) provided with a cutting insert is readily attachable to and detachable from an elongated holder body (12), which is secured to a machining tool. The tool element (10) is clamped against the holder body (12) by means of a bar (19) which is longitudinally movable in the holder body. In order to prevent the cutting forces from causing a relative movement between the tool element (10) and the holder body (12) projections (23, 24) on the tool element (10) are forced against opposed abutting surfaces on the holder body (12) by means of complementary cam surfaces on an enlarged portion (21) on the bar and on the projections (23, 24) upon a clamping movement of the bar (19).

Description: Tool element The invention relates to a tool element comprising a tool body which has an insert seat for receiving an insert. The tool body is provided with an abutment surface for abutting a corresponding surface of a holder body and is further provided with means to keep the tool body nonrotational with respect to the holder body. An expansible shank is connected to the tool body and receivable in a bore of the holder body. Typically, tool elements of the above type are mounted on tool holders which comprise an elongated shaft having a generally rectangular or round cross section. The shaft is secured to a machine tool, such as a lathe, usually by means of two or three screws. In machines using previously known types of tool holders the latters have to be replaced by another holder when the type of cutting inserts is exchanged, which results in high handling costs. Besides the elongated shaft requires a lot of room, which causes problems to the machine designer. Further, this technique is difficult to apply in a mechanized exchange of tools. In order to overcome the above problems it has been suggested in Swedish patent specification no. 401 469 and in Swiss patent specification no. 249 179 to mount the cutting insert on a separate tool element which can be clamped against the main body of the tool holder by means of a drawbar. In the first of these two prior art designs a shaft on the tool element projects into a recess in the forward end of the drawbar. The shaft is provided with a cam surface on its one side adapted for cooperation with a complementary cam surface in the recess. During clamping or the tool element a relative movement along the cam surfaces causes the shaft to be moved in the lateral direction until it abuts a supporting surface in the recess opposite to the cam surface therein. Due to the high cutting forces acting on the tool element during the working operation it has been found that this connection between the tool element and the holder body is. not rigid enough. In the prior art design-disclosed in Swiss patent specification no. 249 179 the tool element is clamped against Vshaped end surfaces on the holder body by means of a drawbar which is attached to the tool element through a threaded connection. Due to this threaded connection.a mechanized exchange of tool elements is difficult to achieve. The object of the present invention is to set forth a tool element which can be mounted on a holder body with a satisfactory rigidity, and thus an accurate positioning of the cutting insert, while making possible mechanized exchange of the tool element. This and other objects of the invention are attained by the characterizing features stated in the appending claims. The invention is described in detail in the following description with reference to the accompanying drawings in which three embodiments are shown by way of example. It is to be understood that these embodiments are only illustrative of the invention and that various modifications thereof may be made within the scope of the claims. In the drawings, Fig. 1 shows a side view of one embodiment according to the invention, wherein the cutting tool is shown in a righthand turning version. Fig. 2 shows a front view of the cutting tool in Fig. 1. Fig. 3 shows a top view of the cutting tool in Figs. 1 and 2. Fig. 4 shows a bottom view of the cutting tool in Figs. 1-3. Fig. 5 shows a section taken on the line A-A in Fig. 4. Figs. 6 and 7 show a side view and a top view, respectively, of an alternative embodiment according to the invention. Fig. 8 shows a top view of the forward portion of the holder body according to a further embodiment of the invention and a sectional view taken on the line B-B; the tool element being detached. Fig. 9 shows a top view and a sectional view taken on the line C-C of the holder body in Fig 8; the tool element being attached. Corresponding details in the various figures have been given the same reference numerals. The tool element shown in Figs. 1-5 comprises a tool body 10 which has an insert seat thereon for receiving a cutting insert 11. The planar outer surface of the cutting insert 11 is disposed in substantially the same plane as the top surface of the tool body 10. The tool body 10 is attached to an elongated shaft 12 at the outer end thereof; the shaft 12 providing the main body of a tool holder. The shaft 12 has a rectangular cross section and is adapted to be secured to a machine tool, such as a lathe in conventional manner. The tool body has abutment surfaces thereon for abutting corresponding surfaces of the shaft 12. In its clamped position against the forward end of the shaft 12 the tool body 10 is forced against a supporting surface 13 and a supporting end surface 14 perpendicular thereto on the holder body. The supporting end surface 14, which provides one of the abovementioned corresponding surfaces of the shaft 12, is broken by a recess or bore 15, which extends axially inwardly into the shaft 12. The axial supporting surface of the tool body 10, thus, is formed by two surfaces 14a, 14b lying in the same transversal plane. The recess 15 is bounded laterally by opposed planar abutting surfaces 16, 17, which extend in the longitudinal direction of the holder body 12 qn mutual parallelism The recess 15 is intended to receive a correspondingly shaped shaft portion or shank 18 on the tool body 10. Thus, the tool body 10 is provided with means for keeping the tool body nonrotational with respect to the holder body 12. According to the invention the tool body 10 is formed to accomodate reciprocally movable means in form of the forward portion 21 of a drawbar 19. The tool body 10 is clamped against the holder body 12 by means of the drawbar 19, which is longitudinally movable in the holder body 12. The portion 21 or the drawbar is received in a correspondingly shaped groove 20 in the tool body 10. In the illustrated embodiment the portion 21 is designed as a cylindrically rounded enlargement, which is connected to the main body of the bar 19 over a narrowed cylindrical neck portion 22. The groove 20, which is designed for locking interrelationship with the bar 19 has a corresponding cylindrical shape; it has, however, a somewhat larger cross section area than the enlarged portion 21.The opening of the groove 20 is narrowed by means of projections 23, 24 which project into the groove from both sides thereof. The projections 23, 24 and the portion 21 are provided with coacting cam surfaces for expanding the shaft portion 18 so as to force the side faces 25, 26 against the abutting surfaces 16, 17 in the bore 15 upon a movement of the drawbar 19 toward the cam surfaces of the shaft portion 18. The groove 20 terminates at the underneath side of the tool body 10, while its upward extent is limited by the planar top surface of the tool body 10. Due to this design problems caused by accumulation of chips in the joint are eliminated. Such accumulation would decrease the life of the joint and deteriorate its ready disassembling during exchange of the tool element. When the tool body 10 is to be clamped against the holder body 12 the tool body is first pushed thereagainst so that its bottom surface rests against the supporting surface 13 and its rear end surface rests against supporting end surfaces 14a, 14b. The enlarged portion 21 of the bar 19 is then received in the groove 20, while the shaft portion 18 of the tool body 10 -is received in the recess 15. During tightening of the bar 19 by means of a suitable operating means, such as a member 27 rotatably screwed to the bar, the tool body 10 is forced against the end surfaces 14a, b. When the bar 19 is further thightened the projections 23, 24 are caused to expand in opposite directions in the transversal direction of the holder body 12. The expansion of the projections 23, 24 is caused due to the coacting cam surfaces on the portion 21 adjacent to the neck portion 22 and on the projections 23, 24, see Fig. 4. Upon a slight expansion of the projections 23, 24, the latter are forced against the abutting surfaces 16, 17. Thus, a high compression force is applied on both side faces 25, 26 of the shaft portion 18, thereby ensuring that the joint members have no play between them. In order to adapt the design of the tool element to an automatized handling thereof the recess 15 for the tool element is symmetrical with respect to a vertical plane through the axial centre line of the holder body 12. Tool elements 10, thus, of left-hand as well as right-hand design can be mounted in the same holder body 12. In the illustrated embodiment the enlarged portion 21 of the bar 19 is cylindrically rounded. It is to be understood, however, that various modifications of this portion can be made. For instance, the widened portion can be dove-tailed and the groove 20 given a corresponding shape. In Figs. 6 and 7 an alternative embodiment of the invention is shown, wherein the shaft portion 18 of the tool body 10 and the front end of the holder body 12 are interconnected by means of a dove-tail joint. Thus, the mouth of the recess 15, which receives the shaft portion 18, is narrowed by means of mutually opposed wedge surfaces 28, 29 adapted for cooperation with complementary supporting surfaces on the shaft portion 18. The design of the drawbar 19 and the groove 20, which receives the enlarged portion 21 of the bar 19, is the same as that shown in Figs 1-5. Alternatively, however, as above-mentioned also the connection between the drawbar 19 and the groove 20 can be made as a dove-tail joint. In Figs. 8, 9 a further embodiment according to the invention is shown having a modified connection between the holder body 12 and the tool body 10. In similarity with the embodiment according to Figs. 1-5 side faces on the shaft portion 18 of the tool body are planar and parallel with the abutting surfaces 16, 17 in the recess 15. The end portion 21 of the drawbar, however, has the shape of a flattened cylindrical enlargement having two parallel and oppositely directed planar surfaces 30. 31. The distance between the surfaces 30, 31 corresponds to the diameter of the neck portion 22 on the drawbar, which neck portion interconnects the enlargement 21 and the main body of the drawbar 19. According to this embodiment the drawbar 19 is not tightened until the tool body 10 is placed in its position and the 0 drawbar then is rotated 90 from the releasing position shown in Fig. 8 to the locking position shown in Fig. 9. Such a design allows insertion of the tool element into the recess 15 in the holder body 12 either straight from above or straight from in front. The latter insertion technique is desired in a mechanized exchange of the tool element.

Claims: Claims 1. A tool element comprising a tool body (10) having an insert seat thereon for receiving an insert (11), and having an abutment surface thereon for abutting a corresponding surface (14) of a holder body (12)and with means thereon to keep said tool body nonrotational with respect to the holder body (12), and having an expansible shank (18) connected thereto, said expansible shank being receivable in a bore (15) of the holder body (12), characterized in that the tool body (10) is formed to accomodate reciprocally movable means (21), said expansible shank and movable means comprise coacting cam surfaces for expanding said expansible shank so as to lock said shank in the bore (15) of the holder body (12) upon a movement of said movable means toward the cam surfaces of the expansible shank t18). 2. A tool element according to claim 1, wherein the tool body (10) is provided with a groove (20) which comprises a cylindrical widened portion. 3. A tool element according to claim 2, wherein the groove (20) extends from the lower surface of the tool body (10) in an upward direction but does not extend completely to the top surface thereof. 4. A tool element according to claim 2, wherein the cam surfaces on the shank (18) are formed by the portions of the cylindrical widened portion which are adjacent to the distal end of the shank.

Inventors: ANDERSSON, KEN GOTE ESKIL, Andersson, Ken Göte Eskil
Applicants: SANTRADE LTD.
Application year: 1979
Main classification: B23B29
IPC codes: B23B29