Tool and clamp for chip removing machining

Abstract: The present invention relates to a clamp and a tool for chip removing machining, preferably for turning. The tool (10) has a holder (11) with a cutting insert pocket (12). The holder comprises a sloping surface (31) provided at a distance from the cutting insert pocket, which sloping surface slopes downwardly in direction from the cutting insert pocket. The holder has a threaded boring (30) for clamping of a clamp. A cutting insert (21) is provided in the cutting insert pocket (12) and has an at least partly planar upper side (22). Clamping means (25), which cooperates with a hole (37) in the clamp and the boring (30), is provided in order to force the cutting insert inwardly in said direction during mounting of the cutting insert. The clamp (24) and the holder (11) comprise a spring and/or a stop surface provided to counteract the movement of the clamp in said direction.

Description: Background of the invention The present invention relates to a tool and a clamp according to the preambles of the independent claims, as can be seen in US-A-3,325,877. Prior art Through US-A-4,480,950 or US-A 5,100,268 a tool of above type is previously known. The known tool comprises a clamp by which a cutting insert is clamped against a cutting insert pocket in a holder. The forward end of the clamp cooperates with a recess in the cutting insert such that the cutting insert is pushed both downwards and inwards at tightening of a screw which acts on the mid section of the clamp. The rear end of the clamp comprises an oblique surface that cooperates with an oblique surface on the holder. The clamp is moved during said tightening. A drawback of the known tool is that the cutting insert must include said recess such that the clamp can function satisfactorily. Another drawback is that plastic deformation of the clamp can occur. Furthermore, solid cutting inserts with planar surfaces cannot be satisfactorily held by means of the known device. Objects of the invention One object of the present invention is to provide a tool and a clamp, which comprises the advantages common with prior art. Another object of the present invention is to provide a tool, which comprises a carefully defined stop for the clamp in order to avoid plastic deformation of the clamp. Another object of the present invention is to provide a tool, which comprises a clamp with a longer useful engagement than previous tools. Still another object of the present invention is to provide a tool in which a planar cutting insert can be rigidly clamped. Still another object of the present invention is to provide a clamp in order to attain the above-captioned advantages. These and other objects have been achieved by a tool and a clamp as defined in the appended claims with reference to the drawings. Description of the drawings Fig. 1 shows an exploded view of a tool according to an embodiment of the present invention in a perspective view. Fig. 2A shows the tool in an assembled condition in a perspective view. Fig. 2B shows the tool in an assembled condition in plan view. Figs. 3A-3C show a mounting sequence of the tool according to the cross-section III-III in Fig. 2B. Figs. 4A-4C show the mounting sequence in an enlarged part of the tool. Detailed description of the invention The tool 10, Fig. 1, comprises a cutting insert holder 11 intended for turning, which in its forward end ends in a taper, wherein is provided a cutting insert pocket 12 with two relative to each other angled support surfaces 13,14 as well as a bottom surface 15. The bottom surface comprises one orifice of a threaded hole. The holder has a shank 16. A first recess 17 is provided in the proximity of the cutting insert pocket 12 in direction towards the shank. The recess 17 connects to a second recess 18 provided still further away in direction F towards the shank. The tool 10 further comprises a shim 19 provided to be forced against the bottom surface by a fastening screw 20. Furthermore, a cutting insert 21 is intended to abut against the shim 19 and the support surfaces 13, 14. The cutting insert 21 has a polygonal basic shape with substantially planar and parallel side faces 22. In some cases only the central portions of the cutting insert may be planar and parallel while the chip surface and adjacent surfaces are profiled. The cutting insert pocket may alternatively be provided for round, triangular or rhombic cutting inserts or trigon inserts (ISO W inserts). In order to firmly clamp the cutting insert 21 in the cutting insert pocket 12 a clamping means 23 is provided, which consists of a lever or a clamp 24, a screw 25, a spring 26, a positioning pin 27, a hollow pin 28 and a pressure cup 29. The pin 27 is for the sake of clarity not shown in Figs. 3C-4C. The clamp 24, Figs. 3A-3C, has substantially the shape of an elongated wedge, wherein the clamp has a longitudinal axis 33 and a relatively central hole 37. The clamp is maneuverable by means of the screw 25 threaded into a boring 30 of the cutting insert holder 11. The center axis of the boring 30 is parallel to the threaded hole in the cutting insert pocket. The clamp has a forward end with an essentially part-spherical surface intended to abut against a complementary surface on the pressure cup 29. The pressure cup is retained at the clamp by the hollow pin 28, which cooperates with holes in both the cup and the clamp. The pressure cup is retained at the clamp in such a manner that the pressure cup is admitted a certain mobility around the radius center of the part-spherical surface. The lower side of the pressure cup is substantially planar. The second recess 18 of the holder, Fig. 5, comprises two towards each other inclined and substantially perpendicular first and second surfaces 31 and 32, respectively. The first surface 31 can alternatively be called sloping surface while the second surface 32 can be called stop surface. Said surfaces are provided substantially perpendicular to the longitudinal axis 33 of the clamp when the tool is seen in the top view of Fig. 2B. The first surface forms an angle about 30-60° with an upper side 34 of the holder. A boring 35 terminates substantially in the middle of the first surface relative to the lateral direction of the clamp. The boring 35 is intended to receive the positioning pin 27, which in turn is intended to be fitted with a gap into a recess 36 in the clamp. The pin 27 is intended to guide the clamp via the recess 36during the mounting sequence. Alternatively, the pin can be integrated with the clamp instead of the pin 27 and the boring 35, whereby the pin during clamping is provided to run in a groove in the surface 31. The second end of the clamp facing away from the pressure cup comprises a projection 38. The free end of the projection 38 facing towards the holder, comprises two surfaces: first and second surfaces 39 and 40 respectively, sloping towards each other, Fig. 4C. The first surface 39 may alternatively be called a slide surface while the second surface 40 can be called an abutment surface. Said surfaces extend substantially perpendicularly to the longitudinal axis 33 of the clamp when the tool is seen in the top view of Fig. 2B. The first surface 39 is convex and the second surface 40 forms an angle about 45° with an upper side 34 of the holder. The projection 38 has a rear surface 41 to which a lip 42 is connected. The lip 42 connects at the part of the surface 41 which is situated farthest away from said free end. The lip is preferably integral with the clamp by having a slot 43 machined out of the basic material. The lip can alternatively be attached to the clamp in other manners. The lip 42 extends past a plane that is defined by the second surface 40 of the projection or by a tangent thereto in case the second surface 32 is curved. The slot 43 shall most preferably not be entirely closed during the mounting procedure. The clamping means 23 functions as follows, Figs. 3A-4C. The positioning pin 27, which preferably is slotted, is firmly pressed into the boring 35 and the spring 26 is put in an enlargement of the boring 30. When the pressure cup 29 is mounted with the aid of the hollow pin 28 to the end of the clamp in accordance with the above-mentioned procedure the threaded part of the locking screw 25 is brought through the hole 37 in the clamp and subsequently through the spring and is threaded into the boring 30, see Figs. 3A and 4A. In this situation the clamp lacks direct contact with both the cutting insert and the holder. This position substantially constitutes correct position at exchanging or indexing of a cutting insert. The head of the locking screw is the only part of the screw intended to remain in contact with the clamp during the mounting procedure when the lower side of the head may slide on a shoulder in the recess 37. The spring is provided to lift the clamp during loosening of the screw. A cutting insert 21 is inserted in the cutting insert pocket 12, whereafter further tightening of the screw 25 forces the clamp in direction towards the holder and the cutting insert such that the planar lower side of the pressure cup engages with the solid planar upper side 22 of the cutting insert and the first convex slide surface 39 of the projection 38 engages with the inwardly and rearwardly inclined first surface 31 of the recess 18 and the end of the lip 42 engages with the forwardly inclined stop surface 32. By "solid" cutting insert is here meant a cutting insert without any through-going central hole for pin or screw attachment. The extreme or forwardmost part of the pressure cup is then provided at the distance a1 from the extreme or forwardmost point P of the cutting insert in the cross-section according to Fig. 3B. During still further tightening of the screw 25 the clamp is forced farther in direction towards the holder and the cutting insert as well as somewhat rearwardly in direction F due to cooperation between the surfaces 31 and 39. Simultaneously the lip wants to counteract this motion in direction F, and therefor the clamp tilts about the screw such that a substantial pressure arises between the pressure cup and the cutting insert even before the projection 38 bottoms in the recess 18 by having the surface 40 abutting against the surface 32. This means that friction between the pressure cup and the cutting insert becomes great such that the cutting insert is forced in direction F together with the movement of the clamp inwards towards the support surfaces 13, 14. The extreme part of the pressure cup (Fig. 3C) is then provided at the distance a2 from the extreme point P of the cutting insert in the section according to Fig. 3B. The distance a2 is greater than the distance a1. Subsequently the projection 38 bottoms such as is shown in Figs. 3C and 4C by having the abutment surface 40 of the projection 38 abutting against the stop surface 32 of the recess 18. The operator notes this as a sudden increase in the resistance against tightening, which obviates plastic deformation of the clamp and the screw. Since the projection 38 forms an essentially V-shaped place of contact with the recess 18 the clamp becomes rigidly fixed in the position according to Fig. 3C. At indexing of the cutting insert the screw is untightened somewhat such that the cutting insert is pushed forwardly by the force of reaction from the lip 42 shortly before the pressure cup disengage with the upper side of the cutting insert. The cutting insert thereby becomes easy to index. The present invention consequently relates to a tool and a clamp with a movement stop and a with greater useful engagement than earlier, whereby planar preferably solid, cutting inserts may be rigidly clamped foremost by engaging the clamp frictionally at an early stage during the mounting procedure with the cutting insert in comparison with prior art devices.

Claims: Tool for chip removing machining, preferably for turning, including: a holder (11) with a cutting insert pocket (12), which has a bottom surface (15,19) and at least one support surface (13,14), said holder comprising a sloping surface (31) provided at a distance from the cutting insert pocket, which sloping surface slopes downwardly in direction (F) away from the cutting insert pocket, said holder having a threaded boring (30) for clamping of a clamp, said holder being provided to be able to hold a solid cutting insert, a cutting insert (21) provided in the cutting insert pocket (12), said cutting insert having an at least partly planar upper side (22), a clamp (24) provided on said holder (11) in contact with the cutting insert, said clamp having a projection (38) with a slide surface (39) in contact with said sloping surface (31) of the holder, clamping means (25) which cooperates with a hole (37) in the clamp and the boring (30) in order to force the cutting insert inwardly in said direction (F) during mounting, characterized in that the clamp (24) and the holder (11) comprise means (32,40,42) spaced from the clamping means (25) and provided to counteract the movement of the clamp in said direction (F). Tool according to claim 1, wherein the means comprise a device (42) resilient relative to the clamp (24), and wherein the means comprise a stop surface (40) sloping towards the slide surface (39) provided to cooperate with an inclined abutment surface (32) sloping towards the sloping surface (31). Tool according to claim 2, wherein the device consists of a lip (42), which connects to a rear surface (41) of the projection (38). Tool according to claim 3, wherein the lip (42) is connected to the part of the rear surface (41) which is situated farthest away from a free end of the projection and that the lip is integral with the clamp (24) by machining a slot (43) from the basic material of the clamp. Tool according to claim 3, wherein the lip (42) extends past a plane which is defined by the stop surface (40) of the projection or a tangent thereto. Clamp to form a part of a tool according to claim 1, wherein the clamp (24) has a projection (38) with a slide surface (39), said clamp being provided to be able to clamp a solid cutting insert to a cutting insert pocket, said clamp (24) having a relatively central hole (37), characterized in that the clamp (24) comprises means (40, 42) spaced from the relatively central hole (37) and provided to counteract the movement of the clamp in a direction (F). Clamp according to claim 6, wherein the means comprise a device (42) resilient relative to the clamp (24) and wherein the means comprise a stop surface (40) sloping towards a slide surface (39). Clamp according to claim 7, wherein the device consists of a lip (42), which connects to a rear surface (41) of the projection (38). Clamp according to claim 8, wherein the lip (42) connects to the part of the rear surface (41) which is situated farthest away from a free end of the projection and that the lip is integral with the clamp (24) by machining a slot (43) from the basic material of the clamp. Clamp according to claim 8, wherein the lip (42) extends past a plane which is defined by the stop surface (40) of the projection or a tangent thereto.

Inventors: JANSSON MIKAEL, JANSSON, MIKAEL
Applicants: SECO TOOLS AB
Application year: 1999
Main classification: B23B27
IPC codes: B23B27