PIN LOCK SYSTEM FOR AN INSERT WITH A BLINDHOLE AN A L-SHAPED LOCK PIN

Abstract: According to the invention, an insert holder (10) exists for indexable cutting inserts. In connection with the insert seat, a clamping device is located, including an L-shaped toggle joint (18), of which one arm (21) is received in a hole (13) in the cutting insert and of which the second arm (22) is actuated by a pressure member (19). Characteristic of the invention is that the hole (13) in the cutting insert is a blind hole and that the end portion of the arm (22) co-operating with the member (19) has a V-shaped cavity (23) in order to enclose a waist portion (24) of the member (19).

Description: lock system for an insert with a blindhole and a L-shaped lock pin. The present invention relates to a new type of cutting tool, including an insert holder for clamping an indexable cutting insert provided with a cavity in a cutting seat in the holder body, so that the cutting insert rests against a base surface, a locking pin, fixed in a bore in the holder and extending up in the bore of the cutting insert, being arranged to ensure a stable location of the cutting insert for clamping the cutting insert against at least one lateral support in the cutting seat. Many different insert holders of the pin type are known, in which clamping of the cutting insert is provided by means of a pin extending up into a hole in the cutting insert, the lever movement of the pin being provided by the opposite end of the pin co-operating with a pressure generating member placed in the holder. The Swedish patent 357316 shows an example of such an insert holder of the pin type. However, with this type of holder, unfavourable positional changes of the cutting insert during the machining operations in progress have sometimes been noted. Furthermore, it is previously known from, for instance, the Swedish patent specification 368 786 a pin holder, where a locking pin, fixed in a bore in the insert holder and extending up in a hole in the cutting insert, is arranged to co-operate with a pressure member placed in the insert holder for clamping the cutting insert against at least one lateral support in the cutting seat. However, this type of holder having a built-in toggle joint for engagement with the insert hole is only thought to work together with the type of cutting inserts having a central through hole extending up through the entire cutting insert. Furthermore, this is a necessity with the solution given in said patent SE-368 786 since there it is assumed that the L-shaped arm co-operating with the cutting insert should also have a side projection which is arranged to be able to push the cutting insert from above, downwards against the shim thereof. This type of holder has, however, the disadvantage that it is necessary that the cutting insert has a central through hole. Characteristic for this type of cutting insert is a major risk of breakage of the cutting insert, especially if they are made of mixed ceramics or pure ceramics, which are cutting materials, which are used more and more. Another disadvantage with this type of insert holder is that as the machining operation progresses, dirt and particles fall down in the central insert hole and gather in the bottom of the cavity, which receives the locking device formed as a toggle joint. Occasionally, even difficulties with releasing the cutting insert during insert changing may occur. The purpose of the invention is now to provide a new and improved type of tool, which is not impaired by the above-mentioned inconveniences. According to the invention, it is proposed that an insert holder be equipped with a hole, which does not pass through the cutting insert, in which hole a substantially L-shaped support pin is received. At the same time, a bore is formed in the holder separated from the cavity which receives the first-mentioned support pin in which a pressure member is arranged with a marked waist portion for co-operation with said V-shaped cavity. When the pressure member is rotated, on the one hand, a downward force on one arm of the support pin is generated, which causes the cutting insert to be pressed against the bottom surface of the cutting seat, at the same time as a force is generated by the inclination of the support pin which is directed inward towards the holder body, this brings about the clamping of the cutting insert against the lateral support or lateral supports via the support pin. Other features which are characteristic of the invention are more closely defined in subsequent claims. The invention is better understood from the following description and drawings, showing a preferred embodiment according to the invention, where: Fig. 1 shows a planar view of the insert holder, Fig. 2 a section view along the line II-II and Fig. 3 a section view along the line 111-111 in Fig. 1, Fig. 4 a perspective view of the holder in Fig. 1, Fig. 5 a perspective view of the cutting insert and the clamping members thereof, Fig. 6 a planar view of another embodiment, Fig. 7 a section view along the line V-V in Fig. 6, and Fig. 8 a detailed enlargement of Fig. 7. In the drawing, an insert holder body is designated 10, which at an end portion has a cutting seat with a bore 11 connected to the bottom thereof. An indexable insert 12, having a central hole 13, that has a bottom 14, is fixed in the cutting seat. The insert seat comprises a base surface 15, which is integrated into the holder or is formed by a detachable shim, which may consist of cemented carbide in order to retain its hardness and flatness. The cutting insert 12 is round with a central elevated plateau 12a. The lateral support of the insert seat is formed by the surfaces 16 and 17, which have a concave bending corresponding to the shape of the cutting insert. The surfaces 16 and 17 have a conical shape corresponding to the flank surface 12b of the cutting insert, the clearance angle of which is normally 4-8°. A support pin 18 is mounted in the bore 13 of the cutting insert, it is intended to act as a double-armed lever under the influence of a pressure member, which here has been given the form of a cylindrical pin 19 threaded into the holder 10 and in that connection been accommodated in a channel 20 directed downwards towards the bottom of the holder, which channel is directed mainly parallel to the recess 13 in the cutting insert, which receives the support pin 18. The pin 18 is L-shaped and has a cylindrical portion 21 at one end intended for engagement with the hole wall of the cutting insert, while a arm 22 formed substantially perpendicularly to the portion 21 is arranged to co-operate with the member 19. The two wedge-shaped end portions 22a and 22b of the arm 22 form between themselves a V-shaped cavity 23 intended to be received in a waist portion in the form of a radial recess 24 developed on the member 19, the ring-shaped upper limiting surface 25 of the recess 24 as well as the upper end surface 26 of the end portions 22a, 22b have an oblique orientation in relation to the centre axis of the bore 20, which receives the member 19. Laterally, the support pin 18 is also provided with a smaller projection 27, which abuts against a surface 28 on the inside of the recess in the holder which receives the support pin 18. The cutting insert is clamped by tightening the member 19 by bringing a suitable key member (not shown) into engagement with a countersunk key recess 19a on the member 19. The member 19 is pressed downwards so that the surfaces 25 and 26 are brought in contact. Continued tightening of the member 19 has the effect that the arm 22 rotates with the projection 27 as the centre so that the arm 22 slides downwards with the projection 27 in contact with the surface 28. The result is that the cylindrical portion 21 pressed with force against the inside of the hole 13 in the cutting insert so that the same is effectively clamped laterally. Thanks to the frictional engagement between the portion 21 and the wall of the hole 13 in the contact portion 29 and the depression caused by the member 19, a downward clamping force is also exerted on the cutting insert. The cutting insert is loosened by turning the member 19 around in the opposite direction. In the alternative embodiment shown in Figs. 6-7, the same clamping principle as previously shown in Figs. 1-4 is retained. As a complement, the insert holder has been equipped here with an upper clamp 30, which is arranged to be clamped by means of a tightening screw 31 through the clamp, the head 32 of which substantially countersunk in its entirety in a bottomed recess in the clamp so that the upper surface 33 of the head 32 becomes situated in the main flush with the top surface of the clamp. In this way, chip flow in the rearward direction is facilitated. It is intended that the front part 34 of the clamp 30 should rest, with the bottom side thereof, against the central elevated plateau 12a of the cutting insert. The upper surface of the cutting insert 12 between the plateau 12a and the cutting edge 12c has the character of an outer plane surface, which transforms mwards towards the cutting insert into a concave rounding upwards to a shoulder 12d serving as chip breaker. This part of the cutting insert, from the edge 12c and into the plateau 12a, should, however, be entirely free from surface contact with the clamp 30, as is best seen in Fig. 7. Thanks to the fact that the cutting insert 12 has been formed with a central elevated plateau 12a, it becomes possible to let the depth of the hole 13 extend upwards a distance corresponding to 40-60 % of the thickness of the cutting insert without this having a negative effect on the strength of the cutting insert, even in the case where the cutting material consists of pure ceramics or mixed ceramics. Under such circumstances, the height h of the plateau 12a should be chosen such that it amounts to 15-40 % of the thickness t of the cutting insert, preferably 20-30 % thereof. According to one embodiment, the bottom side of the front portion of the clamp 30 is formed so that the same becomes slightly curved, or composed of a number of plane surface segments 35, 36, 37, as is shown in Fig. 8, which mutually form an angle of 1-4°. Preferably, the angles Vi and V 2 are equally large, approx. 2°. In this way, the plane surface contact becomes limited to a more distinct plane portion 37 and the requirements of absolute flatness and the maintenance of close tolerances regarding absolute flatness of the bottom side of the clamp portion 34 and plateau surface 12a in its entirety, respectively, no longer need to be critical in any way. The rear part 38 of the clamp 30 intended for contact with the holder 10 has a plane bottom surface 39 for plane surface abutment against a corresponding plane surface 40 of the holder 10. This plane surface 40 should be plane-parallel to the upper cutting plateau 12a. At the same time, the bottom side of the clamp 30 should have a smoothly rounded transition surface 41, which in the forward direction transforms into a plane surface 42, the front portion 42 of which is intended to abut against the cutting plateau 12a.

Claims: Claims 1. Cutting tool, including an insert holder (10) and an cutting insert (12) provided with a hole (13), which insert is arranged to rest against a base surface (11) in an insert seat in the front portion of the insert holder, a substantially L-shaped support pin (18) being received in the insert holder and arranged to be received with one arm thereof in the hole (13) of the cutting insert and with the second arm (22) thereof being actuated by a pressure generating member (19), at the tightening of which, the cutting insert is clamped downwards against the base surface (11), characterized in, that a) the hole (13) in the cutting insert is a blind hole, and b) that the end portion of the second arm, arranged substantially perpendicularly to the arm received in the hole (13), is formed with two wedge-shaped portions (22a, 22b) which between themselves form a V-shaped cavity (23) arranged to partly enclose a waist portion (24) which is more slender in relation to the rest of the member (19). 2. Cutting tool according to claim 1, characterized in, that the length extension of the hole (13) in the cutting insert (12) equals 40-60 % of the thickness (t) of the cutting insert (13). 3. Cutting tool according to claim lor2, characterized in, that the height (h) of the central plateau (12a) of the cutting insert (12) amounts to 15-40 %, preferably 20-30 % of the thickness (t) of the cutting insert. 4. Cutting tool according to any one of claims 1-3, characterized in, that the upper end surface (26) of the wedge-shaped end portions (22a, 22b) has an oblique plane surface contour for co-operation with the member (19) in order to come into engagement with a corresponding oblique surface (25) of the waist portion (24) of the member (19) during clamping. 5. Cutting tool according to any one of claims 1-4, characterized in, that the bottom side on the front portion of the clamp (30) is composed of a number of plane surface segments (35, 36, 37), which mutually form an angle of 1-4°, of which one segment (37) forms a plane surface contact with the elevated cutting plateau (12).

Inventors: ISAKSSON ROBERT, SETO YUSUKE, ISAKSSON, ROBERT, SETO, YUSUKE
Applicants: ISAKSSON ROBERT, SANDVIK AB, SETO YUSUKE, ISAKSSON, ROBERT, SANDVIK AKTIEBOLAG, SETO, YUSUKE
Application year: 2001
Main classification: B23B27
IPC codes: B23B27