Cutting tool

Abstract: A cutting tool comprises, on one hand, a front part (4) for a cutting insert (5) and, on the other hand, a rear part (6), which is detachably secured in a holder, as well as a plurality of nozzles which are supplied with high pressure cooling liquid via a duct system (21) inside the tool and of which at least a first one (13) has the purpose of spraying a jet (14) towards the area of a upper surface on the cutting insert (5) with the purpose of forming a hydraulic wedge between the upper surface of the cutting insert and a chip (17) emanating from a workpiece in order to lift and distance the chip from the cutting insert. According to the invention, a second nozzle (15) co-operates in pair with said first nozzle (13) in order to direct a second high pressure cooling liquid jet (16) towards a point at a level above the cutting insert (5) in order to impinge on the chip (17) at a distance from the cutting insert and thereby apply a mechanical force on the chip which aims to deflect the chip in an upwards/backwards direction.

Description: A cutting tool comprising in combination the features of the preamble of claim 1 is known from US-A-5388487. This invention relates to a cutting tool including a tool body with, on the one hand, a front part for a cutting insert and, on the other hand, a rear part, which can be detachably secured in a holder in an appurtenant machine, as well as a plurality of nozzles, which are supplied with pressurized cooling liquid from an external liquid supply source via a duct system inside the tool body, and of which at least a first one has the purpose of spraying a high pressure cooling liquid jet towards the area of an upper surface on the cutting insert with the purpose of forming an hydraulic wedge between the upper surface of the cutting insert and a chip emanating from a workpiece in order to lift and distance the chip from the cutting insert. General Background of the Invention and Prior Art The practice of cooling not only the cutting inserts of cutting tools, e.g. tools for turning, but also the workpiece commonly consisting of metal which is to be machined by the tool as well as the chip which is cut from the workpiece has long been known. A fundamental aim in today's technology for cutting or chip removing machining is to enable use of as high a pressure as possible in the cooling liquid and to supply this in the form of one or more thin jets held tightly together which generally are directed towards the cutting insert and the chip released thereby. The higher the pressure which may be used in the liquid jet, the greater are the possibilities to use the liquid jet, in an advantageous way, not only for pure cooling, but also to mechanically affect the chip released from the workpiece (by applying a force from the jet to the chip), more precisely with the purpose of breaking this into smaller pieces and/or guiding the chip away from the tool in a controlled way. Among those skilled in the art, there are different opinions as to what, in this connection, is to be regarded as low and high liquid pressure, respectively. Generally, the classification can, however, be made in following intervals: Low pressure < 10 bar, Intermediate pressure 10-100 bar, and High-pressure > 100 bar. On older cutting tools, cooling always took place using low pressure cooling liquid, while cutting tools according to somewhat more recent technology have worked with intermediate pressure cooling liquid. In the more modem technology, liquid pressure of hundreds of bar are sometimes used. When the cutting insert on a cutting tool during, for instance, turning cuts a chip free from a rotating workpiece, commonly of metal, considerable amounts of heat are developed. The cutting of the chip is carried out in a primary shear zone, which is developed in a peripheral portion of the workpiece and extends obliquely upwards/backwards from the cutting edge of the cutting insert. By virtue of the high temperatures which are developed not only in the chip and the workpiece, but also in the cutting insert, the chip separated in the primary shear zone may not slide forward frictionless and without resistance along the upper surface of the cutting insert. On the contrary, the very hot chip adheres to the upper surface of the cutting insert along a certain contact length in a course of events, which has similarities to welding. The contact length may, depending on, for instance, the material in the workpiece, vary between tenths of a millimetre and approximately one millimetre backwards from a support zone near the cutting edge. In this connection, the hot material adheres powerfully as a thin layer above which the real separation of the chip takes place by shearing in a secondary shear zone (frequently denominated weld zone). After this, a so called friction zone follows along which the chip is in strong friction contact with the cutting insert before the same leaves the cutting insert. In order to facilitate the separation of the chip from the cutting insert, most often some form of chip deflector is arranged; e.g. in the form of beads or projections on the upper surface of the cutting insert and/or in the form of special elements on the tool, in particular clamps for retention of the cutting insert. The modern high pressure cooling liquid technology aims at bringing the cooling liquid jet into the substantially wedge-shaped space which is provided between the underside of the chip and the upper surface of the cutting insert at the point where the chip is distanced initially from the cutting insert. The intention is to form a so called hydraulic wedge between the chip and the upper surface of the cutting insert, which wedge should contribute to breaking up the chip and, as far as possible, reducing the contact length of the chip along the cutting insert. A significant aim with introducing high pressure cooling liquid between the chip and the cutting insert is, of course, also to cool these as effectively as possible. A cutting insert intended for chip removing machining is previously known from WO 99/39853, which cutting insert has a chip deflector in the form of a number of small projections which are mutually spaced-apart by means of grooves in which high pressure cooling liquid may be injected with the purpose of shortening the contact length of the chip along the upper surface of the cutting insert. By means of these grooves, the high pressure cooling liquid may better penetrate under the chip at the same time as the surrounding projections aim at breaking up the chip in order to force the chip to deflect upwards/backwards as far as possible. Although this known cutting insert considerable improves the cooling and chip breaking effect in relation to older technology, no radical deflection of the chip in an upwards direction is effected. On the contrary, the chip tends to leave the upper surface of the cutting insert in a comparatively flat angle. This is something that in practice means that the chip may develop as a tangled skein. Objects and Features of the Invention The present invention aims at obviating the above-mentioned shortcomings in the previously known technology and at providing a cutting tool with an improved ability to control the chip, which has been cut free. Therefore, a primary object of the invention is to provide a cutting tool, which not only guarantees a good cooling but also an improved chip breaking ability. According to the invention, the above-mentioned 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 Drawing In the drawing: Fig 1 is a perspective exploded view showing a cutting tool according to the invention adjacent to a partially outlined machine for chip removing machining, Fig 2 is a partial sectioned side view showing the tool during machining of a workpiece, and Fig 3 is a cross-section A-A in fig 2. Detailed Description of a Preferred Embodiment of the Invention In the drawing, a cutting tool is generally designated 1, which in the example is included in a so-called modular tool system and co-operates with a clamping unit 2. This clamping unit is fixedly assembled in a machine 3 outlined only partially, which is represented by a portion of a turret plate. The cutting tool 1 includes a front part 4 with a detachable cutting insert 5, which in the example is in the form of a round cutting insert. A rear part 6 of the cutting tool is in the shape of a male element, which is insertable in a cavity 7 in the clamping unit 2. The coupling between the cutting tool and the clamping unit may advantageously be of the COROMANT CAPTO® type, the male element 6 as well as the cavity 7 having a polygonal, although softly rounded cross-section shape, at the same time as the same tapers in the backward direction. In the area of the interior of the cavity 7, there is a not shown clamping mechanism which may be brought to engagement with coupling means (not shown) inside the male element 6 with the purpose of, on the one hand, pulling in and fixing the male element in the cavity during assembly, and, on the other hand, ejecting the same at dis-assembly. The envelope surface on the male element 6 is designated 8, while the interior surface defining the cavity 7 is designated 9. The front and rear parts 4, 6 of the cutting tool 1 are spaced-apart by a transverse, plate-shaped part 10 on the front side of which a detachable nozzle plate 11 is applied. It should here be pointed out that the parts 4, 6 and 10 are included in an integrated, solid body of metal. The plate 11 is kept fixed against the plate part 10 by means of screws (not shown), which are fastened in holes 12. A plurality of nozzles, of which certain are designated 13, are mounted in the plate 11. These nozzles 13 have the purpose of spraying high pressure cooling liquid jets 14 towards the cutting insert 5, more precisely towards the upper surface of the cutting insert in an area near the cutting edge of the cutting insert. As far as the tool shown in the drawing has been described hitherto the same is in all essentials previously known from disclosed technology, e.g. such as this is represented by WO 99/39852 (filed at the same time as the above-mentioned WO 99/39853). Characteristic of the invention is that the nozzle plate 11 in addition to the first-mentioned nozzles 13 also includes second nozzles 15. Each such second nozzle 15 co-operates in pair with a first nozzle 13. More precisely, the second nozzle 15 in each pair of nozzles should direct a second high pressure cooling liquid jet 16 towards a chip 17 which is released from a workpiece 18 and which is already cooled per se by a first liquid jet 14. In the example according to fig 2, said workpiece is submitted to a turning operation during which the same is brought to rotate. Generally, each second nozzle 15 is placed above a co-operating first nozzle 13, which directs the jet 14 thereof towards the cutting edge of the cutting insert in order to form a hydraulic wedge between the upper surface of the cutting insert and the initially formed chip 17. In this connection, the second nozzle 15 is adjusted in such a way that the appurtenant jet 16 is directed towards a point at a level above the cutting insert in order to meet the chip 17 initially distanced from the cutting insert and thereby applying this a mechanical force which aims to deflect the chip in direction upwards/backwards, as is illustrated in fig 2. In the preferred embodiment shown in the drawing, each second nozzle 15 in the two pairs of co-operating nozzles is placed in the main vertically above the appurtenant first nozzle 13, although it is feasible per se to locate the second nozzle in a point deviating from the vertical plane. Thus, what is essential is that the bore 19 of the nozzle 15 is adjusted in such a way that the jet 16 will meet the chip 17, more precisely in an area on a suitable level above the cutting insert and the hydraulic wedge which is formed by the jet 14. The nozzles 13 as well as the nozzles 15 may, per se , be formed in the way which is described in WO 99/39852, i.e. be re-adjustable in order to enable fine adjustment of the point of impact of the liquid jet in question. However, it is also feasible to use fixed nozzles of simpler type, i.e. nozzles the jet direction of which is set once and for all in connection with the manufacture of the nozzle plate. As may be seen in fig 2, the two nozzles 13, 15 in a co-operating pair of nozzles are connected with a space 20 recessed at the rear side of the nozzle plate 12. High pressure cooling liquid is fed to this space via a duct 21, which at the rear-ends in a port 22. When the male element 6 is fixed in the clamping unit 2, the port 22 is located opposite a port 23 to an analogous duct inside the clamping unit, which duct is positioned in interior surface 9 of the cavity 7. This duct, in turn, is connected in a suitable way to an external cooling liquid supply source, which has the ability to pressurize the cooling liquid with a very high pressure (e.g. within the range of 500-1500 bar, or more). These ports extend radially in order to transmit, between the clamping unit and the male element of the tool, the high pressure cooling liquid in the radial direction with the purpose of avoiding the tool being exposed to axial forces which would tend to eject the tool out of the clamping unit. In the embodiment example shown, the tool includes two pairs of lower and upper nozzles. As may be seen in fig 3, these nozzle pairs are being supplied by one duct 21 each that vent into two spaced-apart collecting spaces 20. In this way, one of the nozzle pairs may be shutdown when the other is operating. However, it is also feasible to connect all nozzles to a common collecting space to which only one liquid duct is drawn. In such cases, all nozzles will simultaneously spray jets towards the cutting insert and the chip, respectively. By guaranteeing spraying according to the invention of not only a first jet for forming an hydraulic wedge between the upper surface of the cutting insert and the chip, but also a second jet with a higher point of impact, the situation is attained where the chip, after having had an advantageously short contact length along the cutting insert, will be deflected upwards/backwards in a considerably more efficient way than in previously known tools. The distinct deflection upwards of the chip contributes in turn to the fact that the chip is deflected inwards to the workpiece to facilitate breaking of the same in smaller pieces. In other words, the emergence of tangled skein of chips, which are difficult to control during practical operation, is counteracted.

Claims: Cutting tool including a tool body with, on one hand, a front part (4) for a cutting insert (5) and, on the other hand, a rear part (6), which is detachably secured in a holder (2) in an appurtenant machine (3), as well as a plurality of nozzles, which are supplied with pressurized cooling liquid from a liquid supply source via a duct system (21) inside the tool body, and of which at least a first one (13) has the purpose of spraying a high pressure cooling liquid jet (14) towards the area of an upper surface on the cutting insert (5) with the purpose of forming a hydraulic wedge between the upper surface of the cutting insert and a chip (17) emanating from a workpiece in order to lift and distance the chip from the cutting insert, characterized in, that a second nozzle (15) co-operates in pair with said first nozzle (13), which second nozzle is arranged to direct a second high pressure cooling liquid jet (16) towards a point at a level above the cutting insert (5) in order to impinge on the chip (17) at a distance from the cutting insert and thereby apply a mechanical force to said chip which aims to deflect the chip in the upwards/backwards direction. Cutting tool according to claim 1, characterized in, that said second nozzle (15) is placed in the main vertically above the first nozzle (13) in a co-operating nozzle pair. Cutting tool according to claim 1 or 2, said nozzles being mounted in a particular plate (11) which is detachably connected to the rest of the tool, characterized in, that said first and second nozzles (13, 15) are connected with a common cavity (20) to which one single duct (21) formed in the tool body leads for supply of cooling liquid to the cavity from an external cooling liquid supply source.

Inventors: LAGERBERG STIG, LAGERBERG, STIG
Applicants: SANDVIK AB, SANDVIK AKTIEBOLAG
Application year: 2000
Main classification: B23B27
IPC codes: B23Q11, B23B27