ARRANGEMENT IN CUTTING TOOL

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method for presetting a cutter of a cutting tool with respect to a tool frame. The invention also relates to a tool comprising a frame and at least one cutter, the cutter comprising at least one cutting edge. The tool is provided with a mechanical adjustment element, the relative positions of whose adjustment components are adjusted, and thus the cutter may be brought to a desired position with respect to the tool frame. After the adjustment the cutter is locked to its adjusted position. The invention further relates to a cutter module, which comprises an adjustment element for presetting the cutter.

[0002] The object of the invention is defined in greater detail in the preambles of the independent claims of the application.

[0003] Different machine tools are used in machining, such as lathes, milling machines, horizontal boring and milling machines, drilling machines, planes, slotting machines and machining centres. Depending on the machine tool, an object being machined is arranged to move in the cutting direction with respect to the tool fixed to the machine tool, or vice versa. The tool comprises one or more cutters having a cutting edge for detaching material from the object being machined. The aim is to preset the cutter in such a manner that it may achieve the required dimensional accuracy. To preset the cutter, a screw or a similar adjustment element is typically used, by means of which the cutter is brought to a desired position with respect to the tool frame or the tool holder of the tool. A problem with current tools is that mechanical adjustment elements always have some clearance, wherefore it is difficult to accurately preset the cutter. Clearances of the adjustment element may be diminished by improving the manufacturing accuracy of the mechanical structure, but, in order to function, the element always requires some kind of clearance. In addition, a better manufacturing accuracy means that manufacturing methods which differ from the conventional ones must be used, which increases the manufacturing costs.

BRIEF DESCRIPTION OF THE INVENTION

[0004] It is an object of the present invention to provide a novel and improved method for improving the accuracy of a cutting tool, a tool, and a cutter module.

[0005] The method of the invention is characterized by supplying the pressure of a pressure medium along the pressure channel to a pressure space in the adjustment element; acting on a working pressure surface of the first adjustment component by means of the pressure of the pressure medium to produce a first force in the first direction; acting on a working pressure surface of the second adjustment component by means of the pressure of the pressure medium to produce a second force in the second, opposite direction; and pressing the mating surfaces of the adjustment components against one another by means of the first force and the second force to remove clearances from the mechanical structure of the adjustment element.

[0006] The tool of the invention is characterized in that the adjustment element comprises at least one pressure space to which the pressure of a pressure medium may be supplied from a pressure channel; that each adjustment component comprises at least one working pressure surface arranged in said pressure space; and that the pressure of the pressure medium is arranged to produce in the adjustment components against one another forces, the directions of which are opposite, the mating surfaces of the adjustment components being arranged to be pressed against one another and thus to remove a clearance from the mechanical structure of the adjustment element.

[0007] The cutter module of the invention is characterized in that the cutter module comprises: a frame which may be fastened to the frame of the cutting tool; at least one adjustment element for adjusting the position of the insert holder with respect to the frame, the adjustment element comprising: at least one pressure channel; at least one pressure space to which the pressure of the pressure medium may be supplied; at least one limiter which is provided with a working pressure surface in the pressure space and which is connected by means of an intermediate piece to the insert holder; at least one stopper sleeve, against which the limiter is arranged to be set, whereby the axial position of the stopper sleeve is arranged to define the preset adjustment of the cutter; at least one adjustment sleeve arranged between the frame and the stopper sleeve; a first thread between the stopper sleeve and the adjustment sleeve and a second thread between the adjustment sleeve and the frame, the pitches of the first thread and the second thread having different magnitudes; and the pressure of the pressure medium acting in the pressure space being arranged to produce forces between the stopper sleeve and the adjustment

sleeve and acting in the opposite directions, and forces between the adjustment sleeve and the frame and acting in the opposite directions, whereby the side surfaces of the first thread and the second thread may be pressed tightly against one another by means of the pressure of the pressure medium.

[0008] The basic idea of the invention is that the pressure of a pressure medium is supplied to an adjustment element, which produces on the working pressure surfaces of the adjustment components at least two forces acting in the opposite directions. The forces are directed in the adjustment components in such a manner that the mating surfaces of the adjustment components are set tightly against one another, whereupon the mechanical clearances between the adjustment components are removed.

[0009] The invention provides the advantage that by means of the pressure of the pressure medium, the mating surfaces of the adjustment components of the adjustment element are set tightly against one another in the adjustment direction. In a way, the pressure of the pressure medium prestresses the adjustment element by pressing or pulling, whereby the adjustment components are set tightly against one another. In this manner, it is possible to remove the clearances in the structure of the adjustment element. Thus, the accuracy of the adjustment element may be very good, even if its structure comprises the clearances necessary for its function. In addition, the manufacturing tolerances of the adjustment components need not be particularly precise, and thus the adjustment element may be manufactured with conventional techniques. Consequently, the adjustment element may be relatively simple and cheap.

[0010] The basic idea of an embodiment of the invention is that the tool comprises at least one adjustment element, which comprises a differential screw mechanism for presetting the cutter. The differential screw comprises two threads with different pitches. By turning the differential screw around its axis the cutter is made move in the direction of the screw axis with respect to the difference between the pitches of the coarse thread and the finer thread. The differential screw provides the advantage that the preset adjustment may be made very precise without needing to use one thread with a particularly small pitch. It is difficult and expensive to manufacture a thread with a very small pitch and, furthermore, the capability of such a thread to resist load and wear is poor. Due to the differential screw, polished or customized threads

need not be used. The threads of the differentia! screw may be manufactured by using a standard machining technique and standard tolerances.

[0011] The basic idea of an embodiment of the invention is that the cutter module is arranged in a fastening opening transverse to the longitudinal axis of the tool and locked immovably in the longitudinal direction of the opening by means of one or more fastening elements, such as a clamping screw. The fastening opening may be a transversal through hole in the tool frame, or it may be a "blind hole". The application provides the advantage that the cutter module is fixed firmly in its place in the fastening opening, whereby it maintains its dimensional accuracy despite the resultant cutting force. Such a fastening is also easy to use and manufacture. It is also possible to drill a fastening opening in the existing tools for placing the cutter module. The central axis of the fastening opening may form an angle with the longitudinal axis of the tool.

[0012] The basic idea of an embodiment of the invention is that the tool comprises at least one cutter, which may be indexed by moving it with respect to the tool frame. Thus, the cutter has at least a first position and a second position. As the tool is provided with a cutter to be indexed, it may be used for machining several working phases without changing the tool. This saves machine time. In addition, a smaller number of different tools are needed, which means that the tool magazine of the machine tool may be smaller.

[0013] The basic idea of an embodiment of the invention is that the indexation of the cutter to be indexed is carried out by using the pressure of the pressure medium.

[0014] The basic idea of an embodiment of the invention is that the stopping of the cutter to be indexed in the outermost position, i.e. the cutting position, is adjusted in the preset adjustment by using a screw mechanism.

[0015] The basic idea of an embodiment of the invention is that the locking of the cutter to be indexed to the indexed position is carried out by using the pressure of the pressure medium.

[0016] The basic idea of an embodiment of the invention is that the locking of the cutter to be indexed to the indexed position is carried out with the same pressure medium simultaneously with the removal of mechanical clearances of the adjustment element.

[0017] The basic idea of an embodiment of the invention is that the pressure medium is a flushing fluid, which may be supplied along a flushing medium channel of the tool to the cutter module. The flushing fluid may be

supplied to the tool through a spindle of the machine tool or alternatively through a tool slide, tool seat, etc. In this case, no essential changes need be done in the machine tool or its control.

[0018] The basic idea of an embodiment of the invention is that the insert holder is an elongated object, in which a replaceable insert piece is fixed to the region of one end. The insert holder is further arranged transversally to the cutter module and it may have a predefined angular position with respect to the longitudinal axis of the cutter module.

BRIEF DESCRIPTION OF THE INVENTION

[0019] Some embodiments of the invention are explained in greater detail in the attached drawings, in which

Figure 1 schematically shows a side view of a chip removing machine tool,

Figure 2 schematically shows a cutting tool arranged in a rotating spindle of a machine tool,

Figure 3 schematically shows a cutting tool and illustrates a preset adjustment of its cutter,

Figure 4a schematically shows a sectional view of a cutter module comprising a screw mechanism for presetting a cutter,

Figure 4b schematically shows a sectional view of a detail of a screw mechanism according to Figure 4a after the removal of clearances by using the pressure of a pressure medium,

Figure 5a schematically shows a sectional view of a second cutter module comprising a differential screw mechanism for presetting a cutter,

Figure 5b schematically shows a sectional view of details of the screw mechanism according to Figure 5a after the removal of clearances between the screw components by using the pressure of a pressure medium,

Figure 6 schematically shows a sectional view of a free end of a cutting tool, the tool being provided with a cutter module comprising a cutter to be indexed and means for removing clearances from an adjustment mechanism,

Figure 7 schematically shows a side view of the tool according to Figure 6,

Figure 8 schematically shows a sectional view of the cutter module according to Figure 6 in a situation where the cutter is brought back to its innermost position,

Figure 9a schematically shows a sectional view of outermost screw components of an adjustment element belonging to the cutter module according to Figures 6 and 8,

Figure 9b schematically shows a detail of the mating surfaces of the outermost screw components,

Figure 10a schematically shows a sectional view of the inner screw components of the adjustment element belonging to the cutter module according to Figures 6 and 8,

Figure 10b schematically shows a detail of the mating surfaces of the inner screw components, and

Figure 11 schematically shows a sectional view of a tool according to the invention, provided with a transversal fastening opening, in which a cutter module according to the invention is arranged.

[0020] For the sake of clarity, some embodiments of the invention are simplified in the figures. Like parts are denoted by like reference numerals in the figures.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

[0021] Figure 1 shows a lathe, which is a typical chip removing machine tool. In a lathe, a tool 1 is usually in its place in a tool holder 2, and a workpiece 3 is rotated in a spindle 4 of the lathe. Feed motion is implemented by moving a slide 5 or the like. A flushing fluid may be supplied from a chamber 6 to the tool 1 in order to flush the chips removed with the tool 1 and to cool the workpiece 3 and a cutter 7 of the tool 1. The invention may be applied in lathe tools.

[0022] Figure 2 shows a cutting tool 1 arranged in a rotating spindle 4 of a machine tool, such as a machining centre or a horizontal boring and milling machine. The invention may be applied in rotating tools, such as drilling tools, broaching tools, cutter heads, etc. The tool 1 may comprise one or more cutters, which remove material from the workpiece 3. The tool 1 may also have one or more cutters to be indexed, which may be indexed to a cutting position when the cutter is used for cutting and, correspondingly, to an idle position when the cutter is not used for cutting. An example of this is a groove 8 in the workpiece according to the figure, which may be done with the cutter 9 to be indexed after the inner hole 10 is first broached with a fixed cutter 11.

[0023] Figure 3 illustrates a currently used arrangement for presetting a cutter 11. In this case, it deals with a drilling tool 1. For the sake of clarity, the figure shows a strong simplification of an insert piece 12, an insert holder 13 and adjustment elements 14. The adjustment elements 14 may comprise an adjustment screw 15 or a similar element, by which the insert holder 13 may be moved in such a manner that the outermost part of the cutter 11 can be placed at a desired distance L from the tool frame 16. A preset adjustment thus adjusts the reach of the cutter 11. After the adjustment the insert holder 13 may be locked to a preset position by means of a clamping screw 17. The preset adjustment may take into account, for instance, deviations of the measures and shape of the insert pieces 12 as well as the wear of the insert pieces 12.

[0024] Figure 4a shows a cutter module 18 of the invention, which may comprise a frame 19, a sleeve 20 and an adjustment screw 15. Such a cutter module 18 may be arranged as one entity at a fastening point in the tool 1 , and thus the module may be detached and replaced easily. The cutter 11 may comprise an insert holder 13, to which a replaceable insert piece 12 with one or more cutting edges may be fastened by a screw or another fastening element. Alternatively, the insert piece may be fixedly fastened to the holder or a cutting edge is provided directly in the cutter. The insert holder 13 may be fastened to the front part of the sleeve 20 by means of a screw, for instance. The sleeve 20, .for its part, may be arranged in an opening 21 of the frame 19 in a sliding manner. Furthermore, the inner hole 22 of the sleeve 20 may be provided with an internal thread 23 in such a manner that the external thread 24 of the adjustment screw 15 may be turned into said internal thread 23. By turning the adjustment screw 15 in the direction B by means of an adjusting wheel 25, for instance, the sleeve 20 and the cutter 11 fastened thereto can be moved in the direction A, whereby the cutter 11 may be preset as desired. Rotation of the sleeve 20 around its axis may be prevented by means of a suitable shape locking, a key 26 or some other machine element. The cutter module 18 may further comprise a pressure space 27, to which the pressure of the pressure medium may be supplied from a pressure channel 28. The pressure medium may be, for instance, a flushing fluid or air. The pressure medium may be supplied from a pressure source 29, such as a pump, through an adjustment element 30, such as a valve, to the pressure channel 28 in the tool 1. The required seals are located between the sleeve 20 and the frame 19 as well

as between the adjustment screw 15 and the frame 19. The sleeve 20 comprises at least one first working pressure surface 31 and the frame 19 comprises, correspondingly, at least one second working pressure surface 32, the pressure of the pressure space 27 acting on the working pressure surfaces 31 , 32. The pressure which acts on the first working pressure surface 31 tends to push the sleeve 20 by means of a first force F1 to the left in the figure, and, accordingly, the pressure which acts on the second working pressure surface 32 tends to push the frame 19 by means of a second force F2 to the right in the figure. Due to the forces acting in the opposite directions, the clearances between the internal thread 23 of the sleeve 20 and the external thread 24 of the adjustment screw 15 are removed. A full pressure may always be supplied to the pressure space 27, except during the presetting. Moreover, the pressure locks the preset adjustment by means of friction between the threads 23, 24, and thus no separate locking mechanism is necessarily required to lock the preset adjustment. It may also be possible to feed a pressure lower than the full pressure during the presetting to the pressure space 27 to diminish the clearances of the adjustment mechanism to some extent and thus to facilitate the adjustment measures. A preset adjustment may be carried out in a presetting machine, which may include an option to feed the pressure medium to the pressure space 27 of the cutter module 18 with a desired pressure.

[0025] Figure 4b shows a detail of the adjustment element 14 according to Figure 4a. The first force F1 acts on the sleeve 20 to the left in the figure, and the second force F2 acts on the frame 19 to the right in the figure. Figure 4b shows how the forces F1 and F2 act on the threads 23, 24 between the adjustment components 19, 20 of the adjustment element 14: the forces F1 and F2 pull the threads 23, 24 away from one another, whereby their sides are set tightly against one another.

[0026] Unlike in Figures 4a and 4b, the pressure surfaces may be constructed in such a manner that the first force F1 acting on the sleeve 20 is directed to the right in the figures and the second force F2 acting on the frame 19 is directed to the left in the figures. Thus, the internal thread 23 and the external thread 24 are pressed against one another. Compared to Figure 4b, the opposite sides are thus against one another in the threads 23, 24.

[0027] Figure 5a shows a second cutter module 18 provided with a differential adjustment screw 15. The differential screw comprises a fine thread and a coarse thread, and the turning of the screw in the direction B is arranged

to produce an axial movement in the direction A, the magnitude of which is proportional to the difference between the pitch of the fine thread and that of the coarse thread. The mechanism allows a very accurate adjustment movement. The adjustment screw 15 may comprise a first external thread 24 to be connected to the internal thread 23 of the sleeve 20 and a second external thread 34 to be connected to a second internal thread 33 of the frame 19. The threads 23 and 24 may be fine threads, and the threads 33 and 34 may be coarse threads, or vice versa. The differential screw also has clearances, which may be removed by using a clearance removal arrangement of the invention similarly as was shown in connection with Figures 4a and 4b.

[0028] Figure 5b shows that the pressure of the pressure medium produces forces F1 and F2 acting in the opposite directions and removing the clearances from both threads of the differential adjustment screw 15.

[0029] Figure 6 shows an application of the cutter module 18 according to the invention, comprising means for indexing the cutter 11. The cutter module 18 may be arranged in a transversal fastening opening 35 in the tool 1 and locked in its place in the frame 16 of the tool 1 by means of one or more locking elements 36, such as a clamping screw. In this case, the fastening opening 35 receives the machining forces directed to the cutter module 18 in the feed direction E, and the locking element 36 prevents the cutter module

18 from moving in the fastening opening 35. For the sake of clarity, the cutter module 18 in Figure 6 is exaggeratedly large with respect to the rest of the tool 1 structure. In addition, the structure of the cutter module is strongly simplified in the figure to advance the clarity. The cutter module 18 comprises an adjustment element 14 based on a differential screw, the operation of which is explained in association with Figure 5a. In this case, the differential adjustment screw 15 may be a sleeve-like object, inside of which a stopper sleeve 38 is connected by means of the first thread 37 and the outer surface of which adjustment sleeve 15 is connected by means of a second thread 39 to the frame

19 of the cutter module 18. The first thread 37 and the second thread 39 have different pitches. The first thread 37 may be a fine thread and the second thread 39 may be a coarse thread, or vice versa. By turning the adjustment sleeve 15 e.g. by means of extension pieces 40a, 40b and a drive wheel 25 around its axis, the stopper sleeve 38 may be preset to a desired position in the axial direction. By adjusting the position of the stopper sleeve 38, a position may be preset, to which the cutter 11 to be indexed extends in the cutting posi-

tion shown in Figure 6. The cutter 11 may be connected to a limiter 42 by means of an intermediate piece 41 , such as a bar. The intermediate piece 41 may be arranged through the stopper sleeve 38 and it may be sealed against the sleeve 38. The limiter 42 may comprise at least one third working pressure surface 43, which is arranged in the pressure space 27. When the pressure of the pressure medium is supplied to the pressure space 27, the pressure acts on the third working pressure surface 43 and pushes the limiter 42, the intermediate piece 41 and the cutter 11 to the left in the figure, i.e. to the cutting position. In other words, the limiter 42 is like a piston, and the intermediate piece 41 may be regarded as a piston rod. At the end of its stroke the limiter 42 is set against the stopper sleeve 38, the axial position of which is preset by the adjustment element 14. The cutter 11 may be supported on the frame 16 of the tool 1 by means of supporting surfaces 44, for instance, or it may be supported in some other manner so that the cutter 11 cannot turn with respect to the axis of the cutter module 18.

[0030] In the cutter module 18 of Figure 6, the indexation of the cutter 11 , the clearance removal of the adjustment element 14 and the locking of the indexed cutter 11 and the locking of the adjustment element 14 may be implemented by supplying the pressure of the pressure medium to the pressure space 27. The feed of the pressure medium may be controlled manually or by means of a control unit 44, which may be controlled numerically.

[0031] The frame 19 of the cutter module 18 may comprise one or more openings 45 or a corresponding pressure channel arranged to be set at the pressure channel 28 in the frame 16 of the tool 1. Between the frame 19 of the cutter module 18 and the adjustment sleeve 15 there may further be a first pressure space 27a, which may to a second pressure space 27b via one or more openings 46 in the adjustment sleeve 15. Essentially the same pressure of the pressure medium thus acts in both pressure spaces 27a, 27b. The pressure P acts on a working pressure surface 47 of the frame 19, thus producing a first force F1 acting to the left in the figure. The pressure also acts on working pressure surfaces 48a, 48b of the adjustment sleeve 15 and produces a second force F2, the direction of which is opposite to that of the force F1. Thus, the forces F1 and F2 remove the clearance from the second thread 39, as can be seen later from Figures 9a and 9b. In addition, the pressure P acts on a working pressure surface 49 of the stopper sleeve 38 and the working pressure surface 43 of the limiter 42, thus producing a third force F3, the direc-

tion of which is opposite to that of the force F2 acting on the adjustment sleeve 15. Thus, the forces F2 and F3 remove the clearance from the first thread 37, as can be seen from Figures 10a and 10b. As the mating surfaces of the threads are pressed tightly against one another due to the forces F1 , F2, F3, friction forces are produced between them, capable of locking the threads immovably. In this case, no separate locking is necessarily required between the thread components.

[0032] When a differential screw similar to that of Figure 6 is utilized in the adjustment element 14, an advantage is that the stopper sleeve 38 does not turn around its axis while the adjustment sleeve 15 is turned, but holds its position. Furthermore, because the cutter 11 is prevented from turning, the relative positions of the limiter 42 and the stopper sleeve 38 with respect to the longitudinal axis of the cutter module 18 are maintained regardless of the adjustment measures. Thus, potential inaccuracies and form errors of the mating surfaces do not affect the accuracy of the preset adjustment.

[0033] The tool 1 shown in Figures 6 and 7 is a multipurpose tool comprising one or more roughing cutters 50a and 50b, which may be used for broaching the hole in the feed direction E1 to have the diameter d1 , the cutter 1 further comprising one or more cutter modules 18, which comprises/comprise a cutter 11 to be indexed and by which the roughed hole may be finished in the feed direction E2 to have the diameter d2.

[0034] Figure 8 shows the cutter module 18 in a situation where the pressure of the pressure medium does not affect in the pressure spaces 27a and 27b. In this case, the entity composed of the limiter 42, the intermediate piece 41 and the cutter 11 may be transferred to its innermost position by means of a suitable return element 51 , such as a spring element. It is also possible to arrange some other return element, such as an element operated with a pressure medium, for the parts that are moving during the indexation. When the pressure P is regenerated, the pressure of the pressure space 27b acts on the working pressure surface 43 of the limiter 42 and its opposite surface. Since the surface area of the working pressure surface 43 is larger, the limiter 42 moves against the stopper sleeve 38 due to the force of the pressure medium. Figure 8 also shows, on the outer surface of the cutter module 18, a locking groove 52 in which the locking element 36 may be arranged.

[0035] Figures 9a and 9b illustrate the removal of clearances from the second thread 39 between the frame 19 and the adjustment sleeve 15.

Since the forces F1 and F2 act in the opposite directions, the mating surfaces of the threads of the adjustment components are set tightly against one another, as can be seen from Figure 9b.

[0036] Figures 10a and 10b, for their part, illustrate the removal of clearances from the first thread 37 between the adjustment sleeve 15 and the stopper sleeve 38. Since the forces F2 and F3 act in the opposite directions, the mating surfaces of the threads in the adjustment components are tightly set against one another, as can be seen from Figure 10b.

[0037] The tool 1 shown in Figure 11 is provided with an oblique transversal fastening opening 35, in which the cutter module 18 according to the invention is arranged. The cutter module 18 may be arranged in the fastening opening extending through the tool 1 , whereby the preset adjustment may be carried out from the tool's 1 side that is opposite with respect to the cutter 11. It is thus easier to position the adjusting wheel 25 and similar elements to the tool 1. It is also easier to carry out the preset adjustment when the adjustment elements may be used from the side that is opposite to the cutter 11. One or more extension pieces 40a, 40b may be connected to the cutter module 18 according to the size of the tool 1.

[0038] It is further to be noted that the tool 1 of the invention may be provided with two or more cutter modules 18 according to the invention. Instead of the screw mechanism, the adjustment element 14 may further comprise some other adjustment mechanism suitable for the purpose, such as an eccentric, key, etc. However, it is to be noted that other mechanical adjustment elements also comprise clearances, which may be removed by arranging the pressure space 27 in connection with the adjustment element 14 and supplying the pressure of the pressure medium to the working pressure surfaces of the adjustment components in such a manner that forces in the opposite directions act on the adjustment components, due to which the mating surfaces of the adjustment components are set tightly against one another.

[0039] In some cases, features disclosed in this application may be applied as such, despite the other features. On the other hand, features disclosed in this application may be used to form various combinations, if necessary.

[0040] The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.