GB2161405A

GB2161405A - Toolholder for a tool, in particular a rotating tool, with an axial adjusting device

Info

Publication number: GB2161405A
Application number: GB08515979A
Authority: GB
Inventors: Otto Eckle; Walter Roser
Original assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Current assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Priority date: 1984-07-10
Filing date: 1985-06-24
Publication date: 1986-01-15
Also published as: DE8420617U1; IT8521391A0; SE8503414L; GB2161405B; GB8515979D0; IT1200664B; FR2567432A1; SE8503414D0; JPS6133805A; CH668373A5

Abstract

A toolholder (1) is adjustable by a nut (4) and is biassed inwardly of a connecting part (2) by means of a spring (21). A groove and tongue connection (22, 24) is provided between the connecting part (2) and the shank (11). Moreover, a setscrew (27) acting on the shank (11) is provided. <IMAGE>

Description

SPECIFICATION Toolholder for a tool, in particular a rotating tool, with an axial adjusting device The invention relates to a toolholder for a tool, in particular a rotating tool, with an axial adjusting device, having a connecting part which has a connecting shank or the like at one end thereof and is provided with a fitting bore coaxial with the axis of the connecting shank at its other end, a tool carrier having a tool receptacle at one end thereof and provided at its other end with a cylindrical shank mounted to be axially movable in the fitting bore and which has a fine thread in its front zone adjacent the tool receptacle, a setting nut which can be screwed on the fine thread and is supported against the front face of the connecting part surrounding the fitting bore, a groove and tongue connection between the connecting part and the cylindrical shank, and at least one setscrew acting on an inclined surface extending obliquely with respect to the shank axis, the setscrew being screwable in a radially extending thread of the connecting part.

Such known toolholders are also described as "setting sleeve receptacles" and are frequently designed in accordance with DIN 6327 or 55058. After loosening the setscrew, the tool carrier can be shifted in the axial direction with respect to the connecting part by turning the setting nut. In this process, an axial adjustment of the tool carrier is possible only in one direction, namely away from the connecting part. If it is desired to adjust, the tool carrier in the opposite direction, i.e. towards the connecting part, during which the cylindrical shank moves further into the fitting bore, this can only take place by pressing on the free end of the tool carrier or else of the tool arranged therein.

This is troublesome, however, and also leads to setting inaccuracies. Since the fine thread between the setting nut and the shank is not subjected to load during the adjustment, the thread turns may, bear now against one end and now against the other flank of the trapezoidal thread. If axially directed forces then act on the tool during machining, the tool carrier may shift by the thread play, because the setscrew is not suitable for transmitting rather large axial forces. Due to the shifting of the tool carrier, the tool previously set to a certain axial position changes its position, whereby the machining accuracy suffers.Tool holders of the kind described are frequently needed, in fact, when tools must be set in a certain position in relation to the machine tool or else in relation to other tools, thus, for example, on multiple-spindle drilling heads, in transfer lines and also in machining centres, for example, when blunt tools are exchanged for fresh tools. Moreover, the known toolholder has the disadvantage that the setting nut may eaily loosen because of the lacking or inadequate gripping or locking action of the fine thread, so that it loses its supporting action in the axial direction and the tool may also shift unintentionally over a rather large distance.

The problem underlying the invention is to provide a toolholder of the kind mentioned at the beginning for a tool, in particular a rotating tool, with an axial adjusting device, which toolholder, along with small over-all dimensions, makes exact and sensitive adjustment of the tool carrier possible, in which the tool carrier does not change position in any circumstances under working conditions and which therefore exhibits a high working accuracy.

According to the invention, this is achieved in that the cylindrical shank has a coaxial through bore at its free end and a longitudinal bore with a larger diameter following thereon, a screw with a head is arranged in the longitudinal bore, the shank of the screw extending through the through bore and the screw being screwed into a thread in the rear end of the fitting bore, and a pressure spring arrangement which loads the cylindrical shank continuously towards the rear end of the fitting bore is provided between the screw head and an annular shoulder provided between the through bore and the longitudinal bore.

The invention therefore starts from the idea of disposing between the receiving part and the tool carrier a spring arrangement which continuously loads the tool carrier towards the receiving part and thereby presses the setting nut against the front face of the connecting part in every state of operation, and therefore also when the tool carrier is adjusted, as a result of which the fine threads of the setting nut and shank are always mutually locked or clamped in the same direction. This has several advantages. In the first place, the adjustment of the tool carrier and consequently of the tool is substantially facilitated. On rotation of the setting nut in one direction, the tool carrier is shifted away from the connecting part in opposition to the force of the spring under the action of the setting nut.On rotation of the setting nut in the other direction, the spring arrangement draws the tool carrier automatically into the connecting part.

In every case, the setting nut remains pressed against the front face of the connecting part and the flanks of the fine threads of the setting nut and the shank also remain in abutment in one direction, in which they also bear against one another under the action of machining forces. Owing to this nature of the locking of the thread in itself and of the setting nut with respect to the connecting part, the tool and the tool carrier cannot change position even under high axial forces. Since the setting nut is constantly pressed against the front face and, moreover, additional frictional forces also occur due to the locking or clamping of the fine thread, the setting nut cannot loosen even under the effect of vibration which may arise during machining, so that the exact setting of the tool is maintained in every case.Due to the capacity for exact setting and the maintenance of the setting under all working conditions, the novel toolholder makes a high working accuracy possible. In addition, the toolholder has small over-all dimensions, in particular in the axial direction, as a result of which the stability and thereby likewise the machining accuracy are enhanced.

Advantageous developments of the invention are characterised in the sub-claims.

The invention is described in detail hereinafter with reference to two embodiments shown in the drawing, in which: Figure 1 is a longitudinal section of a first embodiment; Figure 2 is a partial view in the direction II of Figure 1; Figure 3 is a partial section on the line Ill-Ill in Figure 1; Figure 4 is a longitudinal section of a second embodiment.

The toolholder 1 consists essentially of two main parts, namely the connecting part 2 and the tool carrier 3 mounted to be movable therein. The connecting part 2 is provided at one end with a connecting shank 4 which may be shaped in any desired manner. The connecting shank 4 serves to connect the toolholder 1 to a machine tool spindle 5 or to another toolholder. A connecting device in accordance with German Patent Specification 31 08 439 may be provided for connecting the shank 4 to the machine tool spindle 5. This device consists of a locking pin 7 slidably mounted in a transverse bore 6 in the shank 4, the locking pin having a conical recess at one of its ends and a conical shoulder at its other end. These parts of the locking pin 7 cooperate with two clamping screws 8 which clamp the tool holder 1 securely to the machine tool spindle.

The connecting part 2 moreover has at its other end a fitting bore 9 which is surrounded by an annular front face 10 at the free end of the connecting part 2. The cylindrical shank 11 of the tool carrier 3 is movably mounted in the fitting bore 9 with such a small play that an axial adjustment is only just still possible. The tool carrier 3 has at its end remote from the shank 11 a tool receptacle 12 which may likewise again be shaped in any desired manner. In the embodiment shown in Figure 1, the tool receptacle 12, in accordance with German Patent Specification 31 08 439, is formed similarly to the receptacle of the machine tool spindle 5, for which reason it is superfluous to give a description again. In its zone adjacent the tool receptacle 12, the shank 11 has a fine thread 13 on which a setting nut 14 can be screwed.For actuating the setting nut 14, it is provided with a plurality of radial bores 15 into which a corresponding key can be inserted. The setting nut 4 bears against the front face 10 by means of its annular surface 14a The shank 11 is moreover provided with a longitudinal bore 16 and, at its free, inner end, has a through bore 17 which has a smaller diameter than the longitudinal bore 16. In this way, an annular shoulder 18 is formed between the longitudinal bore 16 and the through bore 17. In the longitudinal bore 16 there is arranged a coaxial screw 19 the shank 19a of which extends through the through bore 17 and is screwed into a thread 20 in the rear end 9a of the fitting bore 9. A pressure spring arrangement, suitably in the form of a plurality of cup springs 21, is provided between the head 19a of the screw 19 and the annular shoulder 18.This pressure spring arrangement 21 loads the cylindrical shank 11 continuously towards the rear end 9a of the fitting bore 9. In order to produce a twistproof connection between the tool carrier 3 and the connecting part 2, the cylindrical shank 11 is provided with a longitudinal groove 22. The connecting part 2 has a radially extending thread 23 into which a retaining screw 24 is screwed. The inner end of the retaining screw 24 has two flats 24a Figure 3) which are diametrically opposite with respect to the screw axis S and extend parallel to one another and parallel to the screw axis S, and whose distance apart corresponds exactly to the width B of the groove. In this way, the flats 24a bear with an exact fit against the side faces 22a of the longitudinal groove 22.Due to this exactly fitting connections, which is simple to produce, any torque can be reliably transmitted without any twisting play.

The longitudinal groove 22 moreover has in a partial zone thereof an inclined surface 25 which is so sloped with respect to the common axis A of all the parts that it encloses an acute angle with this axis and moves away from the axis A towards the free end of the shank 11. The retaining screw 24 has a concentric internal thread 26 into which a setscrew 27 can be screwed, the setscrew being supported against the inclined surface 25 by means of a conical shoulder 27a . When the setscrew 27 is tightened, it prevents any shifting of the shank 11 away from the rear surface 9a . It moreover acts on the shank 11 in the same direction as the cup springs 21.

In order to produce as stable and precisely fitting a connection as possible between the connecting part 2 and the tool carrier 3, it is appropriate for the fitting bore 9 and that part of the cylindrical shank 11 which engages in the fitting bore 9 to be about as long as or, at the most, one and a half times as long as, the diameter. With this conformation, the fitting bore 9 and also the shank 11 can be produced so that they are exactly cylindrical, and have a precise tolerance. The setting distance possible by means of the fine thread 13 and the setting nut 14 has been deliberately kept comparatively small to maintain rigidity and accuracy, because as a rule only a comparatively small range of axial adjustment is required for making it possible to set the tools in the axial direction with respect to one another or in relation to the machine tool. Much more important is very precise setting and very rigid connection between the receiving part 2 and the tool carrier 3, it being moreover important that the position of both parts, once it has been set, does not change under the working conditions arising.

This is chiefly ensured by the spring arrangement 21. This spring arrangement 21 is continuously operative. Even when the setscrew 27 is slackened for a necessary setting of the tool 28, for example a milling cutter, a drill, a reamer, a precision turning tool or the like, the spring arrangement 21 cbntinuously exerts on the shank 11 a force in the direction C which holds the setting nut 14 with its annular surface 14a in constant abut ment against the annular surface 10. Because of this, it is possible to adjust the tool carrier 3 sensitively in both axial directions without pressure having to be exerted manually on the tool carrier 3. It is also always ensured that the setting nut 14 bears against the front face 10 under bias.Furthermore, the turns of the fine thread 13 and the turns of the thread of the setting nut 14 are always clamped together in the same direction and in abutment with one another, in which also axially directed machining forces act on the tool carrier 3. After the tool 28 has been set in the axial direction by means of the setting nut 14, the setscrew 27 is tightened again.

In consequence of its conical shoulder 27a , it likewise act in the direction C and prevents the shank 11 moving in the direction opposite to the direction C under any working conditions whatsoever.

Chiefly the cup spring arrangement 21 and in addition also the setscrew 27 prevents the setting nut 14 from loosening, through the constant abutment of the annular surface 14a against the front face 10. In this way, the axial position of the tool 28, once it has been set, is reliably maintained under all working conditions.

As can be seen from Figure 2, the setting nut 14 may be provided at its periphery with a graduated scale 29 which facilitates the setting operation.

According to Figure 4, the tool carrier 3'may also be so designed that it can accommodate a collet chuck 30, 31. So far as the embodiment shown in Figure 4 coincides with the embodiment shown in Figures 1 to 3, the same reference have been employed for parts having the same functions and reference is therefore to be made to the foregoing description as regards the explanation of these references. Tools having a plain shank, such as, for instance, spiral drills, screw taps, countersinks or the like, are to be accommodated by means of the collet chuck 30, 31. Because of the different lengths of such tools with a plain shank and also because of the possibility of more marked wear, a greater adjustment distance in the axial direction may be of advantage. Moreover, it is important that such tools with a plain shank do not either twist or shift in the axial direction in the collet chuck.So that these requirements are wholly satisfied, the longitudinal bore 16 is suitably provided with a fine thread 32 at its end towards the inner end of the collet 30. In the fine thread there can be screwed a supporting nut 33 which advantageously consists of spring steel. The supporting nut 33 has a cross slot 34 widening in the form of a wedge towards the collet 30, the cross slot extending so deeply into the supporting nut 33 that it has only a small thickness left at its base. The shank 35 of the tool 36 to be inserted into the collet chuck 30, 31 is provided with two diametrically opposite flats 35a which are supported on the wedge-shaped surfaces 34a of the cross slot 34. When the coupling nut 31 of the collet 30 is slackened, by turning the tool 36 the supporting nut 33 can also be turned with it and consequently the tool 36 can be coarsely preset in the axial direction. When the coupling nut 31 is tightened, a back pressure is produced towards the supporting nut 33 which spreads it in consequence of the flats 35a and the wedge-shaped surfaces 34a. As a result of this, the supporting nut 33 is secured against further turning and at the same time forms an axial support for the flats 35a of the shank 35 by means of its wedge-shaped surfaces 34a . After this coarse setting has been carried out, the tool 36 can be set in the above- described manner by means of the setting nut 14 after loosening the setscrew 27.

Claims

1. Toolholder for a tool, in particular a rotating tool, with an axial adjusting device, having a connecting part which has a connecting shank or the like at one end thereof and is provided with a fitting bore coaxial with the axis of the connecting shank at its other end, a tool carrier having a tool receptacle at one end thereof and provided at its other end with a cylindrical shank mounted to be axially movable in the fitting bore and which has a fine thread in its front zone adjacent the tool receptacle, a setting nut which can be screwed on the fine thread and is supported against the front face of the connecting part surrounding the fitting bore, a groove and tongue connection between the connecting part and the cylindrical shank, and at least one setscrew acting on an inclined surface extending obliquely with respect to the shank axis, the setscrew being screwable in a radially extending thread of the connecting part, characterised in that the cylindrical shank (11) has a coaxial through bore (17) at its free end and a longitudinal bore (16) with a larger diameter following thereon, a screw (19) with a head (19a ) is arranged in the longitudinal bore (16), the shank (19a ) of the screw extending through the through bore (17) and the screw being screwed into a thead (20) in the rear end (9a ) of the fitting bore (9), and a pressure spring arrangement (21) which loads the cylindrical shank (11) continuously towards the rear end (9a of the fitting bore (9) is provided between the screw head (19b ) and an annular shoulder (18) provided between the through bore (17) and the longitudinal bore (16).

2. Toolholder according to claim 1, characterised in that the pressure spring arrangement consists of a plurality of cup springs (21).

3. Toolholder according to claim 1 or 2, characterised in that the cylindrical shank (11) has a longitudinal groove (22) and the connecting part (2) has a radially extending thread (23) into which a retaining screw (24) is screwed, the inner end of the retaining screw having two flats (24a ) which are diametrically opposite with respect to the screw axis (S) and extending parallel to one another and parallel to the screw axis (S) and whose distance apart corresponds to the width (B) of the groove, so that they bear with an exact fit against the side faces (22a ) of the longitudinal groove (22).

4. Toolholder according to claim 3, characterised in that the retaining screw (24) has a concentric internal thread (26) into which a setscrew (27) provided with a conical shoulder (27a ) can be screwed.

5. Toolholder according to claim 1 or 2, characterised in that the fitting bore (9) and that part of the cylindrical shank (11) which engages in the fitting bore (9) are about as long as, up to one end and a half times as long as, the diameter of the shank (11).

6. Toolholder according to claim 1 or 2, characterised in that the tool carrier (3' ) has a collet chuck (30, 31) as a tool receptacle and the longitudinal bore (9) is provided with an internal thread (32) at the inner end of the collet chuck (30, 31), a supporting nut (33) having a cross (34) widening in the form of a wedge towards the collet chuck (30, 31) can be screwed in the internal thread (32), and the shank (35) of a tool (36) to be inserted in the collet chuck (30, 31) is provided with diametrically opposite flats (35a ) which are supported on the wedge-shaped surfaces (34a ) of the cross slot (34).

7. Toolholder according to claim 6, characterised in that the supporting nut (33) consists of spring steel.

8. Toolholder according to claim 6 or 7, characterised in that the thread of the supporting nut (33) and the associated internal thread (32) of the longitudinal bore (9) are fine threads.

9. A toolholder substantially as described hereinbefore with reference to and as shown in Figures 1 to 3, or Figure 4 of the accompanying drawings.