DE9015969U1 - Tool shank and tool system for machining workpieces, especially metal - Google Patents

Description

Tool shank and tool system for the

machining of workpieces, especially metal

The invention relates to a tool shaft for a cutting tool system, in particular for piercing and/or turning, which ends in spring-loaded opposing clamping jaws that delimit a clamping slot for the use of a cutting tool, for example a cutting edge or chisel. The invention also relates to a cutting tool system with a tool holder with a bore into which a tool shaft, in particular of the type mentioned above, can be inserted and secured by means of a clamping device that is directed towards the bore in the tool holder.

A cutting tool for metal cutting is known (DE utility model 89 01 327.1), in which the hole in the tool holder (called the shaft there) accommodates a turning tool, whose outer diameter must, however, correspond precisely to the inner diameter of the hole. The turning tool is fastened by tightening a clamping screw that crosses the hole. This rests with its head on a wall area of the hole, so that when the clamping screw is tightened, the wall area is pulled against the turning tool in order to clamp it firmly in the hole. In another known metal cutting tool (EP 0 264 642 Al), the clamping screw is moved against a specific support surface on the turning tool via an internal thread that leads radially to the hole in order to clamp it firmly. Here, too, the turning tool and the hole must each be designed with a low fit tolerance or a high fit accuracy in order to ensure a

machining to achieve stable fixation of the turning tool. Nevertheless, despite high manufacturing costs and precise fine machining, a sufficient form fit between the turning tool and the mounting hole cannot be guaranteed.

The problem underlying the invention is therefore to create a cutting tool system and in particular a tool shaft for this, while avoiding the disadvantages mentioned, in which the cutting tool is easy to use and replace and is held precisely and with great repeatability under a predeterminable clamping force. In particular, a positive fit of the tool shaft in the bore of the tool holder should be achievable.

To solve this problem, the invention proposes that a tool shaft with the features mentioned at the outset should have a spreading slot that is separate from the clamping slot and that is delimited by spring-loaded spreading jaws that are opposite one another and can be pivoted away from one another by an adjusting element to widen it, with at least one clamping and cutting jaw each being connected to one another in such a way that widening of the spreading slot due to one of the spreading jaws being pivoted away results in an increase in the clamping force in the clamping slot due to the connected clamping jaw being pivoted towards the opposite clamping jaw. The pressure of the two clamping jaws on the cutting tool located between them can therefore be increased by actuating the adjusting element and thereby causing the spreading and clamping jaws to pivot relative to one another.

the increase. The associated clamping jaw is coupled to the pivoting movement of the spreading jaw moved by the adjusting element in such a way that the torque exerted on the spreading jaw is transferred to the associated clamping jaw and overall causes an increase in the clamping pressure on the cutting tool located in the clamping gap.

In a further development of the invention, the adjusting element is designed as an insert body that can be inserted into the expansion slot and rotated in the same way as an expansion key. This can, for example, be provided with an oval shape, to which a slot area has a specifically adapted longitudinal and cross-sectional profile. Such an insert body can be conveniently inserted into the expansion slot using a key shaft. For such expansion keys, reference is made to the older patents EP 0 095 Bl and DE 39 06 822.6. By rotating the insert body, the expansion jaws are moved apart from one another due to its oval or other shape with different diameters, and the clamping jaws are therefore also influenced in the sense of increased clamping pressure.

An alternative design option for the adjusting element is in the form of an expansion screw that engages with an internal thread in one of the expansion jaws; after the expansion screw has been moved by rotation through the expansion slot until it stops on the opposite expansion jaw, its further rotation in the same direction leads to the expansion jaw with the internal thread being pushed away, whereby at the same time the associated

clamping jaws are pressed onto the clamped chip tool.

Advantageously, the clamping and spreading slots are arranged next to each other and separated from each other by a joint, from which the connected clamping and spreading jaws are pivotably supported together. The movement principle resulting from this arrangement can be compared to that of a toy seesaw, with the clamping and spreading jaws forming the beam that rests on a stand in the middle and is tiltably mounted. One end of the beam is pivoted upwards, for example, by the adjusting element, so that the other end tends to be adjusted downwards; the latter leads, according to the invention, to an increase in the clamping force on the cutting tool. In a specific implementation of this idea, this joint is designed as a web and/or bridge that runs transversely or diagonally to the clamping and spreading slots, which connect the opposing clamping and spreading jaws to each other. In this way, the joint can be implemented with little construction effort: the clamping and expansion slots can each be formed by material recesses, with the aforementioned web - preferably in a narrow design - being left as a partition or dividing wall between them. The connected clamping and expansion jaws merge into one another in the manner of the rocker arm described above or a double, centrally mounted lever arm.

The desired pivoting of the clamping jaw is also achieved if the clamping and expansion slots run parallel, in particular in a common alignment. This

a particularly good articulation and coupling of the gill and spreading slot is achieved.

The clamping slot is arranged at the front end of the tool shaft so that the cutting tool can be inserted and handled. It is also advantageous to have the expansion slot in the immediate vicinity of the clamping slot. In order to enable the expansion slot or one of its expansion jaws to be easily expanded, a further development of the invention consists in the expansion slot deviating at its end from its longitudinal direction and/or the longitudinal direction of the tool shaft and opening into the outer longitudinal side of the tool shaft. This has the advantage of creating an expansion jaw with a free end that can be easily pivoted; the expansion slot does not have to extend over the entire remaining length of the tool shaft that is still opposite the clamping slot. The other end opposite the clamping slot end of the tool shaft can then be specifically designed, for example, to be accommodated in a tool holder (see below). A special implementation of this idea consists in the expansion slot being L-shaped, with the longer L-leg running approximately in the longitudinal direction of the tool shaft, while the shorter L-leg ends transversely to the longitudinal direction on the outer long side of the tool shaft.

Practical tests have shown that expansion slot widths between about 0.05 and 1.0 mm are appropriate; widths of 0.3 mm are particularly advantageous. To produce and design such widths for the expansion

The well-known wire erosion or wire cutting process is suitable for slotting.

The load on the pivot axis or articulation point of the connecting web between the clamping and cutting jaws is reduced if, according to a further development of the invention, one or both long sides of the expansion slot have an insertion limit stop for the cutting tool to be inserted at a distance from the pivot axis or, if applicable, articulation point of the connected clamping and expansion jaws. Furthermore, it is within the scope of the invention that the clamping surfaces between the clamping jaws and cutting tool not only run parallel to one another, but also diverge from one another or converge towards one another if they are located on opposite or opposite sides of the cutting tool or clamping slot, and/or if one or more clamping surfaces run in a longitudinal section forming an angle profile.

In a tool system with the features mentioned at the beginning, in order to solve the problem mentioned at the beginning, it is proposed according to the invention that the clamping device is designed with two or more clamping elements that are independent of one another, each of which acts on an associated contact surface of the tool shaft. With these separate clamping elements, different pressure forces can be exerted locally at a distance from one another; the tool shaft is pressed into the receiving bore in the tool holder with increased form closure by this force application distributed over the surface. On the other hand, by means of a time-staggered

Actuation or influence of the clamping elements generates a torque; this occurs when the second clamping element is subsequently actuated after the first clamping element has already been actuated. This also results in the tool shank being fitted with increased form-fitting. The resulting gain in stable mounting, repeatability and precision during machining is obvious.

It is particularly advantageous for the clamping elements and their associated contact surfaces to be arranged offset in the transverse direction of the receiving bore in the tool holder. Then, when the clamping elements are actuated at different times, the aforementioned torque runs approximately in line with the circumferential direction of the bore, which results in a particularly stable fixation of the cutting tool transverse to the longitudinal direction of the bore. This aim is also served by an inventive design, according to which both the bore and the tool shaft have a congruent circular arc-shaped profile in cross-section, via which the two contact surfaces for the cutting elements are connected to one another. It is precisely then that the torque that occurs when the cutting elements are actuated at different times can be particularly effective, because the positive circular arc-shaped receptacle in the tool holder bore enables the tool shaft to rotate and/or roll in it.

The contact surfaces for the clamping elements differ from the shape of the other outer surfaces of the tool shank, preferably in that they are not round or

circular arc, but rather flat. It is practical for the attack surfaces to be in different planes. To achieve the torque mentioned, a lever arm can also be formed according to the distance between the two clamping elements. It is practical for the clamping elements and/or their attack surfaces to be arranged evenly or symmetrically with respect to the central axis of the hole in the tool holder, so that the attack of the clamping elements on the tool shaft leads to a comprehensive form closure.

In order to be able to provide the cutting tool on the tool shaft with coolant if necessary, a particularly advantageous development of the invention consists in leaving a through-channel between the tool shaft and the inner wall of the bore; in particular, this through-channel can be arranged between or in the area of the engagement surfaces and/or clamping elements within the bore.

To reduce the width of the through-channel and thus increase the coolant flow speed, an embodiment of the invention is used in which the contact surfaces and the opposite surfaces of the inner wall of the bore run parallel to one another and/or at a distance from one another. This gives the through-channel a substantially square or angular profile that is easy to manufacture with a narrow width.

To realize the clamping elements, it is within the scope of the invention to use clamping screws, each with a

the internal thread in the tool holder leading to the bore. If the clamping screws are turned sufficiently, they press on the respective contact surface on the tool shaft to fix it axially and radially. 5

Another possibility for implementing the clamping elements is in the form of clamping planes, each of which rests against the assigned attack surface of the tool shaft. It is particularly advantageous if the clamping plane is structurally integrated with the inner wall that borders the hole in the tool holder, by being designed as a flat part or section of the inner wall. The savings in manufacturing and design costs are evident. In addition, the clamping plane can easily achieve a larger effective attack surface than the clamping screw, which ultimately leads to a better form fit of the tool shaft in the tool holder.

Further advantages, features and details of the invention emerge from the following description of preferred embodiments of the invention and from the drawings. In them:

Fig.1
to 5 each show a view of the long side

- partially cut - of tool shanks according to the invention,

Fig. 6 a longitudinal side view of a tool system according to the invention with tool holder

and tool shank,

Fig.7

to 10 each show sectional views approximately along the line A-A in Fig. 6 of different working positions or tool system modifications. 5

According to Fig. 1, the tool shaft 1 ends at one end in two clamping jaws 2, 3 that are spring-loaded relative to one another and which together define a clamping gap 4. A cutting insert 6 with a cutting edge 7 protruding from the lower clamping jaw 3 is inserted into the wider front section 5 of the clamping gap 4. Its front end, opposite the cutting edge 7, rests against stop shoulders 8a, 8b on both sides, which serve to limit its insertion. The lower clamping jaw 3 protrudes outwards or forwards relative to the upper clamping jaw 2 and thus forms a tail. The stop shoulders 8a, 8b delimit the front, wider section of the clamping gap 4 from its rear, narrower section 9. This section 9 of the clamping gap 4 extends from here approximately in the longitudinal direction of the tool shaft 1 and ends at a web 10. On the side of the web 10 opposite the clamping gap 4, a spreading gap 11 extends - in the extended longitudinal axis of the clamping gap 4 - which is delimited by an upper spreading jaw 12 and a lower spreading jaw 13. In this arrangement, the web 10 represents a connecting bridge between the upper and lower clamping and spreading jaws 2, 12 and 3, 13. The spreading slot 11 runs in an L-shape with a longer L-leg 14 in the longitudinal direction of the tool shaft and a shorter L-leg 14" running transversely to it, which opens out on the outside of the tool shaft 1.

det. The upper expanding jaw 12 is provided with a hole with an internal thread that is directed transversely to the longer L-leg 14 and with which the external thread of an expanding screw 16 meshes. It can basically be screwed into the expanding slot 10 until it stops at the lower expanding jaw 13, but in the position shown in Fig. 1 it is at a distance from the lower expanding jaw 13. Both expanding jaws can thus spring freely. At the end of the tool shaft 1 opposite the clamping gap 4, attack or support surfaces 17 are formed that are used in the tool system according to Fig. 6 to 9.

The way in which the clamping force is generated on the cutting insert 6 in this tool shank 1 is further illustrated in Fig. 2: The clamping screw 16 is moved into the expansion slot 11 and presses against the inner surface of the lower expansion jaw 13. The upper expansion jaw 12 is moved upwards in the pivoting direction 18 around the web 10 serving as a joint by its threaded engagement 15 with the expansion screw 16; this creates a divergence 19 in the expansion slot 11, which is represented by its widening with increasing proximity to the shorter L-leg 14'. Since the upper clamping jaw 2 and the upper spreading jaw 12 merge into one another in one piece above the joint or connecting web 10 like the two lever arms of a rocker, the upward pivoting movement 18 of the spreading jaw 12 simultaneously gives the upper clamping jaw 2 around the web 10 the tendency to pivot 20 downwards onto the cutting insert 6. This joint rocking movement of the clamping and spreading jaws 2, 12 creates an (increased) clamping force on the cutting insert 6

which is then maintained when the position of the expansion screw 16 remains unchanged. If the cutting insert 6 is to be removed from the clamping slot 4, the expansion screw 16 must be turned back to the position shown in Fig. 1 so that the opposing expansion jaws 12, 13 can freely spring against each other. The cutting insert can then be easily pulled out of the clamping slot 4 if the clamping jaws 2, 3 are only slightly and imperceptibly spread apart from each other.

10

Different shapes for the front section 5 of the clamping slot 4 within the scope of the invention are shown by a comparison of Figs. 1 to 5: The clamping surfaces on both sides, formed between the cutting insert 6 and the upper clamping jaw 2 on the one hand and the cutting insert 6 and the lower clamping jaw 3 on the other hand, run parallel to each other according to Fig. 5, while according to Figs. 1 and 2 they are in

*■ Cutting insert insertion direction 21 diverge from each other.

According to Fig. 3 and 4, the clamping surface between the cutting insert 6 and the lower clamping jaw 3 - viewed in the longitudinal direction - has a profile with the angle 22; in one case, this angle profile protrudes convexly into the lower clamping jaw (Fig. 3), in the other case it forms a concave indentation into which the lower clamping jaw 3 protrudes in a complementary manner (Fig. 4). The clamping surface profiles shown in Fig. 1 to 4 in particular reinforce the fixing of the cutting insert 6, particularly in the axial or insertion direction 21.

Within the scope of the invention, the tool shank according to Fig. 1 to 5 can advantageously be used in a tool system according to Fig.

6 to 9: According to Fig. 6, the tool shaft 1 is inserted into a hole 23 (indicated by dashed lines) within a tool holder 24 with a cylindrical basic shape up to an insertion limit stop 25. 5

As can be seen from the cross-sectional view of Fig. 7, the engagement or support surfaces 17 at the (rear) end of the tool shaft 1 are flat and extend in different planes. Each of these support surfaces 17 serves to engage a clamping screw 26, which can each be screwed along internal threads 27 through the wall of the tool holder 24 into the bore 23. A free through-channel 29 is left open between the support surfaces 17 and a central plane 28 arranged between them, which serves, for example, to conduct and transport cooling medium to the tool shaft 1 and/or to the cutting insert 6.

The operation of the clamping of the tool shaft 1 in the tool holder 24 according to the invention is as follows: According to Fig. 7, the clamping screw 26a shown on the left in the drawing is first actuated and brought into contact with the adjacent support surface 17 under pressure. In the process, the force KL is exerted and the rear part of the tool shaft 1 is pressed into the diametrically opposite area of the wall of the bore 23. According to Fig. 8, the resulting force KR is added after the force KL is triggered by actuating the clamping screw 26b shown on the right in the drawing. Since the two force application points on the respective support surfaces 17 are spaced apart by 1 in the cross-sectional direction,

, a torque M is generated when the clamping screw 26a shown on the right and the clamping screw 26b shown on the left are successively actuated, so that not only the rear part of the tool shaft 1 is pressed into the area of the inner wall of the bore 23 that is diametrically opposite the force KR; rather, the rear part of the tool shaft 1 is also given the tendency to roll along the entire circular section of the inner wall of the bore 23 and thereby cling to or rest against the wall surface with a high degree of form fit. The directions of the forces KL, KR, which enclose the angle 30 with one another, ensure a stable, immovable and comprehensive fixation of the tool shaft 1 both in the transverse direction of the bore 23 and in its circumferential direction. This also has an indirect effect on the positional stability of the cutting insert 6 in the tool shaft 1.

According to Fig. 9, the through-channel 29 is smaller in its inside diameter than the design shown in Figs. 7 and 8 and has a trapezoidal cross-sectional shape. The gap width between the support surfaces 17 and the opposite inner wall surfaces of the bore 23 is significantly smaller than in the design according to Figs. 7 and 8; within the scope of the invention, this gap can also be omitted entirely, so that the clamping screws 26 do not have to enter the interior of the bore 23.

According to Fig.10, instead of one of the clamping screws, a clamping plane 26c is provided, which is designed as a flat section on the inner wall 32 of the tool holder 24 delimiting the bore 23 and with a much larger attack

surface 17 as a clamping screw on the tool shaft 1. The clamping plane 26c interacts with a clamping screw 26b opposite in the transverse direction of the bore, in that both together form the lever arm 1 due to their distance and - when the clamping screw 26b is screwed in - generate the torque M with effects corresponding to the above explanations.

Claims (1)

Protection claims 1. Tool shaft (1) for a cutting tool system, in particular for piercing and/or turning, ending in resiliently opposing clamping jaws (2, 3) which delimit a clamping slot (4) for the use of a cutting tool (6), for example a cutting edge or chisel, characterized by a separate expansion slot (11) which is delimited by resiliently opposing expansion jaws (12, 13) which can be pivoted (18) from one another by an adjusting element (16) in order to expand it, wherein at least one clamping and cutting jaw (2, 12) are connected to one another in such a way that an expansion (18) of the expansion slot (11) causes a narrowing (20) of the clamping slot (4) or an increase in the clamping force on the cutting tool (6). 2. Tool shaft according to claim 1, characterized in that the adjusting element (16) is designed as an insert body that can be inserted into the expansion slot in the manner of an expansion key and rotated therein, preferably with a specific fit for a slot area, or as an expansion screw (16) that is guided along an internal thread (15) through one of the expansion jaws (12, 13) and optionally through the expansion slot (11) until it stops on the opposite expansion jaw (13). 3. Tool shank according to claim 1 or 2, characterized in that the clamping and spreading slot (2, 12) are separated from each other by a joint from which the connected clamping and spreading jaws (2,12) are jointly pivotably supported (18, 20).
5 4. Tool shaft according to claim 3, characterized in that the articulation point is designed as a web and/or bridge (10) running transversely or obliquely to the clamping and spreading slot, which connect opposing jaws (2, 3, 12, 13) to one another. 5. Tool shank according to one of the preceding claims, characterized in that in the region of the pivot axis (10) the connected clamping and spreading jaws (2, 12) merge into one another in the manner of a rocker or a double lever arm. 6. Tool shank according to one of the preceding claims, characterized in that the clamping and spreading slots (4, 11) run parallel and/or in a common alignment or straight line. 7. Tool shank according to one of the preceding claims, characterized in that the expansion slot (H) ^v °n its longitudinal direction and/or that of the tool shank (1) ends at its outer longitudinal side. 8. Tool shank according to one of the preceding claims, characterized in that the expansion slot (11) is L-shaped, with the shorter L-leg (14') ending on the outer longitudinal side of the tool shaft (1). 9. Tool shaft according to one of the preceding claims, characterized in that the expansion slot (11) has a width of approximately 0.05 to 1.0 mm and/or is produced by a wire erosion or wire cutting process and/or has on one or both long sides an extension limit stop (8) for the cutting tool (6) to be inserted at a distance from the pivot axis (10) or, if applicable, the articulation point of the connected clamping and expansion jaws (2, 12). 10. Tool shank according to one of the preceding claims, characterized in that clamping surfaces between clamping jaws (2, 3) and cutting tool (6), insofar as they are located on opposite or opposite sides, run diverging from one another (19) and/or have an angle profile (22) in longitudinal section. 11. Cutting tool system, in particular for grooving and/or turning, with a tool holder (24) with a bore (23) and a tool shaft (1) that can be inserted therein, in particular according to one of the preceding claims, which can be secured by means of a clamping device in the tool holder (24) directed towards the tool shaft (1), characterized in that the clamping device is designed with several mutually independent clamping elements (26a, 26b, 26c) which each act on an associated engagement surface (17) of the tool shaft (1). 12. Tool system according to claim 11, characterized in that the clamping elements (26) and the engagement surfaces (17) are arranged offset in the transverse direction of the bore (1). 13. Tool system according to claim 11 or 12, characterized in that the bore (23) and the tool shaft (1) have a cross-sectionally congruent circular arc-shaped profile (31) which runs from one of the engagement surfaces (17) to the other. 14. Tool system according to one of claims 11 to 13, characterized by flat and/or attack surfaces running in different planes (17). 15. Tool system according to one of claims 11 to 14, characterized in that the clamping elements (26) and/or their engagement surfaces (17) are arranged symmetrically with respect to the bore center axis. 16. Tool system according to one of claims 11 to 15, characterized by a free through-channel (29), for example for coolant, between the tool shaft (1) and the bore inner wall (32), in particular between or in the region of the engagement surfaces (17) and/or clamping elements (26). 17. Tool system according to one of claims 11 to 16, characterized in that the engagement surfaces (17) and the opposite bore inner wall surfaces (32) run parallel and/or at a distance from one another. 18. Tool system according to one of claims 11 to 17, characterized in that one or more clamping elements (26) are designed as separately operable clamping screws (26a, 26b), each of which engages in a tool holder internal thread (27) leading to the bore (23) and, if necessary, rests with pressure (KL, KR) on the respective engagement surface (17) of the tool shaft (1). 19. Tool system according to one of claims 11 to 18, characterized in that one or more clamping elements (26) are designed as clamping planes (26c), which each rest against the associated engagement surface (17) of the tool shaft (1) and preferably form a flat section of the inner wall (32) delimiting the bore (23) in the tool holder (24). 20. Tool system according to claim 19, characterized by a clamping screw (26b) and a clamping plane (26c), which are each directed at and/or act on an associated engagement surface (17) of the tool shaft (1).