Patent Application
20170100784
The invention relates to a rotary tool, in particular a drill, with such a cutting head, as well as a support for such a rotary tool and for accommodating the cutting head.
Drills having replaceable cutting tips mounted on shanks are known. The cutting heads and shanks display continuous and complementing configuration as fluted drills. To this end, each shank has structure for retaining and rotating an associated cutting head. The associated cutting head has complementing structure for being retained and rotated by the shank. While these devices will operate under some circumstances, closer analysis reveals that their useful lives are potentially unduly limited. More specifically, the retaining and drive structure of the shank is subject to deformation and failure during its service life due to concentration of stresses imposed during when drilling on uneven or angled surfaces.
A conventional cutting head and a rotary tool can be derived, for example, from WO 2008/072840 A2 or from the applicant's applications PCT/EP 2015/056288 or DE 10 2015 211744.8, which were unpublished as of the filing date.
The rotary tool is a so-called “modular” rotary tool, which extends in the axial direction along an axis of rotation and has two coupling parts, namely a support and a cutting head. The cutting head is interchangeably mounted on the support. To that end, the support typically has on its front side two fastening bars that face each other and are separated by clamping slots that limit accommodation of pins. Inserted into this pin hole is a coupling pin of the cutting head. This is accomplished by rotating the cutting head around the axis of rotation in relation to the support. This rotation typically forms a clamping connection between the cutting head and the support, clamping together the two coupling parts. At the same time, no other fastening elements, for example screws or the like, are arranged. The fastening by clamping is accomplished between the outer cover surfaces of the coupling pin and the inner cover surfaces of the pin hole.
Also arranged are two corresponding surfaces for transmitting torque from the support to the cutting head. These torque driving surfaces are referred to below in brief as torque surfaces.
Another similar modular rotary tool can be derived from DE 10 2012 200 690 A1.
Modular rotary tools can be divided into two different types. In a first type, like the one derived from, for example, WO 2008/072840 A2, the torque surfaces extend outward radially up to an outermost periphery of the cutting head, also called “drill ridges.” According to a second variant, like the one described, for example, in the two unpublished applications cited above or also in DE 10 2012 200 690 A1, the torque surfaces are formed directly on the coupling pin as its cover surfaces, which interact with corresponding inner cover surfaces of the fastening bars.
Both the torque surfaces and the clamping surfaces of the cutting head and of the support are installed in pairs opposite each other in a coupled state when the cutting head is thus inserted into the support. At the same time, the corresponding clamping surfaces form in each instance a press fit; i.e., in the area of the clamping surfaces, the coupling pin has an allowance vis-à-vis the pin hole.
In some of the applications cited above, formed for an axial pullout safety on each coupling pin are roughly horizontal stop surfaces that interact with corresponding stop surfaces of the support, in order to thus guarantee a positive fit in the axial direction for the cutting head. This positive fit prevents the cutting head from being pulled out from the support in an axial direction, for example when the rotary tool is withdrawn from the drill hole after a drilling procedure.
In WO 2008/072840 A2, a circumferential groove in the form of a recess is formed to form this axial pullout safety on the coupling pin. In a similar manner, in PCT/EP 2015/056288 or DE 10 2015 211744.8, the stop surface is formed by radial grinding in the form of recesses.
In DE 10 2012 200 690 A1, on the other hand, the coupling pin is formed to form a rear grip for an axial, dovetail-type pullout safety.
Based on the above, the problem of the invention is to provide a cutting head, a modular rotary tool and a support, in which the different functions of the torque drive, the fastening by clamps and the axial pullout safety are reliably realized.
According to the invention, the problem is solved by a cutting head with the features of claim 1, by a rotary tool with the features of claim 19 and by a support with the features of claim 23. Advantageous developments are described in the dependent claims.
The preferred designs and advantages of the cutting head, rotary tool and support are in each instance alternatingly transferable.
The rotary tool is generally a so-called “modular” rotary tool that extends in an axial direction along an axis of rotation and which has two coupling parts, namely the support and the cutting head, wherein the cutting head and the support can be interchangeably attached to one another.
In operation, the rotary tool rotates around the axis of rotation in the direction of rotation or peripheral direction. The rotary tool is in particular a drill; thus, the cutting head is in particular a drill head. However, the invention is not limited to use with a drill. The rotary tool can also be, for example, a milling tool or another type of rotating tool, for example a reamer or the like.
The cutting head generally has a front cutting part, to which a coupling pin is attached contrary to the axial direction. Typically formed on the cutting part are two main cutting edges that are connected to each other, in particular in the center section, by means of a chisel edge. Attached to each main cutting edge contrary to an intended direction of rotation is a free surface, which typically merges into a clamping slot associated with the next main cutting edge.
For the interchangeable fastening of the cutting head, the front of the support generally has two opposite-facing fastening bars separated by clamping slots that limit a pin hole. The coupling pin of the cutting head can be inserted to clamp into this pin hole. Preferably, the cutting head is fastened exclusively by the fastening by clamps. The insertion is made by rotating the cutting head around the axis of rotation in relation to the support. This forms the desired clamping connection between the cutting head and the support, so that the two coupling parts are held together by clamping.
The pin hole of the support has inner cover surfaces and the coupling pin of the cutting head has outer cover surfaces that mutually interact with one another. Formed on each inner cover surface and each outer cover surface are corresponding torque surfaces for transmitting torque on one side and corresponding clamping surfaces for transmitting a radial clamping force on the other side. These associated surfaces lie against each other in pairs in the connected state. The torque surfaces and the clamping surfaces form function surfaces for the functions of transmitting torque and of clamping.
Also formed for an axial pullout safety are stop surfaces that correspond to the pin hole and to the coupling pin, which are effective in the axial direction for an axial pullout safety; i.e., in the joined state they are positively covered in the axial direction. In the case of the coupling pin, the stop surfaces are realized by a groove that at the same time divides the coupling pin into a front pin part formed by the groove and a rear pin part. To form the groove, during manufacture in particular with a grinding wheel, an indentation extending in a radial direction is made by grinding. Thus as a result of the groove, a quasi-section is formed between the two pin parts, forming the stop surface.
For the support, to form the stop surfaces an overhang is formed that corresponds to each fastening bar, which overhang in the joined state thus overlaps the rear pin part and engages the groove. Corresponding to the coupling pin, the pin hole also has a front receiving part and a rear receiving part.
The terms “front” and “rear” refer to the axial direction. The axial direction extends in the direction from the support up to the cutting head. The “front” means the part in the direction of the cutting head and the “rear” means the part in the direction of the support.
The function surfaces are generally formed on the outer cover surfaces of the coupling pins or on the inner cover surfaces of the pin hole. The coupling is a type of coupling in which the torque transmission surfaces are arranged on the interior side; i.e., they are hemmed in on the periphery by the fastening bars. The torque surfaces thus specifically do not extend to the outermost periphery of the cutting head; i.e., not up to the rear of the rotary tool, which typically forms the periphery-side boundary surface of the rotary tool.
At least one type of function surfaces, in particular the torque surface, is formed on the rear pin part. Because this rear pin part has a greater diameter than the groove, the rear pin part is more stable and because of its greater radial extension, it is also better suited for the transmission of forces.
An appropriate further development also provides that the function surfaces, i.e. the torque surfaces and the clamping surfaces, are divided between the two parts (pin parts and receiving parts). As a result, different functional levels are defined on the coupling, so that the top pin part or receiving part defines one functional level and the bottom pin part or receiving part defines the other functional level. This divides the functions of torque drive and clamping into different axial subsections. This has the particular advantage that the corresponding sections of the coupling pins and of the pin hole can be optimized for the individual functions. In addition, the axial pullout safety is also realized by the stop surface, which quasi-separates the two parts, regardless of the functions of torque drive and clamping. Altogether, this results in a coupling optimized with regard to different functions, which allows the various functions to be optimized to the different sections.
According to one suitable design, the torque surfaces are formed on the bottom pin part and receiving part, respectively. Because the top part has the groove and/or is formed by the groove, the bottom part generally extends more in the radial direction. Because the greatest possible radial extension is advantageous for transmission of torque, this guarantees an especially effective transmission of torque.
The axial length of the front pin part preferably corresponds to the axial length of the groove; i.e., no other section of the coupling pin connects to the groove in an axial direction. The transmission areas between the individual functional levels typically merge into one another across at least rounded corner areas. Thus, the cutting part, which in the radial direction juts over the coupling pin while forming a head-bearing surface, connects directly onto the groove forward in the axial direction. Thus in particular, the groove merges into a rounding in the head-bearing surface. On the opposite side, the groove preferably also merges into the stop surface via a curve. Each stop surface in turn preferably also passes over a curve or via a chamfer in the lateral surface of the rear pin part. The rear pin part is in turn limited by a bottom pin base, which preferably is formed by a horizontal surface. The lateral surface of the rear pin part preferably also passes over a curve or a chamfer in the pin base.
In one suitable design, the groove runs in a peripheral direction and thus transverse to the axial direction. Thus, it is not inclined with regard to the axial direction and in particular does not have a helical shape.
The groove suitably extends in a peripheral direction around the entire coupling pin, except for any recesses caused by clamping slots, which are formed in the cutting head and cut the coupling pin. In one preferred embodiment, clamping slots are formed, namely in the cutting head, which are aligned with clamping slots of the support. These clamping slots also typically extend into the coupling pin, thus cutting them.
As a result of the fully circular groove, corresponding stop surfaces—except for interruptions caused by the clamping slots—are preferably fully circular also. Thus, the stop surfaces run along sides of the support over the entire fastening bar. The two fastening bars are separated from each other on the support side by the clamping slots.
Alternatively, the groove only runs over a partial area of the fastening bars and thus also only over a partial area of the coupling pin. Preferably, the stop surface joins the torque surfaces in a peripheral direction.
In the inserted state, it is not absolutely necessary that the corresponding stop surfaces directly abut one another or are even clamped together. In principle, a slight gap between the stop surfaces is possible. The pullout safety formed by the stop surfaces is intended, when the rotary tool withdraws, for example, from a bore hole, to prevent the cutting head from being pulled out from the support.
In one preferred embodiment, the stop surface preferably extends according to a first embodiment perpendicularly in the axial direction and thus in the horizontal direction. Thus, the stop surfaces form a common horizontal plane inside of which the stop surfaces are arranged.
Alternatively, the stop surfaces are preferably arranged at an incline to the axial direction. In general, the stop surfaces are spread out by a direction along the periphery of the coupling pins and in a transverse direction. The transverse direction runs outward from the axis of rotation in the direction of the periphery. This transverse direction is inclined under the first angle of inclination with regard to the axial direction. The first angle of inclination is specifically not 90°; i.e., the transverse direction and thus the stop surfaces do not run perpendicular to the axial direction.
The first angle of inclination preferably ranges from 30° to 85° and in particular ranges from 50° to 75°. Accordingly, the stop surface is thus inclined opposite a horizontal plane at an angle from 5° to 60° and in particular at an angle from 40° to 15°. Correspondingly, the support-side stop surface is also inclined at the same angle of inclination, so that the corresponding stop surfaces run parallel to one another. The inclination of these stop surfaces is technically favorable for manufacture. To connect the groove to the coupling pin, typically a grinding wheel is used. Grinding the groove simultaneously forms the stop surfaces. The short axial length of the groove makes it necessary to use comparatively thin grinding wheels. The position of inclination makes it possible to use thicker grinding wheels.
At least one type of function surface on the cover side, and preferably both types of function surfaces on the cover side, run parallel to the axial direction. In particular, the cover-side function surfaces do not form in the axial direction an effective pullout safety; i.e., none of the cover-side function surfaces is inclined in such a way that a positive pullout safety is formed in the axial direction. Thus, viewed from the axial direction (seen from back to front), no cover is formed between the support-side and the cover-side function surfaces.
As an alternative to the design in which the two function surfaces run parallel to the axial direction, a type of cover-side function surfaces is inclined at a second angle of inclination with regard to the axial direction. Each cover-side function surface is in turn spread out by a direction along the periphery and a longitudinal direction perpendicular to it. The longitudinal direction is aligned at the second angle of inclination with regard to the axial direction. The second angle of inclination preferably ranges from 10° to 45° and in particular ranges from 20° to 30°.
Preferably, this function surface is inclined in such a way that it is inclined contrary to the axial direction on the axis of rotation; i.e., viewed in the axial direction, no positive pullout safety is formed with the fastening bars.
This inclined function surface is preferably a torque surface. Inclining the torque surface improves the force transmission between the coupling pins onto the fastening bars. The inclination transmits torque onto the support also in the axial direction. This reduces the load of the fastening bars in the transverse or radial direction. In combination with the arrangement of the torque surfaces in the rear part, this also guarantees an altogether reliable transmission of high torques.
Altogether, the coupling pin is preferably roughly rectangular and has a pair of opposite-facing convex, i.e. outwardly curved, front sides as well as a pair of opposite-facing long sides running specifically in a straight line. In one embodiment in which the pin is cut by clamping slots, each long side is interrupted by a respective clamping slot. At the same time, the clamping slots are in each instance arranged in a roughly diagonal manner and facing the coupling pin. The torque surfaces are also formed specifically on the longitudinal surfaces and the clamping surfaces are formed on the front sides. This rectangular embodiment with long sides that are oriented at an angle with regard to the peripheral direction or direction of rotation of the rotary tool makes possible effective transmission of torque across the long sides.
Advantageously, the two parts, i.e. the rear and the front top pin part or receiving part, extend in an axial direction, preferably over a comparable length. This makes the different functions available in roughly the same lengths for the function zones. “Comparable length” means in this connection that the lengths of the two parts differ by no more than 30%, preferably by no more than 10%. Most preferably, they are identical.
In one preferred embodiment, as an alternative to allocating the function surfaces to the two pin parts, both types of function surfaces are formed on the rear pin part. This makes possible a shorter pin length or if the pin length is the same, a greater length of the rear pin part compared to allocating the two function surfaces to the two pin parts, because the groove can now be made much smaller. Therefore, in this case the groove specifically and exclusively serves to form the stop surfaces.
Preferably, the groove length, i.e. the length of the groove in the axial direction, is only 0.3 to 0.5 times the axial length of the pin part.
The coupling pin generally has a pin length that extends from the already mentioned head-bearing surface up to the pin base. Accordingly, the pin hole also has a length that is defined by the distance between the front contact surfaces of the fastening bars and a base of the pin hole. According to a first preferred variant, the two lengths are coordinated in such a way that in the joined state the head-bearing surface of the cutting head rests on the front contact surfaces and a slight distance (gap) is formed between the base of the pin hole and the pin base. Thus, in this variant the pin length is shorter than the length of the accommodation.
In a second preferred embodiment, in the combined state the coupling pin and its pin base are supported on the base of the mounting. Therefore, in this case the pin length is greater than the length of the mounting. In the second design variant, therefore, a slight gap is formed between the front contact surfaces and the head contact.
The distance, i.e. the difference between the two lengths, is preferably no more than in the range of less than one hundredth of a millimeter. However, in principle, a greater distance can be set.
In one suitable design, in each instance cut-outs are made on the base of the pin hole in the transition area from the inner cover surfaces to the base. In this connection, a “cut-out” means a kind of depression, so that a hypothetical cutting plane of the base (extending in a horizontal direction) is cut in the longitudinal direction (and thus at a hypothetical lengthening of the inner cover surface) of the bottom receiving part of a clearance.
The clearance preferably extends from the start of the fastening bar contrary to the direction of rotation. In so doing, the clearance forms a radius. The clearance reduces in an advantageous manner stresses that occur at the inserted cutting head. The clearance has a positive effect on the elasticity of the fastening bars.
According to a first design variant, the clearance only extends over a partial section of the fastening bar and, indeed, in particular only over the area of the clamping surfaces. Alternatively, the clearance in a suitable alternative extends over the entire fastening bar.
As a result of the coupling pins, generally a good guide is formed, in particular for forces having a lateral effect on the cutting head, for example in the case of a slight tilting away from the axial direction. At the same time, the coupling pins prevent any tilting of the longitudinal axis of the cutting head in relation to the longitudinal axis of the support.
According to a preferred further development, the coupling pins also have in the rear pin part, i.e. in the area of the torque surfaces, excess with regard to the pin hole. In the area of the clamping surfaces, excess is realized for the desired clamping effect of the coupling pins. Rotating the coupling pin therefore somewhat expands the pin hole. The additional excess is now also achieved in the rear pin part, so that in the inserted state, there is no distance between the coupling pins and the pin hole, or only a small (<5 μm) one. This guarantees a good guide.
Excess” generally means that a nominal width of a coupling pin is greater than a corresponding nominal width of the pin hole. In the area of the clamping surfaces, the excess ranges, for example—measured as the distance from the clamping surface to the axis of rotation—from 2/100 to 4/100 mm. The excess in the rear pin part is advantageously smaller than in the front pin part, and in particular is smaller by at least a factor of 2 and preferably by a factor of 2 to 4.
Exemplary embodiments of the invention are described in detail by the use of figures. In the figures, identically acting parts are given the same reference numbers.
The rotary tool 2 shown in the figures is formed as a modular drilling tool. It extends in an axial direction 4 along an axis of rotation 6. Around the axis of rotation 6 rotates the rotary tool 2 during normal operation in the direction of rotation, which at the same time defines a peripheral direction 8.
The rotary tool 2 consists of a support 10 and a cutting head 12 that can be interchangeably fastened to it. The cutting head 12 has a front cutting part 13 and a coupling pin 14 connected to it. The cutting part 13 is limited on the front side by an anterior front surface and in this instance does not have precisely calculated main cutting edges, which typically are connected to one another in the center of a drill front via a transverse cut and extend radially outward. Main cutting edges are connected to the main free areas on the front contrary to the direction of rotation and peripheral direction 8. On its circumference, the cutting head 12 has a ridge 15 that is interrupted by opposite-facing clamping slots 16 that start in the cutting head 12 and merge into the support 10. In the exemplary embodiment, the clamping slots 16 are roughly spiral in shape. The support 10 is a grooved shaft section in which secondary cutting edges, which extend, for example, along the clamping slots 16 and start at the cutting head 12, continue. A non-grooved tightening section is typically attached to a grooved shaft section of the support 10, with which the rotary tool 2 is clamped into a machine tool.
Elements on the support 10 that correspond to one another are identified below with the letter “a” and on the cutting head 12 with the letter “b.”
The support 10 has on its front side two roughly diagonal, opposite-facing fastening bars 18 that are interrupted by the clamping slots 16. The fastening bars 18 extend in a peripheral direction 8 in each instance across an angular range of approximately 70° to 90°. The front of each fastening bar 18 is limited by flat front contact surfaces 22a, which are arranged in the exemplary embodiment within a common horizontal plane to which the axis of rotation 6 is thus vertically aligned.
The circumference of the pin hole 20 is limited by inner cover surfaces 24a of the fastening bars 18. It is also limited on its bottom side by a base 25a running horizontally, i.e. perpendicular to the axis of rotation 6. Inserted into this base 25a concentric to the axis of rotation 6 is a centering hole 26a. Also running in the exemplary embodiment 2 are coolant channels 28 in the support 10, which escape through the bottom surface and align there with corresponding coolant channels 28 of the cutting head 12.
On the inner cover surfaces 24a, the support 10 has in each instance torque sections 30a and clamping sections 32a, which are aligned in the axial direction 4 offset to one another and follow—viewed in a projection in axial direction 4—one another in peripheral direction 8 under an intermediate arrangement of a transition section. Directly attached to the base 25a are groove-like indentations 36 in the inner cover surfaces 24a, which forms a projection. This projection forms on its bottom side aligned to the indentation preferably horizontally extending stop surfaces 38a.
The groove-like indentation 36 formed as a type of recess divides the pin hole 20 into two parts, namely a front receiving part 40a and a rear receiving part 42a.
Corresponding to the pin hole 20, the cutting head 12 has the coupling pin 14, which extends in axial direction 4. The coupling pin 14 is radially offset backwards in a radial direction from the peripheral surfaces of the ridge 15. Corresponding to the pin hole 20, the coupling pin 40 has outer cover sections 24b, on which also are formed torque sections 30b and clamping sections 32b. These sections are aligned in the axial direction 4 offset to one another and follow—viewed in a projection in axial direction 4—one another in peripheral direction 8 under an intermediate arrangement of a transition section.
The radially offset backwards coupling pin 14 forms in the transitions from the cutting part 13 to the coupling pin 14 a radial projection to the ridge 14, as a result of which two head-bearing surfaces 22b are formed that are in turn arranged in a common horizontal plane and which are separated by the clamping slots 16.
Inserted into the coupling pin 14 is a particular—except for the recesses caused by the clamping slots 16—circumferential groove 37 that divides the coupling pin into two parts, namely a front pin part 40b and a rear pin part 42b.
Also formed concentrically to the axis of rotation 6 on the coupling pin 14 is an insertion pin 26b, which is formed solely for use in the support 10 as a first centering aid of the cutting head 12. The cutting head 12 is actually centered by the clamping sections 32a and b.
As is clear in particular from the top views of the cutting head 12 according to
In the exemplary embodiments, the groove 37 and the groove-like indentation 36 in each instance extend completely circumferentially and in each instance lead into the clamping slots 16. The two parts (pin parts and receiving parts) 40a and b and 42a and b form two function zones or functional levels that are offset to one another in axial direction 4. In the front part 40a and b are formed the clamping surfaces 32a and b, and in the rear part 42a and b are formed the torque surfaces 30a and b.
As is clear in particular from the top views of
The groove 37 passes—viewed in axial direction 4—on the end side preferably across rounded transition areas in the head-bearing surfaces 22b extending radially outwards and in the backward area passes into the stop surfaces 38b. The groove 37 has a groove length 11 that is defined by the distance between the head-bearing surfaces 22b and the stop surface 38b. At the same time, the groove length 11 also defines in this respect an axial length of the front pin part 40b. In the same manner, the front receiving part 40a also has a length corresponding to the groove length 11.
The rear pin part 42b extends in an axial direction across a part length I2 that is defined by the distance between the stop surfaces 38b and the base 25b. In the same manner, the rear receiving part 42a has a length corresponding to the part length I2.
The part length I2 and the groove length 11 are roughly the same, and preferably identical. They preferably differ by no more than 30%. They generally range, for example in the case of a rotation tool 2 with a nominal diameter of 16 mm, between typically 2 mm and 5 mm, and in particular measure approximately 3 mm (+/−0.5 mm). For other nominal diameters, the respective part length is correspondingly adjusted so that the ratio of nominal diameter to part or groove length remains the same.
In the first exemplary embodiment according to
Alternatively, the stop surfaces 38a and b run in a horizontal direction perpendicular to the axial direction.
The stop surfaces 38a and b are generally clamped by a direction along the circumference of the coupling pin 14 or of the pin hole 20 and a transverse direction that is aligned perpendicular to the direction along the circumference. At the same time, this transverse direction is inclined with regard to axial direction 4 under the first angle of inclination α1. If a circumferential section runs along a circular arc line around the axis of rotation 6, the transverse direction will correspond to the radial direction.
The stop surfaces 38a and b extend in a longitudinal direction that typically measures a few millimeters, for example 0.5 mm to 2 mm.
The transition areas between various lateral surfaces 30a and b, 32a and b in an axial direction to the adjacent surfaces 22a and b, 38a and b, and 25a and b, are in each instance rounded or tapered.
In the design variant according to
A second design variant of the rotary tool 2 is shown in
Due to the arrangement of the torque surfaces 30a and b in the rear part 42a and b, the torque surfaces 30a and b are aligned together at an oblique incline with regard to axial direction 4 under a second angle of inclination α2 (see
For assembling the cutting head 12, it first is inserted forward into the pin hole 20 in axial direction 4 along with its coupling pin 14. In this connection, it is, in contrast to the position shown in
In the assembled end position, according to the first embodiment shown in
Altogether, an extremely reliable coupling between the cutting part 12 and the support 10 is realized by the design described herein containing the function surfaces separated into different axial function zones, namely torque surfaces 30a and b and clamping surfaces 32a and b, as well as the separately formed axial pullout safety in the form of the stop surfaces 38a and b.
A further, third design variant is shown in
In this design variant, the groove 37 has a significantly shorter groove length 11 that preferably ranges from 0.3 to 0.5 times the part length 12. Thus, the part length 12 is generally significantly greater (by at least a factor of 2) than the groove length 11. This makes possible, compared to the preceding exemplary embodiments, on the one hand a short pin length 13, or the part length, 12 and thus the length of the function surfaces 30a and b and 32a and b, can be increased. [000105] As in the preceding exemplary embodiments, the groove 37 connects directly to the head-bearing surface 22b. The stop surfaces 38b in turn run perpendicular to the axial direction 4 or inclined in relation to it. The pin hole 20 is also formed in accordance with the design of the coupling pin 14.
The patents and publications referred to herein are hereby incorporated by reference.
Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.
