Surgical milling cutter with improved chip removal
Patent Information
- Authority / Receiving Office
- TR · TR
- Patent Type
- Patents
- Current Assignee / Owner
- AESCULAP AG
- Filing Date
- 2020-11-12
- Publication Date
- 2026-06-22
AI Technical Summary
Existing surgical milling cutters face issues with inefficient chip removal, high heat generation, difficulty in cleaning, and limited visibility during surgical procedures due to their design, leading to impaired cutting performance and potential tissue damage.
A surgical milling cutter with a symmetrical design featuring two diametrically opposed teeth and cutting edges that facilitate axial and lateral tissue ablation, providing large interdental spaces for efficient chip removal and reduced heat generation, ensuring easy cleaning and improved visibility.
The design ensures effective cutting performance, particularly in the axial direction, with minimal heat generation, easy cleaning, and enhanced visibility, making it suitable for high-speed medical applications without tissue damage.
Abstract
Description
[0001] The present invention relates to a surgical milling cutter with a shank for rotary coupling with a drive unit around a rotation axis extending in the longitudinal direction of the shank and a milling head arranged distally on the shank, which has at least two teeth with cutting edges for rotary ablation of tissue, each designed for ablation of tissue in both the distal and lateral directions and extending from distal to the rotation axis of the milling cutter in a proximal radial outward direction, wherein a chip space is formed as a clearance space between teeth adjacent in the circumferential direction.
[0002] Surgical burs are well-known from the prior art and are used for the ablation of hard tissue such as bone or cartilage by being driven rotationally around a longitudinal axis. So-called rose burs or rose cutters are milling tools with an almost spherical cutter head equipped with many cutting teeth, ranging from six to fourteen depending on the diameter. The teeth and their cutting edges converge at the distal end of the cutter head along the axis of rotation. Due to the large number of teeth, their height decreases towards the distal end and is zero directly at the axis of rotation. Therefore, there is no interdental space between the individual teeth immediately at or near the distal end of the cutter. While appropriate geometric optimization can potentially...In the area of the distal end of the milling cutter head, a slightly greater tooth height and thus slightly larger chip spaces are created. However, since the cutting edges meet in the center, i.e., at the axis of rotation of the milling cutter head, even with such optimization the disadvantages of difficult chip removal, a resulting relatively high temperature rise, and a severely restricted or nonexistent view of the working area remain.
[0003] The teeth / cutting edges of such rose burrs are typically manufactured by grinding. This process uses so-called pointed grinding wheels. These wheels usually have a grinding angle of 60° to 90° and, through material removal in the burr head, form the interdental space. The penetration depth of the pointed grinding wheel into the burr head is adjusted so that the tooth face of a previous interdental space aligns with the tooth back of a subsequent interdental space to form a tooth with a corresponding cutting edge. The teeth are usually formed with a helix, i.e., a spiral shape, to prevent the pointed grinding wheel from running into the burr shank when grinding the proximal area of the burr head. This allows the teeth or cutting edges in the proximal area of the burr head to be formed slightly closer to the axis of rotation.The pointed cutting discs are set so that the rake angle of the cutting edges is negative and usually between -10° and -40°. The clearance angle at the cutting edges is correspondingly very large, between 40° and 70°.
[0004] One disadvantage of such rose cutters in terms of their manufacture is the long running time of the grinding machine during production, due to their high number of teeth / cutting edges, which leads to high manufacturing costs.
[0005] One disadvantage of this type of milling tool in terms of practical use is that, due to the relatively sharp teeth and their large number resulting from the manufacturing process, a so-called "chattering" can often occur when working with bone, which manifests as uncontrolled jumping away from the area being worked, making precise work impossible or extremely difficult.
[0006] Another disadvantage is caused by the relatively small interdental space between the teeth in the distal end region, which acts as the chip space. During machining, bone material removed from the teeth accumulates in the chip space and must be transported away to make room for newly removed material. If the material transport through the interdental spaces is insufficient, the chip space becomes clogged, and the cutting edges are obstructed by accumulated material. As a result, further material removal is no longer possible. This is one of the reasons why it is problematic to achieve satisfactory cutting performance and cutting efficiency in the axial direction with such milling heads. This disadvantage is particularly serious because surgical procedures very often require working at depth (i.e., axially) to remove bone in the axial direction. A clogged cutting edge in the center of the milling head, or...The interdental space is difficult or impossible for the surgeon to see because the milling head itself obstructs their view. Cleaning a blocked interdental space during surgery is very difficult. If the interdental space is blocked and the surgeon then proceeds to work on bone, increased pressure and friction can occur, leading to a rise in temperature. This is particularly critical because even temperatures above 45°C can cause coagulation of the patient's proteins, with well-known adverse consequences.
[0007] To mitigate the latter problem, these types of milling cutters are rinsed or cooled with liquid. The liquid facilitates chip removal and reduces heat buildup at the work site. However, insufficient cutting performance and inadequate liquid supply can lead to localized overheating, potentially causing coagulation of the bone. Furthermore, excessive heating of the interdental material can occur, causing it to coagulate and become very difficult to remove.
[0008] Another disadvantage can be that, due to the geometry of the milling cutter, a surgeon has no direct view of the surgical site, i.e., the area of operation at the tool tip. This applies to both milling cutters in operation and those that are stationary. Therefore, to examine the surgical site, at least partial, if not complete, removal of the milling cutter from the surgical area is necessary.
[0009] Finally, the many deep interdental spaces of such rose burs or rose drills are difficult to clean in everyday clinical practice during their preparation.
[0010] In addition to the milling cutters described above, milling tools with two cutting edges, such as so-called olive cutters or neuro cutters, as well as so-called twin-cutter milling tools, are known in medical technology. However, these have a significantly smaller chip space.
[0011] A surgical bur with only one cutting edge, a so-called single-flute bur, has a relatively large chip space. US 2017 015 0974 A1 discloses an example of such an instrument. However, due to the single cutting edge and the bur head's asymmetrical / eccentric design relative to the axis of rotation, its mass is distributed eccentrically, resulting in an imbalance during operation. This leads to rough, uneven running of the bur, which places considerable stress on the handpiece and especially its bearings, and causes increased operating noise.
[0012] Medical burs with helical teeth are disclosed in WO 2011 / 023 381 A1 and KR 101 200 448 B1. US 2013 / 261 628 A1 discloses a drill bit for a power drill. The cutting edges of this drill bit are also helical.
[0013] EP 0 925 760 A2 and US 5 788 699 A both disclose medical drills. However, the drill disclosed in EP 0 925 760 A2 is not suitable for axial tissue removal. The drill disclosed in US 5 788 699 A lacks point symmetry with respect to an axis of rotation. Instead, the cutting edges of the drill are arranged on the same side of the axis of rotation. This can lead to imbalance during drilling or rotation around the axis of rotation.
[0014] Against this background, the present invention aims to reduce the aforementioned disadvantages of the prior art, in particular to provide a milling cutter with improved cutting performance in the axial direction, low heat generation, and improved chip removal from the distal end region, especially for high-speed applications in medicine for processing bone. A further objective is to provide a milling cutter that is particularly easy to clean and is especially suitable for obtaining tissue material such as bone or cartilage for further artificial material production. Finally, the invention is intended to provide an improved method for obtaining bone and / or cartilage material.
[0015] This problem is solved according to the present invention by a surgical milling cutter according to claim 1, i.e. a surgical milling cutter with a shank for rotary coupling with a drive unit about a rotational axis extending in the longitudinal direction of the shank, in particular with a surgical handpiece, and a milling head arranged distally on the shank, wherein the milling head has at least two teeth, each with cutting edges for rotary ablation of tissue, wherein the cutting edges are each designed for ablation of tissue in both axial and / or distal directions as well as in radial and / or lateral directions, wherein a chip space is formed as a clearance space, also referred to as an inter-tooth space, between teeth adjacent in the circumferential direction.Each chip space extends on the side of the respective cutting edge facing the axis of rotation from the cutting edge to a region on the opposite side of the axis of rotation, at least in a distal section of the cutter. The teeth are arranged and formed transversely to the axis of rotation, diametrically opposed to each other, and aligned in a single plane. The teeth can be designed such that a top surface of one tooth and a back surface of the other tooth together form a flat surface in which the axis of rotation lies.
[0016] It can also be said that, according to the invention, each chip space is formed on the cutting edge side of the milling cutter's axis of rotation and extends, at least in a distal region, to the side of the axis of rotation facing away from the respective cutting edge. The surgical milling cutter according to the invention is preferably rotationally symmetrical about its axis of rotation and / or has a mass distribution symmetrical about the axis of rotation, so that it can be operated without imbalance.
[0017] The back surface of one tooth and the front surface of the other tooth can together form another flat surface opposite the aforementioned surface. The two surfaces can be parallel to each other. Preferably, they are parallel to each other in a direction transverse to the axis of rotation, but inclined to each other by a tooth thickness angle in the direction of the axis of rotation.
[0018] A particular advantage of the invention is that the design of the teeth or cutting edges is such that the interdental space / chip space in the distal end region of the milling head, near or at the axis of rotation (at the tip), is as large as possible. This ensures efficient removal of the material removed by the milling cutter (especially bone dust or chips). In most cases, the need for liquid-based material removal aids can be advantageously reduced. Coagulation of the treated bone, as well as of the removed material in the interdental space, due to excessive heat, can be reliably avoided. Therefore, and due to the good accessibility of the teeth, interdental spaces, and cutting edges, the milling cutter is particularly easy and thorough to clean.A further particular advantage of the invention lies in the fact that, due to the inventive design of the milling cutter and its chip spaces, the surgeon is afforded a particularly good view of the surgical site without having to completely or partially remove the milling cutter from the operating area. Finally, heat generation is extremely low, so that disproportionate heating of bone material, especially to temperatures of 45°C and above, can be reliably avoided during processing with the milling cutter according to the invention. An advantageous consequence of this can be that the removed bone material is not damaged and can therefore be used for further purposes, for example, bone grafting.
[0019] Advantageous embodiments of the invention are claimed in the dependent claims and are explained in more detail below.
[0020] One embodiment is characterized in that the cutting edges are each arc-shaped, extending from distal-radial-inward to proximal-radial-outward. They can also be nearly semicircular and / or arc back radially inward from the widest point of the cutter head in the radial direction to the cutter shank. Preferably, the cutting edges of the cutter head extend from distally, starting at the cutter's axis of rotation, in a proximal radial-outward direction. The cutting edges of each cutter head can be formed, in particular, at the edges and shaped such that, when the cutter rotates about its axis of rotation (longitudinal axis), they trace a path that is preferably substantially spherical. Such a cutter can also be called a ball end mill and is particularly well suited for applications where material needs to be removed in the lateral / radial and / or axial / distal direction.Within the scope of the invention, the milling head can also be designed such that the envelope geometry described by the cutting edges during a rotation of the milling cutter has other shapes, for example those of a flame cutter, conical cutter, cylindrical cutter or oval cutter.
[0021] In another embodiment, the teeth or cutting edges can be designed without helical or spiral edges. This improves the accessibility of the interdental spaces and thus the cleaning effectiveness. Furthermore, such tooth / cutting edge shapes are relatively easy, quick, and inexpensive to manufacture.
[0022] In a further embodiment, the milling cutter can have exactly two teeth or cutting edges arranged on diametrically opposite sides of the cutter's axis of rotation. The cutting edges are formed on the opposite sides of the two teeth, so that both cutting edges remove material when the milling cutter rotates around its axis. The cutting-edge surface of the tooth is also referred to as the tooth face, and the side of the tooth facing away from the cutting edge is called the tooth back. The respective cutting-edge clearance (i.e., on the side of the tooth face) constitutes the chip space, as defined in the invention, for material removed by the corresponding cutting edge. Due to the described arrangement and design of the cutting edges / teeth, the two interdental spaces are particularly large, ensuring excellent removal of the removed material and enabling rapid healing of non-coagulated bone.
[0023] Such a two-toothed or two-edged design can be achieved particularly effectively and easily by removing material from the milling cutter on both sides of the axis of rotation (laterally), at least at the distal end of the cutter, down to the axis of rotation. This removal then forms a largely flat surface that creates the tooth face of the respective tooth.
[0024] Alternatively or additionally, a step or shoulder can extend distally from the axis of rotation in a proximal direction, so that the surface forming the tooth's crown transitions into the dorsum of the opposing tooth with a step or shoulder. This step or shoulder forms a boundary between the crown of one tooth and the posterior surface of the adjacent tooth (in the cutting direction), i.e., the dorsum of the other tooth. In a particularly advantageous embodiment for manufacturing purposes, the step or shoulder extends from the tip of the cutter head, i.e., from the intersection of the distal end of the cutter head with the axis of rotation, at an oblique angle to the axis of rotation, so that the shank of the cutter is just barely not touched in the posterior (proximal) region of the cutter head.This angle preferably lies in the plane of the respective crown surface, is also referred to as the setting angle, and preferably lies in a range of 2° to 10°. In other words, the tooth crown, together with the surrounding clearance angle, forms the cutting edge. Alternatively or additionally, the tooth back can be designed with a constant width.
[0025] The tooth face is designed and / or arranged in such a way that the rake angle at the cutting edge is 0°.
[0026] A particularly advantageous embodiment of the invention with regard to material removal is characterized in that at least one of the cutting edges has at least one interruption or groove, in particular as a chipbreaker groove. This can be provided in the tooth, in particular in a centripetal direction. The interruption of the cutting edges reduces their width, thus facilitating penetration of the cutting edges into the bone, which in turn leads to improved cutting performance. The chipbreaker grooves of adjacent teeth / cutting edges can be offset from one another and / or arranged, in particular such that the grooves of one tooth are located at the positions corresponding to the cutting edges of the other tooth and vice versa, so that the cutting edges of the teeth alternately participate in the material removal. In this way, the size and shape of the removed chips can be determined, thus optimizing the removal of the removed material.Furthermore, this ensures that, with regard to the area swept by the respective cutting section during its rotation around the axis of rotation, only one cutting edge is engaged, even though the milling cutter nominally has more cutting edges.
[0027] The back of the tooth, the side facing away from the cutting edge, can be inclined and / or positioned relative to the axis of rotation, so that the tooth widens conically from distal to proximal towards the shaft. The back of the tooth can also be designed as a flat surface, which improves accessibility, ease of cleaning, and ease of manufacturing.
[0028] The tooth thickness can increase from distal to proximal at an angle of 1° to 10° relative to the axis of rotation. This angle is called the tooth thickness angle. This results in particularly high stability and also good cleaning properties. The distal thickness of the tooth or cutting edge can be between 1 / 20 and 1 / 10 of the diameter of the cutter head in the radial direction. In this way, a particularly large chip space can be provided while simultaneously ensuring high tooth / cutting edge stability. Furthermore, the cutting performance and chatter tendency can be influenced by appropriately designing the tooth thickness. Finally, the strength of the cutter head can be defined by the tooth thickness at the required height.
[0029] Another embodiment of the invention is characterized in that the cutting edge has a constant clearance angle in a range between 2° and 30°. Alternatively, the cutting edge can have a clearance angle that varies from distal to proximal, particularly in a range between 2° and 30°. Furthermore, the cutting edge can have a rake angle of 0°. The circumferential clearance angle essentially forms the shape of the cutter head that defines the material removal. By appropriately shaping the clearance angle, the cutting performance and chatter tendency can be influenced. The cutting performance and chatter tendency can be further positively influenced by the variation of the clearance angle along its path as described above.
[0030] A particularly user-friendly embodiment is characterized by the fact that the milling head has a tip at its distal end with an angle of 110° to 150°, which ensures particularly good and easy centering and thus handling during use, especially when working axially with the milling tool. This angle is referred to as the tip angle. Proximal to the tip, the cutting edge / tooth can be arc-shaped, particularly circular.
[0031] According to the invention, the milling cutter can be designed either as a right-hand rotating milling cutter (right-hand cutter) or as a left-hand rotating milling cutter (left-hand cutter).
[0032] In summary, the invention provides a surgical milling cutter, which in particular may have only two cutting edges. The interdental space is preferably designed such that the removed tissue can be transported away as freely as possible. The tooth shape can be designed in such a way that all material not required for the strength of the tooth is removed. Furthermore, the surfaces of the milling cutter, especially the cutter head, can be designed to be particularly smooth and flat, which facilitates chip removal. Due to the low heat generation and the particularly good chip removal, a particularly gentle material removal can be achieved with the milling cutter according to the invention, whereby changes and / or damage to the removed material are largely, if not completely, avoided.Material removed by means of a milling cutter according to the invention is therefore particularly suitable for the artificial regeneration of such material within the framework of the method according to the invention.
[0033] The invention offers in particular the following advantages: Very good cutting performance, especially in the axial direction; very good chip removal due to only two cutting edges; reduced temperature development at the cutting edge and in the tissue; very easy-to-clean cutter head; symmetrical design of the cutting edges; easy to clean due to highly accessible surfaces; no negative rake angle; low chatter tendency; no tendency for the interdental spaces to become clogged; very smooth running without vibration, as the mass is arranged symmetrically to the axis of rotation; cost-effective to manufacture due to the small number of teeth / cutting edges; simple and cost-effective milling cutter for high-speed applications in medicine, for machining bone
[0034] Further features and advantages of the present invention will become apparent from the following exemplary and non-limiting description of the figures. These are merely schematic and serve only to illustrate the invention. They show: Fig. 1 Two perspective views of a state-of-the-art rose cutter, Fig. 2 a perspective view of a cutting machine according to the state of the art, Fig. 3 a perspective partial view of a distal section of a milling cutter according to a first embodiment of the invention, Fig. 4 a side view of the milling cutter Figure 3 , Fig. 5 a sectional view of the milling cutter Figure 3 in a direction perpendicular to the axis of rotation, Fig. 6 a view of the milling cutter of the Figure 3 , Fig. 7 a front view of the milling cutter Figure 3 , Fig. 8 a partial cut of the milling cutter Figure 3 through the axis of rotation, Fig. 9a perspective view of the milling cutter Figure 3 from another direction, Fig. 10 another perspective view of the milling cutter Figure 3 from another direction, Fig. 11 a perspective view of another embodiment of a milling cutter according to the invention, Fig. 12 a side view of the milling cutter Figure 11 , Fig. 13 a view of the milling cutter of the Figure 11 , Fig. 14 a front view of the milling cutter Figure 11 , Fig. 15 a perspective view of another embodiment of a milling cutter according to the invention, Fig. 16 a perspective view of the milling cutter Figure 15 from another direction, Fig. 17 a perspective view of another embodiment of a milling cutter according to the invention, Fig. 18 one of the Figure 7 corresponding representation with a marking of the chip spaces, Fig. 19 one of the Figure 14corresponding representation with a marking of the chip spaces, Fig. 20 a view of a further embodiment of a milling cutter according to the invention, Fig. 21 a sectional view of the milling cutter Figure 20 in a direction perpendicular to the axis of rotation, Fig. 22 a sectional view of the milling cutter Figures 20 and 21 in a side view, Fig. 23 an enlarged detail view from Fig. 22 , Fig. 24 a side view of another embodiment of a milling cutter according to the invention, Fig. 25 a view of the milling cutter of the Figure 24 , Fig. 26 a front view of the milling cutter Figures 24 and 25 in a direction perpendicular to the axis of rotation and Fig. 27 an enlarged detail view from Fig. 24 .
[0035] Figure 1Figure 1 shows a rose cutter 1 according to the state of the art in two perspective views from different angles. This cutter has a proximal shank 2 and a distal cutter head 3 with an approximately spherical outer contour. The rose cutter 1 has a longitudinal axis 4, which is also its axis of rotation 4 during operation. In the illustrated example, it is provided with a total of eight teeth 5, on the side of each tooth facing away from the axis of rotation 4, a cutting edge 7 is formed, extending from a distal tip 6 of the cutter head 3 towards the proximal end of the cutter shank 2. A space 8 is formed between each adjacent tooth 5. The teeth 5 each have a helix and extend helically from distal to proximal. It can therefore be said that the teeth 5 and their cutting edges 7 converge at the distal end 9 of the cutter head on the axis of rotation 4 of the rose cutter 1.In the two views of the . Figure 1 It is clearly shown that the height of the teeth 5 decreases towards the distal end 9 and is zero directly at the axis of rotation 4 or the tip 6. In other words, the depth of the interdental spaces at the distal end 9 or at the tip 6 is zero and increases proximally towards the cutter shank 2. The chip space available for material removed during axial feed in the direction of the longitudinal axis 4 of the cutter 1 is therefore very small near the tip 6 and non-existent at the tip 6, so that the interdental spaces 8 can easily become clogged, leading to the disadvantages described above.
[0036] The Figure 2Figure 1 shows another known milling cutter 10 in the form of a so-called single-flute cutter 10 in a perspective view. This cutter has a shank 11 proximally and a cutter head 12 distally. The single-flute cutter 10 has a longitudinal axis 13, which is also its axis of rotation 13 during operation. The cutter head 12 is formed by a flattened section on one side extending to the axis of rotation 13 and has a cutting edge 14b with a substantially flat face 15. On the opposite side of the cutting edge 14b, a recessed edge 14a is formed. This forms a clearance for the cutting edge 14b. The milling cutter is designed exclusively for clockwise rotation, meaning it only cuts in clockwise directions.Due to its shape, the entire mass of the milling head 11 is located on one side of the axis of rotation 13, so that the mass distribution of the single cutter 10 is asymmetrical, which is associated with the disadvantages described at the beginning.
[0037] The Figures 3 , 9 and 10 show a first embodiment of a surgical milling cutter 16 according to the invention, to which the Figures 4 to 8 Furthermore, views and sectional views from different directions are shown. The milling cutter 16 has a milling shank 17 proximally and a milling head 18 distally. The milling cutter 16 has a longitudinal axis 19, which is also its axis of rotation 19 during operation. The milling shank 17 extends coaxially to the axis of rotation 19, which centrally penetrates the milling head 18 at its distal end 20 (see especially in Figure 7 ).
[0038] The milling cutter head 18 has exactly two teeth 21 and 22, namely a first tooth 21 and a second tooth 22. Tooth 21 has a cutting edge 23 for rotary material removal. Tooth 22 has a cutting edge 24 for rotary material removal. The two teeth 21 and 22, and thus also the cutting edges 23 and 24, are arranged diametrically opposite each other on the rotation axis 19 of the milling cutter 16, offset from each other transversely to the rotation axis 19. The cutting edges 23 and 24 are each located on the side of the corresponding tooth 21 and 22 facing away from the rotation axis 19 and are each arc-shaped. They begin at the distal end 20 on the axis of rotation 19 and initially extend from distal-radial-inside to proximal-radial-outside, then continue in an arc shape from the widest point 25 of the cutter head 18 to the cutter shaft 17.The cutting edges 23 and 24 are each unhelical and free of helical twist. Due to this shape, the milling cutter 16 has a path of essentially spherical shape when rotating about its axis of rotation 19.
[0039] Teeth 21 and 22 are identically formed, so the description of tooth 21 applies equally to tooth 22. This is particularly evident in... Figure 7As can be seen, tooth 21 has a flat top surface 26a, which forms the front surface of tooth 21 in the direction of rotation, and a flat back surface 27a, which forms the rear surface of tooth 21 in the direction of rotation. Tooth 22 has a flat top surface 26b, which forms the front surface of tooth 22 in the direction of rotation, and a flat back surface 27b, which forms the rear surface of tooth 22 in the direction of rotation. The direction of rotation is the cutting direction of the cutter 16. Teeth 21 and 22 are offset relative to each other transversely to the axis of rotation 19 (see Figure 7 ), such that the breast surfaces 26a, 26b of the two teeth 21, 22 span a common plane in which the axis of rotation 19 lies. In particular in Figure 7It is clearly visible that the cutting edge 23 of the first tooth 21 and the cutting edge 24 of the second tooth 22 meet at the tip of the distal end 20 precisely where the axis of rotation 19 penetrates the distal end 20. The axis of rotation 19 lies in the plane of the thoracic surface 26a and the thoracic surface 26b.
[0040] The back surface 27a / 27b is inclined in the axial direction relative to the front surface 26a / 26b by a tooth longitudinal angle g' between 4° and 12.5°, so that the cutter head 18 has a total tooth thickness angle g between 8° and 25° (see Figure 8 ). Furthermore, the dorsal surface 27a / 27b is oriented relative to the thoracic surface 26a / 26b in a direction transverse to the axis of rotation 19 by a tooth transverse angle α between 0° and 10° (see Figure 7) inclined. The tooth thickness S' of tooth 21 at the distal end 20 is diameter-dependent and is approximately 1 / 10 (one tenth) of the diameter D of the milling cutter head 18. The tooth thickness S' of tooth 22 at the distal end 20 is also diameter-dependent and is approximately 1 / 10 (one tenth) of the diameter D of the milling cutter head 18. The total milling cutter head thickness S of the milling cutter head 18 is therefore approximately 2 / 10 of the diameter D (see Figure 4 ). The distal end 20 of the milling head 18 is designed as a point with a point angle c of 90° to 150° (see Figure 6 The cutting edges 23, 24 each extend from the tip at the distal end 20 over a clearance angle d of 110° to 170° in the direction of the cutter shank 17 (see Figure 6 ).
[0041] Between the thoracic surface 26a of tooth 21 and the posterior surface 27b of tooth 22, a step 28a or shoulder 28a with a shoulder surface 29a is formed, extending proximally from the distal end 20 along the axis of rotation 19. Between the thoracic surface 26b of tooth 22 and the posterior surface 27a of tooth 21, a step 28b or shoulder 28b with a shoulder surface 29b is formed, extending proximally from the distal end 20 along the axis of rotation 19. The transition from the thoracic surface 26a, 26b to the shoulder surface 29a, 29b is rounded and is inclined at an angle f relative to the axis of rotation 19 and lying in the plane of the thoracic surface 26a, 26b in a range of 2° to 10° (see Figure 6 ) arranged. The shoulder surface 29a, 29b is also located in a tooth chest angle e lying in a plane transverse to the axis of rotation 19 in a range of 110° to 160° (see Figure 5) arranged. The clearance angle b of the respective cutting edge 23, 24 lies in a range of 0° to 30° and is formed circumferentially, that is, over the entire range of the clearance angle d (see Figure 7 ). The transition from the chest area 26a, 26b to the shoulder area 29a, 29b is rounded, which improves material removal and suitability for cleaning.
[0042] In Figure 7It is clearly visible that, in the direction of rotation, a chip space 30a is formed in front of the first tooth 21 between its breast surface 26a and its shoulder surface 29a. This space provides material for material removed by the first tooth 21 of the milling cutter 16 and its cutting edge 23, and together with a region 31a behind the back surface 27b of the adjacent tooth 22, forms a total chip space 30a / 31a. Furthermore, in the direction of rotation, a chip space 30b is formed in front of the second tooth 22 between its breast surface 26b and its shoulder surface 29b. This space provides material for material removed by the second tooth 22 of the milling cutter 16 and its cutting edge 24, and together with a region 31b behind the back surface 27a of the adjacent tooth 21, forms a total chip space 30b / 31b. Figure 18 shows the view of Figure 7without reference numerals, in which the clearances 30a, 30b, the areas 31a, 31b and the chip spaces 30a / 31a, 30b / 31b of both teeth 21, 22 of the milling cutter 16 are identified with corresponding hatching (chip spaces 30a, 30b: marked with hatching, areas 31a, 31b: marked with checkering). Figure 7 It is also evident that the chip space 30a, 30b extends on the side of the axis of rotation 19 facing the respective cutting edge 23, 24 from the cutting edge 23, 24 to a region on the side of the axis of rotation 19 facing away from the cutting edge 23, 24, and that each chip space 30a, 30b is formed on the cutting edge side of the axis of rotation 19 and extends at least in a distal region to the side of the axis of rotation 19 facing away from the respective cutting edge 23, 24. While in the Figures 3 to 10Parts belonging to the first tooth 21 are marked with the reference suffix a, parts belonging to the second tooth 22 are marked with the reference suffix b, for example the breast surface 26a is that of the first tooth, while the breast surface 26b is that of the second tooth 22.
[0043] The Figures 11 to 14 Figure 1 shows a further embodiment of a milling cutter 34 according to the invention. The milling cutter 34 has a milling shank 35 proximally and a milling head 36 distally. The milling cutter 34 has a longitudinal axis 37, which is also its axis of rotation 37 during operation. The milling shank 35 extends coaxially to the axis of rotation 37, which centrally penetrates the milling head 36 at its distal end 38 (see in particular in Figure 1). Figure 11 ).
[0044] The milling cutter head 36 has a first tooth 39 and a second tooth 40. Tooth 39 has a cutting edge 41 for rotary material removal. Tooth 40 has a cutting edge 42 for rotary material removal. The two teeth 39 and 40, and thus also the cutting edges 41 and 42, are arranged in a common plane, at the center of which lies the axis of rotation 37, on diametrically opposite sides of the axis of rotation 37 of the milling cutter 34. The cutting edges 41 and 42 are each located on the side of the respective tooth 39 and 40 facing away from the axis of rotation. The cutting edges 41 and 42 are each arc-shaped. They begin at the distal end 38 on the axis of rotation 37 and initially extend from distal-radial-inside to proximal-radial-outside, then continue in an arc shape from the widest point 43 of the cutter head 34 to the cutter shaft 35.The cutting edges 41 and 42 are each unhelical and free of helical twist. Due to this shape of the cutting edges 41 and 42, the milling cutter 34, when rotating about its axis of rotation 37, has a path of essentially spherical shape.
[0045] Teeth 39 and 40 are identically formed, as is particularly evident in Figures 11 and 12As can be seen, flat surfaces are incorporated into the milling cutter head 36 on diametrically opposite sides of the axis of rotation 37. The milling cutter head 36 therefore has two opposing, flat surfaces 44, 45, which are parallel to each other in a direction transverse to the axis of rotation 37 and inclined to each other in the direction of the axis of rotation 37. The surfaces 44, 45 and the cutting edges 41, 42 are arranged and designed such that surface 44 forms the face surface of the cutting edge 41 and the back surface of the cutting edge 42, and surface 45 forms the face surface of the cutting edge 42 and the back surface of the cutting edge 41.
[0046] Surface 44 is offset from surface 45 in the axial direction by a tooth thickness angle h between 0° and 20° (see Figure 12 ) inclined. The cutter head thickness S of the cutter head 34 at the tip at the distal end 38 is between 0.05 mm and 1.0 mm (see Figure 12). The distal end 38 of the milling head 36 is designed as a point with a point angle i of 90° to 160° (see Figure 13 The cutting edges 41, 42 each extend from the tip 43 at the distal end 38 over a clearance angle j of 110° to 170° in the direction of the cutter shank 35 (see Figure 13 The cutter head 36 has a diameter D at its widest point. The length L of the cone, i.e., the extent of the surfaces 44, 45 in the direction of the axis of rotation 37, is approximately 7 / 9D (seven-ninths of the diameter D). The surfaces 44, 45 transition into the cutter shank 35 with a radius R, where the radius R corresponds to approximately half the diameter D. The clearance angle k of the cutting edges 41, 42 is in a range of 0° to 30° and is continuous, that is, over the entire range of the clearance angle j (see Figures 13 and 14 ).
[0047] In Figure 14It is clearly visible that, in the direction of rotation, a chip space 30a is formed in front of the first tooth 39 as a clearance space, which provides material removed by the first tooth 39 of the milling cutter 34 and its cutting edge 41, and together with a region 31a behind the adjacent tooth 40 forms a total chip space 30a / 31a. Furthermore, in the direction of rotation, a chip space 30b is formed in front of the second tooth 40 as a clearance space, which provides material removed by the second tooth 40 of the milling cutter 34 and its cutting edge 42, and together with a region 31b behind the adjacent tooth 39 forms a total chip space 30b / 31b. Figure 19 shows the view of Figure 14without reference numerals, in which the clearances 30a, 30b, the areas 31a, 31b and chip spaces 30a / 31a, 30b / 31b of both teeth 39, 40 of the milling cutter 34 are identified with corresponding hatching (chip spaces 30a, 30b: marked with hatching, areas 31a, 31b: marked with checkering).
[0048] The Figures 15 and 16 show a variant of the embodiment described above. Figures 3 to 8, in which the cutting edge 23 of tooth 21 has interruptions in the form of grooves 32a, 32b and the cutting edge 24 of tooth 22 has interruptions in the form of grooves 33a, 33b, 33c. The grooves 32a and 32b as well as the grooves 33a, 33b and 33c are each spaced apart from each other by the cutting portions remaining between them. They are also incorporated centripetally into the corresponding teeth 21, 22 and interrupt the cutting edges 23, 24. The grooves 32a and 32b of the first tooth 21 are offset relative to the grooves 33a, 33b and 33c of the second tooth 22 in the circumferential direction of the cutting edges 23, 24, such that remaining cutting edges of the second tooth 22 are positioned at the locations corresponding to the grooves 32a, 32b of the first tooth 21, and remaining cutting edges of the first tooth 21 are positioned at the locations corresponding to the grooves 33a, 33b, 33c of the second tooth 22. This enables particularly uniform material removal.With regard to the remaining features, the embodiments of the . Figures 3 to 8 and the Figures 15 and 16 It should be noted that within the scope of the invention, the embodiment of the Figures 11 to 14 may be provided with such grooves 32a, 32b, 33a, 33b, 33c.
[0049] The Figure 17 shows a variant of the embodiment of Figures 15 and 16 , in which only one groove 32a, 33a is provided in each of the cutting edges 23, 24. This enables a particularly uniform material removal. With regard to the other features, the embodiments of the Figures 3 to 8 and the Figure 17 It should be noted that within the scope of the invention, the embodiment of the Figures 11 to 14 may be provided with such grooves 32a, 33a.
[0050] The Figures 20, 21 , 22 and 23 show a further embodiment of a milling cutter 46 according to the invention, which is in particular different from the one described in Figure 2The single-flute cutter 10 shown is to be distinguished from the cutter 46. The cutter 46 has a cutter shank 47 proximally and a cutter head 48 distally. It also has a longitudinal axis 49, which is simultaneously its axis of rotation 49 during operation. The cutter head 48 is formed by two symmetrically opposed flattenings extending to just before the axis of rotation 49, with an additional pointed surface 66 that reaches to the axis of rotation 49 at the tip 53 with the clearance angle m, and has a cutting edge 50b, on the opposite side of which another cutting edge 50a is formed. Both cutting edges 50a, 50b have the same shape and dimensions, in particular the same diameters, and together with the pointed surface 66 form a common top surface 51. On the side opposite the top surface, they together form a substantially flat back surface 52. As shown in particular in the Figure 21 and 22As shown, the back surface 52 is smaller than the face surface 51, so that a clearance angle k is formed on each of the cutting edges 50a, 50b. The face surface forms a clearance space / surface for each of the cutting edges 50a, 50b. The leading edge 53 of the cutter head 48, which can also be referred to as the tip 53, is preferably also designed as a cutting edge, so that a cutting action in the axial direction, i.e., in the direction of the axis of rotation 49, can be achieved. This can be achieved, for example, by ensuring that both cutting edges 50a, 50b extend exactly to the axis of rotation 49. The chip spaces 54a, 54b and the clearance spaces 55a, 55b of both cutting edges 50a, 50b are integrated into the Figure 21 marked.
[0051] The milling cutter 46 is thus designed for both clockwise and counterclockwise rotation, meaning it cuts in both directions. Due to its shape, the mass of the milling cutter head 48 is minimal because the pointed end 66 is symmetrical about the axis of rotation 49, resulting in very smooth running. Furthermore, the milling cutter head 48 can be designed with surprisingly small dimensions, particularly with a diameter smaller than, for example, 3 mm, 4 mm, or 5 mm.
[0052] The Figures 24, 25, 26 and 27 show a further embodiment of a milling cutter 56 according to the invention, which is also based on the one described in Figure 2 The single-flute cutter 10 shown is to be distinguished from the one shown. The milling cutter 56 is similar to the one in the Figures 20 and 21The milling cutter 46 shown is designed for both clockwise and counterclockwise rotation, meaning it cuts in both directions. It has a proximal shank 57 and a distal head 58. It also has a longitudinal axis 59, which is simultaneously its axis of rotation 59 during operation. The head 58 is formed by two opposing flattened surfaces, one forming a breast surface 61 and the other a back surface 62. Between the breast surface 61 and the back surface 62, a cutting edge 60b is formed on one side of the head 58, and another cutting edge 60a is formed on the opposite side. The distal end of the head 58 is shaped like a point 63. The special feature of the milling cutter 56 is that its breast surface 61 lies on the axis of rotation 59 at the point 63.It can be said that the breast surface 61, the cutting edges 60a, 60b and the axis of rotation 59 meet at the tip 63. The two cutting edges 60a, 60b have the same shape and dimensions, in particular the same diameters. As shown in particular in . Figure 24 As shown, the back surface 62 is smaller than the face surface 61, so that a clearance angle m is formed on each of the cutting edges 60a, 60b. The face surface forms a clearance space / surface for each of the cutting edges 60a, 60b. The leading edge or tip 63 of the cutter head 58 is preferably also designed as a cutting edge, so that a cutting action in the axial direction, i.e., in the direction of the axis of rotation 59, can be effected. The chip spaces 64a, 64b and the clearance spaces 65a, 65b of both cutting edges 60a, 60b are in the Figure 24 marked.
[0053] The cutter head 58 has a cutter head thickness S at its tip 63. Starting from the tip 63, the top surface 61 and the back surface 62 are inclined to each other by a tooth thickness angle h. Furthermore, the top surface 61 is inclined relative to the axis of rotation 59 by an upper tooth thickness angle n, and the back surface 62 is inclined relative to the axis of rotation 59 by a lower tooth thickness angle o, such that the relationship h = n + o applies.
[0054] Due to its shape, the milling cutter 56 has a somewhat less favorable mass distribution with regard to eccentricity than the one in the Figures 20 and 21 The milling cutter 46 shown, however, has better cutting properties in the direction of the rotation axis 59. The milling cutter head 58 can also be designed with surprisingly small dimensions, in particular with a diameter smaller than, for example, 3 mm, 4 mm or 5 mm. Reference symbol list
[0055] 1 Rose cutter 2 Cutter shank 3 Cutter head 4 Longitudinal axis, rotational axis 5 Teeth 6 Distal tip 7 Cutting edges 8 Tooth gap 9 Distal end 10 Single flute 11 Cutter shank 12 Cutter head 13 Longitudinal axis, rotational axis 14a Recessed edge 14b Cutting edge for clockwise rotation 15 Breast surface 16 Cutter 17 Cutter shank 18 Cutter head 19 Longitudinal axis, rotational axis 20 Distal end 21 First tooth 22 Second tooth 23 Cutting edge 24 Cutting edge 25 Widest point 26a Breast surface of first tooth 21, 39 26b Breast surface of second tooth 22, 40 27a Back surface of first tooth 21, 39 27b Back surface of second tooth 22, 40 28a Step / Shoulder of the first tooth 21, 39 28b Step / Shoulder of the second tooth 22, 40 29a Shoulder surface of the first tooth 21, 39 29b Shoulder surface of the second tooth 22, 40 30a Chip space of the first tooth 21, 39 30b Chip space of the second tooth 22, 40 31a,b Clearance behind back surfaces 32a,b Groove 33a,b,c Groove 34 Cutter 35 Cutter shank 36 Cutter head 37 Longitudinal axisRotation axis 38 Distal end 39 First tooth 40 Second tooth 41 Cutting edge 42 Cutting edge 43 Widest point 44 Surface 45 Surface 46 Cutter 47 Cutter shank 48 Cutter head 49 Longitudinal axis, rotation axis 50a, 50b Cutting edge 51 Breast surface 52 Back surface 53 Leading edge, tip 54a, 54b Chip space 55a, 55b Clearance 56 Cutter 57 Cutter shank 58 Cutter head 59 Longitudinal axis, rotation axis 60a, 60b Cutting edge 61 Breast surface 62 Back surface 63 Leading edge, tip 64a, 64b Chip space 65a, 65b Clearance 66 Pointing surface, Pointing a Tooth cross angle b Clearance angle c Tip angle d Clearance angle eTooth face angle fSetting angle gTooth thickness angle g'Tooth longitudinal angle hTooth thickness angle iCep angle jClearance angle kClearance angle LLeCone length mPoint angle nRober tooth thickness angle oLower tooth thickness angle DDiameter RRadius SCutter head thickness S'Tooth thickness
Claims
1. A surgical milling cutter (16, 34, 46, 56) having a shaft (17, 35, 47, 57) for rotationally driven coupling with a drive unit about a rotational axis (19, 37, 49, 59) extending in a longitudinal direction of the shaft (17, 35, 47, 57) and a cutter head (18, 36, 48, 58) arranged distally on the shaft (17, 35, 47, 57), the cutter head (18, 36, 48, 58) having at least two teeth (21, 22, 39, 40) with respective cutting edges (23, 24, 41, 42, 50a, 50b, 60a, 60b) for rotationally removing tissue, the cutting edges (23, 24, 41, 42, 50a, 50b, 60a, 60b) each being designed for the removal of tissue both in the distal direction and in the lateral direction, a chip space (30a, 30b, 54a, 54b) being formed as clearance in each case between adjacent teeth (21, 22, 39, 40) in the circumferential direction, wherein each chip space (30a, 30b, 54a, 54b) extends on the side of the rotational axis (19, 37, 49, 59) facing the respective cutting edge (23, 24, 41, 42, 50a, 50b, 60a, 60b) from the cutting edge (23, 24, 41, 42, 50a, 50b, 60a, 60b) into a region on the side of the rotational axis (19, 37, 49, 59) facing away from the cutting edge (23, 24, 41, 42, 50a, 50b, 60a, 60b), characterized in that the teeth (21, 22, 39, 40) are offset relative to each other transversely to the rotational axis (19, 37) in such a way that front surfaces (26a, 26b, 44, 45) of the teeth (21, 22, 39, 40) span a common plane in which the rotational axis (19, 37) lies.
2. The surgical milling cutter (16, 34, 46, 56) according to claim 1, characterized in that the cutting edges (23, 24, 41, 42, 50a, 50b, 60a, 60b) are each arcuate from distal-radial-inward to proximal-radial-outward and / or are each non-helical and twist-free.
3. The surgical milling cutter (16, 34, 46, 56) according to claim 1 or 2, characterized in that the milling cutter (16, 34, 46, 56) has exactly two teeth (21, 22, 39, 40) arranged on diametrically opposite sides of the rotational axis (19, 37, 49, 59) of the milling cutter (16, 34, 46, 56).
4. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the front surface (26a, 26b, 44, 45, 51) of the tooth (21, 22, 39, 40) in the cutting direction is substantially flat and / or a step (28a, 28b) extending in the proximal direction starting at the distal part at the rotational axis (19, 37) and is arranged relative to the rotational axis (19, 37) at a setting angle (f) of 2° to 10° lying in the plane of the front surface (26a, 26b).
5. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the teeth (21, 22, 39, 40) lie transversely to the rotational axis (37) diametrically opposite each other without offset and in particular are formed in such a way that a front surface (26a) of one tooth (39) and a rear surface (27b) of the other tooth (40) together form a flat surface (44), and the rear surface (27a) of one tooth (39) and the front surface (26b) of the other tooth (40) together form a flat surface (45).
6. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that at least one of the cutting edges (23, 24, 41, 42) has at least one interruption (32a, 32b, 33a, 33b, 33c) or flute (32a, 32b, 33a, 33b, 33c), which is incorporated into the tooth (21, 22, 39, 40) in the centripetal direction, causes a reduction in the length of the cutting edges and thus serves to reduce the feed force.
7. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the thickness of the tooth (21, 22, 39, 40) increases with a tooth thickness angle (g, h) of 1° to 10° relative to the rotational axis (19, 37) from distal to proximal.
8. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the distal thickness of the tooth (21, 22, 39, 40) is between 1 / 20 and 1 / 10 of the diameter (D) of the cutter head (18, 36) in the radial direction.
9. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the cutting edge (23, 24, 41, 42) has a constant relief angle (b, k) of 2° to 30° along the cutting edge (23, 24, 41, 42) or the cutting edge (23, 24, 41, 42) has a relief angle (b, k) in a range of 2° to 30° that varies along a course of the cutting edge (23, 24, 41, 42).
10. The surgical milling cutter (16) according to any of the preceding claims, characterized in that the cutting edge (23, 24) has a rake angle of 0°.
11. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the cutter head (18, 36) has a tip with a tip angle (c, i) of 110° to 150° at its distal end (20, 38).
12. The surgical milling cutter (16, 34) according to any of the preceding claims, characterized in that it is rotationally symmetrical to the rotational axis (19, 37).
13. The surgical milling cutter (46, 56) according to any of the preceding claims, characterized in that it has a first cutting edge (50a, 60a) which effects tissue removal in a first direction of rotation, and has a second cutting edge (50b, 60b) which effects tissue removal in a second direction of rotation opposite to the first direction of rotation.
14. The surgical milling cutter (16, 34, 46, 56) according to any of the preceding claims, characterized in that the cutter head (18, 36, 48, 58) has a flame-shaped, coneshaped, olive-shaped or roller-shaped cross-sectional shape in a cross-section through the rotational axis (19, 37, 49, 59).