CN115517736B

CN115517736B - Skull drill

Info

Publication number: CN115517736B
Application number: CN202211123001.6A
Authority: CN
Inventors: 宋春辉; 王航
Original assignee: Beijing Pinchi Medical Equipment Co ltd; Beijing Pins Medical Co Ltd
Current assignee: Beijing Pinchi Medical Equipment Co ltd; Beijing Pins Medical Co Ltd
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2025-12-05
Anticipated expiration: 2042-09-15
Also published as: CN115517736A

Abstract

The embodiment of the invention discloses a skull drill, which is used for machining a skull by utilizing a plurality of first cutting edges circumferentially arranged on a positioning table so as to cut a counter bore at one end of the outside of a skull opening in a rotary cutting mode. Therefore, on one hand, the craniotomy position can form a counter bore for accommodating the fixing device of the implantation instrument, the volume of the fixing device outside the skull is reduced, the postoperative aesthetic property is improved, and the wound healing is facilitated. On the other hand, the positioning table is matched with the reserved cranium opening during rotary cutting, so that the counter bore can be close to or keep the same axis with the reserved cranium opening, and the mounting precision of the implantation instrument fixing device is improved. In still another aspect, the table surface of the counter bore is cut to be an arc surface through the first cutting edge, so that the shape of the counter bore can be more fit with the radian of the skull. After the mounting surface of the implantation instrument fixing device is set to a shape corresponding to the mounting surface, the adaptability of the implantation instrument fixing device to the skull bone can be further ensured.

Description

Skull drill bit

Technical Field

The invention relates to the field of medical instruments, in particular to a skull drill bit.

Background

The electrodes are implanted into the brain of a person, and various diseases including parkinson's disease, epilepsy, dystonia, depression and the like can be treated by electric stimulation of the brain by the electrodes, and the electrodes are left in the brain for a long time and are fixed by using a fixing device. The craniotomy which penetrates through the skull is formed in the operation, and is limited by surgical instruments, and most craniotomies formed in the operation have poor suitability with the fixing device, so that the fixing device is obviously protruded out of the skull, and the attractiveness and wound healing are affected.

Disclosure of Invention

In view of this, the embodiment of the invention provides a skull drill bit, which is used for machining a step hole with an arc-shaped table surface and positioned at a craniotomy by utilizing a first cutting edge positioned at a cutting knife and a positioning table matched with the first cutting edge.

The skull drill bit of the embodiment of the invention comprises:

The positioning table is rotationally arranged or fixedly arranged on the head of the skull drill bit and is opposite to the rotation axis of the skull drill bit;

the plurality of cutters are circumferentially arranged along the head of the skull drill bit and comprise first cutting edges, one ends of the first cutting edges extend to the side wall positions of the positioning table, the other ends of the first cutting edges incline towards the table top direction of the positioning table, and meanwhile, the first cutting edges bend towards the reverse direction of the table top of the positioning table.

Further, the skull drill bit has a chip-receiving region located between adjacent two of the cutting blades and adjacent the first cutting edge to the locating table.

Further, the first cutting edge is bent in a direction opposite to the rotary cutting direction of the cutting blade, and the chip accommodating area is formed at a position where the first cutting edge is connected with the positioning table.

Further, the cutting blade comprises a first avoidance surface, and the first cutting edge is positioned at the edge of the first avoidance surface;

The first avoiding surface faces to the rotary cutting direction of the cutting knife.

Further, the cutting blade comprises a second avoidance surface, and the intersection position of the second avoidance surface and the first avoidance surface forms the first cutting edge;

the second avoidance surface is positioned on one side of the cutting blade, which is close to the table top of the positioning table, and one side of the second avoidance surface, which is far away from the first cutting edge, is inclined towards the direction away from the table top of the positioning table.

Further, a third avoidance surface facing to the outer side is arranged in the circumferential direction of the cutting blade, the third avoidance surface intersects with the first avoidance surface to form a second cutting edge, the second cutting edge is arranged in the thickness direction of the cutting blade, and one side, away from the second cutting edge, of the third avoidance surface is inclined towards the rotation axis of the skull drill bit.

Further, the second cutting edge includes a tip;

one end of the second cutting edge, which is close to the table surface of the positioning table, is connected with one end of the first cutting edge, which is far away from the positioning table, so as to form the tip.

Further, an end of the second cutting edge remote from the tip is inclined toward a rotational axis of the skull drill.

Further, the side wall of the positioning table comprises a cylindrical surface;

The plurality of cutting blades are three cutting blades, and the three cutting blades are uniformly distributed along the circumferential direction of the positioning table.

Further, the skull drill bit further comprises:

The driving handle comprises a driving end and a connecting end which are oppositely arranged, wherein the connecting end and the positioning table are respectively positioned on two opposite sides of the head of the skull drill bit, the driving end is provided with a guide step and a fixing column, the guide step is convexly arranged on the end face of the driving end, the guide step is convexly provided with a fixing column, and the circumferential direction of the fixing column is provided with a connecting groove.

According to the skull drill provided by the embodiment of the invention, the skull is processed by utilizing the plurality of first cutting edges circumferentially arranged on the positioning table, so that a counter bore is cut at one end of the outside of the craniotomy in a rotary cutting mode. Therefore, on one hand, the craniotomy position can form a counter bore for accommodating the fixing device of the implantation instrument, the volume of the fixing device outside the skull is reduced, the postoperative aesthetic property is improved, and the wound healing is facilitated. On the other hand, the positioning table is matched with the reserved cranium opening during rotary cutting, so that the counter bore can be close to or kept concentric with the reserved cranium opening, and the installation accuracy of the implantation instrument fixing device is improved. In still another aspect, the table surface of the counter bore is cut to be an arc surface through the first cutting edge, so that the shape of the counter bore can be more fit with the radian of the skull. After the mounting surface of the implantation instrument fixing device is set to a shape corresponding to the mounting surface, the adaptability of the implantation instrument fixing device to the skull bone can be further ensured.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a related art implant device fixture in a pre-and post-donned state;

fig. 2 is a schematic cross-sectional view of a related art insertion instrument holder

FIG. 3 is a perspective view of the state of the skull drill bit borehole in accordance with an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of an embodiment of the invention at D-D in FIG. 3;

FIG. 5 is an enlarged schematic cross-sectional view of the state of drilling of a skull drill in accordance with an embodiment of the invention;

FIG. 6 is a schematic illustration of the structure of one side of a skull drill in an embodiment of the invention;

FIG. 7 is a schematic view of the other side of the skull drill in accordance with an embodiment of the invention;

fig. 8 is a schematic view of the structure of the other side of the skull drill in accordance with an embodiment of the invention.

Reference numerals illustrate:

1-a cutting blade;

11-a first cutting edge, 12-a chip containing area, 13-a first avoiding surface, 14-a second avoiding surface, 15-a third avoiding surface, 16-a second cutting edge and 17-a tip;

2-a positioning table;

3-driving handle, 31-driving end, 311-guiding step, 312-fixing column, 3121-connecting slot and 32-connecting end;

a-head, A1-skull, A2-craniotomy, A3-mesa;

B-rotation axis and C-implantation instrument fixing device.

Detailed Description

The present invention is described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in detail. The present invention will be fully understood by those skilled in the art without the details described herein. Well-known methods, procedures, flows, components and circuits have not been described in detail so as not to obscure the nature of the invention.

Moreover, those of ordinary skill in the art will appreciate that the drawings are provided herein for illustrative purposes and that the drawings are not necessarily drawn to scale.

Unless the context clearly requires otherwise, the words "comprise," comprising, "and the like throughout the specification are to be construed as including, rather than being exclusive or exhaustive, that is to say, as" including but not limited to.

In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

Unless specifically stated or limited otherwise, the terms "mounted," "connected," "secured" and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed, or may be directly connected, or may be indirectly connected through intervening media, or may be in communication between two elements or the relationship of two elements to each other, unless otherwise specifically stated. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

Spatially relative terms, such as "inner," "outer," "lower," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In the operation of the implant device, a wound is made in the human body so as to put the implant device, which includes the electrode, inside the human body. Taking the example of a brain implant electrode, a wound, i.e., craniotomy A2, is made in the skull A1 of the patient during the operation. Craniotomy A2 allows the brain of the patient to communicate with the outside.

The existing electrode fixing device is protruded on the skull A1 after being installed, and the part protruded outside the skull can further act on human body parts such as hair or scalp, so that the skull opening A2 and the nearby positions are damaged and ulcerated. Meanwhile, the movement of the patient during wearing can also affect the electrode and the electrode fixing device, for example, the hand can collide with the electrode fixing device when moving nearby the head A.

Fig. 1 and 2 are perspective views showing a state before and after wearing and a sectional view showing an implant device fixing apparatus in the related art. 1-2, in order to allow the insertion instrument holder to be submerged inside the craniotomy A2, the present embodiment provides a stepped hole (as shown in the right view of FIG. 1) in the craniotomy A2, the stepped hole having a mesa A3 that allows the insertion instrument holder to be submerged therein. The top of the insertion instrument holder in the stepped bore may conform well to the contour of the patient's head a (as shown in the left view of fig. 1). Fig. 2 is a view of an insertion instrument holder that may be disposed in the stepped bore. The whole fixing device of the implantation instrument in the figure is in a flat structure, and the flange bottoms on two sides can sink into the table top A3 of the step hole, so that the flange bottoms are arranged to be cambered surfaces which are matched with the table top A3.

Fig. 3-4 are perspective and cross-sectional views of the state of the burr drilling. Fig. 6-8 are schematic views of the skull drill in different orientations. The head of the skull drill in the figure is provided with a cutter, the tail of the skull drill faces upwards, and the tail can be driven to rotate by a hand or motor and other driving modes (not shown in a driving mechanism diagram) so as to drive the head to make rotary cutting action on the skull A1. Fig. 5 is an enlarged schematic cross-sectional view of the state of the burr drilling. Table A3 in the figure is formed after the skull is cut by the tool.

In some embodiments, as shown in fig. 1-8, the skull drill bit in this example includes a locating table 2 and a plurality of cutters 1. The positioning table 2 is arranged on the head of the skull drill bit and is opposite to the rotation axis B of the skull drill bit. The plurality of cutters 1 are arranged along the head circumference of the skull drill bit and the cutters 1 comprise a first cutting edge 11, one end of the first cutting edge 11 is connected with the side wall of the positioning table 2, the other end is inclined towards the table top direction of the positioning table 2, and simultaneously the first cutting edge 11 is reversely bent towards the table top of the positioning table 2.

The bending direction of the first cutting edge 11 of the present embodiment is the bending direction of the cutting blade 1 shown in fig. 5. The cutting blade 1 has a first curvature in the bending direction, i.e. the plane in which the first curvature lies passes through the rotation axis B of the skull drill bit. When the skull drill bit rotates, the positioning table 2 of the skull drill bit is penetrated in the reserved craniotomy A2, so that the side wall of the positioning table 2 is matched with the inner wall of the reserved craniotomy A2, and the rotation axis B of the cutting knife 1 is coincident with or nearly coincident with the center of the reserved craniotomy A2. The internal diameter of the preformed cranium can be between 12mm and 20 mm.

In other embodiments, the positioning table 2 is rotatably mounted to the head of the skull drill. That is, the positioning table 2 has a degree of freedom of rotation on the rotation axis B. At this time, one end of the first cutting edge 11 extends to the side wall of the positioning table 2, so as to ensure the radian integrity of the processed table top A3. Therefore, when the skull drill bit is used for processing the table top A3, the positioning table 2 can be kept in a static state or a nearly static state in the craniotomy A2 by utilizing the positioning table 2 capable of rotating, so that the friction between the side wall of the positioning table 2 and the side wall of the craniotomy A2 is avoided, and secondary damage is prevented.

Alternatively, the positioning table 2 may be rotatably connected to the head of the skull drill by plastic bearings (not shown).

According to the skull drill bit provided by the embodiment of the invention, the skull A1 is processed by utilizing the plurality of first cutting edges 11 which are circumferentially arranged on the positioning table 2, so that a counter bore is cut at one end of the skull opening A2, which is close to the outer side. Therefore, on one hand, the skull opening A2 can form a counter bore for accommodating the fixing device of the implantation instrument, the volume of the fixing device outside the skull opening A1 is reduced, the postoperative aesthetic property is improved, and the wound healing is facilitated. On the other hand, the positioning table 2 is matched with the reserved craniotomy A2 during rotary cutting, so that the counter bore can be close to or kept concentric with the reserved craniotomy A2, and the installation accuracy of the implantation instrument fixing device is improved. On the other hand, the table surface A3 of the counter bore is cut into an arc surface by the first cutting edge 11, so that the shape of the counter bore can be more fit with the radian of the skull. After the mounting surface of the implantation instrument fixture is set to a shape corresponding thereto, the adaptability of the implantation instrument fixture to the skull bone A1 can be further ensured.

In some embodiments, as shown in fig. 1-8, the skull drill bit has a chip-receiving region 12, the chip-receiving region 12 being located between two adjacent cutting blades 1 and adjacent the positioning table 2 at the first cutting edge 11. The chip-receiving area 12 of the present embodiment is arranged immediately adjacent to the first cutting edge 11, i.e. in front of the rotary cutting direction (indicated by the arrow in fig. 6) of the first cutting edge 11. Therefore, when the cutting knife 1 rotates the skull A1, generated skull A1 scraps can be contained in the scraps containing area 12, so that the skull scraps can be cleaned conveniently in the operation, and the falling of the skull A1 scraps is reduced.

Further, the first cutting edge 11 is curved in the opposite direction of the rotary cutting of the cutting blade 1, and a chip receiving region 12 is formed at a position where the first cutting edge 11 is connected to the positioning table 2. The first cutting edge 11 in this embodiment further has a second curvature in its rotation direction, and the second curvature makes the skull A1 fragments generated by the first cutting edge 11 not scatter outwards, but gather towards the connection position of the cutting knife 1 and the positioning table 2, so that the cleanliness of the operation is further improved, and the skull A1 fragments located in the fragment containing area 12 are convenient to be intensively treated.

In some embodiments, as shown in fig. 1-8, the cutting insert 1 includes a first relief surface 13, and the first cutting edge 11 is located at an edge of the first relief surface 13. The first relief surface 13 faces the rotary cutting direction of the cutting blade 1. Specifically, in this embodiment, the bottom of the first relief surface 13 is used to form the first cutting edge 11, and the shape of the first relief surface 13 is adapted to the first curvature and the second curvature of the first cutting edge 11.

Further, the cutting insert 1 includes a second relief surface 14, and a first cutting edge 11 is formed at a position where the second relief surface 14 intersects with the first relief surface 13. The second relief surface 14 is located on the side of the cutting insert 1 that is closer to the table top of the positioning table 2, and the side of the second relief surface 14 that is farther from the first cutting edge 11 is inclined in a direction away from the table top of the positioning table 2 (as shown by the region I shown in fig. 8). The second relief surface 14 in this embodiment is located at the bottom of the cutting blade 1, which is opposite to the table surface A3 during the rotary cutting, and the second relief surface 14 is disposed to be raised in a direction away from the table surface A3 in order to reduce friction with the table surface A3 and sharpen the first cutting edge 11.

In some embodiments, as shown in fig. 1-8, the cutting blade 1 has a third relief surface 15 facing outward in the circumferential direction, the third relief surface 15 intersects the first relief surface 13 to form a second cutting edge 16, the second cutting edge 16 is disposed in the thickness direction of the cutting blade 1, and a side of the third relief surface 15 away from the second cutting edge 16 is inclined toward the rotation axis B of the skull drill (as shown in a region III shown in fig. 8). The first cutting edge 11 in the above embodiment can cut the skull A1 to form the table A3, while the second cutting edge 16 provided in the present embodiment is also capable of trimming the side wall of the table A3 as the skull drill is continually advanced intracranially. Therefore, after the skull drill bit finishes drilling, the arc-shaped table surface A3 is formed, and meanwhile, the side wall of the step hole can also have higher dimensional accuracy, so that a mounting foundation is provided for mounting the implantation instrument fixing device. Meanwhile, the avoidance area formed by the third avoidance surface 15 can also effectively avoid the friction between the cutting knife 1 and the circumferential direction of the skull A1.

Preferably, the person skilled in the art can configure the length of the second cutting edge 16 in this embodiment, i.e. the dimension of the third relief surface 15 in the thickness direction of the cutting insert 1, so that it exactly matches the depth of the land A3 of the stepped bore. Thus, when the operator drills the skull A1, the appropriate depth of the drill can be determined according to the height dimension of the third relief surface 15 or the length of the second cutting edge 16. I.e. when the top of the second cutting edge 16 just dips into the skull A1, the punching operation is stopped immediately.

Further, the second cutting edge 16 comprises a tip 17. The end of the second cutting edge 16 close to the table surface of the positioning table 2 is connected to the end of the first cutting edge 11 remote from the positioning table 2 to form a tip 17. In this embodiment the first cutting edge 11 and the second cutting edge 16 of the cutting blade 1 are arranged adjacent to each other, thereby forming a tip at the point of the cutting blade 1. When the skull drill is fed towards the skull A1, the tip 17 can effectively improve the cutting capacity of the skull drill and the cutting efficiency.

Further, the end of the second cutting edge 16 remote from the tip 17 is inclined towards the rotational axis B of the skull drill (as shown in region II in fig. 8). The tip 17 of the present embodiment is composed of three edges, namely, the bottom of the first relief surface 13 (first cutting edge 11), the bottom of the second relief surface 14, and the second cutting edge 16. By the angular disposition of the second cutting edge 16, the tip 17 is made sharper both in the direction of movement and in the thickness direction of the cutting blade 1. Further improving the trimming capability of the side wall of the table top A3.

In some embodiments, as shown in fig. 1-8, the sidewall of the positioning table 2 comprises a cylindrical surface. The plurality of cutters 1 are 3 cutters 1, and the 3 cutters 1 are uniformly distributed along the circumferential direction of the positioning table 2. In the cutting of the skull A1, the cutting blade 1 of the present embodiment can generate the same cutting force in the circumferential direction, thereby ensuring the stability thereof in the feeding direction, and avoiding the wobbling of the skull drill during drilling, thereby causing the non-uniform circumferential depth of the mesa A3 of the stepped hole.

In other embodiments, the number of cutting blades 1 is 4, 5 or more. Those skilled in the art can select the size of the diameter of the craniotomy A2 to maximize cutting efficiency.

In some embodiments, as shown in fig. 1-8, the skull drill bit further comprises a drive shaft 3. The driving handle 3 comprises a driving end 31 and a connecting end 32 which are oppositely arranged, the connecting end 32 and the positioning table 2 are respectively positioned on two opposite sides of the head of the skull drill bit, the driving end 31 is provided with a guide step 311 and a fixing column 312, the guide step 311 is convexly arranged on the end face of the driving end 31, the guide step 311 is convexly provided with the fixing column 312, and the circumference of the fixing column 312 is provided with a connecting groove 3121. Taking a motor as an example, when driving the skull drill, the skull drill may be connected to the driving mechanism by the driving shaft 3 in the present embodiment using the connection groove 3121 to position the skull drill in the axial direction thereof. The torque in the rotational direction can then be transmitted by means of the guide step 311 of the drive end 31. Fig. 7 shows a guide step 311, which guide step 311 has two guide surfaces facing the sides of the drive shaft 3. The torque of the motor can be transmitted to the skull drill bit through the two guide surfaces.

The electrode implantation procedure may be performed using the skull drill in the above-described embodiments, as shown in fig. 1-8, and in an alternative implementation, the electrode implantation procedure includes first, opening a reserved cranium on the skull A1 of the patient, and aligning the skull drill corresponding to the reserved cranium with the reserved cranium. The positioning table 2 is extended into the reserved cranium. Then, the skull drill is turned and a certain pressure is applied to the skull A1. During the rotary cutting of the cutting blade 1, the skull A1 fragments of the chip-holding area 12 are constantly cleaned. Finally, after the perforation is completed, the corresponding electrode fixing device is installed in the craniotomy A2.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, and various modifications and variations may be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A skull drill, characterized in that the skull drill comprises:

a positioning table (2) which is rotatably arranged or fixedly arranged on the head of the skull drill bit and is opposite to the rotation axis (B) of the skull drill bit;

a plurality of cutting blades (1) arranged along the head circumference of the skull drill bit and the cutting blades (1) comprise a first cutting edge (11), one end of the first cutting edge (11) extends to the side wall position of the positioning table (2), the other end of the first cutting edge is inclined towards the table top direction of the positioning table (2), and meanwhile, the first cutting edge (11) is reversely bent towards the table top of the positioning table (2);

The skull drill bit is provided with a chip containing region (12), and the chip containing region (12) is positioned between two adjacent cutting blades (1);

The cutting knife (1) comprises a first avoidance surface (13), a second avoidance surface (14) and a third avoidance surface (15), wherein the first avoidance surface (13) faces the rotary cutting direction of the cutting knife (1), the second avoidance surface (14) is positioned at one side, close to the table surface of the positioning table (2), of the cutting knife (1), and the third avoidance surface (15) is positioned in the circumferential direction of the cutting knife (1) and faces the outer side;

The first avoidance surface (13) is provided with a first edge and a second edge, the first edge is intersected with the second avoidance surface (14) to form the first cutting edge (11), the first cutting edge (11) is bent towards the opposite direction of rotary cutting of the cutting blade (1), the second edge is intersected with the third avoidance surface (15) to form a second cutting edge (16), the second cutting edge (16) is arranged in the thickness direction of the cutting blade (1), and one end, close to the table surface of the positioning table (2), of the second cutting edge (16) is connected with one end, far away from the positioning table (2), of the first cutting edge (11) to form a tip (17);

The shape of the first avoidance surface (13) is adapted to the bending direction of the first cutting edge (11), and the first avoidance surface (13) penetrates through the cutting edge (1) in the thickness direction of the cutting edge (1).

2. A skull drill according to claim 1, characterized in that the chip-receiving area (12) is located adjacent to the positioning table (2) at the first cutting edge (11).

3. A skull drill according to claim 2, characterized in that the connection location of the first cutting edge (11) with the positioning table (2) forms the chip-receiving area (12).

4. A skull drill according to claim 1, characterized in that the side of the second relief surface (14) remote from the first cutting edge (11) is inclined in a direction remote from the table top of the positioning table (2).

5. A skull drill according to claim 1, characterized in that the side of the third relief surface (15) remote from the second cutting edge (16) is inclined towards the rotational axis (B) of the skull drill.

6. A skull drill according to claim 1, characterized in that the end of the second cutting edge (16) remote from the tip (17) is inclined towards the rotational axis (B) of the skull drill.

7. The skull drill according to claim 1, characterized in that the sidewall of the localization table (2) comprises a cylindrical surface;

the plurality of cutting blades (1) are three cutting blades (1), and the three cutting blades (1) are uniformly distributed along the circumferential direction of the positioning table (2).

8. The skull drill according to claim 1, wherein the skull drill further comprises:

The driving handle (3) comprises a driving end (31) and a connecting end (32) which are oppositely arranged, wherein the connecting end (32) and the positioning table (2) are respectively positioned on two opposite sides of the head of the skull drill bit, the driving end (31) is provided with a guide step (311) and a fixing column (312), the guide step (311) is convexly arranged on the end face of the driving end (31), the guide step (311) is convexly provided with the fixing column (312), and the circumference of the fixing column (312) is provided with a connecting groove (3121).