Electric trephine with function of immediate stop of trephine penetration

Abstract

The utility model discloses an electric trephine with a function of immediate stop of trephine penetration, which comprises a transmission part, an outer trephine component, an inner trephine component and a clutch mechanism, the inner trephine component is sleeved in the outer trephine component, the front end of the inner trephine component extends out of the front end of the outer trephine component, and the outer trephine component can synchronously rotate along with the inner trephine component; the clutch mechanism is arranged between the rear end of the inner trephine assembly and the transmission piece and comprises an elastic piece, one end of the elastic piece is connected to the rear end of the inner trephine assembly, and the other end of the elastic piece is connected with the transmission piece. The inner trephine assembly is combined with the transmission part by compressing the elastic part, the transmission part drives the inner trephine assembly to rotate, and when the elastic part is released, the inner trephine assembly is separated from the transmission part, and the inner trephine assembly stops rotating. According to the electric trephine with the function of immediate stopping of trephing, crushing type drilling of bone tissues is reduced, and rapid recovery of a patient after an operation is facilitated; in addition, looping can be stopped immediately, and the operation safety is high.

Description

Technical Field

[0001] This utility model relates to the field of medical technology, and in particular to an electric ring saw with a stop function when passing through a ring. Background Technology

[0002] In interbody fusion surgery, a trephine saw is typically used for osteotomy. Because the bone removed by the trephine saw is relatively intact, it can be repositioned back into the cut area to facilitate patient recovery. Currently, trephine saws used in osteotomy surgery include manual and electric trephine saws. Manual trephine saws rely on manual rotation by medical staff, which is inefficient and labor-intensive. While electric trephine saws can improve surgical efficiency, they lack an automatic stop function. The operator must rely on experience to judge whether the cut has been completed and control the trephine saw to stop, which greatly increases the risk of accidentally injuring surrounding soft tissues, compromising surgical safety. Utility Model Content

[0003] Therefore, it is necessary to provide an electric circumferential saw with an immediate stop function after circumferential insertion, which can improve surgical efficiency while ensuring surgical safety.

[0004] An electric ring saw with a ring-through-stop function includes:

[0005] External ring saw assembly;

[0006] An inner ring saw assembly is fitted inside the outer ring saw assembly, with its front end extending from the front end of the outer ring saw assembly. The outer ring saw assembly can rotate synchronously with the inner ring saw assembly.

[0007] The transmission component is indirectly located at the rear end of the outer ring saw assembly and the inner ring saw assembly;

[0008] A clutch mechanism is disposed between the rear end of the inner ring saw assembly and the transmission member. The clutch mechanism includes an elastic element, one end of which is connected to the rear end of the inner ring saw assembly, and the other end is connected to the transmission member. The inner ring saw assembly engages with the transmission member by compressing the elastic element, and is driven to rotate by the transmission member. When the elastic element is released, the inner ring saw assembly disengages from the transmission member, and the inner ring saw assembly stops rotating.

[0009] In one embodiment, the outer ring saw assembly includes an outer ring saw handle, an outer blade tube, and an outer ring saw head. The rear end of the outer blade tube is connected to the outer ring saw handle, and the front end is connected to the rear end of the outer ring saw head. The front end of the outer ring saw head is provided with outer saw teeth. The inner ring saw assembly includes an inner ring saw handle, an inner blade tube, and an inner ring saw head. The inner ring saw handle is located inside the outer ring saw handle. The rear end of the inner blade tube is connected to the front end of the inner ring saw handle, and the front end is connected to the inner ring saw head. The front end of the inner ring saw head is provided with inner saw teeth.

[0010] In one embodiment, the clutch mechanism includes:

[0011] A first transmission part is disposed at the front end of the transmission component;

[0012] The second transmission unit is located at the rear end of the inner ring saw handle;

[0013] The elastic element is disposed between the first transmission part and the second transmission part.

[0014] In one embodiment, the first transmission part is at least one radially extending transmission groove disposed on the front end face of the transmission member, and the second transmission part is at least one radially extending transmission pin disposed on the rear end of the inner ring saw handle; wherein, when the elastic member is compressed, the transmission pin is engaged in the transmission groove to make the inner ring saw handle cooperate with the transmission member; when the elastic member is released, the transmission pin disengages from the transmission groove to separate the inner ring saw handle from the transmission member.

[0015] In one embodiment, there are two transmission grooves, which are arranged opposite to each other on the diameter line of the transmission component; the inner ring saw handle is provided with a through hole extending radially, and there is one transmission pin, which passes through the through hole and has its two ends extending out of the through hole respectively.

[0016] In one embodiment, the front end of the transmission member is provided with a mounting hole, the rear end of the inner ring saw handle is provided with a mounting post, the elastic element is a spring, one end of the spring abuts against the mounting hole, and the other end is sleeved on the mounting post.

[0017] In one embodiment, the inner ring saw assembly is axially movable relative to the outer ring saw assembly, and further includes a synchronous transmission mechanism disposed between the inner ring saw assembly and the outer ring saw assembly to enable the outer ring saw assembly to rotate synchronously with the inner ring saw assembly.

[0018] In one embodiment, the outer ring saw assembly includes an outer ring saw head and an outer ring saw handle, the inner ring saw assembly includes an inner ring saw head and an inner ring saw handle, the synchronous transmission mechanism includes at least one axially extending slot disposed on the outer ring saw handle, and the inner ring saw handle is provided with a flat pin in the radial direction, the two ends of the flat pin extending into the slot.

[0019] In one embodiment, the device further includes a ring saw housing having a front end and a rear end; wherein the rear end of the outer ring saw assembly extends into the front end of the ring saw housing and is connected to the ring saw housing via a first bearing, and one end of the transmission member extends into the rear end of the ring saw housing and is connected to the ring saw housing via a second bearing.

[0020] In one embodiment, the ring saw housing includes a main body and an outer cover. The rear end of the main body is connected to the front end of the outer cover. One end of the transmission member extends through the outer cover into the rear end of the main body and is connected to the main body. The outer cover is provided with a plug portion.

[0021] The aforementioned electric ring saw with the "stop upon ring penetration" function features an outer ring saw assembly that rotates synchronously with the inner ring saw assembly, and a clutch mechanism is installed between the inner ring saw assembly and the transmission component. When the ring saw penetrates the target area, the pressure on the inner ring saw assembly disappears, triggering the clutch mechanism to automatically disengage the inner ring saw assembly from the transmission component, thus achieving the "stop upon ring penetration" function. Attached Figure Description

[0022] Figure 1 This is a front view of an electric ring saw in one embodiment of the present invention;

[0023] Figure 2 For along Figure 1 Sectional view of the middle BB line;

[0024] Figure 3 for Figure 2 A magnified view of a portion of point A in the middle;

[0025] Figure 4 for Figure 2 A magnified view of a portion of point B in the middle;

[0026] Figure 5 for Figure 2 A magnified view of a portion of point C.

[0027] Explanation of reference numerals in the attached figures:

[0028] 10. Ring saw housing; 11. Outer shell body; 111. Front section; 112. Rear section; 12. Outer cover; 12a. Plug section;

[0029] 20. Outer ring saw assembly; 21. Outer ring saw head; 21a. Outer saw teeth; 22. Outer blade tube; 23. Outer ring saw handle; 23a. Strip groove; 24. First bearing;

[0030] 30. Inner ring saw assembly; 31. Inner ring saw head; 21a. Outer saw teeth; 32. Inner blade tube; 33. Inner ring saw handle; 33a. Mounting post;

[0031] 40. Transmission component; 41. Connection interface; 42. Transmission groove; 43. Mounting hole; 44. Second bearing;

[0032] 50. Drive pin;

[0033] 60. Elastic components;

[0034] 70. Depth limiting component; 71. Depth limiting element; 71a. Stop; 72. Adjusting sleeve; 72a. Spiral groove; 73. Sliding element; 74. Impact element; 75. First limiting sleeve; 76. Second limiting sleeve. Detailed Implementation

[0035] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model are described clearly and completely below with reference to the accompanying drawings. Obviously, the specific details described below are only a part of the embodiments of this utility model, and this utility model can be implemented in many other embodiments different from those described herein. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0036] In this document, when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The directional terms such as "front," "back," "up," and "down" are defined based on the location of the components in the accompanying drawings and their relative positions, and are merely for clarity and convenience in expressing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed by this utility model.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0038] Based on the accompanying drawings, the components in the above embodiments are numbered and the parentheses are removed before the specific implementation is as follows:

[0039] like Figure 1-4As shown, an electric ring saw with a ring-through-stop function in one embodiment of the present invention includes a transmission component 40, an inner ring saw assembly 30, an outer ring saw assembly 20, and a clutch mechanism. The transmission component is indirectly disposed at the rear ends of the outer ring saw assembly and the inner ring saw assembly. The front end of the outer ring saw assembly 20 has multiple outer saw teeth 21a arranged circumferentially. The inner ring saw assembly 30 is fitted inside the outer ring saw assembly 20, with its front end extending from the front end of the outer ring saw assembly 20 and having multiple inner saw teeth 31a arranged circumferentially. The outer ring saw assembly 20 can rotate synchronously with the inner ring saw assembly 30. The clutch mechanism is disposed between the front end of the transmission component 40 and the rear end of the inner ring saw assembly 30. The clutch mechanism includes an elastic element 60, one end of which is connected to the rear end of the inner ring saw assembly 30, and the other end is connected to the transmission component 40. When the inner ring saw assembly 30 is subjected to pressure, the inner ring saw assembly 30 compresses the elastic element 60 and engages with the transmission element 40, transmitting the torque on the transmission element 40 to the inner ring saw assembly 30. When the pressure is removed, the elastic element 60 is released, and the transmission element 40 and the inner ring saw assembly 30 automatically separate.

[0040] The aforementioned electric ring saw with an instant-stop function after circumcision features an outer ring saw assembly 20 that rotates synchronously with the inner ring saw assembly 30, and a clutch mechanism is provided between the inner ring saw assembly 30 and the transmission component 40. When the ring saw pierces the target area, the pressure on the inner ring saw assembly 30 disappears, the elastic element 60 releases, and the inner ring saw assembly 30 automatically separates from the transmission component 40, achieving the instant-stop function after circumcision and ensuring surgical safety. Compared to traditional manual ring saws, this electric ring saw, driven by electricity, significantly improves surgical efficiency while reducing the workload of medical staff.

[0041] In one embodiment, the outer ring saw assembly 20 includes an outer ring saw head 21, an outer blade tube 22, and an outer ring saw handle 23. The front end of the outer blade tube 22 is connected to the outer ring saw head 21, and the rear end is connected to the outer ring saw handle 23. The front end of the outer ring saw head 21 has a plurality of outer saw teeth 21a arranged in a circumferential direction. When the outer ring saw handle 23 rotates, it drives the outer blade tube 22 and the outer ring saw head 21 to rotate, thereby using the rotating outer saw teeth 21a to cut bone tissue. The inner ring saw assembly 30 includes an inner ring saw head 31, an inner blade tube 32, and an inner ring saw handle 33. The inner ring saw handle 33 is located inside the outer ring saw handle 23. The front end of the inner blade tube 32 is connected to the inner ring saw head 31, and the rear end is connected to the inner ring saw handle 33. The front end of the inner ring saw head 31 has a plurality of inner saw teeth 31a arranged in a circumferential direction. The rear end of the inner ring saw head 31 is connected to the front end of the inner ring saw handle 33. When the inner ring saw handle 33 rotates, it drives the inner ring saw head 31 to rotate, thereby using the rotating inner saw teeth 31a to cut bone tissue.

[0042] In one embodiment, the clutch mechanism further includes a first transmission part disposed at the front end of the transmission member 40 and a second transmission part disposed at the rear end of the inner ring saw handle 33, with an elastic element 60 disposed between the transmission member 40 and the inner ring saw handle 33. In operation, when the inner ring saw assembly 30 moves backward under pressure, the first and second transmission parts engage, thereby transmitting the torque on the transmission member 40 to the inner ring saw handle 33, driving the inner blade tube 32 and the inner ring saw head 31 to rotate. When the hole is drilled through, the pressure on the inner ring saw assembly 30 disappears, and the first and second transmission parts separate under the elastic force of the elastic element 60. The inner ring saw assembly 30 disengages from the transmission member 40, and both the inner ring saw assembly 30 and the outer ring saw assembly 20 stop rotating simultaneously, achieving the function of stopping immediately upon drilling through.

[0043] In one embodiment, the first transmission part is at least one transmission groove 42 disposed on the front end face of the transmission member 40, and the second transmission part is at least one transmission pin 50 disposed on the rear end of the inner ring saw handle 33, the transmission pin 50 cooperating with the transmission groove 42. In the working state, the transmission pin 50 is inserted into the transmission groove 42 to achieve the function of transmitting torque. When drilling through the hole, the transmission pin 50 disengages from the transmission groove 42. As an example, there are two transmission grooves 42, arranged opposite each other on the diameter line of the transmission member 40; the inner ring saw handle 33 is provided with a radially extending through hole, and there is one transmission pin 50, which passes through the through hole, with both ends of the transmission pin 50 extending out of the through hole.

[0044] As an example, the transmission component 40 has a mounting hole 43 at its front end, the inner ring saw handle 33 has a mounting post 33a at its rear end, the elastic component 60 is a spring, the spring is installed in the mounting hole 43, and the front end of the spring is sleeved on the mounting post 33a.

[0045] In one embodiment, the inner ring saw assembly 30 is axially movable relative to the outer ring saw assembly 20 and includes a synchronous transmission mechanism disposed between the inner ring saw assembly 30 and the outer ring saw assembly 20, so that the outer ring saw assembly 20 rotates synchronously with the inner ring saw assembly 30. With this structure, when the inner saw teeth 31a pierce the bone tissue, the inner ring saw assembly 30 continues to move forward under the action of the elastic member 60, while the outer saw teeth 21a, located behind the inner saw teeth 31a, do not completely penetrate the bone tissue. During this process, the outer saw teeth 21a form a support with the bone tissue, limiting excessive forward movement of the entire electric ring saw during piercing, avoiding accidental injury to surrounding tissues or organs due to inertia, and further improving the safety of the surgery.

[0046] In one embodiment, the synchronous transmission mechanism includes an axially extending slot 23a disposed on the outer ring saw handle 23, and the end of the transmission pin 50 extends out of the transmission slot 42 and inserts into the slot 23a. Preferably, the front end of the transmission member 40 extends into the interior of the rear end of the outer ring saw handle 23. Thus, when the inner ring saw handle 33 rotates, the outer ring saw handle 23 rotates synchronously through the cooperation of the transmission pin 50 and the slot 23a. Simultaneously, the transmission pin 50 can slide back and forth along the slot 23a, thereby allowing the inner ring saw handle 33 to move axially relative to the outer ring saw handle 23.

[0047] As an alternative, the inner ring saw assembly 30 and the outer ring saw assembly 20 of the electric ring saw with the ring-through-stop function are fixedly connected, thereby eliminating the need for a synchronous transmission mechanism.

[0048] In one embodiment, the electric ring saw with a ring-stop function further includes a ring saw housing 10, which has a front end and a rear end. The rear end of the ring saw housing 10 is provided with a plug portion 12a, which mates with a socket on a drive handle (not shown). An outer ring saw handle 23 is rotatably mounted inside the ring saw housing 10. The outer ring saw handle 23 is rotatably mounted inside the outer housing body 11 via a plurality of first bearings 24 to reduce rotational resistance. As an example, the ring saw housing 10 in this embodiment includes an outer housing body 11 and an outer cover 12. The rear end of the outer housing body 11 is connected to the front end of the outer cover 12, and the outer cover 12 is provided with a plug portion 12a. The ring saw housing 10 adopts a split structure for easy assembly. It is a cylindrical shape extending axially for easy gripping.

[0049] In this embodiment, the transmission component 40 is rotatably mounted inside the housing body 11 via the second bearing 44, and the rear end of the transmission component 40 extends from the central hole of the outer cover 12. When the ring saw is mounted on the drive handle, the rear end of the transmission component 40 is connected to the output end of the drive device (not shown in the figure) inside the drive handle.

[0050] like Figure 2 , 5 As shown, in one embodiment, the electric ring saw further includes a depth limiting component 70 to achieve adjustable drilling depth. As an example, the depth limiting component 70 includes a depth limiting element 71, an adjusting sleeve 72, and a transmission mechanism. The depth limiting element 71 is a cylindrical structure disposed on the ring saw housing 10 and is capable of moving back and forth axially. The adjusting sleeve 72 is rotatably fitted onto the ring saw housing 10. The transmission mechanism is disposed between the depth limiting element 71 and the adjusting sleeve 72, for converting the rotational movement of the adjusting sleeve 72 into the axial movement of the depth limiting element 71.

[0051] In use, a tube (not shown in the figure) is fitted over the outer blade tube 22 and the outer ring saw head 21, with the rear end of the tube contacting the front end of the depth limiting member 71. When the front end of the tube contacts human skin, the ring saw cannot move forward due to the skin's restriction. By adjusting the position of the depth limiting member 71, the distance between the front end of the tube and the human skin can be adjusted, thereby achieving precise control of the cutting depth.

[0052] As an alternative, the depth limiting member 71 can also be directly set on the outer knife tube 22. In addition to being a cylindrical structure, the depth limiting member 71 can also be semi-circular or strip-shaped.

[0053] In one embodiment, the ring saw housing 10 includes a front section 111 and a rear section 112 connected front to back. The depth limiting member 71 is mounted on the front section 111, and the front end of the depth limiting member 71 extends out of the front section 111 and the adjusting sleeve 72, and is provided with a stop 71a. The stop 71a restricts the rearward movement of the depth limiting member 71, ensuring safe operation.

[0054] In one embodiment, the stop portion 71a protrudes inward relative to the rest of the depth limiting member 71, and the inner side of the stop portion 71a engages with the front end face of the depth limiting member 71 to limit the backward movement of the depth limiting member 71.

[0055] In one embodiment, the transmission mechanism includes a sliding member 73 disposed on the depth limiting member 71, and a helical groove 72a disposed on the adjusting sleeve 72 and cooperating with the sliding member 73, wherein the sliding member 73 is located within the helical groove 72a. Through the cooperation of the sliding member 73 and the helical groove 72a, the rotational motion of the adjusting sleeve 72 can be converted into the axial motion of the depth limiting member 71. Alternatively, the positions of the helical groove 72a and the sliding member 73 can be interchanged, i.e., the helical groove 72a is disposed on the depth limiting member 71, and the sliding member 73 is disposed on the adjusting sleeve 72.

[0056] In one embodiment, the ring saw housing 10 is provided with an elastically retractable impact member 74, and the inner wall of the adjusting sleeve 72 is provided with a plurality of recesses arranged at intervals along the circumferential direction to cooperate with the impact member 74; when the adjusting sleeve 72 rotates, the impact member 74 slides into or out of the recesses to generate an impact sound. Through the cooperation of the impact member 74 and the recesses, the user can obtain clear sound feedback during operation, ensuring the accuracy of adjustment.

[0057] In one embodiment, the outer surface of the ring saw housing 10 has a plurality of graduations spaced apart along the circumferential direction. The graduations provide an intuitive depth indication, allowing the user to precisely adjust the cutting depth.

[0058] In one embodiment, the outer diameter of the front section 111 is smaller than the outer diameter of the rear section 112. This design allows for more flexible installation of the depth limiting member 71 in the front section 111 and improves the overall structural stability.

[0059] In one embodiment, the system further includes a first limiting sleeve 75 and a second limiting sleeve 76, which are respectively mounted on the front section 111 on the front and rear sides of the adjusting sleeve 72. The first limiting sleeve 75 and the second limiting sleeve 76 are used to limit the range of movement of the adjusting sleeve 72 to ensure that the adjusting sleeve 72 rotates smoothly.

[0060] The embodiments described above are merely examples of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. An electric ring saw with a stop function upon ring pass, characterized in that, include: External ring saw assembly; An inner ring saw assembly is fitted inside the outer ring saw assembly, with its front end extending from the front end of the outer ring saw assembly. The outer ring saw assembly can rotate synchronously with the inner ring saw assembly. The transmission component is indirectly located at the rear end of the outer ring saw assembly and the inner ring saw assembly; A clutch mechanism is disposed between the rear end of the inner ring saw assembly and the transmission component. The clutch mechanism includes an elastic element, one end of which is connected to the rear end of the inner ring saw assembly, and the other end is connected to the transmission component. The inner ring saw assembly is connected to the transmission component by compressing the elastic element, and the transmission component drives the inner ring saw assembly to rotate. When the elastic element is released, the inner ring saw assembly disengages from the transmission component and stops rotating.

2. The electric ring saw with immediate stop function upon ring penetration according to claim 1, characterized in that, The outer ring saw assembly includes an outer ring saw handle, an outer blade tube, and an outer ring saw head. The rear end of the outer blade tube is connected to the outer ring saw handle, and the front end is connected to the rear end of the outer ring saw head. The front end of the outer ring saw head is provided with outer saw teeth. The inner ring saw assembly includes an inner ring saw handle, an inner blade tube, and an inner ring saw head. The inner ring saw handle is located inside the outer ring saw handle. The rear end of the inner blade tube is connected to the front end of the inner ring saw handle, and the front end is connected to the inner ring saw head. The front end of the inner ring saw head is provided with inner saw teeth.

3. The electric ring saw with a stop-on-ring function according to claim 2, characterized in that, The clutch mechanism includes: A first transmission part is disposed at the front end of the transmission component; The second transmission unit is located at the rear end of the inner ring saw handle; The elastic element is disposed between the first transmission part and the second transmission part.

4. The electric ring saw with a stop-on-ring function according to claim 3, characterized in that, The first transmission part is at least one radially extending transmission groove disposed on the front end face of the transmission member, and the second transmission part is at least one radially extending transmission pin disposed on the rear end of the inner ring saw handle; wherein, When the elastic element is compressed, the transmission pin engages in the transmission groove to connect the inner ring saw handle with the transmission element. When the elastic element is released, the drive pin disengages from the drive groove to separate the inner ring saw handle from the drive element.

5. The electric ring saw with a stop-on-ring function according to claim 4, characterized in that, There are two transmission grooves, which are arranged opposite each other on the diameter line of the transmission component; the inner ring saw handle is provided with a through hole extending radially, and there is one transmission pin, which passes through the through hole and has its two ends protruding from the through hole.

6. The electric ring saw with a ring-through-and-stop function according to claim 4, characterized in that, The transmission component has a mounting hole at its front end, the inner ring saw handle has a mounting post at its rear end, the elastic component is a spring, one end of the spring abuts against the mounting hole, and the other end is sleeved on the mounting post.

7. The electric ring saw with a stop-on-ring function according to claim 1, characterized in that, The inner ring saw assembly is axially movable relative to the outer ring saw assembly, and also includes a synchronous transmission mechanism disposed between the inner ring saw assembly and the outer ring saw assembly, so that the outer ring saw assembly rotates synchronously with the inner ring saw assembly.

8. The electric ring saw with a ring-through-and-stop function according to claim 7, characterized in that, The outer ring saw assembly includes an outer ring saw head and an outer ring saw handle, the inner ring saw assembly includes an inner ring saw head and an inner ring saw handle, the synchronous transmission mechanism includes at least one axially extending slot disposed on the outer ring saw handle, and a flat pin is disposed radially on the inner ring saw handle, with both ends of the flat pin extending into the slot.

9. The electric ring saw with a stop-on-ring function according to any one of claims 1-8, characterized in that, It also includes a ring saw housing, which has a front end and a rear end; wherein, the rear end of the outer ring saw assembly extends into the front end of the ring saw housing and is connected to the ring saw housing via a first bearing, and one end of the transmission member extends into the rear end of the ring saw housing and is connected to the ring saw housing via a second bearing.

10. The electric ring saw with a stop-on-ring function according to claim 9, characterized in that, The ring saw housing includes a main body and an outer cover. The rear end of the main body is connected to the front end of the outer cover. One end of the transmission component extends through the outer cover into the rear end of the main body and is connected to the main body. The outer cover is provided with a plug portion.

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