Knob type compression adjustment device for tambourine

Abstract

The application provides a knob type compression adjusting device of sand belt of a drum, relates to the technical field of musical instruments, and solves the technical problem that the distance between the sand belt and the lower drum surface cannot be adjusted. The device comprises a shell, a rotating assembly and a sliding assembly. The shell is fixed to the side of the drum. The sliding assembly is in sliding connection with the shell and is connected with the end of the sand belt. The rotating assembly comprises a knob. The sliding assembly comprises a contact part. The contact part is located in the shell. The knob extends into the shell and is rotatably arranged in the sliding assembly. Different positions of the side wall of the knob can be clamped with the contact part by rotating the knob. The sliding assembly is moved by different distances, and the distance between the sand belt and the lower drum surface is adjusted. The device is compact in structure and convenient to use. The distance between the sand belt and the lower drum surface of the drum musical instrument with the sand belt can be quickly adjusted, so that different tone effects are excited when the drum is played.

Description

Technical Field

[0001] The invention relates to the technical field of musical instruments, in particular to a knob-type compression adjustment device for a musical drum snare belt. Background Art

[0002] Medium- to large-scale drums are often fitted with a long, flat metal belt called a snare, also known as a snare string, attached to the lower drumhead. Made of several slender metal springs or thin, straight wires stretched side by side, the snare string is typically stretched across the entire lower drumhead and tightened at both ends. Snare strings are primarily used to enhance the drum's timbre. Without a snare string attached, striking the drum produces a high-pitched tom-tom sound. With a snare string attached, the original sound is enhanced by the sound of the vibrating wires striking the drumhead, thereby enhancing the drum's timbre.

[0003] In actual use and performance, it is found that the tension of the sand belt after being tightened, and the adjustment of the distance between the sand belt and the lower drum surface will cause a certain change in the timbre of the musical drum. If the performer can very easily and quickly adjust the distance between the sand belt and the lower drum surface in different performance atmospheres, it will produce a very obvious change in the sound effect, thereby being able to more fully and perfectly express the performer's desired artistic performance effect.

[0004] The applicant has found that the prior art has at least the following technical problems: the sand belt in the prior art is fixed to the position of the lower drumhead of the musical drum and is firmly tightened and compacted. The distance between the sand bag and the lower drumhead cannot be adjusted during the performance, which is inconvenient to use. Summary of the Invention

[0005] The present invention aims to provide a knob-type pressure adjustment device for a musical drum snare belt, addressing the existing technical problem of difficulty adjusting the distance between the snare belt and the lower drumhead. The various technical advantages achieved by the preferred solution among the various technical solutions provided by the present invention are detailed below.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] The present invention provides a knob-type compression adjustment device for a musical drum snare belt, comprising a housing, a rotating assembly, and a sliding assembly, wherein:

[0008] The shell is fixed to the side of the musical drum, and the sliding assembly is slidably connected to the shell and connected to the end of the snare belt;

[0009] The rotating assembly includes a toggle block, and the sliding assembly includes a resistance portion. The resistance portion is located in the shell. The toggle block extends into the shell and is rotatably arranged in the sliding assembly. By rotating the toggle block, different positions of the side wall of the toggle block can be engaged with the resistance portion, and drive the sliding assembly to move different distances, thereby adjusting the distance between the sand belt and the lower drum surface.

[0010] Preferably, two or more positioning grooves are provided on the side wall of the toggle block, and the positioning grooves are arranged at intervals;

[0011] The resistance portion includes a raised top block, the sliding assembly includes a sliding block, a matching groove is provided on the sliding block, the top block is located on the side wall of the matching groove, the toggle block extends into the matching groove, and the toggle block is rotated, so that different positioning grooves can be engaged with the top block, thereby driving the sliding block to move different distances along the axial direction of the musical drum.

[0012] Preferably, the rotating assembly includes a main shaft, which is rotatably connected to the housing and fixedly connected to the toggle block, and is eccentrically arranged relative to the toggle block.

[0013] Preferably, a sliding groove is provided on the sliding block, the sliding groove is connected with the matching groove, the matching groove is located on the side of the sliding block facing the side of the musical drum, the main shaft passes through the sliding groove and the matching groove, and the matching groove and the sliding groove both extend along the axial direction of the musical drum.

[0014] Preferably, the outer contour of the toggle block includes at least two connected curved segments, and the two curved segments are symmetrically arranged; the positioning groove includes a first positioning groove and a second positioning groove, wherein:

[0015] There are at least two first positioning grooves respectively located on the two curved segments, and the second positioning groove is located at the connection of the two curved segments.

[0016] Preferably, the central angles between the corresponding positions of the first positioning groove and the corresponding positions of the second positioning groove on the two curved segments are the same, and the radii from the corresponding positions of the first positioning groove to the center points on the curved segments are different.

[0017] Preferably, the rotating assembly includes a rotating plate, which is fixed to an end of the main shaft away from the toggle block and is located outside the housing for hand-held toggle.

[0018] Preferably, a sliding hole is provided on the sliding block, and a light bar is provided in the shell. The light bar is arranged along the axis of the musical drum, and the light bar passes through the sliding hole, so that the sliding block is slidably connected to the shell.

[0019] Preferably, a slot is provided on one side of the shell facing the lower drum surface, and the sliding block includes an extended support plate, the extended support plate extends out of the slot, and a hook is provided on the extended support plate;

[0020] The end of the sand belt is at 90 degrees to the part of the sand belt located on the lower drum surface, and is fixed with a buckle, and the buckle is fixedly connected to the hook.

[0021] Preferably, a return top hole is provided at the end of the sliding block facing away from the lower drum surface, a hollow tube is provided in the shell, a spring is fixed in the hollow tube, the hollow tube extends into the return top hole, and the spring is squeezed between the hollow tube and the return top hole and is always in a compressed state.

[0022] The knob-type compression adjustment device for a musical drum snare belt provided by the present invention has the following advantages compared to the prior art: during the performance of a musical drum, the toggle block is manually rotated, and different positions of the toggle block's side wall can engage with the abutment portion, driving the sliding assembly to move different distances, thereby adjusting the distance between the snare belt and the lower drum surface, thereby adjusting the timbre of the musical drum, and meeting the different adjustment requirements for the musical drum's timbre in different performance environments. The knob-type compression adjustment device for a musical drum snare belt has a compact structure and is easy to use. It can quickly adjust the distance between the snare belt and the lower drum surface of a drum instrument equipped with a snare belt, thereby stimulating different timbre effects during musical drum performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a schematic diagram of the overall structure of the knob-type compression adjustment device of the musical drum snare belt;

[0025] Figure 2 This is a partial cross-sectional view of the knob-type compression adjustment device of the snare belt;

[0026] Figure 3 It is a structural diagram of the shell;

[0027] Figure 4 It is a structural diagram of the rotating component;

[0028] Figure 5 It is a structural diagram of the sliding component from the first perspective;

[0029] Figure 6 This is a structural diagram of the sliding component from another perspective;

[0030] Figure 7 It is a structural diagram of the first state of the toggle block and the top block;

[0031] Figure 8 It is a structural diagram of another state of cooperation between the toggle block and the top block.

[0032] In the figure, 1. adjusting device; 2. shell; 21. upper through hole; 22. lower through hole; 23. light bar; 24. hollow tube; 25. mounting foot; 3. rotating assembly; 31. rotating plate; 32. main shaft; 33. toggle block; 34. positioning groove; 341. first positioning groove; 342. second positioning groove; 4. sliding block; 41. sliding groove; 42. extended support plate; 43. hook; 44. matching groove; 45. top block; 46. sliding hole; 47. return top hole; 48. extension column; 5. buckle; 6. musical drum. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center," "length," "width," "height," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," and "side" and the like, indicating positions or location relationships, are based on the positions or location relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0035] An embodiment of the present invention provides a knob-type tightening adjustment device for a musical drum snare belt, which can quickly adjust the fitting distance between the snare belt and the lower drum surface in a drum instrument with a snare belt, thereby stimulating different timbre effects when the musical drum is played.

[0036] The following combination Figures 1-8 The technical solution provided by the present invention is described in more detail.

[0037] like Figures 1-8As shown, this embodiment provides a knob-type tightening adjustment device 1 for a musical drum sand belt, comprising a shell 2, a rotating assembly 3 and a sliding assembly, wherein: the shell 2 is fixed to the side of the musical drum 6, the sliding assembly is slidably connected to the shell 2, and is connected to the end of the sand belt; the rotating assembly 3 includes a toggle block 33, the sliding assembly includes a resistance portion, the resistance portion is located in the shell 2, the toggle block 33 extends into the shell 2, and is rotatably arranged in the sliding assembly, and the toggle block 33 is rotated, and different positions of the side wall of the toggle block 33 can be engaged with the resistance portion, and drive the sliding assembly to move different distances, thereby adjusting the distance between the sand belt and the lower drum surface.

[0038] In the present embodiment, the knob-type compression adjustment device 1 for a musical drum snare belt is configured such that, during the performance of a musical drum 6, the toggle block 33 is manually rotated. Different positions of the side wall of the toggle block 33 engage with the abutment portion, driving the sliding assembly to move different distances, thereby adjusting the distance between the snare belt and the lower drumhead, thereby adjusting the timbre of the musical drum 6 and meeting the different timbre adjustment requirements of the musical drum 6 in different performance environments. The knob-type compression adjustment device 1 for a musical drum snare belt is compact and easy to use, and can quickly adjust the distance between the snare belt and the lower drumhead of a drum instrument equipped with a snare belt, thereby stimulating different timbre effects when the musical drum 6 is played.

[0039] In this embodiment, when the toggle block 33 is rotated, different positions of the side wall of the toggle block 33 can engage with the interference portion, and drive the sliding assembly to move different distances along the axis direction of the musical drum 6, thereby adjusting the distance between the sand belt and the lower drum surface.

[0040] As an optional embodiment, the sliding assembly includes a sliding block 4, a slot is provided on the side of the shell 2 facing the lower drum surface, the sliding block 4 includes an extended support plate 42, the extended support plate 42 extends out of the slot, and a hook 43 is provided on the extended support plate 42; the end of the sand belt is at 90° to the part of the sand belt located on the lower drum surface, and is fixed with a buckle 5, which is fixedly connected to the hook 43.

[0041] Since the end of the sand belt is at 90 degrees to the part of the sand belt located on the lower drum surface, and the buckle 5 on the end of the sand belt is fixedly connected to the hook 43, when the toggle block 33 is rotated, different positions of the side wall of the toggle block 33 can be engaged with the interference part, and drive the sliding assembly to move different distances along the axial direction of the musical drum 6, thereby adjusting the distance between the sand belt and the lower drum surface, which is convenient for adjustment.

[0042] As an alternative embodiment, see Figure 4 、 Figure 7 and Figure 8As shown, more than two positioning grooves 34 are provided on the side wall of the toggle block 33, and the positioning grooves 34 are arranged at intervals; the interference portion includes a raised top block 45, and the sliding assembly includes a sliding block 4, and the sliding block 4 is provided with a matching groove 44, and the top block 45 is provided on the inner side wall of the matching groove 44. The toggle block 33 extends into the matching groove 44, and the toggle block 33 is rotated. Different positioning grooves 34 can be engaged with the top block 45, thereby driving the sliding block 4 to move different distances along the axial direction of the musical drum 6.

[0043] Specifically, the above-mentioned toggle block 33 is a special-shaped block. When different positioning grooves 34 are engaged with the top block 45, the toggle block 33 drives the sliding block 4 to move different distances along the axial direction of the musical drum 6, thereby adjusting the distance between the sand belt and the lower drum surface.

[0044] As an alternative embodiment, see Figure 7 and Figure 8 As shown, the rotating assembly 3 includes a main shaft 32, which is fixedly connected to the toggle block 33 and is eccentrically arranged relative to the toggle block 33. Figure 2 and Figure 3 As shown, the housing 2 is provided with an upper through hole 21 and a lower through hole 22, and the main shaft 32 passes through the upper through hole 21 and is rotatably connected to the lower through hole 22. When the main shaft 32 is eccentrically arranged relative to the toggle block 33, the rotation of the main shaft 32 can realize the toggle block 33 to drive the sliding block 4 to move; otherwise, the toggle block 33 cannot drive the sliding block 4 to move.

[0045] As an alternative embodiment, see Figure 5 and Figure 6 As shown, the sliding block 4 is provided with a chute 41, which is connected to a mating slot 44. The mating slot 44 is located on the side of the sliding block 4 facing the side of the musical drum 6. The main shaft 32 passes through the chute 41 and the mating slot 44. The mating slot 44 and the chute 41 both extend along the axis of the musical drum 6. Due to the structure of the chute 41 and the mating slot 44, the main shaft 32 and the toggle block 33 do not affect the movement of the sliding block 4 along the axis, ensuring smooth movement of the sliding assembly.

[0046] As an alternative embodiment, see Figure 7 and Figure 8 As shown, the outer contour of the toggle block 33 includes at least two connected curved segments, and the two curved segments are symmetrically arranged; the positioning groove 34 includes a first positioning groove 341 and a second positioning groove 342, wherein: there are at least two first positioning grooves 341 respectively located on the two curved segments, and the second positioning groove 342 is located at the connection of the two curved segments.

[0047] See also Figure 7 and Figure 8As shown, in this embodiment, two first positioning grooves 341 are arranged on the two curved segments at intervals, and the second positioning groove 342 is located at the connection of the two curved segments. In this way, the operator can realize the movement of the sliding component along the axis of the musical drum 6 by rotating the toggle component to the right or the left, so as to facilitate the adjustment of the distance between the sand belt and the lower drum surface.

[0048] See also Figure 7 and Figure 8 When the toggle block 33 is rotated from the position where the second positioning groove 342 is engaged with the top block 45 to the position where the first positioning groove 34 is engaged with the top block 45, the sliding block 4 moves a certain distance, and the distance between the sand belt and the lower drum surface changes; when the toggle block 33 is rotated from the position where the first positioning groove 341 is engaged with the top block 45 to the position where the other first positioning groove 341 is engaged with the top block 45, the sliding block 4 also moves further, and the further distance between the sand belt and the lower drum surface changes.

[0049] The above structure realizes three-level adjustment of the distance between the sand belt and the lower drum surface. The sliding component drives the sand belt to fit and press the drum surface, slightly leave the drum surface, and completely leave the drum surface, so as to achieve the purpose of conveniently adjusting the tone of the musical drum 6.

[0050] As an alternative embodiment, see Figure 7 and Figure 8 As shown, the central angles between the corresponding positions of the first positioning groove 341 and the corresponding positions of the second positioning groove 342 on the two curved segments are the same, and the radii from the corresponding positions of the first positioning groove 341 on the curved segments to the center points are different.

[0051] The above structure has the following effect: when the toggle block 33 is rotated from the position where the second positioning groove 342 engages the top block 45 to the position where the first positioning groove 341 engages the top block 45, or when the toggle block 33 is rotated from the position where the first positioning groove 341 engages the top block 45 to another position where the first positioning groove 341 engages the top block 45, the rotation angle of the toggle block 33 is the same. However, due to the different radii from the corresponding positions of the first positioning groove 341 on the curved segment to the center point, the sliding block 4 moves different distances along the axis of the musical drum 6, that is, the distance between the snare belt and the lower drum head changes by different amounts. The user can rotate the toggle assembly counterclockwise or clockwise according to actual conditions and select the distance change between the snare belt and the lower drum head according to actual conditions, thereby adjusting the timbre of the musical drum 6, making the adjustment method more convenient and flexible.

[0052] The width of the matching groove 44 should meet the outer contour of the toggle block 33, so that the toggle block 33 does not contact the inner wall of the matching groove 44 when rotating, but can be engaged with the head. Figure 7 and Figure 8 shown.

[0053] As an alternative embodiment, see Figure 4 As shown, the rotating assembly 3 includes a rotating plate 31. The rotating plate 31 is fixed to the end of the main shaft 32 facing away from the toggle block 33 and is located outside the housing 2 for manual operation. This structure facilitates the operator to rotate the main shaft 32 and toggle block 33 by holding the rotating plate 31, thereby engaging the various positioning slots 34 with the top block 45.

[0054] As an alternative embodiment, see Figure 3 and Figure 5 As shown, the sliding block 4 is provided with a sliding hole 46, and the housing 2 is provided with a light bar 23. The light bar 23 is arranged along the axis of the musical drum 6 and passes through the sliding hole 46 to slide the sliding block 4 and the housing 2. When the toggle block 33 drives the sliding block 4 to move along the axis of the musical drum 6, the sliding block 4 is slidably connected to the housing 2 through the matching structure of the sliding hole 46 and the light bar 23, making the movement of the sliding block 4 smoother.

[0055] As an alternative embodiment, see Figure 5 The end of the sliding block 4 facing away from the lower drum surface is provided with a return hole 47. A hollow tube 24 is provided within the housing 2. A spring (not shown) is secured within the hollow tube 24. The hollow tube 24 extends into the return hole 47, and the spring is squeezed between the hollow tube 24 and the return hole 47, remaining in a compressed state. This spring tensions the housing 2 and the sliding block 4 without interfering with the movement of the sliding block 4 by the toggle block 33, ensuring a compact structure and preventing the housing 2 and the sliding block 4 from becoming loose.

[0056] As an alternative embodiment, see Figure 5 and 6 The sliding block 4 is provided with extension columns 48, which are located on both sides of the extended support plate 42. The sliding hole 46 extends from the extension columns 48 to the end of the sliding block 4. The extension columns 48 further increase the length of the sliding hole 46 to reduce the local rotational torque applied to the sliding block 4 when sliding on the optical bar 23, making the sliding movement of the sliding block 4 smoother.

[0057] As an alternative embodiment, see Figure 3 As shown, the shell 2 is provided with mounting feet 25, and the mounting feet 25 are provided with fixing holes for passing locking members to fix the shell 2 and the musical drum 6. The above-mentioned locking members can be screws. The shell 2 is fixed to the lower side of the musical drum 6 near the lower drum head via four mounting feet 25 with ordinary screws, which facilitates the installation and removal of the shell 2.

[0058] The lever-type adjustment device 1 of the sand belt of the musical drum 6 of this embodiment rotates the toggle assembly, and the positioning groove 34 on the toggle block 33 and the top block 45 on the sliding block 4 cooperate and engage with each other, which can drive the sliding block 4 to move along the axis of the musical drum 6. When different positioning grooves 34 and the top block 45 engage with each other, the sliding block 4 corresponds to different positions of the upper, middle and lower points respectively, which can make one end of the sand belt connected to it move along the axis of the musical drum 6 to fit and press the drum surface, slightly leave the drum surface, and completely leave the drum surface, thereby achieving the purpose of conveniently adjusting the timbre of the musical drum 6.

[0059] For details, see Figure 1 and Figure 7 、 Figure 8 As shown, when the rotating piece 31 of the rotating assembly 3 is rotated to the downward position, the sand belt is driven to the farthest position from the lower drum surface of the musical drum 6; when the rotating piece 31 is rotated to the middle locking position, the sand belt is driven to a distance of about 1-2 mm from the lower drum surface; when the rotating piece 31 is rotated to the upward locking position, the sand belt is driven to be close to the lower drum surface.

[0060] For assembly purposes, the toggle assembly can be separated into two parts above the toggle block 33 , which can be inserted into the housing 2 and the sliding block 4 respectively during assembly.

[0061] In the description of this specification, specific features, structures or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0062] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A knob-type tightening adjustment device for a musical drum snare belt, characterized in that: It includes a housing, a rotating assembly, and a sliding assembly, wherein: The shell is fixed to the side of the musical drum, and the sliding assembly is slidably connected to the shell and connected to the end of the snare belt; The rotating assembly includes a toggle block, and the sliding assembly includes a resistance portion, the resistance portion is located in the shell, the toggle block extends into the shell, and is rotatably arranged in the sliding assembly. By rotating the toggle block, different positions of the side wall of the toggle block can be engaged with the resistance portion, and the sliding assembly is driven to move different distances, thereby adjusting the distance between the sand belt and the lower drum surface; Two or more positioning grooves are provided on the side wall of the toggle block, and the positioning grooves are arranged at intervals; The resistance portion includes a raised top block, the sliding assembly includes a sliding block, a matching groove is provided on the sliding block, the top block is located on the side wall of the matching groove, the toggle block extends into the matching groove, and the toggle block is rotated, so that different positioning grooves can be engaged with the top block, thereby driving the sliding block to move different distances along the axial direction of the musical drum.

2. The knob-type tightening adjustment device for a musical drum snare belt according to claim 1, characterized in that: The rotating assembly includes a main shaft, which is rotatably connected to the housing and fixedly connected to the toggle block, and is eccentrically arranged relative to the toggle block.

3. The knob-type tightening adjustment device for a musical drum snare belt according to claim 2, characterized in that: The sliding block is provided with a sliding groove, which is connected to the matching groove. The matching groove is located on the side of the sliding block facing the side of the musical drum. The main shaft passes through the sliding groove and the matching groove. The matching groove and the sliding groove both extend along the axial direction of the musical drum.

4. The knob-type compression adjustment device for a musical drum snare belt according to claim 1, characterized in that: The outer contour of the toggle block includes at least two connected curved segments, and the two curved segments are symmetrically arranged; the positioning groove includes a first positioning groove and a second positioning groove, wherein: There are at least two first positioning grooves respectively located on the two curved segments, and the second positioning groove is located at the connection of the two curved segments.

5. The knob-type tightening adjustment device for a musical drum snare belt according to claim 4, characterized in that: The central angles between the corresponding positions of the first positioning groove and the corresponding positions of the second positioning groove on the two curved segments are the same, and the radii from the corresponding positions of the first positioning groove to the center points on the curved segments are different.

6. The knob-type tightening adjustment device for a musical drum snare belt according to claim 2, characterized in that: The rotating assembly includes a rotating plate, which is fixed to one end of the main shaft away from the dial block and is located outside the shell for being manually dialed.

7. The knob-type tightening adjustment device for a musical drum snare belt according to claim 1, characterized in that: The sliding block is provided with a sliding hole, and a light bar is provided in the shell. The light bar is arranged along the axis of the musical drum and passes through the sliding hole, so that the sliding block is slidably connected to the shell.

8. The knob-type tightening adjustment device for a musical drum snare belt according to claim 1, characterized in that: A slot is provided on one side of the shell facing the lower drum surface, and the sliding block includes an extended support plate, the extended support plate extends out of the slot, and a hook is provided on the extended support plate; The end of the sand belt is at 90 degrees to the part of the sand belt located on the lower drum surface, and is fixed with a buckle, and the buckle is fixedly connected to the hook.

9. The knob-type tightening adjustment device for a musical drum snare belt according to claim 1, characterized in that: A return top hole is provided at the end of the sliding block facing away from the lower drum surface, a hollow tube is provided in the shell, a spring is fixed in the hollow tube, the hollow tube extends into the return top hole, and the spring is squeezed between the hollow tube and the return top hole and is always in a compressed state.

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