A new type of fishing drum with adjustable pitch

Abstract

The present invention relates to a novel pitch-adjustable fishing drum, comprising a drum body and a drum head arranged at one end of the drum body, wherein the drum head comprises, from inside to outside, an inner drum membrane, a first electrode layer, an electrorheological fluid layer, a second electrode layer, and an outer drum membrane, and a circle of main frame glue is arranged on the periphery of the opposite surfaces of the first electrode layer and the second electrode layer; a voltage controller is arranged on the side of the drum body, and the first electrode layer and the second electrode layer are electrically connected to the voltage controller; the novel pitch-adjustable fishing drum controls the electric field strength between the first electrode layer and the second electrode layer through the voltage controller, so that the viscosity of the electrorheological fluid layer changes accordingly, thereby obtaining a drum head with different tightness, so that the pitch of the fishing drum can be quickly adjusted, the adjustment method is simple and reliable, and the pitch of the fishing drum is also richer.

Description

Technical Field

[0001] The invention relates to the technical field of traditional musical instruments, in particular to a novel fishing drum with adjustable tone. Background Art

[0002] The fishing drum, which originated from the Tang Dynasty Daoqing, is a traditional musical instrument popular in Fujian, Hubei, Hunan, Shandong, Guangxi, Shaanxi, Jiangxi, Zhejiang and other regions, and is often used in folk art performances. The fishing drum is made of bamboo tubes, and the sizes of fishing drums vary from place to place. Some drums are about 25 to 40 cm long and 5 to 7 cm in diameter, while some are about 60 to 100 cm long and 13 to 14 cm in diameter. One end of the drum surface is covered with lard skin, sheepskin or frog skin. The existing fishing drum surface is fixed, and the tightness of the drum surface cannot be adjusted, so the tone of the fishing drum is single, and different sounds can only be produced by different striking methods and strengths of the artist, thus limiting the fishing drum from playing multi-tone repertoires and affecting the promotion and inheritance of the fishing drum. Summary of the invention

[0003] The present invention relates to a novel pitch-adjustable fishing drum. The novel pitch-adjustable fishing drum controls the electric field strength between a first electrode layer and a second electrode layer through a voltage controller, so that the viscosity of an electrorheological fluid layer changes accordingly, thereby obtaining a drum surface with different degrees of tightness, so that the pitch of the fishing drum can be adjusted quickly, the adjustment method is simple and reliable, and the pitch of the fishing drum is richer.

[0004] The technical solution of the present invention is as follows:

[0005] A novel pitch-adjustable fishing drum comprises a drum body and a drum head arranged at one end of the drum body, wherein the drum head comprises, from inside to outside, an inner drum membrane, a first electrode layer, an electrorheological fluid layer, a second electrode layer, and an outer drum membrane, and a circle of main frame glue is arranged on the periphery of the opposite surfaces of the first electrode layer and the second electrode layer; a voltage controller is arranged on the side of the drum body, and the first electrode layer and the second electrode layer are electrically connected to the voltage controller.

[0006] The diameter of the outer tympanic membrane is larger than the outer diameter of the drum body, the diameters of the inner tympanic membrane, the first electrode layer, the electrorheological fluid layer and the second electrode layer are equal to the outer diameter of the drum body, and the portion of the outer tympanic membrane that exceeds the end surface of the drum body is fixed to the side of the drum body.

[0007] A meshed secondary frame glue is arranged between the first electrode layer and the second electrode layer, and the electrorheological fluid layer is arranged in the mesh holes of the secondary frame glue; and the main frame glue and the secondary frame glue have the same height.

[0008] Wherein, the main frame glue and the auxiliary frame glue are thermosetting solid glue, the width of the main frame glue is 1-2 mm, and the width of the auxiliary frame glue is 0.5-1 mm.

[0009] Wherein, the voltage controller includes a power supply and a voltage control switch.

[0010] Wherein, the voltage-controlled switch includes a plurality of buttons, each of which is connected to a resistor with a different resistance value.

[0011] Wherein, a sound absorbing layer is embedded on the inner wall of the drum body away from the drum head, and the diameter of the sound absorbing layer is equal to the inner diameter of the drum body.

[0012] Among them, a tail tone adjustment mechanism can be selectively and detachably installed at the tail of the fishing drum; the tail tone adjustment mechanism includes a tuning cylinder detachably inserted at the open mouth of the tail of the fishing drum and a tuning cone arranged at the tail of the tuning cylinder; an elastic ring membrane is arranged on the inner circumferential surface of the tuning cylinder; the elastic ring membrane and the inner wall of the tuning cylinder are sealed to form a first air cavity; a first air valve is arranged on the wall of the tuning cylinder and connects the first air cavity with the outside; in the inflated state, a reduced diameter portion is formed in the middle inner drum of the elastic ring membrane; the tuning cone is fixedly connected to the tuning cylinder through a number of connecting columns; the tuning cone includes a T-shaped rigid body and an elastic cone membrane wrapped outside the T-shaped rigid body; the elastic cone membrane and the T-shaped rigid body are sealed to form a second air cavity; a second air valve is arranged on the bottom surface of the T-shaped rigid body and connects the second air cavity with the outside; the elastic cone membrane part is opposite to the gap of the elastic ring membrane.

[0013] Wherein, the tip of the tuning cone has a reflective blunt end.

[0014] Wherein, a hanging belt is externally connected to one side of the drum body.

[0015] The present invention has the following beneficial effects:

[0016] 1. Compared with the original fishing drum, the present invention controls the electric field strength between the first electrode layer and the second electrode layer through a voltage controller, so that the viscosity of the electrorheological fluid layer changes accordingly, thereby obtaining a drum surface with different degrees of tightness, so that the tone of the fishing drum can be quickly adjusted, and the adjustment method is simple and reliable.

[0017] 2. The secondary frame glue of the present invention divides the electrorheological fluid layer into multiple areas. When the drum head in a certain area is cracked, the secondary frame glue can maintain the overall tension of the drum head and prevent the crack from expanding. At the same time, the secondary frame glue can prevent the electrorheological fluid of the entire surface from flowing out from the damaged area, which can effectively increase the service life of the drum head.

[0018] 3. The main frame glue and the auxiliary frame glue of the present invention are thermosetting solid glue. When the electrorheological fluid is encapsulated between the first electrode layer and the second electrode layer, the main frame glue and the auxiliary frame glue can be further cured by heating to enhance their viscosity, which can effectively prevent the electrorheological fluid from flowing out of the sealing glue. The encapsulation method is simple and effective.

[0019] 4. The width of the main frame glue of the present invention is 1-2 mm, and the width of the auxiliary frame glue is 0.5-1 mm. The main frame glue and auxiliary frame glue of this width can not only provide sufficient adhesion, but also avoid the influence of glue curing shrinkage on the drum surface.

[0020] 5. The drum surface of the present invention is covered with an inner tympanic membrane and an outer tympanic membrane on the outside of the first electrode layer and the second electrode layer respectively. The inner tympanic membrane and the outer tympanic membrane are made of the same material as the tympanic membrane of a traditional fishing drum. Thus, when the drum surface is struck, the sound of the novel pitch-adjustable fishing drum will be closer to the sound of a traditional fishing drum due to the coverage of the double-layer tympanic membrane, thus avoiding a large change in pitch.

[0021] 6. A sound-absorbing layer is embedded on the inner wall of the drum body of the present invention, which is away from the drum head. When the drum head is struck, the material of the side close to the drum head is a traditional bamboo tube, and the sound can be reflected more and transmitted to the opening of the fishing drum. When the sound wave is transmitted to the position of the sound-absorbing layer, most of the sound wave is transmitted parallel to the axial direction of the drum body, but a small part will be emitted to the inner wall of the drum body, which will generate noise. The sound-absorbing layer can better absorb the noise, making the pronunciation of the fishing drum purer.

[0022] 7. The present invention can be optionally equipped with a tail sound adjustment mechanism. When the tail sound needs to be tuned or regulated or the fishing drum is to have more diverse timbre and sound effects, the tail sound adjustment device is inserted into the tail of the fishing drum, and the air pressure of the first air cavity and the second air cavity is adjusted by the first air valve and the second air valve, so as to adjust and control the degree of tension or contraction of the elastic ring membrane and the elastic cone membrane, and the relative gap between the elastic cone membrane and the elastic ring membrane; when the drumhead of the fishing drum is struck, the drumhead vibrates the air in the fishing drum, and the air in the fishing drum flows toward the tail under the impact of the drumhead, first passing through the reduced diameter part in the tuning cylinder, and the flow rate increases. When passing through the relative gap between the elastic cone membrane and the elastic ring membrane, the channel diameter is further reduced, and the flow rate is further increased. After flowing out to the outside, the volume suddenly increases, the flow rate decreases, and the pressure is released. In this process, the air pressure changes continuously, causing the elastic ring membrane and the elastic cone membrane to vibrate and sound accordingly; at the same time When the sound is played, the blunt head reflects a certain amount of air vibration waves, thereby increasing the interference of air vibration and achieving a better echo effect; since only part of the gap between the elastic ring membrane and the elastic cone membrane is relative, and the other parts are not relative, the air vibration first causes the elastic ring membrane to vibrate and make sound, then the relative part of the gap to vibrate and make sound, and then the elastic cone membrane to vibrate and make sound, thereby being able to produce different tones of continuous, rapid and sequential sound effects and the resonance sound effect of the relative part of the gap, producing diverse and distant tail sound effects; for different occasions, different needs, different user habits and preferences, it is only necessary to adjust the air pressure of the first air cavity and the second air cavity through the first air valve and the second air valve to achieve different tail sound effects simply, quickly and stably, and its variability is difficult to exhaust, thereby enabling the fishing drum to overcome the shortcomings of monotonous timbre and narrow range of variation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the present invention;

[0024] Figure 2 It is a partial cross-sectional view of the drum surface of the present invention;

[0025] Figure 3 It is a schematic diagram of another embodiment of the voltage controlled switch of the present invention;

[0026] Figure 4 It is a front cross-sectional view of the present invention;

[0027] Figure 5 is a schematic diagram of a second embodiment of the present invention;

[0028] Figure 6 is a schematic diagram of the tail tone adjustment mechanism of the present invention;

[0029] Figure 7 It is a schematic diagram of the present invention with a tail tone adjustment mechanism.

[0030] The reference numerals in the figure are as follows:

[0031] 1-drum body, 2-drum surface, 21-inner tympanic membrane, 22-first electrode layer, 23-electrorheological fluid layer, 24-second electrode layer, 25-outer tympanic membrane, 3-main frame glue, 4-voltage controller, 5-secondary frame glue, 6-voltage control switch, 7-sound absorbing layer, 8-hanging strap, 9-tuning tube, 10-tuning cone, 11-elastic ring membrane, 12-first air cavity, 13-first air valve, 14-T-shaped rigid body, 15-elastic cone membrane, 16-second air cavity, 17-second air valve, 18-reflective blunt head, 19-connecting column. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Embodiment 1:

[0034] See also Figures 1 to 2A novel pitch-adjustable fishing drum comprises a drum body 1 and a drum head 2 arranged at one end of the drum body 1, wherein the drum head 2 comprises an inner drum membrane 21, a first electrode layer 22, an electrorheological fluid layer 23, a second electrode layer 24, and an outer drum membrane 25 from the inside to the outside, wherein the inner drum membrane 21 and the outer drum membrane 25 are made of traditional fishing drum drum materials, such as pig skin, sheep skin or oil film, so that when the drum head 2 is struck, the sound produced will be closer to the sound of a traditional fishing drum because of the coverage of the double-layer drum membrane, thereby avoiding a large change in the pitch; a circle of main frame glue 3 is arranged on the periphery of the opposite surfaces of the first electrode layer 22 and the second electrode layer 24; The main frame glue 3 is a thermosetting solid glue, and the width of the main frame glue 3 is 1 to 2 mm. The main frame glue 3 of this width can provide sufficient adhesion to prevent the first electrode layer 22 and the second electrode layer 24 from separating. A voltage controller 4 is arranged on the side of the drum body 1, and the first electrode layer 22 and the second electrode layer 24 are electrically connected to the voltage controller 4. The electric field strength between the first electrode layer 22 and the second electrode layer 24 is controlled by the voltage controller 4, so that the viscosity of the electrorheological fluid layer 23 changes accordingly, thereby obtaining a drum head 2 with different degrees of tightness, so that the tone of the fishing drum can be quickly adjusted.

[0035] Furthermore, the diameter of the outer tympanic membrane 25 is larger than the outer diameter of the drum body 1, and the diameters of the inner tympanic membrane 21, the first electrode layer 22, the electrorheological fluid layer 23, and the second electrode layer 24 are equal to the outer diameter of the drum body 1; when installing the drum head 2, the inner tympanic membrane 21, the first electrode layer 22, the electrorheological fluid layer 23, and the second electrode layer 24 are fixed to the end surface of the drum body 1 in sequence, and then the inner tympanic membrane 21, the first electrode layer 22, the electrorheological fluid layer 23, and the second electrode layer 24 are wrapped with the outer tympanic membrane 25, so that each membrane layer is firmly fixed and tightly connected; the portion of the outer tympanic membrane 25 that exceeds the end surface of the drum body 1 is fixed to the side of the drum body 1.

[0036] Furthermore, the first electrode layer 22 and the second electrode layer 24 are flexible carbon fiber films or meshed carbon fibers or meshed metal wires, thereby ensuring the contact range with the electrorheological fluid without affecting the vibration effect of the inner eardrum 21 and the outer eardrum 25 .

[0037] Furthermore, the voltage controller 4 includes a power supply and a voltage control switch 6, and the voltage control switch 6 includes a plurality of buttons, each of which is connected to a resistor with a different resistance value and connected in parallel with each other. By pressing different buttons, resistors with different resistance values ​​will be connected between the power supply and the electrode layer, so that different electric field strengths are formed between the first electrode layer 22 and the second electrode layer 24 to control the electrorheological fluid layer 23 to reach different viscosities. When the electric field strength exceeds the critical electric field, the electrorheological fluid layer 23 can be changed from liquid to solid, so that the drum head 2 reaches the most tense state and the pitch emitted by the drum head 2 is also the highest.

[0038] Optional, see Figure 3The voltage control switch 6 can be a rotary adjustable resistance switch, so that the size of the resistance can be continuously adjusted, and the viscosity adjustment of the corresponding electrorheological fluid layer 23 is also more continuous, so that the tone emitted by the drum head 2 is also richer.

[0039] The power supply of the present application can be connected to an external power source by an external wire or provided with a rechargeable battery.

[0040] For further information, see Figure 4 A sound absorbing layer 7 is embedded on the inner wall of the drum body 1 away from the drum head 2, and the diameter of the sound absorbing layer 7 is equal to the inner diameter of the drum body 1; when the drum head 2 is struck, the material of the side close to the drum head 2 is a traditional bamboo tube, and the sound can be reflected more and transmitted to the opening of the fishing drum; when the sound wave is transmitted to the position of the sound absorbing layer 7, most of the sound wave is transmitted parallel to the axial direction of the drum body 1, but a small part will be emitted to the inner wall of the drum body 1, which will produce noise. The sound absorbing layer 7 can better absorb the noise, making the pronunciation of the fishing drum purer.

[0041] Furthermore, a hanging strap 8 is externally connected to one side of the drum body 1, and the artist can carry the fishing drum on his back to play by means of the hanging strap 8, which not only saves effort, but also allows the free hand to control the voltage controller 4, so that the fishing drum can emit the required tone in time.

[0042] Working principle of the present invention:

[0043] When playing the fishing drum, the artist first puts the strap 8 on his body, then uses one hand to strike the drum head 2, and uses the other hand to adjust the voltage controller 4 and strike the simple board; when debugging the pronunciation of the fishing drum, if the drum head 2 is found to be loose, the voltage controller 4 can be used to adjust the tightness of the drum head 2 to meet the pronunciation requirements of the fishing drum; in addition, during the performance, the artist can use the voltage controller 4 to adjust the viscosity of the electrorheological fluid layer to control the tightness of the drum head 2 to emit different tones, making the pronunciation of the fishing drum richer.

[0044] Embodiment 2:

[0045] The difference between the second embodiment and the first embodiment is that:

[0046] See also Figure 5A meshed secondary frame glue 5 is arranged between the first electrode layer 22 and the second electrode layer 24, and the electrorheological fluid layer 23 is arranged in the mesh of the secondary frame glue 5. The mesh can be circular or polygonal, and the figure only shows a hexagonal mesh; the secondary frame glue 5 divides the electrorheological fluid layer 23 into multiple areas. When the drum head 2 in a certain area is broken, the secondary frame glue 5 can maintain the overall tension of the drum head 2 to prevent the crack from expanding; at the same time, the secondary frame glue 5 can prevent the electrorheological fluid of the entire surface from flowing out from the damaged part, which can effectively improve the service life of the drum head 2; the main frame glue 3 and the secondary frame glue 5 have the same height to avoid the formation of a height difference that causes the electrorheological fluid in adjacent meshes to flow to each other; the secondary frame glue 5 is a thermosetting solid glue, and the width of the secondary frame glue 5 is 0.5-1mm. The secondary frame glue 5 of this width can not only provide sufficient adhesion, but also avoid the influence of glue curing shrinkage on the drum head 2.

[0047] For further information, see Figure 6 and 7 The tail of the fishing drum can be selectively and detachably installed with a tail tone adjustment mechanism; the tail tone adjustment mechanism includes a tuning cylinder 9 detachably inserted at the open mouth of the tail of the fishing drum and a tuning cone 10 arranged at the tail of the tuning cylinder 9; an elastic ring membrane 11 is arranged on the inner circumference of the tuning cylinder 9; the elastic ring membrane 11 and the inner wall of the tuning cylinder 9 are sealed to form a first air cavity 12; a first air valve 13 is arranged on the wall of the tuning cylinder 9 and connects the first air cavity 12 with the outside; in the inflated state, the The elastic ring membrane 11 has a reduced diameter portion formed in the middle thereof; the tuning cone 10 is fixedly connected to the tuning cylinder 9 via a plurality of connecting posts 19; the tuning cone 10 comprises a T-shaped rigid body 14 and an elastic cone membrane 15 wrapped around the T-shaped rigid body 14; the elastic cone membrane 15 and the T-shaped rigid body 14 are sealed to enclose a second air cavity 16; a second air valve 17 is arranged on the bottom surface of the T-shaped rigid body 14 and connects the second air cavity 16 with the outside; a portion of the elastic cone membrane 15 is opposite to the gap of the elastic ring membrane 11.

[0048] Furthermore, the tuning cone 10 has a reflective blunt tip 18 at its tip.

[0049] When it is necessary to tune or regulate the tail sound or to make the fishing drum have more diverse timbre and sound effects, the tail sound adjustment device is inserted into the tail of the fishing drum, and the air pressure of the first air cavity 12 and the second air cavity 16 is adjusted by the first air valve 13 and the second air valve 17, so as to adjust and control the tension or contraction degree of the elastic ring membrane 11 and the elastic cone membrane 15, and the relative gap between the elastic cone membrane 15 and the elastic ring membrane 11; when the drumhead of the fishing drum is struck, the drumhead vibrates the air in the fishing drum, and the air in the fishing drum flows toward the tail under the impact of the drumhead, first passes through the reduced diameter part in the tuning cylinder 9, and the flow rate increases. When passing through the relative gap between the elastic cone membrane 15 and the elastic ring membrane 11, the channel diameter is further reduced, the flow rate is further increased, and after flowing out to the outside, the volume suddenly increases, the flow rate decreases, and the pressure is released. In this process, the air pressure changes continuously, causing the elastic ring membrane 11 and the elastic cone membrane 15 to vibrate correspondingly. sound; at the same time, the reflective blunt head 18 reflects a certain amount of air vibration waves, thereby increasing the interference of air vibration and achieving a better echo effect; since only part of the gap between the elastic annular membrane 11 and the elastic conical membrane 15 is relative, and the other parts of each are not relative, the air vibration first causes the elastic annular membrane 11 to vibrate and make sound, then causes the relative part of the gap to vibrate and make sound, and then causes the elastic conical membrane 15 to vibrate and make sound, thereby being able to produce different tones of continuous, rapid and sequential sound effects and the resonance sound effect of the relative part of the gap, producing diverse and distant tail sound effects; for different occasions, different needs, different user habits and preferences, it is only necessary to adjust the air pressure of the first air cavity 12 and the second air cavity 16 through the first air valve 13 and the second air valve 17 to simply, quickly and stably achieve different tail sound effects, and its variability is difficult to exhaust.

[0050] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A novel pitch-adjustable fishing drum, comprising a drum body (1) and a drum head (2) arranged at one end of the drum body (1), characterized in that: The drum surface (2) comprises, from the inside to the outside, an inner drum membrane (21), a first electrode layer (22), an electrorheological fluid layer (23), a second electrode layer (24), and an outer drum membrane (25), and a circle of main frame glue (3) is arranged on the periphery of the opposite surfaces of the first electrode layer (22) and the second electrode layer (24); a voltage controller (4) is arranged on the side of the drum body (1), and the first electrode layer (22) and the second electrode layer (24) are electrically connected to the voltage controller (4).

2. A novel pitch-adjustable fishing drum as claimed in claim 1, characterized in that: The diameter of the outer tympanic membrane (25) is greater than the outer diameter of the drum body (1); the diameters of the inner tympanic membrane (21), the first electrode layer (22), the electrorheological fluid layer (23), and the second electrode layer (24) are equal to the outer diameter of the drum body (1); and the portion of the outer tympanic membrane (25) that protrudes beyond the end surface of the drum body (1) is fixed to the side surface of the drum body (1).

3. A novel pitch-adjustable fishing drum as claimed in claim 1, characterized in that: A mesh-shaped secondary frame glue (5) is arranged between the first electrode layer (22) and the second electrode layer (24); the electrorheological fluid layer (23) is arranged in the mesh holes of the secondary frame glue (5); and the main frame glue (3) and the secondary frame glue (5) have the same height.

4. A novel pitch-adjustable fishing drum as claimed in claim 3, characterized in that: The main frame glue (3) and the auxiliary frame glue (5) are thermosetting solid glues, the width of the main frame glue (3) is 1 to 2 mm, and the width of the auxiliary frame glue (5) is 0.5 to 1 mm.

5. The novel pitch-adjustable fishing drum as claimed in claim 1, characterized in that: The voltage controller (4) comprises a power supply and a voltage control switch (6).

6. A novel pitch-adjustable fishing drum as claimed in claim 5, characterized in that: The voltage control switch (6) comprises a plurality of buttons, each button being connected to a resistor with a different resistance value.

7. The novel pitch-adjustable fishing drum as claimed in claim 1, characterized in that: A sound absorbing layer (7) is embedded on the inner wall of the drum body (1) at a side away from the drum surface (2), and the diameter of the sound absorbing layer (7) is equal to the inner diameter of the drum body (1).

8. A novel pitch-adjustable fishing drum according to any one of claims 1 to 7, characterized in that: The tail of the fishing drum is detachably mounted with a tail tone adjustment mechanism; the tail tone adjustment mechanism comprises a tuning cylinder (9) detachably inserted at the open mouth of the tail of the fishing drum and a tuning cone (10) arranged at the tail of the tuning cylinder (9); an elastic ring membrane (11) is arranged on the inner circumferential surface of the tuning cylinder (9); the elastic ring membrane (11) and the inner wall of the tuning cylinder (9) are sealed to form a first air cavity (12); a first air valve (13) is arranged on the wall of the tuning cylinder (9) and connects the first air cavity (12) with the outside; in the inflated state, the elastic ring membrane (11) ) is formed with a reduced diameter portion at the middle inner drum; the tuning cone (10) is fixedly connected to the tuning cylinder (9) through a plurality of connecting columns (19); the tuning cone (10) comprises a T-shaped rigid body (14) and an elastic cone membrane (15) wrapped around the T-shaped rigid body (14); the elastic cone membrane (15) and the T-shaped rigid body (14) are sealed to form a second air cavity (16); a second air valve (17) is arranged on the bottom surface of the T-shaped rigid body (14) and connects the second air cavity (16) with the outside; the elastic cone membrane (15) is partially opposite to the gap of the elastic annular membrane (11).

9. A novel pitch-adjustable fishing drum as claimed in claim 8, characterized in that: The tip of the tuning cone (10) has a reflective blunt tip (18).

10. A novel pitch-adjustable fishing drum as claimed in claim 9, characterized in that: A hanging belt (8) is externally connected to one side of the drum body (1).

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