Centrifugal wind wheel outer rotor series drive device

Abstract

The invention discloses a centrifugal wind wheel outer rotor series drive device, and relates to the technical field of centrifugal wind wheel series drive, the centrifugal wind wheel outer rotor series drive device comprises a base, the top end of the base is fixedly provided with a first centrifugal fan shell, and a sealing mechanism is arranged between the base and a second centrifugal fan shell; a driving mechanism is arranged between the first centrifugal fan shell and the servo motor; a fixing seat is fixedly mounted at the top end of the base, and a cleaning mechanism is arranged between the first centrifugal fan shell and the fixing seat. According to the centrifugal wind wheel outer rotor series connection driving device, the driving rod drives the controller to drive the inner impeller set to rotate, the inner impeller set drives the filtering disc to rotate, air flow is pre-compressed through the inner impeller set, the air flow entering the first outer impeller set is more uniform, and then the air compression effect of the first outer impeller set is improved; and the air is conveyed through the first exhaust outlet, the shell of the first centrifugal fan is of a circular structure, the air circulation area is increased, and the circulation amount is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of series drive of centrifugal impellers, and specifically to an external rotor series drive device for centrifugal impellers. Background Art

[0002] The centrifugal impeller is the core component in a centrifugal fan. It sucks in gas and accelerates it to a high speed. Subsequently, this gas is pushed into the outlet of the fan, enabling the gas to obtain a large amount of kinetic energy, and then driving the gas to flow out of the outlet of the fan, thereby improving the usage efficiency.

[0003] However, in the existing centrifugal impellers during use, the flow rate and pressure at the outer edge of the blade group are inconsistent, internal circulation occurs in the volute, the vorticity increases, the efficiency decreases, and it is not conducive to controlling vibration and noise.

[0004] To solve the above defects, in the prior art, a Chinese patent with the publication number CN221322825U discloses a series low-noise centrifugal fan impeller, including an outer impeller group, an inner impeller group coaxial with the outer impeller group, a sound-absorbing part arranged between the outer impeller group and the inner impeller group, fixing screws, a fixing mesh plate arranged on the sound-absorbing part and fixed by the fixing screws, noise-reducing blades forming the inner impeller group and the outer impeller group, and a connecting ring arranged at the top of the outer impeller group; wherein, the bottom of the sound-absorbing part is connected to the bottom connecting disc, the fixing mesh plate is arranged at the top, the fixing mesh plate is fixed by fixing screws, the size of the fixing mesh plate is adapted to the gap between the inner and outer impeller groups. Through the combined application of the fixing mesh plate and the fixing screws, a stable and firm support structure is provided for the sound-absorbing part. The sound-absorbing part is filled with sound-absorbing materials to absorb the noise inside the volute and achieve the effect of noise reduction.

[0005] Moreover, in the prior art, a Chinese patent with the publication number CN214945187U discloses a series high-pressure centrifugal fan, including a frame body, on which a motor, a first centrifugal ventilator, and a second centrifugal ventilator are arranged. The first centrifugal ventilator includes a first impeller, the second centrifugal ventilator includes a second impeller, and the first impeller and the second impeller are coaxially arranged. By setting the first centrifugal ventilator and the second centrifugal ventilator, and a connecting pipe is arranged between the first air outlet and the second air inlet. Fixed pipes are fixedly connected to both the first air outlet and the second air outlet, and the fixed pipes change the shapes of the first air outlet and the second air outlet from square to circular. By using one motor to drive the operation of the first impeller and the second impeller, it can be used to replace a centrifugal blower with a two-stage impeller, which can not only meet the performance parameters that a centrifugal blower can achieve, but also greatly reduce the processing difficulty and manufacturing cost.

[0006] During the use of the above device, the sound-absorbing part is filled with sound-absorbing materials to achieve the effect of noise reduction. However, in the above device, the long-term operation of the fan causes external dust to enter the inside of the fan, and the dust causes the equipment to be corroded, thereby affecting the operation of the equipment. Therefore, in the actual use process, the accumulation of dust affects the operation of the equipment. Summary of the Invention

[0007] The purpose of the present invention is to provide a series-drive device for an outer rotor of a centrifugal impeller to solve the problem that the accumulation of dust affects the operation of the equipment proposed in the above background technology.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A series-drive device for an outer rotor of a centrifugal impeller, including a base, a first centrifugal fan housing is fixedly installed at the top of the base, a second centrifugal fan housing is fixedly installed at the top of the base, a sealing disc is fixedly installed on the outer surface of the second centrifugal fan housing, a transmission pipe is fixedly installed on the inner side surface of the sealing disc, and a sealing mechanism for preventing leakage is provided between the base and the second centrifugal fan housing; a servo motor is fixedly installed at the top of the base, an output shaft is rotatably installed at the output end of the servo motor, a positioning frame is fixedly installed on the outer surface of the first centrifugal fan housing, and a driving mechanism for series operation is provided between the first centrifugal fan housing and the servo motor; a fixing seat is fixedly installed at the top of the base, an air inlet box is fixedly installed on the outer surface of the first centrifugal fan housing, and a cleaning mechanism is provided between the first centrifugal fan housing and the fixing seat.

[0009] Further, a coupling is fixedly installed on the outer surface of the output shaft, a driving rod is fixedly installed on the inner side surface of the coupling, the driving rod is movably installed on the inner side surface of the positioning frame, and the coupling and the driving rod form a rotating structure.

[0010] Further, the cleaning mechanism includes a positioning disc, the positioning disc is fixedly installed on the outer surface of the driving rod, a rotating rod is fixedly installed on the outer surface of the driving rod, the rotating rod is fixedly installed on the outer surface of the positioning disc, and the driving rod and the rotating rod form a rotating structure.

[0011] Further, a buffer spring is fixedly installed on the inner side surface of the rotating rod, a limiting rod is fixedly installed on the outer surface of the buffer spring, the limiting rod is movably installed on the inner side surface of the rotating rod, and the buffer spring and the limiting rod form a telescopic structure.

[0012] Further, a cleaning brush is fixedly installed on the outer surface of the limiting rod, the cleaning brush is movably abutted against the inner side surface of the first centrifugal fan housing, and a filter disc is movably abutted against the inner side surface of the first centrifugal fan housing.

[0013] Further, the driving mechanism includes a buffer pad fixedly installed on the outer surface of the driving rod. A controller is fixedly installed on the outer surface of the driving rod, and an inner impeller group is fixedly installed on the outer surface of the controller.

[0014] Further, a filter disc is fixedly installed on the outer surface of the inner impeller group. An outer impeller group one is fixedly installed on the outer surface of the filter disc, and the filter disc and the outer impeller group one form an integral structure.

[0015] Further, the sealing mechanism includes a first air outlet fixedly installed on the outer surface of the first centrifugal fan housing. A connecting pipe is fixedly installed on the outer surface of the first air outlet, and a transmission pipe is fixedly installed on the outer surface of the connecting pipe.

[0016] Further, a second air outlet is fixedly installed at the top of the second centrifugal fan housing. The second air outlet is circular in structure, and a driving rod is movably installed on the inner side surface of the second centrifugal fan housing.

[0017] Further, an outer impeller group two is fixedly installed on the outer surface of the driving rod. The driving rod is movably installed on the inner side surface of the bearing seat, and the bearing seat is fixedly installed at the top of the fixed seat.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The driving rod drives the controller to rotate, the controller drives the inner impeller group to rotate, the inner impeller group drives the filter disc to rotate. By pre-compressing the air flow through the inner impeller group, the air flow entering the outer impeller group one can be made more uniform, thereby improving the air compression effect of the outer impeller group one to increase the air volume of the fan. The filter disc drives the outer impeller group one to rotate, facilitating the transmission of gas through the air inlet box, and the gas is transmitted through the first air outlet. Since the first centrifugal fan housing is circular in structure, the gas circulation area is increased and the circulation volume is improved;

[0020] (2) The connecting pipe is fixedly connected to the first air outlet, and the gas is transmitted to the transmission pipe through the first air outlet. A sealing disc is installed at the connection between the transmission pipe and the second centrifugal fan housing to increase the overall sealing performance, prevent gas leakage, and increase the transmission efficiency. The driving rod is rotationally connected to the output shaft of the servo motor through the bearing seat to increase the transmission stability. The driving rod drives the outer impeller group two inside the second centrifugal fan housing to rotate, and the number of impellers of the outer impeller group two is the same as that of the outer impeller group one. The connecting pipe and the transmission pipe are bent, effectively increasing the resistance inside the pipeline and improving the pressurization effect during transmission;

[0021] (3) The second outer impeller group and the first outer impeller group rotate coaxially through the drive rod, which is convenient for improving the intake efficiency, ensuring that the flow rate and pressure at the outer edge of the blade group are consistent, and reducing the noise generated inside.

[0022] (4) By starting the servo motor, the servo motor drives the output shaft to rotate. The output shaft and the drive rod are connected by a coupling. The drive rod drives the inner impeller group to rotate. The inner impeller group drives the filter disc and the first outer impeller group to rotate. When the inner impeller group rotates, a large low-pressure area is formed in the center area of the impeller, thereby reducing the eddy current intensity at the impeller inlet, increasing the gas flow velocity, and further reducing the power consumption of the fan.

[0023] (5) The gas is conducted into the interior of the first centrifugal fan housing through the air inlet opened in the air inlet box, and the filter disc is used to filter the incoming gas to improve the gas quality. The drive rod drives the rotating rod to rotate, and the rotating rod drives the limiting rod carrying the cleaning brush to move. The cleaning brush is used to clean the dust inside the first centrifugal fan housing, preventing dust from accumulating inside the first centrifugal fan housing and affecting the operation of the equipment, and increasing the safety of the equipment.

[0024] (6) The cleaning brush presses the limiting rod, and the limiting rod drives the buffer spring to stretch and contract. The groove opened inside the rotating rod limits the limiting rod, relieving the frictional force generated by the cleaning brush and increasing the service life of the cleaning brush. The rotating rod is limited by the positioning disc, and the drive rod is positioned by the positioning frame, preventing the drive rod from shifting and falling off, and improving the overall stability. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 It is a three-dimensional structure schematic diagram of the first air outlet of the present invention;

[0027] Figure 3 It is a three-dimensional structure schematic diagram of the first outer impeller group of the present invention;

[0028] Figure 4 It is a sectional structure schematic diagram of the air inlet box of the present invention;

[0029] Figure 5 It is a three-dimensional structure schematic diagram of the cleaning brush of the present invention;

[0030] Figure 6 It is a three-dimensional structure schematic diagram of the inner impeller group of the present invention;

[0031] Figure 7 It is a three-dimensional structure schematic diagram of the second air outlet of the present invention;

[0032] Figure 8 It is a three-dimensional structure schematic diagram of the positioning frame of the present invention;

[0033] Figure 9 This is a three-dimensional structural schematic diagram of the second outer impeller group of the present invention;

[0034] Figure 10 This is a three-dimensional structural schematic diagram of the rotating rod of the present invention.

[0035] In the figure: 1, base; 2, first centrifugal fan housing; 3, second centrifugal fan housing; 4, servo motor; 5, output shaft; 6, coupling; 7, drive rod; 8, positioning frame; 9, positioning disk; 10, rotating rod; 11, buffer spring; 12, limiting rod; 13, cleaning brush; 14, buffer pad; 15, controller; 16, inner impeller group; 17, filter disk; 18, first outer impeller group; 19, air inlet box; 20, first air outlet; 21, connecting pipe; 22, transmission pipe; 23, second air outlet; 24, fixed seat; 25, bearing seat; 26, second outer impeller group; 27, sealing disk. Specific embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment 1: Please refer to Figure 1 - Figure 10 , the present invention provides the following technical solutions: A centrifugal wind wheel outer rotor series drive device includes a base 1, a first centrifugal fan housing 2 is fixedly installed at the top of the base 1, a second centrifugal fan housing 3 is fixedly installed at the top of the base 1, a sealing disk 27 is fixedly installed on the outer surface of the second centrifugal fan housing 3, a transmission pipe 22 is fixedly installed on the inner side surface of the sealing disk 27, and a sealing mechanism for preventing leakage is provided between the base 1 and the second centrifugal fan housing 3; a servo motor 4 is fixedly installed at the top of the base 1, an output shaft 5 is rotatably installed at the output end of the servo motor 4, a positioning frame 8 is fixedly installed on the outer surface of the first centrifugal fan housing 2, and a drive mechanism for series operation is provided between the first centrifugal fan housing 2 and the servo motor 4; a fixed seat 24 is fixedly installed at the top of the base 1, an air inlet box 19 is fixedly installed on the outer surface of the first centrifugal fan housing 2, and a cleaning mechanism is provided between the first centrifugal fan housing 2 and the fixed seat 24.

[0038] The sealing mechanism for preventing leakage, which is arranged between the base 1 and the second centrifugal fan housing 3, enhances the sealing performance of the equipment, ensuring stable transmission of the equipment. Moreover, the driving mechanism arranged in series between the first centrifugal fan housing 2 and the servo motor 4 drives the equipment to operate, thereby increasing the wind pressure. Additionally, the cleaning mechanism arranged between the first centrifugal fan housing 2 and the fixed seat 24 facilitates the internal cleaning, preventing dust from accumulating inside the first centrifugal fan housing 2 and improving the efficiency of the equipment.

[0039] Embodiment 2: On the basis of Embodiment 1, please refer to Figure 1 - Figure 10 , a positioning frame 8 is further disclosed, and its specific structure is as follows: A coupling 6 is fixedly installed on the outer surface of the output shaft 5, a driving rod 7 is fixedly installed on the inner side surface of the coupling 6, the driving rod 7 is movably installed on the inner side surface of the positioning frame 8, and the coupling 6 and the driving rod 7 form a rotating structure. The cleaning mechanism includes a positioning disk 9, the positioning disk 9 is fixedly installed on the outer surface of the driving rod 7, a rotating rod 10 is fixedly installed on the outer surface of the driving rod 7, the rotating rod 10 is fixedly installed on the outer surface of the positioning disk 9, and the driving rod 7 and the rotating rod 10 form a rotating structure. A buffer spring 11 is fixedly installed on the inner side surface of the rotating rod 10, a limiting rod 12 is fixedly installed on the outer surface of the buffer spring 11, the limiting rod 12 is movably installed on the inner side surface of the rotating rod 10, and the buffer spring 11 and the limiting rod 12 form a telescopic structure. A cleaning brush 13 is fixedly installed on the outer surface of the limiting rod 12, the cleaning brush 13 is movably abutted against the inner side surface of the first centrifugal fan housing 2, and a filter disk 17 is movably abutted against the inner side surface of the first centrifugal fan housing 2.

[0040] By starting the servo motor 4, the servo motor 4 operates to drive the output shaft 5 to rotate. The output shaft 5 and the driving rod 7 are connected by a coupling 6. The driving rod 7 drives the inner impeller group 16 to rotate. The inner impeller group 16 drives the filter disc 17 and the outer impeller group 18 to rotate. When the inner impeller group 16 rotates, a large low-pressure area is formed in the center area of the impeller, thereby reducing the eddy current intensity at the impeller inlet, increasing the gas flow velocity, and further reducing the power consumption of the fan. The gas is conducted into the first centrifugal fan housing 2 through the air inlet opened in the air inlet box 19, and the filter disc 17 is used to filter the incoming gas to improve the gas quality. Moreover, the driving rod 7 drives the rotating rod 10 to rotate, and the rotating rod 10 drives the limiting rod 12 carrying the cleaning brush 13 to move. The cleaning brush 13 is used to clean the dust inside the first centrifugal fan housing 2, preventing dust from accumulating inside the first centrifugal fan housing 2 and affecting the equipment operation, increasing the safety of the equipment. Also, when the cleaning brush 13 presses the limiting rod 12, the limiting rod 12 drives the buffer spring 11 to expand and contract, and the groove opened inside the rotating rod 10 limits the limiting rod 12, alleviating the friction force generated by the cleaning brush 13 and increasing the service life of the cleaning brush 13. In addition, the rotating rod 10 is limited by the positioning disc 9, and the driving rod 7 is positioned by the positioning frame 8, preventing the driving rod 7 from shifting and falling off, and improving the overall stability.

[0041] Embodiment 3: On the basis of Embodiment 1, please refer to Figure 2 - Figure 10 , a connecting pipe 21 is also disclosed, and its specific structure is as follows: The driving mechanism includes a buffer pad 14, which is fixedly installed on the outer surface of the driving rod 7. A controller 15 is fixedly installed on the outer surface of the driving rod 7. An inner impeller group 16 is fixedly installed on the outer surface of the controller 15. A filter disc 17 is fixedly installed on the outer surface of the inner impeller group 16. An outer impeller group 1 is fixedly installed on the outer surface of the filter disc 17, and the filter disc 17 and the outer impeller group 18 form an integral structure. The sealing mechanism includes a first air outlet 20, which is fixedly installed on the outer surface of the first centrifugal fan housing 2. A connecting pipe 21 is fixedly installed on the outer surface of the first air outlet 20, and a transmission pipe 22 is fixedly installed on the outer surface of the connecting pipe 21. A second air outlet 23 is fixedly installed at the top of the second centrifugal fan housing 3. The second air outlet 23 is circular in structure, and the driving rod 7 is movably installed on the inner side surface of the second centrifugal fan housing 3. An outer impeller group 26 is fixedly installed on the outer surface of the driving rod 7. The driving rod 7 is movably installed on the inner side surface of the bearing seat 25, and the bearing seat 25 is fixedly installed at the top of the fixed seat 24.

[0042] The driving rod 7 drives the controller 15 to rotate. The controller 15 drives the inner impeller group 16 to rotate. The inner impeller group 16 drives the filter disc 17 to rotate. By pre-compressing the air flow in the inner impeller group 16, the air flow entering the first outer impeller group 18 can be made more uniform, thereby improving the air compression effect of the first outer impeller group 18 to increase the air volume of the fan. The filter disc 17 drives the first outer impeller group 18 to rotate, facilitating the transmission of gas through the air inlet box 19, and the gas is transmitted through the first air outlet 20. The first centrifugal fan housing 2 has a circular structure, increasing the gas flow area and improving the flow rate. The connecting pipe 21 is fixedly connected to the first air outlet 20. The gas is transmitted from the first air outlet 20 to the transmission pipe 22. A sealing disc 27 is installed at the connection between the transmission pipe 22 and the second centrifugal fan housing 3, increasing the overall sealing performance, preventing gas leakage, and increasing the transmission efficiency. The driving rod 7 is rotationally connected to the output shaft 5 of the servo motor 4 through a bearing seat 25, increasing the stability of the transmission. The driving rod 7 drives the second outer impeller group 26 inside the second centrifugal fan housing 3 to rotate. The number of impellers of the second outer impeller group 26 is the same as that of the first outer impeller group 18. The connecting pipe 21 and the transmission pipe 22 are bent, effectively increasing the resistance inside the pipeline and improving the pressure boosting effect during transmission. The second outer impeller group 26 and the first outer impeller group 18 rotate coaxially through the driving rod 7, facilitating the improvement of the air intake efficiency, ensuring that the flow rate and pressure at the outer edge of the blade group are consistent, and reducing the noise generated inside.

[0043] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A centrifugal fan outer rotor series drive device, comprising a base (1), a first centrifugal fan housing (2) being fixedly mounted on the top of the base (1), characterized in that: A second centrifugal fan casing (3) is fixedly mounted on the top of the base (1), a sealing disk (27) is fixedly mounted on the outer surface of the second centrifugal fan casing (3), a transmission pipe (22) is fixedly mounted on the inner side of the sealing disk (27), and a sealing mechanism for preventing leakage is provided between the base (1) and the second centrifugal fan casing (3); A servo motor (4) is fixedly mounted on the top of the base (1), an output shaft (5) is rotatably mounted on the output end of the servo motor (4), a positioning frame (8) is fixedly mounted on the outer surface of the first centrifugal fan housing (2), and a driving mechanism operating in series is provided between the first centrifugal fan housing (2) and the servo motor (4); A fixing seat (24) is fixedly mounted on the top of the base (1), an air inlet box (19) is fixedly mounted on the outer surface of the first centrifugal fan housing (2), and a cleaning mechanism is provided between the first centrifugal fan housing (2) and the fixing seat (24).

2. A centrifugal wind wheel outer rotor series drive device according to claim 1, characterized in that: A coupling (6) is fixedly mounted on the outer surface of the output shaft (5), a driving rod (7) is fixedly mounted on the inner side surface of the coupling (6), the driving rod (7) is movably mounted on the inner side surface of the positioning frame (8), and the coupling (6) and the driving rod (7) form a rotating structure.

3. The centrifugal wind wheel outer rotor series drive device according to claim 1, characterized in that: The cleaning mechanism comprises a positioning plate (9), wherein the positioning plate (9) is fixedly mounted on the outer surface of a driving rod (7), a rotating rod (10) is fixedly mounted on the outer surface of the driving rod (7), and the rotating rod (10) is fixedly mounted on the outer surface of the positioning plate (9), and the driving rod (7) and the rotating rod (10) form a rotating structure.

4. A centrifugal wind wheel outer rotor series drive device according to claim 3, characterized in that: A buffer spring (11) is fixedly mounted on the inner side surface of the rotating rod (10), a limiting rod (12) is fixedly mounted on the outer surface of the buffer spring (11), the limiting rod (12) is movably mounted on the inner side surface of the rotating rod (10), and the buffer spring (11) and the limiting rod (12) form a telescopic structure.

5. A centrifugal wind wheel outer rotor series drive device according to claim 4, characterized in that: A cleaning brush (13) is fixedly mounted on the outer surface of the limiting rod (12), and the cleaning brush (13) movably abuts against the inner side surface of the first centrifugal fan housing (2), and a filter disc (17) movably abuts against the inner side surface of the first centrifugal fan housing (2).

6. The centrifugal wind wheel outer rotor series drive device according to claim 1, characterized in that: The driving mechanism comprises a buffer pad (14), wherein the buffer pad (14) is fixedly mounted on the outer surface of the driving rod (7), a controller (15) is fixedly mounted on the outer surface of the driving rod (7), and an inner impeller assembly (16) is fixedly mounted on the outer surface of the controller (15).

7. A centrifugal wind wheel outer rotor series drive device according to claim 6, characterized in that: A filter disc (17) is fixedly mounted on the outer surface of the inner impeller assembly (16), and an outer impeller assembly (18) is fixedly mounted on the outer surface of the filter disc (17), and the filter disc (17) and the outer impeller assembly (18) form an integrated structure.

8. The centrifugal wind wheel outer rotor series drive device according to claim 1, characterized in that: The sealing mechanism comprises a first air outlet (20), the first air outlet (20) being fixedly mounted on the outer surface of a first centrifugal fan housing (2), a connecting pipe (21) being fixedly mounted on the outer surface of the first air outlet (20), and a transmission pipe (22) being fixedly mounted on the outer surface of the connecting pipe (21).

9. The centrifugal wind wheel outer rotor series drive device according to claim 1, characterized in that: A second air outlet (23) is fixedly mounted on the top of the second centrifugal fan housing (3); the second air outlet (23) is in a circular structure, and a driving rod (7) is movably mounted on the inner side surface of the second centrifugal fan housing (3).

10. The centrifugal wind wheel outer rotor series drive device according to claim 6, characterized in that: The outer surface of the driving rod (7) is fixedly mounted with an outer impeller assembly 2 (26), the driving rod (7) is movably mounted on the inner side of the bearing seat (25), and the bearing seat (25) is fixedly mounted on the top of the fixed seat (24).

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