Booster pump

Abstract

The invention provides a booster pump, and belongs to the technical field of water pumps. The problem that an existing booster pump is inconvenient to maintain is solved. The booster pump comprises a pump body and a main frame, the main frame is a non-detachable U-shaped component made of sheet plates, two side walls of the main frame are oppositely arranged front and back and are connected through a strip-shaped pull rod, the pump body is fixedly arranged in the main frame, and a water inlet pipe and a water outlet pipe of the pump body penetrate through the side walls of the main frame. A top plate covers the top of the main frame, side plates cover the left side and the right side of the main frame respectively, and the top plate and the two side plates are independently formed and detachably connected with the main frame. According to the booster pump, the booster pump can be conveniently maintained, for example, the circuit board, the pressure tank and the sealing element are overhauled or replaced.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pumps and relates to a booster pump. Background Art

[0002] A booster pump is a device that improves the water flow pressure by driving an impeller to rotate through an electric motor. According to different uses, booster pumps can be divided into industrial-grade booster pumps, circulating booster pumps, household booster pumps, etc. Among them, household booster pumps take into account the characteristics of miniaturization, low noise, and easy installation. At the same time, by integrating the pump body, pressure tank, circuit board, etc. into a closed outer shell, the aesthetics and convenience of home use are improved.

[0003] For example, a centrifugal booster pump disclosed in a patent (Application No.: 202211035849.3) includes a pump body and an electric motor disposed in the pump body. The pump body is provided with a water injection port, a water inlet, a water inlet flow channel, and a water outlet flow channel. A pump cavity is provided in the pump body, and an impeller is disposed in the pump cavity. During the use of the booster pump, maintenance work on key components such as the pressure tank and circuit board will be involved. Similar to conventional household booster pumps, this booster pump integrates components such as the pump body and pressure tank of the booster pump into the outer shell. At the same time, during use, external water pipes need to be connected to the water inlet and outlet of the booster pump respectively. When internal components such as the pressure tank, circuit board, and seal need to be repaired, the external water pipes must be disassembled first, and often the outer shell needs to be completely disassembled for repair. This not only makes the operation cumbersome and inconvenient for maintenance, but also easily causes loosening and leakage at the connection of the external water pipes due to frequent disassembly and assembly, and deformation or even damage of the outer shell, affecting the service life of the booster pump. Summary of the Invention

[0004] The purpose of the present invention is to address the above problems existing in the prior art and propose a booster pump, and the present invention solves the problem of inconvenient maintenance of existing booster pumps.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A booster pump includes a pump body, characterized in that the booster pump further includes a main frame. The main frame is a non-detachable U-shaped member composed of sheet-shaped plates. Its two side walls are arranged opposite to each other front and back, and are connected by strip-shaped tie rods between the two side walls. The pump body is fixedly arranged in the main frame. The water inlet pipe and the water outlet pipe of the pump body both pass through the side walls of the main frame. A top plate is provided on the top of the main frame, and side plates are respectively provided on the left and right sides of the main frame. The top plate and the two side plates are respectively formed independently and are detachably connected to the main frame.

[0006] During the use of this booster pump, the water inlet pipe and the water outlet pipe on the pump body are respectively connected to external water pipes. The top plate and the two side plates are formed independently, which not only meets the requirement of installing the pump body in a closed chamber but also facilitates the disassembly of the top plate and the side plates. For the purpose of facilitating maintenance, the present invention has made an innovative design for the main frame. The main frame is a non-detachable U-shaped member composed of sheet-shaped plates. At the same time, the orientations of the water inlet pipe and the water outlet pipe are also optimized, and both pass through the side walls of the main frame and are connected to the external water pipes. This design enables, during maintenance, without removing the external water pipes, only by removing the top plate and the left and right side plates, an open operation space can be formed by virtue of the open structure of the U-shaped main frame, providing multi-directional operation entrances, and thus facilitating the maintenance of the booster pump, such as the inspection or replacement of the circuit board, the pressure tank, and the seals. Obviously, the structural design of this main frame can avoid the problems of troublesome maintenance and long maintenance time caused by overall disassembly during the maintenance process.

[0007] At the same time, during the maintenance of the booster pump, the pump body often needs to be in an operating state to facilitate troubleshooting the root cause of the problem. However, the pump body generates vibrations during operation, and at the same time, the water inlet pipe and the water outlet pipe also have pulsating vibrations generated by the water flow. In view of this, the present invention adopts an original design of the main frame with strip-shaped tie rods. The two ends of the strip-shaped tie rods are respectively connected to the two side walls of the main frame, effectively dispersing the vibrations generated during the operation of the pump body and the pulsating vibrations of the water flow in the water inlet pipe and the water outlet pipe. This makes it so that after the left and right side plates and the top plate are removed, the main frame still constitutes a stable frame structure, avoiding deformation or fracture at the connection between the lower edges of the two side walls of the main frame, especially at the connection with the bottom wall, thus avoiding the problem of possible product damage and shortened service life of the booster pump while pursuing convenient maintenance.

[0008] In the above-mentioned booster pump, the left and right side edges of the bottom wall of the main frame are both bent upward to form upward flanges with insertion holes. The openings of the insertion holes are arranged upward. The bottom edge of the side plate is inserted into the insertion holes on the adjacent upward flanges, and the top edge of the side plate is clamped with the top plate. When installing the side plate, first insert the bottom edge of the side plate into the corresponding insertion holes, and then clamp the top edge of the side plate to the top plate to complete the installation of the side plate. Conversely, the disassembly of the side plate can be achieved. This design makes the installation and disassembly of the side plate very convenient, thus making the maintenance of the booster pump more convenient.

[0009] As another case of the detachable connection between the side plates and the top plate, it can be that: between the bottom edge of the side plate and the bottom wall of the main frame, and between the top edge of the side plate and the top plate, bolt connections are used, and between the top plate and the two side walls of the main frame, bolt connections or clamping connections are used. This connection method can also meet the detachable requirements of the side plates and the top plate, thus facilitating the maintenance of the booster pump.

[0010] In the above-mentioned booster pump, the insertion hole is a strip-shaped square hole. An insertion part in the shape of a U-shaped plate protruding downward is integrally formed on the bottom edge of the side plate. The bottom edge of the side plate is inserted into the insertion hole through the insertion part. Limiting steps that abut against the opening edge of the insertion hole are provided on two opposite side walls of the insertion part. The bottom edge of the side plate abuts against the upper end surface of the adjacent upward flanging. The insertion hole is a strip-shaped square hole, and at the same time, the insertion part inserted into it is in the shape of a U-shaped plate, which can increase the cross-sectional area of the insertion part and endow the insertion part with high structural strength. By abutting the limiting steps against the opening edge of the insertion hole and simultaneously abutting the bottom edge of the side plate against the upper end surface of the adjacent upward flanging, not only can the installation position of the side plate be pre-positioned during the installation of the side plate, facilitating the rapid completion of the assembly of the side plate and improving the maintenance convenience of the booster pump, but also, after the assembly is completed, the bottom of the side plate is well supported, enhancing the installation stability of the side plate.

[0011] In the above-mentioned booster pump, downward flangings are formed by bending the left and right side edges of the top plate downward. A plurality of clamping parts in the shape of frames with a pair of clamping tongues inside are integrally formed on each downward flanging. Clamping protrusions corresponding to the clamping parts one by one are integrally formed on the inner side surface of the side plate. The clamping protrusions can be inserted horizontally between the two clamping tongues of the corresponding clamping part and be clamped and positioned by the two clamping tongues.

[0012] The cross-section of the top plate of this structure is U-shaped, which can improve the structural strength of the top plate. During the installation of the side plate, after the insertion part on the bottom edge of the side plate is inserted into the corresponding insertion hole, only need to push the top of the side plate inward. At this time, the clamping protrusions on the side plate can be inserted horizontally between the two clamping tongues of the corresponding clamping part and be clamped and positioned by the two clamping tongues, and at this time, the installation of the side plate is completed. On the contrary, the disassembly of the side plate can be realized. This design makes the installation and disassembly of the side plate very convenient, thus making the maintenance of this booster pump more convenient.

[0013] In the above-mentioned booster pump, the strip-shaped pull rod is horizontally arranged and made of metal material. The number of strip-shaped pull rods on the left and right side parts of the main frame is two each. The two strip-shaped pull rods on the same side are arranged at intervals up and down. The strip-shaped pull rod made of metal material has high strength. The up-and-down interval arrangement of the strip-shaped pull rods not only facilitates the maintenance of the booster pump, but also enables the top and bottom of the main frame to be supported by the strip-shaped pull rods, ensuring that the main frame has higher structural strength, thereby avoiding the situation of deformation or fracture of the main frame, and further avoiding the problem of possible product damage and shortened service life of the booster pump while pursuing convenient maintenance.

[0014] In the above-mentioned booster pump, the two strip-shaped tie rods at the higher positions on the main frame are respectively arranged adjacent to the clamping parts at the left and right sides of the top plate. By arranging the strip-shaped tie rods adjacent to the clamping parts, the strip-shaped tie rods can more effectively share and reduce the vibration load borne by the clamping protrusions and the clamping parts, thereby avoiding the risk of deformation or fracture of the clamping protrusions and the clamping parts. Therefore, the strip-shaped tie rods also have the additional effect of protecting the clamping protrusions and the clamping parts.

[0015] In the above-mentioned booster pump, inward flanges are bent and formed on the left and right sides of the two side walls of the main frame. A plurality of strip-shaped slit holes are arranged at intervals in the vertical direction on the inward flanges. The length direction of the slit holes is arranged vertically. Flaky protrusions corresponding to the slit holes one by one are integrally formed at the front and rear sides of the side plate. The length dimension of the slit holes is greater than the vertical width dimension of the protrusions. The protrusions are inserted horizontally into the corresponding slit holes. The side plate is inserted into the slit holes through the protrusions, further increasing the installation stability of the side plate, so that during the operation of the booster pump, the side plate is not prone to vibration, thereby reducing noise and effectively protecting the side plate, and improving the service life of the booster pump. The length dimension of the slit holes is greater than the vertical width dimension of the protrusions, so that during the installation of the side plate, the protrusions can be smoothly inserted into the slit holes and blind operation can be achieved, thereby improving the convenience of side plate installation. On the contrary, it can also make the side plate disassemble more conveniently, making the maintenance of this booster pump more convenient.

[0016] In the above-mentioned booster pump, protruding parts corresponding to the ends of the strip-shaped tie rods one by one are integrally formed at the left and right sides of the two side walls of the main frame. The ends of the strip-shaped tie rods are fixedly connected to the corresponding protruding parts by bolts. This structure not only makes the installation of the strip-shaped tie rods convenient, but also ensures better installation stability of the strip-shaped tie rods, thereby better supporting the main frame, improving the overall structural strength of the main frame, and better avoiding the problem that the main frame may be damaged and the service life of the booster pump may be shortened while pursuing convenient maintenance.

[0017] In the above-mentioned booster pump, the cross-section of the strip-shaped tie rod is L-shaped. The vertical side wall of the strip-shaped tie rod abuts against the outer side surface of the corresponding protruding part, and the horizontal side wall of the strip-shaped tie rod abuts against the upper side surface of the corresponding protruding part. This design makes the installation stability of the strip-shaped tie rods better. At the same time, the cross-section of the strip-shaped tie rod is L-shaped, which has a relatively high structural strength, thereby better supporting the main frame and improving the overall structural strength of the main frame.

[0018] In the above-mentioned booster pump, the front and rear sides of the top plate are respectively fixedly connected to the main frame by bolts. This structure not only ensures the convenience of disassembling the top plate, but also relies on the fastening force of the bolts to make the top plate and the side plate connected to the top plate have better installation stability.

[0019] Compared with the prior art, the present booster pump has the following advantages:

[0020] 1. By passing both the inlet pipe and the outlet pipe of the pump body through the side wall of the main frame, when the booster pump needs to be repaired, it is not necessary to remove the external water pipes, but only the top plate and the left and right side plates need to be removed, thus forming a very open operation space, and it is very convenient to repair the booster pump, such as inspecting or replacing the circuit board, pressure tank and seals.

[0021] 2. In the present invention, by respectively arranging two upper and lower strip-shaped tie rods on the left and right sides of the main frame, the vibration generated during the operation of the booster pump and the pulse vibration of the inlet pipe and the outlet pipe are effectively dispersed, so that the main frame forms a frame structure with stable structure. In this way, the main frame of the booster pump is not easily damaged, and the booster pump has a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a perspective structural view of the present booster pump.

[0023] Figure 2 is an exploded view of the present booster pump.

[0024] Figure 3 is a perspective structural view of the main frame.

[0025] Figure 4 is a perspective structural view of the bottom wall of the main frame.

[0026] Figure 5 is a perspective structural view of the side plate.

[0027] Figure 6 is a top view of the present booster pump.

[0028] Figure 7 is Figure 6 a perspective cross-sectional view taken along A-A in

[0029] Figure 8 is Figure 7 an enlarged view of part A in

[0030] Figure 9 is Figure 7 an enlarged view of part B in

[0031] Figure 10 is Figure 6 a perspective cross-sectional view taken along B-B in

[0032] Figure 11 is a structural view of the front side wall of the main frame.

[0033] Figure 12 is a structural view of the rear side wall of the main frame.

[0034] Figure 13 It is a three-dimensional structural schematic diagram of the top plate.

[0035] In the figure, 1 is the top plate; 11 is the downward turned edge; 12 is the clamping portion; 121 is the clamping tongue; 2 is the side plate; 21 is the insertion portion; 211 is the limiting step; 22 is the clamping protrusion; 23 is the protrusion; 3 is the pump body; 31 is the water inlet pipe; 32 is the water outlet pipe; 33 is the water injection pipe; 4 is the main frame; 41 is the strip-shaped pull rod; 42 is the upward turned edge; 421 is the insertion hole; 43 is the inward turned edge; 431 is the slit hole; 44 is the protruding portion; 5 is the pressure tank; 6 is the circuit board; 7 is the bolt. Detailed implementation manners

[0036] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0037] Embodiment 1

[0038] As Figures 1 to 3 shown, this booster pump includes components such as the main frame 4, the top plate 1, two side plates 2, the pump body 3, the pressure tank 5, etc. Among them, the main frame 4 is a non-detachable U-shaped member composed of sheet-shaped plates, the two side walls are arranged opposite to each other front and back, and the two side walls are connected by the strip-shaped pull rod 41. The pump body 3 is fixedly arranged in the main frame 4, and the bottom of the pump body 3 is fixedly connected to the bottom wall of the main frame 4 through the bolt 7. The water inlet pipe 31 and the water outlet pipe 32 of the pump body 3 both pass through the front side wall of the main frame 4, and the main water pipe of the pump body 3 passes through the top plate 1. The top plate 1 and the two side plates 2 are both in the shape of rectangular plates and are independently formed respectively. The top plate 1 covers the top of the main frame 4, and the two side plates 2 respectively cover the left and right side parts of the main frame 4 and are both located outside the adjacent strip-shaped pull rods 41. The top plate 1 and the two side plates 2 are respectively detachably connected to the main frame 4. Specifically, the front and rear side edges of the top plate 1 are respectively fixedly connected to the main frame 4 through the bolt 7. The strip-shaped pull rod 41 is horizontally arranged and made of metal material. The number of strip-shaped pull rods 41 on the left and right side parts of the main frame 4 is two each, and the two strip-shaped pull rods 41 on the same side are arranged at intervals up and down.

[0039] As Figures 3 to 5 shown, the left and right side edges of the bottom wall of the main frame 4 are both bent upward to form the upward turned edge 42 with the insertion hole 421. The opening of the insertion hole 421 faces upward. The bottom edge of the side plate 2 is inserted into the insertion hole 421 on the adjacent upward turned edge 42, and the top edge of the side plate 2 is clamped with the top plate 1. Specifically, as Figure 5 and Figure 8As shown, the insertion hole 421 is a strip-shaped rectangular hole. An integrally formed downwardly protruding U-shaped plate-like insertion portion 21 is provided at the bottom edge of the side plate 2. The bottom edge of the side plate 2 is inserted into the insertion hole 421 through the insertion portion 21. Limiting steps 211 that abut against the opening edges of the insertion hole 421 are provided on both opposite side walls of the insertion portion 21. The bottom edge of the side plate 2 abuts against the upper end surface of the adjacent upwardly turned edge 42.

[0040] As Figures 9 to 12 shown, protruding portions 44 corresponding to the ends of the strip-shaped pull rods 41 are integrally formed on the left and right sides of the two side walls of the main frame 4. The ends of the strip-shaped pull rods 41 are fixedly connected to the corresponding protruding portions 44 by bolts 7. The cross-section of the strip-shaped pull rod 41 is L-shaped. The vertical side wall of the strip-shaped pull rod 41 abuts against the outer side surface of the corresponding protruding portion 44, and the horizontal side wall of the strip-shaped pull rod 41 abuts against the upper side surface of the corresponding protruding portion 44. This design makes the installation of the strip-shaped pull rod 41 more stable. At the same time, the cross-section of the strip-shaped pull rod 41 is L-shaped, which has a relatively high structural strength, so as to better support the main frame 4 and improve the overall structural strength of the main frame 4.

[0041] As Figure 5 、 Figure 9 and Figure 13 shown, the left and right sides of the top plate 1 are bent downward to form downwardly turned edges 11. A plurality of frame-shaped clamping portions 12 each having a pair of clamping tongues 121 inside are integrally formed on each downwardly turned edge 11. Clamping protrusions 22 corresponding to the clamping portions 12 are integrally formed on the inner side surface of the side plate 2. The clamping protrusion 22 can be inserted horizontally between the two clamping tongues 121 of the corresponding clamping portion 12 and be clamped and positioned by the two clamping tongues 121. The two strip-shaped pull rods 41 at higher positions on the main frame 4 are respectively adjacent to the clamping portions 12 at the left and right sides of the top plate 1. During the installation of the side plate 2, after the insertion portion 21 at the bottom edge of the side plate 2 is inserted into the corresponding insertion hole 421, only the top of the side plate 2 needs to be pushed inward. At this time, the clamping protrusion 22 on the side plate 2 can be inserted horizontally between the two clamping tongues 121 of the corresponding clamping portion 12 and be clamped and positioned by the two clamping tongues 121. At this time, the installation of the side plate 2 is completed. On the contrary, the disassembly of the side plate 2 can be realized. This design makes the installation and disassembly of the side plate 2 very convenient, thus making the maintenance of this booster pump more convenient.

[0042] As Figure 11 and Figure 12 Inner turned edges 43 are bent on the left and right sides of the two side walls of the main frame 4. A plurality of strip-shaped slit holes 431 are arranged at intervals in the vertical direction on the inner turned edges 43. The length direction of the slit holes 431 is arranged vertically. As Figure 5 and Figure 10As shown, on the front and rear sides of the side plate 2, there are integrally formed sheet-like protrusions 23 that are arranged in one-to-one correspondence with the slit holes 431. The length dimension of the slit holes 431 is greater than the vertical width dimension of the protrusions 23, and the protrusions 23 are inserted horizontally into the corresponding slit holes 431.

[0043] Embodiment 2

[0044] The structure and principle of this embodiment are basically the same as those of Embodiment 1. The difference lies in that between the bottom edge of the side plate 2 and the bottom wall of the main frame 4, and between the top edge of the side plate 2 and the top plate 1, bolt 7 connections are used.

[0045] Embodiment 3

[0046] The structure and principle of this embodiment are basically the same as those of Embodiment 1. The difference lies in that the top plate 1 and the two side walls of the main frame 4 are connected by snap connection. The snap connection structure can adopt the prior art.

[0047] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0048] Although terms such as 1, top plate; 11, downwardly turned edge; 12, snap connection part; 121, snap tongue; 2, side plate; 21, insertion part; 211, limiting step; 22, clamping protrusion; 23, protrusion; 3, pump body; 31, water inlet pipe; 32, water outlet pipe; 33, water injection pipe; 4, main frame; 41, strip-shaped pull rod; 42, upwardly turned edge; 421, insertion hole; 43, inwardly turned edge; 431, slit hole; 44, protruding part; 5, pressure tank; 6, circuit board; 7, bolt are used more in this article, the possibility of using other terms is not excluded. Using these terms is only for more conveniently describing and explaining the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A booster pump, comprising a pump body (3), characterized in that, The booster pump further includes a main frame (4), and the main frame (4) is a non-detachable U-shaped member formed by sheet-shaped plates. Its two side walls are arranged opposite to each other front and back, and are connected by strip-shaped tie rods (41) between the two side walls. The pump body (3) is fixedly arranged inside the main frame (4). The water inlet pipe (31) and the water outlet pipe (32) of the pump body (3) both pass through the side walls of the main frame (4). A top plate (1) is covered on the top of the main frame (4), and side plates (2) are respectively covered on the left and right sides of the main frame (4). The top plate (1) and the two side plates (2) are respectively formed independently and are detachably connected to the main frame (4).

2. The booster pump according to claim 1, wherein, On the left and right sides of the bottom wall of the main frame (4), upward flanges (42) with insertion holes (421) are bent upwards. The openings of the insertion holes (421) face upwards. The bottom edge of the side plate (2) is inserted into the insertion holes (421) on the adjacent upward flanges (42), and the top edge of the side plate (2) is clamped with the top plate (1).

3. The booster pump according to claim 2, characterized in that, The insertion holes (421) are strip-shaped square holes. An insertion part (21) in the shape of a U-shaped plate protruding downwards is integrally formed on the bottom edge of the side plate (2). The bottom edge of the side plate (2) is inserted into the insertion holes (421) through the insertion part (21). Limiting steps (211) that abut against the opening edges of the insertion holes (421) are provided on the two opposite side walls of the insertion part (21). The bottom edge of the side plate (2) abuts against the upper end surface of the adjacent upward flange (42).

4. The booster pump according to claim 1 or 2 or 3, characterized in that, On the left and right sides of the top plate (1), downward flanges (11) are bent downwards. A plurality of clamping parts (12) in the shape of frames with a pair of clamping tongues (121) inside are integrally formed on each downward flange (11). Clamping protrusions (22) corresponding to the clamping parts (12) are integrally formed on the inner side surfaces of the side plates (2). The clamping protrusions (22) can be inserted horizontally between the two clamping tongues (121) of the corresponding clamping parts (12) and are clamped and positioned by the two clamping tongues (121).

5. The booster pump according to claim 4, characterized in that, The strip-shaped tie rods (41) are horizontally arranged and made of metal materials. The number of strip-shaped tie rods (41) on the left and right sides of the main frame (4) is two each. The two strip-shaped tie rods (41) on the same side are arranged at intervals up and down.

6. The booster pump according to claim 5, characterized in that, The two strip-shaped tie rods (41) with higher positions on the main frame (4) are respectively adjacent to the clamping parts (12) at the left and right side edges of the top plate (1).

7. The booster pump according to claim 1 or 2 or 3, characterized in that, On the left and right sides of the two side walls of the main frame (4), inward flanges (43) are bent. A plurality of strip-shaped slit holes (431) arranged at intervals in the vertical direction are formed on the inward flanges (43). The length direction of the slit holes (431) is arranged vertically. Sheet-shaped protrusions (23) corresponding to the slit holes (431) are integrally formed at the front and back side edges of the side plate (2). The length dimension of the slit holes (431) is larger than the vertical width dimension of the protrusions (23). The protrusions (23) are inserted horizontally into the corresponding slit holes (431).

8. The booster pump according to claim 1 or 2 or 3, characterized in that, On the left and right sides of the two side walls of the main frame (4), there are integrally formed protruding parts (44) corresponding to the ends of the strip-shaped pull rods (41) one by one, and the ends of the strip-shaped pull rods (41) are fixedly connected to the corresponding protruding parts (44) by bolts (7).

9. The booster pump according to claim 8, wherein The cross-section of the strip-shaped pull rod (41) is L-shaped. The vertical side wall of the strip-shaped pull rod (41) abuts against the outer side surface of the corresponding protruding part (44), and the horizontal side wall of the strip-shaped pull rod (41) abuts against the upper side surface of the corresponding protruding part (44).

10. The booster pump according to claim 1 or 2 or 3, characterized in that, The front and rear sides of the top plate (1) are fixedly connected to the main frame (4) by bolts (7) respectively.

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