Adjustable pipeline damping fixing device

Abstract

The invention provides an adjustable pipeline damping and fixing device, and relates to the technical field of pipeline installation, the adjustable pipeline damping and fixing device comprises an n-shaped pipeline, and the n-shaped pipeline comprises a vertical pipe section, an S-shaped pipe section and an installation short pipe; four bends are formed on the two S-shaped pipe sections, and a medium circulating in the n-shaped pipeline sequentially passes through the four bends; flow stabilizers are fixedly arranged in the mounting short pipes; and the flow stabilizer is jointly composed of a peripheral retaining ring and a speed reduction grid welded in the retaining ring, the speed reduction grid is formed by welding a plurality of thin hollow pipes in a criss-cross mode, and the retaining ring is welded and fixed to the circumferential inner wall of the mounting short pipe. The rubber shock pad is clamped between the stress hanging lug and the pipeline fixing frame in an extruding mode and used for conducting shock absorption and noise reduction on the n-shaped pipeline, the rubber shock pad is used in cooperation with the flow stabilizer and the bend so that multiple and multiple types of shock absorption and noise reduction can be conducted on the n-shaped pipeline, and the shock absorption and noise reduction effect on the n-shaped pipeline can be further improved.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline installation, and in particular to an adjustable pipeline shock-absorbing fixing device. Background Art

[0002] The pipeline shock-absorbing fixture is a device used to reduce the displacement and damage of pipelines caused by vibration, impact or external force during operation. It is widely used in many fields such as industry, construction, oil and gas, and chemical industry to ensure the stability and safety of the pipeline system.

[0003] There have been some related research and practice in the prior art, such as the utility model patent with publication number CN222047031U, which discloses a pipe fixing device with a shock-absorbing function, including a first buffer structure, a first clamping structure, a first clamping element and a second clamping element. The first buffer structure includes a support element, a buffer spring and a mounting element. One side of the support element contacts the ground, one end of the buffer spring is connected to the support element, and the other end is away from the ground and connected to one side of the mounting element. The mounting element can adjust the distance with the support element; the first clamping structure includes a first rotating rod, the first rotating rod is arranged on one side of the mounting element and can rotate, one end of the first rotating rod is connected to one end of the first clamping element, and the other end of the first clamping element is used to connect with one end of the second clamping element. When the first clamping element is connected to the second clamping element, it can be enclosed and clamped on the outer wall of the pipe, and the clamping component can rotate with the first rotating rod to adjust the clamping angle. The utility model aims to propose a pipe fixing device with a shock-absorbing function that can adjust the clamping angle.

[0004] Most existing fixing devices use a method of installing a shock-absorbing buffer pad between the fixing device and the pipeline to reduce vibration and noise on the pipeline. However, most of them lack a mechanism for pushing the pipeline and the shock-absorbing buffer pad apart to facilitate the replacement of the worn shock-absorbing buffer pad, which makes it inconvenient to disassemble and replace the shock-absorbing buffer pad. The replacement operation of the shock-absorbing buffer pad is relatively troublesome and time-consuming. Summary of the invention

[0005] In view of this, the present invention provides an adjustable pipe shock-absorbing fixing device to solve the problem that the fixing device lacks a mechanism for pushing and separating the pipe and the shock-absorbing buffer pad to facilitate the replacement of the worn shock-absorbing buffer pad, which makes it inconvenient to disassemble and replace the shock-absorbing buffer pad and the replacement operation of the shock-absorbing buffer pad is troublesome and time-consuming.

[0006] The technical solution proposed by the present invention is: an adjustable pipeline shock-absorbing fixing device, specifically comprising an "X"-shaped pipeline, wherein the "X"-shaped pipeline comprises a vertical pipe section, an S-shaped pipe section and a short installation pipe;

[0007] Both ends of the vertical pipe section are symmetrically welded with two S-shaped pipe sections, and installation short pipes are welded to the first ends of the S-shaped pipe sections; four bends are formed on the two S-shaped pipe sections, and the medium flowing in the U-shaped pipe sequentially passes through the four bends; flow stabilizers are fixedly arranged inside the installation short pipes; each flow stabilizer is jointly composed of an outer retaining ring and a deceleration grid welded inside the retaining ring, the deceleration grid is composed of a plurality of thin hollow pipes welded vertically and horizontally, and the retaining ring is welded and fixed to the circumferential inner wall of the installation short pipe.

[0008] Further, it further includes a pipe fixing bracket. The pipe fixing bracket is integrally in a π-shaped hollow structure, and two installation components are symmetrically arranged in the middle part of the two longitudinally arranged side pipes of the pipe fixing bracket; when the medium in the U-shaped pipe flows through the four bends, the four bends will generate a blocking and decelerating effect on the medium flowing through them. By virtue of this blocking and decelerating effect, the four bends can reduce the flow rate of the medium, eliminate the water hammer effect generated when the medium flows, and weaken the vibration and noise generated by the water hammer effect on the U-shaped pipe; the two flow stabilizers can also intercept and decelerate the flowing medium, reducing the vibration and noise generated when the U-shaped pipe is in operation; the cooperation between the flow stabilizers and the bends on the S-shaped pipe section can perform multiple interceptions and decelerations on the flow rate of the medium, effectively improving the vibration and noise reduction effect of the U-shaped pipe.

[0009] Further, the installation component includes a longitudinally arranged main body plate and an L-shaped fixing rod. Two inverted L-shaped fixing rods are symmetrically welded to both ends of the longitudinally arranged main body plate. A positioning screw rod passes through the corner parts of the two L-shaped fixing rods. One end of the positioning screw rod is welded with a hexagonal screwing head, and the other end is screwed with a nut.

[0010] The vertical rod sections of the four L-shaped fixing rods on the two installation components are respectively welded and fixed to the opposite sides of the two longitudinally arranged side pipes of the pipe fixing bracket.

[0011] Further, the installation component further includes an L-shaped limiting plate and a U-shaped pushing frame. Two L-shaped limiting plates are symmetrically welded to the bottom of the longitudinally arranged main body plate. A U-shaped pushing frame is slidably installed through the part of the longitudinally arranged main body plate between the two L-shaped limiting plates. When the U-shaped pushing frame slides downward, the bottom end thereof abuts against the horizontal plate sections of the two L-shaped limiting plates.

[0012] Further, two installation ear blocks are symmetrically welded to the middle bottom positions of the opposite sides of the two longitudinally arranged side pipes of the pipe fixing bracket, and push bolts are screwed through the two installation ear blocks.

[0013] Further, the top ends of the two push bolts respectively pass through the spaces between the two L-shaped limiting plates on the corresponding sides and respectively abut against the middle positions of the bottom ends of the two U-shaped pushing frames.

[0014] Further, rubber shock pads are sleeved on the parts of the two positioning screws located between the two L-shaped fixing rods, and the bottom side of the main body of the rubber shock pad abuts against the top end of the corresponding longitudinal side pipe on the pipe fixing frame.

[0015] Further, two stress hanging ears are symmetrically welded to the middle part of the vertical pipe section. The cross-section of the stress hanging ear is in a U-shaped structure, and the overall stress hanging ear is in a right trapezoidal structure.

[0016] The two stress hanging ears are correspondingly in extrusion abutting contact with the middle parts of the top surfaces of the two rubber shock pads. The rubber shock pads are squeezed and clamped between the stress hanging ears and the pipe fixing frame, which is used to reduce vibration and noise of the U-shaped pipe. When used in cooperation with the flow stabilizer and the bend, it can implement multiple and various forms of vibration and noise reduction for the U-shaped pipe, which helps to further improve the vibration and noise reduction effect on the U-shaped pipe.

[0017] The leading end part of the stress hanging ear protrudes from the rubber shock pad. When the U-shaped pushing frame slides downward, the top end abuts against the protruding part of the stress hanging ear. When the pushing bolt rotates clockwise, it can be pushed to slide upward. When the pushing bolt slides upward, it can push the U-shaped pushing frame to slide upward to push the stress hanging ear to a state separated from the rubber shock pad, and an operation space for disassembling and replacing the rubber shock pad is vacated between the stress hanging ear and the pipe fixing frame, which is convenient and fast to disassemble and replace the rubber shock pad.

[0018] Further, two expansion bolts are installed on both ends of the horizontal side rod of the pipe fixing frame in a spaced and penetrating manner. The pipe fixing frame is fixed to the vertical wall surface in the factory building through the four expansion bolts.

[0019] An adjustable pipe shock absorption fixing device provided by the present invention has the following beneficial effects:

[0020] First, when the medium in the U-shaped pipe flows through the four bends, the four bends will produce a blocking and decelerating effect on the medium flowing through them. By virtue of this blocking and decelerating effect, the four bends can reduce the flow rate of the medium, eliminate the water hammer effect generated when the medium flows, and weaken the vibration and noise generated by the water hammer effect on the U-shaped pipe. The two flow stabilizers can also intercept and decelerate the flowing medium, reducing the vibration and noise generated when the U-shaped pipe is in operation. The flow stabilizer and the bends on the S-shaped pipe section can be used in cooperation to implement multiple interceptions and decelerations of the flow rate of the medium, effectively improving the vibration and noise reduction effect on the U-shaped pipe.

[0021] Second, the rubber shock pads are squeezed and clamped between the stress hanging ears and the pipe fixing frame, which is used to reduce vibration and noise of the U-shaped pipe. When used in cooperation with the flow stabilizer and the bend, it can implement multiple and various forms of vibration and noise reduction for the U-shaped pipe, which helps to further improve the vibration and noise reduction effect on the U-shaped pipe.

[0022] III. When the push bolt rotates clockwise, it can be pushed to drive its body to slide upward. When the push bolt slides upward, it can push the U-shaped push frame upward to push the force-bearing ear to a state of separation from the rubber shock pad, and create an operating space for the rubber shock pad to be disassembled and replaced between the force-bearing ear and the pipe fixing bracket, facilitating the quick disassembly and replacement of the rubber shock pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below.

[0024] The accompanying drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0025] In the accompanying drawings:

[0026] Figure 1 shows the overall structural schematic diagram of the present invention;

[0027] Figure 2 shows the schematic diagram of the installation position of the pipe fixing bracket in the present invention;

[0028] Figure 3 shows the bottom side structural schematic diagram of the pipe fixing bracket in the present invention;

[0029] Figure 4 shows the semi-sectional inner side structural schematic diagram of the U-shaped pipe in the present invention;

[0030] Figure 5 shows the structural schematic diagram of the retaining ring in the present invention;

[0031] Figure 6 shows the present invention Figure 3 the enlarged structural schematic diagram of part A;

[0032] Figure 7 shows the structural schematic diagram of the pipe fixing bracket in the present invention;

[0033] Figure 8 shows the disassembly state schematic diagram of the installation component in the present invention;

[0034] Figure 9 shows the exploded state schematic diagram of the installation component in the present invention.

[0035] LIST OF REFERENCE NUMERALS:

[0036] 1, U-shaped pipe; 101, vertical pipe section; 102, S-shaped pipe section; 103, installation short pipe; 104, force-bearing ear;

[0037] 2, flow stabilizer; 201, retaining ring; 202, deceleration grid;

[0038] 3. Pipe fixing bracket; 301. Expansion bolt; 302. Installation ear block; 303. Thrust bolt; 304. Installation component; 3041. Vertically arranged main body plate; 3042. L-shaped fixing rod; 3043. L-shaped limiting plate; 3044. U-shaped thrust frame; 3045. Positioning screw; 3046. Nut;

[0039] 4. Rubber shock pad. Detailed implementation manner

[0040] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0041] Please refer to Figures 1 to 9 ;

[0042] Embodiment 1:

[0043] The present invention provides an adjustable pipe shock-absorbing fixing device, which includes a U-shaped pipe 1. The U-shaped pipe 1 includes a vertical pipe section 101, an S-shaped pipe section 102 and an installation short pipe 103;

[0044] Both ends of the vertical pipe section 101 are symmetrically welded with two S-shaped pipe sections 102, and the first ends of the S-shaped pipe sections 102 are both welded with installation short pipes 103; four bends are formed on the two S-shaped pipe sections 102, and the medium flowing in the U-shaped pipe 1 sequentially passes through the four bends; flow stabilizers 2 are fixedly arranged inside the installation short pipes 103; the flow stabilizer 2 is jointly composed of an outer retaining ring 201 and a deceleration grid 202 welded inside the retaining ring 201. The deceleration grid 202 is formed by welding a plurality of thin hollow pipes vertically and horizontally, and the retaining ring 201 is fixedly welded to the circumferential inner wall of the installation short pipe 103;

[0045] When the medium in the U-shaped pipe 1 flows through the four bends, the four bends will generate a blocking and decelerating effect on the medium flowing through them. By virtue of this blocking and decelerating effect, the four bends can reduce the flow rate of the medium, eliminate the water hammer effect generated during the medium flow, and weaken the vibration and noise generated by the water hammer effect on the U-shaped pipe 1; the two flow stabilizers 2 can also intercept and decelerate the flowing medium, reducing the vibration and noise generated when the U-shaped pipe 1 is in operation; the flow stabilizer 2 and the bends on the S-shaped pipe section 102 are used in combination to implement multiple interceptions and decelerations of the flow rate of the medium, effectively improving the vibration and noise reduction effect of the U-shaped pipe 1.

[0046] On the basis of Embodiment 1, Embodiment 2:

[0047] An adjustable pipeline shock absorption fixing device further includes a pipeline fixing frame 3. The pipeline fixing frame 3 is integrally in a π-shaped hollow structure, and two installation components 304 are symmetrically arranged in the middle part of the two longitudinally arranged side pipes of the pipeline fixing frame 3.

[0048] Preferably, the installation component 304 includes a longitudinally arranged main body plate 3041 and an L-shaped fixing rod 3042. Two inverted L-shaped fixing rods 3042 are symmetrically welded at both ends of the longitudinally arranged main body plate 3041. A positioning screw 3045 is jointly penetrated through the corner parts of the two L-shaped fixing rods 3042. One end of the positioning screw 3045 is welded with a hexagonal screwing head, and the other end is sleeved with a nut 3046 by screwing;

[0049] The vertical rod sections of the four L-shaped fixing rods 3042 on the two installation components 304 are respectively welded and fixed to the mutually opposite sides of the two longitudinally arranged side pipes of the pipeline fixing frame 3.

[0050] Preferably, the installation component 304 further includes an L-shaped limiting plate 3043 and a U-shaped pushing frame 3044. Two L-shaped limiting plates 3043 are symmetrically welded at the bottom of the longitudinally arranged main body plate 3041. A U-shaped pushing frame 3044 is slidably installed through the part of the longitudinally arranged main body plate 3041 between the two L-shaped limiting plates 3043. When the U-shaped pushing frame 3044 slides downward, the bottom end thereof abuts against the horizontal plate sections of the two L-shaped limiting plates 3043.

[0051] Preferably, two installation ear blocks 302 are symmetrically welded at the middle bottom positions of the mutually opposite sides of the two longitudinally arranged side pipes of the pipeline fixing frame 3. Thrust bolts 303 are screwed through both of the two installation ear blocks 302.

[0052] Preferably, the top ends of the two thrust bolts 303 respectively pass through the spaces between the two L-shaped limiting plates 3043 on the corresponding side, and respectively abut against the middle positions of the bottom ends of the two U-shaped pushing frames 3044.

[0053] Preferably, rubber shock pads 4 are sleeved on the parts of the two positioning screws 3045 between the two L-shaped fixing rods 3042. The bottom side of the main body part of the rubber shock pad 4 abuts against the top end of the corresponding longitudinally arranged side pipe on the pipeline fixing frame 3.

[0054] Preferably, two force-bearing hanging ears 104 are symmetrically welded at the middle part of the vertical pipe section 101. The cross section of the force-bearing hanging ear 104 is in a U-shaped structure, and the force-bearing hanging ear 104 is integrally in a right trapezoidal structure; the two force-bearing hanging ears 104 respectively abut against and are extruded with the middle parts of the top surfaces of the two rubber shock pads 4.

[0055] The pipe fixing bracket 3 is used to carry and fix the U-shaped pipe 1, which helps to improve the installation stability of the U-shaped pipe 1;

[0056] The rubber shock pad 4 is squeezed and clamped between the force-bearing ear 104 and the pipe fixing bracket 3, and is used to reduce vibration and noise of the U-shaped pipe 1. When used in cooperation with the flow stabilizer 2 and the bend, it can implement multiple and various forms of shock absorption and noise reduction for the U-shaped pipe 1, which helps to further improve the shock absorption and noise reduction effect on the U-shaped pipe 1.

[0057] The front end part of the force-bearing ear 104 protrudes from the rubber shock pad 4. When the U-shaped push frame 3044 slides downward, the top end thereof abuts against the protruding part of the force-bearing ear 104;

[0058] When the push bolt 303 rotates clockwise, it can be pushed to slide upward along its own body. When the push bolt 303 slides upward, it can push the U-shaped push frame 3044 to slide upward and separate the force-bearing ear 104 from the rubber shock pad 4, creating an operation space for disassembling and replacing the rubber shock pad 4 between the force-bearing ear 104 and the pipe fixing bracket 3, facilitating the quick disassembly and replacement of the rubber shock pad 4. When disassembling and replacing the rubber shock pad 4, the nut 3046 needs to be rotated and loosened from the positioning screw 3045, and the positioning screw 3045 and the rubber shock pad 4 need to be pulled out.

[0059] Preferably, two expansion bolts 301 are installed at both ends of the horizontal side rod of the pipe fixing bracket 3 in a spaced-through manner. The pipe fixing bracket 3 is fixed to the vertical wall surface in the factory building through four expansion bolts 301.

[0060] The working principle of this embodiment: The pipe fixing bracket 3 is fixed to the vertical wall surface in the factory building through four expansion bolts 301, and the pipe fixing bracket 3 is used to carry and fix the U-shaped pipe 1;

[0061] When the medium in the U-shaped pipe 1 flows through the four bends, the four bends will produce a blocking and decelerating effect on the medium flowing through them. By virtue of this blocking and decelerating effect, the four bends can reduce the flow rate of the medium, eliminate the water hammer effect generated when the medium flows, and weaken the vibration and noise generated by the water hammer effect on the U-shaped pipe 1; the two flow stabilizers 2 can also intercept and decelerate the flowing medium, reducing the vibration and noise generated when the U-shaped pipe 1 is operating; the rubber shock pad 4 is squeezed and clamped between the force-bearing ear 104 and the pipe fixing bracket 3, and is used to reduce vibration and noise of the U-shaped pipe 1;

[0062] When the top push bolt 303 rotates clockwise, it can be advanced to drive its body to slide upward. When the top push bolt 303 slides upward, it can push the U-shaped top push frame 3044 to slide upward and push the force-bearing ear 104 away from the rubber shock pad 4, creating an operating space for disassembling and replacing the rubber shock pad 4 between the force-bearing ear 104 and the pipe fixing bracket 3, and then disassembling and replacing the rubber shock pad 4.

[0063] When disassembling and replacing the rubber shock pad 4, the nut 3046 needs to be rotated and loosened from the positioning screw 3045 and the positioning screw 3045 and the rubber shock pad 4 need to be pulled out.

[0064] In this article, the following points need to be noted:

[0065] 1. The drawings of the embodiments of the present invention only relate to the structures involved in the embodiments of the present invention, and other structures can refer to the general design.

[0066] 2. Without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0067] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An adjustable pipeline shock-absorbing fixing device, comprising a U-shaped pipeline (1), and the U-shaped pipeline (1) includes a vertical pipe section (101), an S-shaped pipe section (102) and a mounting short pipe (103); It is characterized in that Both ends of the vertical pipe section (101) are connected with two S-shaped pipe sections (102) in a symmetric welding form, and mounting short pipes (103) are welded to the first ends of the S-shaped pipe sections (102); four bends are formed on the two S-shaped pipe sections (102), and the medium flowing in the U-shaped pipeline (1) sequentially passes through the four bends; flow stabilizers (2) are fixedly arranged inside the mounting short pipes (103); the flow stabilizer (2) is jointly composed of a peripheral retaining ring (201) and a deceleration grid (202) welded inside the retaining ring (201), the deceleration grid (202) is formed by welding a number of thin hollow pipes vertically and horizontally, and the retaining ring (201) is welded and fixed to the circumferential inner wall of the mounting short pipe (103).

2. An adjustable pipeline shock absorption fixing device according to claim 1, characterized in that, It further includes a pipeline fixing bracket (3), the pipeline fixing bracket (3) is integrally in a π-shaped hollow structure, and two mounting components (304) are symmetrically arranged in the middle part of the two vertical side pipes of the pipeline fixing bracket (3).

3. The adjustable pipeline shock-absorbing and fixing device according to claim 2, characterized in that, The mounting component (304) includes a vertically arranged main body plate (3041) and an L-shaped fixing rod (3042), two inverted L-shaped fixing rods (3042) are symmetrically welded to both ends of the vertically arranged main body plate (3041), a positioning screw (3045) passes through the corner parts of the two L-shaped fixing rods (3042) together, one end of the positioning screw (3045) is welded with a hexagonal screwing head, and a nut (3046) is sleeved and screwed on the other end; The vertical rod sections of the four L-shaped fixing rods (3042) on the two mounting components (304) are respectively welded and fixed to the mutually opposite sides of the two vertical side pipes of the pipeline fixing bracket (3).

4. The adjustable pipeline shock-absorbing and fixing device according to claim 3, wherein The mounting component (304) further includes an L-shaped limiting plate (3043) and a U-shaped pushing frame (3044), two L-shaped limiting plates (3043) are symmetrically welded to the bottom of the vertically arranged main body plate (3041), and a U-shaped pushing frame (3044) is slidably installed through the part of the vertically arranged main body plate (3041) between the two L-shaped limiting plates (3043), and when the U-shaped pushing frame (3044) slides downward, the bottom end thereof abuts against the horizontal plate sections of the two L-shaped limiting plates (3043).

5. An adjustable pipeline shock-absorbing fixing device according to claim 4, characterized in that, Two mounting ear blocks (302) are symmetrically welded to the middle bottom positions of the mutually opposite sides of the two vertical side pipes of the pipeline fixing bracket (3), and two pushing bolts (303) are screwed through the two mounting ear blocks (302).

6. The adjustable pipeline shock-absorbing and fixing device according to claim 5, characterized in that, The top ends of the two pushing bolts (303) respectively pass through the spaces between the two L-shaped limiting plates (3043) on the corresponding sides, and respectively abut against the middle positions of the bottom ends of the two U-shaped pushing frames (3044).

7. An adjustable pipeline shock-absorbing fixing device according to claim 3, characterized in that, Rubber shock-absorbing pads (4) are sleeved on the parts of the two positioning screws (3045) between the two L-shaped fixing rods (3042), and the bottom sides of the main body parts of the rubber shock-absorbing pads (4) abut against the top ends of the corresponding vertical side pipes on the pipeline fixing bracket (3).

8. An adjustable pipeline shock-absorbing fixing device according to claim 4, characterized in that, Two force-bearing lugs (104) are symmetrically welded to the middle part of the vertical pipe section (101). The cross-section of the force-bearing lug (104) is in a U-shaped structure, and the force-bearing lug (104) as a whole is in a right trapezoid structure; The two force-bearing lugs (104) are correspondingly in extrusion abutting contact with the middle parts of the top surfaces of the two rubber shock pads (4); The front end part of the force-bearing lug (104) protrudes from the rubber shock pad (4), and when the U-shaped pushing frame (3044) slides downward, the top end thereof abuts against the protruding part of the force-bearing lug (104).

9. An adjustable pipeline shock-absorbing fixing device according to claim 2, characterized in that, Two expansion bolts (301) are installed at both ends of the horizontal side rod of the pipe fixing frame (3) in a spaced-through manner. The pipe fixing frame (3) is fixed to the vertical wall surface in the factory building by four expansion bolts (301).

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