A radial strength testing device for a fireworks launch tube

Abstract

This invention provides a radial strength testing device and method for fireworks launchers. The device includes a support mechanism, a positioning mechanism, and a compression mechanism. The positioning mechanism includes multiple wedge-shaped clamps arranged in a ring array on the support mechanism and disc springs sleeved on the multiple wedge-shaped clamps. Each wedge-shaped clamp forms an expansion sleeve. The inner cylindrical surface of the fireworks launcher is sleeved on the outer surface of the multiple wedge-shaped clamps. The compression mechanism includes a conical mandrel located on the side of the wedge-shaped clamps away from the support mechanism, a drive assembly for driving the conical mandrel to move towards the wedge-shaped clamps, and a pressure sensor connected to the conical mandrel. This invention can apply pressure to fireworks launchers in industrial applications, causing the expansion sleeve to drive the fireworks launcher to generate radial displacement, thereby quickly measuring the radial strength and obtaining a displacement-strength curve. Based on the radial strength, the mechanical property curves of the fireworks launcher can then be obtained, yielding the elastic, yield, and tensile strength parameters of the fireworks launcher.

Description

Technical Field

[0001] This invention relates to the field of fireworks launcher testing technology, and in particular to a radial strength testing device for fireworks launchers. Background Technology

[0002] The core function of a fireworks launcher is as a specialized tubular device for loading and launching fireworks shells; this device needs to be tested before leaving the factory.

[0003] In existing technologies, the most basic tensile, compression and torsion tests are generally used to test fireworks launch tubes. There is a lack of equipment for rapid and effective testing of the radial strength of fireworks launch tubes, which makes it impossible to study the mechanical properties of fireworks launch tubes in real application scenarios. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a radial strength testing device for fireworks launch tubes. This device addresses the problem that existing technologies generally use basic tensile, compressive, and torsional tests to measure the radial strength of fireworks launch tubes, lacking equipment for rapid and effective testing. This makes it impossible to study the mechanical properties of fireworks launch tubes in real-world application scenarios.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A radial strength testing device for a fireworks launcher includes a support mechanism, a positioning mechanism located on the support mechanism, and a compression mechanism cooperating with the positioning mechanism. The positioning mechanism includes a plurality of wedge-shaped clamps arranged in a ring array on the support mechanism and a disc spring sleeved on the plurality of wedge-shaped clamps. Each wedge-shaped clamp is combined to form an expansion sleeve. The inner cylindrical surface of the fireworks launcher is sleeved on the outer surface of the plurality of wedge-shaped clamps. The compression mechanism includes a conical mandrel located on the side of the wedge-shaped clamps away from the support mechanism, a driving component for driving the conical mandrel to move toward the wedge-shaped clamps, and a pressure sensor connected to the conical mandrel. The support mechanism includes a base plate sleeve, and the side of the base plate sleeve near the conical mandrel is recessed to form a relief groove for the conical part to enter.

[0007] According to one aspect of the above technical solution, the support mechanism further includes a workbench, a clamping plate located on the workbench, and a base plate located on the clamping plate. The base plate is fixedly connected to the base plate, the clamping plate and the base plate are connected by a first bolt, and the base plate and the base plate is connected by a second bolt.

[0008] According to one aspect of the above technical solution, the wedge-shaped clamp includes a wedge-shaped portion and an extension portion extending from the wedge-shaped portion in a direction away from the other wedge-shaped clamps. The extension portion is located at the upper end of the wedge-shaped portion, and the outer surface of the wedge-shaped portion is recessed to form a placement groove. The disc spring is disposed in the placement groove of each of the wedge-shaped portions.

[0009] According to one aspect of the above technical solution, the driving assembly includes a press located above the positioning mechanism, a punch fixed to the side of the press near the positioning mechanism, a displacement sensor connecting the press and the clamping plate, a guide post disposed on the side of the press near the clamping plate, and a guide sleeve disposed on the side of the clamping plate near the press. The guide post is slidably disposed on the guide sleeve, and the pressure sensor is connected to the punch.

[0010] According to one aspect of the above technical solution, the conical mandrel includes an integrally formed cylindrical part and a conical part. The cylindrical part is fixedly connected to the pressure sensor by a third bolt. A plurality of wedge-shaped parts surround a receiving space, and the conical part is used to extend into the receiving space.

[0011] According to one aspect of the above technical solution, the extrusion mechanism further includes a bushing surrounding the outer cylindrical surface of the cylindrical portion, a base body surrounding the outer cylindrical surface of the bushing, a pressure cap fixed to the side of the base body near the wedge-shaped clamp, and a return spring connecting the bushing and the cylindrical portion. The cylindrical portion is slidably connected to the bushing, the side of the bushing near the extension portion is used to extrude the extension portion, and the pressure cap surrounds the side of the extension portion.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] By setting a positioning mechanism on the support structure and a compression mechanism that cooperates with the positioning mechanism, when it is necessary to test the radial strength of the fireworks launch tube, the fireworks launch tube is fitted onto the outer surface of each wedge-shaped clamp, so that the inner wall of the fireworks launch tube is tightly fitted with the outer wall of the wedge-shaped clamp. Then, the conical mandrel is driven by the drive assembly to extend between multiple wedge-shaped clamps, so that multiple wedge-shaped clamps are compressed and deformed outward. Because the inner wall of the fireworks launch tube is tightly fitted with the outer wall of the wedge-shaped clamp, the fireworks launch tube will produce the same deformation, thus enabling the fireworks launch tube to achieve the deformation effect in actual use scenarios. The disc spring can fix multiple wedge-shaped clamps, ensuring that each wedge-shaped clamp is subjected to uniform force when compressed by the conical mandrel, and can deform evenly. To achieve stable clamping of the fireworks launcher, a pressure sensor collects the axial force transmitted by the conical mandrel in real time. Then, a conversion algorithm calculates the radial force borne by the fireworks launcher based on the axial force. By continuously loading the conical mandrel to increase the axial force, the radial force reaches the target value. Under the action of the target radial force, the integrity of the launcher's appearance is verified. The radial strength of the fireworks launcher is then tested to obtain the displacement strength curve. Based on the radial strength, the mechanical performance curve of the fireworks launcher is obtained, yielding the elastic, yield, and tensile strength parameters. Depending on the type of fireworks launcher, the actual working conditions of the launcher are determined, and thus, the appropriate strength parameters are used to verify the strength of the fireworks launcher in practical applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the radial strength testing device for a fireworks launch tube in an embodiment of the present invention;

[0015] Figure 2 for Figure 1 Exploded view of the structure in the image;

[0016] Figure 3 for Figure 2 Exploded view of the structure of the main body, bushing, and gland;

[0017] Figure 4 for Figure 2 Exploded view of the structure at the expansion sleeve and base plate jacket;

[0018] Figure 5 for Figure 4 A schematic diagram of the expansion sleeve from a top view;

[0019] Figure 6 for Figure 2 A schematic diagram of the structure at the conical mandrel;

[0020] Figure 7 for Figure 1 Cross-sectional view in the middle;

[0021] Explanation of key component symbols:

[0022]

[0023] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0025] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] Please see Figures 1 to 7 The image shows a radial strength testing device for a fireworks launch tube according to an embodiment of the present invention. It includes a support mechanism 30, a positioning mechanism 40 located on the support mechanism 30, and a compression mechanism 50 that cooperates with the positioning mechanism 40. The positioning mechanism 40 includes a plurality of wedge-shaped clamps 23 arranged in a ring array on the support mechanism 30, and a disc spring 13 sleeved on the plurality of wedge-shaped clamps 23. Each wedge-shaped clamp 23 is combined to form an expansion sleeve 11. The inner cylindrical surface of the fireworks launch tube 12 is sleeved on the outer surface of the plurality of wedge-shaped clamps 23. The compression mechanism 50 includes a conical mandrel 21 located on the side of the wedge-shaped clamps 23 away from the support mechanism 30, a driving component for driving the conical mandrel 21 to move toward the wedge-shaped clamps 23, and a pressure sensor 19 connected to the conical mandrel 21.

[0028] Understandably, this invention, by setting a positioning mechanism 40 on the support mechanism 30 and a compression mechanism 50 that cooperates with the positioning mechanism 40, allows the fireworks launch tube 12 to be fitted onto the outer surface of each wedge-shaped clamp 23 when the radial strength of the fireworks launch tube 12 needs to be tested. This ensures that the inner wall of the fireworks launch tube 12 is tightly fitted to the outer wall of the wedge-shaped clamp 23. Then, the conical mandrel 21 is driven by the drive assembly to extend between multiple wedge-shaped clamps 23, causing the multiple wedge-shaped clamps 23 to be compressed and deformed outward. Because the inner wall of the fireworks launch tube 12 is tightly fitted to the outer wall of the wedge-shaped clamp 23, the fireworks launch tube 12 will produce the same deformation, thus enabling the fireworks launch tube 12 to achieve the deformation effect required in actual use scenarios. The disc spring 13 can fix multiple wedge-shaped clamps 23, ensuring that each wedge-shaped clamp 23 is subjected to the conical mandrel 21. The pressure is uniform during compression, allowing for uniform deformation and thus stable clamping of the fireworks launch tube 12. The axial force transmitted by the conical mandrel 21 is collected in real time by the pressure sensor 19. Then, the radial force borne by the fireworks launch tube 12 can be calculated based on the axial force through a conversion algorithm. By continuously loading the conical mandrel 21 to increase the axial force, the radial force reaches the target value. Under the action of the target value of radial force, the integrity of the tube's appearance is verified. The radial strength of the fireworks launch tube 12 is tested in sequence to obtain the displacement strength curve. Then, based on the radial strength, the mechanical performance curve of the fireworks launch tube is obtained, and the elastic, yield, and tensile strength parameters of the fireworks launch tube are obtained. According to different types of fireworks launch tubes, the actual working conditions of the fireworks launch tube are determined, and then the strength parameters used to verify the strength of the fireworks launch tube in actual application are determined.

[0029] Specifically, in this embodiment, the support mechanism 30 includes a workbench 8, a clamping plate 7 located on the workbench 8, a base plate 4 located on the clamping plate 7, and a base plate sleeve 10 fixed to the base plate 4. The clamping plate 7 and the base plate 4 are connected by a first bolt 5, and the base plate 4 and the base plate sleeve 10 are connected by a second bolt 9.

[0030] Understandably, the base plate sleeve 10 is annular, and a ring array of multiple wedge-shaped clamps 23 is arranged on the bottom of the base plate sleeve 10.

[0031] Furthermore, the wedge-shaped clamp 23 includes a wedge-shaped portion 232 and an extension portion 231 extending from the wedge-shaped portion 232 in a direction away from the other wedge-shaped clamps 23. The extension portion 231 is located at the upper end of the wedge-shaped portion 232. The outer surface of the wedge-shaped portion 232 is recessed to form a placement groove 233. The disc spring 13 is disposed in the placement groove 233 of each wedge-shaped portion 232. The conical mandrel 21 includes an integrally formed cylindrical portion 211 and a conical portion 212. The cylindrical portion 211 is fixedly connected to the pressure sensor 19 by a third bolt 18. The plurality of wedge-shaped portions 232 form a receiving space. The conical portion 212 is used to extend into the receiving space.

[0032] Understandably, the inner surfaces of multiple wedge-shaped portions 232 enclose each other to form a conical receiving space, which is for the conical portion 212 to enter. Since multiple wedge-shaped clamps 23 are spaced apart on the base plate sleeve 10, when the wedge-shaped portion 232 is squeezed, the wedge-shaped portion 232 will expand outward from the bottom end to drive the fireworks launch tube 12 to expand outward. The purpose of setting the placement groove 233 in the recess on the outer surface of the wedge-shaped portion 232 is to make the disc spring 13 located in the placement groove 233, so as to prevent the fireworks launch tube 12 from not being able to fit tightly with the outer surface of the wedge-shaped portion 232.

[0033] Furthermore, the driving assembly includes a press 1 located above the positioning mechanism 40, a punch 20 fixed to the side of the press 1 near the positioning mechanism 40, a displacement sensor 2 connecting the press 1 and the clamping plate 7, a guide post 3 disposed on the side of the press near the clamping plate, and a guide sleeve 6 disposed on the side of the clamping plate near the press. The pressure sensor 19 is connected to the punch 20. The extrusion mechanism 50 also includes a bushing 15 surrounding the outer cylindrical surface of the cylindrical portion 211, a base body 16 surrounding the outer cylindrical surface of the bushing 15, a pressure cap 14 fixed to the side of the base body 16 near the wedge-shaped clamping plate 23, and a return spring 17 connecting the bushing 15 and the cylindrical portion 211. The cylindrical portion 211 is slidably connected to the bushing 15. The side of the bushing 15 near the extension portion 231 is used to extrude the extension portion 231. The pressure cap 14 surrounds the side of the extension portion 231.

[0034] Understandably, the press 1 and punch 20 drive the tapered mandrel 21 downwards, and the displacement sensor 2 records the descent distance in real time. When the bushing 15 contacts the extension 231 of each wedge-shaped clamp 23, the pressure cap 14 just surrounds the side of the extension 231, and the tapered mandrel 21 continues to slide down along the bushing 15 (at this time, the bushing 15 is blocked and cannot descend), causing each wedge-shaped clamp 23 to expand outwards. At this time, the return spring 17 is compressed. When the tapered mandrel 21 rises, the return spring 17 resets the tapered mandrel 21 back to its original position. Then, the bushing 15 no longer contacts the extension 231 of the wedge-shaped clamp 23, and the test ends. The function of the bushing 15 is to cooperate with the tapered mandrel 21 for positioning, ensuring that the tapered mandrel 21 can accurately and stably transmit force when subjected to force, and push the expansion sleeve 11 composed of each wedge-shaped clamp 23 to move synchronously in a straight line. The function of the pressure cap 14 is to limit the expansion sleeve 11 composed of each wedge-shaped clamp 23, prevent the expansion sleeve 11 from being excessively deformed or falling off during the stress process, and ensure the overall stability and safety of the expansion sleeve 11.

[0035] Furthermore, the bottom plate sleeve 10 has a recessed groove 101 on the side near the tapered spindle 21 to allow the tapered portion 212 to enter.

[0036] Understandably, in order for each surface of the inner wall of the wedge-shaped portion 232 to fit tightly against the conical portion 212, the conical portion 212 must extend downward as much as possible. To avoid the apex of the conical portion 212 from colliding with the base plate sleeve 10, a relief groove 101 is provided on the base plate sleeve 10 to accommodate the apex of the conical portion 212.

[0037] In summary, the radial strength testing device for fireworks launch tubes in the above embodiments of the present invention can quickly test the radial strength of fireworks launch tubes in industry.

[0038] A second embodiment of the present invention provides a method for testing the radial strength of a fireworks launcher. This method is based on the radial strength testing device for a fireworks launcher described in the first embodiment and includes the following steps:

[0039] Place the fireworks launch tube on the outer surface of each of the wedge-shaped clamps; this step is to ensure that the inner surface of the fireworks launch tube fits tightly against the outer surface of the wedge-shaped clamps;

[0040] The drive assembly drives the tapered mandrel to move toward the wedge-shaped clamp, causing the wedge-shaped clamp to open under force, and the pressure sensor records the pressure value Faxial.

[0041] Let the normal force on a single wedge-shaped clamp be N, the frictional force be f=μN, the axial force be Faxial / φ, and the wedge angle of the wedge-shaped clamp be θ; where φ represents the number of wedge-shaped clamps; in this embodiment, there are 6 wedge-shaped clamps, so φ is taken as 6.

[0042] Construct the axial force balance equation and the radial force balance equation between the wedge-shaped clamp and the tapered mandrel;

[0043] By combining the axial force balance equation and the radial force balance equation, the solution to the equation is obtained;

[0044] Substituting the solution of the equation into the radial force balance equation of a single wedge-shaped clamp, the radial force of a single wedge-shaped clamp is obtained, and then the total radial expansion force of the wedge-shaped clamp is obtained.

[0045] The radial pressure of the wedge-shaped clamp is calculated based on the total radial expansion force of the wedge-shaped clamp.

[0046] Specifically, the axial force balance equation is as follows:

[0047] ;

[0048] Substituting f=μN into the axial force balance equation, we get:

[0049] ;

[0050] The radial force balance equation is:

[0051] ;

[0052] The solution to the equation is:

[0053] ;

[0054] Substituting the solution into the radial force equilibrium equation, we get:

[0055] ;

[0056] The formula for the total radial expansion force is:

[0057] ;

[0058] Fradial represents the radial force on a single wedge plate, and FradialS represents the total radial expansion force on all wedge plates.

[0059] The formula for the radial pressure is:

[0060] ;

[0061] in, This indicates the area of ​​the fireworks launch tube.

[0062] The radial pressure of the fireworks launch tube was thus determined.

[0063] The axial length of the fireworks launcher sample was set to 40mm. By changing multiple wedge clamps, launchers with different inner diameters and wall thicknesses could be quickly measured, meeting the requirements for flexible measurement on the test bench. The mechanical properties of four common fireworks launcher materials—paper tubes, molded tubes, antistatic plastics, and stainless steel—were measured and statistically analyzed, covering the mechanical properties of common consumer-grade (0.8-inch, 1.0-inch, 1.2-inch) and professional-grade (1.5-inch, 2.0-inch) tubes. Detailed dimensional specifications are listed in the table below. This provides theoretical support for the selection of materials and structural design of launchers for different combinations of fireworks and small fireworks displays.

[0064] Dimensions (inner diameter, outer diameter, height) of fireworks launch tubes of different specifications

[0065]

[0066] Analysis of the direction of motion and friction force during testing: The tapered mandrel moves downwards along the press, pushing the tapered mandrel downwards (axial direction). As the tapered mandrel moves downwards, the six wedge-shaped clamps expand outwards (radially) along the 10° conical surface of the tapered mandrel, while simultaneously exhibiting an upward sliding tendency relative to the tapered mandrel (opposite to the direction of motion relative to the tapered mandrel). Friction force 𝑓 hinders this relative sliding; therefore, the direction of the friction force acting on the expansion sleeve composed of each wedge-shaped clamp is downwards along the conical surface (opposite to the direction of motion of the expansion sleeve relative to the mandrel).

[0067] In this embodiment, after the step of calculating the radial pressure of the wedge-shaped clamp based on the total radial expansion force of the wedge-shaped clamp, the method further includes:

[0068] The axial force Faxial collected by the pressure sensor is recorded in real time and converted into radial pressure Pradial.

[0069] Verify whether the radial pressure Pradial satisfies the judgment formula; if so, the test is passed.

[0070] ;

[0071] Where S represents the safety factor, which is usually taken as S=1.5 to 2.0 (adjusted according to the safety level of fireworks display), and Pe represents the ultimate pressure under actual working conditions. In this embodiment, it represents the maximum combustion and explosion pressure of black powder.

[0072] After the experiment, check whether the fireworks launch tube has surface defects; otherwise, the test ends.

[0073] This embodiment compares the measured radial strength parameter with the maximum combustion and explosion pressure of black powder under actual application conditions of the fireworks launcher. If the measured radial strength parameter is greater than the maximum combustion and explosion pressure of black powder under actual application conditions of the fireworks launcher, it indicates that the fireworks launcher has passed the test and meets the application scenario. This embodiment provides theoretical and data support for the structural safety and quality of the fireworks launcher.

[0074] The overall testing method is based on the idea of ​​converting the axial force and displacement of the conical mandrel test into radial force and displacement using a wedge clamp. Pressure and displacement are applied using a quasi-static, slow pressurization method, with a force application rate ≤100 N / s. This restricts the axial relative movement between the tested fireworks launch tube and the expansion sleeve formed by the wedge clamp, eliminating the influence of friction. The applied force and displacement in the axial direction are acquired in real time, with a pressure angle designed to be 10°. The force and displacement sensors have accuracies of 10 N and 0.01 mm, respectively. The variation law of radial displacement is depicted through synchronous acquisition of force and displacement, and the yield and fracture strength of the launch tube are calculated based on the variation curve. The sampling rate of the acquisition system is ≥200 Hz.

[0075] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A radial strength testing device for a firework launching tube, characterized by, The device includes a support mechanism, a positioning mechanism located on the support mechanism, and a pressing mechanism that cooperates with the positioning mechanism. The positioning mechanism includes a plurality of wedge-shaped clamps arranged in a ring array on the support mechanism and a disc spring sleeved on the plurality of wedge-shaped clamps. Each wedge-shaped clamp is combined to form an expansion sleeve. The inner cylindrical surface of the fireworks launch tube is sleeved on the outer surface of the plurality of wedge-shaped clamps. The pressing mechanism includes a conical mandrel located on the side of the wedge-shaped clamps away from the support mechanism, a driving component that drives the conical mandrel to move toward the wedge-shaped clamps, and a pressure sensor connected to the conical mandrel. The support mechanism includes a base plate sleeve. The conical mandrel includes an integrally formed cylindrical part and a conical part. The side of the base plate sleeve near the conical mandrel is recessed to form a relief groove for the conical part to enter.

2. The radial strength testing device for a firework launching tube according to claim 1, wherein, The support mechanism further includes a workbench, a clamping plate located on the workbench, and a base plate located on the clamping plate. The base plate is fixedly connected to the base plate, the clamping plate and the base plate are connected by a first bolt, and the base plate and the base plate clamping plate are connected by a second bolt.

3. The radial strength testing device for a firework launching tube according to claim 2, wherein, The wedge-shaped clamp includes a wedge-shaped portion and an extension portion extending from the wedge-shaped portion in a direction away from the other wedge-shaped clamps. The extension portion is located at the upper end of the wedge-shaped portion. The outer surface of the wedge-shaped portion is recessed to form a placement groove. The disc spring is disposed in the placement groove of each wedge-shaped portion.

4. The radial strength testing device of a firework launching tube according to claim 3, wherein, The drive assembly includes a press located above the positioning mechanism, a punch fixed to the side of the press near the positioning mechanism, a displacement sensor connecting the press and the clamping plate, a guide post located on the side of the press near the clamping plate, and a guide sleeve located on the side of the clamping plate near the press. The guide post is slidably mounted on the guide sleeve, and the pressure sensor is connected to the punch.

5. The radial strength testing device of claim 4, wherein, The cylindrical part is fixedly connected to the pressure sensor by a third bolt, and the multiple wedge-shaped parts form a receiving space, with the conical part extending into the receiving space.

6. The radial strength testing device of a fireworks launching tube according to claim 5, wherein, The extrusion mechanism further includes a bushing surrounding the outer cylindrical surface of the cylindrical portion, a base body surrounding the outer cylindrical surface of the bushing, a pressure cap fixed to the side of the base body near the wedge-shaped clamp, and a return spring connecting the bushing and the cylindrical portion. The cylindrical portion is slidably connected to the bushing, the side of the bushing near the extension is used to extrude the extension, and the pressure cap surrounds the side of the extension.

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