Thermal shock buffering device and opening control method thereof

Abstract

The invention provides a thermal shock buffering device and an opening control method thereof, the thermal shock buffering device comprises two buffering devices, each buffering device comprises a hollow shell, a storage chip is clamped between the two shells, and the shells are formed through a blow molding process. The shell is made of other molding materials not limited to PP, PE, HDPE or PET, the cost of raw materials is reduced, and meanwhile the phenomenon that the whole device loses efficacy due to the fact that a pressure relief hole of the shell is blocked and other sealing performance problems exist is avoided. The shell is integrally formed through the blow molding process, the production process is simple, and the sealing performance of the shell is improved. The shell is integrally formed, the structure is simplified, the internal space of the phase change unit is increased, the volume of the phase change material is increased, and thermal performance is improved. After the phase change units of the two shells are assembled, a protection cavity is formed in the center, and the interior of the protection cavity is used for installing and protecting a core storage chip.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high temperature protection, in particular to a thermal shock buffering device and a control opening method thereof. BACKGROUND

[0002] High temperature protection generally adopts energy blocking and temperature buffering methods to realize temperature control. In some all-weather conditions, uncertain time and unknown attitude application cases, special design methods and principles are needed to ensure the maintenance-free and high reliability of the thermal buffering device. Typical examples such as airborne black boxes need the function (thermal buffering) to work, and its attitude (forward, reverse, lateral, etc.) and time are random, while in normal times, the thermal buffering medium needs to be zero leakage and the function structure needs to be complete in the environment change of-30~+70℃.

[0003] The phase change material can be vaporized at a specific temperature, breaking the air hole, realizing full conversion and capacity release of the temperature buffering medium, but the existing thermal buffering device is deformed by welding, and the technical cost of stainless steel and welding is high, the construction process is complex, and the sealing performance of the original phase change unit shell after secondary processing needs 100% detection, which takes a long time. At the same time, the secondary processing is easy to cause poor sealing performance, and the through hole after secondary processing is easy to block, resulting in the phenomenon of buffering device failure. At the same time, the existing buffering device is difficult to control the opening temperature of the device, and the opening temperature is not accurate, and sometimes the buffering device is opened without reaching the burst temperature, resulting in the phenomenon of device failure. Therefore, we propose a thermal shock buffering device and a control opening method to solve the above problems. SUMMARY

[0004] The present application provides a thermal shock buffering device and a control opening method, which solves the problem of high technical cost of stainless steel and welding, complex construction process, and 100% detection of sealing performance of the original phase change unit shell after secondary processing, which takes a long time. The through hole after secondary processing is easy to block, resulting in the phenomenon of buffering device failure.

[0005] Another problem solved by the present application is that the existing buffering device is difficult to control the opening temperature of the device, and the opening temperature is not accurate, and sometimes the buffering device is opened without reaching the burst temperature, resulting in the phenomenon of device failure.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: a thermal shock buffering device and a control opening method, including two buffering devices, the buffering device includes a hollow shell, a storage chip is clamped between the two shells, and the shell is formed by blow molding process.

[0007] In the preferred embodiment, the shell is filled with a phase change material, which can be gasified at a predetermined temperature to reduce the temperature of the storage chip area, and the thermal buffering phase change material is a hydrogel. The relationship between the volume of the thermal buffering phase change material and the required thermal buffering energy Q is V1=K1*Q / 2200, where K1=1.5-2.0. The upper limit of the temperature determines the required thermal buffering energy Q, and the volume of the thermal buffering phase change material V1 and K1 are constants.

[0008] In the preferred embodiment, the shell is provided with a concave point, which is an annular concave point or a rectangular concave point; the concave point is a breaking point, and the concave point causes the shell to break at a fixed point. The relationship between the area A of the annular concave point or the rectangular concave point, the depth d of the concave point, and the limit pressure function when breaking is that the limit pressure is proportional to the product of the area and the depth of the concave point: σlim1= K2*A*d. Where K2 is a proportional constant representing the degree of influence of the material properties and the shape of the concave point on the limit pressure.

[0009] In the preferred embodiment, the volume of the shell and the limit pressure that the shell can withstand have a functional relationship: V0=V1+V1*K2 / σlim1. Where V0 represents the volume of the shell (which may be determined by the size parameters of the shell), V1 represents the volume of the phase change material in the shell, σlim1 represents the limit pressure that the shell can withstand, and K2 is a proportional constant representing the gas-liquid ratio of the phase change material at the predetermined temperature.

[0010] In the preferred embodiment, the top of the shell is provided with a plurality of convex points, which are support convex strips, the support convex strips form a turning convex strip with the shell, and stress concentration is formed at the convex strip. The length of the convex strip and the number of convex strips have a limit pressure or limit function relationship when breaking: σlim2=K3*N / L. The length (L), the number (N), the limit pressure (σlim2) when breaking, and K3 are a proportional constant representing the degree of influence of the shape and number of convex points on the limit pressure. The shell is made of other plastic materials other than PP, PE, HDPE, or PET.

[0011] In the preferred embodiment, the storage chip is provided with support clamping pieces at both ends, the buffering device is provided with equipment limiting grooves and communication grooves, and the support clamping pieces are located on the equipment limiting grooves of the shell.

[0012] In the preferred embodiment, the shell is provided with an anti-sealing device, the anti-sealing device is provided with an anti-overflow sealing tape, the anti-sealing device includes a mounting seat, a fastener, and an exhaust member, the shell is provided with a groove and a mounting hole, and the anti-overflow sealing tape is pasted on the top of the mounting hole.

[0013] In the preferred embodiment, the mounting seat comprises an outer ring, the bottom of the outer ring is provided with a bottom ring, the inner wall of the outer ring is provided with a first thread, and the outer ring abuts against the mounting hole; The fastener comprises a hollow barrel, the barrel is provided with a second outer ring, the outer wall of the second outer ring is provided with a third thread, the inner wall of the barrel is provided with a second thread, the second outer ring is connected with the first thread, and the barrel is provided with a plurality of flat-bottomed holes; The exhaust member comprises a hollow exhaust barrel, the bottom of the exhaust barrel is provided with an arc-shaped bottom cover, the exhaust barrel is provided with a plurality of circumferential arrays of exhaust holes, and the outer side of each layer of exhaust holes is provided with an annular baffle; The top of the exhaust barrel is provided with a fourth thread, and the fourth thread is connected with the second thread.

[0014] A control opening method of a thermal shock buffering device, the method is: S1, determining the opening temperature at which the shell needs to be blasted through a storage chip body; S2, controlling the limit pressure of the shell through the limit pressure function relationship of the concave point by controlling the area size and the depth of the concave point; S3, further controlling the limit pressure that the shell can withstand through the limit pressure function relationship of the convex strip by controlling the length and the number of the convex strip; S4, controlling the deformation of the shell by selecting the material of the shell; when the shell is at room temperature, the limit pressure of the shell is determined by the selected material of the shell and the cavity volume size; S5, the internal pressure change factors of the shell include the volume size of the phase change ball, the heating temperature of the phase change ball, and the cavity pressure change of the shell; S6, controlling the opening of the shell when reaching the predetermined temperature by controlling the pressure change in the shell: When the buffering device needs to be blasted at a predetermined temperature, the limit pressure that the shell can withstand in steps S2-S4 is the same as the changed pressure in the shell, so that the shell annular concave point or rectangular concave point is blasted at this time.

[0015] When the storage chip needs to be blasted, the limit pressure that the shell can withstand in steps S2-S4 is the same as the changed pressure in the shell, so that the storage chip is blasted at this temperature. In the preferred embodiment, a solid phase change material is arranged in the shell.

[0016] The beneficial effects of the present invention are as follows: the shell is made of HDPE or other plastic materials, the cost of raw materials is reduced, and the phenomenon of poor shell sealing caused by opening through holes in the shell is avoided. At the same time, the phenomenon of through holes being blocked due to opening through holes in the shell, which causes the shell to be unable to be blasted due to blockage and the failure of the entire device when it is needed to be blasted, is avoided. The shell is integrally formed using a blow molding process, which simplifies the production process and improves the sealing performance of the shell. The integral molding structure of the shell is simplified, the internal space of the phase change unit is increased, the volume of the phase change material is increased, and the thermal performance is improved. After the phase change units of the two shells are assembled, a protective cavity is formed in the center, and the interior is used to install and protect the core storage memory chip.

[0017] The present application controls the ultimate pressure of the shell by controlling the concave points and convex strips on the shell; controlling the material of the shell; the deformation of the shell and the size of the shell cavity.

[0018] Because when the shell reaches the phase change temperature, the shell deformation volume increases, the cavity inside the shell increases, and there is a hysteresis in the shell explosion. When the memory chip reaches the explosion temperature, the pressure of the cavity inside the shell is equal to the ultimate pressure of the shell, and the shell explodes, thereby controlling the explosion temperature of the memory chip. By controlling the composition of the phase change ball, the volume of the phase change ball, and the phase change function of the heating temperature inside the shell, the ultimate pressure inside the shell can be controlled, which has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and examples; Figure 1 It is a front view of the overall structure of the present invention; Figure 2 It is an exploded view of the overall structure of the present invention; Figure 3 is an axonometric view of the outer shell of the present invention from another perspective; Figure 4 This invention Figure 3 A magnified view of ; Figure 5 is a cross-sectional view of the buffer device of the present invention; Figure 6 is a cross-sectional view of the anti-blocking device of the present invention; Figure 7 is an exploded view of the anti-blocking device of the present invention; Figure 8 is an axial side view of the exhaust member of the present invention; Figure 9 is an axial side view of the fastener of the present invention; In the figure: buffer device 1; equipment limit groove 101; connecting groove 102; shell 2; groove 201; mounting hole 202; annular concave point 3; rectangular concave point 4; supporting ridge 5; supporting clip 6; phase change ball 7; storage chip 8; anti-overflow sealing tape 9; anti-blocking device 10; mounting seat 11; outer ring 1101; bottom ring 1102; first thread 1103; fastener 12; cylinder 1201; second outer ring 1202; second thread 1203; third thread 1204; flat bottom hole 1205; exhaust member 13; exhaust pipe 1301; fourth thread 1302; arc-shaped bottom cover 1303; annular baffle 1304; exhaust hole 1305. DETAILED DESCRIPTION

[0020] Example 1: like Figures 1-9 In the invention, a thermal shock buffer device and a method for controlling its opening are provided, comprising two buffer devices 1, wherein the buffer device 1 comprises a hollow shell 2, a storage chip 8 is sandwiched between the two shells 2, and the shell 2 is formed by a blow molding process. With this structure, the shell 2 is made of HDPE or other plastic materials, which reduces the cost of raw materials and avoids the phenomenon of poor sealing of the shell 2 caused by opening a through hole in the shell 2. At the same time, it avoids the phenomenon of blockage of the through hole due to opening a through hole in the shell 2, which makes it impossible for the shell 2 to be blasted due to the blockage, and the failure of the entire device. The shell 2 is integrally formed by a blow molding process, which simplifies the production process and improves the sealing performance of the shell. The shell 2 is simplified as an integral molding structure, and the internal space of the phase change unit is increased, which increases the volume of the phase change material and improves the thermal performance. After the phase change units of the two shells 2 are assembled, a protective cavity is formed in the center, and the interior is used to install and protect the core storage chip 8.

[0021] The present application controls the ultimate pressure of the shell 2 by controlling the concave points and convex strips on the shell 2; controlling the material of the shell 2; the deformation of the shell 2 and the size of the cavity of the shell 2.

[0022] Because when the shell 2 reaches the phase change temperature, the deformation volume of the shell 2 increases, the cavity inside the shell 2 increases, and there is a hysteresis in the explosion of the shell 2. When the storage chip 8 reaches the explosion temperature, the pressure of the cavity inside the shell 2 is equal to the ultimate pressure of the shell 2, and the shell 2 explodes, thereby controlling the explosion temperature of the storage chip 8. By controlling the composition of the phase change ball 7, the volume of the phase change ball 7, and the phase change function of the heated temperature inside the shell 2, the ultimate pressure inside the shell 2 is controlled.

[0023] In the preferred embodiment, the housing 2 is filled with a phase change material 7, which can be vaporized at a predetermined temperature to reduce the temperature of the storage chip 8 area, and the thermal buffer phase change material 7 is a hydrogel; The relationship between the volume of the thermal buffer phase change material 7 and the required thermal buffer energy Q is: V1=K1*Q / 2200, where K1=1.5~2.0; The upper limit of temperature determines the required thermal buffering energy Q; the volume V1 of the thermal buffering phase change material 7, and K1 is a constant.

[0024] In the preferred embodiment, the shell 2 is provided with a concave point, which is a ring-shaped concave point 3 or a rectangular concave point 4; the concave point is a breaking point, and the concave point causes the shell 2 to break at a fixed point. The area size A of the ring-shaped concave point 3 or the rectangular concave point 4, the depth d of the concave point, and the limit pressure function relationship at the time of breaking are: the product of the pressure and the area and depth of the concave point is in a proportional relationship: σlim1= K2*A*d K2 is a proportional constant, which represents the degree of influence of the material properties and the shape of the concave point on the limit pressure.

[0025] In the preferred embodiment, the volume size of the shell 2 and the limit pressure that the shell 2 can withstand have a functional relationship: V0=V1+V1*K2 / σlim1 V0 represents the volume size of the shell, which can be determined by the size parameters of the shell, V1 represents the volume size of the phase change material 7 in the shell, σlim1 represents the limit pressure that the shell can withstand, and K2 is a proportional constant, which represents the gas-liquid ratio of the phase change material at a preset temperature.

[0026] In the preferred embodiment, the top of the shell 2 is provided with a plurality of convex points, which are support convex strips 5, the support convex strips 5 form a turning convex strip with the shell 2, and stress concentration is formed at the convex strip; The length of the convex strip and the number of convex strips and the limit pressure or limit function relationship at the time of breaking are: σlim2=K3*N / L The length L, the number N, and the limit pressure σlim2 at the time of breaking, and K3 is a proportional constant, which represents the degree of influence of the shape and number of convex points on the limit pressure.

[0027] In the preferred embodiment, the storage chip 8 is provided with a support clamp 6 at both ends, the buffering device 1 is provided with a device limiting groove 101 and a communication groove 102, and the support clamp 6 is located on the device limiting groove 101 of the shell 2.

[0028] In the preferred embodiment, the shell 2 is provided with a plugging prevention device 10, the plugging prevention device 10 is provided with an anti-overflow sealing tape 9, the plugging prevention device 10 includes a mounting seat 11, a fastener 12, and an exhaust member 13, the shell 2 is provided with a recess 201 and a mounting hole 202, and the anti-overflow sealing tape 9 is pasted on the top of the mounting hole 202.

[0029] In the preferred embodiment, the mounting seat 11 includes an outer ring 1101, the bottom of the outer ring 1101 is provided with a bottom ring 1102, the inner wall of the outer ring 1101 is provided with a first screw thread 1103, and the outer ring 1101 abuts against the mounting hole 1102; The fastener 12 comprises a hollow barrel 1201, the barrel 1201 is provided with a second outer ring 1202, the outer wall of the second outer ring 1202 is provided with a third thread 1204, the inner wall of the barrel 1201 is provided with a second thread 1203, the second outer ring 1202 is connected with the first thread 1103, and the barrel 1201 is provided with a plurality of flat bottom holes 1205; The exhaust member 13 comprises a hollow exhaust barrel 1301, the bottom of the exhaust barrel 1301 is provided with an arc-shaped bottom cover 1303, and the exhaust barrel 1301 is provided with a plurality of circumferential arrayed exhaust holes 1305, and the outer side of each layer of exhaust holes 1305 is provided with an annular baffle 1304; The top of the exhaust barrel 1301 is provided with a fourth thread 1302, and the fourth thread 1302 is connected with the second thread 1203. Through the structure, the exhaust member 13 extends into the bottom of the fastener 12, the exhaust member 13 is rotated, the fourth thread 1302 is connected with the second thread 1203, the top of the exhaust member 13 is flush with the top of the fastener 12, the structure of the fastener 12 and the exhaust member 13 extends into the air of the bottom ring 1102, the two ends of the clamp extend into the flat bottom hole 12011, the fastener 12 and the structure of the exhaust member 13 are rotated, the first thread 1103 is connected with the third thread 1204, the fastener 12 is flush with the top of the mounting base 11, the plurality of annular baffles 1304 on the exhaust member 13 can penetrate the bottom ring 1102, the exhaust member 13 can penetrate the mounting base 11, and the overall structure of the anti-sealing device 10 is kept horizontal at the top, so that the anti-overflow sealing tape 9 is conveniently pasted.

[0030] The bottom of the exhaust member 13 is provided with the arc-shaped bottom cover 1303, and the exhaust holes 1305 are located on the side of the exhaust barrel 1301. During the process that the spherical phase change material becomes large, the phase change material at the bottom of the exhaust member 13 cannot block the exhaust holes 1305, the plurality of annular baffles 1304 on the outer side of the exhaust barrel 1301 can block the direct contact between the exhaust holes 1305 and the phase change material during the process that the phase change material becomes large. At the same time, when the gaseous phase change material suddenly meets the relatively cold material of the exhaust member 13, if the phase change material suddenly liquefies, the liquid can flow down along the annular baffles 1304 along the outer wall, further avoiding the blocking of the exhaust holes 1305 and avoiding the failure of the overall structure.

[0031] The solid phase change material in the overall device is gasified, so that the temperature buffer medium has reached a saturated state when sealed, the sealing property of the phase change unit temperature buffer medium in a normal environment is solved, a corresponding switch can be opened at a specific high temperature, and sufficient conversion and capacity release of the temperature buffer medium are realized.

[0032] The anti-overflow sealing tape 9 is made of low melting alloy or low melting plastic material, and the body of the anti-overflow sealing tape 9 is not damaged or changed in nature at -40-110°C. When the temperature reaches the set melting point, the anti-overflow sealing tape 9 melts, opens the phase change unit exhaust channel, and ensures its thermal performance.

[0033] Embodiment 2: Further illustrated in combination with Embodiment 1: a control opening method of a thermal shock buffering device, the method is: S1, determine the opening temperature at which the shell 2 needs to be burst through the storage chip 8 body; S2, control the limit pressure of the shell 2 through the limit pressure function relationship of the concave point, the area size of the concave point and the depth of the concave point; S3, further control the limit pressure that the shell 2 can withstand through the limit pressure function relationship of the convex strip, the length and the number of the convex strip; S4, control the deformation of the shell 2 by selecting the material of the shell 2; the cavity volume size of the shell 2 at room temperature, the limit pressure of the shell 2 is determined by the material selection and the cavity volume size of the shell 2; S5, the internal pressure change factors of the shell 2 include the volume size of the phase change ball 7, the heated temperature of the phase change ball 7, and the cavity pressure change of the shell 2; S6, control the opening of the shell 2 when reaching the predetermined temperature by controlling the pressure change in the shell 2: When the buffering device 1 needs to burst at a predetermined temperature, the limit pressure that the shell 2 can withstand in steps S2-S4 is the same as the changed pressure in the shell 2, so as to control the burst of the shell annular concave point 3 or the rectangular concave point 4 at this time.

[0034] The above embodiments are only preferred technical solutions of the present application, and should not be regarded as a limitation of the application. The protection scope of the present application should be based on the technical solutions claimed in the claims, including the equivalent replacement solutions of the technical features claimed in the claims. That is, within this range, equivalent replacement improvements are also within the protection scope of the present application.

Claims

1. A thermal shock buffering device, characterized by: The application relates to a buffer device (1) comprising two hollow housings (2) which hold a storage chip (8) therebetween, and the housings (2) are formed by a blow molding process.

2. The thermal shock buffering apparatus of claim 1, wherein: The housing (2) is internally provided with a phase change material (7), the phase change material (7) can be gasified at a predetermined temperature to reduce the temperature of the storage chip (8) region, and the thermal buffer phase change material (7) is a hydrogel; The relationship between the volume of the thermal buffer phase change material (7) and the required thermal buffer energy Q is V1=K1*Q / 2200, wherein K1=1.5-2.0; The upper limit of the temperature determines the required thermal buffer energy Q; The volume V1 of the thermal buffer phase change material (7) and K1 are constants.

3. The thermal shock buffering apparatus of claim 1, wherein: The housing (2) is provided with a concave point, the concave point is an annular concave point (3) or a rectangular concave point (4); the concave point is a breaking point, and the concave point makes the housing (2) break at the point; The area size A of the annular concave point (3) or the rectangular concave point (4), the depth d of the concave point and the limit pressure function relationship when breaking are as follows: sigma lim1= K2*A*d; Wherein, K2 is a proportional constant, which is used to represent the influence degree of the material properties and the concave point shape on the limit pressure.

4. The thermal shock mitigation device of claim 1, wherein: The functional relationship between the volume size of the housing (2) and the limit pressure borne by the housing (2) is V0=V1+V1*K2 / sigma lim1; Wherein, V0 represents the volume size of the housing (may be determined by the size parameters of the housing), V1 represents the volume size of the phase change material (7) in the housing, sigma lim1 represents the limit pressure borne by the housing, and K2 is a proportional constant, which is used to represent the gas-liquid ratio of the phase change material at the preset temperature.

5. The thermal shock mitigation device of claim 1, wherein: The top of the housing (2) is provided with a plurality of convex points, the convex points are support convex strips (5), the support convex strips (5) and the housing (2) form turning convex strips, stress concentration is formed at the convex strips; The length of the convex strip and the number of the convex strips and the limit pressure or limit function relationship when breaking are as follows: sigma lim2=K3*N / L; The length (L), the number (N) and the limit pressure (sigma lim2) when breaking, and K3 is a proportional constant, which represents the influence degree of the shape and the number of the convex points on the limit pressure.

6. The thermal shock mitigation device of claim 1, wherein: The storage chip (8) is provided with support clamping pieces (6) at two ends, the buffer device (1) is provided with equipment limiting grooves (101) and communication grooves (102), and the support clamping pieces (6) are located on the equipment limiting grooves (101) of the housing (2).

7. The thermal shock mitigation device of claim 1, wherein: The housing (2) is provided with a plugging prevention device (10), the plugging prevention device (10) is provided with an anti-overflow sealing tape (9), the plugging prevention device (10) comprises a mounting seat (11), a fastener (12) and an exhaust member (13), the housing (2) is provided with a recess (201) and a mounting hole (202), and the anti-overflow sealing tape (9) is pasted on the top of the mounting hole (202).

8. The thermal shock mitigation device of claim 8, wherein: The mounting seat (11) comprises an outer ring (1101), the bottom of the outer ring (1101) is provided with a bottom ring (1102), the inner wall of the outer ring (1101) is provided with a first screw thread (1103), and the outer ring (1101) abuts against the mounting hole (1102); The fastener (12) comprises a hollow barrel (1201), the barrel (1201) is provided with a second outer ring (1202), the outer wall of the second outer ring (1202) is provided with a third thread (1204), the inner wall of the barrel (1201) is provided with a second thread (1203), the second outer ring (1202) is connected with the first thread (1103), and the barrel (1201) is provided with a plurality of flat-bottom holes (1205); The exhaust member (13) comprises a hollow exhaust barrel (1301), the bottom of the exhaust barrel (1301) is provided with an arc-shaped bottom cover (1303), the exhaust barrel (1301) is provided with a plurality of circumferential arrays of exhaust holes (1305), and the outer side of each layer of exhaust holes (1305) is provided with an annular baffle (1304); The top of the exhaust barrel (1301) is provided with a fourth thread (1302), and the fourth thread (1302) is connected with the second thread (1203).

9. The control opening method of the thermal shock buffering device according to any one of claims 1-7, wherein the method is: S1, determining the opening temperature at which the shell (2) needs to be burst through the storage chip (8) body; S2, controlling the limit pressure of the shell (2) through the limit pressure function relationship of the concave point, the area size and the depth of the concave point; S3, further controlling the limit pressure that the shell (2) can withstand through the limit pressure function relationship of the convex strip and the length and number of the convex strip; S4, controlling the deformation of the shell (2) by selecting the material of the shell (2); when the shell (2) is at room temperature, the cavity volume size of the shell (2) is determined by the material selection and the cavity volume size of the shell (2), and the limit pressure of the shell (2) is determined; S5, the internal pressure change factors of the shell (2) include the volume size of the phase change ball (7), the heating temperature of the phase change ball (7), and the cavity pressure change of the shell (2); S6, controlling the opening of the shell (2) when reaching the predetermined temperature by controlling the pressure change in the shell (2): When the buffering device (1) needs to be burst at the predetermined temperature, the limit pressure that the shell (2) can withstand in steps S2-S4 is the same as the changed pressure in the shell (2), so as to control the burst of the shell annular concave point (3) or the rectangular concave point (4) at this time.

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