A heat-shrinkable terminal

Abstract

The present application relates to a heat-shrinkable terminal, which includes a connecting column, a first blind hole and a second blind hole respectively provided on two end faces of the connecting column, at least two first long grooves provided on the side wall of the connecting column, at least two second long grooves provided on the side wall of the connecting column, and a heat-shrinkable transparent sleeve. The heat-shrinkable transparent sleeve includes a first part sleeved on the connecting column, and a second part and a third part respectively extending outward from both ends of the first part. A first heat-shrinkable ring is provided on the inner wall of the second part, and a second heat-shrinkable ring is provided on the inner wall of the third part. Moisture-sensitive color-changing pigments are coated on the surfaces of the first heat-shrinkable ring and the second heat-shrinkable ring. The present application is used for the connection of electrical circuits, can display the infiltration of water vapor, and provides a reference basis for maintenance or replacement.

Description

Technical Field

[0001] This application relates to the technical field of terminal blocks, and more particularly to a heat shrink terminal. Background Art

[0002] Heat shrink terminals are used for electrical line connections and have the functions of insulation, waterproofing, and stress protection. Existing heat shrink terminals are mostly of an integral structure. After the connected wires are inserted into the internal metal tube from both sides, a hot air gun or other heating methods are used to heat the heat shrink tube wrapped outside the metal tube to make it closely adhere to the wires.

[0003] The heat shrink tube and the wire cannot be completely adhered. During use, as the heat shrink tube ages, the gap between the two will gradually increase. After the gap increases, water vapor will enter, resulting in a reduction or even failure of the performance at the connection. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of this application is to provide a heat shrink terminal that can display the infiltration of water vapor and provide a reference for maintenance or replacement.

[0005] The above object of this application is achieved through the following technical solutions:

[0006] A heat shrink terminal, comprising:

[0007] A connecting post;

[0008] A first blind hole and a second blind hole, respectively provided on two end faces of the connecting post;

[0009] At least two first long grooves are provided on the side wall of the connecting post, the bottom surface is communicated with the inner wall of the first blind hole, one end is a closed end, and the other end is communicated with the end face where the first blind hole is located;

[0010] At least two second long grooves are provided on the side wall of the connecting post, the bottom surface is communicated with the inner wall of the second blind hole, one end is a closed end, and the other end is communicated with the end face where the second blind hole is located;

[0011] A heat shrinkable transparent sleeve, including a first part sleeved on the connecting post and a second part and a third part respectively extending outward from both ends of the first part;

[0012] A first heat shrink ring provided on the inner wall of the second part; and

[0013] A second heat shrink ring provided on the inner wall of the third part;

[0014] Wherein, wet water-changing pigments are coated on the surfaces of the first heat shrink ring and the second heat shrink ring.

[0015] By adopting the above technical solution, after inserting two electric wires into the first blind hole and the second blind hole respectively, the heat-shrinkable transparent sleeve is heated, and the heat-shrinkable transparent sleeve begins to shrink and fit on the surfaces of the connecting column and the electric wires. During this process, the inner diameters of the first blind hole and the second blind hole are reduced simultaneously, tightly wrapping the electric wires. At the same time, the first heat-shrinkable ring and the second heat-shrinkable ring will also completely or partially fit on the surfaces of the electric wires under the push of the heat-shrinkable transparent sleeve. During use, water vapor seeps in through the gap between the heat-shrinkable transparent sleeve and the electric wires and contacts the water-wet color-changing pigment on the adjacent first heat-shrinkable ring or second heat-shrinkable ring, and the water-wet color-changing pigment changes color. This color change can be observed through the heat-shrinkable transparent sleeve, providing a reference basis for maintenance or replacement.

[0016] In a preferred example of the present application: the number of the first heat-shrinkable rings is more than two;

[0017] More than two first heat-shrinkable rings are arranged at intervals on the inner wall of the second part.

[0018] By adopting the above technical solution, more than two first heat-shrinkable rings can form multiple reminders. During use, in the direction close to the connecting column, these first heat-shrinkable rings change color in sequence and there is a time interval between the color changes of every two adjacent first heat-shrinkable rings. In this way, multiple reminders and early reminders can be realized, effectively avoiding the problems of omission or lag that are likely to occur during single reminder.

[0019] In a preferred example of the present application: the number of the second heat-shrinkable rings is more than two;

[0020] More than two second heat-shrinkable rings are arranged at intervals on the inner wall of the third part.

[0021] By adopting the above technical solution, more than two second heat-shrinkable rings can form multiple reminders. During use, in the direction close to the connecting column, these second heat-shrinkable rings change color in sequence and there is a time interval between the color changes of every two adjacent second heat-shrinkable rings. In this way, multiple reminders and early reminders can be realized, effectively avoiding the problems of omission or lag that are likely to occur during single reminder.

[0022] In a preferred example of the present application: the length of the first long groove is 0.7 - 0.9 times the depth of the first blind hole.

[0023] By adopting the above technical solution, a certain distance is reserved between the end of the first long groove close to the first blind hole and the bottom of the first blind hole, and the head of the electric wire connected thereto can be completely wrapped.

[0024] In a preferred example of the present application: in the direction close to the bottom surface of the first blind hole, the width of the first long groove tends to decrease.

[0025] By adopting the above technical solution, the fitting between the side wall of the first blind hole and the electric wire can be made closer.

[0026] In a preferred example of the present application: the length of the second long groove is 0.7 - 0.9 times the depth of the second blind hole.

[0027] By adopting the above technical solution, a distance is reserved between the two ends of the second long groove close to the second blind hole and the bottom of the second blind hole, and the head of the electric wire connected thereto can be completely wrapped.

[0028] In a preferred example of the present application: in the direction close to the bottom surface of the second blind hole, the width of the second long groove tends to decrease.

[0029] By adopting the above technical solution, the fitting between the side wall of the second blind hole and the electric wire can be made closer.

[0030] In a preferred example of the present application: the first heat - shrinkable ring includes more than two first arc - shaped parts;

[0031] More than two first arc - shaped parts can enclose a ring, and the maximum outer diameter of this ring is less than the inner diameter of the second part.

[0032] By adopting the above technical solution, the first heat - shrinkable ring is composed of multiple non - connected first arc - shaped parts, and there are gaps between adjacent first arc - shaped parts. During the shrinkage process of the heat - shrinkable transparent sleeve, these first arc - shaped parts can move with the heat - shrinkable transparent sleeve and tightly fit on the surface of the electric wire, fitting more closely with the electric wire, and further reducing the gap width between the heat - shrinkable transparent sleeve and the electric wire.

[0033] In a preferred example of the present application: the second heat - shrinkable ring includes more than two second arc - shaped parts;

[0034] More than two second arc - shaped parts can enclose a ring, and the maximum outer diameter of this ring is less than the inner diameter of the third part.

[0035] By adopting the above technical solution, the second heat - shrinkable ring is composed of multiple non - connected second arc - shaped parts, and there are gaps between adjacent second arc - shaped parts. During the shrinkage process of the heat - shrinkable transparent sleeve, these second arc - shaped parts can move with the heat - shrinkable transparent sleeve and tightly fit on the surface of the electric wire, fitting more closely with the electric wire, and can further reduce the gap width between the heat - shrinkable transparent sleeve and the electric wire.

[0036] In a preferred example of the present application: in the direction of approaching each other, the inner diameters of the first blind hole and the second blind hole both tend to decrease.

[0037] By adopting the above technical solution, during the process of inserting the wire into the first blind hole or the second blind hole, the wire will undergo slight deformation, and the connection strength between it and the connection post will be further improved.

[0038] In summary, the beneficial technical effects of the present application are as follows:

[0039] 1. When in use, after inserting two wires into the first blind hole and the second blind hole respectively, heat the heat-shrinkable transparent sleeve. The heat-shrinkable transparent sleeve starts to shrink and fits on the surfaces of the connection post and the wire. During this process, the inner diameters of the first blind hole and the second blind hole simultaneously decrease, tightly wrapping the wire. At the same time, the first heat-shrinkable ring and the second heat-shrinkable ring will also all or partially fit on the surface of the wire under the push of the heat-shrinkable transparent sleeve. During the use process, water vapor seeps in through the gap between the heat-shrinkable transparent sleeve and the wire and contacts the water-wet color-changing pigment on the adjacent first heat-shrinkable ring or second heat-shrinkable ring, and the water-wet color-changing pigment changes color. This color change can be observed through the heat-shrinkable transparent sleeve, providing a reference basis for maintenance or replacement.

[0040] 2. A certain distance is reserved between the end of the first long groove close to the first blind hole and the bottom of the first blind hole. During the deformation of the side wall of the first blind hole, the stress concentration phenomenon at this place will be reduced, and cracks can be avoided.

[0041] 3. The first heat-shrinkable ring and the second heat-shrinkable ring are respectively composed of a plurality of non-connected first arc-shaped parts and a plurality of non-connected second arc-shaped parts. There are gaps between adjacent first arc-shaped parts and adjacent second arc-shaped parts. During the shrinking process of the heat-shrinkable transparent sleeve, these first arc-shaped parts and second arc-shaped parts can move along with the heat-shrinkable transparent sleeve and tightly fit on the surface of the wire, fitting more closely with the wire, and further reducing the gap width between the heat-shrinkable transparent sleeve and the wire.

[0042] 4. During the process of inserting the wire into the first blind hole or the second blind hole, the wire will undergo slight deformation, and the connection strength between it and the connection post will be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a three-dimensional structure schematic diagram provided by an embodiment of the present application.

[0044] Figure 2 is based on Figure 1 the given internal structure schematic diagram.

[0045] Figure 3 is based on Figure 1 the given three-dimensional explosion diagram.

[0046] In the figure, 11 is a connecting post, 12 is a first blind hole, 13 is a second blind hole, 14 is a first long groove, 15 is a second long groove, 2 is a heat-shrinkable transparent sleeve, 21 is a first part, 22 is a second part, 23 is a third part, 31 is a first heat-shrinkable ring, 32 is a second heat-shrinkable ring, 311 is a first arc part, and 321 is a second arc part. Specific embodiments

[0047] The following further elaborates on this application with reference to the accompanying drawings.

[0048] Please refer to Figure 1 and Figure 2 , which discloses a heat-shrinkable terminal according to an embodiment of this application. The heat-shrinkable terminal mainly consists of a connecting post 11, a heat-shrinkable transparent sleeve 2, a first heat-shrinkable ring 31, a second heat-shrinkable ring 32, etc.

[0049] The connecting post 11 is cylindrical in shape, having two circular end faces and one side face. A first blind hole 12 and a second blind hole 13 are respectively provided on these two circular end faces. The sum of the depths of the first blind hole 12 and the second blind hole 13 is less than the length of the connecting post 11.

[0050] At least two first long grooves 14 are provided on the side wall of the connecting post 11. The bottom surface of the first long groove 14 is connected to the inner wall of the first blind hole 12. One of its two ends is connected to the end face where the first blind hole 12 is located, and the other end is a closed end. These first long grooves 14 divide the part of the connecting post 11 at the first blind hole 12 into several independent parts.

[0051] At least two second long grooves 15 are also provided on the side wall of the connecting post 11. The second long grooves 15 and the first long grooves 14 are respectively located at both ends of the connecting post 11. The bottom surface of the second long groove 15 is connected to the inner wall of the second blind hole 13. One of its two ends is connected to the end face where the second blind hole 13 is located, and the other end is a closed end. These second long grooves 15 divide the part of the connecting post 11 at the second blind hole 13 into several independent parts.

[0052] The heat-shrinkable transparent sleeve 2 consists of three parts in total, namely a second part 22, a first part 21, and a third part 23, which are sequentially connected together. The first part 21 is sleeved on the connecting post 11, and the second part 22 and the third part 23 are respectively located on both sides of the connecting post 11.

[0053] The first heat-shrinkable ring 31 and the second heat-shrinkable ring 32 are respectively located on the inner walls of the second part 22 and the third part 23. Moisture-sensitive color-changing pigments are coated on their surfaces. When water vapor seeps in along the gap between the heat-shrinkable transparent sleeve 2 and the wire and contacts the first heat-shrinkable ring 31 or the second heat-shrinkable ring 32, the color of the moisture-sensitive color-changing pigment coated on the first heat-shrinkable ring 31 or the second heat-shrinkable ring 32 will change.

[0054] During installation, insert the two wires to be connected into the second part 22 and the third part 23 of the heat-shrinkable transparent sleeve 2 respectively, and then continue to push so that the two wires are inserted into the first blind hole 12 and the second blind hole 13 on the connecting post 11 respectively.

[0055] Then, heat the heat-shrinkable transparent sleeve 2 with a hot air gun or other heating methods. After being heated, the heat-shrinkable transparent sleeve 2 begins to shrink, and its second part 22 and third part 23 will closely adhere to the internal wires.

[0056] During the shrinking process of the first part 21 of the heat-shrinkable transparent sleeve 2, a thrust will be exerted on the outer wall of the connecting post 11. At this time, the inner walls of the first blind hole 12 and the second blind hole 13 will move towards the direction close to the wires, and the moving amplitude is positively correlated with the distance between the inner wall and the bottom surface of the blind hole. When the inner walls of the first blind hole 12 and the second blind hole 13 move towards the wires, the pressure on the contact part with the wires will increase, and the connection strength between the wires and the connecting post 11 will also increase accordingly.

[0057] During use, water vapor in the air will seep in along the gap between the heat-shrinkable transparent sleeve 2 and the wires. Especially when the heat-shrinkable transparent sleeve 2 gradually ages, the amount of water vapor seeping in will become larger and larger. After the water vapor contacts the first heat-shrinkable ring 31 or the second heat-shrinkable ring 32 during the seeping process, it will cause the wet water discoloring pigment coated on them to change color. This discoloration can be seen through the heat-shrinkable transparent sleeve 2 during inspection or daily maintenance. In this way, the staff can perform maintenance or replacement according to the discoloration of the first heat-shrinkable ring 31 or the second heat-shrinkable ring 32, fundamentally eliminating the need for repair after damage.

[0058] Please refer to Figure 2 and Figure 3 As a specific implementation manner of the heat-shrinkable terminal provided by this application, the length of the first long groove 14 is 0.7 - 0.9 times the depth of the first blind hole 12, that is, the length of the first long groove 14 is less than the depth of the first blind hole 12.

[0059] During the shrinking process of the heat-shrinkable transparent sleeve 2, the inner wall of the first blind hole 12 will move towards the direction close to the wires to clamp the wires, and at this time, the head of the wires can be completely wrapped. Compared with the simple plug-in connection method, this connection method has higher connection strength.

[0060] Further, in the direction close to the bottom surface of the first blind hole 12, the width of the first long groove 14 tends to decrease, so that when the inner wall of the first blind hole 12 moves towards the wire, the width between the parts of the inner wall away from the bottom of the first blind hole 12 can also be the same as or even smaller than the width between the parts close to the bottom of the first blind hole 12, which can further improve the connection strength between the wire and the connecting post 11.

[0061] Please refer to Figure 2 and Figure 3 As a specific embodiment of the heat-shrinkable terminal provided by the present application, the length of the first long groove 14 is 0.7-0.9 times the depth of the first blind hole 12, that is, the length of the first long groove 14 is less than the depth of the first blind hole 12.

[0062] During the shrinkage process of the heat-shrinkable transparent sleeve 2, the inner wall of the first blind hole 12 will move towards the wire, clamping the wire, and at this time, the head of the wire can be completely wrapped. Compared with the simple insertion connection method, the connection strength of this connection method is higher.

[0063] Further, in the direction close to the bottom surface of the first blind hole 12, the width of the first long groove 14 tends to decrease, so that when the inner wall of the first blind hole 12 moves towards the wire, the width between the parts of the inner wall away from the bottom of the first blind hole 12 can also be the same as or even smaller than the width between the parts close to the bottom of the first blind hole 12, which can further improve the connection strength between the wire and the connecting post 11.

[0064] Please refer to Figure 2 and Figure 3 As a specific embodiment of the heat-shrinkable terminal provided by the present application, the length of the second long groove 15 is 0.7-0.9 times the depth of the second blind hole 13, that is, the length of the second long groove 15 is less than the depth of the second blind hole 13.

[0065] During the shrinkage process of the heat-shrinkable transparent sleeve 2, the inner wall of the second blind hole 13 will move towards the wire, clamping the wire, and at this time, the head of the wire can be completely wrapped. Compared with the simple insertion connection method, the connection strength of this connection method is higher.

[0066] Further, in the direction close to the bottom surface of the second blind hole 13, the width of the second long groove 15 tends to decrease, so that when the inner wall of the second blind hole 13 moves towards the wire, the width between the parts of the inner wall away from the bottom of the second blind hole 13 can also be the same as or even smaller than the width between the parts close to the bottom of the first blind hole 12, which can further improve the connection strength between the wire and the connecting post 11.

[0067] Please refer to Figure 2 and Figure 3 As a specific embodiment of the heat-shrinkable terminal provided in this application, the number of the first heat-shrinkable rings 31 is more than two. These first heat-shrinkable rings 31 are spaced on the inner wall of the second part 22, and the distance between adjacent first heat-shrinkable rings 31 can be equal or unequal.

[0068] After the number of the first heat-shrinkable rings 31 increases, during the process of water vapor infiltration, the water vapor will contact these first heat-shrinkable rings 31 in the order from outside to inside. After the outermost first heat-shrinkable ring 31 contacts, its color changes, indicating that the water vapor has begun to infiltrate. The more the number of the first heat-shrinkable rings 31 that change color, the more serious the degree of water vapor infiltration.

[0069] During daily inspection or maintenance, repair or replacement can be carried out according to the number and degree of color change of the first heat-shrinkable rings 31.

[0070] Please refer to Figure 2 and Figure 3 As a specific embodiment of the heat-shrinkable terminal provided in the application, the number of the second heat-shrinkable rings 32 is more than two. These second heat-shrinkable rings 32 are spaced on the inner wall of the third part 23, and the distance between adjacent second heat-shrinkable rings 32 can be equal or unequal.

[0071] After the number of the second heat-shrinkable rings 32 increases, during the process of water vapor infiltration, the water vapor will contact these second heat-shrinkable rings 32 in the order from outside to inside. After the outermost second heat-shrinkable ring 32 contacts, its color changes, indicating that the water vapor has begun to infiltrate. The more the number of the second heat-shrinkable rings 32 that change color, the more serious the degree of water vapor infiltration.

[0072] During daily inspection or maintenance, repair or replacement can be carried out according to the number and degree of color change of the second heat-shrinkable rings 32.

[0073] Please refer to Figure 2 and Figure 3 As a specific embodiment of the heat-shrinkable terminal provided in the application, the first heat-shrinkable ring 31 includes more than two first arc-shaped parts 311. These first arc-shaped parts 311 can enclose a ring, and the maximum outer diameter of the ring is smaller than the inner diameter of the second part 22.

[0074] More than two first arc portions 311 within the same first heat-shrinkable ring 31 are circumferentially evenly distributed on the inner wall of the second portion 22. When the first portion 22 shrinks upon heating, the more than two first arc portions 311 within the same first heat-shrinkable ring 31 will simultaneously move towards the wire and tightly adhere to the outer wall of the wire. At this time, adjacent first arc portions 311 within the same first heat-shrinkable ring 31 can be in contact or there is a gap between them, which can reduce the gap width between the heat-shrinkable transparent sleeve and the wire and improve the sealing performance.

[0075] Please refer to Figure 2 and Figure 3 As a specific implementation of the heat-shrinkable terminal provided in the application, the first heat-shrinkable ring 31 includes more than two first arc portions 311. These first arc portions 311 can enclose a ring, and the maximum outer diameter of this ring is smaller than the inner diameter of the second portion 22.

[0076] More than two first arc portions 311 within the same first heat-shrinkable ring 31 are circumferentially evenly distributed on the inner wall of the second portion 22. When the first portion 22 shrinks upon heating, the more than two first arc portions 311 within the same first heat-shrinkable ring 31 will simultaneously move towards the wire and tightly adhere to the outer wall of the wire. At this time, adjacent first arc portions 311 within the same first heat-shrinkable ring 31 can be in contact or there is a gap between them, which can reduce the gap width between the heat-shrinkable transparent sleeve and the wire and improve the sealing performance.

[0077] Please refer to Figure 2 and Figure 3 As a specific implementation of the heat-shrinkable terminal provided in the application, the second heat-shrinkable ring 32 includes more than two second arc portions 321. These second arc portions 321 can enclose a ring, and the maximum outer diameter of this ring is smaller than the inner diameter of the second portion 22.

[0078] More than two second arc portions 321 within the same second heat-shrinkable ring 32 are circumferentially evenly distributed on the inner wall of the second portion 22. When the first portion 22 shrinks upon heating, the more than two second arc portions 321 within the same second heat-shrinkable ring 32 will simultaneously move towards the wire and tightly adhere to the outer wall of the wire. At this time, adjacent second arc portions 321 within the same second heat-shrinkable ring 32 can be in contact or there is a gap between them, which can reduce the gap width between the heat-shrinkable transparent sleeve and the wire and improve the sealing performance.

[0079] Please refer to Figure 2, as a specific embodiment of the heat-shrinkable terminal provided in the application, in the direction close to each other, the inner diameters of the first blind hole 12 and the second blind hole 13 on the connecting column 11 both tend to decrease. In this way, as the insertion depth of the wire increases, the pressure between the inner wall of the first blind hole 12 or the second blind hole 13 will also increase, and the connection strength can be further improved.

[0080] The embodiments of the above specific embodiments are all preferred embodiments of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A heat-shrinkable terminal, characterized in that, it includes: a connecting post (11); a first blind hole (12) and a second blind hole (13), which are respectively arranged on two end faces of the connecting post (11); at least two first long grooves (14), which are arranged on the side wall of the connecting post (11), the bottom surface is communicated with the inner wall of the first blind hole (12), one end is a closed end, and the other end is communicated with the end face where the first blind hole (12) is located. The first long groove (14) divides the part of the connecting post (11) located at the first blind hole (12) into multiple independent parts; at least two second long grooves (15), which are arranged on the side wall of the connecting post (11), the bottom surface is communicated with the inner wall of the second blind hole (13), one end is a closed end, and the other end is communicated with the end face where the second blind hole (13) is located. The second long groove (15) divides the part of the connecting post (11) located at the second blind hole (13) into multiple independent parts; a heat-shrinkable transparent sleeve (2), which includes a first part (21) sleeved on the connecting post (11) and a second part (22) and a third part (23) respectively extending outward from both ends of the first part (21); a first heat-shrinkable ring (31), which is arranged on the inner wall of the second part (22); and a second heat-shrinkable ring (32), which is arranged on the inner wall of the third part (23); wherein, wet water-changing pigments are coated on the surfaces of the first heat-shrinkable ring (31) and the second heat-shrinkable ring (32).

2. The heat-shrinkable terminal according to claim 1, characterized in that: the number of the first heat-shrinkable rings (31) is more than two; more than two first heat-shrinkable rings (31) are arranged at intervals on the inner wall of the second part (22).

3. The heat-shrinkable terminal according to claim 1 or 2, characterized in that: the number of the second heat-shrinkable rings (32) is more than two; more than two second heat-shrinkable rings (32) are arranged at intervals on the inner wall of the third part (23).

4. The heat-shrinkable terminal according to claim 1, characterized in that: the length of the first long groove (14) is 0.7 - 0.9 times the depth of the first blind hole (12).

5. The heat-shrinkable terminal according to claim 4, characterized in that: in the direction close to the bottom surface of the first blind hole (12), the width of the first long groove (14) tends to decrease.

6. The heat-shrinkable terminal according to claim 1 or 4 or 5, characterized in that: the length of the second long groove (15) is 0.7 - 0.9 times the depth of the second blind hole (13).

7. The heat-shrinkable terminal according to claim 6, characterized in that: in the direction close to the bottom surface of the second blind hole (13), the width of the second long groove (15) tends to decrease.

8. The heat-shrinkable terminal according to claim 1, characterized in that: the first heat-shrinkable ring (31) includes more than two first arc-shaped parts (311); more than two first arc-shaped parts (311) can enclose a ring, and the maximum outer diameter of the ring is smaller than the inner diameter of the second part (22).

9. The heat-shrinkable terminal according to claim 1 or 8, characterized in that: The second heat-shrinkable ring (32) includes more than two second arc-shaped parts (321); More than two second arc-shaped parts (321) can be surrounded to form a ring, and the maximum outer diameter of the ring is smaller than the inner diameter of the third part (23).

10. A heat-shrinkable terminal according to claim 1, characterized in that: In the direction close to each other, the inner diameters of the first blind hole (12) and the second blind hole (13) both tend to decrease.

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