Simple needle assisting module for insulin pump

Abstract

The utility model relates to the technical field of insulin pumps, in particular to a simple needle assisting module for an insulin pump, which comprises a bottom shell, a fluid pushing module, a percutaneous insertion module and a reciprocating driving module, the fluid pushing module, the percutaneous insertion module and the reciprocating driving module are arranged in the bottom shell, a mounting groove is arranged in the bottom shell, the reciprocating driving module comprises a torsion spring, a guide block and a driving block, and the torsion spring has pre-torsion amount. One end of the torsion spring extends outwards and forms a connecting arm, a first limiting groove and a second limiting groove are formed in the installation groove, a strip-shaped groove is formed in the guide block, the driving block comprises a first sliding block used for fixing a needle body and a second sliding block used for fixing a sleeve, the guide block is arranged above the torsion spring, and the connecting arm of the torsion spring is movably arranged in the strip-shaped groove of the guide block. And in the process that the torsional spring releases the pre-torsion amount, the connecting arm drives the guide block to move in the mounting groove in the insertion or retraction direction. The insulin pump achieves needle assisting operation through cooperation of the extension arm at the end of the torsional spring and the guide block, and is simple in structure, convenient to install, good in stability and low in cost.

Description

Technical Field

[0001] The utility model relates to the technical field of insulin pumps, in particular to a simple needle-assisting module for insulin pumps. Background Art

[0002] An insulin pump is a small, computer-controlled medical device that simulates the insulin secretion function of the human pancreas, helping diabetics better control their blood sugar levels. Insulin pumps are becoming increasingly smaller, making them portable. They primarily consist of an injection module and an injection assist module. The injection assist module pushes the indwelling component into the patient's body, while the injection module injects insulin from a reservoir tube into the patient's subcutaneous tissue.

[0003] A search revealed patent publication number CN207768850U, which discloses a needle insertion device comprising a fastener, a rotating unit, and a linear reciprocating unit. This device operates quickly, reliably, and accurately, eliminating the need for the user to remove the needle. However, in actual use, these components are complex and require precise installation, resulting in high costs. Furthermore, since insulin pumps are consumables and typically need to be discarded after three days of use, this places a significant financial burden on patients. Therefore, improvements to the existing insulin pump needle insertion mechanism are needed, simplifying the structure to reduce costs. Utility Model Content

[0004] In order to solve the problems of complex structure and high cost of existing needle insertion devices, the utility model provides a simple needle-assisting module for insulin pumps, which realizes needle-assisting operation through the sliding cooperation of the extension arm at the end of the torsion spring and the guide block. It has a simple structure, easy installation, good stability and low cost.

[0005] The utility model provides a simple needle-assisting module for an insulin pump, comprising a bottom shell and a fluid pushing module, a percutaneous insertion module and a reciprocating drive module arranged in the bottom shell. The fluid pushing module comprises a fluid reservoir and an infusion tube, the fluid reservoir is connected to the infusion tube, the percutaneous insertion module comprises a needle and a cannula, the needle is fixedly connected to the infusion tube and is placed in the inner cavity of the cannula, the reciprocating drive module is used to drive the needle body and the cannula to move along the insertion direction, and is used to drive the needle body to move along the retraction direction, a mounting groove for accommodating the reciprocating drive module is provided in the bottom shell, the reciprocating drive module comprises a torsion spring, a guide block and a drive block, the torsion spring has a pre-torsion The compression direction of the torsion spring is perpendicular to the bottom shell. One end of the torsion spring extends outward and forms a connecting arm. The installation groove is also provided with a limiting groove 1 for accommodating the torsion spring and a limiting groove 2 for allowing the connecting arm to rotate. The limiting groove 2 is arranged above the limiting groove 1. The center of the limiting groove 1 is also provided with a positioning column for the torsion spring to be sleeved. The guide block is provided with a strip groove. The driving block includes a slider 1 for fixing the needle body and a slider 2 for fixing the sleeve. The guide block is placed above the torsion spring. The connecting arm of the torsion spring is movably arranged in the strip groove of the guide block. During the process of releasing the pre-torsion of the torsion spring, the connecting arm drives the guide block to move in the installation groove in the insertion or retraction direction. The cooperation between the connecting arm at the end of the torsion spring and the guide block is used to achieve needle assistance. Under the limiting action of the limiting grooves 1 and 2, the pin insertion has good stability and high reliability.

[0006] Furthermore, a slide groove is provided on the bottom shell for the driving block to slide, one end of the slide groove is connected to the mounting groove, and the other end is provided with a pin hole that penetrates the bottom shell, and the needle is placed in the pin hole. Insertion and retraction are achieved through the cooperation of the driving block and the slide groove.

[0007] Furthermore, a position limit stopper is provided near the pin hole of the slideway to prevent the second slide block from retracting, and a position limit step is provided on the second slide block to match the stopper. The position limit stopper and the position limit step cooperate to prevent the second slide block from retracting.

[0008] Furthermore, the stopper includes a stopper plate near the pin insertion hole and a guide plate away from the pin insertion hole. A wedge surface that mates with the guide plate is provided on the side of the second slider near the pin insertion hole, and a stopper step that mates with the stopper plate is provided on the other side of the second slider. The stopper, through the interaction of the guide plate and the wedge surface, smoothly abuts against the stopper step, limiting the position of the second slider, thereby preventing the cannula from retracting and placing it subcutaneously.

[0009] Furthermore, the position where the torsion spring has a pre-twisted amount is the initial position, and the position where the torsion spring has fully released the pre-twisted amount is the final position. A protrusion is provided in the second limiting groove at a position corresponding to the final position, with the final position and the initial position located on either side of the protrusion. The distance from the initial position to the final position is approximately one full circle. When the connecting arm rotates approximately half a circle from the initial position to complete the pin insertion, it continues to release the remaining torque and rotates approximately half a circle again to the final position to contact the protrusion, completing the pin removal.

[0010] Furthermore, one end of the guide block is connected to the slider 1 via a connecting rod 1, and the other end of the guide block is provided with a connecting rod 2. The bottom shell is provided with an avoidance groove for the sliding movement of the connecting rod 2, and the avoidance groove is connected to the mounting groove. The horizontal movement of the guide block is guided by the connecting rods 1 and 2.

[0011] Furthermore, the fluid pushing module also includes a pump assembly, which includes a piston and a screw, one end of the screw is connected to the piston, the piston is located in the fluid reservoir, and the other end of the screw is connected to the drive assembly. The drive assembly drives the pump assembly to push the fluid.

[0012] Furthermore, the drive assembly includes an electromagnetic drive component and a ratchet assembly, the ratchet assembly consists of a first ratchet and a second ratchet, the second ratchet has a ratchet part 2 and a hollow column, one end of the ratchet part 2 is provided with a groove, the hollow column is located in the middle of the other end of the ratchet part 2, the inner wall of the hollow column is provided with an internal thread that cooperates with the external thread of the screw rod, the first ratchet has a ratchet part 1 located in the groove and a convex column connected to the end face of the ratchet part and driven to rotate by the electromagnetic drive component.

[0013] Furthermore, an inner pawl assembly is provided on the inner wall of the groove, and the inner pawl assembly includes an inner spring piece and an inner pawl. The inner spring piece is connected to the inner wall of the groove, and the inner pawl is connected to the inner spring piece.

[0014] Furthermore, an outer pawl assembly is provided on the bottom shell outside the second ratchet. The outer pawl assembly includes an outer spring piece and an outer pawl. The outer spring piece is connected to the bottom shell, and the outer pawl is connected to the outer spring piece.

[0015] The pawls are engaged with the corresponding ratchet wheels respectively, making the infusion smoother and more accurate. Moreover, due to the one-way transmission mechanism of the ratchet wheel and pawl, the screw rod can only drive in one direction to push out the liquid medicine.

[0016] The beneficial effects of the present invention are:

[0017] (1) The utility model provides a simple needle-assisting module for an insulin pump, which realizes needle-assisting by cooperating with a connecting arm extending from the end of a torsion spring and a guide block. The required movement space is small, and the guide block and the connecting arm are limited and guided by limiting grooves 1 and 2 respectively. The needle insertion has good stability and high reliability, making the insulin pump more portable and flat.

[0018] (2) The utility model provides a simple needle-assisting module for an insulin pump. By arranging a torsion spring in a limiting groove of the bottom shell so that its compression direction is perpendicular to the direction of the needle insertion, and placing the torsion spring in the middle of the sliding path of the guide block, the force transmission is more efficient and the loss of force in motion conversion is reduced;

[0019] (3) The utility model provides a simple needle-assisting module for an insulin pump. By limiting the guide block in the installation groove of the bottom shell, the length direction of the installation groove is consistent with the direction of the needle insertion, ensuring that the guide block slides stably during the release of the torsion spring, that is, ensuring stable needle insertion and withdrawal, the overall structural stability is higher, the assembly yield is higher, and the failure rate during transportation and use is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the structure of an insulin pump;

[0022] Figure 2 This is a schematic diagram of the structure of the insulin pump (the cannula, guide block and drive block are omitted);

[0023] Figure 3 It is a structural diagram of the reciprocating drive module;

[0024] Figure 4 It is a structural diagram of the fluid pushing module;

[0025] Figure 5 This is an exploded view of the fluid push module;

[0026] Figure 6 is a structural schematic diagram of another embodiment of a reciprocating drive module;

[0027] In the figure, 1. bottom shell, 11. mounting slot, 12. limiting slot 1, 13. limiting slot 2, 131. protrusion, 14. slide slot, 15. pin hole, 16. avoidance slot, 17. battery, 18. circuit board, 19. positioning column, 2. fluid reservoir, 3. infusion tube, 4. needle, 5. cannula, 6. torsion spring, 61. connecting arm, 7. guide block, 71. strip slot, 72. connecting rod 1, 73. Connecting rod 2, 8. Driving block, 81. Slider 1, 811. Positioning groove, 82. Slider 2, 83. Limit stopper, 84. Limit step, 91. Piston, 92. Screw, 93. Ratchet part 2, 931. Groove, 94. Hollow column, 95. Ratchet part 1, 951. Boss, 96. Inner spring piece, 97. Inner pawl, 98. Outer spring piece, 99. Outer pawl, 10. Push rod. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0029] In order to facilitate the needle-assisting operation, a simple needle-assisting module for insulin pump is designed. Figure 1-2 As shown, it includes a base shell 1 and a fluid pushing module, a percutaneous insertion module and a reciprocating drive module arranged in the base shell 1. The fluid pushing module includes a fluid reservoir 2 and an infusion tube 3. The fluid reservoir 2 is connected to the infusion tube 3. The percutaneous insertion module includes a needle 4 and a sleeve 5. The needle 4 is fixedly connected to the infusion tube 3 and is placed in the inner cavity of the sleeve 5. The reciprocating drive module is used to drive the needle 4 and the sleeve 5 to move along the insertion direction, and is used to drive the needle 4 to move along the retraction direction. A mounting groove 11 that can accommodate the reciprocating drive module is provided in the base shell 1. A battery 17 and a circuit board 18 are also provided on the base shell 1.

[0030] The fluid stored in fluid reservoir 2 can be medication, nutrients, solutions, or other liquids. When used in home care settings, it can be used to deliver insulin, coagulation factors, chronic disease medications, or other nutrients, or it can be used to deliver cells or other suspended liquids. The percutaneous insertion module is connected to fluid reservoir 2 via infusion tube 3. The reciprocating drive module moves in an insertion direction to insert needle 4 and cannula 5 into the skin. The reciprocating drive module then moves in a retraction direction to remove needle 4 from the skin, placing cannula 5 subcutaneously to complete the injection.

[0031] Specifically, such as Figure 3As shown, the reciprocating drive module includes a torsion spring 6, a guide block 7 and a drive block 8. The torsion spring 6 has a pre-twist amount. The compression direction of the torsion spring 6 is perpendicular to the bottom shell 1. One end of the torsion spring 6 extends outward and forms a connecting arm 61. A limiting groove 12 for accommodating the torsion spring 6 and a limiting groove 2 13 for the connecting arm 61 to rotate are also provided in the mounting groove 11. The limiting groove 2 13 is arranged above the limiting groove 12. A positioning column 19 for the torsion spring 6 to be sleeved is also provided in the center of the limiting groove 12. The torsion spring 6 is placed between the limiting groove 12 and the positioning column 19. A strip groove 71 is provided on the guide block 7. The drive block 8 includes a slider 1 81 for fixing the needle 4 and a slider 2 82 for fixing the sleeve 5. The guide block 7 is placed above the torsion spring 6. The connecting arm 61 of the torsion spring 6 is movably arranged in the strip groove 71 of the guide block 7. During the process of releasing the pre-twist amount of the torsion spring 6, the connecting arm 61 drives the guide block 7 to move in the mounting groove 11 along the insertion or retraction direction. The reciprocating drive module is provided with at least one fastener, which is used to fix the torsion spring 6 with pre-stored torsion that has not been released. When the fastener is removed, the torsion spring 6 releases the pre-twist to drive the connecting arm 61 to rotate and transmit it to the guide block 7. The guide block 7 is horizontally displaced along the pin insertion direction of the installation slot 11 to complete the pin insertion. The torsion spring 6 continues to rotate driven by the remaining torsion and transmits it to the guide block 7. The guide block 7 is horizontally displaced along the retraction direction of the installation slot 11 to bring the needle 4 back, so that the sleeve 5 is placed subcutaneously. The insulin pump is flat as a whole, with good portability and high stability. Under the limiting action of the limiting groove 12, the torsion spring 6 can ensure compression and release in the direction of needle insertion and needle withdrawal, so as to ensure the stability of needle insertion and needle withdrawal and reduce the patient's pain. Under the limiting action of the limiting groove 2 13, the guide block 7 can be driven by the torsion spring 6 to smoothly perform linear displacement along the installation groove 11, avoiding the situation where the needle is not inserted in place due to distortion and displacement, and the movement space required for the guide block 7 to complete the needle insertion and withdrawal is relatively small. In addition, the torsion spring 6 is set in the middle position of the moving path of the guide block 7, which makes the force transmission more stable and efficient, and reduces the loss of force in motion conversion.

[0032] To facilitate smoother needle insertion, the base housing 1 is provided with a slideway 14 through which the drive block 8 slides. One end of the slideway 14 communicates with the mounting slot 11, and the other end defines a needle insertion hole 15 that extends through the base housing 1. The percutaneous insertion module is positioned within the insertion hole 15. The needle 4 and cannula 5 are inserted into the skin through the insertion hole 15, pushed along the slideway 14 by the reciprocating drive module. The needle 4 is then withdrawn from the skin along the slideway 14, repositioning the cannula 5 subcutaneously.

[0033] To prevent the cannula 5 from retracting, a stopper 83 is positioned near the pin insertion hole 15 on the chute 14 to block the retraction of the second slider 82. The second slider 82 is also provided with a stopper step 84 that mates with the stopper. The stopper 83 comprises a stopper plate near the pin insertion hole 15 and a guide plate away from the hole. A wedge surface mates with the guide plate on the side of the second slider 82 near the pin insertion hole 15, while a stopper step 84 mates with the stopper plate on the other side of the second slider 82. When the second slider 82 moves in the direction of the pin insertion, the guide plate abuts against the wedge surface and moves along it to the stopper step 84 at the rear end of the second slider 82. At this point, the stopper step 84 abuts against the stopper plate of the stopper 83, effectively preventing the second slider 83 and, consequently, the cannula 5 from retracting, allowing the cannula 5 to remain stably positioned subcutaneously for infusion.

[0034] The position where the torsion spring 6 has a pre-twisted amount is the initial position, and the position where the torsion spring 6 completely releases the pre-twisted amount is the end position. A protrusion 131 is provided at the position corresponding to the end position in the limiting groove 13, and the end position and the initial position are respectively located on both sides of the protrusion 131. The distance from the initial position to the end position is close to a complete circle. When the connecting arm 61 rotates nearly half a circle from the initial position, that is, the connecting arm 61 is placed in the middle of the strip groove 71 of the guide block 7, the needle insertion is completed. At this time, the slider 2 82 of the driving block 8 is pushed by the connecting rod 1 72 and abuts against the limit stopper 83 in the slide groove 14. Then, the guide block 7 continues to rotate nearly half a circle to the end position and abuts against the protrusion 131 at the end position under the drive of the torsion spring 6 to continue to release the remaining torsion. At this time, the slider 1 81 of the driving block 8 moves in the retraction direction under the drive of the connecting rod 1 72. A positioning groove 811 for fixing the infusion tube 3 is provided on the slider 1 81. The retraction of the slider 1 81 drives the infusion tube 3 to retract, that is, the needle 4 is retracted.

[0035] To ensure more stable movement of the guide block 7, one end of the guide block 7 is connected to the slider 1 81 via the connecting rod 1 72. The other end of the guide block 7 is provided with a connecting rod 2 73. The bottom shell 1 is provided with an escape groove 16 for the sliding movement of the connecting rod 2 73. The escape groove 16 is connected to the mounting groove 11. The length of the escape groove 16 is not less than the length of the connecting rod 2 73. The cooperation between the escape groove 16 and the connecting rod 2 73 guides the guide block 7.

[0036] like Figure 4-5 As shown, to achieve fluid delivery, the fluid delivery module further includes a pump assembly, which includes a piston 91 and a screw 92. One end of the screw 92 is connected to the piston 91, which is located in the fluid reservoir 2, and the other end of the screw 92 is connected to the drive assembly. The drive assembly drives the piston 91 to move along the length of the fluid reservoir 2 to deliver the liquid medicine.

[0037] The drive assembly includes an electromagnetic drive member and a ratchet assembly. The electromagnetic drive member includes an electromagnetic coil, a magnet, and a bracket. The ratchet assembly consists of a first ratchet and a second ratchet. The second ratchet has a ratchet portion 93 and a hollow column 94. A groove 931 is defined at one end of the ratchet portion 93. The hollow column 94 is located in the middle of the other end of the ratchet portion 93. The inner wall of the hollow column 94 is provided with an internal thread that mates with the external thread of the screw rod 92. The first ratchet has a ratchet portion 95 located within the groove 931 and a protrusion 951 connected to the end face of the ratchet portion 95 and driven to rotate by the electromagnetic drive. An inner pawl 97 assembly is provided on the inner wall of the groove 931. The inner pawl 97 assembly includes an inner spring 96 and an inner pawl 97. The inner spring 96 is connected to the inner wall of the groove 931, and the inner pawl 97 is connected to the inner spring 96. An outer pawl 99 assembly is provided on the bottom shell 1 outside the second ratchet. The outer pawl 99 assembly includes an outer spring piece 98 and an outer pawl 99 . The outer spring piece 98 is connected to the bottom shell 1 , and the outer pawl 99 is connected to the outer spring piece 98 .

[0038] The first ratchet is driven to rotate by the electromagnetic drive component, which in turn causes the second ratchet to rotate. When the screw rod 92 rotates, it can drive the piston 91 to move in the fluid reservoir 2, thereby injecting the medicine into the patient's body through the cannula 5. The pawls are engaged with the corresponding ratchets respectively, so that the transmission process is smoother and the transmission amount is more accurate when the pawls and ratchets are engaged, thereby more accurately controlling the amount of medicine injected into the patient. At the same time, due to the one-way transmission mechanism of the ratchet pawl, the screw rod 92 can only be driven in one direction, so that the medicine can be pushed out by controlling the piston 91.

[0039] like Figure 6 As shown, to further simplify the structure, the reciprocating drive module can also be configured as a lever 10. One end of the torsion spring 6 extends outward and upward to form a connecting arm 61. The lever 10 is connected to the drive block 8. The torsion spring 6 has a pre-twisted value. When the fastener used to release the pre-twisted value of the torsion spring 6 is toggled, the connecting arm 61 applies a thrust to the lever 10, pushing the drive block 8 to move the needle 4 and cannula 5 along the insertion direction of the slide 14. Under the action of the needle 4, the cannula 5 penetrates the patient's body and is stopped by the limit stop 83 and retained subcutaneously, while the needle 4 is retracted by the slider 81. When the torsion spring 6 is toggled in the opposite direction to return to the pre-twisted value and secured with the fastener, the lever 10 returns to its initial position.

[0040] The above description is only illustrative and not restrictive of the present invention. Those skilled in the art will understand that many modifications, changes or equivalents may be made without departing from the spirit and scope defined by the appended claims, but all of them will fall within the scope of protection of the present invention.

Claims

1. A simple needle-assisting module for an insulin pump, comprising a bottom shell (1) and a fluid pushing module, a percutaneous insertion module and a reciprocating drive module arranged in the bottom shell (1). The fluid pushing module comprises a fluid reservoir (2) and a fluid infusion tube (3), wherein the fluid reservoir (2) is connected to the fluid infusion tube (3). The percutaneous insertion module comprises a cannula (5) and a needle (4) connected to the end of an infusion tube (3), wherein the infusion tube (3) is placed in the inner cavity of the cannula (5). The reciprocating drive module is used to drive the needle (4) and the sleeve (5) to move in the insertion direction, and is used to drive the needle (4) to move in the retraction direction. Its characteristics are: The reciprocating drive module includes A torsion spring (6), wherein the torsion spring (6) has a pre-twisted amount, and one end of the torsion spring (6) extends outward and forms a connecting arm (61), A guide block (7) is provided with a strip groove (71), and A driving block (8), the driving block (8) comprising a slider 1 (81) for fixing the needle (4) and a slider 2 (82) for fixing the sleeve (5), The guide block (7) is placed above the torsion spring (6), and the connecting arm (61) of the torsion spring (6) is movably arranged in the strip groove (71) of the guide block (7). When the torsion spring (6) releases the pre-twisted amount, the connecting arm (61) drives the guide block (7) to move along the insertion direction or the retraction direction.

2. The simple needle-assisting module for an insulin pump according to claim 1, characterized in that: A mounting groove (11) capable of accommodating a reciprocating drive module is provided in the bottom shell (1), and both ends of the guide block (7) abut against the inner wall of the mounting groove (11).

3. The simple needle-assisting module for an insulin pump according to claim 2, characterized in that: A limiting groove (12) capable of accommodating a torsion spring (6) is provided in the installation groove (11), and a positioning column (19) for the torsion spring (6) to be sleeved is further provided at the center of the limiting groove (12), and the torsion spring (6) is placed between the limiting groove (12) and the positioning column (19).

4. The simple needle-assisting module for an insulin pump according to claim 3, characterized in that: A second limiting groove (13) for the connection arm (61) to rotate is provided in the installation groove (11), and the second limiting groove (13) is provided above the first limiting groove (12).

5. The simple needle-assisting module for an insulin pump according to claim 2, characterized in that: One end of the guide block (7) is connected to the slider (81) via the connecting rod (72), and the other end of the guide block (7) is provided with the connecting rod (73). The bottom shell (1) is provided with an avoidance groove (16) for the sliding movement of the connecting rod (73), and the avoidance groove (16) is communicated with the mounting groove (11).

6. The simple needle-assisting module for an insulin pump according to claim 2, characterized in that: The bottom shell (1) is provided with a slide groove (14) for the driving block (8) to slide. One end of the slide groove (14) is connected to the installation groove (11), and the other end is provided with a pin hole (15) that passes through the bottom shell (1). The needle head (4) is placed in the pin hole (15).

7. The simple needle-assisting module for an insulin pump according to claim 6, characterized in that: One end of the slide groove (14) close to the pin insertion hole (15) is provided with a limit stopper (83) for preventing the second slide block (82) from retracting.

8. The simple needle-assisting module for an insulin pump according to claim 7, characterized in that: The second sliding block (82) is provided with a limiting step (84) adapted to the limiting stopper (83).

9. The simple needle-assisting module for an insulin pump according to claim 8, characterized in that: The limit stopper (83) includes a limit plate close to the pin hole (15) and a guide plate away from the pin hole (15); a wedge surface adapted to the guide plate is provided on one side of the slider (82) close to the pin hole (15); and a limit step (84) adapted to the limit plate is provided on the other side of the slider (82).

10. The simple needle-assisting module for an insulin pump according to claim 4, characterized in that: The position where the torsion spring (6) has a pre-twisted amount is the initial position, and the position where the torsion spring (6) completely releases the pre-twisted amount is the end position. A protrusion (131) is provided at a position corresponding to the end position in the second limiting groove (13), and the end position and the initial position are respectively located on both sides of the protrusion (131).

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