Production method for conical hollow needle

Abstract

Provided is a novel production method for a conical hollow needle that makes it possible to efficiently form a conical part that has a nearly perfectly circular outer circumferential surface shape.　The present invention is a production method for a conical hollow needle 10 that has a conical part 24 that has a tapered outer circumferential surface 20. The production method involves immersing a straight hollow needle 10' in an electrolyte 30 to conically electropolish an outer circumferential surface 24'. From the beginning to the end of the electropolishing, the hollow needle 10', which acts as an anode, is sandwiched between a pair of cathodes 34, 34 at a prescribed distance therefrom in the radial direction, and the hollow needle 10' is rotated around the axis thereof to change which surfaces of the hollow needle 10' are opposite the cathodes 34, 34.

Description

Manufacturing method of conical hollow needle

[0001] The present invention relates to a method for manufacturing a conical hollow needle having a conical portion whose outer circumferential surface is tapered.

[0002] Conventionally, hollow needles with approximately constant inner and outer diameters have been used as injection needles, etc. Also, U.S. Patent No. 5,002,535 (Patent Document 1) discloses a conical hollow needle having a tapered outer circumferential surface in which the outer diameter at the tip end is smaller than the outer diameter at the base end.

[0003] U.S. Pat. No. 5,002,535

[0004] The tapered outer circumferential surface of a conical hollow needle can be formed by mechanical polishing or chemical polishing using a metal-dissolving bath such as an acid. For example, a straight hollow needle, which is the base of the conical hollow needle, can be used, and the outer circumferential surface of the hollow needle can be tapered by chemical polishing while controlling the region immersed in the metal-dissolving bath in the needle length direction and thereby the amount of dissolution of the outer circumferential surface.

[0005] In such chemical polishing, in order to improve the polishing efficiency and make industrial production possible, it is desirable to perform electrochemical polishing (electrolytic polishing) by placing an electrode plate in the bath and passing a current between the electrode plate and the hollow needle.

[0006] However, the inventors' investigations revealed that conventional electrochemical polishing, which simply places one electrode plate opposite the hollow needle, may result in the outer peripheral surface of the electropolished hollow needle becoming irregularly circular. In other words, it became clear that conventional electrochemical polishing using a simple electrode plate results in an irregular outer peripheral surface shape in the conical portion, which may increase the patient's pain during puncture and adversely affect the strength characteristics of the hollow needle.

[0007] An object of the present invention is to provide a novel method for manufacturing a conical hollow needle that can efficiently form a conical portion having an outer peripheral surface shape that is close to a perfect circle.

[0008] The following describes preferred embodiments for understanding the present invention, but the embodiments described below are merely examples and may be appropriately combined with one another. Multiple components described in each embodiment may be recognized and employed independently to the greatest extent possible, and may also be appropriately combined with any of the components described in other embodiments. Accordingly, the present invention is not limited to the embodiments described below, and various other embodiments may be realized.

[0009] The first aspect is a method for manufacturing a conical hollow needle having a tapered conical portion on its outer circumferential surface, in which a straight hollow needle is immersed in an electrolyte to electrolytically polish the outer circumferential surface into a conical shape, and during the process from the start to the end of the electrolytic polishing, a pair of cathodes are arranged to sandwich the hollow needle, which is an anode, at a predetermined distance in the radial direction, and the hollow needle is rotated around the needle axis to change the surface of the hollow needle facing the cathode.

[0010] According to the method for manufacturing a conical hollow needle according to this embodiment, the hollow needle is rotated during the electropolishing process, changing the surface of the hollow needle facing the cathode. This reduces variations in electrolysis efficiency due to differences in the distance and orientation between the outer circumferential surface of the hollow needle and the cathode. Therefore, the conical portion of the outer circumferential surface obtained by electropolishing has an outer circumferential shape closer to a perfect circle, effectively reducing pain during puncture due to the reduced diameter. Furthermore, by making the inner and outer circumferential surfaces of the conical hollow needle each have a cross-sectional shape closer to a perfect circle, a conical hollow needle with excellent strength can be obtained.

[0011] The second aspect is a method for manufacturing a conical hollow needle having a tapered conical portion on the outer circumferential surface, in which a straight hollow needle is immersed in an electrolyte to electrolytically polish the outer circumferential surface into a conical shape, and during the process from the start to the end of the electrolytic polishing, a cathode that radially faces the outer circumferential surface of the hollow needle, which is an anode, is positioned at three or more different positions around the hollow needle.

[0012] According to the method for manufacturing a conical hollow needle according to this embodiment, during the electropolishing process, the cathode is positioned at three or more different positions circumferentially around the hollow needle. This reduces variations in electrolysis efficiency due to differences in the distance and orientation between the outer circumferential surface of the hollow needle and the cathode. Therefore, the conical portion of the outer circumferential surface obtained by electropolishing has an outer circumferential shape that is closer to a perfect circle, and the diameter is small all around, which effectively reduces pain during puncture. Furthermore, by making the inner and outer circumferential surfaces of the conical hollow needle each have a cross-sectional shape that is closer to a perfect circle, a conical hollow needle with excellent strength characteristics can be obtained.

[0013] In a third aspect, in the method for manufacturing a conical hollow needle described in the second aspect, the cathodes are arranged independently of each other around the circumference of the hollow needle, and the cathodes are repositioned relative to the hollow needle so that they are at different positions around the circumference of the hollow needle during the process from the start to the end of electrolytic polishing.

[0014] According to the method for manufacturing a conical hollow needle according to this embodiment, multiple cathodes independently arranged around the circumference of the hollow needle allow for efficient electropolishing of the hollow needle in multiple directions. Furthermore, during the electropolishing process, for example, by moving the outer circumferential surface of the hollow needle and the cathodes relative to each other, the cathodes can be positioned at three or more different positions around the circumference of the hollow needle. Therefore, with fewer cathodes, it is possible to achieve a conical portion closer to a perfect circle.

[0015] In a fourth aspect, in the method for manufacturing a conical hollow needle described in the second aspect, the cathode is arranged to surround the hollow needle, and the cathode simultaneously faces the hollow needle at three or more different positions in the circumferential direction during the process from the start to the end of electrolytic polishing.

[0016] According to the method for manufacturing a conical hollow needle according to this embodiment, for example, by using three or more cathodes or by arranging the cathodes so that they surround the hollow needle, it is possible to make the conical portion closer to a perfect circle without having to rotate the hollow needle or move the cathode.

[0017] A fifth aspect is the method for manufacturing a conical hollow needle according to any one of the second to fourth aspects, wherein the cathode extends in a curved manner in the circumferential direction of the hollow needle.

[0018] According to the method for manufacturing a conical hollow needle according to this embodiment, the radial facing area of ​​the hollow needle relative to the cathode is widened in the circumferential direction, thereby making it possible to obtain a wide area in the circumferential direction of the hollow needle where efficient electrolytic polishing is possible.

[0019] In a sixth aspect, in the method for manufacturing a conical hollow needle according to any one of the first to fifth aspects, a conical portion having a circularity of 0 to 0.0015 mm is formed by electrolytic polishing.

[0020] The manufacturing method of the conical hollow needle according to this aspect makes it possible to obtain a conical hollow needle having a conical portion on its outer surface with a cross-sectional shape that is sufficiently close to a perfect circle. As a result, the diameter of the conical portion is small all around, which reduces pain when puncturing and reduces localized stress concentration in the circumferential direction of the conical hollow needle, thereby achieving excellent strength characteristics for the conical hollow needle.

[0021] The seventh aspect is a method for manufacturing a conical hollow needle having a tapered conical portion on its outer circumferential surface, in which a straight hollow needle is immersed in an electrolyte to electrolytically polish the outer circumferential surface into a conical shape, and a plurality of cathodes are arranged facing and spaced apart from the outer circumferential surface of the hollow needle, which is an anode, and the state of current flow between the hollow needle and the plurality of cathodes is controlled to adjust the electrolytic polishing of the hollow needle by each of the cathodes.

[0022] According to the method for manufacturing a conical hollow needle according to this aspect, for example, for multiple pairs of cathodes arranged opposite each other across the hollow needle in multiple radial directions, the energization state with the hollow needle can be alternately controlled to sequentially switch and adjust the electropolishing region of the hollow needle by each pair of cathodes in the circumferential direction, thereby improving the roundness, as shown in an example in Figure 8 of the embodiment described later.Furthermore, as shown in an example in Figure 9 of the embodiment described later, for example, by controlling the energization time and / or applied voltage of multiple cathodes arranged at different positions in the circumferential direction of the hollow needle, the amount of electropolishing of the hollow needle can be adjusted in the circumferential direction, thereby improving the roundness. Alternatively, as shown in an example in Figure 10 of an embodiment described below, by performing control such as mutually adjusting the current flow time and / or applied voltage for multiple cathodes arranged at different positions along the length of the hollow needle, it becomes possible to adjust the amount of electropolishing in the hollow needle along the length to achieve a conical shape or adjust the inclination angle of the conical portion.

[0023] According to the present invention, a conical portion having an outer peripheral surface shape that is close to a perfect circle can be efficiently formed.

[0024] 1. A plan view showing a conical hollow needle according to a first embodiment of the present invention. A left side view of the conical hollow needle shown in FIG. 1. A cross-sectional view taken along line III-III of FIG. 1. A diagram for explaining a method for manufacturing the conical hollow needle shown in FIG. 1, showing a state in which the metal pipe is not immersed in the electrolyte during the electrolytic polishing process. A diagram for explaining a method for manufacturing the conical hollow needle shown in FIG. 1, showing a state in which the tip of the metal pipe is immersed in the electrolyte during the electrolytic polishing process. A diagram for explaining a method for manufacturing the conical hollow needle shown in FIG. 1, showing a state in which the entire electrolytic polishing region of the metal pipe is immersed in the electrolyte during the electrolytic polishing process. FIG. 2 is an enlarged view illustrating a method for manufacturing a conical hollow needle shown in FIG. 1, showing a first electrolytic polishing step; FIG. 3 is an enlarged view illustrating a method for manufacturing a conical hollow needle shown in FIG. 1, showing a second electrolytic polishing step; FIG. 4 is a view illustrating a method for manufacturing a conical hollow needle according to a second embodiment of the present invention; FIG. 5 is a view illustrating a method for manufacturing a conical hollow needle according to a fifth embodiment of the present invention; FIG. 6 is a view illustrating a method for manufacturing a conical hollow needle according to a sixth embodiment of the present invention;

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] 1 to 3 show a conical hollow needle 10 according to a first embodiment of the present invention. The conical hollow needle 10 is made of a metal such as medical stainless steel. The conical hollow needle 10 has a blade surface 12 at its distal end, which is inclined relative to the needle axis L, and a needle tip 14 at its distal end. In this embodiment, the blade surface 12 has different angles of inclination relative to the needle axis L at its distal end and proximal end. The smaller angle of inclination at the distal end makes the needle tip 14 sharper, but the blade surface 12 may also be a single flat surface with a constant inclination angle throughout. The conical hollow needle 10 has an inner lumen 16 that penetrates in the needle axial direction (the vertical direction in FIG. 1 ) and an inner circumferential surface 18 that forms the wall of the inner lumen 16. The inner circumferential surface 18 has a substantially circular cross-sectional shape and extends straight in the needle axial direction with a substantially constant cross-section. In other words, the conical hollow needle 10 has a substantially constant inner diameter along its entire length in the needle axial direction.

[0027] The outer peripheral surface 20 of the conical hollow needle 10 has a cylindrical portion 22 extending straight with a substantially constant cross section at the base end (upper portion in FIG. 1 ), opposite the needle tip 14, and a tapered conical portion 24 at the tip end (lower portion in FIG. 1 ), facing the needle tip 14. The conical portion 24 is inclined at a substantially constant angle relative to the needle axis L. The angle of inclination of the conical portion 24 relative to the needle axis L is preferably 0.05 degrees or more and 0.35 degrees or less, more preferably 0.09 degrees or more and 0.3 degrees or less, thereby suppressing angular change between the cylindrical portion 22 and the conical portion 24 while sufficiently reducing the diameter of the tip of the conical portion 24. However, the angle of inclination of the conical portion 24 relative to the needle axis L may change gradually or in steps along the needle axis, i.e., the longitudinal direction. Note that the angle of inclination is exaggerated in the figures to make the shape of the conical portion 24 easier to understand.

[0028] The conical portion 24 of the conical hollow needle 10 is formed by electrolytically polishing the tip portion of the metal pipe 10', which is a straight hollow needle, so that it tapers, for example, using an electrolytic polishing device 26 shown in Figures 4A to 4C. Therefore, the conical portion 24 of the conical hollow needle 10 is an electrolytically polished surface formed by electrolytic polishing.

[0029] As shown in Fig. 4A, the metal pipe 10' from which the conical hollow needle 10 is made has an initial shape of a straight cylinder before electropolishing, with both the inner and outer diameters being approximately constant in the axial direction. Furthermore, an anode-side wiring 28 is connected to the metal pipe 10'. One end of the anode-side wiring 28 is electrically connected to the metal pipe 10', which serves as the anode for electrolysis, and the other end is electrically connected to a power supply device (not shown).

[0030] Also, an electrolytic cell 32 containing an electrolytic solution 30 is prepared. The electrolytic solution 30 is not particularly limited as long as it is a solution that can realize electrolytic polishing of the metal pipe 10′, but for example, an aqueous phosphoric acid solution obtained by diluting phosphoric acid with water is used.

[0031] A pair of electrodes 34, 34 serving as cathodes facing each other are inserted into the electrolytic cell 32. The electrodes 34, 34 are each made of a conductive metal. At least a portion of each of the electrodes 34, 34 is immersed in the electrolytic solution 30. The projected area of ​​the portion of each of the electrodes 34, 34 immersed in the electrolytic solution 30 in the facing direction is equal to or larger than an electrolytic polishing region 38 (described below) of the metal pipe 10′ in a side view. Cathode-side wiring 36 is connected to each electrode 34. One end of the cathode-side wiring 36 is electrically connected to the electrode 34, which serves as the cathode for electrolysis, and the other end is electrically connected to a power supply device (not shown).

[0032] As shown in FIG. 4A, the metal pipe 10' is placed over the opening of the electrolytic bath 32. Then, as shown in FIG. 4B, the metal pipe 10' and the electrolytic bath 32 are brought close to each other, and the tip of the metal pipe 10' is immersed in the electrolytic solution 30 in the electrolytic bath 32. Then, by passing current between the metal pipe 10' immersed in the electrolytic solution 30 and the electrodes 34, 34, an electrolytic reaction occurs in the metal pipe 10', with the metal pipe 10' serving as the anode and the electrodes 34, 34 serving as cathodes. As a result, the portion of the metal pipe 10' immersed in the electrolytic solution 30 dissolves from the outer periphery, reducing its outer diameter. During the electropolishing process, the two electrodes 34, 34 are arranged to sandwich the metal pipe 10' at a predetermined radial distance. The two electrodes 34, 34 are arranged independently of each other in the circumferential direction of the metal pipe 10'.

[0033] 4B and 4C, during the electrolytic polishing process, the metal pipe 10' and the electrolytic cell 32 are moved relatively in the axial direction of the metal pipe 10' (the up-and-down direction in FIG. 4B) to change the area of ​​the metal pipe 10' immersed in the electrolytic solution 30. This makes it possible to vary the amount of dissolution of the metal pipe 10' due to electrolytic polishing in the axial direction, thereby changing the outer diameter of the metal pipe 10' in the axial direction.

[0034] Specifically, for example, by gradually immersing the metal pipe 10' in the electrolyte 30 up to the base end, the time spent immersed in the electrolyte 30 in the electropolishing region 38 of the metal pipe 10' (the length region where the conical portion 24 of the conical hollow needle 10 is formed) can be gradually increased from the base end to the tip. As a result, in the electropolishing region 38 of the metal pipe 10', the tip side, which is immersed in the electrolyte 30 for a relatively long time, dissolves more due to electrolysis than the base end side, which is immersed in the electrolyte 30 for a relatively short time. Therefore, the outer peripheral surface 24' of the electropolishing region 38 of the metal pipe 10' is formed into a tapered shape tapering from the base end to the tip by electropolishing. As a result, the outer peripheral surface 24' of the electropolishing region 38 of the metal pipe 10' becomes the conical portion 24 formed on the electropolished surface after electropolishing. The electrolytic polishing region 38 is a length region of the metal pipe 10′ that is immersed in the electrolytic solution 30 during the electrolytic polishing process, and is the length region from the tip of the metal pipe 10′ to the liquid surface of the electrolytic solution 30 in Figure 4C, which shows the state in which the immersion length of the metal pipe 10′ in the electrolytic solution 30 is at its maximum.

[0035] In this embodiment, the metal pipe 10' and the electrodes 34, 34 are moved relative to each other during the process from the start to the end of electrolytic polishing to change the opposing direction of the metal pipe 10' and the electrodes 34, 34. As a result, the electrodes 34, 34 are disposed at three or more different positions in the circumferential direction of the metal pipe 10' during the electrolytic polishing process.

[0036] Specifically, for example, as shown in FIG. 5A, the first electropolishing process is first performed in a first arrangement in which the electrodes 34, 34 are arranged opposite each other in a first direction 40 of the metal pipe 10'. At this time, the amount of dissolution is greater on both sides of the first direction 40, which is the opposing direction of the electrodes 34, 34, than on both sides of the second direction 42, which is perpendicular to the first direction 40. Therefore, the width dimension W1 in the first direction 40 of the outer peripheral surface 24' of the electropolished region 38 of the metal pipe 10' (shown by the two-dot chain line in FIG. 5A) is smaller than the width dimension W2 in the second direction 42. After the first electropolishing process is completed, the metal pipe 10' has a circularity (|W2-W1|) of the outer peripheral surface 24' of the electropolished region 38 of, for example, about 0.0055 mm. After the first electropolishing process is completed, the metal pipe 10' has a wall thickness in the electropolished region 38 that is thinner in the first direction 40 than in the second direction 42.

[0037] After the first electropolishing step is completed, the metal pipe 10' is rotated 90 degrees in the circumferential direction, or the electrodes 34, 34 are moved 90 degrees in the circumferential direction around the metal pipe 10', so that the electrodes 34, 34 are positioned opposite each other in the second direction 42 of the metal pipe 10', as shown in FIG. 5B . Then, the second electropolishing step is performed in the second arrangement in which the metal pipe 10' and the electrodes 34, 34 are opposed in the second direction 42. In the second electropolishing step, the amount of dissolution of the metal pipe 10' is greater on both sides of the second direction 42 than on both sides of the first direction 40. The metal pipe 10', which has a thin wall and a small diameter in the first direction 40 and a thick wall and a large diameter in the second direction 42 due to electropolishing in the first arrangement, is processed into a shape closer to a perfect circle in the outer peripheral surface 24' of the electropolishing region 38 by electropolishing in the second arrangement, as shown by the two-dot chain line in FIG. 5B . That is, in the metal pipe 10′ for which the second electropolishing step has been completed, the outer peripheral surface 24′ (indicated by the two-dot chain line in FIG. 5B ) of the electropolishing region 38 has a width dimension W1′ in the first direction 40 that is approximately the same as a width dimension W2′ in the second direction 42. In the metal pipe 10′ for which the second electropolishing step has been completed, the wall thickness in the electropolishing region 38 is approximately the same in the first direction 40 and the second direction 42.

[0038] The first electropolishing step and the second electropolishing step can be performed discontinuously, for example, by changing the arrangement of the metal pipe 10' and the electrodes 34, 34 from the first arrangement to the second arrangement while stopping the current flow, and then restarting the electropolishing by turning on the current again. Alternatively, the first electropolishing step and the second electropolishing step can be performed continuously by changing the arrangement from the first arrangement to the second arrangement while performing the electropolishing. The time required for the first electropolishing step and the time required for the second electropolishing step may be different from each other or may be the same.

[0039] In this embodiment, during the electropolishing process, the metal pipe 10' and the electrodes 34, 34 are moved (relatively rotated) relative to each other, thereby changing the position of the cathode electrode 34 at four different positions in the circumferential direction of the metal pipe 10' relative to the outer peripheral surface 20' of the anode metal pipe 10', thereby changing the surface of the metal pipe 10' facing the electrode 34. This reduces the difference in dissolution rate between the first direction 40 and the second direction 42 of the metal pipe 10', thereby preventing flattening of the outer peripheral surface 24' of the electropolishing region 38 of the metal pipe 10' and enabling the outer peripheral surface 24' of the metal pipe 10' to be electropolished into a shape closer to a perfect circle. In other words, upon completion of the second electropolishing process, the circularity (|W2'-W1'|) of the conical portion 24 becomes smaller than the value (e.g., 0.0055 mm) at the completion of the first electropolishing process. In the metal pipe 10' in which the electrolytic polishing process including the first electrolytic polishing process and the second electrolytic polishing process has been completed, the circularity (|W2'-W1'|) of the conical portion 24, which is the outer peripheral surface 24' of the electrolytic polishing region 38, is preferably in the range of 0 to 0.0015 mm, and a needle closer to a perfect circle than conventional needles can be manufactured.

[0040] The distal and proximal outer diameters of the conical portion 24 are set, for example, so that the difference in gauge dimension specified in ISO 9626 is 1, with the distal outer diameter being smaller than the proximal outer diameter. Specifically, for example, if the proximal end of the conical portion 24 has an outer diameter dimension equivalent to 32 gauge in ISO 9626, the distal end of the conical portion 24 has an outer diameter dimension equivalent to 33 gauge in ISO 9626. The gauge dimension of the outer diameter of the metal pipe 10' is approximately the same as the gauge dimension of the proximal outer diameter of the conical portion 24. However, the outer and inner diameter dimensions of the conical hollow needle 10 and the outer and inner diameter dimensions of the metal pipe 10' do not necessarily have to be set in accordance with the ISO 9626 standard (gauge dimension). The present invention is also applicable to conical hollow needles thinner than 33 gauge and conical hollow needles thicker than 32 gauge. It should be noted that ISO9626 is a standard relating to the diameter dimensions of needles (tubes) with a fixed outer diameter, and does not cover all the outer diameter dimensions of tapered cylindrical surfaces such as the conical portion 24 of the conical hollow needle 10. However, the diameter dimensions at specific positions have been explained using the gauge dimensions specified in ISO9626.

[0041] Because the inner circumferential surface 18' of the metal pipe 10' does not face the electrodes 34, 34, changes in shape due to electrolysis are suppressed compared to the outer circumferential surface 24'. Therefore, the inner circumferential surface 18' of the metal pipe 10' after electropolishing, i.e., the inner circumferential surface 18 of the conical hollow needle 10, maintains a cross-sectional shape that is close to a perfect circle. Furthermore, the inner diameter of the conical hollow needle 10 is approximately the same as the inner diameter of the metal pipe 10' before electropolishing.

[0042] The metal pipe 10' with the conical portion 24 formed by electrolytic polishing is removed from the electrolytic bath 32, and then the tip is cut or otherwise formed to form the cutting surface 12 and the needle tip 14, thereby forming the conical hollow needle 10. If burrs on the cutting surface 12 formed by cutting or otherwise become a problem, a shot blasting process or the like may be performed to remove the burrs by hitting small glass or metal balls against the cutting surface.

[0043] According to this embodiment, when the conical portion 24 of the conical hollow needle 10 is formed by electropolishing, the electrode 34 is positioned relative to the metal pipe 10' at three or more positions in the circumferential direction of the metal pipe 10'. This allows for three or more circumferentially facing portions of the metal pipe 10' where electrolysis of the metal pipe 10' efficiently proceeds. Therefore, compared to when the metal pipe 10' and the electrode 34 face each other in only one or two directions, the outer circumferential surface 20' of the metal pipe 10' can be electropolished entirely in the circumferential direction to reduce its diameter. As a result, the conical hollow needle 10 has a conical portion 24 with a cross-sectional shape that is closer to a perfect circle. This reduces the diameter all around, effectively reducing pain during puncture, and the circular cross-section provides excellent strength when an external force is applied.

[0044] In this embodiment, in the electrolytic polishing process, the electrodes 34 are disposed at four locations around the circumference of the metal pipe 10' by rotating the metal pipe 10' and the electrodes 34 relative to each other. Therefore, with fewer than three electrodes 34, 34, it is possible to effectively reduce variations in the electrolytic action in the circumference direction.

[0045] In particular, the two opposing electrodes 34, 34 are arranged so that the electrodes 34, 34 face each other in a first direction 40 in the first electrolytic polishing step, and the electrodes 34, 34 face each other in a second direction 42 in the second electrolytic polishing step. Therefore, both sides in the second direction 42, where the amount of dissolution is small in the first electrolytic polishing step, can be efficiently dissolved in the second electrolytic polishing step, and the difference in outer diameter can be suppressed in two orthogonal directions in which the difference in outer diameter of the metal pipe 10' is likely to be large.

[0046] As for the electropolishing step in the method for manufacturing a conical hollow needle, the aspect shown in Figure 5 is the most suitable among the aspects disclosed in this specification, but other aspects shown in Figures 6 and 7 may also be adopted. That is, Figure 6 is a diagram illustrating the electropolishing step in the method for manufacturing a conical hollow needle as a second embodiment of the present invention. In the following description, components and parts that are substantially the same as those in the first embodiment are given the same reference numerals in the figure, and description thereof will be omitted. Furthermore, since the conical hollow needles manufactured according to the second and third embodiments are substantially the same as the conical hollow needle 10 shown in the first embodiment, description thereof will be omitted.

[0047] In the electrolytic polishing apparatus 50 shown in FIG. 6, three electrodes 52, 52, 52 serving as cathodes are arranged around a metal pipe 10', which is the base of the conical hollow needles. The three electrodes 52, 52, 52 are inclined at 120 degrees from one another, arranged at approximately equal intervals in the circumferential direction of the metal pipe 10', and arranged to surround the periphery of the metal pipe 10'. Each electrode 52 extends in a tangential direction to the outer circumferential edge of the cross section of the metal pipe 10' and extends approximately perpendicular to the radial direction of the metal pipe 10', which is the direction in which the metal pipe 10' and the electrodes 52 face each other. The three electrodes 52, 52, 52 are arranged at a substantially constant distance from each other to the outer circumferential surface 20' of the metal pipe 10'.

[0048] In this way, by arranging the three electrodes 52, 52, 52 around the metal pipe 10', the three electrodes 52, 52, 52 are simultaneously arranged at three mutually different positions in the circumferential direction of the metal pipe 10' and simultaneously face the outer circumferential surface 20' of the metal pipe 10' at three positions. In electrolytic polishing, the three electrodes 52, 52, 52 are all cathodes, and the metal pipe 10' is the anode. In the electrolytic polishing apparatus 50 of this embodiment, during the electrolytic polishing process, the three electrodes 52, 52, 52 are fixedly arranged without moving relative to the outer circumferential surface 20' of the metal pipe 10', and the arrangement of the three electrodes 52, 52, 52 with respect to the outer circumferential surface 20' of the metal pipe 10' does not change.

[0049] The outer circumferential portion of the metal pipe 10' can be electrolyzed to reduce its diameter by passing a current between the metal pipe 10' and each electrode 52. As in the first embodiment, in the electrolytic polishing step, the metal pipe 10' and the electrolytic cell 32 are moved relatively in the axial direction of the metal pipe 10' (the direction perpendicular to the plane of the paper in FIG. 6 ), thereby forming the outer circumferential surface 24' of the electrolytic polishing region 38 of the metal pipe 10' into a tapered conical portion 24.

[0050] According to this embodiment, the three electrodes 52, 52, 52 are simultaneously arranged at three positions in the circumferential direction of the metal pipe 10', and therefore variation in the efficiency of electropolishing in the circumferential direction of the metal pipe 10' is reduced without rotating the metal pipe 10' relatively to the electrodes 52, 52, 52. Therefore, a mechanism for rotating the metal pipe 10' relatively to the electrodes 52, 52, 52 is not required, and a conical portion with a cross-sectional shape that is close to a perfect circle can be realized using a simple manufacturing device.

[0051] Although the present embodiment shows an example in which three electrodes 52 are provided, four or more electrodes may be provided at the same time, and for example, providing more electrodes may improve the circularity of the outer peripheral shape of the conical portion. Furthermore, each electrode 52 is not necessarily limited to a flat plate shape, and may be curved or bent along the circumferential direction of the metal pipe 10'.

[0052] FIG. 7 is a diagram illustrating the electropolishing step in the manufacturing method of a conical hollow needle according to a third embodiment of the present invention. In the electropolishing apparatus 60 shown in FIG. 7, a cathode electrode 62 is cylindrical and continuously surrounds the entire circumference of a metal pipe 10' from which the conical hollow needle is made. The electrode 62 is arranged concentrically with the metal pipe 10', curved and extending in the circumferential direction of the metal pipe 10', and simultaneously faces the outer peripheral surface 20' of the metal pipe 10' over the entire circumference. It is desirable that the radial distance between the outer peripheral surface 20' of the metal pipe 10' and the inner peripheral surface of the electrode 62 be approximately constant over the entire circumference.

[0053] According to this embodiment, the metal pipe 10' and the electrode 62 are opposed simultaneously at a substantially constant distance over the entire circumference, so that the metal pipe 10' is electropolished substantially uniformly over the entire circumference. Therefore, the circumferential variation in the outer diameter of the conical portion of the conical hollow needle is further reduced, and a conical portion with a cross-sectional shape that is close to a perfect circle can be obtained by electropolishing.

[0054] It is also conceivable to use the electrolytic cell 32 itself as an electrode, but this would have drawbacks such as difficulty in setting a sufficiently small distance between the electrolytic cell 32 and the metal pipe 10', and the shape of the electrolytic cell 32 being limited to a circular shape, making it difficult to realize an electrolytic cell 32 that can process, for example, a plurality of metal pipes 10', and therefore is not practical.

[0055] 8 is a diagram illustrating the electropolishing step in the method for manufacturing a conical hollow needle according to a fourth embodiment of the present invention. This embodiment is based on the first embodiment and illustrates a different aspect of the multiple electrodes 34 spaced apart on the outer periphery of the metal pipe 10' and the control of current flow to these multiple electrodes 34. The vertical cross-sectional view is, for example, as in the first embodiment, as shown in FIGS. 4A to 4C, in which the electrodes 34 are spaced apart on the outer periphery of the metal pipe 10' and extend substantially parallel to the metal pipe 10'.

[0056] That is, in this embodiment, the electrode 34 serving as a cathode arranged at a distance on the outer periphery of the metal pipe 10' is composed of two pairs of electrodes 34a, 34a and electrodes 34b, 34b arranged opposite each other across the metal pipe 10' in two radial directions that are orthogonal to each other. In other words, a total of four electrodes 34 are arranged at a distance from each other in the circumferential direction on the outer periphery of the metal pipe 10' so as to face different positions in the circumferential direction relative to the outer periphery of the metal pipe 10'. Note that in this embodiment, since multiple metal pipes 10' are arranged at predetermined intervals in the longitudinal electrolytic cell 32, it is possible for adjacent metal pipes 10' to share the electrodes 34a, 34b arranged between them, thereby reducing the total number of electrodes 34a, 34b relative to the number of metal pipes 10'.

[0057] In this embodiment, two pairs of electrodes 34a, 34a and 34b, 34b serving as cathodes are arranged around the metal pipe 10' in a spaced-apart, opposing relationship. For example, by alternately switching and controlling the energization state of one pair of electrodes 34a, 34a and the other pair of electrodes 34b, 34b with the metal pipe 10' using a timer switch or the like, the electropolishing region of the metal pipe 10' is sequentially switched between the surface region facing one pair of electrodes 34a, 34a and the surface region facing the other pair of electrodes 34b, 34b. As a result, the outer peripheral surface of the metal pipe 10' is electropolished in two mutually orthogonal directions. Compared to the case of simply electropolishing using a pair of electrodes as in the first embodiment, for example, it is possible to easily perform electropolishing with high circularity on the metal pipe 10' without rotating the metal pipe 10' around its central axis relative to the electrodes. In addition, taking into account the difference in the amount of electrolytic polishing in the circumferential direction of the metal pipe 10', it is possible to improve the roundness by controlling the current flow time and applied voltage between one pair of electrodes 34a, 34a and the other pair of electrodes 34b, 34b of the metal pipe 10' by making them different.

[0058] 9 is a diagram illustrating the electrolytic polishing step in the manufacturing method of a conical hollow needle according to a fifth embodiment of the present invention. The electrolytic polishing apparatus 70 shown schematically in FIG. 9 has a structure in which electrode devices 72 each equipped with an electrode 74 as a cathode are provided on each of the wall portions of the electrolytic bath 32 on both sides of the metal pipe 10'. In the electrode device 72, a plurality of electrodes 74 are arranged in the longitudinal direction of each wall portion of the electrolytic bath 32, sandwiching a non-conductive spacer portion 76 therebetween.

[0059] As a result, the multiple electrodes 74 in each electrode device 72 are spaced apart from the surface of the metal pipe 10' (the distance in the general direction of the metal pipe 10') by different distances. For example, the distance from the electrode 74 closest to the metal pipe 10' is indicated by Da in the figure, and the distance from the electrode 74 farthest from the metal pipe 10' is indicated by Db in the figure. Furthermore, the opposing positions of the multiple electrodes 74 in the distance direction on the surface of the metal pipe 10' are different from each other in the circumferential direction of the metal pipe 10'.

[0060] Furthermore, the current between each of the plurality of electrodes 74 and the metal pipe 10' is passed by controlling the voltage and / or current supplied from the power supply 78 for each electrode 74 with the controller 80. Specifically, for example, for each of the plurality of electrodes 74, the current passage time is controlled to be shorter or the applied voltage is controlled to be lower for an electrode that is closer to the metal pipe 10' than for an electrode that is farther away from the metal pipe 10', thereby making it possible to electropolish the outer surface of the metal pipe 10' over the entire circumference in a time-efficient manner and with good roundness.

[0061] FIG. 10 is a diagram illustrating the electropolishing step in the method for manufacturing a conical hollow needle according to a sixth embodiment of the present invention. This embodiment is based on the first embodiment and shows a variation of FIG. 4C . The horizontal cross-sectional view may be, for example, as shown in FIGS. 5A and 5B , similar to the first embodiment. That is, in this embodiment, the cathode electrode 34, spaced apart from the outer periphery of the metal pipe 10′, is divided in the depth direction (the length direction of the metal pipe 10′) of the electrolytic bath 32 into which the tip of the metal pipe 10′ is inserted. Multiple electrodes 34 are arranged in the depth direction of the electrolytic bath 32, sandwiching non-conductive spacers between them. The opposing positions of the multiple electrodes 34 on the surface of the metal pipe 10′ in the separation direction are different from each other along the length of the metal pipe 10′.

[0062] Furthermore, the current flow between each of the electrodes 34 and the metal pipe 10' is controlled by a controller to control the voltage and / or current supplied from the power supply for each electrode 34, as with the electrodes 74 in the fifth embodiment. Specifically, for example, the current flow time of the electrodes 34 closer to the upper opening of the electrolytic cell 32 can be controlled to be shorter or the applied voltage can be controlled to be lower than that of the electrodes closer to the bottom of the electrolytic cell 32, thereby electropolishing the outer surface of the metal pipe 10' so that it tapers downward. In such electropolishing, it is also possible to perform the electropolishing process by immersing the entire length of the electropolishing region 24' of the metal pipe 10' in the electrolytic solution 30 from the beginning.

[0063] Although the embodiments of the present invention have been described in detail above, the present invention is not limited by the specific description. For example, only one electrode 34 may be used. For example, in the electropolishing process, the metal pipe 10' may be rotated four times, each time by 90 degrees, to position the electrode 34 at four circumferential positions relative to the metal pipe 10'. When rotating the metal pipe 10' and the electrode 34 relative to each other, the amount of relative rotation between the metal pipe 10' and the electrode 34 is not particularly limited. However, since the electrode 34 must be positioned at three or more circumferential positions relative to the metal pipe 10', a rotation angle other than 180 degrees or a multiple thereof is desirable. In the first embodiment, the metal pipe is rotated stepwise by a predetermined angle relative to the electrode. However, for example, the metal pipe may be rotated continuously circumferentially while electropolishing is being performed.

[0064] In the first embodiment, the electrolytic polishing step is exemplified by gradually increasing the length of time the metal pipe 10' is immersed in the electrolyte 30, thereby making the time the distal end is immersed in the electrolyte 30 longer than the proximal end. However, for example, the length of time the metal pipe 10' is immersed in the electrolyte 30 may be gradually reduced from a state in which the entire electrolytic polishing region 38 of the metal pipe 10' is immersed in the electrolyte 30, thereby making the time the distal end is immersed in the electrolyte 30 longer than the proximal end. Furthermore, the step of gradually increasing the length of time the metal pipe 10' is immersed in the electrolyte 30 and the step of gradually decreasing the length of time the metal pipe 10' is immersed in the electrolyte 30 may be performed in order, or these steps may be repeated alternately.

[0065] Furthermore, by changing the distance between the metal pipe 10′ and the electrode 34, for example, so that it increases from the tip to the base end of the metal pipe 10′, the amount of dissolution of the metal pipe 10′ in the axial direction can be changed by performing the electrolytic polishing process for the same period of time.

[0066] In the above embodiment, an example has been shown in which the immersion length of the metal pipe 10′ in the electrolytic solution 30 is changed by moving the metal pipe 10′ and the electrolytic cell 32 relative to each other in the axial direction of the metal pipe 10′. However, for example, the immersion length of the metal pipe 10′ in the electrolytic solution 30 can also be changed by raising / lowering the liquid level of the electrolytic solution 30 in the electrolytic cell 32 without moving the metal pipe 10′ and the electrolytic cell 32 relative to each other in the axial direction of the metal pipe 10′.

[0067] The conical portion 24, which is the electrolytically polished surface, only needs to constitute a part of the outer peripheral surface 20 of the conical hollow needle 10; the entire outer peripheral surface 20 may be constituted by the conical portion 24, or only the tip portion of the outer peripheral surface 20 may be constituted by the conical portion 24, as in the above embodiment.

[0068] On the outer peripheral surface 20 of the conical hollow needle 10, only the conical portion 24 does not necessarily have to be an electrolytically polished surface; for example, the cylindrical portion 22 can also be smoothed by electrolytic polishing. Therefore, the electrolytically polished region 38 of the metal pipe 10' is not necessarily limited to the region where the conical portion 24 is formed.

[0069] In the above embodiment, for ease of understanding, the case of electropolishing one metal pipe 10' has been described. However, for example, it is also possible to simultaneously electropolish multiple metal pipes 10'. In this case, multiple metal pipes 10' may be simultaneously electropolished in one electrolytic bath 32, or multiple metal pipes 10' may be simultaneously electropolished in multiple electrolytic baths 32. For example, two longitudinal plate-shaped electrodes 34, 34 may be arranged facing each other at a predetermined distance in one electrolytic bath 32, and multiple metal pipes 10' may be arranged between the two electrodes 34, 34, with parallel opposing surfaces, at a predetermined distance in the longitudinal direction of the electrodes 34. This allows multiple metal pipes 10' to be simultaneously electropolished between the two electrodes 34, 34. Then, by rotating the multiple pipes 10' around their respective central axes at predetermined time intervals or continuously, it becomes possible to change the facing direction of the electrodes 34 relative to each metal pipe 10' in four or more different directions while the two electrodes 34, 34 remain fixed. In this way, multiple needles with high circularity can be efficiently manufactured.

[0070] Furthermore, in the method of the present invention, the facing direction of the cathode relative to the outer peripheral surface of the hollow needle refers to the shortest facing direction between the hollow needle and the cathode. Therefore, if the cathode is flat, even if the cathode extends circumferentially around the hollow needle, it only provides a single facing direction. On the other hand, if the cathode is curved with a curved facing surface whose center of curvature is the central axis of the hollow needle, even a single cathode can provide facing directions at three or more different positions around the hollow needle, such as the single cylindrical cathode surrounding the hollow needle shown in the third embodiment. However, in the present invention, it is desirable for a cathode that provides facing directions in the radial direction of the hollow needle at three or more different positions to provide three or more facing directions at equal intervals (equal angles) around the hollow needle for equal periods of time during the electropolishing process.

[0071] In the above embodiment, a conical hollow needle 10 having a needle tip 14 at only one end has been described, but the present invention can also be applied to a double-ended needle having needle tips at both ends, for example. In this case, for example, the conical portion 24 may be formed only at the tip portion, which is the side that is inserted into the patient, or at each end. Furthermore, a conical hollow needle 10 having a needle tip 14 at only the tip may be provided with a needle hub or the like at the base end.

[0072] REFERENCE SIGNS LIST 10 Conical hollow needle (first embodiment) 10' Metal pipe (hollow needle) 12 Blade surface 14 Needle tip 16 Lumen (lumen of conical hollow needle) 16' Lumen (lumen of hollow needle) 18 Inner peripheral surface (inner peripheral surface of conical hollow needle) 18' Inner peripheral surface (inner peripheral surface of hollow needle) 20 Outer peripheral surface (outer peripheral surface of conical hollow needle) 20' Outer peripheral surface (outer peripheral surface of hollow needle) 22 Cylindrical portion 24 Conical portion 24' Outer peripheral surface (outer peripheral surface of electrolytic polishing area) 26 Electrolytic polishing device 28 Anode side wiring 30 Electrolyte 32 Electrolytic cell 34 Electrode (cathode) 36 Cathode side wiring 38 Electrolytic polishing area 40 First direction 42 Second direction 50 Electrolytic polishing device (second embodiment) 52 Electrode (cathode) 60 Electrolytic polishing apparatus (third embodiment) 62 Electrode (cathode) 70 Electrolytic polishing apparatus (fifth embodiment) 72 Electrode device 74 Electrode (cathode) 76 Spacer portion 78 Power supply 80 Controller

Claims

1. A method for manufacturing a conical hollow needle having a tapered conical portion on its outer periphery, in which a straight hollow needle is immersed in an electrolyte to electrolytically polish the outer periphery into a conical shape, and during the process from the start to the end of the electrolytic polishing, a pair of cathodes are arranged to sandwich the hollow needle, which serves as an anode, at a predetermined distance in the radial direction, and the hollow needle is rotated around the needle axis to change the surface of the hollow needle facing the cathode.

2. A method for manufacturing a conical hollow needle having a tapered conical portion on the outer periphery, in which a straight hollow needle is immersed in an electrolyte to electrolytically polish the outer periphery into a conical shape, and a cathode that radially faces the outer periphery of the hollow needle (which serves as an anode) is positioned at three or more different positions around the hollow needle during the entire process from the start to the end of the electrolytic polishing.

3. A method for manufacturing a conical hollow needle as described in claim 2, wherein a plurality of the cathodes are arranged independently of one another in the circumferential direction of the hollow needle, and the position of the cathodes is changed relative to the hollow needle so that they are in different positions in the circumferential direction of the hollow needle during the process from the start to the end of electrolytic polishing.

4. A method for manufacturing a conical hollow needle according to claim 2, wherein the cathode is disposed so as to surround the hollow needle, and the cathode simultaneously faces the hollow needle at three or more different positions in the circumferential direction during the process from the start to the end of electrolytic polishing.

5. A method for manufacturing a conical hollow needle according to any one of claims 2 to 4, wherein the cathode extends in a curved manner in the circumferential direction of the hollow needle.

6. The method for manufacturing a conical hollow needle according to any one of claims 1 to 5, wherein the conical portion has a circularity of 0 to 0.0015 mm formed by electrolytic polishing.

7. A method for manufacturing a conical hollow needle having a tapered conical portion on its outer periphery, comprising: immersing a straight hollow needle in an electrolyte to electrolytically polish the outer periphery into a conical shape; arranging a plurality of cathodes facing and spaced apart from the outer periphery of the hollow needle, which serves as an anode; and controlling the state of current flow between the hollow needle and the plurality of cathodes, thereby adjusting the strength of electrolytic polishing of the hollow needle by each of the cathodes.