WO2023150289A1

WO2023150289A1 - Method and apparatus for making needles

Info

Publication number: WO2023150289A1
Application number: PCT/US2023/012304
Authority: WO
Inventors: Emanoel Rizea; Lee BURGESS
Original assignee: Interplex Industries, Inc.
Priority date: 2022-02-05
Filing date: 2023-02-03
Publication date: 2023-08-10

Abstract

A method of forming needles in which a length of metal is stamped to form a configured strip having nascent needles at least partially disposed in windows. The configured strip is moved over a plurality of pushers such that the pushers are aligned with, and disposed below, the windows and the nascent needles, respectively. The pushers are moved upward into the windows to bend the nascent needles so the bodies of the nascent needles slope upward. A grinding wheel is rotated and lowered to interact with the second end portions of the nascent needles to remove material from the second end portions to form tapered tips in the second end portions. The grinding wheel is then raised and the pushers are moved downward to be disposed below the windows, thereby allowing the nascent needles to move back toward their original unbent configurations.

Description

METHOD AND APPARATUS FOR MAKING NEEDLES

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No.: 63/307,083 filed on 5 February 2022, which is herein incorporated by reference.

TECHNICAL FIELD

[0002] This disclosure relates generally to methods and apparatus for making needles and more particularly to methods and apparatus for making needles having tapered tips.

BACKGROUND

[0003] Conventionally, a needle is formed from a length of metal cut from a source. The length of metal is deformed to have a desired cross-sectional configuration and then is processed to have a tapered tip at one end. The processing conventionally includes grinding to remove material to form the tip. One of the main issues encountered with grinding is the considerable amount of time it takes to grind a tip since each needle is typically ground individually.

[0004] Based on the foregoing, it would be desirable to have a method and apparatus for forming needles in a fast and efficient manner. The present disclosure relates to such a method and apparatus.

SUMMARY

[0005] In accordance with the disclosure, a method is provided for forming needles. In accordance with the method, a length of metal is stamped to form a configured strip having nascent needles and first and second ribbons connected together by columns to form a plurality of windows. The nascent needles each have a body disposed between first and second end portions. The first end portion is secured to the first ribbon and the second end portion has a free end. The nascent needles are at least partially disposed in the windows, respectively. The configured strip is moved over a plurality of pushers such that the pushers are aligned with, and disposed below, the windows and the nascent needles. The pushers are moved upward into the windows to bend the nascent needles so the bodies of the nascent needles slope upward. A grinding wheel is rotated and lowered to interact with the second end portions of the nascent needles to remove material from the second end portions to form tapered tips in the second end portions. The grinding wheel is raised and then the pushers are moved downward to be disposed below the windows, thereby allowing the nascent needles to move back toward their original unbent configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

[0007] Fig. 1 shows a perspective view of a needle formed by a method of the present disclosure;

[0008] Fig. 2 shows a plan view of a configured strip formed in a step of the method, the configured strip including nascent needles;

[0009] Fig. 3 shows a close-up plan view of a portion of the configured strip shown in Fig. 2;

[0010] Fig. 4 shows a side elevational view of the portion of the configured strip shown in Fig. 3;

[0011] Fig. 5 shows a perspective view of a grinding station wherein the configured strip is processed to grind the nascent needles to form tapered tips in the nascent needles; [0012] Fig. 6 shows a front perspective view of a grinding machine in the grinding station;

[0013] Fig. 7 shows a perspective view of a slab spaced above a ramp structure of the grinding machine shown in Fig. 6;

[0014] Fig. 8 shows a perspective view of a pusher of the ramp structure shown in Fig. 7; [0015] Fig. 9 shows a front, top perspective view of a top portion of the grinding machine of Fig. 6 showing a portion of the slab with first and second clamping structures mounted thereto;

[0016] Fig. 10 shows a close-up, rear perspective view of the grinding machine of Fig. 6 showing a pair of nascent needles bent upward by pushers;

[0017] Fig. 11 shows a close-up, front perspective view of a portion of the ramp structure, with all of the pushers removed, except for one pusher, which is spaced above the ramp structure;

[0018] Fig. 12 shows a schematic front view of a top portion of the grinding machine, wherein the configured strip of Fig. 2 is positioned over the pushers of the ramp structure when the ramp structure is in a deactivated position;

[0019] Fig. 13 shows a schematic front view of the top portion of the grinding machine wherein the pushers extend through the configured strip of Fig. 2 and bend the nascent needles upward when the ramp structure is in an activated position; and

[0020] Fig. 14 shows a schematic front view of the top portion of the grinding machine when the ramp structure is in the activated position and the bent nascent needles interact with a grinding wheel.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0021] It should be noted that in the detailed description that follows, identical components have the same reference numerals, regardless of whether they are shown in different embodiments of the present disclosure. It should also be noted that for purposes of clarity and conciseness, the drawings may not necessarily be to scale and certain features of the disclosure may be shown in somewhat schematic form.

[0022] Spatially relative terms, such as "top", "bottom", "lower", "above", "upper", and the like, are used herein merely for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as they are illustrated in (a) drawing figure(s) being referred to. It will be understood that the spatially relative terms are not meant to be limiting and are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. [0023] A method is provided to form a needle, such as a suture needle, a hypodermic needle, a biopsy needle or a specialty needle. The needle (such as the needle 10 shown in Fig. 1) may have a length of from about 0.5 inches to about 3.5 inches and may have a diameter, measured in gauges, ranging from about 07 gauge to about 33 gauge. The needle 10 may be formed from metal, such as stainless steel. [0024] The needle 10 has a tip 12 and a body 14. If the needle 10 is a suture needle, the needle may further have an eye through which suture material is threaded. The body 14 may have an arcuate cross-section and be straight or curved. If curved, the body 14 may be 1/4, 1/2, 3/8 or 1/3 of a circle. The curve allows a surgeon to see where the tip is at all times. The cross-section of the body 14 may be closed, i.e., cylindrical with an internal lumen, or may be open, i.e., channel-shaped. With the latter type of cross-section, the channel may be U-shaped and may have a shallow, medium, or deep configuration. At the tip 12, the opening in the lumen or channel is diagonal and the body 14 presents a beveled face with sharp edges.

[0025] Referring now to Fig. 2-4, the needle 10 is formed with a plurality of other needles from an extended length of metal, such as stainless steel. The length of metal may be wound on, and then dispensed from, a first reel. At a first station, the length of metal is dispensed from the first reel and stamped in a die to form a first configured strip 20 having a needle piece 22 and a carrier piece 24 that are interconnected. The needle piece 22 includes a plurality of nascent needles 26 secured at first end portions 25 to a narrow first header ribbon 28 (shown best in Fig. 10). The carrier piece 24 includes a narrow second header ribbon 32 that is secured to the first header ribbon 28 by connecting columns 34. The first and second header ribbons 28, 32 have holes 36 formed therein, which are used, inter alia, for moving the configured strip 20 through the processing line(s).

[0026] The nascent needles 26 are aligned with, and at least partially disposed in, windows 40 formed in the configured strip 20. As shown, each nascent needle 26 has a body 14 with a U-shaped cross section. In contrast, the first end portion 25 of each nascent needle 26 is flat (as shown in Fig. 10) and, thus, is more compliant and bendable than the body 14 of the nascent needle 26. A first pair and a second pair of flanges or wings 42 extend from the body 14. In each of the first and second pairs, the wings 42 project from the body 14 in opposing directions. The first pair is spaced from the second pair along the length of the body 14. A second end portion of the body 14 (where the tip is formed) has a free end that is flat and has the same cross-section as the rest of the body 14. Although not shown, the nascent needles 26 may include eyes. [0027] After the configured strip 20 is formed in the first station, the configured strip 20 may be wound onto one or more second reels 46, which is/are then transported to a second station 48, which is shown in Fig. 5. Alternately, the first and second stations may be located adjacent to each other and the configured strip 20 may be conveyed directly to and processed in the second station 48, without being wound on another reel. From the second reel 46 or directly from the first station, the configured strip 20 is advanced through a grinding machine 50, where a grinding process is performed on the configured strip 20 to form the tips 12 of the needles 10.

[0028] The grinding process may be a mechanical grinding process in which an abrasive surface of a rotating grinding wheel is brought into physical contact with the second end portions of the nascent needles 26 to physically (mechanically) remove material and thereby form the tips 12 on the nascent needles 26. Alternately, the grinding process may be an electrochemical grinding process in which an electrically conductive grinding wheel is electrically charged to act as a cathode and the electrically conductive configured strip 20 (including the nascent needles 26) is charged to act as an anode. An electrolytic fluid, such as sodium nitrate, sodium chlorate, sodium hydroxide or sodium carbonate is pumped into the space between the second end portions of the nascent needles 26 and the grinding wheel. The electrolytic fluid causes electrochemical reactions to occur at the surfaces of the second end portions, which oxidizes the surfaces to form oxide films thereon. These oxide films are abrasively removed by the rotating grinding wheel to thereby form the tips 12. Most material is removed from the nascent needles 26 by the electrochemical reactions which occur at the surfaces of the second end portions, indeed, the only time that abrasive grinding occurs is in the removal of the oxide films. The abrasive surface of the grinding wheel in both the mechanical grinding process and the electrochemical grinding process may be formed by abrasive particles of diamond dust, aluminum oxide, boron carbide or silicon carbide.

[0029] When the second reel 46 is utilized, a pay-off apparatus 56 and a take-up apparatus 58 are used in the second station 48. The pay-off apparatus 56 includes the second reel 46. The take-up apparatus 58 includes a third reel 60 that is rotated by a motor to pull the configured strip 20 through the grinding machine 50 and to wind the processed configured strip 20 on the third reel 60. The third reel 60 is rotated in increments, with the amount of incremental rotation being determined by the number of nascent pins 26 that are ground at one time, i.e., the size of a batch of the nascent pins 26 being ground. The duration of the time intervals between the rotational increments is determined by the time it takes to grind a batch of the nascent pins 26. The incremental rotation is controlled by a controller 64 in concert with a controller 66 of the grinding machine 50. More than one third reel 60 may be utilized in the second station 48.

[0030] Referring now also to Figs. 6-11 , the grinding machine 50 includes an outer housing 70 enclosing a slab 72 supported on a base 74 by one or more pedestals 76. The slab 72 includes an elongated slot 78, which is located about midway along the length of the slab 72. A portion of each longitudinal edge of the slab 72 is tapered where the slot 78 aligns with the longitudinal edge. A ramp structure 80 is movably mounted to the pedestals 74, below the slab 72, such as through the use of movable guide rods disposed inside the pedestals 74. The ramp structure 80 has a base 82 with an elongated butte 84 extending therefrom. As best shown in Fig. 11, the butte 84 has a top surface 83 through which a plurality of spaced-apart cavities 85 extend.

[0031] Pushers 86 are disposed in the cavities 85, respectively, and project outwardly therefrom. Each pusher 86 has a sloping top surface 88 with a groove 90 formed therein. The top surface 88 slopes downwardly from an outer edge 91 to an inner edge 92, with the groove 90 extending through both of the outer and inner edges 91 , 92. The pushers 86 may be mounted in the cavities 85 by rods 87 to permit limited movement in the cavities 85. The pushers 86 may be outwardly biased by springs 89 mounted to the rods 87, respectively. This limited mobility provides the pushers 86 with some flexibility to absorb excessive forces applied to the pushers 86. A pair of spacedapart, metal guideposts 94 extend upwardly from side mounts of the butte 84.

[0032] It should be appreciated that in other embodiments, the pushers 86 may not be separate, resiliently movable pieces. Instead, the pushers 86 may be fixed in position and/or may be integrally formed with the butte 84 of the ramp structure 80, i.e., the pushers 86, the ramp structure 80 and the butte 84 may be one single unitary piece. [0033] As best shown in Fig. 9, first and second clamp structures 96, 98 are disposed over, and mounted to, the slab 72. The first clamp structure 96 is positioned to the left of the slot 78, while most of the second clamp structure 98 is positioned to the right of the slot 78; however, a portion of the second clamp structure 98 overhangs the slot 78. A portion of a top surface of the first clamp structure 96 slopes downwardly as it approaches the slot 78. The overhanging portion of the second clamp structure 98 is tapered to form a space between the slot 78 and the second clamp structure 98. The overhanging portion includes a downwardly facing groove, within which a cord 100 of elastomeric material is disposed. The elastomeric material may be Neoprene, silicon or EPDM rubber.

[0034] An actuator 102 is provided to move the ramp structure 80 between an upper, activated position and a lower deactivated position. In the activated position, the base 82 of the ramp structure 80 is pressed against a bottom surface of the slab 72, while in the deactivated position, the base 82 of the ramp structure 80 is spaced below the slab 72. The actuator 102 may utilize an electric solenoid or a pneumatic cylinder (as is shown). The (pneumatic) actuator 102 may include a cylindrical housing 104 having an inner chamber within which a piston is disposed. The piston or the housing 104 may be movable (to move the ramp structure 80) by controlling the flow of fluid to the inner chamber through a pair of ports 106. As shown, the housing 104 is movable and is connected to a lift 108, which is secured to the ramp structure 80. Fluid to the inner chamber may be controlled to move the housing 104 upward to move the ramp structure 80 to the activated position and may be controlled to move the housing 104 downward to move the ramp structure 80 to the deactivated position.

[0035] When the ramp structure 80 is in the activated position, the pushers 86 and the guideposts 94 extend through the slot 78 in the slab 72 and project above the top surface of the slab 72. The pushers 86 are also disposed at a height that is above an inner portion of the top surface of the first clamp structure 96. When the ramp structure 80 is in the deactivated position, the pushers 86 and the guideposts 94 do not project above the top surface of the slab 72. Instead, they are either flush with, or completely disposed below the top surface of the slab 72.

[0036] The grinding process is described in the paragraphs below. The first three steps of the process are schematically shown in Figs. 12-14. A modified version of the pushers (designated 86') are shown being used. A pusher 86' is the same as the pusher 86, except a portion of the pusher 86' has been removed to reduce the amount of plastic used to form the pusher 86'.

[0037] In a first step of the grinding process, the configured strip 20 is disposed over the slot 78 and over the tapered longitudinal edges of the slab 72 when the ramp structure 80 is in the deactivated position. The configured strip 20 is positioned such that the bodies 14 of a first batch of the nascent needles 26 are aligned over the grooves 90 of the pushers 86 and the holes 36 in the configured strip 20 are aligned over the guideposts 94 extending from the butte 84. More specifically, the second end portions of the nascent needles 26 rest against, or are in close proximity to, the top surface of the slab 72, with the bodies 14 of the nascent needles 26 being disposed in close proximity to the grooves 90 in the outer edges 91 of the pushers 86. The distances between the bodies 14 of the nascent needles 26 and the top surfaces 88 of the pushers 86 increase as the top surfaces 88 slope downwardly from the outer edges 91 to the inner edges 92.

[0038] With the configured strip 20 so positioned, a second step of the grinding process is performed. The actuator 102 is actuated to move the ramp structure 80 upward, toward the activated position. As the ramp structure 80 moves upward, the pushers 86 move above the top surface of the slab 72 and increasingly engage the nascent needles 26. More specifically, as the pushers 86 move upward, more and more of the bodies 84 of the nascent needles 26 move into and engage the grooves 90 of the pushers 86, respectively. This engagement and the continued upward movement of the pushers 86 bend major portions of the nascent needles 26 upward in a sloping manner. The nascent needles 26 bend in their compliant first end portions 25 since they are the least rigid portions of the nascent needles 26. In addition to bending the nascent needles 26, the upward movement of the ramp structure 80 moves tapered end portions of the guideposts 94 into holes 36 in the configured strip 20.

[0039] When the ramp structure 80 arrives at the activated position, tapered end portions of the guideposts 94 are disposed in the holes 36 of the configured strip 20, thereby helping to hold the configured strip 20 in place relative to the ramp structure 80. In addition, at least a majority of the body 14 of each of the nascent needles 26 slopes upwardly and is positioned in a groove 90 of an associated pusher 86 such that the inner edge 92 of the pusher 86 is positioned between the first and second pairs of the wings 42 of the nascent needle 26. The cord 100 of the second clamp structure 98 presses against the bodies 14 of the nascent needles 26. Furthermore, the second end portion (including the free second end) of each needle body 14 extends beyond the outer edge 91 of the associated pusher 86 so as to not be supported on the associated pusher 86. In this manner, the second end portions of the nascent needles 26 are exposed and disposed at a height that is above the inner portion of the top surface of the first clamp structure 96.

[0040] With the ramp structure 80 in the activated position, a third step of the grinding process is performed. A rotating grinding wheel 120 is lowered to interact with the second end portions of the nascent needles 26. As described above, the grinding wheel may operate in a mechanical grinding process in which material is only mechanically removed from the second end portions or may operate in an electrochemical grinding process to primarily remove oxide films from the second end portions. The grinding wheel 120 removes material from the second end portions, thereby forming the tips 12 on the nascent needles 26. During the grinding process, the configured strip 20 and the nascent needles 26 are held in place by the guideposts 94 and the second clamp structure 98, with the cord 100 pressing against the bodies 14 of the nascent needles 26.

[0041] After the tips 12 have been formed in the nascent needles 26, a fourth step of the grinding process is performed. The grinding wheel 120 is raised and the ramp structure 80 is moved back downward to the deactivated position. As the ramp structure 80 moves downward, the major portions of the nascent needles 26 also move downward to assume their original unbent shape through shape memory.

[0042] When the ramp structure 80 is back in the deactivated position and the nascent needles 26 are back in their unbent shapes, the configured strip 20 is advanced to move a second batch of nascent needles 26 into alignment over the pushers 86. The advancement of the configured strip 20 is performed by incrementally rotating the third reel 60 under the control of the controllers 64, 66. The foregoing process continues until all of the nascent needles 26 in the configured strip 20 have been mechanically/ electrochemically ground to form their tips 12.

[0043] The size of each batch of nascent needles 26 to be ground is determined by the number of available pushers 86. In the shown embodiment of the grinding machine 50, there are twelve pushers 86 and, thus, each batch consists of twelve nascent needles 26. In other embodiments, a different number of pushers 86 may be provided. [0044] After a batch of nascent needles 26 has been ground to form their tips 12, the batch may be moved into a wash machine 112 through advancement of the configured strip 20 by the take-up apparatus 58. In the wash machine 112, the configured strip 20 with the batch of nascent needles 26 is cleaned of metal and grinding debris using a fluid such as water and/or compressed air. The configured strip 20 is then wound onto the third reel 60.

[0045] Once the entire configured strip 20 has been processed in the second station 48, the configured strip 20 may then be sent to other stations for further processing. For example, the configured strip 20 may be sent to a third station where the configured strip 20 and its nascent needles 26 may be electro-polished and otherwise processed. After passing through the third station, the configured strip 20 may be moved to a mounting station where it is further processed with one or more strips containing adjunct components. In the mounting station, the nascent needles 26 are removed from the configured strip 20 and mounted to the adjunct components. By way of example, the adjunct components may be syringes, handles or portions thereof and may be composed of plastic or other structural material. When the nascent needles 26 are removed from the intermediate strip 20 they may be considered needles 10. The adjunct components may be secured to the needles 10 mechanically and/or through molding to form devices. Thereafter, the formed devices may be packaged for shipment to customers.

[0046] Instead of being mounted to adjunct components, the nascent needles 26 may simply be removed from the rest of the configured strip 20 to form the needles 10, which are then packaged and shipped to customers.

[0047] It is to be understood that the description of the foregoing exemplary embodiment(s) is (are) intended to be only illustrative, rather than exhaustive. Those of ordinary skill will be able to make certain additions, deletions, and/or modifications to the embodiment(s) of the disclosed subject matter without departing from the spirit of the disclosure or its scope.

Claims

What is claimed is:

1. A method of forming needles, comprising: stamping a length of metal to form a configured strip having nascent needles and first and second ribbons connected together by columns to form a plurality of windows, the nascent needles each have a body disposed between first and second end portions, the first end portion being secured to the first ribbon and the second end portion having a free end, and wherein the nascent needles are at least partially disposed in the windows, respectively; moving the configured strip over a plurality of pushers such that the pushers are aligned with, and disposed below, the windows and the nascent needles; moving the pushers upward into the windows to bend the nascent needles so the bodies of the nascent needles slope upward; rotating and lowering a grinding wheel to interact with the second end portions of the nascent needles to thereby remove material from the second end portions to form tapered tips in the second end portions; raising the grinding wheel; and moving the pushers downward to be disposed below the windows, thereby allowing the nascent needles to move back toward their original unbent configurations.

2. The method of forming needles of claim 1, wherein the nascent needles that are aligned with the pushers are a first batch of the nascent needles, and wherein the method further comprises: after moving the pushers downward to be disposed below the windows, moving the configured strip such that the pushers are aligned below a second batch of the nascent needles; moving the pushers upward into the windows to contact the bodies of the nascent needles of the second batch and to bend the nascent needles so the bodies of the nascent needles slope upward; rotating and lowering the grinding wheel to interact with the second end portions of the nascent needles of the second batch to remove material from the second end portions to form tapered tips in the second end portions; raising the grinding wheel; and moving the pushers downward to be disposed below the windows, thereby allowing the nascent needles of the second batch to move back toward their original unbent configurations.

3. The method of claim 1 , wherein the first and second ribbons have holes extending therethrough, wherein the moving of the configured strip aligns the holes over guideposts, and wherein the method further comprises: before the rotating and lowering of the grinding wheel, moving the guideposts upward to extend into the holes, respectively; and after raising the grinding wheel, moving the guideposts downward to no longer extend into the holes.

4. The method of claim 3, wherein the pushers are mounted to a ramp structure, wherein the moving of the pushers upward comprises moving the ramp structure from a disengaged position to an engaged position and wherein the moving of the pushers downward comprises moving the ramp structure from the engaged position to the disengaged position.

5. The method of claim 4, wherein the guideposts are mounted to the ramp structure, wherein the moving of the guideposts upward comprises moving the ramp structure from the disengaged position to the engaged position and wherein the moving of the guideposts downward comprises moving the ramp structure from the engaged position to the disengaged position.

6. The method of claim 5, wherein the ramp structure includes a butte extending from a base, which is movably mounted below a slab with a slot extending therethrough, the butte being at least partially, movably disposed in the slot of the slab; wherein the pushers and the guideposts are mounted to the butte; wherein when the ramp structure is in the disengaged position, the pushers are completely disposed below a top surface of the slab, and when the ramp structure is in the engaged position, the pushers at least partially extend above the top surface of the slab.

7. The method of claim 1 , wherein each pusher has a sloping top surface with a groove formed therein, and wherein during the moving of the pushers, the bodies of the nascent needles are received in the grooves.

8. The method of claim 7, wherein each nascent needle has a pair of wings extending from opposing sides of the body, and wherein the wings are disposed on opposing sides of the groove when the ramp structure is in the engaged position.

9. The method of claim 8, wherein the top surface of each pusher slopes downwardly from an outer edge to an inner edge, wherein each nascent needle has a pair of second wings extending from opposing sides of the body, the pair of second wings being spaced from the pair of first wings, and wherein when the ramp structure is in the engaged position, the inner edge of each of the pushers is disposed between the pairs of the first and second wings of the nascent needle associated with the pusher.

10. The method of claim 1 , wherein the length of metal comprises stainless steel.

11 . The method of claim 1 , further comprising cleaning metal and grinding debris from the nascent needles using water and/or compressed air.

12. The method of claim 11 , further comprising removing the nascent needles from the configured strip to form needles.

13. The method of claim 12, further comprising mounting the needles to adjunct components to form devices.

14. The method of claim 1, wherein the moving of the pushers upward bends the nascent needles in the first end portions.

15. The method of claim 14, wherein the nascent needles each have a body with an arcuate cross-section, and wherein the first end portions of the nascent needles are flat to facilitate the bending of the nascent needles in the first end portions.

16. The method of claim 1 , further comprising: electrically charging the grinding wheel to act as a cathode; electrically charging the nascent needles to act as an anode; and pumping electrolytic fluid between the grinding wheel and the nascent needles to thereby form oxide layers on the second end portions of the nascent needles; and wherein the grinding wheel interacts with the second end portions of the nascent needles to abrasively remove the oxide layers from the second end portions.

17. The method of claim 1 , wherein the rotating and lowering of the grinding wheel places the grinding wheel into physical contact with the second end portions of the nascent needles, thereby mechanically grinding off parts of the second end portions.