KR101402438B1 - Toothbrush having improved tuft retention and anchor wire - Google Patents

Abstract

The handle, especially the toothbrush 200, has a staple 100 for improved tuft retention and use. Staples have a specially designed topography that provides reliable anchoring and manufacturing from cost effective materials. In one embodiment, the present invention is directed to an apparatus comprising a handle 210, a head 210 having a handle 220, at least one hole 215 connected to the handle and extending from the surface 211 to the head, And a staple disposed in the hole and anchoring the cleaning element to the tuft hole, the staple having a longitudinal axis (AA) and a first major surface (20) A plurality of grooves 30 are formed in the first major surface and each groove extends from the bottom edge 111 of the staple toward the top edge 10 of the staple along the straight axis BB, It is a device with a knob that intersects the longitudinal axis at an acute angle [theta] of [deg.] To 70 [deg.].

Description

[0001] TOOTHBRUSH HAVING IMPROVED TUFT RETENTION AND ANCHOR WIRE [0002] BACKGROUND OF THE INVENTION [0003]

The present invention relates to a brush, particularly a toothbrush, and more particularly to an improved anchor or staple design for securing a tuft of bristles within the head of a brush.

In a conventional manufacturing method for a brush, particularly a toothbrush, the brush is injection molded into the empty tuft hole of the toothbrush head. The tuft hole is initially formed in the head simultaneously with the injection molding or is perforated after injection molding. In the second step, U-shaped tufts of bristles are inserted into the holes of the head. Each tuft of bristles is held in place by a plate-like staple that is wider than the tuft hole so that the staple's edge is used to finely shave the sides of the hole when the staple is used to insert the U-shaped bristle tuft into the tuft hole do. The pressure of the surrounding plastic on the staple and the resulting traction friction contribute to the force of keeping the staples in place. However, there are problems associated with brushes made in this manner. In particular, the entire tufts of individual bristles or bristles may unintentionally escape from the tuft hole during brushing by the consumer. Staple or anchor technology addresses these problems in a number of ways. However, proper fastening of tufts of bristles within tuft holes must be balanced against other considerations such as material cost and mass production capability.

For years, at least one of its major surfaces has a parallel horizontal groove (i. E., A groove that extends parallel to the longitudinal axis of the staple) to separate from the tuft hole than a staple having a smooth surface A rectangular shaped toothbrush staple formed into a staple which has proved to be more resistant has become useful.

Staples have also been developed with rounded edges that eliminate and / or minimize the problems of tuft weakness and the possibility of tearing of filaments or bristles at the curves of U. With this rounded structure, the contact area or contact area between the lower staple edge and the bristle filament closely matches the U shape at the curved portion of each tuft. That is, this allows the staples to be deeply inserted into the head, so that a larger, more stable force can be applied to each U-shaped tuft without damaging or damaging the filaments.

Recently, staples having a special groove pattern on the main surface of the staple have been introduced in the art for improved retention, including inclined shapes of parallel grooves.

Staples made from materials with oligodynamic action have also been introduced in the art. These extraordinary staples have a soft main surface; Cadmium, silver, brass, copper, stainless steel, titanium, and mercury.

Typically, the toothbrush staple is made of a nickel-silver alloy. Because of the costs associated with nickel-silver alloys, it has long been eager to manufacture staples from cheap metals such as brass. Although the general concept of using brass staples has been published, testing and experimentation have proven that simply forming and using brass staples of a smooth surface can not be used to manufacture a toothbrush to provide effective tuft retention. Moreover, simply applying a known home pattern proved to be ineffective.

In one aspect, the present invention is a staple having a groove pattern optimized for at least one of its major surfaces. The optimized groove pattern makes it possible to produce staples from materials that are more cost effective than nickel-silver alloys such as brass, while providing the necessary tuft retention for use in viable toothbrush products.

In one such embodiment, the present invention provides a golf club head comprising: a handle; a head having at least one tuft hole extending from the surface to the head and connected to the handle; at least one tuft of bristles disposed in the tuft hole; A brass staple disposed in the tuft hole and anchoring tufts of bristles to the tuft hole and having a longitudinal axis and a first major surface; Wherein each of the grooves extends from a bottom edge of the brass staple to a top edge of the brass staple along a straight axis, the straight axis extending from 40 to 70 Lt; RTI ID = 0.0 > °. ≪ / RTI >

In another aspect, the present invention is a staple having an oblique pattern of grooves on both main surfaces of staples. The inclination of the sloped pattern of grooves for each major surface is chosen such that the pattern on the major surface is operated in a complementary and cooperative manner to improve tuft retention.

In one such embodiment, the present invention provides a golf club head comprising: a handle; a head having at least one tuft hole extending from the surface to the head and connected to the handle; at least one tuft of bristles disposed in the tuft hole; A staple disposed in the tuft hole to anchor the tuft of bristles to the tuft hole and having a longitudinal axis and a first major surface and a second major surface; and a first set of parallel And a second set of parallel grooves formed on a second major surface of the staple; Each groove of the first set extending from a bottom edge of the staple to a top edge of the staple along a linear axis and inclined upward from a first edge in a transverse direction of the staple to a second edge in a transverse direction of the staple, Each of the grooves of the second set extending from the bottom edge of the staple to the top edge of the staple along the linear axis and the staple from the second edge of the staple in the transverse direction, Wherein the linear axis of the second set of grooves intersects the longitudinal axis at a second acute angle.

In yet another aspect, the present invention provides a golf club head comprising a handle, a head having at least one tuft hole connected to the handle and extending from the surface to the head, at least one tuft of bristles disposed in the tuft hole, And a staple disposed in the tuft hole to anchor tufts of bristles to the tuft hole and having a longitudinal axis and a first major surface; Wherein a plurality of parallel grooves are formed in the first main surface, each groove extending from a bottom edge of the staple to a top edge of the staple along a linear axis, the linear axis intersecting the longitudinal axis at an acute angle, Having a width and an adjacent groove spaced apart from each other, and a ratio of the distance to the width is 3.0 to 4.0.

In another aspect, the present invention is directed to a cleaning device comprising a handle, a head connected to the handle and having at least one hole extending from the surface to the head, at least one cleaning element disposed in the hole, An anchor to the tuft hole and having a longitudinal axis and a first major surface; Wherein each of the grooves extends along a straight axis from the bottom edge of the staple toward the top edge of the staple and the linear axis extends along the longitudinal axis to an acute angle of 40 to 70 degrees Crossing toothbrush.

In yet another aspect, the present invention can be a staple for fixing a cleaning element in an anisate mechanism comprising a flat wire having a longitudinal axis and a first major surface, wherein the first major surface has a plurality of And each groove extends from the bottom edge of the flat wire along a straight axis toward the top edge of the flat wire and the straight axis intersects the longitudinal axis at an acute angle of 40 to 70 degrees.

1 is a front perspective view of a staple according to a first embodiment of the present invention;
Fig. 2 is a front view of the staple of Fig. 1; Fig.
3 is a plan view of the staple of Fig.
Figure 4 is a front view of the head of a toothbrush engaged with the staple of Figure 1 for anchoring a cleaning element in the form of tufts of bristles;
5 is a cross-sectional view of the toothbrush taken along line V-V in Fig.
Figure 6 is a cross-sectional view of the toothbrush according to lines VI-VI of Figure 4;
7 is a front perspective view of a staple according to a second embodiment of the present invention;
8 is a front view of the staple of Fig.
Fig. 9 is a rear view of the staple of Fig. 7; Fig.
10A is a table of experimental data for tuft retention for a first toothbrush type using Ag-Ni staples with longitudinal grooves.
FIG. 10B is a graph of experimental data in the table of FIG. 10A. FIG.
11A is a table of experimental data for tuft retention for a first toothbrush type using brass staples having grooves angled in accordance with an embodiment of the present invention.
FIG. 11B is a graph of experimental data in the table of FIG. 11A. FIG.
12A is a table of experimental data for tuft retention for a second toothbrush type using Ag-Ni staples with longitudinal grooves.
FIG. 12B is a graph of experimental data in the table of FIG. 12A. FIG.
13A is a table of experimental data for tuft retention for a second toothbrush type using brass staples having angled grooves according to an embodiment of the present invention.
13B is a graph of experimental data in the table of Fig. 13A. Fig.
14A is a table of experimental data for tuft retention for a third toothbrush type using Ag-Ni staples with longitudinal grooves.
FIG. 14B is a graph of experimental data of the table of FIG. 14A. FIG.
15A is a table of experimental data for tuft retention for a third toothbrush type using brass staples having angled grooves according to an embodiment of the present invention.
FIG. 15B is a graph of experimental data of the table of FIG. 15A. FIG.

1 to 3 show a staple 100 according to an embodiment of the present invention. The staple 100 is a flat wire member that is used as an anchor in a brush, particularly a toothbrush, to secure U-shaped tufts of bristles within tuft holes formed in the head of a handle-like device such as a toothbrush. The staple 100 has a substantially rectangular cross-section (longitudinal and transverse) and is elongated along the longitudinal axis A-A. Of course, other shapes may also be used to form the staples.

The staple 100 is limited by the outer circumference including the top edge 10, the bottom edge 11, the first edge 12 in the transverse direction, and the second edge 13 in the transverse direction. The staple 100 has a length L, a height H, and a thickness t. The length L of the staple 100 depends on the size of the tuft hole to be inserted, but is preferably in the range of 2.09 to 2.13 mm for a 1.70 mm tuft hole, and most preferably 2.11 mm. The height H of the staple 100 depends on the dimensions of its end use, but is preferably in the range of 1.49 to 1.51 mm for a 1.70 mm tuft hole, most preferably 1.50 mm. Similarly, although the thickness t of the staple 100 also depends on its end use, a range of 0.24 to 0.26 mm is preferred, and 0.25 mm is most preferred. However, the present invention is not limited to all embodiments, and other dimensions may be used. The exact dimensions of the final product depends on the size of the tuft hole, the type and size of the bristle tuft, the type of brush on which the staple is used, and so on. In addition, while staple 100 is shown as having a generally uniform thickness t, height H and length L, one or more of these dimensions may be oblique and / or irregular.

In the illustrated embodiment, the edges 10-13 of the staple 100 are flat. However, in other embodiments, one or more of the edges 10-13 may be formed to provide additional tuft retention and / or to reduce pressure at the curved portions of the bristle tufts. For example, the transverse edges 12-13 may be serrated, sharpened, or barb formed, and the bottom edge 11 may be rounded.

The staple 100 further includes a first major surface 20 and a second major surface 21. The second major surface 21 is on the opposite side of the first major surface 20 so that the staple 100 is a flat, rectangular plate-like structure. The first major surface 20 includes a first set of grooves 30 formed on the first major surface 20 to cover substantially the entirety thereof. All grooves 30 are parallel to one another and are equidistant apart from one another. In some embodiments, however, not all grooves 30 may be parallel to one another, and the distance between adjacent grooves may vary irregularly or as a function of the distance from one or both of the transverse edges 12-13.

Due to the grooves 30 that are spaced apart from each other, a continuous ridge 31 is formed between the adjacent grooves 30. It is preferable that the protruding portion 31 is an elongated strip, not formed in a segment shape. In other words, the first major surface 20 preferably does not include grooves that intersect with each other. Briefly, it is preferred that the groove pattern on the first major surface 20 be free of intersecting grooves.

The grooves 30 are linear in the preferred embodiment shown and each extend along the groove axis B-B. However, in other embodiments, the grooves 30 may be curved, zigzag, or irregular in shape.

The grooves 30 are preferably spaced apart from each other by a distance D of 0.29 to 0.31 mm, most preferably about 0.30 mm. Most preferably, the groove 30 has a width W of 0.09 to 0.11 mm, especially about 0.10 mm. In one embodiment, the ratio of the distance D to the width W is in the range of 3.0 to 4.0, most preferably 3.0. The groove 30 has a depth of 0.09 to 0.11 mm and a depth of about 0.11 mm. However, the exact dimensions of the groove and its pattern can vary considerably and are not considered to limit the invention unless specifically stated in the claims. However, in one embodiment, the depth of the groove 30 is preferably 1/3 or less of the thickness t of the staple 100. It has been found that fabricating the groove 30 with a depth greater than 1/3 of the thickness t results in unwanted distortion of the wire / staple 100.

The groove 30 is elongated to the entire height H of the staple 100 and extends from the top edge 10 to the bottom edge 11. [ The groove 30 is disposed on the first major surface 20 of the staple 100 so as to be inclined with respect to the longitudinal axis A-A. Alternatively, the groove axis B-B of each groove 30 forms an angle that is not perpendicular to the longitudinal axis A-A of the staple 100. In particular, the groove axis B of the groove 30 provides for adequate tuft retention when inserted into the toothbrush and is provided with an angular orientation (&thetas;) that is specifically selected to maintain the structural integrity of the staple 100 when inserted into the toothbrush, Intersects axis AA. The acute angle? Plays a crucial role in achieving the desired goal of increased tuft retention, depending on the constituent metal. It has also been found that the angle of the groove pattern allows cheap and / or soft metal to be used without undesired deformation and / or curling of the wire. However, the selected metal should not be so soft that the imprinting of the groove pattern causes unwanted deformation and curling. For example, aluminum has been found to be inadequate in most cases. In one preferred embodiment, a metal having a Brinell hardness lower than nickel-silver and higher than aluminum for staple 100 is selected.

By experiment, it is necessary that the acute angle [theta] be 40 [deg.] To 70 [deg.], Preferably 55 [deg.] To 65 [deg.], And most preferably about 60 [deg.] To form staples 100 that are properly executed from brass . When the acute angle [theta] with respect to brass is less than 40 [deg.], The wire has a tendency to deform and wind. However, it is difficult to imprint a groove pattern having an angle when the angle is larger than 70 DEG with respect to brass. Also, when the acute angle of the groove is within the desired range, the experiment using the toothbrush breakout experiment shows that the tuft retention is greatly increased by 25% compared to other anchors that are grooved or not grooved.

The grooves 30 are formed on the first major surface 20 so as to be inclined upwardly from the bottom edge 11 to the top edge 10 to go from the first edge 12 in the transverse direction to the second edge 13 in the transverse direction. . Of course, the grooves 30 may be inclined upwardly, if necessary, from the bottom edge 11 to the top edge 10 to extend from the second edge 13 in the transverse direction to the first edge 12 in the transverse direction As shown in FIG. The second major surface 21 of the staple 100 is preferably a smooth surface without grooves or topography. In another embodiment, these second major surfaces are also patterned into grooves (as described below with respect to Figures 7 to 9).

The grooves 30 may be formed by roll pressing or stamping the brass sheet with a die and then cutting the sheet into the desired strip and the strip is cut to form the staple 100.

Figs. 4-6 illustrate a toothbrush 200 in which each bristle tuft 50 is anchored to tuft hole 215 by a single staple 100. Fig. Although bristle tufts 50 are shown, other cleaning elements, including elastomeric fingers, fibers, and the like, may also be used. The toothbrush 200 includes a head 210 and a neck 220 extending with a elongated handle. A plurality of tuft holes 215 are formed in the front surface 211 of the head 210. The head 210 is typically made of hard plastic such as polypropylene.

Each of the plurality of tuft holes 215 in the toothbrush head 210 is extended downward along the central axis C-C from the front surface 211 of the head 210. [ The tuft hole 215 preferably includes a circular bore formed in the head 210. Of course, if desired, the tuft holes 215 may be formed in other shapes.

During manufacture, the bristle tufts 50 are bent into a U-shape and secured within the tuft hole 215 by the staple 100. The staple 100 is inserted into the tuft hole 215 such that each bristle tuft 50 is bent into a U-shape and can include a curved portion 51 and two extension legs 52, The legs 52 and 53 of the bristle tuft 50 extend upward from the hole 215 and extend over the front surface 211 of the head 210. The curved or bent portion 51 of the bristle tuft 50 contacts the bottom edge 11 of the staple 100 while the two legs 52 and 53 extend upward to form a bristle of the stretched and visible toothbrush.

The two edges 12-13 in the transverse direction of each staple 10 are slightly extended into the opposing side walls of each hole 215. [ The rotational position of the plane holding each staple 100 is not important, i.e., the staple 100 is installed by rotating the staple about its central vertical axis different from the rotational position of about 45 degrees before installation . However, it is preferred that the staple 100 be disposed in the tuft hole 215 such that the longitudinal axis of the staple 100 is perpendicular to the central axis C-C of the tuft hole 215.

7 to 9 show a staple 100A according to a second embodiment of the present invention. The basic structure of the staple 100A is the same as that of the staple 100. Fig. Accordingly, similar reference numerals having the suffix A added thereto are used to indicate corresponding parts and features. In order to avoid duplication, only the features of the staple 100A different from the staple 100 will be described below with the understanding that the description as described above can be applied.

The main difference between the staple 100A and the staple 100 is that in addition to the first set of grooves 30A formed in the first major surface 20A the second major surface of the staple 100A is the second set of grooves 40A). The above description of the groove 30 of the staple 100 is generally applicable to the grooves 30A and 40A and is therefore hereby incorporated by reference. However, in this embodiment of the present invention, it should be appreciated that the staple 100A is not limited to the exact range for the acute angle [theta]. However, the acute angle is preferably 40 to 70 degrees.

The groove 30A formed in the first surface 20A of the staple 100A is tilted upward from the bottom edge 11A to the top edge 10A so that the second edge 12A from the first edge 12A in the transverse direction, (11A). However, the groove 40A formed in the second surface 21A of the staple 100A is inclined upward from the bottom edge 11A to the top edge 10A so that the second edge 13A extends in the transverse direction from the second edge 13A in the transverse direction, 1 < / RTI > edge 12A. In other words, the grooves 30A and 40A are elongated in a direction inclined to the opposite side. Of course, the inclination directions of the grooves 30A and 40A may be staggered. The grooves 30A and 40A are preferably arranged such that the openings along the top and bottom edges 10A and 11A are staggered along the length of the staple 100A.

Experiment

Three different types of commercially available toothbrushes were used to determine and compare brass staples with a typical Ag-Ni staple having a longitudinal groove (i.e., 0 [deg.]) And a groove with an angle of 60 [ The experiment was carried out. Three other tested toothbrushes are referred to herein as toothbrush 1, toothbrush 2, toothbrush 3.

A test for toothbrush 1 will be described with reference to Figs. 10A-11B. Using Ag-Ni staples with longitudinal grooves as anchors, the test parameters for toothbrush 1 and the details of tuft retention data are shown in the table of Figure 10a and the graph of Figure 10b. Details of the test parameters and tuft retention for the toothbrush 1 using brass staples with grooves having an angle of 60 degrees as an anchor are shown in the table of Figure 11a and the graph of Figure 11b. As can be appreciated, for the toothbrush 1, the Ag-Ni staple with longitudinal grooves was shown to have an average tuft retention of 3.7 kgf and a CPK of 1.5. By comparison, the brass staple with grooves with an angle of 60 degrees had an average tuft retention of 3.7 kgf and a large CPK of 1.82.

Test data for toothbrush 2 will be described with reference to Figures 12A-13B. Details of the test parameters and tuft retaining data for toothbrush 2 using Ag-Ni staples having longitudinal grooves as anchors are shown in the table of FIG. 12A and the graph of FIG. 12B. Details of the test parameters and tuft retention for toothbrush 2 using brass staples with grooves having an angle of 60 [deg.] As anchor are described in the table of Figure 13a and the graph of Figure 13b. As can be appreciated, the Ag-Ni staple with longitudinal grooves showed an average tuft retention of 3.8 kgf and a CPK of 2.24. By comparison, the brass staple with grooves with an angle of 60 degrees had an average tuft retention of 4.0 kgf and a large CPK of 2.48.

Test data for toothbrush 3 will be described with reference to FIGS. 14A-B. The details of the test parameters and tuft retaining data for toothbrush 3 using the Ag-Ni staple with longitudinal grooves as anchors are shown in the table of Figure 14a and the graph of Figure 14b. Details of the test parameters and tuft retention for the toothbrush 3 using a brass staple having a groove with an angle of 60 [deg.] As anchor are described in the table of Figure 15a and the graph of Figure 15b. As can be appreciated, Ag-Ni staples longitudinally grooved against toothbrush 3 exhibited an average tuft retention of 2.4 kgf and a CPK of 0.63. By comparison, a brass staple with a groove with an angle of 60 degrees showed an average tuft retention of 2.8 kgf and a large CPK of 1.09.

The present invention has been described and illustrated in sufficient detail to enable those skilled in the art to make and use the invention with ease, and various alternatives, modifications and improvements will readily appear without departing from the spirit and scope of the invention.

10: upper edge 11: bottom edge
20: first main surface 21: second main surface
30: groove 50: bristle tuft
100: Staple

Claims (22)

A handle,
A head having at least one tuft hole connected to the handle and extending from the surface to the head,
At least one tuft of bristles disposed in the tuft hole,
A brass staple disposed in the tuft hole and anchoring tufts of bristles to tuft holes and having a longitudinal axis and a first major surface,
Wherein each of the grooves extends from a bottom edge of the brass staple to a top edge of the brass staple along a straight axis, the straight axis having an acute angle of 40 to 70 degrees with respect to the longitudinal axis, Each groove having an adjacent groove spaced apart from one another by a width and a distance, the ratio of the distance to the width being between 3.0 and 4.0. The tuft of bristles according to claim 1, wherein the tufts of the bristles are U-shaped with curved and leg portions, the tufts of the U-shaped bristles are anchored to the tuft holes by brass staples so that the leg portions extend upward and protrude from the tuft holes Wherein the brass staple is disposed between the leg portions and the curved portion of the brass staple. The toothbrush of claim 1, wherein the acute angle is 60 degrees. 2. The toothbrush of claim 1, wherein the staple has a thickness and the groove has a depth not greater than 1/3 of the depth of the thickness of the staple. The toothbrush of claim 1, wherein the brass staple is a flat wire having a rectangular cross-section. 2. The toothbrush of claim 1, wherein the grooves are uniformly spaced apart from each other and cover the entire first major surface. 7. The toothbrush of claim 6, wherein the adjacent grooves are spaced apart from one another by a distance of 0.29 mm and 0.31 mm. 8. The toothbrush of claim 7, wherein the groove has a width of 0.09 to 0.10 mm. 7. The toothbrush of claim 6, wherein the groove has a depth of 0.09 to 0.10 mm. 2. The staple cartridge of claim 1, wherein the brass staple comprises a second major surface opposite the first major surface, wherein the first major surface includes only grooves and the second major surface is flat and non- toothbrush. 2. The toothbrush of claim 1, wherein the tuft hole has a central axis and the longitudinal axis of the staple is orthogonal to the central axis of the tuft hole. A handle,
A head having at least one tuft hole connected to the handle and extending from the surface to the head,
At least one tuft of bristles disposed in the tuft hole,
A staple disposed in the tuft hole to anchor tufts of bristles to tuft holes and having a longitudinal axis and a first major surface and a second major surface;
A first set of parallel grooves formed on a first major surface of the staple,
A second set of parallel grooves formed on a second major surface of the staple,
Each groove of the first set extending from the bottom edge of the staple to the top edge of the staple along the linear axis and inclined upward from the first edge in the transverse direction of the staple to the second edge in the transverse direction of the staple, Each of the grooves of the second set extending from the bottom edge of the staple to the top edge of the staple along the straight axis and the second edge of the second set of lateral edges of the staple, Wherein the linear axis of the second set of grooves intersects the longitudinal axis at a second acute angle and extends in the first and second sets of staples along the top and bottom edges of the staple, Wherein the openings of the grooves of the toothbrushes are staggered along the length of the staples. 13. The toothbrush of claim 12, wherein the first acute angle is between 40 and 70 and the second acute angle is between 40 and 70. 14. The toothbrush of claim 13, wherein the first and second acute angles are 60 degrees. 13. The toothbrush of claim 12, wherein the staple is a flat brass wire. 13. The toothbrush of claim 12, wherein the first and second sets of grooves are uniformly spaced apart from each other and cover the entirety of the first and second major surfaces, respectively. A handle,
A head having at least one tuft hole connected to the handle and extending from the surface to the head,
At least one tuft of bristles disposed in the tuft hole,
And a staple disposed in the tuft hole to anchor tufts of bristles to tuft holes and having a longitudinal axis and a first major surface,
Wherein a plurality of parallel grooves are formed in the first main surface, each groove extending from a bottom edge of the staple to a top edge of the staple along a linear axis, the linear axis intersecting the longitudinal axis at an acute angle, And having an adjacent groove spaced apart from one another by a distance, the ratio of the distance to the width being between 3.0 and 4.0. 18. The toothbrush of claim 17, wherein the acute angle is between 40 ° and 70 °. 19. The toothbrush of claim 18, wherein the staple is made of brass. delete delete 1. A staple comprising a flat wire having a longitudinal axis and a first major surface for securing a cleaning element in a hand-held instrument,
Wherein each of the grooves extends from a bottom edge of the flat wire along a straight axis toward a top edge of the flat wire, the straight axis having a longitudinal axis of 40 to 70 degrees , Each groove having an adjacent groove spaced apart from one another by a width and a distance, the ratio of the distance to the width being between 3.0 and 4.0.

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