JP2004337586A - Bowling pin, manufacturing method thereof, and die set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bowling pin which not only satisfies conditions of shape, weight, dry sound generated upon collision but also has superior durability without peeling off a skin part or a display part even when receiving impact or friction is given, a manufacturing method thereof, and a die set used therefor. <P>SOLUTION: This bowling pin is provided with a core material 3 with a hollow part 5 formed of synthetic resin and the skin part 15 comprising synthetic resin with impact resistance higher than that of the core material 3. In the bowling pin, the synthetic resin of the core material 3 is preferably polypropylene and the synthetic resin formed into the surface of the core material is preferably polyamide resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a boring pin, a method for manufacturing the same, and a mold set used for the manufacture.

Bowling is not only widely enjoyed as an easy leisure, but also a popular sport.
It is important for a pin used for boring to fall easily when a ball or a pin collides, and if the conditions such as a collision force and a collision angle at the time of collision are the same, the pin must fall uniformly. Therefore, according to international standards, the shape and weight are height: 38 cm, maximum diameter part: 12 cm, bottom diameter: 6 cm, weight: 1417 g to 1644 g, and the weight of 10 pins arranged in each lane The difference is strictly defined as less than 113 g.

Bowling pins need to have the unique dry sound generated when balls and pins collide with each other, and the durability to withstand repeated collisions.Conventionally, a wooden core material coated with a synthetic resin layer on the surface is used. Had been used. In addition, on the surface of the wooden bowling pin, display portions such as characters and patterns were formed by baking.
For example, in Patent Document 1, a circumferential groove having an appropriate width and depth is provided around the largest diameter portion of a boring pin body made of wood, and a synthetic resin ring is fitted into the circumferential groove. There is disclosed a boring pin in which a vertically long cavity is provided at the center of a small diameter portion, a mandrel made of synthetic resin is fitted into the cavity, and the outer surface is covered with an outer coating of synthetic resin.
Japanese Utility Model Laid-Open No. 6-77781

However, the boring pin of Patent Literature 1 has some problems because the main body is made of wood.
For example, the maximum weight of a ball is about 7.52 kg, and when colliding with a pin, the energy of the ball is very large due to the speed of the pitch, and the pin is replaced with a new one in a few months, depending on the frequency of use. Therefore, there is a problem that the usable period is relatively short.

Therefore, a synthetic resin having excellent durability can be used as the core material of the boring pin, but it also has some problems.
First, the synthetic resin has a higher specific gravity than wood, so if it is manufactured in the prescribed shape, the weight will be too large. Second, the unique drying of the pin when the ball or the pin collides with each other. That is, it does not emit a sound.

Therefore, it was thought that the above problem could be solved by making the core material made of synthetic resin hollow. However, when a hard synthetic resin is insert-molded on the surface of a core material manufactured in a hollow shape, the core material cannot withstand high temperature and high pressure and is deformed and cannot be made into a product.
Further, when the ball collides with the pin, the skin portion of the surface of the bowling pin receives considerable impact and friction when the bowling pin collides with each other and when the ball is further reset when the fallen pin is reset. For this reason, the display part such as letters and patterns formed by baking painting of the surface and the skin part that has been clear painted will peel off in a short period of time and it will not look good, so repainting or frequently replacing the pin with a new one I had to change it.

The present invention has been made in view of the above-mentioned conventional problems, and not only satisfies the conditions such as the shape, weight, and dry sound generated at the time of a collision required for a boring pin, but also has excellent durability. An object of the present invention is to provide a boring pin and a method for manufacturing the same.
Another object of the present invention is to provide a highly durable boring pin that does not peel off even when the display unit receives an impact or friction, a method of manufacturing the same, and a mold set used in the manufacture thereof.

In order to achieve the above object, the boring pin according to claim 1 is a core material having a hollow portion formed of a synthetic resin, and a synthetic resin molded on the surface of the core material and having higher impact resistance than the core material. And a skin portion comprising:
According to this boring pin, it is possible to emit a dry-burning sound when a ball or a pin collides with each other, as in the case of a conventional pin having a wooden core, and it is possible to satisfy the prescribed shape and weight. .
The boring pin according to claim 2 is the method according to claim 1,
The synthetic resin of the core material is polypropylene, and the synthetic resin formed on the surface of the core material is a polyamide resin.
The boring pin according to claim 3 is characterized in that, in claim 1 or 2, the surface layer of the skin portion is not further coated.
The boring pin according to claim 4 is the method according to claim 1,
A cover which has a base portion, a display member provided on the base portion to display characters, patterns, and the like, and a transparent portion which covers the display member and allows the characters, patterns, etc. of the display member to be seen through, and further connected to the base portion The boring pin is characterized in that the display portion constituted by the above is embedded in the skin portion with a part thereof being exposed.
The boring pin according to claim 5 is the device according to claim 4,
The base portion and the cover are formed in a fitting structure.
According to a sixth aspect of the present invention, in the boring pin according to the fourth or fifth aspect, the synthetic resin forming the base portion is more flexible than the synthetic resin forming the cover.
A boring pin according to claim 7, wherein the display body according to any one of claims 4 to 6, wherein the display body is exposed from the skin part, and the skin part is provided on the outer periphery of the exposure part and is formed one step lower than the exposure part. And a buried portion to be buried in the body.
An eighth aspect of the present invention provides the bowling pin according to any one of the fourth to seventh aspects, wherein at least a surface of the base portion on which the display body is arranged is colored.
The boring pin according to claim 9 is the method according to claim 1,
The display unit has an exposed portion exposed from the skin portion, and a buried portion provided on the outer periphery of the exposed portion, and buried in the skin portion formed one step lower than the exposed portion,
The display unit has a curved transparent plate and a display body stacked on the back side thereof,
The transparent plate is formed by being curved so as to have a shape along the circumferential direction of the bowling pin,
It is characterized in that a part of the display part is buried in a skin part in a state of being exposed on a surface of a bowling pin.
The boring pin according to claim 10 is the method according to claim 9,
Characters and patterns printed on the display body laminated on the back side of the transparent plate are directly printed on the back side of the transparent plate, so that the display body is omitted.
The method for manufacturing a boring pin according to claim 11 is:
A synthetic resin serving as a core material having a hollow portion is formed by an injection molding method, a deformation preventing material is fitted into the hollow portion from an opening of the core material, and the core material is set in a mold. It is characterized in that a skin portion made of a synthetic resin having higher impact resistance than the core material is formed on the surface of the material.
The method for manufacturing a boring pin according to claim 12 is:
In the eleventh aspect, before forming the skin portion, a display portion is formed on the surface of the core material, and the skin portion is formed so that the display portion is exposed.
The method for producing a bowling pin according to claim 13 is:
In the eleventh aspect, a concave portion is formed in the skin portion, and the display body is formed of a synthetic resin in the concave portion.
The method for manufacturing a boring pin according to claim 14 is:
In claim 11,
In the display unit, an exposed portion exposed from the skin portion, and a buried portion provided on the outer periphery of the exposed portion, and buried in the skin portion formed one step lower than the exposed portion is provided,
The display unit has a curved transparent plate and a display body laminated on the back side thereof,
The transparent plate is formed by being curved so as to have a shape along the circumferential direction of the bowling pin,
It is characterized in that a part of the display part is buried in the skin part in a state of being exposed on the surface of the bowling pin.
A mold set according to a fifteenth aspect is a mold for manufacturing the boring pin according to the first aspect, wherein the inner surface of the core forming die has a rough surface, and the inner surface of the core forming die has a rough surface. It is characterized in that the inner surface of the mold has a mirror roughness.

As described above, according to the boring pin according to the present invention, the material used as the core material has good injection moldability, rigidity, impact strength, hardness, low cost, using a synthetic resin excellent in recyclability, The material used as the skin portion is characterized by using a synthetic resin that is more excellent in friction and wear resistance, impact resistance, and hardness than the core material, and thus can be used for an extremely long time.
Further, in the bowling pin according to the present invention, it is not necessary to apply a primer, a clear coating, or the like to the upper layer of the skin portion. Since the synthetic resin of the skin portion is extremely hard and has excellent scratch resistance, friction and wear resistance, impact resistance, and the like, the surface of the skin portion can be kept clean without any treatment.
Further, since the core material is formed of a polypropylene resin and the skin portion is formed of a polyamide resin, the core material is excellent in durability and recyclability.
In addition, the hollow shape not only satisfies the conditions such as the shape and weight stipulated in international standards, but also generates a unique dry sound that eliminates stress when balls and pins collide with each other. be able to.

Further, the boring pin is not deformed even if a compressive force acts from the surface of the core material having the hollow portion during insert molding of the skin portion, because the deformation preventing material is fitted into the hollow portion.
Furthermore, since the cap used at the time of the product is used when insert molding the skin portion, it is economical and efficient.

ADVANTAGE OF THE INVENTION According to the boring pin which concerns on this invention, a skin part or a display part does not peel even if it receives an impact or friction, and it becomes possible to obtain high durability. Therefore, it is possible to reduce the cost in using the boring pin.
Also, unlike the conventional baked coating, vivid coloring is possible.

A boring pin 1 according to a first embodiment of the present invention and a method for manufacturing the same will be described with reference to FIGS. The configuration of the boring pin 1 according to the present embodiment will be described with reference to FIG.
In FIG. 1, reference numeral 3 denotes a core material, and a hollow portion 5 extending in a vertical direction is formed in the core material 3. Upper and lower ends of the hollow portion 5 are open, and a cap 9 as a deformation preventing material is fitted in the upper opening 7, and a cap 13 is fitted in the lower opening 11. The core material 3 and the cap 9 are almost covered by a skin portion 15, and two line portions 17 and a character portion 19 as a display body are exposed from the skin portion 15 in the missing portion of the skin portion 15. Is formed. In the present embodiment, the skin portion 15 is white, the line portion 17 is red, and the character portion 19 is black. These colors can be colored as desired by blending a pigment with a synthetic resin,

The kind of the synthetic resin as the material of the core material 3 is not particularly limited, but a polypropylene resin is exemplified. Polypropylene resin is suitable as a core material because it is lightweight, has good heat resistance and good injection moldability, and has rigidity, impact strength and hardness. Further, it is suitably used in terms of low cost and recyclability.
The core material desirably has an Izod impact strength (notched, 20 ° C., ASTM D253) of 200 J / m or more and a Rockwell R hardness of 80 (20 ° C., ASTM D785) or more.
Depending on the composition of the polypropylene resin, there are a homopolymer (homopolymer), a random copolymer and a block copolymer which are copolymers, and a block copolymer having excellent impact resistance is used as a core material. preferable. Examples of commercially available polypropylene resins include “J-750HP” manufactured by Idemitsu Petrochemical Co., Ltd.
Further, by blending another resin with the polypropylene resin, more excellent characteristics can be provided. For example, a synthetic resin obtained by blending a polyamide resin with a polypropylene resin can be used.
Further, a reproduction pellet or the like can be used. The regenerated pellets have the following composition, for example.
Admar (trademark) 9-15% (weight, same hereafter)
6 nylon (trademark) 0-46%
666 nylon (trademark) 0-33%
12 nylon (trademark) 0-8%
EVOH resin 0-21%
Ever (trademark) 0-39%
PE (polyethylene) 0-53%
PP (polypropylene) 0-45%
These are adjusted to a total of 100% and blended.

It is preferable that the skin portion 15 is formed of a synthetic resin having more frictional wear resistance and impact resistance than the core material 3. For example, a polyamide resin having an amide group bond, which is a thermoplastic engineering plastic, is preferably exemplified. Polyamide resin is excellent in friction and wear resistance and impact resistance, and is suitable as a material for a skin portion of a boring pin.
The properties of the skin portion are desirably 600 J / m or more in Izod impact strength (notched, 23 ° C., ASTM D253) and 110 or more in Rockwell R hardness (23 ° C., ASTM D785). , Abrasion resistance, impact resistance, and hardness are required to be high. That is, the skin portion is a portion that directly receives an impact by a bowling ball, and must not have any cracks or scratches, and extremely severe characteristics are required.

Depending on the composition of the polyamide resin, there are a homopolymer (homopolymer) and a copolymer nylon which is a copolymer. As the material for the skin portion, any material can be used. Resins ([NH (CH2) 5CO] n, nylon 6) can be suitably used.
Furthermore, gloss and flexibility can be imparted to the appearance by blending a small amount of an elastomer with the poly ε-caproamide resin, so that it can be more preferably used as a material for the skin portion.
Examples of commercially available resins obtained by blending a small amount of an elastomer with a poly ε-caproamide resin include “Amilan U141” (trade name, manufactured by Toray Industries, Inc.).
Further, by blending another resin or pigment with the polyamide resin, further different characteristics can be imparted. For example, the skin portion can be colored ivory by blending a pigment.
For the line portion 17, for example, a polyamide resin can be used, and for the character portion 19, for example, a urethane resin can be used.
The materials used for the core material, the skin portion, and the line portion are commonly used in other embodiments.

In the present invention, it is not necessary to apply a primer, a clear coating, or the like to the upper layer of the skin portion 15. Since the synthetic resin of the skin portion is extremely hard and has excellent scratch resistance, friction and abrasion resistance, impact resistance, etc., the surface of the skin portion can be kept clean without applying anything. . Further, when a polyamide resin is used for the skin portion, it is difficult to adhere the coating thereon, so that the clear coating or the like is peeled off during use and the appearance is worsened.
In the present invention, the material used as the core material is a synthetic resin having good injection moldability, rigidity, impact strength, hardness, low cost, and excellent recyclability. Another feature is that a synthetic resin having excellent friction wear resistance, impact resistance and hardness is used.

  Next, a method for manufacturing the boring pin 1 according to the present invention will be described. First, the core material 3 is manufactured in advance. That is, as shown in FIG. 2, cores 23 and 25 forming the hollow portion 5 are set in the mold 21, and a synthetic resin is injected into the cavity 27 through the gate 26 to form the core material 3.

The core 25 is formed with a diameter larger than the diameter of the upper end portion of the core 23, and the diameter is further increased from the middle part. 8 are formed. The step portion 6 is formed in the middle of the upper end portion of the hollow portion 5, and the step portion 8 is formed near the upper opening 7 (see FIG. 3).
In addition, since the ridge 29 is formed on the outer peripheral surface of the base end of the core 23, the concave ridge 31 is formed on the inner peripheral surface of the lower end of the hollow portion 5. In addition, since the convex portion 24 projecting from the cavity 27 is formed on the mold 21, a small hole 33 is formed on the outer peripheral surface of the core material 3 (see FIG. 3).

Next, the core material 3 is taken out of the mold 21 and the cap 9 is driven into the hollow portion 5 from the upper opening 7 of the core material 3 as shown in FIG. A head 35 is provided on the cap 9, and a round hole 37 is formed at the center of the head 35.
In addition, it is preferable that the outer surface of the core material 3 has a rough surface roughness in order to enhance the adhesion of the skin portion. For this reason, it is preferable that the average roughness of the inner surface of the mold 21 for forming the core material 3 is 0.1 mm or more in terms of Ra.
Next, as shown in FIG. 4, the core 3 into which the cap 9 has been driven is set in a mold 39, and the iron bar 41 is inserted into the round hole 37 of the cap 9 to fix the core 3. Since the core material 3 is fixed by the iron bar 41, the height of the boring pin 1 can be reliably controlled. The mold 39 is provided with a cavity 43 for forming the character portion 19, and a urethane resin is injected into the cavity 43 through a gate 45 to form the character portion 19 as a display. Since the character portion 19 flows into the small hole 33 of the core 3, the character portion 19 is securely fixed to the core 3.

The core material 3 on which the convex character portion 19 as a display body is formed as described above is set in a mold 47 as shown in FIG. 5, and the iron bar 41 is inserted into the round hole 37 of the cap 9. 3 is fixed. The mold 47 is provided with a cavity 49 for forming the skin portion 15, and a polyamide resin is injected into the cavity 49 through a gate 51 to form the skin portion 15.
The cap 9 is covered with a skin portion 15, and two concavities 52 having a thin skin portion 15 are formed in a narrow portion of the core material 3.
It is preferable that the inner surface of the mold 47 for forming the skin portion 15 be mirror-finished because the inner surface roughness of the mold 47 is transferred to the skin portion 15 as it is. For example, it is preferable that the roughness of the inner surface of the mold 47 be less than 1 μm as the average surface roughness Ra.
By making the skin portion a mirror surface state, the boring pin has improved scratch resistance and abrasion resistance, and maintenance such as cleaning of the boring pin becomes easy.
As described above, since the inner surface roughness of the mold that forms the core material is roughened, the surface of the roughened core material is covered with a surface portion provided with a mechanical adhesive force, and further, Since the inner surface of the mold for forming the skin portion is mirror-finished as described above, a multi-layer boring pin including a core material and a skin portion having excellent appearance is provided.

When a polyamide resin is used as the skin portion 15, the resin temperature is 250 ° C. or higher and the inside of the cavity 49 is pressurized. However, since the cap 9 is fitted into the upper end of the hollow portion 5, The core material 3 can be reliably manufactured into a predetermined shape defined by international standards without deformation.
The character portion 19 is exposed. When the skin portion 15 is formed, pressure is applied to the character portion 19. As described above, since the character portion 19 is formed of an urethane-based resin having elasticity, the character portion 19 is compressed to increase the density, and the character portion 19 becomes clear and easily visible. In addition, it does not wear out and disappear like a character portion formed by painting.

  Next, as shown in FIG. 6, the core material 3 on which the skin portion 15 is formed is set in a mold 53, and a red polyamide resin is injected into the concave portion 52 through a gate 55, and is subjected to so-called two-color molding. The book line portions 17 are formed. Since the line portion 17 is formed of the synthetic resin filled in the concave portion 52, the line portion 17 does not disappear and disappear like the line portion formed by painting.

As described above, the core material 3 formed on the skin portion 15, the line portion 17, and the like is removed from the mold 53, and the cap 59 is inserted into the hole 57 formed after the iron bar 41 is removed. Driving in round hole 37. The protrusions 60 formed on the outer peripheral surface of the cap 59 are fitted into the concave portions 62 formed on the inner peripheral surface of the round hole 37, so that the cap 59 is prevented from coming off.
Further, the cap 13 is driven into the lower opening 11, and the convex portion 14 of the cap 13 is fitted into the groove 31 formed on the inner peripheral surface of the hollow portion 5, so that the cap 13 is prevented from coming off. The head 16 of the cap 13 comes into contact with the lower surface of the core 3. Thus, the boring pin 1 of the present embodiment is completed.

A boring pin 101 and a method of manufacturing the same according to a second embodiment of the present invention will be described with reference to FIGS.
Since the boring pin 101 according to the second embodiment has the same components as the boring pin 1 according to the first embodiment, the components are used in the description of the first embodiment. The description is omitted by attaching the same reference numerals as the reference numerals.

  First, the configuration of the boring pin 101 will be described with reference to FIG. Reference numeral 103 denotes a core material, and the core material 103 has an upper hole 105a and a lower hole 105b as hollow portions. A synthetic resin constituting the core material 103 is interposed between the upper hole 105a and the lower hole 105b, and the upper hole 105a and the lower hole 105b have a bottom. The upper hole 105a has an upper opening 107a at the upper end of the core 103, and the lower hole 105b has a lower opening 107b at the lower end of the core 103. A cap 9 as a deformation preventing material is fitted in the upper opening 107a, and a cap 13 is fitted in the lower opening 107b. The core material 103 and the cap 9 are almost covered by the skin portion 15, and the two line portions 17 and the display portion 109 are formed in the missing portion of the skin portion 15 so as to be exposed from the skin portion 15. . The skin portion 15 is white, and the line portion 17 is red. For the skin portion 15 and the line portion 17, for example, a polyamide resin is used.

Next, the configuration of the display unit 109 will be described with reference to FIG. The display unit 109 includes a base portion 102 made of a blue urethane-based resin, a display body 104 made of a transparent polyamide resin, and a cover 106 made of a transparent polycarbonate or a urethane-based resin. The base 102 has a slightly higher flexibility than the cover 106.
The base part 102 has a disk part 102a, and a flange 102b is formed at the lower end of the outer peripheral part of the disk part 102a. As shown in FIGS. 10 and 11, columnar bosses 102c and 102d are formed on the back surface of the disk portion 102a, and the boss 102c is closer to the center of the disk portion 102a and the boss 102d is closer to the outer peripheral portion. In a different position. The boss 102c is longer than the boss 102d and has a larger diameter.

In the present embodiment, a red character 104a and a yellow pattern 104b are printed on the surface of the thin substantially disc-shaped display body 104. As described above, the characters 104a and the like can be displayed on the display body 104 by printing, so that vivid coloring can be easily applied. The upper end of the display body 104 has a shape in which a part of an arc is removed, and a straight portion 104c is formed in this part.
A concave portion 106a is formed on the back surface of the cover 106, and the concave portion 106a has two steps. The concave portion 106a is formed in a shape that fits exactly on the upper surface of the base portion 102, and the cover 106 has a disk portion 106c and a flange 106b corresponding to the concave portion 106a.

  In the display unit 109, the display body 104 is placed on the disk unit 102 a of the base unit 102, the cover 106 is put on the display unit 104, and the concave portion 106 a of the cover 106 fits on the upper surface of the base unit 102. It is configured. The display body 104 is placed at a correct position on the disk portion 102a with reference to the positions of the straight portion 104c, the boss 102c and the boss 102d. As described above, since the base portion 102 has a slightly higher flexibility than the cover 106, the cover 106 is fitted so as to slightly compress the base portion 102. Therefore, the cover 106 fits into the base portion 102 so as not to come off easily.

  Next, a method of manufacturing the boring pin 101 will be described. First, the core material 103 is manufactured in advance. That is, as shown in FIG. 12, cores 123 and 125 capable of forming an upper hole 105a and a lower hole 105b are set in a mold 121, and a synthetic resin is injected into a cavity 27 through a gate 26 to form a core material. 103 is formed.

With the core 125 set, step portions 6 and 8 are formed in the middle of the upper hole 105a of the core material 103. The step 6 is formed near the bottom of the upper hole 105a, and the step 8 is formed near the upper opening 107a (see FIG. 12).
Further, since the protruding ridge 29 is formed over the outer periphery of the base end portion of the core 123, the concave ridge 31 is formed on the inner peripheral surface of the lower end portion of the lower hole 105b. Also, since the convex portions 122 and 124 protruding from the cavity 27 are formed in the mold 121, small holes 133 and 134 are formed on the outer peripheral surface of the core member 103 (see FIG. 13). The small holes 133 and 134 correspond to the bosses 102c and 102d of the display unit 109, and the diameter of the small hole 133 is formed larger than the diameter of the small hole 134.

Next, the core material 103 is taken out of the mold 121, and the cap 9 is driven into the upper hole 105a from the upper opening 107a of the core material 103 as shown in FIG. The bosses 102c and 102d of the display unit 109 are fitted into the small holes 133 and 134, respectively, and the display unit 109 is fixed to the core 103. As described above, since the boss 102c and the boss 102d are different in length and diameter, the boss 102c cannot be fitted in the small hole 134. Therefore, the display unit 109 is always attached to the core member 103 in a correct posture.
As shown in FIG. 14, the core material 103 into which the cap 9 is driven and the display unit 109 is fixed is set in the mold 47, and the iron bar 41 is inserted into the round hole 37 of the cap 9 to fix the core material 103. Since the core material 103 is fixed by the iron bar 41, the height of the boring pin 101 can be reliably controlled.

  The mold 47 is provided with a cavity 49 for forming the skin 15, and the polyamide resin is injected into the cavity 49 via the gate 51 to form the skin 15 (see FIG. 15). The cap 9 is covered with a skin portion 15, and two concavities 52 having a thin skin portion 15 are formed in a narrow portion of the core 103.

  When a polyamide resin is used for the skin portion 15, the inside of the cavity 49 is pressurized at a high resin temperature of 250 ° C. or higher, and since the cap 9 is fitted into the upper hole 105a, the core material 103 is It can be reliably manufactured into a predetermined shape specified by international standards without deformation.

When the skin portion 15 is formed, in the display portion 109, the flange 106b is covered with the skin portion 15, and only the disk portion 106c is exposed (the display body is an exposed portion exposed from the skin portion). As described above, since the base 102 and the cover 106 of the display unit 109 are formed of polycarbonate or urethane-based resin having elasticity, they are curved along the curved surface of the skin portion 15. Further, only the flange 106b of the display unit 109 is covered by the skin portion 15 (that is, the flange 106b is a buried portion provided on the outer periphery of the exposed portion and buried in the skin portion formed one step lower than the exposed portion). Therefore, the blue base portion 102 is visible through the edge 106d of the transparent disk portion 106c (it is blue in the present embodiment, but at least the surface of the base portion on the side where the display is arranged) is colored. Therefore, when the display unit 109 is viewed from the front, a blue ring is visually recognized at the edge 106d.
As described above, since the display body 104 of the display unit 109 is covered with the cover 106, the display body 104 does not disappear and disappear like a display unit formed by painting.

  Next, as shown in FIG. 16, the core material 103 on which the skin portion 15 is formed is set in a mold 53, and a red polyamide resin is injected into the concave portion 52 through a gate 55, and is formed by so-called two-color molding. The book line portions 17 are formed. Since the line portion 17 is formed of the synthetic resin filled in the concave portion 52, the line portion 17 does not disappear and disappear like the line portion formed by painting.

The core material 103 formed on the skin portion 15, the line portion 17 and the like as described above is removed from the mold 53, and the cap 59 is inserted into the hole 57 formed after the iron bar 41 is pulled out. It is driven into the hole 37 (see FIG. 17). The protrusions 60 formed on the outer peripheral surface of the cap 59 are fitted into the concave portions 62 formed on the inner peripheral surface of the round hole 37, so that the cap 59 is prevented from coming off.
Further, the cap 13 is driven into the lower opening 107b, and the convex portion 14 of the cap 13 is fitted into the recess 31 formed on the inner peripheral surface of the lower hole 105b, so that the cap 13 is prevented from coming off. The head 16 of the cap 13 comes into contact with the lower surface of the core 103. Thus, the boring pin 101 is completed.

Although the embodiment of the present invention has been described in detail above, the specific configuration is not limited to this embodiment, and even if there is a change in the design without departing from the gist of the present invention, the invention is not limited to the embodiment. included.
For example, in the second embodiment, the base portion 102 and the cover 106 are made of polycarbonate or urethane-based resin, but the present invention is not limited to this, and may be made of another synthetic resin. Further, the display body 104 can be made of not only the polyamide resin but also another synthetic resin, paper, or the like.

Further, another embodiment of the display unit 109 will be described. 18 is a plan view for explaining a display unit according to another embodiment, FIG. 19 is a cross-sectional view taken along line AA of FIG. 18, and FIG. 20 is a cross-sectional view taken along line BB of FIG. It is.
As shown in FIGS. 18 to 20, in the present embodiment, the display unit 109 includes a curved transparent plate 206, a display body 204 attached to the back side thereof, and bosses 202c and 202d.
The transparent plate 206 is formed so as to be curved so as to have a shape along the circumferential direction of the bowling pin, and a display body 204 on which characters and patterns are printed is adhered to the back side thereof via a transparent adhesive. I have. As a material for forming the transparent plate 206, a transparent resin such as polycarbonate is used.
Examples of a material for forming the display body 204 on which characters and patterns are printed include a sheet-like material such as a plastic film or paper.
In the present embodiment, the bosses 202c and 202d are each formed in the shape of a protrusion on the back side of the transparent plate 206, one by one. Is fixed to the core member 103.
The display 204 may be omitted by directly printing the characters and patterns printed on the display 204 attached to the back side of the transparent plate 206 on the back side of the transparent plate 206.

According to the boring pin according to the present invention, the material used as the core material is a synthetic resin having good injection moldability, rigidity, impact strength, hardness, low cost, and excellent recyclability, and a material used as a skin portion. Is characterized by the use of a synthetic resin that is more excellent in friction and wear resistance, impact resistance, and hardness than the core material, and thus can be used for an extremely long time.
Further, in the bowling pin according to the present invention, it is not necessary to apply a primer, a clear coating, or the like to the upper layer of the skin portion. Since the synthetic resin of the skin portion is extremely hard and has excellent scratch resistance, friction and wear resistance, impact resistance, and the like, the surface of the skin portion can be kept clean without any treatment.
Further, since the core material is formed of a polypropylene resin and the skin portion is formed of a polyamide resin, the core material is excellent in durability and recyclability.
ADVANTAGE OF THE INVENTION According to the boring pin which concerns on this invention, a skin part or a display part does not come off even if it receives an impact or friction, high durability can be obtained, and the cost in using a boring pin is reduced. Becomes possible.

It is a front view of the bowling pin concerning a 1st embodiment of the present invention. It is an explanatory view for explaining the manufacturing process of the boring pin according to the first embodiment of the present invention. It is a partially broken perspective view of the core material which forms the boring pin shown in FIG. It is an explanatory view for explaining the manufacturing process of the boring pin according to the first embodiment of the present invention. It is an explanatory view for explaining the manufacturing process of the boring pin according to the first embodiment of the present invention. It is an explanatory view for explaining the manufacturing process of the boring pin according to the first embodiment of the present invention. It is an explanatory view for explaining the manufacturing process of the boring pin according to the first embodiment of the present invention. It is a front view of the bowling pin concerning a 2nd embodiment of the present invention. It is an exploded perspective view of a display provided in a bowling pin according to a second embodiment of the present invention. It is a front view of a display provided in a bowling pin according to a second embodiment of the present invention. It is AA sectional drawing of FIG. It is explanatory drawing for demonstrating the manufacturing process of the boring pin which concerns on 2nd Embodiment of this invention. FIG. 9 is a partially cutaway perspective view of a core constituting the boring pin shown in FIG. 8. It is an explanatory view for explaining a manufacturing process of a boring pin according to a second embodiment of the present invention. It is an explanatory view for explaining a manufacturing process of a boring pin according to a second embodiment of the present invention. It is an explanatory view for explaining a manufacturing process of a boring pin according to a second embodiment of the present invention. It is an explanatory view for explaining a manufacturing process of a boring pin according to a second embodiment of the present invention. FIG. 9 is a plan view for explaining a display unit according to another embodiment of the present invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Boring pin 3 Core material 5 Hollow part 7 Upper opening 9 Cap 11 Lower opening 13 Cap 15 Skin part 16 Head part 17 Line part 19 Character part 21 Mold 23, 25 Core 24 Convex part 26 Gate 27 Cavity 29 Convex part 31 concave streak 33 small hole 35 head 37 round hole 39 mold 41 iron bar 43 cavity 45 gate 47 mold 49 cavity 51 gate 52 recess 53 mold 55 gate 57 hole 59 cap 60 convex portion 62 concave portion 101 boring pin 102 base portion 102a Disk portion 102b Flange 102c, 202c Boss 102d, 202d Boss 103 Core material 104, 204 Display body 104a Character 104b Pattern 105a Upper hole 105b Lower hole 106 Cover 106a Recess 106b Flange 106c Disk portion 107a Upper opening 107b Lower opening 109 Display 121 mold 123,125 core 122,124 convex part 206 transparent plate

Claims (15)

  A boring pin comprising: a core material having a hollow portion formed of a synthetic resin; and a skin portion formed on a surface of the core material and made of a synthetic resin having higher impact resistance than the core material.   The boring pin according to claim 1, wherein the synthetic resin of the core material is polypropylene, and the synthetic resin formed on the surface of the core material is a polyamide resin.   The boring pin according to claim 1, wherein the surface layer of the skin portion is not further coated.   The bowling pin according to claim 1, further comprising a base, a display provided on the base for displaying characters, patterns, and the like, and a transparent portion that covers the display and allows the characters, patterns, and the like of the display to be seen through. A boring pin characterized in that a display portion constituted by a cover connected to a base portion is embedded in a skin portion with a part thereof being exposed.   5. The boring pin according to claim 4, wherein the base portion and the cover are formed in a fitting structure.   6. The boring pin according to claim 4, wherein the synthetic resin forming the base portion has higher flexibility than the synthetic resin forming the cover.   The boring pin according to any one of claims 4 to 6, wherein the display body is buried in an exposed portion exposed from a skin portion and a skin portion provided on an outer periphery of the exposed portion and formed one step lower than the exposed portion. A boring pin having a buried portion.   The bowling pin according to any one of claims 4 to 7, wherein at least a surface of the base portion on which the display body is arranged is colored. 2. The boring pin according to claim 1, wherein the display unit comprises: an exposed portion exposed from a skin portion; and a buried portion provided on an outer periphery of the exposed portion and buried in a skin portion formed one step lower than the exposed portion. Have
The display unit has a curved transparent plate and a display body stacked on the back side thereof,
The transparent plate is formed by being curved so as to have a shape along the circumferential direction of the bowling pin,
A boring pin, wherein a part of the display portion is embedded in a skin portion in a state of being exposed on a surface of the boring pin.   The boring pin according to claim 9, wherein the display body is omitted by directly printing characters or patterns printed on the display body stacked on the back side of the transparent plate on the back side of the transparent plate.   A synthetic resin serving as a core material having a hollow portion is formed by an injection molding method, a deformation preventing material is fitted into the hollow portion from an opening of the core material, and the core material is set in a mold. A method for manufacturing a boring pin, comprising forming a skin portion made of a synthetic resin having higher impact resistance than a core material on a surface of the material.   12. The boring pin manufacturing method according to claim 11, wherein a display portion is formed on a surface of the core before forming the skin portion, and the skin portion is formed so that the display portion is exposed. Pin manufacturing method.   The method for manufacturing a boring pin according to claim 11, wherein a concave portion is formed in a skin portion, and a display body is formed of a synthetic resin in the concave portion. The method of manufacturing a boring pin according to claim 11, wherein the display unit has an exposed portion exposed from a skin portion, and a buried portion provided on an outer periphery of the exposed portion and buried in a skin portion formed one step lower than the exposed portion. Section and
The display unit has a curved transparent plate and a display body laminated on the back side thereof,
The transparent plate is formed by being curved so as to have a shape along the circumferential direction of the bowling pin,
A method of manufacturing a boring pin, characterized in that a part of the display section is embedded in a skin portion while being exposed on a surface of the boring pin. A mold for manufacturing the boring pin according to claim 1,
A mold set, characterized in that the inner surface of the mold for forming the core material has a rough surface, and the inner surface of the mold for forming the skin portion has a mirror surface.

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