JPS6238185A - Exercise ball for baseball - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a practice baseball ball made of a polyolefin resin foam.

More specifically, by controlling the expansion ratio and foaming state of the foam-molded sphere, and by adjusting the compressive deformation load and repulsion properties of the sphere to a specific gloss, not only will it not tear, crack, deform, etc. A practice baseball that makes it possible to adjust the flight distance and the sound produced when hitting as close as possible to the true sound of a hardball baseball, and is light and safe, and does not damage glass or property. Regarding a baseball that is safe even if it hits the human body directly.

[Prior Art 1] Conventionally, it has been impossible to conduct baseball batting practice in satisfactory conditions at an indoor practice field, gymnasium, or indoors, and it has been particularly difficult to practice on rainy days or in the gymnasium with people from other clubs. There is a problem in that it is not possible to practice batting sufficiently or during the off-season in snowy regions, and a solution to this problem is desperately needed.

As a means of solving the above problems, attempts have been made to make practice balls by making synthetic resin or foaming it.

For example, JP-A-57-57568, JP-A-56-161
No. 066, Japanese Utility Model Application Publication No. 54-118268, and Japanese Utility Model Application Publication No. 56-11863 have been proposed.

However, in JP-A-57-57568, the structure is constructed by coating the outer periphery of a core core such as cork or rubber with rubber, and further providing a shell layer made of crosslinked vinyl chloride resin. It is not possible to practice batting indoors, causing damage to equipment and safety issues.
Moreover, it does not have the durability to withstand repeated use.

Also, Japanese Unexamined Patent Publication No. 56-161066, Utility Model Application No. 54-1
The one disclosed in Japanese Patent No. 18268 is made of polyurethane resin, and the flying distance is long, and the hitting sound is not sufficient.

Furthermore, Japanese Utility Model Application Publication No. 56-11863 discloses a foam ball integrally molded with a thermoplastic resin, and in all of the examples, a soft thermoplastic resin, that is, a rubber-based polymer is used. , the flight distance of the ball is greater,
In addition, products that may cause damage to equipment are used, and it cannot be said that the results are satisfactory, and they have not been adopted for actual baseball practice such as professional baseball, amateur baseball, and high school baseball. is the current situation.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks, has durability, and adjusts the flight distance when hitting and makes the sound generated when hitting close to the true pitch sound of a hardball baseball. To provide a practice baseball ball that is comb-friendly and highly safe.

[Means for Solving the Problems] The ball of the present invention is a spherical integrally foamed product made of a polyolefin resin and has an expansion ratio of 20 to 30, and is uniformly foamed from the center to the surface of the molded sphere. The following (a) has the same diameter as a hardball baseball ball composed of cells and whose surface layer is composed of a skin layer with a thickness of 20 to 60 μm.
To provide a practice baseball that satisfies (b).

(a) Compressive load 15-25Kg (Load when the molded sphere is compressed to 50% of its diameter (radius)) (b) Repulsion 25-401 [However, the height 100iff above the concrete floor surface It is expressed by 1) the maximum height at which a ball can bounce from a free fall. ] The polyolefin resin of the present invention includes low-density, medium-density, and high-density polyethylene, polypropylene, polybutene-1, etc. homopolymers, ethylene-propylene copolymers, ethylene-butene-1 copolymers, ethylene-1, etc. Copolymers of ethylene or propylene with other α-olefins such as hexene-1 copolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic Examples include acid copolymers, Eblene-ethyl acrylate copolymers, copolymers of ethylene and polar group enomers such as ionomer resins, polyethylene graft copolymerized with styrene monomers, and mixtures thereof.

Among the above materials, low-density polyethylene and those obtained by grafting styrene thereto are preferred in terms of impact resistance and the like.

The melt index of the above polyolefin resin is 0.
01~30! ? /10 minutes, preferably Hao, 1-20g/
Selected within 10 minutes.

In the present invention, it is important to use a spherical integrally foamed product made of the above-mentioned polyolefin resin with an expansion ratio of 20 to 30, and by making it a spherical integrally foamed product, the durability during impact is improved. When the foaming ratio is less than 20 times,
There is a concern that some durability will deteriorate, and if it exceeds 30 times,
The application range of repulsion and compressive deformation load described later cannot be satisfied, which has a negative impact on the feeling of use, flight distance, etc.

Furthermore, in the present invention, the cells of the internal foam of the molded sphere are regulated. That is, the surface layer from the center of the molded sphere is composed of uniformly expanded cells, and the surface layer is composed of a skin layer with a thickness of 20 to 60 μm, and the compressive deformation load is 15 to 25 K! J, IIIP with repellency ranging from 25 to 40 Cta! It is a baseball for baseball.

The purpose of making the above foam into a uniform foam cell is to eliminate the presence of an uneven internal density layer (uneven distribution of the center of gravity) and maintain the linearity of the ball's flight trajectory (preventing the ball from wandering). .

On the other hand, the presence of a skin layer with a thickness of 20 to 60 μm in the surface layer is necessary in order to approximate the true pitch sound of a hardball baseball as much as possible due to the correlation between the foaming ratio, the repulsion properties described below, and the compressive deformation load. It also greatly improves durability.

Furthermore, the reason why the compressive deformation load is 15 to 25 K9 and the repulsion is 25 to 40 C is the above-mentioned impact feeling, that is,
It is preferable to fall within this range in order to approximate the true pitch sound of a hardball baseball as much as possible. In addition, in order to control flight distance, the repulsion is set in the range of 25 to 40 Cts.

Further, the foam of the present invention is preferably the same size as a hardball baseball for batting practice.

In particular, the foam ball of the present invention produces a sound similar to the sound of a true ball when the ball is hit with the bat, so players can enjoy batting while determining whether or not they hit the ball with the bat during practice. .

Furthermore, in the present invention, the ball may be colored if necessary, and within the scope of the gist of the present invention.
The combination of other additives, pigments, fillers, etc. and the core body are
One person may do it.

[Examples] The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples without departing from the gist of the present invention.

4/ili Examples 1 to 2 and Comparative Examples 1 to 3 Low-density polyethylene [Product name Nippon Seki Xuron F41, Nippon Petrochemical ■
Using Freon as a foaming agent, foam beads with a diameter of about 5 to 6 TrL/TrL are created by foaming mini pellets (cylindrical shape with a diameter of 1.0 m and a length of 2.0 m)] to a desired expansion ratio. Fill a ball mold with foamed beads and use heated steam to heat the beads at a temperature of 110 to 150°C and a pressure of 1.2 to 2.
．． A ball of the same size (approximately 7.2 ci+ in diameter) as a uniformly foamed hardball was obtained by integrally molding the ball in a range of 0 kg/ci, consisting of a surface skin layer with a thickness of 40 μm, and uniformly foamed.

Table 1 shows the results of various tests conducted using the ball.

Table 1 Using the same foamed beads as in Example 1, foamed layers with different expansion ratios were sequentially laminated, varied unevenly in the radial direction (concentric spherical shape), and integrally molded.The thickness of the surface skin layer was 4
A continuous layer of 0μ skin was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 In the same manner as in Example 1, uniformly foamed integrally molded products were produced with the expansion ratio fixed at 24 times and the surface skin layer varied, and the results of evaluation in the same manner as in Example 1 are shown in Table 3. Indicated.

A spherical synthetic rubber with a diameter of 3 cttr is used as the third surface core material, and the surrounding area is covered with a foam made of low density polyethylene used in Example 1'C- with a foaming ratio of 24 times and a surface skin layer of about 40 μm. When a ball with the same diameter as a hard ball was manufactured and used for batting practice, it was found that after several uses, the ball began to peel at the boundary between the core material and the foam, resulting in a poor feel when using the ball, especially when hitting the ball. .

(-R) Using the low-density polyethylene of Example 1, hemispherical foams with a foaming ratio of 24 times were molded, and these were welded to produce a ball, and the feel of the ball was evaluated. Although there is not much difference from the ball of Example 1, fluctuations are observed in the flight trajectory after being hit.

Comparative Example 13 Polystyrene resin as resin [Product name: Sudiro Ball J
Q-300, manufactured by Mitsubishi Yuka Co., Ltd.] was used to mold the same balls as in Example 1, and the feeling of use was examined. It was of inferior quality.

The test method is as follows.

(Test method) (1) Compression deformation load (K3) The ball is compressed using a compression jig (load cell), and the compression force is expressed as the required compression force when the ball is compressed to 50% of the ball diameter.

(2) Repulsion (cttr) It is expressed as the maximum height (cm) at which a ball bounces when it falls freely from a height of 100 cm above a concrete floor surface.

(3) Evaluation of durability Even after being hit more than 100 times, no damage such as deformation, damage, or falling off of small pieces was observed. → Changes such as deformation, injury, and small pieces falling off occur after 0.10 hits.
→ △After several blows, changes such as deformation, injury, or falling off of small pieces occur. → × (4) Feeling of use (g. Discrimination during repeated batting) A. Feeling of hitting When a tossed ball is fully swung with a normal bat, the feeling of whether or not it is possible to sufficiently determine whether the hitting is good or bad. Pointing to
The reaction force transmitted to the hand when hitting and the hitting sound are at a satisfactory level, and the above-mentioned reaction force and hitting FX can be clearly determined by the practitioner depending on the poor hitting condition such as the hitting point being deviated from the center of the ball. Optimally, it changes as the time progresses.
→ ○Does not make a true pitch sound when hitting the true heart with the bat. → × B. Flight distance: Judgment of the quality of the above-mentioned batting. The distance that can be practiced in a small space is set at 3 to 1077 LP1 degree, and a flight distance within that range is considered optimal.

Evaluation Less than 3TrL → ×3~10T
rL → 0 10-12m → Δ 13m or more → X Optimize the condition so that the body does not feel a shock when receiving a direct hit from a relatively high-velocity ball before the danger sensitivity velocity suddenly decreases by %. make it a thing. →O Feels a sense of impact →× [Operations and effects of the present invention] As mentioned above, the functions and effects of the baseball of the present invention are as follows: (1) No tearing, cracking, deformation, etc., and no durability. Get lost.

(2) It is lightweight, does not damage glass or equipment, and does not cause injury even if it hits the human body directly, and is highly safe.

(3) When the sound generated when hitting the ball captures the true heart of the ball, it approximates the true pitch of a hardball baseball, making it possible not only to determine whether the hit is good or bad, but also to make it sound like the real ball. You can taste the feeling.

(4) Since the distance of the ball is short and there is no danger, it can be used in narrow spaces such as inside gymnasiums and indoors.

(5) There is no fluctuation in the flight trajectory.

(6) It is inexpensive.

Claims (2)

[Claims] (1) Foaming ratio made of polyolefin resin: 20-3
The following (1) is a 0x spherical integral foam molded product, which is composed of uniformly foamed cells from the center to the surface layer of the molded sphere, and the surface layer is composed of a skin layer with a thickness of 20 to 60 μm. a) to (b) A practice baseball that satisfies (a) compressive deformation load of 15 to 25 kg (b) repulsion of 25 to 40 cm. (2) The practice baseball ball according to claim 1, wherein the polyolefin is low density polyethylene.