1. Field of the Invention
This invention relates to a manufacturing apparatus and method for golf ball with which rubber string is wound on a core sphere to obtain a wound-string core.
2. Description of the Related Art
Conventionally, a wound-string golf ball is manufactured as that rubber string is wound on a core sphere composed of solid rubber or a core sphere formed by filling a rubber bag with liquid material of fluid or paste to form a wound-string core, and the wound-string core is coated with a cover.
As a method to wind the rubber string on this core sphere (so-called center), a method, in which the core sphere is held by plural winding rollers, at least one of the winding rollers is driven to rotate the core sphere and supply the rubber string onto the surface of the core sphere to wind the rubber string on the core sphere, is widely adopted. It is necessary to extend and wind the rubber string on the core sphere to improve hardness and resiliency of the core sphere. As a rubber string extending means, a means disclosed by Japanese Patent Publication No. 3-52312 is known.
In this rubber string extending means, provided with a pair of pre-supplying rollers, disposed on an upstream side of an upper winding roller and a lower winding roller holding the core sphere and winding the rubber string, and elastically pushed as to tightly contact each other, a main supplying roller supplying the rubber string to the upper and the lower winding rollers, and a guiding pulley attached to the main supplying roller, the rubber string going between the pair of pre-supplying rollers is hitched to the guiding pulley, and the rubber string is supplied to the core sphere held by the upper and lower winding rollers after the rubber string is led to go along a peripheral face of the main supplying roller to add tensile force.
On the other hand, as the winding roller, a winding apparatus of Japanese Patent No. 2572802 is known. That is to say, this winding apparatus, provided with a pair of cylindrical rollers arranged to be movable in an axis direction back and forth and rotatable, a concave roller, composed of a central roller portion and a pair of tapered roller portions rotatable independently on both sides of the central roller portion, disposed above the cylindrical rollers, and a control device, is constructed as to hold the core sphere with the pair of cylindrical rollers and the concave roller, and oscillate and rotate a spherical body (a core sphere or a wound-string core) to wind the rubber string at random by rotating with moving the cylindrical rollers back and forth.
In this case, to uniformly wind the rubber string on the spherical body, angular speed of the rotation of the spherical body is calculated from circumferential speed of the cylindrical roller and diameter of the spherical body, and reciprocation of the spherical body is controlled by the control device as angular speed of the oscillation of the spherical body is equal to that of the rotation of the spherical body. That is to say, even if the circumferential speed of the cylindrical roller is constant, the angular speed of the rotation of the spherical body is decreased along with increase of the diameter of the spherical body. So the reciprocation of the cylindrical roller is controlled to be short when the diameter of the spherical body is small and to be long when the diameter of the spherical body is long to control the oscillation of the spherical body. And, measurement of the diameter of the spherical body is conducted by detecting vertical displacement of the concave roller with a differential trans displacement gauge, and input of the detected value into the control device through an amplifier, a filter, an A/D converter, etc.
However, (the above-described) conventional rubber string extending means can not add stable tensile force (tension) to the rubber string because the pair of pre-supplying rollers, disposed on the upstream side of the main supplying roller, have point-contact with the rubber string, tension defects frequently occur (about 30%), and ununiform hardness of the rubber string layer wound on the core sphere and break of the rubber string are frequently generated thereby.
And, in the above-described winding apparatus of Japanese Patent No. 2572802, construction is extremely complicated and faults are easily caused, and cost is high for the expensive apparatus itself. And, talc, etc., to prevent the rubber strings from adhering each other, is scattered in the winding and tending to clog between the central roller portion and each of the tapered roller portions of the concave roller, and frequent maintenance is required.
It is therefore an object of the present invention to provide a manufacturing apparatus for golf ball having simple construction and hardly broken and a manufacturing method for golf ball, with which the problems above are solved, tension defect is improved, break of the rubber string is reduced, quality of the wound-string core is improved, and wound-string golf balls having good sphericity are mass-produced with low cost.