Manufacturing apparatus and method for golf ball

A manufacturing method for a golf ball, which comprises:

• holding a core sphere or a wound-string core in a pair of 34 mm to 42 mm diameter bottom rollers and a pair of concave top rollers having a minimum diameter of 15 mm to 35 mm at a central portion;
• rotating and reciprocating the bottom rollers in an axis direction so as to move opposite to each other to rotate the core sphere or wound-string core;
• winding rubber string;
• and
• pressurizing the core sphere or wound string core intermittently by the pair of top rollers with predetermined pressure to obtain a wound string core of a predetermined diameter, wherein
• a rotation frequency of the bottom rollers is 1100 rpm to 2000 rpm, a ratio of rotation of the bottom roller to reciprocation of the bottom roller is 10:15 to 15:10, and a ratio of pressurization of the top roller to reciprocation of the bottom roller is 1:14 to 1:5;
• a reciprocating rotational driving mechanism reciprocates and rotates the bottom rollers, wherein
• the reciprocating rotational driving mechanism is provided with an input shaft having a pair of cam portions and is driven to rotate around a lateral axis;
• a turning shaft in the lateral axis direction disposed behind the input shaft;
• a pair of ring members, one of the ring members being fitted to one of the pair of cam portions, an other of the ring members being fitted to an other of the pair of cam portions, each of the ring members being fitted to each of the corresponding cam portions so as to freely slide;
• an attachment member attached to a first protruding piece on the turning shaft so as to freely oscillate;
• a connecting member connecting the ring member and the attachment member;
• a bottom roller shaft in the longitudinal axis direction, a front end of which is connected to a bottom roller;
• a holding member holding another end of the bottom roller shaft so as to freely rotate;
• a crank member, a front end of which is attached to the holding member and a rear end of which is attached to a second protruding piece on the turning shaft;
• an output shaft fitted to the bottom roller shaft;
• a plurality of gears transmitting torque from the input shaft to the output shaft;
• a rotational force transmitting mechanism transmitting the torque from the output shaft, allowing the bottom roller to move back and forth;
• and
• one of the cam portions and the other of the cam portions are directed opposite for 180° each other.