Patent ID: 7727437
Filing Date: 2010-06-01
Classification: B29C,B29L

Abstract:
1. A method of manufacturing golf balls comprising a core and one or more cover layer which encloses the core, at least one cover layer being a thin layer made of a synthetic resin material having a thickness of 1.0 mm or less, which method is characterized by forming the thin layer on a surface of a core or spherical body by a process that includes steps (i) and (ii) below: (i) holding within a mold cavity the core or a spherical body composed of the core enclosed by a cover layer and injecting a synthetic resin material into a space defined by a surface of the core or spherical body and an inner face of the mold cavity so as to form a cover layer on the surface of the core or spherical body; and (ii) grinding the cover layer formed in step (i) to a thickness of 0.1 mm or more using a grinder comprising a cylindrical grinding tool which rotates on a shaft and has a periphery on which are formed a plurality of circumferential grooves, each corresponding in shape to the curved surface of a spherical workpiece to be ground, the grooves being arranged axially with respect to the rotary shaft, and comprising also a cylindrical restraining tool which is disposed parallel to the grinding tool and rotates on a shaft, the grinder being constructed so as to grind spherical workpieces placed between both tools by rotating the grinding tool and the restraining tool in the same direction, conferring a peripheral speed ratio therebetween, and at the same time causing the restraining tool to oscillate axially with respect to the shaft thereof, wherein the grinding tool rotates at a speed of 2000 to 3000 rpm, the restraining tool rotates at a speed of 100 to 300 rpm, and the peripheral speed ratio is from 20 to 69, and wherein the restraining tool is made to oscillate at an amplitude of 2 to 10 mm and a speed of 30 to 120 cycled per minute.