Patent ID: 9138906
Filing Date: 2015-09-22
Classification: B26D,B28B,B31B,B31F,E04F

Abstract:
1. A scoring device of a whetstone type for a gypsum board production machine having a rotary blade and a backing block stationarily positioned under the rotary blade and having an upper flat surface, comprising: a space for downward deformation of the sheet of paper for gypsum board liner, which is formed in the backing block and which opens on the upper flat surface of the backing block, and tensioning means for stably imposing tension on the sheet traveling on the upper flat surface of the block, wherein a blade edge of the rotary blade scrapes an upper surface portion of a sheet of paper for gypsum board liner traveling under tension, the upper flat surface of the backing block abuts against a lower surface of the sheet for the travelling of the sheet, a score is continuously ground on the sheet by the blade edge, an opening of the space has an edge defining the space on the upper flat surface and is located immediately under the rotary blade made of whetstone, so that a part of the sheet to be ground is downwardly released by the opening, and the backing block and the blade edge are so positioned as to cause the sheet under tension to be slightly bent downward in a range of the opening for keeping intimate contact between the blade edge and the upper surface of the sheet throughout an angular range of a predetermined central angle (β) about a rotational center axis of the rotary blade and maintaining a grinding action of the blade edge on the upper surface portion of the sheet in the angular range, so that said upper surface portion is scraped from the sheet of paper to make a groove on the upper surface of the sheet while making a folding line protruding from a lower surface of the sheet in said range of the opening, by the grinding action of the blade edge, wherein the central angle is set to be in a range from 10 degrees to 90 degrees.