To reduce residual distortion, improve seismic tracking ability and mounting work, and reduce cost, by using as an elastic material a rubber composition containing a rubber component and metal salt of α, β unsaturated carboxylic acid.
A base material rubber of an elastic washer 1 contains various diene-based rubber, the other rubber component, preferably cis-1,4-polybutadiene rubber, and natural rubber, polyisoprene rubber, or mixture of them as further rubber component. A metal salt of α, β unsaturated carboxylic acid, especially preferably used ethylenic unsaturated carboxylic acid is a metal salt of (meta) acrylic acid or crotonic acid, and its mixing amount is 10-100 pts.wt. to 100 pts.wt. of the rubber component. The structure discussed above reduces residual distortion than a washer made of conventional rubber composition, prevents occurrence of looseness, softens this washer, allows tracking even when opening is large, and increases compression elastic coefficient by 10% to improve fastening efficiency.
TAJIMA HIROSHI
HAYASHI SHINJI
