Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
This article describes an attachment tool which provides a permanent and accurate indication of the amount of torque applied while tightening nuts and bolts (Fig. 1). A two-part film, available from G. T. Technology in Southfield, Michigan, is attached to the nut or bolt with an adhesive backing and serves to display the applied torque (see Fig. 2). (Image Omitted) The film, shown in Fig. 3, consists of chemically-filled microcapsules of various sizes. Larger capsules are broken by relatively weaker applied forces, while smaller ones require stronger forces for breakage. Upon application of pressure, the microcapsules on the A-film are broken and the released color forming material reacts with the color-developing material to produce a mark on the B-film.