Importance

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Abstract

A method and apparatus (10) for fastening upper and lower workpieces (20, 22) without movement of the workpieces. The apparatus is provided with a frame having upper and lower portions (24.1, 24.2) carrying upper and lower riveting ram assemblies (26, 28), respectively. Each riveting ram assembly includes a buck ram (30 or 32), a buck ram moving assembly (62 or 90, 92), a pressure foot (34 or 36), a pressure foot moving assembly (38 or 40), a buck ram position measuring device (74 or 104), and a pressure foot position measuring device (78 or 108). The upper pressure foot moving assembly (38) further includes an upper pressure foot compensation cylinder assembly (42). The apparatus also includes a load cell (112) carried by one of the buck rams for sending a force signal in response to the force being applied to the fastener during upset and thereafter. A programmable process controller (82) is provided which is capable of having programmed into it the length of a fastener, and a deflection compensation table which sets forth the deflection of a portion of the frame during upset. The controller modulates sequential operation of the various moving assemblies during operation to move the buck rams and the pressure feet in response to signals received from the position measuring devices and the load cell in such a manner that the fastener may be upset while maintaining the upper surface (122) of the upper workpiece (20) in a desired workplane (124) even though one portion of the frame may deflect more than another portion of the frame.

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First Claim