Pneumatic cord and yarn grips provide a convenient method for clamping fiber, cord, yarns and fine braided wires to reduce the problem of jaw breaks associated with testing these materials.
A specially designed horn with a smooth finish and a contoured surface with a graduated cam allows for easy loading and a stress reduced clamping area on the specimen.
The clamping mechanism can be activated either automatically or through a foot switch. This allows hands-free grip operation enabling the specimen to be held with both hands, for easy loading.
Pneumatic cord and yarn grips provide selectable clamping force to accommodate different materials and excellent follow-up action which compensates for decay of the holding force due to specimen creep.
Principle of Operation
Where the gripping area of mono-filaments, cord and yarn is small in relation to the strength, normal techniques using standard grip faces usually result in specimen failures adjacent to the jaw faces.
The pneumatic cord and yarn grips have been designed specifically to overcome the problem of specimen failure by incorporating a capstan design which evenly distributes the gripping force over the surface of a curved half capstan through friction.
In addition, the pneumatically cushioned gripping force applied to the ends of the specimen compensates for the decay of force due to specimen creep.The pneumatics activate a moveable face, which acts upon a contoured fixed gripping face. This serves as a capstan and provides support for the specimen, making the transition from the free stressed length of specimen to the rigidly clamped portion gradually rather than abruptly, thus minimizing breakage of the specimen adjacent to the jaw face. The capstan also incorporates a polished guide horn, which assists in rapid specimen loading. The polished finish prevents damage to individual fibres during specimen insertion.
The specimen is placed over the top of the horn and slides down to the proper gripping position on the contoured clamp. The grips may be closed or opened by a pneumatic footswitch for hands free operation. An automatic air kit is also available for hands free, automated, and pretension testing via software or system default settings.