The use of cable ties to bundle a plurality of wires or similar articles has long been known. Basic cable tie construction includes an elongate cable tie strap having a tail at one end and a head at the other end. The head includes a central passage or aperture therethrough for accommodating a tail in an insertable fashion. The head supports a locking device adjacent the head aperture to securely lock the cable tie body within the aperture of the head to provide securement of the cable tie about the bundle of wires. In one type of cable tie construction, the locking device is a flexibly supported integrally formed pawl having plastic teeth which engage corresponding teeth on a cable tie body to provide locking engagement therebetween. As is typical of most cable ties, the tail of the cable tie is inserted into the head aperture uniquely in one direction. However, the art has also seen the use of bi-directional, or symmetrically-formed, cable ties which permit the cable tie tail to be inserted through the aperture in the head in either direction.
One such bi-directional cable tie is shown and described in co-pending commonly assigned U.S. application Ser. No. 08/689,466, filed Aug. 9, 1996, entitled "A Self-Locking Cable Tie Strap With Symmetrical Structure", issued on Mar. 23,1999, as U.S. Pat. No. 5,884,367 which is herein incorporated by reference for all purposes. The cable tie of such construction may be particularly used with an automatic cable tie installing device where a plurality of cable ties held together in a reel. A cable tie from the reel may be fed from a dispenser to a cable tie installing gun for installation about a plurality of wires. The symmetrical construction of the cable tie permits the cable tie to be easily dispensed and aligned within the installation gun. As may be appreciated, in order to accommodate insertion of the cable tie tail from either direction, the pawl or locking device of the symmetrical cable tie must be sufficiently flexible to permit deflection in either direction. Such flexibility assures that the cable tie tail may be easily inserted through the aperture in the head in either direction.
While such flexible construction permits easy insertion, it has been found that in certain circumstances such cable ties may not exhibit sufficiently high resistance to withdrawal forces as may be required in certain applications. Additionally, the art has uniformly provided bi-directional cable ties having symmetrical withdrawal-resistance characteristics while ignoring circumstances where it may be desirable to provide a bi-directional cable tie exhibiting discretely selectable, or non-symmetrical, withdrawal-resistance characteristics depending upon which direction the cable tie strap is inserted through the head.
Accordingly, it is desirable to provide a cable tie having a self-locking feature in a symmetrical structure which exhibits ease of insertion of the cable tie strap into the aperture in either direction and yet provides suitably high resistance to withdrawal forces in order to maintain a self-locking configuration. Additionally, it is desirable to provide a self-locking feature in an asymmetrical structure which offers discretely-selectable resistance to withdrawal forces according to the direction of strap insertion.