Abstract:
Provided is a tensioning clutch to be used in a tool for tensioning bundle, or cable, ties. A tensioning clutch according to the present invention includes a pawl mechanism having a removable pawl insert adapted to be reoriented or replaced without requiring significant disassembly of the housing of the tool. A tensioning clutch according to the present invention includes a pawl link, a tension abutment at least partly contemporaneously movable with the pawl link, and a pawl mechanism movably coupled to the pawl link. The pawl mechanism includes a pawl insert having one or more tie engagement surfaces, the insert being detachably coupled to a pawl body. The tie engagement surface of the insert may be biased towards, and movable away from, the tension abutment.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to tools used in tensioning bundle ties and more specifically to a bundle tie tensioning clutch to be used in a bundle tie tensioning tool. 
   Flexible bundle ties are well known items. Such ties are used to secure wires, cables, tubing and similar items into tight, neat bundles. Typically, flexible bundle ties include a head portion and a tie tail portion extending from the head. In use, the tie tail is looped around the items to be secured and then inserted through the head. A locking or ratcheting mechanism in the head holds the tie tail in the head and secures the tie around the bundle. Preferably, the tie tail is pulled through the head under tension to draw the items to be secured into a tight bundle. Thereafter, the excess portion of the tie tail may be clipped off near the head. 
   Many flexible ties are economically molded of flexible plastic. For some applications, however, plastic has insufficient strength or other drawbacks, and metal ties are used. Metal ties include a flat strap portion and a locking head portion, each of which is made of a strong, durable metal such as stainless steel. As a rule, metal ties are significantly stronger than plastic ties of the same size and are typically pulled at much higher tensions than plastic ties when they are installed. 
   A variety of tools have been developed to enable workers to install flexible bundle ties with speed, uniformity and economy. Generally, such tools function to grip the tie tail portion of the tie after the tie has been looped around the items to be bundled. The tool pulls the tie tail until a predetermined desired tension is achieved, after which the tool cuts off the excess portion of the tie tail closely adjacent the head. Such tools greatly simplify the task of properly installing bundle ties. 
   In a typical tie tensioning tool, a tie is grasped and pulled by a tensioning clutch including a pawl, a pawl link, a shaft, a torsion spring, and tension abutment such as a backing plate. The tensioning clutch is generally slidably situated in a housing. The pawl link usually includes a yoke in which the pawl is rotatably supported on the shaft. The torsion spring includes a substantially stationary leg that cooperates with an aperture in the pawl link, and a biasing leg that cooperates with the pawl, thereby biasing the pawl toward the backing plate. 
   Various handheld tools have been developed to assist in the installation of flexible ties. In one well known form of such tool, the tool comprises a pistol or gun-like device having a movable trigger or lever that is squeezed by the operator to pull on the tie tail and thereby tension the tie. The operator continues squeezing the trigger until a predetermined tension is achieved after which a cutting blade adjacent the nose of the tool snaps upwardly to clip off the excess portion of the tie tail. A knob at the rear of the tool allows the worker to adjust or set the tension at which cutoff occurs. Examples of such manually operated handheld tools are shown in the inventors&#39; U.S. Pat. No. 4,997,011, issued Mar. 5, 1991, U.S. Pat. No. 4,793,385 issued Dec. 27, 1998, and U.S. Pat. No. 5,921,290 issued Jul. 13, 1999, commonly owned by the assignee hereof. 
   The pawls of prior devices were normally cast in hardened steel and had teeth, which gripped a tie when the tie was inserted between the pawl and the cooperating tension abutment or backing plate. The pawl is a wear part of a tensioning tool. That is, eventually and frequently, the teeth on the pawl wear down and the clutch needs to be repaired or the pawl replaced. This is especially true when the tensioning tool is used with metal ties, such as stainless steel ties. Replacing or repairing a damaged or worn pawl is both time and labor intensive. Most prior devices require that the tool be taken out of service for repair, and replacement of the pawl requires disassembly of the tool&#39;s housing. As with any industrial teardown repair, care must be taken to ensure that reassembly is properly executed, and the tool must be tested prior to reinstatement of service. 
   Therefore, the art of tensioning bundle ties may benefit from a bundle tie tensioning clutch having an engagement surface that may be changed when desired, without significant disassembly of the remainder of the tensioning tool. 
   SUMMARY OF THE INVENTION 
   The present invention provides a bundle tie tensioning clutch having an engagement surface that may be changed when desired, without significant disassembly of the remainder of the tensioning tool. 
   In one embodiment, a tensioning clutch according to the present invention includes a pawl link, a tension abutment at least partly contemporaneously movable with said pawl link, and a pawl mechanism movably coupled to the pawl link. The pawl mechanism includes a pawl insert that is detachably coupled to a pawl body. The pawl insert includes a tie engagement surface, which is preferably biased towards and movable away from, the tension abutment, which may be a backing plate coupled to the pawl link. While the backing plate and pawl link could be provided separately, the backing plate may, instead, be formed integrally with the pawl link. The pawl mechanism is rotatably supported by the pawl link. The pawl link may form a yoke at least partially in which the pawl mechanism is movably supported. Such movable support may be provided in the form of rotatable support upon a bearing shaft. 
   The pawl insert is detachably coupled to said pawl body, which may be, for example, by a threaded mounting bolt inserted through said pawl insert and engaging a threaded mounting aperture located in the pawl body. In another embodiment, the pawl insert may be a polygonal insert having a plurality of tie engagement surfaces, such as three tie engagement surfaces. The pawl insert may be formed from, or at least include, a material including a carbide. The insert may include a tool surface, an access surface generally opposed from the tool surface by an insert thickness, at least one side surface extending from the access surface to the tool surface, and a mounting aperture accessible through the insert thickness. The insert tie engagement surface is preferably formed by the junction of the side surface and the access surface. The pawl body preferably includes an insert lip adapted to interface to at least one side surface of the pawl insert. The insert access surface may be a polygonal, planar surface, such as a triangular surface, for example. Similarly, the insert tool surface may be a polygonal, planar surface, such as a triangular surface. 
   The pawl mechanism of a tensioning clutch according to the invention may be biased towards the tension abutment by a torsion spring exerting a first force against said pawl link and a second force against the pawl mechanism. The second force may be exerted against the pawl body. 
   In another embodiment, an improvement is provided for a bundle tie tensioning tool having a mechanism for grasping a bundle tie. The improvement includes a pawl mechanism movably coupled to a pawl link. The pawl mechanism includes a pawl insert detachably coupled to a pawl body. Furthermore, the pawl link may be adapted for substantially linear reciprocal sliding movement within a housing of the tool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a prior art cable tie tensioning apparatus. 
       FIG. 2  is a right elevation partial cross section view taken along line  2 - 2  of  FIG. 1 . 
       FIG. 3  is a perspective view of an embodiment of a tensioning clutch according to the present invention. 
       FIG. 4  is a right elevation view of the embodiment of  FIG. 3 . 
       FIG. 5  is an assembly view of an embodiment of a pawl mechanism to be used in a tensioning clutch according to the present invention. 
       FIG. 6  is a right elevation partial cross section of a tool incorporating the tensioning clutch embodiment of  FIG. 3  in a first position. 
       FIG. 7  is a right elevation partial cross section of a tool incorporating the tensioning clutch embodiment of  FIG. 3  in a second position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
   Turning now to the Figures,  FIG. 1  and  FIG. 2  show a prior bundle tie tensioning tool  10 . The handheld tool  10  may be optimized for use with metal, and, in particular, stainless steel, ties. The handheld tool  10  includes a generally gun or pistol shaped housing  14  having a handle or grip portion  20 , a barrel portion  22  and a trigger  24 . The housing  14  is usually provided in a plurality of parts held together by threaded fasteners  15 . The trigger  24  is located forwardly of the grip  20  and under the barrel portion  22  where it falls naturally under the fingers of the operator. The trigger  24  is movable from an initial position spaced away from the grip  20  to a second position nearer the grip  20 . 
   A tie  12  is tensioned by means of a tensioning clutch  26 , which is slidably disposed at least partially within the barrel portion  22  of the housing  14 . The tensioning clutch  26  grips a tail portion  18  of the tie  12  and pulls it rearwardly as the trigger  24  is moved from the initial position to the second position. When the trigger  24  is released, it springs forwardly to the initial position. At the same time, the tensioning clutch  26  releases the tie tail  18  and moves forwardly relative to the tie tail  18 . As the trigger  24  is once again squeezed, the tensioning clutch  26  once again grips the tie tail  18  and draws it rearwardly. The process is repeated until a desirable tension is achieved in the tie  12 . 
   With reference more particularly to  FIG. 2 , the construction of the prior tensioning clutch  26  may be more fully explained. As illustrated, the tensioning clutch  26  is internally mounted at least partially in the barrel portion  22  and includes a pawl link  40  mounted for horizontal, linear reciprocating movement relative to the housing  14 . The pawl link  40  may be supported for linear sliding movement within the housing  14  by means of slider blocks  41  received within rectangular-sectioned channels  43  formed on the interior wall of the housing  14 . When a tie  12  is inserted into the tool  10 , the tie tail  18  is gripped by means of a tie gripping pawl  42  carried upon a shaft  45  disposed towards the forward end of the pawl link  40 . The gripping pawl  42  is pivotally attached to the pawl link  40  and is upwardly biased toward a tension abutment such as a backing plate  44 , which is also carried by the pawl link  40 . In the prior device  10 , the backing plate  44  is integrally formed with the pawl link  40 . The gripping pawl  42  is rotatably biased toward the backing plate  44  by means of a torsion spring  46  so that a bundle tie tail  18  inserted therebetween will be engaged by and between the pawl  42  and the backing plate  44 . The upper surface of the pawl  42  is provided with teeth or serrations  42   a  that engage the tie tail  18 . 
   A nose guide block  38  may be provided within the housing  14 . The guide block  38  includes a surface that engages the gripping pawl  42  when the pawl link  40  is at the leftmost or initial position. Such engagement pivots the gripping pawl  42  away from the backing plate  44  to facilitate insertion of the tie tail  18  into the tool  10 . When the pawl link  40  moves toward the right, the tie tail  18  is pinched between the gripping pawl  42  and the backing plate  44 . The tie tail  18  is thus pulled along with the pawl link  40 . It will be appreciated that, as the pawl links  40  move to the right, the gripping pawl  42  grips the tie tail  18  to pull the tie tail  18  and thereby tension the tie  12 . When the pawl link  40  is reciprocated to the left, the gripping pawl  42  loosens its grip on the tie tail  18 , thereby permitting the pawl link  40  to return to its initial position without simultaneously moving the tie tail  18 . 
   Turning now to  FIG. 3  and  FIG. 4 , an embodiment  100  of a bundle tie tensioning clutch according to the present invention is shown. Like prior devices, the tensioning clutch  100  includes a pawl link  140 , a pawl mechanism  142 , a tension abutment such as a backing plate  144 , a shaft  145 , and a torsion spring  146 . The clutch  100  also preferably includes a tool interface  141  that may include mounting structure such as a threaded stud to be linked to the drive mechanism of the tool and bearing supports to provide a mounting location for slide blocks, similar to those  41  in  FIG. 2 . A tensioning clutch according to the present invention may be used with a variety of tensioning tools that may be actuated by, for example, mechanical means, pneumatic means, electromechanical means, electrical means, manual means, or any combination thereof. Further, the clutch  100  may include a transition plate  148  mounted to the pawl link  140  by a pair of threaded fasteners  149 . As explained further below, the pawl mechanism  142  of a tensioning clutch  100  according to the present invention includes a replaceable pawl insert  152 . The pawl insert  152  is mounted to the pawl body  150  in a manner that allows removal and replacement of the insert  152  without the need for disassembly of the entire tensioning tool. 
     FIG. 5  provides an assembly view of an embodiment of a pawl mechanism  142  according to the present invention. The pawl mechanism  142  includes a pawl body  150  and a replaceable pawl insert  152 , which is coupled to the pawl body  150  preferably by a threaded mounting bolt  154 . If a threaded mounting bolt  154  is used, the mounting bolt  154  may be removed by using a tool, such as a manual screwdriver  200 , for example. Such removal may occur preferably while the clutch  100  is operatively mounted in a tensioning tool. The pawl body  150  preferably includes structure to maintain the pawl insert  152  in a desired orientation. In this example, the pawl body  150  has an insert lip  151 , against which a side of the pawl insert  152  rests when coupled to the body  150 , and a threaded mounting aperture  153 , adapted to accept the threaded mounting bolt  154 . The pawl body  150  is preferably formed from any desirable supportive material, such as steel, aluminum, etc. The pawl insert  152  is preferably a commercially available triangular carbide insert such as a G10E insert available from Sumitomo Electric Carbide, Inc. of Mount Prospect, Ill. The insert  152  has preferably a plurality of tie engagement surfaces  155 . While a triangular insert  152  is preferred, any polygonal insert  152 , such as a rectangle, a pentagon, a hexagon, etc., may also be used. Use of a polygonal insert  152  having multiple engagement surfaces  155  provides a user the ability to quickly adjust the insert  152 , thereby providing a sharp edge when one is desired. Inserts  152  having different shapes than those listed may also be employed. 
     FIG. 6  shows the embodiment  100  of  FIG. 3  that has been incorporated into the barrel portion  122  of a bundle tie tensioning tool  110  similar to the prior tool  10  of  FIG. 1 . In this position, the pawl mechanism  142  is rotated rearwardly by the nose guide block  138 , thus parting the pawl insert  152  from the backing plate  144  to ease lateral tie insertion. 
     FIG. 7  also shows the embodiment  100  of  FIG. 3  that has been incorporated into the barrel portion  122  of a bundle tie tensioning tool  110  similar to the prior tool  10  of  FIG. 1 ; however, the tensioning function of the tool has been activated, e.g. by way of a user grasping a trigger on the tool  110 , so that the clutch  100  has been retracted away from the nose guide block  138  thereby allowing the torsion spring  146  to bias a tie engagement surface  155  of the pawl mechanism  142  against the tie  12 . The tie  12  is thus gripped between the pawl insert  152  and the backing plate  144  during a majority of the retraction of the clutch  100 . 
   The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.