Abstract:
An improved tool head for use with an automatic cable tie installation system providing improved reliability, and reduced jamming and/or failure. The improved tool head incorporates a structurally rigid frame which locates and supports the interacting and cooperating components of the tool head in a precise relationship despite such factors as flexing and twisting of the housing, thermal expansion and contraction of the housing, and operational wear.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a tool head and, more particularly, to a tool head for use with an automatic cable tie installation system providing improved performance and reliability. 
     As is well-known to those skilled in the art, cable ties are used to bundle or secure a group of articles such as electrical wires or cables. Cable ties of conventional construction include a cable tie head and an elongate tail extending therefrom. The tail is wrapped around a bundle of articles and thereafter inserted through a passage in the head. The head of the cable tie typically supports a locking element which extends into the head passage and engages the body of the tail to secure the tail to the head. 
     Although cable ties are often installed manually, it is desirable in certain applications to utilize an automatic cable tie installation system wherein cable ties are dispensed from a remote dispenser, and thereafter delivered to a tool head for application about a bundle of wires positioned within the jaws of the tool head. Automatic cable ties installation systems are well-known in the art, and are disclosed for example in U.S. Pat. Nos. 4,790,225 and 4,498,506. It will be appreciated that the disclosed tool heads include a plurality of subassemblies each having multiple moving parts, the subassemblies cooperating together to deliver, tension and cut the cable tie. To be commercially practical, the tool head must be capable of repeatedly applying a cable tie about the bundle of articles inserted within the jaw assembly without jamming. The tool head must also be able to complete a cycle (wherein one cable tie is wrapped, tensioned and cut) within a sufficiently short interval of time. 
     Those skilled in the art will appreciate that the foregoing requirements demand extremely accurate and precise location and support of the various cooperating components of the tool head. These prior art tool heads, including the tool heads disclosed in the mentioned patents, often locate and support many of the internal cooperating components via the housing shells. These housing shells are typically formed of plastic and are susceptible to flexing and twisting during operation which can adversely affect the cooperation between the components of the tool head, thus leading to jamming and/or failure of the tool head. Moreover, the practice of locating the various cooperating components of the tool head with respect to more than one reference structure (e.g., the two separate housing shells) allows the manufacturing tolerances associated with the individual components to be combined, which may lead to misalignment of the components. 
     There is therefore a need in the art for a tool head for use with an automatic cable tie installation system which exhibits improved reliability, and reduced jamming and/or failure. The improved tool head should maintain an accurate and precise relationship between the interacting and cooperating components of the tool head even when the tool head is subjected to such factors as flexing and twisting of the housing, thermal expansion and contraction of the housing, and operational wear. 
     SUMMARY OF THE INVENTION 
     The present invention, which addresses the needs of the prior art, relates to a tool head for installation of a cable tie about a bundle of elongate articles. The tool head is adapted for use with a remote dispenser, cable tie bandolier and cable tie delivery hose of an automatic cable installation system. The cable tie includes a head and an elongate tail extending therefrom. The tool head includes a housing including first and second cooperating shells. The tool head further includes a jaw assembly for grasping and directing the cable tie about the articles. The tool head further includes a tie passage communicating at one end with the cable tie delivery hose and at the other end with the jaw assembly whereby a cable tie supplied by the remote dispenser is delivered to the jaw assembly. The tool head further includes a tie tensioning assembly for tensioning the cable tie upon installation of the cable tie about the elongate articles. The tie tensioning assembly includes a drive train and a pawl gear cut-off mechanism. Finally, the tool head includes a structurally rigid frame sized for location within the housing. The frame provides a fixed and common reference structure independent of the housing to both support the pawl gear cut-off mechanism and to locate the pawl gear cut-off mechanism with respect to the drive train. 
     As a result, the present invention provides a tool head for use with an automatic cable tie installation system which exhibits improved reliability, and reduced jamming and/or failure. The structurally rigid frame utilized in the improved tool head maintains an accurate and precise relationship between the interacting and cooperating components of the tool head even when the tool head is subjected to such factors as flexing and twisting of the housing, thermal expansion and contraction of the housing, and operational wear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an automatic cable tie installation system; 
     FIG. 2 is an exploded perspective view of a prior art tool head; 
     FIG. 2 a  is an enlarged detail of FIG. 2; 
     FIG. 3 is an exploded perspective view of a tool head in accordance with the present invention; 
     FIG. 4 is a side elevational view of the tool head of FIG. 3; 
     FIG. 5 is a perspective view of the components of the tool head of FIG. 3 removed from their housing; and 
     FIG. 6 is an exploded perspective view of the structurally rigid frame and gear assembly of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, an automatic cable tie installation system  10  is shown in FIG.  1 . Installation system  10  includes a cable tie dispenser  12  (as described in commonly-owned pending U.S. application Ser. No. 09/377,650, incorporated herein by reference), a cable tie bandolier  14  (as described in commonly-owned U.S. Pat. Nos. 5,934,465 and 5,967,316, incorporated herein by reference), a cable tie delivery hose  16  and a tool head  18 . In operation, dispenser  12  severs the leading cable tie from bandolier  14 , and thereafter propels the individual cable tie to the tool head via hose  16 . The cable tie is wrapped about a bundle of articles positioned within the jaws, tensioned and is then subjected to a cutting operation whereby the excess portion of the cable tie tail is cut from the tensioned cable tie. 
     The operating components of a prior art tool head  50  are shown in FIGS. 2 and 2A. In this regard, the general operation of tool head  50  is well-known to those skilled in the art. As discussed hereinabove, U.S. Pat. Nos. 4,498,506 and 4,790,225, both of which are incorporated herein by reference, disclose the structure and operation of a prior art tool head. 
     As will be appreciated by those skilled in the art, the housing of tool head  50 , i.e., housing  52 , is preferably formed from first and second cooperating shells  54   a ,  54   b , such shells being used to both support and locate the various components of the tool head. Although it is commercially desirable to form shells  54   a ,  54   b  from a plastic material, this construction introduces the possibility that housing  52  may flex and twist during operation which can lead to misalignment of the cooperating components, and ultimately jamming and/or failure of the tool head. 
     Tool head  50  includes jaw assembly  56 , tie tensioning assembly  58 , and a tie passage  60  communicating at one end with cable tie delivery hose  16  and at the other end with jaw assembly  56  whereby a cable tie supplied by remote dispenser  12  is delivered to the jaw assembly. 
     Jaw assembly  56  includes in particular a top jaw  62 , a bottom jaw  64 , opposing jaw-mounting plates  66   a ,  66   b , a trigger  68  connected to bottom jaw  64  for moving the bottom jaw between an open position and a closed position, a push rod  70  for moving top jaw  62  during installation of the cable tie about the bundle of elongate articles, a power-operated device  72  for powering said push rod, and a cutting mechanism  73  supported between jaw-mounting plates  66   a ,  66   b.    
     Tie tensioning assembly  58  includes in particular a drive train  74 , a pawl gear cut-off mechanism  76  and a tension adjustment mechanism  78  pivotable about a pivot point  80 . Cutting mechanism  73  cooperates with pawl gear cut-off mechanism  76  to cut off any excess portion of the tail from the tensioned cable tie. 
     In turn, drive train  74  includes a power-operated device  82 , a driveshaft  84  coupled at one end to power operated device  82 , a driveshaft bearing for supporting the other end of driveshaft  84  positioned within a housing  86 , and a gear assembly  88 . In turn, gear assembly  88  includes a first bevel gear  90  positioned at the end of the driveshaft  84 , a second bevel gear  92  fixedly coupled to a shaft  94  and located to engage first bevel gear  90 , a drive gear  96  also fixedly coupled to shaft  94 , a pair of opposing bearings  98  for rotatably supporting shaft  90 , and an idler gear  100  rotatably coupled to a shaft  102  via a bearing  104  and located to cooperate with the pawl gear cut-off mechanism  76 . As a result, rotary motion may be transmitted from driveshaft  84  to the internal gear  105  (shown in hidden line in FIG. 2A) of pawl gear cut-off mechanism  76 . 
     Gear assembly  88  further includes a pair of opposing gear-supporting plates  106   a ,  106   b , for supporting the mentioned gears therebetween. In this regard, each of plates  106   a ,  106   b  includes an aperture  108  sized to receive bearings  98 , and an aperture  110  sized to receive the end of shaft  102 . A microswitch  112  for sensing the presence of a cable tie is mounted on a bracket  114 , which in turn is secured to gear-supporting plate  106   a . Gear-supporting plates  106   a ,  106   b  also pivotally support pawl gear cut-off mechanism  76  via a pair of pivot pins  116 . Each of gear-supporting plates  106   a ,  106   b  include a pair of apertures  118  sized to receive the ends of pivot pins  116 . Gear-supporting plates  106   a ,  106   b , themselves are each separately supported by shells  54   a ,  54   b , respectively, of housing  52 . Thus, flexing of housing  52  can result in independent movement of each of driveshaft bearing  86 , gear-supporting plate  106   a  and gear-supporting plate  106   b.    
     It will be appreciated that pawl gear cut-off mechanism  76  must be properly aligned with jaw assembly  56  to receive the tail of the cable tie. Pawl gear cut-off mechanism  76  must also be properly aligned with microswitch  112  to ensure smooth operation of the tool head. Again, twisting and/or flexing of housing  52  may produce misalignment and/or movement of gear-supporting plates  106   a ,  106   b  (either together or independent of one another), thus causing misalignment of pawl gear out-off mechanism  76  with respect to jaw assembly  56 . Of course, this same twisting and/or flexing of housing  52  can produce movement and misalignment of the jaw assembly itself. Finally, to ensure proper tensioning of the cable tie during operation, the location of tension adjustment mechanism  78  with respect to the pawl gear cut-off mechanism must be maintained. 
     Referring now to FIGS. 3-6, tool head  18  of the present invention incorporates and utilizes a novel, structurally rigid mounting frame  120 , also referred to as the “unibody.” Frame  120  preferably includes first and second locating plates  122   a ,  122   b . These plates are preferably machined metal plates which are configured to be securely fixed to one another via screws and/or bolts. When assembled, the unibody forms a structurally rigid frame which provides a fixed and common reference structure independent of the housing to both support pawl gear cut-off mechanism  76  and to locate pawl gear cut-off mechanism  76  with respect to drive train  74 . Preferably, the unibody also supports and locates the drive shaft bearing, supports and aligns the gear assembly, locates the jaw assembly, locates the pivot point for the tension adjustment mechanism and locates the microswitch. 
     Each of locating plates  122   a ,  122   b  includes a jaw-locating bracket  124   a ,  124   b  configured for securement to the jaw-mounting plates of the jaw assembly, thus locating the jaw assembly with respect to the unibody, and in turn with respect to the pawl gear cut-off mechanism. In this regard, each of brackets  124   a ,  124   b  includes a pair of screw-receiving apertures  126  which are located to align with a pair of threaded apertures (not shown) provided in each of jaw-mounting plates  66   a ,  66   b.    
     Locating plate  122   a  also includes an arm  128  having a aperture  130 , which provides the pivot point for the tension adjustment mechanism and which receives a pivot pin  132  (see FIG.  4 ). Accordingly, the location of pivot pin  132  is fixed with respect to pivot pins  116  (i.e., the pins that support pawl gear cut-off mechanism  76 ), thus ensuring proper cooperation between the tension adjustment mechanism and the pawl gear cut-off mechanism during all conditions of operation. Each of locating plates  122   a ,  122   b  further includes a threaded aperture  134  which receives a screw passing through housing shells  54   a ,  54   b , respectively, thereby allowing shells  54   a ,  54   b  to be secured to locating plates  122   a ,  122   b , respectively. 
     Referring now to FIG. 6, locating plates  122   a ,  122   b  together provide a driveshaft bearing housing  136 , which supports the driveshaft bearing. Locating plate  122   a  includes a pair of threaded apertures  138 , while locating plate  122   b  includes a pair of screw-receiving apertures  140 . Installation of screws  142  thus fixedly secures the locating plates to one another, and also secures the drive shaft bearing within bearing housing  136 . 
     Thus, when the unibody is assembled within the tool head, the unibody forms a structurally rigid frame which provides a common reference for locating the various operating components of the tool head. In contrast to the use of a plastic housing for locating the tool components, the unibody is preferably formed from machined plates, thus ensuring the accuracy at which the various attachment points are located. It will be appreciated that the unibody&#39;s rigid structure ensures that all parts are held in proper orientation relative to each other, and prevents binding and misalignment of the moving components due to such factors as torque from the motors thermal expansion and contraction of the housing and operational wear. Thus, one common structure which is unaffected by flexing and/or twisting of the tool housing locates and supports the drive train, and also aligns the various subassemblies of the tool head with one another. 
     Although the unibody is described as including locating plate  122   a ,  122   b , it is contemplated herein that the unibody can be formed as a single integral unit. This may of course require certain modifications to the gear assembly, to the coupling of the pawl gear cut-off mechanism to the unibody, and to the drive shaft bearing housing. However, the unibody (whether formed as a single unit or plural pieces) provides a structurally rigid frame which locates and supports the various components of the tool head to prevent binding and misalignment of such components during operation. 
     It will be appreciated that the present invention has been described herein with reference to certain preferred or exemplary embodiments. The preferred or exemplary embodiments described herein may be modified, changed, added to or deviated from without departing from the intent, spirit and scope of the present invention, and it is intended that all such additions, modifications, amendment and/or deviations be included within the scope of the followings claims.