Abstract:
An automatic knot-tying device for tying a discrete knot about a workpiece, such as a bundle of wires, is disclosed herein. The present invention works by pulling a filament transversely around the workpiece. The preferred embodiment of the device comprises a hand-held housing and a knot-tying mechanism within that housing comprising a hollow nozzle for leading the filament toward the workpiece, a wrapping ring for wrapping the filament around the workpiece, and a plurality of pins that extend into and retract out of the path of the filament to form the knot. The operation is finished by cinching and cutting the loose filament so that the resulting knot is discrete and secure. Also disclosed is a method for automatically tying a knot around a workpiece by pulling, instead of pushing a filament around the workpiece.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to automatic knot-tying devices and more particularly to an automatic knot-tying device for tying a knot around a generally cylindrical target item. 
     BACKGROUND OF THE FIELD 
     In many industries, both military and commercial, such as the aircraft, automotive, and appliance industries, wire bundles, or harnesses, are used extensively in the manufacturing processes of various products. Each bundle, or harness, generally comprises two or more wires that customarily are tied together at various points along their lengths to help ensure safety and durability, as well as a generally clean design. 
     Individually tying the bundle points by hand is costly, labor-intensive, and time-consuming, and often leads to carpal tunnel syndrome, or other physical injury, in the operator. With these problems in mind, several patented inventions have been directed toward automating the wire-tying process. One such device, that described in German Offenlegungsschrift U.S. Pat. No. 2,533,640 and improved in U.S. Pat. No. 4,558,894 to Detterbeck et al, is a hand-held pistol-like apparatus that forms a continuous crocheted tying structure around and along a bundle of wires. Even Detterbeck&#39;s improvement, however, does not actually tie a knot around the bundle: it simply pulls taut a predetermined number of loops. The device, therefore, is limited because it is not capable of tying individual knots at discrete points along the bundle. 
     Another patented device is described in U.S. Pat. No. 4,094,342 to Nishikawa et al. Nishikawa&#39;s device uses guide channels along the inside surface of the bundle holding elements to guide the string or cord around the wire bundle into the shape of a knot. The string is then pulled taut and cut. Several problems, including jamming and inconsistent knot quality, are associated with the Nishikawa device because it pushes, rather than pulls, the string around the bundle. 
     One feature of knot-tying is that a second pass of the string around the bundle must be laid in front of or behind a first pass. The prior art has not dealt with this problem very successfully; instead, prior art devices have tried simply to lay the string in patterns described by guide channels in the holding elements themselves. The Nishikawa device, and other devices, particularly the one described in U.S. Pat. No. 3,057,648 to Schwarze et al, use guide channels of differing depths to result in criss-crossing passes of the string. In a different approach, the device disclosed in prior art patent to Jung et al., U.S. Pat. No. 4,502,905, uses a transverse pin with a hook to grab the second pass of the string and draw it back across the first pass. 
     The Jung device illustrates another problem in the prior art—that of finishing the knot. After the string is laid around the bundle, the Jung device heats and bonds the string instead of tying a knot. Such heating, or other type of fusing or bonding, as well as the use of plastic, generic cotton string, or other fabric are frequently not acceptable because of the harsh environments encountered by many installations of wire bundles. Depending upon the particular industry and the application of the product, these bundles may be placed in environments of extreme temperature, vibration, radiation, or other types of shock. To withstand these conditions while maintaining the integrity of the knot, many applications require the use of “lace,” a particular type of flexible string-like material. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention comprises a hand-held housing with an activating button or switch so that the user can easily manipulate the device and apply a knot at any desired discrete location, or a series of discrete locations, along a bundle. The housing defines a generally U-shaped opening into which the bundle fits with the bundle longitudinal axis generally transverse to the handle. The user does not have to manipulate the bundle or come into physical contact with it at all; he simply thrusts the device around the bundle and presses the activating button. 
     The housing contains a knot-tying mechanism that actually ties a knot, i.e., not loops or chains of loops, around the wire bundle. With the present invention, any of several different knots could be tied, with different arrangements and indexing of pins and hooks; however, in the preferred embodiment, it has been chosen to tie a clove hitch around the bundle and then tie a surgeon&#39;s knot to secure the clove hitch, because this combination of clove hitch and surgeon&#39;s knot is the FAA-approved method of tying wire harnesses. Military specifications also require use of the clove hitch/surgeon&#39;s knot combination. 
     The knot-tying mechanism of the device operates in two distinct stages. In the first stage, the mechanism wraps and tightens the clove hitch around the bundle, and then in the second stage, the mechanism ties the surgeon&#39;s knot to secure the wrapped clove hitch. The mechanism then resets itself for the next operation. A continuous supply of lace, or other filament, is fed to the device by a belt-mounted or housing-mounted spool, or some other method. The entire process from the moment the device engages the bundle to the moment the device disengages the bundle, leaving a precisely tied, tight, and finished discrete knot, takes approximately 5 seconds, using the preferred embodiment. Of course, alternate embodiments, particularly with alternate controlling means, can easily speed up or slow down the processing time. 
     The knot-tying mechanism of the preferred embodiment comprises a nozzle, from which the lace issues, a wrapping ring, which rotates around the bundle, completely circumscribing it, and various reciprocating, twisting, and sliding pins and hooks that extend and retract into and out of the path of the lace proximate the bundle. 
     The nozzle of the preferred embodiment of the present invention not only delivers the lace to the knot-tying mechanism, but also acts as a key element of the knot-tying processes. Because the nozzle itself is angled and tapered as it approaches the bundle, it can control the laying of a second pass of lace across a first pass around the bundle, thus eliminating the need for transverse pins with hooks to pull or push the lace of the second pass. Because the nozzle twists upon its own longitudinal axis, it is able to play a large role in the knot-tying process, thereby greatly reducing the overall number of pins and hooks necessary. 
     The wrapping ring of the preferred embodiment of the present invention is linked to the housing so that it can swing about the bundle, completely circumscribing it, as many times as is necessary for the desired knot design. A clamp on the wrapping ring temporarily holds the free end of the lace issuing from the nozzle, and is preset to release the lace at the proper time during the knot-tying process. The combination of the wrapping ring and the clamp, instead of holding elements and guide channels, pulls the lace around the bundle instead of pushing it, thus eliminating the problems associated with pushing, such as jamming and inconsistent knot quality. 
     In the preferred embodiment, the pins and hooks that reciprocate so as to extend into and retract out of the proximity of the knot are also capable of twisting on their own axes. Such twisting action, in combination with holding grooves on only one side of the pin, allows that the lace may be held as necessary and then immediately released so as to provide slack in the knot-tying process at the appropriate time. Because the pins and hooks are so multi-functioned, the number of elements needed to tie the knot is minimized. 
     When the user first engages the preferred embodiment of the device with the bundle, by placing the bundle generally transversely within the opening of the housing, the knot-tying mechanism is in the initial set-up position. In this initial set-up position, the free end of the lace issuing from the nozzle is held in place on the wrapping ring by the clamp. Once actuated, by the button or other actuation method, the mechanism begins the clove hitch process. With the lace being continuously fed from the nozzle, the wrapping ring rotates around the bundle, carrying the lace with it, and various pins and hooks, which in the preferred embodiment are specifically referred to as the loop slack pin, the main hook, the first clove hitch retaining pin, and the main slack pin come into play at various times to snag, tighten, or guide the lace. 
     Once the clove hitch is complete and tight, the knot-tying mechanism then ties and finishes a surgeon&#39;s knot to secure the wrapped clove hitch and finish the procedure. In this surgeon&#39;s-knot tying process, the various reciprocating, twisting, and sliding pins involved are specifically referred to in the preferred embodiment as the second clove hitch retaining pin, the nozzle tab, the main slack pin, the tail cincher, and the surgeon&#39;s knot retaining pin. Also during this process, the nozzle assembly rotates around the bundle, changing its orientation thereto, the nozzle tube extends and retracts within its own housing, and the nozzle tube twists about its own axis. 
     In the preferred embodiment, once the surgeon&#39;s knot is complete, a cutting edge engages and severs the lace so that the knot is stand-alone and discrete. The lace is then reattached to the clamp on the wrapping ring, and the mechanism is ready for the next engagement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a perspective view of the preferred embodiment of the invention of the automatic knot-tying device as it is held by a user; 
     FIG. 1 b  is a side view of the preferred embodiment of the invention of the automatic knot-tying device; 
     FIG. 1 c  is a front view of the device showing the center line along which the remaining detail views are generally taken; 
     FIG. 2 is a detail section view showing the initial set-up configuration of the knot-tying mechanism; 
     FIG. 3 is a detail section view showing an intermediate step in the clove hitch process; 
     FIG. 4 a  is a detail section view showing an intermediate step in the clove hitch process; 
     FIG. 4 b  is a front view showing the intermediate step of FIG. 4 a;    
     FIG. 5 is a front view of an intermediate step in the clove hitch process; 
     FIG. 6 a  is a detail section view of an intermediate step in the clove hitch process; 
     FIG. 6 b  is a front view of the intermediate step of FIG. 6 a;    
     FIG. 7 a  is a detail section view of an intermediate step in the clove hitch process; 
     FIG. 7 b  is a front view of the intermediate step of FIG. 7 a;    
     FIG. 8 is a detail section view of an intermediate step in the clove hitch process; 
     FIG. 9 a  is a detail section view of an intermediate step in the clove hitch process; 
     FIG. 9 b  is a front view of the intermediate step of FIG. 9 a;    
     FIG. 10 is a detail section view of an intermediate step in the clove hitch process; and 
     FIG. 11 is a front detail section view of the final step in the clove hitch process. 
     FIG. 12 a  is a detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 12 b  is a front view of the intermediate step of FIG. 12 a;    
     FIG. 13 is a detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 13 b  is a front view of the intermediate step of FIG. 13 a;    
     FIG. 14 is a front detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 15 a  is a detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 15 b  is a front view of the intermediate step of FIG. 15 a;    
     FIG. 16 is a detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 17 a  is a detail section view of an intermediate step in the surgeon&#39;s knot process; 
     FIG. 17 b  is a front view of the intermediate step of FIG. 17 a;    
     FIG. 18 is a detail section view of an intermediate step in the surgeon&#39;s knot process; and 
     FIG. 19 is a detail section view of the final step in the surgeon&#39;s knot process. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 a  is a perspective view of the preferred embodiment of the invention of the automatic knot-tying device  10  as it is intended to be held by a user. The lace supply  18  in the preferred embodiment is a belt-mounted spool. In alternate embodiments, the lace supply could be a spool or reel mounted to the handle  14  or other location. FIG. 1 b  is a side view of the preferred embodiment of the invention of the automatic knot-tying device  10 . The device  10  comprises a housing  12  attached to a handle  14  with power connection  16 . The preferred embodiment also comprises a button  20  for actuating the device. However, in alternate embodiments, there could be a trigger, proximity sensor, or other device mounted on the housing for purposes of actuation. 
     In the preferred embodiment, the housing  12  defines a generally U-shaped opening  22  for accommodating the workpiece, usually a bundle of wires  24 . The opening  22  fits around the bundle  24  such that the handle  14  of the device  10  is generally orthogonal to the longitudinal axis of the bundle  24 , as seen in FIG. 1 c . FIG. 1 c  is a front view of the device  10  showing the section lines along which the remainder of the detail views will generally be taken. 
     The knot-tying mechanism  28  is shown in FIG. 2 in the initial set-up configuration. FIG. 2 is a detail view of the mechanism  28  taken along the section lines shown in  1   c . The mechanism  28  comprises a nozzle assembly  30 , which is mounted onto two nozzle tracks  40 , which, in the preferred embodiment, are designed in a circular arc and defined by the housing  12 . The tracks  40  in the preferred embodiment are coplanar with the plane defined by the wrapping ring  44 , hereinafter referred to as the reference plane. The lace  42 , or other filament, is delivered from the supply  18  through the nozzle tube  36  and out the nozzle tip  38 . The free end of the lace  42  is then clamped onto the wrapping ring  44  by use of the clamp  46 . The bundle  24  fits into the opening  22  such that it is entirely within the circle defined by the wrapping ring  44 . 
     In the initial set-up configuration, the nozzle assembly  30  rests at the downward end of the nozzle tracks  40  with the nozzle tube  36  extending generally vertically from the nozzle housing  32  into the proximity of the wire bundle  24 . (The nozzle set screw  34  is tightened so as to allow the nozzle tube  36  to reciprocate through the housing  32 .) The nozzle tube  36  is not coplanar with the wrapping ring  44 , but instead approaches the reference plane at an angle of approximately 25 degrees. The lace  42  is relatively taut but not restrained within the nozzle tube  36  so that it is allowed to issue freely from the nozzle tip  38 . The wrapping ring  44  initially rests such that the clamping screw is positioned at approximately 250 degrees. 
     Upon activation by the button or other signaling device, the wrapping ring  44  begins to rotate clockwise in the first step of the knot-tying procedure, i.e., tying the clove hitch. FIG. 3 shows an intermediate position after the wrapping ring  44  has rotated approximately 300 degrees clockwise, placing the loop slack pin  48 , which is oriented generally orthogonal to the reference plane, within the path of the lace  42 . The lace  42  has wrapped partially around the bundle  24 , and the clamp  46  is now at approximately 200 degrees. 
     FIG. 4 a  shows a later intermediate position after the wrapping ring  44  has continued an additional 145 (approx.) degrees clockwise rotation around the bundle  24 . The groove  50  in the loop slack pin  48  (shown in FIG. 4 b ) is initially oriented generally away from the opening  22  such that the groove  50  has caught and loosely retained the lace  42 , which has now come into contact once again with the bundle  24 , completing a closed loop formation around the bundle  24 . The clamp is now positioned at approximately 15 degrees. 
     The front view of FIG. 4 b  shows that because of the proximity of the nozzle tip  38  to the extension pin housing wall  52 , the angle of the nozzle tube  36  (not shown in this figure), and the taper of the nozzle tip  38 , the second pass of the lace  42  over the top of the bundle  24  will be in front of (more forward from the extension pin housing wall  52 ) the first pass of the lace  42 . 
     In FIG. 5, which shows a next step before the wrapping ring  44  rotates further, the hook  54 , which is oriented generally orthogonal to the reference plane, extends from the extension pin housing wall  52  to its maximum position forward. The loop slack pin  48  retracts back toward the extension pin housing wall  52  in order to avoid snagging the second pass of the lace  42  but not so far as to pin the lace  42  against the wall  52 . 
     After an additional rotation, of approximately 270 degrees, of the wrapping ring  44 , as shown in FIG. 6 a , the hook  54  has caught the lace  42  on the second pass around the bundle  24 , causing a “V-shaped” formation in the lace  42 . The first leg of the “V” extends from a point on the periphery of the bundle  24  toward the loop slack pin  48 , and the second leg extends toward the hook  54 . The clamp  46  is now at approximately 260 degrees. The hook  54 , in FIG. 6 b , now recedes back into the extension pin housing wall  52 , trapping the lace  42  and pinning it against the wall  52 . The clamp  46  then releases the lace  42 , leaving the free end of the lace  42  projecting from the far side of the hook  54 . 
     FIGS. 7 a  and  7   b  illustrate the continuation of the clove hitch process, with the first clove hitch retaining pin  56 , which is oriented generally orthogonal to the reference plane, extending from the extension pin housing wall  52  at the apex of the “V” formation. The groove  58  (not shown) in the first clove hitch retaining pin  56  is initially oriented generally toward the bundle  24  so as to be facing the second leg of the “V.” 
     At this point, the lace  42  being fed from the nozzle tip  38  must be clamped tightly within the nozzle for the duration of the clove-hitch process. FIG. 8 shows how the first clove hitch retaining pin  56  begins to rotate clockwise (within the track defined by the hitch pin housing wall  60 ) around the bundle  24 , encountering the second leg of the “V” as it does so. The groove  58  (not shown) in the first clove hitch retaining pin  56  snags the lace  42  and carries the lace  42  along the path of the pin  56 . As it travels along this path, the first clove hitch retaining pin  56  recedes back into the hitch pin housing wall  60  so as to clear any other part of the lace  42  as it rotates around the bundle  24 . The first clove hitch retaining pin  56  comes to rest at approximately 285 degrees, forming an “eyelet”  62  in the lace  42 . 
     In FIG. 9 a , the main slack pin housing  70 , which lies along a plane generally parallel with the reference plane but simply off-set slightly, has pivoted clockwise on the bolt  72  so that the main slack pin  74  is brought into play. The main slack pin  74  extends from the housing  70  so that the main slack pin tip  76  is positioned within the eyelet formation  62  of the lace  42  beside the first clove hitch retaining pin  56 . FIG. 9 b  shows how the hook  78 , which is oriented generally orthogonal to the reference plane, has extended from the tip  76  into the eyelet  62 . 
     FIG. 10 shows how the main slack pin  74  then extends further from the housing  70  so that the tip hook  78  will snag and carry the lace  42  such that only a small amount of free end of the lace  42  is remaining pinned by the main hook  54  to the extension pin housing wall  52 . 
     To complete the clove-hitch process, the loop slack pin  48  then twists approximately 180 degrees to release the lace  42  from the groove  50  and then recedes back into the wall  52  so that the loop slack pin  48  is now out of play. FIG. 11 shows the loop slack pin  48  after having receded. The lace  42  now hangs loosely around the bundle  24  and the clove hitch is complete. 
     FIG. 12 a  shows the next intermediate step. In order to maintain the integrity of the clove hitch during the next phase of the knot-tying process, the second clove hitch retaining pin  80 , which is oriented generally orthogonal to the reference plane, extends from the hitch pin housing wall  60 , capturing within the groove  82  the portion of the lace  42  being fed from the nozzle  38 . Now begins the process of tying the surgeon&#39;s knot to secure the clove hitch around the bundle  24 . FIG. 12 b  is a front view of this intermediate step. 
     In FIG. 13 a , first the nozzle tube  36  retracts within the nozzle housing  32 . Then the nozzle assembly  30  begins its journey along the nozzle tracks  40  and continues until the nozzle tip  38  is positioned beneath the taut strand of lace  42  between the main slack pin  74  and the main hook  54 . The nozzle tube  36  twists, if necessary, so that the gap between the nozzle tab  84  (shown in FIG. 13 b ) and the nozzle tip  38  is then aimed at the taut strand of lace  42  in preparation to capture the lace  42  in the gap. The nozzle tube  36  then extends from the nozzle housing  32  so far as to pin the lace  42  in the gap between the nozzle tab  84  and the nozzle tip  38  against the extension pin housing wall  52 . In FIG. 14, the lace  42  (not shown in this figure) is being held against the wall  52 . The main hook  54  extends, releasing its own hold on the lace  42 . 
     In FIG. 15 a , while the nozzle assembly  30  continues to journey clockwise along the nozzle tracks  40 , the nozzle tube  36  begins to twist about its own axis, so that the lace  42  is wrapped around the tip  38 , as shown in FIG. 15 b . Simultaneously, the main slack pin  74  gradually recedes so as to provide slack and allow the lace  42  to be wrapped around the nozzle tip  38 , but in a way that the lace  42  is always kept taut at all times. At the end of this step, the nozzle tip  38  is positioned (as in FIG. 16) roughly between the two clove hitch retaining pins  56  and  80 , and the main slack pin  74  retreats completely within its housing  70  and is pivoted away from the area proximate the bundle  24 . 
     FIG. 16 shows how the tail cincher  86  extends into the knot area proximate the bundle  24  to take hold on the free end of the lace  42 , which is extending from the side of the nozzle tip  38 . The tail cincher  86  in the preferred embodiment is generally in the shape of a pair of tweezers or tongs and clamps the lace  42  between its two prongs. In alternate embodiments, however, the tail cincher  86  could be of any shape and could use any other means of clamping the lace  42 . 
     While the free end of the lace  42  is being held by the tail cincher  86 , the nozzle tube  36  then retracts into the nozzle housing  32 , so as to begin pulling taut the knot being formed. In FIG. 17 a , the surgeon&#39;s knot retaining pin  90  extends from the extension pin housing wall  52  within the surgeon&#39;s knot retaining pin track  92  (shown in FIG. 17 b ). The two clove hitch retaining pins  56  and  80  twist as necessary so that their respective grooves  58  and  82  release the lace  42  and then the pins  56  and  80  retract within the wall  52 . At this point, the tail cincher  86  twists approximately 180 degrees. 
     FIG. 18 shows the surgeon&#39;s knot retaining pin  90  after it has traveled as far as necessary along the track  92  to take up the slack between the nozzle tip  38  and the knot  98 . The lace  42  has been caught in the groove  94  (not shown) of the pin  90 , and the pin  90  retracts within the wall  52  until the lace  42  touches the wall  52 . 
     In FIG. 19, the nozzle assembly  30  has journeyed back along the nozzle tracks  40  counterclockwise approximately to the starting position. The tail cincher  86  now also retracts, with the result that the lace  42  is pulled tightly between the tail cincher  86  and the nozzle tip  38 , and the surgeon&#39;s knot  98  is finished. 
     Upon the completion of the knot  98 , the tail cincher  86  releases the free end of the lace  42 . Simultaneously, the cutting edge enters the proximity of the knot roughly between the knot  98  and the surgeon&#39;s knot retaining pin  90 . After the cutting edge has cut the lace  42 , the new free end of the lace  42  is carried by the retaining pin  90  back down the track  92  to be clamped to the clamp  46  on the wrapping ring  44  in preparation for the next application.