Knots and knot tying – Methods
Reexamination Certificate
2000-06-20
2001-08-28
Calvert, John J. (Department: 3765)
Knots and knot tying
Methods
C289S001200, C289S017000, C289S018100
Reexamination Certificate
active
06279970
ABSTRACT:
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'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'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's knot to secure the clove hitch, because this combination of clove hitch and surgeon's knot is the FAA-approved method of tying wire harnesses. Military specifications also require use of the clove hitch/surgeon'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'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 butto
Calvert John J.
Oliver Polly L.
Welch Gary L.
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