Patent Publication Number: US-6669130-B2

Title: Feeding string

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to feeding string, more particularly to a method of and apparatus for precision feeding of string forward to apparatus in which string is utilized. 
     The invention is especially concerned with feeding string forward from a supply to apparatus in which predetermined lengths of string are utilized, such as a high speed stringer for attaching string to items. 
     The term “string” as used herein encompasses what is ordinarily regarded as “string” as well as flexible string-like strands. 
     BRIEF SUMMARY OF THE INVENTION 
     In general, the method of the invention feeds string forward from a supply. The method comprises entraining the string coming from the supply around at least one feed roll, driving the roll in the direction for feeding the string forward, subjecting the string to a force in the reverse direction upstream from the roll, and subjecting the string to a forwarding force downstream from the roll. Apparatus of the invention generally involves a feed roll, a motor for driving the feed roll in the direction for feeding the string forward, a retarder for subjecting the string to force in the reverse direction upstream from the roll for retarding its forward feed, and an accelerator for subjecting the string to a forwarding force downstream from the roll for exerting a pull on the string to tension the portion of the string between the retarder and the accelerator. 
     Other features will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a semi-diagrammatic view of a first version of apparatus of this invention, said apparatus carrying out the generic method of the invention and a first species of the method; 
     FIGS. 2 and 3 are enlarged longitudinal cross-sections of what are termed a “retarder” and an “accelerator” of the apparatus shown in FIG. 1; 
     FIG. 4 is a cross-section generally on line  4 — 4  of FIG. 1 on a larger scale than FIG. 1; and 
     FIG. 5 is a semi-diagrammatic view of a second version of the apparatus, which also carries out the generic method and a second species of the method. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, an apparatus of this invention for carrying out the method of this invention, designated  1  in its entirety, is shown to comprise at least one feed roll and specifically two rolls  3  and  5  for feeding forward string S pulled from a supply  7 . The supply  7  is shown as a cop of string, i.e., a wound supply on a conical bobbin. The string S coming from the supply (i.e., being unwound from the cop) is entrained around the rolls in a manner to be described, first around the first roll  3  and then around the second roll  5 . Each roll is adapted to be positively driven in the direction for the forward feed of the string (as entrained around the rolls). 
     At  9  is generally indicated what may be broadly termed a retarder, operable as a drag brake or decelerator, for subjecting the string coming from the supply to force in a reverse direction with respect to the forward feed direction for retarding its forward feed. The retarder is interposed between the supply  7  and the first roll  3 , i.e., upstream from the first roll. At  11  is generally indicated what may be broadly termed an accelerator for subjecting the string coming from the second roll  5  (i.e., downstream from the second roll) to a forwarding force. Being retarded (held back, in effect braked) upstream from the rolls and accelerated (pulled forward) downstream from the rolls, the reach of string entrained around the rolls is tensioned and travels around the rolls in good contact therewith. 
     Each of the rolls  3  and  5  is preferably a godet roll (i.e., a plastic-coated steel roll) of elongate cylindrical form. Roll  3  is on an axial shaft  13  and roll  5  is on an axial shaft  15 . Shaft  13  is journalled in inboard and outboard bearings  17  and  19  and shaft  15  is journalled in inboard and outboard bearings  21  and  23 . The axis  13 A of roll  3  and the axis  15 A of roll  5  (and hence the rolls) are oriented at an acute angle  2  to one another, divergent from the ends of the rolls at the inboard bearings  17 ,  21 . Angle  2  may range from about two degrees to about thirty degrees, and in one embodiment angle  2  is about twelve degrees. The rolls are mounted in close proximity to one another. 
     Indicated at  25  in FIG. 1 is an electric motor, specifically a servomotor, for driving the rolls  3  and  5  via a gearbox  27  The output shaft  29  of the motor is coupled as indicated at  31  to the input shaft  33  of the gearbox. The latter is a reversing speed-reducing gearbox containing gearing for driving two output shafts  35  and  37  in opposite directions. The output shaft  35  of the gearbox is coupled as indicated at  39  to the roll shaft  13  and the output shaft  37  of the gearbox is coupled as indicated at  41  to the roll shaft  15 . 
     The retarder  9  comprises an instrumentality which may be termed a venturi. The retarder  9  subjects the string to force in the reverse direction with respect to the forward feed of the string by gas flow, more particularly by a flow of air. The venturi which has been used is a commercially available item, in particular an EXAIR® unit sold by Exair Corporation of Cincinnati, Ohio. As shown in FIG. 2, this unit comprises a tubular body designated  43  in its entirety open at both ends having a central section  45  and end sections  47  and  49  (on opposite sides of the central section). Further, the unit has a passage  51  through the body  43  having an upstream section  53 , an intermediate section  55  and a downstream section  57 . The central section  45  of the body  43  has an annular plenum chamber  59 . An air inlet  61  supplies air from a source under pressure (not shown) to the plenum chamber  59 . Ports or nozzles  63  extend at an angle from the plenum chamber  59  to the central section  55  of the passage  51  for injecting air under pressure into section  55  in the direction of section  53  of the passage  51 . Air blows out of the ports and through section  53  (note air direction arrows A in FIG.  2 ). String S, coming from the supply  7  (e.g., cop), travels through the passage  51  generally out of contact with the body  43  of the venturi  9 , and is retarded in its travel by action of the air blowing on the string. 
     The accelerator  11  comprises a venturi similar to the retarder  9  but oppositely oriented as shown in FIG. 3 with from the retarder  9  as it appears in FIG.  2 . String S, coming from the supply  7 . travels first through section  53  then through sections  55  and  57  of the passage  51  of retarder  9 , but string S, coming from the roll  5 , travels first through section  57  then through sections  55  and  53  of the passage  51  of accelerator  11 . String S traveling through the venturi  11  travels out of contact with the body  43  of venturi  11 . Air blows out of the ports  63  of accelerator  11  and through section  53  of passage  51  of accelerator  11 , thus subjecting the string to an accelerating force. 
     The string S, coming from the supply  7  and threaded through the upstream venturi  9  is entrained around the first and second godet rolls  3  and  5  in a figure-8 path. As shown in FIG. 4, the entrainment involves the string first passing under and for about a one-quarter turn T 1  around roll  3 , then over and around roll  5  in almost a full turn T 2 , then back and over and around roll  3  in almost a full turn T 3 , then forward over and around roll  5  in almost a full turn T 4 , then back and over and around roll  3  in almost a full turn T 5 , and then forward and around roll  5  in about a one-quarter turn T 6 , then being threaded through the downstream accelerator  11 . The turns are spaced axially on the rolls. As will be appreciated by those skilled in the art, the spacing between turns is dependent on the angle  2  between the axes  13 A,  15 A of the rolls  13 ,  15 . The spacing increases with the angle  2 . 
     During operation of the apparatus  1  of the present invention, predetermined lengths of string S are fed forward, issuing from the downstream accelerator  11  and fed to apparatus (not of this invention and not shown) in which the lengths of string are utilized. Rolls  3  and  5  are continuously driven by servomotor  25  via the gearbox  27  each in the direction for feeding the string forward in recurring cycles. During each cycle, the rolls  2  and  5  are first driven at a relatively low rate of speed (e.g., at a speed for feeding the string forward at 600-800 feet per minute), then sped up and driven at a higher rate of speed (e.g., at a speed for feeding the string forward at about 1200 feet per minute), then slowed down and driven at the aforementioned relatively low rate of speed. This slow-fast-slow cycle is obtained by controlling the servomotor  25  by a controller  59 . The servomotor and controller which have been used are commercial item, in particular an ALLEN-BRADLEY® Model A320P-HKC22AA AC Servomotor and an ALLEN-BRADLEY® Model 1394 Servo Drive Control System, each of which are sold by Allen-Bradley Company Inc. of Milwaukee, Wis. The slow-fast-slow cycle typically involves operation at the slow speed for the first ¼ of the cycle, ramping up the speed to the high speed in the next ¼ of the cycle, running at the high speed for the third ¼ of the cycle, and slowing down to the low speed in the last ¼ of the cycle. The length of string fed forward on each cycle is determined by the number of revolutions of rolls  3  and  5  in the cycle, and the number of revolutions of the rolls during each cycle is a matter of the setting of the controller to operate the servomotor for the requisite number of revolutions of the rolls in each cycle interval. A typical setting where the rolls  3  and  5  are each four inch diameter rolls, making their circumference 12.57 inches ( 4 B), is for rotation of the rolls roughly 1.23 revolutions in each cycle for feeding 15.5 inches of string on each cycle. 
     The retardation of the string by the upstream retarder  9  and the acceleration of the string by the downstream accelerator  11  subjects the string passing around the rolls  3  and  5  to tension which, though relatively low, is sufficient to maintain the string in relatively intimate frictional contact with the rolls, thus tending to insure accurate feeding of the string. This is achieved even when feeding the string at the non-constant rate as described above to feed apparatus utilizing the string at a non-constant rate. The angling and spacing of the rolls tends to prevent tangling of the turns on the surface of the rolls. 
     While the above-described method and apparatus continuously feed the string S forward in slow-fast-slow cycles (i.e., at a non-constant rate), the method and apparatus may be such as to feed the string forward continuously at a constant (invariant) rate. Such method and apparatus is illustrated in FIG. 5, being the same as illustrated in FIGS. 1-4 except that only the roll  5  is positively driven by an electric motor/speed reducer unit  71 . Roll  3  idles under the torque imparted thereto by the string. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     When introducing elements of the present invention or the preferred embodiments thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.