US3082797A - Method and apparatus for bending wire - Google Patents

Description

March 26,- 1963 s. A., PLATT 3,032,797

METHQD AND APPARATUS FOR BENDING WIRE Filed Nov. 7. 1958 '7 Sheets-Sheet 1 i E I m m -T 2 1 g f A i H my INVENTOR.

STEPHEN A. PLATT L BY M M March 26, 1963 s. A. PLATT 3,082,797

METHOD AND APPARATUS FOR BENDING WIRE Filed Nov. 7, 1958 v 7 Sheets-Sheet 2 INVENTOR. STEPHEN A. PLATT ATTORNEYS March 26, 1963 s. A. PLATT 3,032,797

METHOD AND APPARATUS FOR BENDING WIRE Filed Nov. 7, 1958 '7 Sheets-Sheet 3 INVENTOR. STEPHEN A. PLATT A TTORNE Y5 March 26, 1963 s. A. PLATT METHOD AND APPARATUS FOR BENDING WIRE 7 Sheets-Sheet 4 Filed NOV. 7, 1958 .En m lmmu &

INVENTOR. STEPHEN A. PLATT March 26, 1963 s. A. PLATT 3,082,797

METHOD AND APPARATUS FOR BENDING WIRE Filed Nov. 7, 1958 7 Sheets-Sheet 6 INVENTOR. 5O STEPHEN A. PLATT A T TORNE Y5 March 1963 s. A. PLATT 3,082,797

METHOD AND APPARATUS FOR BENDING WIRE Filed Nov. 7, 1958 7 Sheets-Sheet '7 wrm:

INVENTOR. STEPHEN PLA 7' 50 BY M ATTORNEYS United States Patent 3,082,797 lfvlETHOD AND APPARATUS FQR BENDING WIRE tephen A. Piatt, 1169 Fulton St, Grand Haven, Mich. Fiied Nov. '7, 1958, Sea. No. 772,433 4 @iairns. (Cl. 140-71) This invention relates to ways and means for bending wire. More particularly, it relates to a method and apparatus for bending wire to be used as electrical resistance, heating elements and the like.

Sinusoidally bent, wire resistance elements are used in a number of appliances, such as heating pads, grills and the like. Consequently, there is a demand for sinusoidally bent resistance wire and machines have been developed to bend wire to supply this demand. An example of such a machine is described in US. Patent No. 2,456,353 to Wolf, et al.

The machines heretofore developed have a disadvantage however, in that for a given width of resistance wire element produced thereby the amount of wire per unit ength of element is less than that desired. In short, the

amount of wire per unit area of element is unduly limited. These machines bend the resistance wire in substantially perfect sine waves. Even the most efiicient of these machines cannot form the wire closer than with parallel traverse wires or bars. Because the minimum radius of bend of resistance wire is limited by the physical properties of the wire, once the minimum bending radius has been reached, the quantum of wire per unit area of element cannot be increased in the case of such machines without damaging the wire. On the other hand, the demand of the art is for an increased thermal output per per unit area of wire element and from economic and engineering considerations, the optimum design of a bent resistance wire element calls for an increase in the amount of wire per unit area of element. This the prior art machines are incapable of delivering.

The machines heretofore developed produce sinuated element with substantially parallel bars, whether the return bends be very small or very large. Where the sinuated element can be taken direct from the machine and fabricated into its final sheath without intermediate handling, no trouble is experienced. However, large volume manufacture has made it necessary .to store finished element in continuous lengths on large reels, in large quantity, between machine and assembly lines. This calls for sinuated element with its turns touching each other to prevent interlacing of one element with another when they slip on each other, or when one element falls next to another on the production table.

Another problem that had to be met was that of crowding all the bars of sinuation per running inch or foot possible, both for maximum storage per given reel and for anti-tangling characteristics.

A general object of this invention is to develop ways and means for producing flat sinuated wire elements wherein the amount of resistance wire per unit area of element :is increased. More particularly, it is an object of this invention to provide ways and means for bending resistance wire wherein the only inherent limitation is that of the wire itself, namely, the minimum bending radius that the wire can withstand without fracturing or cracking.

Another object of this invention is a machine which produces the required element form. Extremes are now required in industry ranging from bends as short as one wire diameter up to A; inch radius. It will be seen why physical handling of such requires turns to be touching until just prior to stretching into sheath assembly.

A specific object of this invention is to provide a method for bending resistance wire into an element hav- "ice ing the maximum amount of wire per unit area of element.

Another specific object of this invention is to provide an apparatus for continuously and controllably bending resistance wire into an element having the maximum amount of wire per unit area of element.

These and other objects which may appear as this specification proceeds are achieved by this invention which shall be described in the context of the drawings wherein:

FIG. 1 is a front elevation of a preferred embodiment of the machine of this invention;

FIG. 2 is an enlarged, front, elevational view of a portion of the apparatus of FIG. 1 with a portion of the apparatus broken away to reveal interior structure;

FIG. 3 is a partial, side elevation view taken along the lines IIIIII of FIG. 1 with portions of the supporting structure of the apparatus broken away to reveal internal structure;

FIG. 4 is a fragmentary, sectional, partially broken plan view of the apparatus taken along the lines IVIV of FIG. 1;

FIG. 4a is an enlarged, plan view of the mandrels shown in FIG. 4;

FIG. 5 is a sectional, plan view taken along the lines VV of PEG. 2 and showing a portion of the bent wire travel resist means of the apparatus of FIG. 1;

FIG. 6 is a plan view of the apparatus of FIG. 1 which view has been somewhat reduced in size; and

FIGS. 7-14 are diagrammatic views illustrating progressively the relative movements of the wire feeding head and mandrels during one operative cycle of the apparatus of HG. 1.

In general, the drawings show that a basic concept of this invention is bending the wire so that it back tracks or doubles back against itself in a plane with the result that the marginal terminal loops are partially overlapped laterally of the Wire.

In terms of method, the drawings broadly disclose the steps of pushing wire under tension in a direction of travel while simultaneously in a plane looping the wire transversely to a line in said direction; first to one side of said line and then to the other side of said line, and resisting movement of looped wire in said direction of travel. The adjacent loops of the bent wire elements thus formed will usually be in contact with one another and, unless this condition is corrected, will short circuit the oppositely disposed loops under use conditions. Consequently, while not shown, the method of this invention comprises the step of separating (or breaking contact of) adjacent loops.

in terms of apparatus, the drawings broadly disclose a machine for continuously forming bent resistance wire which comprises means for pushing wire under tension in a direction of travel, means for simultaneously looping in a plane said wire transversely to a line in said direction, first to one side of said line and then to the other side of said line, and, means for resisting movement of the looped wire in its direction of travel. The sinuating mechanism has a wire feeding head adapted to travel in a figure 8 shaped path in a plane. The mechanism also has a pair of reciprocable mandrels oppositely disposed on each side of said line of travel and adapted to move into and out of said plane in coordination with the movement of the Write feeding head. Each mandrel is adapted to move oppositely to the other and to come between the wire and the wire feeding head as said wire feeding head reverses its movement parallel to the direction of trvael of the finished wire, and to withdraw from said plane as said wire feeding head moves towards it. The movement of the feeding head in wrapping the wire around each of the mandrels pushes the sinuated or looped wire through the 3 machine. This produces the tight loop formation char acteristic of the product of this machine.

Structure In somewhat greater detail, it will be observed that the drawings illustrate a wire bending apparatus 20 into which resistance wire 21 under tension is fed and out of which a continuous, looped wire 22 emerges (FIG. 4.) The apparatus comprises a stationary table 23 having a fiat, horizontal top surface. A pair of wire bending posts or mandrels 24 and 26 extend vertically and movably through the table in slots 25 and 27, respectively. It will be observed that the mandrels 24 and 26 are oppositely disposed and are adapted by means to be later described herein to reciprocate oppositely and vertically from a position flush with, or below, the top surface of said table 23 to a position above the plane of said surface. (The line or direction of travel of wire through the machine is normal to a line between these mandrels 24 and 26.

Adjacent the table 23 and opposite said reciprocable mandrels is a movable wire feeding means or head 28 comprising a horizontally disposed bottom plate 29, the top surface of which is disposed in the same plane as that of the top surface of the table 23 (FIGS. 4 and 6). Adjacent the top of bottom plate 29 and facing one another is a pair of curved guide surfaces formed by the circumferential periphery of a horizontally disposed, preferably rotatable, disk 36 on an axial shaft 31 and by the circumferential periphery of another horizontally disposed, preferably rotatable, disk 32 on an axial shaft 33. The adjacent portions of the guide surfaces are spaced apart a distance slightly more than the outside diameter of the wire 21. Above and adjacent to said guide surfaces is a retention plate 34 attached to said bottom plate 29 as by screws 35.

Below and attached as by rivets to said bottom plate is a horizontally disposed guide plate 47 (FIG. 3). The front portion of the bottom plate (with reference to direction of travel of the unbent wire 21) is slidable in a transversely arranged track 49 between a stationary front sup port block 36 and a retaining plate 37 attached to the block. The back portion of said guide plate (again with reference to the direction of travel of the unbent wire 21) curves downwardly in sliding engagement with a movable drive rod 38. Secured to the underside of said guide plate 47 is one flange of an angle iron 39. The other flange of the angle iron 39 is in sliding contact with said drive rod 38 and in conjunction with the curved portion of the guide plate maintains the wire feeder 28 in position on said drive rod. 1 i

The drive rod 38 is pivotally secured to the ends of a pair of rocker arms 40 and 44 by pins 41 and 45, respectively (FIG. 6). The other ends of the rocker arms 40 and 44 are pivotally attached to the front support block 36 by pins 42 and 46 respectively. The rocker arms 40 and 44 are spaced axially of the rod 38. Both rocker arms, it will be noted, lie in the same plane and are transversely disposed to both the stationary front block and the direction of travel of said unbent wire 21 through the apparatus.

At the right hand end of the drive rod 38 there is mounted in the horizontal plane a roller follower assembly 48 with the axis of the roller being vertically disposed. The roller is shown in contact with the periphery of a disk cam 50 mounted on an axial shaft 51 the axis of which is likewise vertically disposed. The periphery of the disk cam 50 comprises a pair of removable cam follower tracks 52 and 54 which have inwardly curved leading and trailing edges.

At the right hand end of the drive rod 38 there is attached a spring post 56 (FIGS. 1 and 3). The post 56 mounts one end of a helical, tension spring 57. The other end of the spring 57 is attached to the stationary support structure 53 of the machine and biases the drive rod toward the disk cam 56.

The drive rod 38 in conjunction with the rocker arms 49 and 44, the cam follower assembly and the spring 57, functions to impart reciprocating backward and forward motion to the wire feeder means 28.

Transverse motion of the wire feeder means 28 is obtained by transverse motion assembly comprising a pitman (FIG. .6), one end of which is pivotally secured to the bottom plate 29 of the feeder means 28 as by a shaft pin 61. The other end of the pitrnan 60 has a head block 62. The head block 62 is secured to an anchor plate as by the bolt 63 and nut 67. The anchor plate 65 is seated in the channel 64 of the disk cam 50 for radial adjustment and detachably secured by the set screws 66.

Each of the vertically movable mandrels 24 and 26 functions as wire bending posts. The portions thereof which rise above the plane of the top surface of the table 23 are provided with outer lateral, curved, wire bending surfaces 24a and 26a (FIG. 4a) each of which has a radius of revolution corresponding to the desired radius of curvature of the loops of the sinuated wire product. In general, this radius is selected to correspond to the minimum radius at which the particular Wire being sinuated can be bent Wtihout rupture. The axis of each surface runs longitudinally through the corresponding mandrel.

Each of the vertically movable mandrels 24 and 25 is driven by a spring and cam assembly (FIGS. 2 and 3). Thus, with reference to the right hand mandrel 24 the bottom end thereof is associated with a cam follower 69, a pivot bar 107 rotatably secured to a stationary shaft 103 mounted in the stationary support structure 58 and a compression spring 68 attached to the overhead portion of the structure 58. Similarly, the bottom end of the left hand mandrel 26 is associated with a cam follower 71, a pivot bar 109 rotatably secured to the shaft 108 and a compression spring 70 attached to the overhead portion of the supporting structure 58. Both cam followers ride on a rotatable, horizontal radial cam 72. The cam 72 is mounted on and rotated by the rotatable shaft 75. The cam 72 has two adjacent cam surfaces, each of which has a constant radius for about 270 and a larger radius for about 90 about the axis of the cam whereby each cam surface comprises a lower peripheral portion 73 and a raised peripheral portion 74. The raised portion of the one cam surface is disposed 180 about the cam axis from the raised portion of the second cam surface and the radius of each raised cam surface is sufficient to project the respective mandrels 24 and 26 above the plane of the top surface of the table 23 when said cam surfaces contact the respective cam follower members of the mandrels 24 and 26. The bias of the springs 68 and 70 toward the cam 72 assures that the cam followers 69 and 70 will be in constant contact with the respective cam surfaces.

The drive shaft 75 associated with the radial cam 72 is connected to the gear box 76. By means of the gear box '76 it also drives the disk cam 50, thus synchronizing the operation of said mandrels 24 and 26 and the cam 50. The drive shaft 75 is driven from a prime mover (not shown) by means of the pulley 77.

Under operative conditions the wire feeder means 28 makes substantially a transverse figure 8 motion. Accordingly, the mandrels 24 and 26 are centered in and forgn the ends of the loops in the wire as the wire is sinuate The means for resisting movement of looped Wire in the direction of travel thereof comprises an assembly situated above the table 23 behind the mandrels (FIG. 2). This assembly comprises an inverted U-shaped frame 81 which carries a set of rubber disks 82 rotatable on a shaft 83. The shaft 83 is arranged transversely to the direction of wire travel and inserted into an aperture in each of the depending legs of the frame 81. The rubber wheels are secured axially of the shaft 83 by a pair of clamping bars 84. The clamping bars are axially adjustable along the shaft 83 to regulate the degree of resistance to rotation as a group or with respect to each other. They are clamped to an upper horizontally disposed suspension rod 85 by thumbscrews 86. The ends of the suspension rod are mounted to the depending legs of the frame 81. The cross arm 87 of the frame 81, disposed under, and adjacent to, a crossbar member '88 has a pair of upstanding guide pins 89 passing through the arcuate guide pin slots 90 in the crossbar member 88 ('FIG. 5). The crossbar has a thumbscrew assembly 91 for adjusting and setting the angular position of the frame 81 with relation to the work traveling under the rubber wheels 82.

The crossbar 88 is joined as by machine screws to the depending arms of vertically movable yoke 93, the crossbar of which is threadedly suspended on a vertically disposed adjustment stud 95. The upper end of the adjustment stud 95 passes through an overhead support frame 94, anchored to said bed block 23. A lock nut 96 threadedly attached to said thumbscrew 95 is disposed adjacent to and on top of the crossarrn of the upper U-bar 93.

The preferred embodiment of this invention also has a spring adjustment assembly for the drive rod 38 (FIG. 6). This assembly has a horizontally disposed shim bar 97, one end of which is interposed between the spring post 56 of the drive rod and the edge of .the bed block 23. The bias of the spring 57 causes the spring post to bear against the shim bar 97 when the rod 48 is at rest. A short distance from said end and on the rocker arm side of said shim bar, the bar is in contact with an arcuate fulcrum 98. The other end of the shim bar 97 is biased away from the bed block 23 by a spring 100. Byreason of position of the fulcrum 98, the shim is urged against the spring post. The end of the shim bar 97, biased outwardly by the spring 100, is urged inwardly against the spring by a thumbscrew 1G1 threadedly passing through an aperture in the vertical flange of an angle iron 102 (attached to the bed block 23). To assure retention of setting, the thumbscrew has a lock nut 103. By adjustment of the thumbscrew the axial travel of the rod '38 and thereby the fore and aft movement of the feeding head 28 may be controlled.

Also included may be means for manually moving the wire feeder means 28 to facilitate threading wire through the machine at start-up.

It may also be observed that the underside of the disk cam 50 is associated with a belt drive pulley 104 (FIG. 1) which is also keyed to the drive shaft 51. Under operative conditions this pulley may be used to drive the sinuated wire wind-up reel.

Other auxiliary structural features may also be provided, such as, for example, as shown in FIG. 6, a pair of oppositely disposed, adjustable guide plates 106 which function to guide the looped wire 22 from the machine. They also resist movement of said looped wire 22 from the mandrels.

Operation Under operative conditions resistance wire 21, as from a supply reel 116 (FIG. 4), passes through a wire tensioning apparatus 112. The wire tensioning apparatus 112 is a conventional device and is therefore not described herein. The apparatus 112 functions to establish and maintain the wire 21 at a constant and uniform tension as it is pulled into the machine 2%.

In the machine 26 the wire 21 is pulled into the wire feeding head 28 between the guide surfaces 30 and 32 by the movement of the head 28. The feeding head 28 moves in the plane of said table 23 top surface in a figure 8 path transversely to the direction of travel of said wire 21 while the mandrels 24 and 26 alternately rise above and withdraw to at least said plane. The movement of the feeding means and the mandrels 24 and 26 are so coordinated that wire emerging from said feeding head is continuously looped around the mandrels, first on one side and then on the other, and previously formed loops are pushed in the direction of travel against the resistance of the disks 82 whereby the back track in the looped wire is retained and in some cases may even be increased.

The coordination of these movements may be seen in the context of FIGS. 7l4. Thus, as shown in FIG. 7, as the wire feeder means 28 moves left from its extreme right hand position, the incoming wire 21 is positioned behind the elevated, right hand mandrel 24. As the wire feeder means 28 continues its travel to the left, the incoming wire 21 is drawn firmly about the right hand mandrel 24 by the tension applied to the wire as it is fed to the wire feeder 28. When the wire has been firmly wrapped about the mandrel 24, the left hand mandrel 26 withdraws to the top surface of the table 23 as in FIG. 8. As the right hand wiping disk 30 moves past the mandrel 24, it wipes the wire firmly against the surface of revolution of the mandrel, producing a loop having a radius corresponding exactly to that of the surface of revolution.

As its leftward movement continues, the feeder 28 moves also toward the direction of travel (backward) as in FIG. 9, thereby leading the wire behind the lowered left hand mandrel 26 and pushing the previously formed loop in the direction of travel. As the wire feeding means 28 approaches the leftward limit of its travel, it commences to move forwardly and the left hand wire mandrel 26 elevates above the level of the table 23 and blocks forward movement of the left hand portion of the wire, as in FIG. 10. Upon reaching the left hand limit of its travel, the feeder means 28 starts to move toward the right hand side of the line of travel whereupon the incoming wire 21 is engaged by the guide surface 32 and is led along therewith in the right hand direction, thereby forming a tight loop about the post 26, as in FIG. 11. As the feeder means continues its rightward movement, the right hand mandrel 24 withdraws to the level of the table 23 as in FIG. 12, and the wire feeder 28 moves rearwardly as in FIG. 13, pushing the preceding loop out of the way and leading the wire 21 behind the lowered mandrel 24. As the wire feeder 28 completes its travel to the right, the right hand mandrel 24 again rises above the level of the table 23 and the feeder 28 moves forwardly. As can be seen, the movement of the wire feeding means 28 in a continuous figure 8 motion in relationship to the continuous elevation and withdrawal movement of the mandrels 24 and 26 results in formation of tight wire loops.

The bent wire element 22 thus formed is pushed by the action of the wire feeder means 28 under the rubber wheels 82 of the movement resistance assembly 80. The various thumbscrews of this assembly are adjusted to provide sufiicient bearing and thus resistance to forward travel of element 22. This causes adjacent loops to come together as they are pushed rearwardly without decreasing the radius of the loops below the critical minimum at which fracturing occurs.

The width W (FIG. 4) of the bent wire elements 22 can be adjusted by changing the length of the stroke of the transverse motion drive rod 60. This can be accomplished by loosening the lock nut on the shaft 63 and sliding the same between the retaining plates 65 toward the drive shaft 51 to decrease the width and away from the drive shaft to increase the width. The spacing of the mandrels 24 and 26 is correspondingly adjusted.

The radius of each loop can be adjusted by substituting thicker or thinner mandrels 24 and 26 and thus a larger or smaller radius about which the wire is formed. The removable follower tracks 52 and 54 can be changed to ones of increased radial thickness for larger loops and to ones of decreased radial thickness for smaller loops. The angle of the frame 81 in relation to the sinuated wire is set to cause the sinuated wire to move rearwardly in a straight line rather than curving to either side.

The concepts of this invention have a number of advantages. In the first place, resistance Wire elements pro duced according to the teachings hereof have almost twice as much wire per unit length for a given width of element. Second, uniform and consistent loops are made. Third, the only limiting factor in the curvature of the loops is the wire itself, the radius at which the wire cracks or fractures. Fourth, the curvatures are consistently accurate. Finally, the machine embodiment of this invention can be readily adjusted to different production requirements with a minimum of effort.

Pushing the formed wire away from the mandrels 24 and 26 produces the tightest possible loop configuration with the loops along opposite sides being arranged in partially overlapping relationship rather than spaced alternate relationship. It is this that attains the objective of packing more resistance into a unit area of formed wire than was heretofore possible. This overlapping arrangement must be effected in the initial sinuation of the wire. It cannot be accomplished by attempting to close the loops once they have been formed in an open configuration.

Other features, advantages and embodiments of this invention will become apparent to those in the exercise of ordinary skill in the art in light of the preceding description. Therefore, it should be noted that as this invention may be embodied in several forms without departing from the spirit thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

I claim:

1. An apparatus for continuously forming a wide, flat, elongated band of looped resistance wire, which comprises: wire forming means for pulling wire under constant and uniform tension from a source; said wire forming means simultaneously forming loops in said wire with said loops lying in a flat plane and constituting said band, said loops extending transversely of and being alternately arranged with respect to the longitudinal center line of said band and the closed ends thereof forming the margins of said band, said wire forming means also moving said band away from said source; and means for resisting movement of said band away from said source and said wire forming means for urging the loops at the margins of said band into abutting relationship; said resisting means having a rubber-like wheel rotatably supported for rotation about an axis extending generally parallel to said loops of said band; a support for said resisting means, said resisting means being movable on said support toward and away from said band and angularly variable with relation to the direction of movement of said band.

2. An apparatus as recited in claim 1 wherein said rubber-like wheel consists of a plurality of separate disklike members arranged in side-by-side relationship along said axis; said disk-like members each being rotatable with respect to the others to provide a limited differential action for said resisting means.

3. An apparatus as recited in claim 1 wherein said wirc forming means has a head member; a pair of disks rotatably mounted on said head member, said disks being rotatable about axes normal to said plane of said band and spaced apart only sufliciently to form a passage for movement of wire therebetween; a guide supporting said head for reciprocating movement laterally of said band; driving means secured to said guide for shifting said guide and said head parallel to the direction of movement of said band.

4. An apparatus for continuously forming a wide, fiat, elongated band of looped resistance wire, which comprises: Wire forming means for pulling wire under constant and uniform tension from a source; said wire forming means simultaneously forming loops in said wire with said loops lying in a flat plane and constituting said band, said loops extending transversely of and being alternately arranged with respect to the longitudinal center line of said band and the closed ends thereof forming the margins of said band, said wire forming means also moving said band away from said source; said wire forming means having a head member; a pair of disks rotatably mounted on said head member, said disks being rotatable about axes normal to said plane of said band and spaced apart only sufficiently to form a passage for movement of wire therebetween; a guide supporting said head for sliding reciprocating movement laterally of said band; driving means secured to said guide for shifting said guide and said head parallel to the direction of movement of said band; and means for resisting movement of said band away from said wire forming means.

References Cited in the file of this patent UNITED STATES PATENTS 905,130 Ayer Dec. 1, 1908 1,273,020 Winsor July 16, 1918 1,439,411 Griner Dec. 19, 1922 2,047,717 Van Dresser et a1 July 14, 1936 2,061,579 Huyett Nov. 24, 1936 2,188,407 Horton Jan. 30, 1940 2,709,462 Schade May 31, 1955 2,747,619 Buttner May 29, 1956 2,898,949 Huszar Aug. 11, 1959

Claims (1)

1. AN APPARATUS FOR CONTINUOUSLY FORMING A WIDE, FLAT, ELONGATED BAND OF LOOPED RESISTANCE WIRE, WHICH COMPRISES: WIRE FORMING MEANS FOR PULLING WIRE UNDER CONSTANT AND UNIFORM TENSION FROM A SOURCE; SAID WIRE FORMING MEANS SIMULTANEOUSLY FORMING LOOPS IN SAID WIRE WITH SAID LOOPS LYING IN A FLAT PLANE AND CONSTITUTING SAID BAND, SAID LOOPS EXTENDING TRANSVERSELY OF AND BEING ALTERNATELY ARRANGED WITH RESPECT TO THE LONGITUDINAL CENTER LINE OF SAID BAND AND THE CLOSED ENDS THEREOF FORMING THE MARGINS OF SAID BAND, SAID WIRE FORMING MEANS ALSO MOVING SAID BAND AWAY FROM SAID SOURCE; AND MEANS FOR RESISITING MOVEMENT OF SAID BAND AWAY FROM SAID SOURCE AND SAID WIRE FORMING MEANS FOR URGING THE LOOPS AT THE MARGINS OF SAID BAND INTO ABUTTING RELATIONSHIP; SAID RESISTING MEANS HAVING A RUBBER-LIKE WHEEL ROTATABLY SUPPORTED FOR ROTATION ABOUT AN AXIS EXTENDING GENERALLY PARALLEL TO SAID LOOPS OF SAID BAND; A SUPPORT FOR SAID RESISTING MEANS, SAID RESISTING MEANS BEING MOVABLE ON SAID SUPPORT TOWARD AND AWAY FROM SAID BAND AND ANGULARLY VARIABLE WITH RELATION TO THE DIRECTION OF MOVEMENT OF SAID BAND.

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