US3662678A - Coil tightener - Google Patents

Abstract

Coil tightening and tying system provides a strap loop having overlapping end portions in circling relation to the coil, establishes travel-retarding engagement of strap at a single intermediate location between the ends of the loop, shrinks the portion of the loop between one of the end regions and the circumferential location into gripping contact with the outer coil convolution, and produces relative rotary movement between the coil and the strap of the loop in a direction to rotate the outer convolution of the coil in a volute direction while maintaining the engagement to maintain gripping contact with the outer convolution.

Description

United States Patent Johnson 1 May 16, 1972 [54] COIL TIGHTENER Primary ExaminerBilly .l. Wilhite [72] Inventor. Robert A. Johnson, Flossmoor, Ill. Atwmey wi"iam P- Porcel [73] Assignee: Interlake Steel Corporation, Chicago, lll.

[57] ABSTRACT [22] Filed: June 23, 1970 Appl. No.: 49,047

References Cited UNITED STATES PATENTS 4/1967 Lems 100/3 Coil tightening and tying system provides a strap loop han'ng overlapping end portions in circling relation to the coil, establishes travel-retarding engagement of strap at a single intermediate location between the ends of the loop, shrinks the portion of the loop between one of the end regions and the circumferential location into gripping contact with the outer coil convolution, and produces relative rotary movement between the coil and the strap of the loop in a direction to rotate the outer convolution of the coil in a volute direction while maintaining the engagement to maintain gripping contact with the outer convolution.

2 Claims, 12 Drawing Figures ROBERT A- Jol/N-SoN ,5 PQMML VQQ PHENTEDMM 16 m2 SHEET 2 BF 5 INVENTOR /0BER7 A. J'oHNsoN Adda. fi ww;

ATTORNEY PATENTEUMM 16 m 3,662.67'8

SHEET M []F 5 con. TIGI-ITENER BACKGROUND OF THE INVENTION The present invention relates to the art of strapping apparatus and more particularly to strapping machines of the type capable of tightening a spiral coil and applying a strap loop about the tightened coil.

The technique of using the binder strap or band as the coilgripping element during the coil-tightening operation is taught in U.S. Pat. No. 3,320,874. Specifically, as disclosed in that patent, a strap loop is established snug upon the outer coil wrap or convolution and is rotated in a volute direction to impart corresponding movement of the outer coil convolution, thereby drawing the inner coil convolutions taut. Simultaneously, the strap of the loop is taken up to shrink the binder strap to maintain its snug engagement with the outer coil convolution as the coil shrinks. Rotation of the strap loop and, hence, the outer coil wrap is accomplished by moving the strapping head in an arcuate path about the coil periphery.

Instead of rotating the strapping head to effect the rotation of the loop in a volute direction, the head can remain fixed, and rotation of the strap loop in snug contact with the outer coil convolution can be produced by drawing tensioned band about the coil from a strap reservoir.

SUMMARY OF THE INVENTION The present invention relates to improved coil tightening and tying system of the latter type.

In accordance with a principal feature of the present invention, a length of band is fed by a strapping head and is looped in loosely-encircling relation about a coil. A hold-back mechanism that includes a traction wheel having controlled resistance to rotation engages the band of the loop at a single intermediate position between the opposite ends of the loop. The traction wheel cooperates with the strapping head during retraction of band by the head to prevent retraction of a predetermined segment of the length of band comprising the loop and to cause the remaining band of the loop to be shrunk into snug engagement with the outer coil convolution. When the retraction force on the strap produced by the head exceeds the preset resistance to rotation of the traction wheel, the traction wheel rotates to allow band of the restrained loop segment to be retracted so that the band of the loop rotates in clamping contact with the outer coil convolution in a volute direction to thereby draw the inner convolutions taut.

In the preferred embodiment shown herein, the traction wheel is affixed to the shaft of a hydraulic motor which is connected in a closed hydraulic circuit to a hydraulic reservoir through an adjustable flow control and release-valve arrangement.

A more specific but important feature of the present invention resides in the provision of mechanism cooperable with the head to configure the length of band that is fed into a loop of generally-keyslot shape, characterized by a generally circular main loop region that encircles a major peripheral region of the coil and a generally U-shaped open-bubble region which bulges outwardly from the coil and joins the main loop region. The traction wheel engages band at one extremity of the bubble region. During the coil-tightening operation, the band of the main loop region is shrunk into engagement with the coil and, subsequently, the traction wheel rotates to allow movement of band from the bubble region to the main loop region to effect coil-tightening rotation of the outer coil convolution. As the coil is tightened, the band of the bubble region progressively collapses upon the coil.

In the strapping system of the present invention, the strapping head and holdback mechanism are mounted to pivot in unison above a horizontally-movable carriage. Tangency-sensing mechanism controls pivotal movement of the head and hold-back mechanism to maintain the head tangent with respect to the coil periphery throughout the coil-tightening operation thereby to insure maximum tightening of the coil.

Other features and advantages of the invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a typical strapping station incorporating the coil-tightening system of the present invention;

FIG. 2 is a top-plan view of the horizontal carriage and showing the presently-preferred structural arrangement for mounting the hold-back mechanism and strapping head;

FIG. 3 is a front-elevational view, partly in section, further illustrating the mounting structure for supporting the holdback mechanism and strapping head on the horizontal carrlage;

FIGS. 4 and 5 are perspective views showing the hold-back mechanism and strapping head positioned adjacent a coil;

FIG. 6 is a detailed fragmentary view of the hold-back mechanism showing the pinch-roll mechanism, accumulator void and hydraulic motor;

FIG. 7 is a top-plan view of the pinch-roll assembly;

FIG. 8 is a sectional view taken as indicated along 88 of FIG. 7;

FIGS. 9 and 10 are fragmentary sectional views of the gated-guide track segment; and

FIGS. 11 and 12 are diagrammatic views illustrating the keyslot shaped strap-loop formed in accordance with the invention and the manner of obtaining a coil-tightening capstan effect through operation of the hold-back mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The invention relates to a system for forming a strap loop directly upon a coil and utilizing tensioning of the loop for tightening the coil. For purposes of disclosure, the invention is illustrated in a conventional strapping station, such as that shown in Winkler U.S. Pat. No. 3,252,408, and Gasper, et al., U.S. Pat. No. 3,320,874.

The principal features of the strapping station are described here to provide proper environment for understanding the operation of the strapping system of this invention, but it should be understood that the present system has application apart from the specific arrangements shown herein.

Referring to FIG. 1, the strapping machine 1 in which the invention is shown embodied consists of two bases, 2 and 3; the base 2 supports two corner posts 4 and 5, while the base 3 supports two corner posts 6 and 7. An l-beam 8 is connected between the upper ends of the two posts 4 and 5, while another I-beam 9 is connected across the upper ends of the two posts 6 and 7. Mounted between the posts 4 and 5 at the upper end is another I-beam 10. Similarly mounted between the posts 5 and 7 at their upper ends is another I-beam 11. A carriage 12 is mounted for vertical movement between the posts 4 and 5 and is supported by two chains 13 and 14 which are driven by means of sprockets at 15 attached to a shaft 16. Likewise, a carriage 17 is mounted for vertical movement between the two posts 6 and 7, and is supported by means of two chains 18 and 19 driven by means of two sprockets at 20 geared to the shaft 16. The shaft 16 is driven in one direction or another by means of a motor 21 suitably mounted on a platform 22 secured to the post 7. Y

The chains 13 and 14 are connected at their opposite ends to a counter-weight 23 which is guided along the post 5. In a similar manner, the opposite ends of the chains 18 and 19 are secured to another counter-weight 24 guided along the corner post 7. With this arrangement, rotation of the shaft 16 by the motor 21 in one direction causes both carriages l2 and 17 to be lowered together, while rotation of the shaft 16 by the motor 21 in the opposite direction causes both carriages I2 and 17 to be elevated.

The carriage 17 supports a horizontal slide carriage 26 which is mounted for movement toward and away from the object to be strapped on the two end plates 17A and 17B of the carriage 17. Each of the end plates is provided with a plurality of outboard rollers 17C positioned to roll along the vertical post members 6 and 7 to maintain positional stability of the carriage 17 as it is raised or lowered by the chains 18 and 19. Additionally, plates 17A and 17B are provided with inboard rollers 17D arranged in the two horizontal rows which receive and guide the side rails 26R of the slide carriage 26 and permit movement of the carriage through a predetermined path in a horizontal plane. The carriage 26 is stabilized by front and rear cross-brace structures 26A and 26B (FIG. 2), each rigidly connected to each of the side rails 26R.

As will be described in detail below, the horizontal slide car riage 26 carries a strapping head 25 and a hold-back mechanism H. The strapping head 25 can be of many types, but 'one particularly suited for such a structure is shown in U.S. Letters Pat. No. 3,120,171, which was issued on Feb. 4, 1964, in the name of M. B. Hall, et al. Such a strapping head automatically feeds a length of strap from a supply source, permits the length of strap to be encircled into a strap loop, automatically shrinks the strap loop onto an object, and secures the overlapping ends of the strap loop together and severs the strap loop from the supply source.

A strap guide segment 27 carried on the strapping head 25 is positioned vertically by movement of the carriage l7, and a corresponding strap-guide segment 30 is positioned vertically by movement of the carriage 12. The carriages 12 and 17 move in synchronism between an upper position wherein the strap guide segments 27 and 30 are in a common horizontal plane with strap guide segments 28 and 29, and a lower position which is pictured in FIG. 1. As will be described, the system of the present invention incorporates a gated-guide track segment 101 which is permanently affixed in alignment with strap-guide segment 29 and which, together with guide segments 27, 28, 29 and 30, cooperatively define a generallycircular continuous path guideway or chute beginning and ending at the strapping head 25. The strapping head 25 is operable to feed strap through this guideway to form a closed circular loop of strap at the elevated position. As described in the aforesaid Gasper, et al., U.S. Pat. No. 3,320,874, after the coil is in proper position, and after the strap loop is formed, the carriages l2 and 17 descend to lower the loop of strap to a position illustrated in FIG. 1 to encircle at mid-height region of the coil. Concurrently, the strapping head 25 is moved toward the coil on the horizontal slide carriage 26.

Referring to FIGS. 2 and 3, the supporting structure for the strapping head 25 and hold-back mechanism H includes a lower mounting plate 50 having a pair of oppositely-extending arms 50A and 50B and an outwardly-projecting V-shaped central body portion 50C that is affixed rigidly to the horizontal carriage 26, such as by directly welding the underside of v the V-shaped main body portion 50C to the carriage crossbar 26B and by connecting the terminal end arm 50A to the carriage crossbar 26A by a bolt 52. A bearing support plate 54 is welded to the lower mounting plate 50 to mount a bearing block 56. A strapping head sub-plate 58 is pivotly supported above mounting plate 50 at a pivot point A in a manner to be described in greater detail below and is additionally supported by bearing block 56 so that it is free to rotate about pivot point A above the mounting plate 50. As will be described, rotation of the strapping head subplate 58 is controlled by a cylinder 60 that has its rear end 60A pin-mounted to carriage crossbar 26A through mounting plates 62 and 64, and which has its piston rod 608 drivingly connected to sub-plate 58 through clevis 66.

A tangency-sensing element B (FIGS. 2, 3 and 4) is mounted in rotatable relation between the plates 50 and 58 at the pivot point A. The sensing element B includes a central vertical hub 67 that is journaled on a pivot shaft 67A which had its opposite ends carried in the plates 50 and 58. They sensing element B has a forwardly diverging cam arm 67B radiating from the hub 67 carrying a pair of cam rollers 68,

cam

normally located in partially-projecting relation through the open-front face of the tangency-sensing unit B. Finally, the sensing element B has a sidewise-radiating switch-actuating arm 67C centered between a pair of limit switches 60 and 62 that are fixed to the plate 58.

The strapping head 25 is mounted to sub-plate 58 so that the center line of rotation of the tangency-sensing assembly B coincides with the center line of sealer jaws 25.] of the head 25. When the head 25 is tangent to the coil periphery, the rollers 68 engage the coil evenly and the actuating arm 67C remains centered between the limit switches 60 and 62. When the head 25 inclines a predetermined extent from tangency in either direction, the rollers 68 sense the change and cause the actuating arm 67C to operate a corresponding one of the limit switches 60 and 62 for adjusting the head position through the action of cylinder 60 effecting rotation of the strapping head sub-plate 58. I

The above-mentioned hold-back mechanism H is similarly mounted on the strapping head sub-plate 58. Basically, the hold-back mechanism H consists of a hydraulic motor M on whose shaft is mounted a traction wheel 70. As will be described, the motor M is connected in a closed hydraulic circuit to a hydraulic reservoir 72 through an adjustable flow control and release valve arrangemenLThe traction wheel 70 is located to align with a void space 74 between a pair of spaced plates 76 and 78 which are mounted in spaced parallel relation above sub-plate 58 by means of spacer rods 80, 81. This alignment is also coincident with the strap track section 90 and the track assembly 91 mounted to the strapping head 25 (FIGS. 4 and 5), and the strap guide segment 27 which guides the band from the strapping head to the first overhead track section 30.

As best shown in FIGS. 6 to 8, a pinch-roll assembly 82 works in conjunction with the traction wheel 70 and includes an idler wheel 83 swingable between an upright position facing the traction wheel and a retracted position (shown in dotted line indicated at 83 in FIG. v6) spaced therefrom below plate 78 to accommodate formation and collapse of the bubble portion of the strap loop, as will be described hereinbelow.

The sub-plate 58 serves to support the pinch-roll assembly 82 and, for this purpose, includes an upstanding support 86 (FIGS. 7 and 8) along which a plate clevis 92 (FIG. 7) is secured by means of bolts 86B. A cradle-like frame 84, generally L-shaped in plan elevation (see FIG. 7), is pivoted on a vertical pin 94 which is supported between integral wings 92W of the plate clevis 92. As shown in FIG. 7, a rectangularsleeve structure 96 is secured to the edge of the cradle 84 and includes a pair of flange bearings 98 that mount a shaft 100 for rotation about a horizontal axis 100H, which is located beneath the plane of the plate 78 that serves as the bottom boundary of the void space 74. The shaft 100 carries-a radially-projecting arm structure 102 which mounts the idler wheel 83. Rotation of shaft 100 swings the radial arm 102 about the horizontal axis 1001-1 (FIG. 7).

Rotation of shaft 100 is controlled by a cylinder 104 which actuates a piston rod 106. The piston rod 106 carries a clevis 108 at its free end, the clevis being connected to a crank arm 110 by means of a pivot pin 108?. The cylinder 104 is provided with side-wise-extending shaft stubs 112, 114 swingmounted to the frame 84 by journaling the stubs 112, 114 within a flanking pair of depending bearings 116, 118 shown secured to the frame by bolts 120. To accommodate limited pivotal movement of cylinder 104, sub-plate 58 (FIG. 6) is cut out as at 122 (FIG. 6), and the frame 84 is hollowed or recessed as at 124. A positive stop arrangement accurately determines the limit of swinging movement of the idler wheel 83 to permit accurate alignment with the traction wheel 70. The stop arrangement is shown as including outboard plate 126 located at one extremity of the frame 84 and carrying an adjustable set screw 130. A plate 128 is secured to the rectangular sleeve 96 by weld 128W (FIG. 7) to mount the outboard plate 126. The set screw 130 is engageable with the crank arm 1 10 to determine proper orientation of the idler wheel 83.

The strap in void space 74 is held against movement by the action of the traction wheel 70 which is connected in mechanical driving engagement with the hydraulic pumping circuit (FIG. 11) that functions as the braking means of the hold-back mechanism H. A gear hydraulic-type motor M is shown in the circuit to effect pumping of hydraulic fluid in the direction of the arrows when the traction wheel 70 rotates in a direction to accommodate return of strap toward the strap supply. The resistance to pumping flow and, hence, the braking resistance that the motor M presents to the traction wheel 70 is controlled by a release valve RV and a flow control valve CV.

The pinch-roll assembly serves to insure loading of the strap against the traction wheel 70 with sufficient force to preclude slippage. For this purpose, the frame 84 is normally urged in a clockwise direction as viewed in FIG. 7 by the action of a bias spring 132 which reacts between the stationary clevis plate 92 and the frame 84. In the illustrated arrangement, the bias spring 132 is of the expansion type and is shown mounted in telescoping relation upon a bolt 134. The bolt 134 projects through a clearance opening 136 in plate clevis 92 and is threadedly engaged in a tapped hole 138 in frame 84 to accommodate lengthwise adjustment for varying the compression force exerted by the spring 132. In addition, the plate clevis 92 is provided with an adjustable stop 140 which determines the limit position of rotation of the frame 84 in order to gauge the nip between idler wheel 83 and the traction wheel 70 to the thickness of the strap.

OPERATION As stated, when the carriages 12 and 17 are in their upper position, adjacent ends of the guide segments 27, 28, 29, and 101, are aligned and cooperatively define a generally-circular continuous path guideway or chute beginning and ending at the strapping head 25. It will be noted that when the vertical carriage 17 is at the elevated position and the horizontal carriage 26 is retracted, the gated-guide segment 101 covers the accumulator void 74 (FIGS. 1, 9 and 10) and guides the strap being fed into the overhead track to the strapping head 25. The gated-guide segment 101 includes a fixed gate portion 101A and a movable gate portion 1018 which interengage to define a strap guideway 101C. The movable gate portion 1018 is raised and lowered by means of cylinder 146. A limit switch 148 is positioned above the movable gate portion 1013 to be activated upon raising of the gate portion 101B.

After strap feed has started and the leading edge of the strap re-enters the strapping head 25, strap feed stops when the leading end has entered the sealer jaws 25.] of the head 25. This leading end of the strap or band is then held by the gripping jaws which signal the gate portion 101B to be elevated by cylinder 146 thereby closing switch 148. Closing of switch 148 signals additional strap feed by the strapping head. Since the leading end of the band is restrained by the guide segments 27, 28, 29 and 30, the band will bubble out from the open-sided track created when gate portion 1013 was raised and into the void space 74 (hereinafter called the accumulator void 74) between plates 76 and 78. The duration of this over-feed is controlled by a time delay relay (not shown) and can be adjusted to provide any desired length of strap. In normal usage, approximately 48 to 60 inches of overfeed is sufficient to provide for the subsequent coil-tightening function. When the strap enters the accumulator void 74, its presence is sensed by switch 142 (FIG. 6) through the action of the pivoted actuator arm 144 being urged upwardly by the incoming strap. Upon completion of the over-feed, the cylinder 104 is actuated to swing the idler wheel 83 of the pinch-roll assembly 82 upward through opening 78A in plate 78 to the position shown in full lines in FIG. 6. The strap is pinched between the idler wheel 83 and the traction wheel 70 on hydraulic motor M.

A unique keyslot configuration of the loop of strap is formed as a result of raising the gated-guide track segment 101 during strap over-feed. As shown in FIG. 11, the keyslot loop is characterized by a generally C-shaped main loop region ML and a generally U-shaped open-bubble region U outwardly projecting therefrom. It will be noted that the traction wheel 70 of the hold-back mechanism H is in travel-retarding engagement of the strap at a single intermediate circumferential location C at one extremity of the U-shaped region between the lead end L and the supply strap region SS of the strap loop S.

The closed loop of strap is formed into the keyslot configuration while the carriages 12, 17 are elevated. Thereafter, the carriages 12, 17 are lowered to strip the strap from the stationary guide chutes and position the loop in loosely-encircling relation about the coil at the lower phantom-line position indicated in FIG. 1.

When the strap loop is lowered to the position shown in FIG. 1, the carriage 26 begins to move toward the coil, and the tangency-sensing mechanism B operates to position the sealer jaws of the strapping head in tangency with respect to the coil. During this time, the strapping head 25 begins to pull slack strap to shrink the portion of the loop between the supply strap portion SS and the circumferential location C into gripping contact with the outer coil convolution, as shown in FIG. 12. The hold-back assembly H at this time prevents movement of strap from the U-shaped open-bubble portion U of the loop S. As explained in the aforementioned patents, when carriage 12 is lowered, support arms 34 are caused to be pivoted into contact with the face of the coil. This provides support for the loop portion of band as it is shrunk around the coil.

The amount of hold-back or restraining force supplied by the traction wheel 70 on the strap can be varied by adjustment of the closed loop hydraulic circuit of the hold-back mechanism H, which is illustrated in FIG. 11. Rotation of the traction wheel 70, (as a result of strap being drawn from the U-shaped bubble portion U) turns the motor M causing fluid flow in the directions of the arrows (FIG. 11). The amount of flow, and hence, the resistance of motor M to rotation is controlled by release valve RV and flow control valve CV in the closed hydraulic circuit. In practice, the valves RV and CV are adjusted so as to generate sufficient rotation resisting force at traction wheel 70 to allow the friction clamping force between the outer coil convolution and the main loop region to exceed forces on the coil which would operate in opposition to attempted rotation thereof.

When continued pull exerted by the strapping head 25 overcomes amount of hold-back force generated by the hold-back mechanism I-I, strap is withdrawn from the bubble portion U, while'the strap in the main loop portion is established in a travelling capstan" effect on the coil. Continued motion of the strap under the influence of these forces effects a wrapping action on the coil. As the strap continues to move about the coil, the open-bubble portion U collapses as shown dotted in FIG. 12.

When the wrapping action has drawn the coil convolutions to their maximum tightness, the strap continues to move about the coil to exhaust the length of strap of the open-bubble portion U. Just prior to total collapse of the bubble U, the pivoted switch actuator arm 144 drops due to the absence of band in the accumulator void 74. This signals cylinder 104 to swing the idler wheel 83 to a retracted position beneath the void space, releasing the hold on the strap and permitting complete collapse of the bubble region U. The swing of the idler wheel is toward the coil to avoid tangling of the strap being collapsed toward the coil. The retracing means of the strapping head 25 continues to withdraw strap, thereby quickly taking up slack created by the release until the strap is again tight around the coil. The seal joint is then completed and the strap sheared by the strapping head, thus completing a tightening and tying cycle.

It should be noted that minimal destructive forces are applied to the strap during a cycle of operation, so that the strap which is ultimately bound about the tightened coil retains its original strength and durability. This results from the fact that the strap is engaged at a single intermediate location along the strap loop between a rotatable traction wheel and an idler wheel. Thus, maintenance of the required tensioning of the strap during retraction is accomplished without subjecting the strap to destructive bending forces or heating due to frictional engagement. Moreover, the tensioning can be easily and precisely controlled through adjustmentof the hydraulic circuit valves so that destructive sliding of the strap against the outer coilconvulsion is minimized.

The single point engagement technique in accordance with the present invention results in the strap loop being in full girth tight engagement with the coil only after the coil is finally and fully tightened.

Thus, while preferred constructional features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In an apparatus for tightening a spiral coil of strap through rotation of the outer coil convolution in a volute direction, feed means for feeding strap, means cooperating with said feed means for forming strap into a substantially closed strap loop of generally keyslot shape characterized by a generally circular main loop region and a generally U-shaped open bubble region extending outwardly from the main loop region, retracting means for withdrawing strap of the strap loop, and hold-back mechanism that includes a traction wheel engageable with braking means having a predetermined resistance to rotation, the traction wheel being engageable with the strap of the strap loop at a single intermediate location therealong and cooperable with the retracting means for tensioning strap of the main loop region to effect friction clamping engagement thereof with the outer coil convolution and thereafter controllably limiting withdrawal of strap from the bubble region to the main loop region to thereby effect progressive collapse of the strap of the bubble region upon the outer coil convolution accompanied by coil tightening rotation of the outer coil'convolution, said braking means comprises a closed hydraulic circuit having pumping means driven by rotation of the traction wheel and flow restricting means determining the resistance to rotation of the traction wheel.

2. In an apparatus for tightening a spiral coil of strap through rotation of the outer coil convolution in a volute direction, feed means for feeding strap, means cooperating with said feed means for forming strap into a substantially closed strap loop of generally keyslot shape characterized by a generally circular main loop region and a generally U-shaped open bubble region extending outwardly from the main loop region, retracting means for withdrawing strap of the strap loop, and hold-back mechanism that includes a tractionwheel engageable with braking means having a predetermined resistance to rotation, the traction wheel being engageable with the strap of the strap loop at a single intermediate location therealong and cooperable with the retracting means for tensioning strap of the main loop region to effect friction clamping engagement thereof with the outer coil convolution and thereafter controllably limiting withdrawal of strap from the bubble region to the main loop region to thereby effect progressive collapse of the strap of the bubble region upon the outer coil convolution accompanied by coil tightening rotation of the outer coil convolution, said hold-back mechanism includes a shiftably mounted frame, an idler wheel, means for swinging the idler wheel about an axis offset from the plane of the strap loop between a strap pinching position within the bubble region and facing the traction wheel and a retracted position adjacent the coil and spaced from the bubble region,

and means biasing the frame in a direction to load the idlerwheel towards the traction wheel, the swinging means includes a hydraulic cylinder and piston mechanism operable after forming of the bubble region to swing the idler wheel to the strap inching osition and responsive durin withdrawal of strap rom the Bubble region to swing the id er wheel to the retracted position, said braking means comprises a closed hydraulic circuit having pumping means driven by rotation of the traction wheel and flow restricting means determining the I resistance to rotation of the traction wheel.

l l l I

Claims (2)

1. In an apparatus for tightening a spiral coil of strap through rotation of the outer coil convolution in a volute direction, feed means for feeding strap, means cooperating with said feed means for forming strap into a substantially closed strap loop of generally keyslot shape characterized by a generally circular main loop region and a generally U-shaped open bubble region extending outwardly from the main loop region, retracting means for withdrawing strap of the strap loop, and hold-back mechanism that includes a traction wheel engageable with braking means having a predetermined resistance to rotation, the traction wheel being engageable with the strap of the strap loop at a single intermediate location therealong and cooperable with the retracting means for tensioning strap of the main loop region to effect friction clamping Engagement thereof with the outer coil convolution and thereafter controllably limiting withdrawal of strap from the bubble region to the main loop region to thereby effect progressive collapse of the strap of the bubble region upon the outer coil convolution accompanied by coil tightening rotation of the outer coil convolution, said braking means comprises a closed hydraulic circuit having pumping means driven by rotation of the traction wheel and flow restricting means determining the resistance to rotation of the traction wheel.

2. In an apparatus for tightening a spiral coil of strap through rotation of the outer coil convolution in a volute direction, feed means for feeding strap, means cooperating with said feed means for forming strap into a substantially closed strap loop of generally keyslot shape characterized by a generally circular main loop region and a generally U-shaped open bubble region extending outwardly from the main loop region, retracting means for withdrawing strap of the strap loop, and hold-back mechanism that includes a traction wheel engageable with braking means having a predetermined resistance to rotation, the traction wheel being engageable with the strap of the strap loop at a single intermediate location therealong and cooperable with the retracting means for tensioning strap of the main loop region to effect friction clamping engagement thereof with the outer coil convolution and thereafter controllably limiting withdrawal of strap from the bubble region to the main loop region to thereby effect progressive collapse of the strap of the bubble region upon the outer coil convolution accompanied by coil tightening rotation of the outer coil convolution, said hold-back mechanism includes a shiftably mounted frame, an idler wheel, means for swinging the idler wheel about an axis offset from the plane of the strap loop between a strap pinching position within the bubble region and facing the traction wheel and a retracted position adjacent the coil and spaced from the bubble region, and means biasing the frame in a direction to load the idler wheel towards the traction wheel, the swinging means includes a hydraulic cylinder and piston mechanism operable after forming of the bubble region to swing the idler wheel to the strap pinching position and responsive during withdrawal of strap from the bubble region to swing the idler wheel to the retracted position, said braking means comprises a closed hydraulic circuit having pumping means driven by rotation of the traction wheel and flow restricting means determining the resistance to rotation of the traction wheel.

Images