CA1282765C - Apparatus and process for forming center unwindable rolls of perforatedplastic film - Google Patents

Abstract

APPARATUS AND PROCESS FOR FORMING
CENTER-UNWINDABLE ROLLS OF PERFORATED PLASTIC FILM
ABSTRACT OF THE DISCLOSURE
An apparatus and a method are disclosed for winding strips or tubes of plastic film into center-unwindable rolls having a diameter of at least about 3 inches and for unloading the wound rolls without telescoping thereof. Bare expandable winding shafts are provided which comprise a fixed vacuum leaf and a plurality of movable leaves controlled by an elongated air bladder, the contracted diameter being at least about one-quarter inch less than the expanded diameter. Each leaf also has an outer surface having a selected slipperiness toward the film surface.

Description

APPARATUS AND PROCESS FOR FORMING
CENTER-UNWINDABLE ROLLS OF PERFORATED PLASTIC FILM

This invention relates to methods for continuously winding transversely perforated plastic film into large-diameter rolls. It further relates to methods for transferring a moving film from a fully wound roll on a first bare winding shaft onto a second bare shaft. It especially relates to methods for enabling large-diameter rolls of perforated plastic film to be unloaded from a bare shaft.
When winding rolls of a plastic film, several problems occur because of the characteristics of the film. Slipperiness of the film is one such characteristic. If the fllm is irl the form of a narrow strip which is folded lengthwise, sealed lengthwise, and gussetted to form a tube, uneven thickness creates difficulties. If the folded, sealed, and gussetted tube is also transversely perforated and sealed, there are further operational problems.
The reason therefor is that transversely perforated plastic film can withstand very little tensional force without being separated. Consequently, in a turret winding operation on a first bare expandable shaft which is disposed at a winding position, a transversely perforated plastic film cannot be wound with sufficient tension to form a compact and rigid finished roll. Thls difFi.culty is magnlfied when the roll of plastlc film is a cent0r-unwlndable roll having an inner diameter of at least about 7.~ cm (3 inches).
Further, when a plastic film is in the form of a transversely perforated and flattened tube for separation by a consumer into freezer bags, produce bags, and the like, the relatively loose winding of such a narrow center-unwindable roll is accentuated so that telescoping of the roll easily occurs when a sidewise force is placed thereon, such as when unloading the roll from a shaft on which it has been wound. A means for preventing such telescoping, ~28~7~5 such as minimizing the side~ise force required for unloading a roll from a shaft, is needed.
It is also difficult to transfer a moving strip or tube of such transversely perforated film from a wound roll to a new shaft upon which the strip of film or tube of film is to be wound because the lay-on roll cannot be applied to the moving strip or tube with sufficient force to bend the strip or tube into adequate contact with the new shaFt. Accordingly, a means for eFfecting such transfer, without premature breakage of the strip or roll, is additionally needed.
IJ.S. Patent No. 3,053,467 describes expansible shafts, arbors, or mandrals of the fluld pressure type on which a tubular core of rolls of paper may be supported for winding and unwinding.
This shaft has a multiplicity of radially movable and self retractable gripping buttons which are actuated by an inflatable, cylindrical air bag.
Such an expansible shaft is further described in U.S.
Patent No. 3,863,857, wherein elongate leaf members are attached to the ends of the buttons and are radially expanded by inflation of the air bladder. These expansible air shafts are primarily intended for gripping a core of a roll of paper or other web material. After winding is completed, the buttons or leaf members are retracted so that the core can be slid enrJwise ~rom the windlng shaft. If individual rolls are to be wound, such as when winding tubes of transversely perforated film to form rolls that can be separated into plastic bags by a consumer, the core may be furnished with a circumferentially attached strip of expansible adhesive tape in order to facilitate transfer of a continuously moving tube onto a new core.
U.S. Patent No. 2,779,547 describes a winding mandrel with a suction means, comprising a drum mounted for rotation about the axis of a hollow shaft and provided with a slot which is parallel to the axis of rotation of the shaft and runs substantially the length of the drum and in which is positioned a suction box connected at its center to an external vacuum pump through a rotary seal at an end of the mandrel. An aperture pad of non-porous rubber fits into the suction box and has spaced holes along the length thereof to form suction passages. In operation, a moving paper web is drawn by suction at the holes into frictional anchorage upon the pad.
U.S. Patent No. 3,552,670 describes a web-winding apparatus of the automatic or continuous type for automatically moving a new "core-carrying" mandrel into the path of the web while it is still being wound on a preceding core-carrying mandrel to complete -the winding of that roll. The web is fed in partial wrapping engagement over a bed roll to a core on one of a plurality of rotatably mounted wlnding mandrels carried in revolution by a rotatable turret past a pickup position where the free leading edge of a web formed by transverse severance of the web is transferred to a core disposed in a successive winding mandrel. A stationary vacuum chamber is formed within the interior of the bed roll and communicates through one end to a source of partial vacuum and peripherally through a plurality of holes in the shell of the bed roll. Where light, relatively impervious web materials are involved, such as sanitary tissues having transverse lines of weakness, the shell has relatively few openings through which a partial vacuum acts on the web. The bed roll has openings in the form of slots having a wirJth o~ about 0.1 cm (0.040 inch) and a very short radial distance throuyh which the vacuum must act, so that when a breakage occurs at a line of transverse perforations, the loose end of the web is caught very quickly onto the bed roll.
U.S. Patent No. 3,743,199 describes a vacuum reel spool for use on a paper machine reel when transferring a very light web to a new reel spool. The reel spool comprises a cylindrical shell having a longitudinal axis of rotation and a plurality of perforations which are formed uniformly on the surface of the shell along substantially the entire face width thereof. The interior of the reel spool is connected to a vacuum source, such as a vacuum pump.
During operation, the vacuum produced within the reel spool urges ~28Z~7~5 the ballooned portion of the web, that is formed between a previously ~Nound roll and a new reel spool, into the nip between the reel drum and the reel spool so that even especially light webs, such as tissue paper, can be reeled continuously when traveling at speeds as high as 0.17 I<m/minute (350û feet per minute).
U.S. Patent No. 4,03û,6al describes a winder for plastic film in the absence of a winding core. The winder features equalized air lubrication of the wound roll throughout its axial removal from the arbor. It is particularly directed to rolls of web having small central holes which are less susceptible to crushing.
U.S. Patent No. 4,327,877 describes a continuous winding device for webs of paper, such as toilet paper, comprising a pair of drums drivable at an equal peripheral speed, the first drum having annular seats with perforated zones for suction orifices adapted to exert a suction during the removal of a fin.ished roll and the insertion of a new core. The suction brings the material into the zone in which the tearing is to take place and inserts the material between the drum and the new inserted core.
This invention provides a process for continuously winding a transversely perforated plastic film on a first bare expandable shaft, which is disposed at a winding position, to form a center-unwindable roll that has an inner dlameter oF at leask about 7.6 cm (3 inches). The process comprises the followlny steps:
A. providing an expanded diameter for the bare expandable shaft that is at least about 6.4 mm (1/4 inch) greater than the relaxed diameter thereof, this expanded diameter being approximately equal to the inner diameter of the center-unwindable roll; and B. providing a selected minimum friction between the outer surface of the bare roll and the plastic film;
whereby the wound roll is unloadable from the shaft at the winding position without telescoping thereof.
This process further comprises:
A. providing a second bare expandable shaft, having the expanded diameter and the selected minimum friction between its outer surface and the plastic film, and disposing it at a transfer position in the vicinity of the continuously moving film, and B. providing each shaft with a row of openings which are disposed lengthwise of each shaft and are capable of being rapidly connected to a vacuum source.
Each shaft comprises a plurality oF arcuate leaves, forming the outer surface of the shaft, which are rigidly supported and radially movable to define the expanded diameter which is preferably about 12.8 mm (1/2 inch) greater than the relaxed or contracted diameter. One of the leaves is a vacuum leaf which cornprises the row of openings. Preferably, the vacuum leaf comprises a straight pipe in its middle, the openings being selectively spaced along the pipe so that they coincide with the position of a roll to be wound thereon.
More specifically, the process of this invention is directed to continuously winding, on a first bare expandable shaft which is disposed at a winding position, a plurality of transversely perforated and f:Lattened tubes of plastic film to form a plurality of center-unwindable rolls having an inner diameter of at least about 7.6 cm (3 :inches), the tubes being disposed in parallel, spaced apart, and moving continuously and at a subst~nt1ally uniform speed from a manufacturing apparatus therefor to form a plar7ar reach which extends toward the winding position, and a second bare shaft being selectively disposed at a transfer position in the vicinity of the reach. Such winding is characterized by the following problems:
(a) the tubes are easily broken at a line of perforakion by excessive tension, (b) the resultant tension during the winding is inadequate to compact the rolls tightly, and (c) the wound rolls are easily telescoped during unloading thereof from the first bare shaft.
This invention provides the following steps as an improvement to this winding process:

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A. providing an expanded diameter for each bare expandable shaft that is at least about 6.4 mm (1/4 inch) greater than its relaxed diameter, the expanded diameter being approximately equal to the inner diameter of the rolls;
a. providing a selected maximum friction coefficient between the outer surface of each bare roll and the plastic film; and C. providing a row of openings which are disposed lengthwise of each shaft and are capable of being rapidly connected to a vacuum source, whereby:
(1) the windlng at a selected tension of th~
tubes on the first shaft, while it is at the expanded diameter, forms the plurality of rolls, (2) when the rolls being wound on the first shaft are at a selected diameter, the tubes within the planar reach are brought into proximity with the second shaft, (3) while having the expanded diameter, the second shaft is rotated at a peripheral speed equal to the uniform speed, (4~ the openings in the second shaft are connected to the vacuwn source, (5) the tubes are held by the second sha~t along a nolding line which is aligned with the openings, the tubes are snapped along a line of perforation that is between the holding line and the first shaft, and the tubes are wound on the second shaft at the transfer position, and (6) the wound rolls on the first shaft are unloaded therefrom without telescoping of the wound rolls.
Preferably, the first and second shafts are cantileverly supported at one end, whereby the wound rolls are axially unloaded toward the unsupported end of the shaft in the winding poSitiGn.

'765 ~ he vacuum in the vacuum source is suitably about 67.5 kPa (20 inches ~9) and is quickly available when a vacuum reservoir is the vacuum source.
The process of this invention for continuously winding a plurality of transversely perforated and flattened tubes of plastic film to form a plurality of center-unwindable rolls having an inner diameter of at least about 7.6 cm (3 inches), the tubes being disposed in parallel, spaced apart, and moving continuously and at a substantially uniforrn speed from a manufacturing apparatus therefor to form a planar reach which extends towards the winding, may be further deflned as comprising:
A. providing at least a first expandable shaft and a second expandable shaft, each shaft having an outer surface which has:
1) an expanded diameter which is at least about 6.4 mm (1/4 inch) greater than its relaxed diameter, the expanded diameter being approximately equal to the inner diameter of the rolls, 2) a selected maximum friction coefficient toward the plastic film, and 3) a row of openings which are disposed lenrJthwLse of the shaft and are cap~ble of belng rapidly connected to a vacuum source;
B. disposing:
1) each shaft transversely to the flattened tubes, 2) the first shaft in a winding position that is farther from the manufacturing apparatus than the second shaft, and 3) the second shaft in a transfer position that is in the vicinity of the planar reach;
C. performing the winding of the tubes on the first shaft, while it is at its expanded diameter, to form the rolls at a selected tension;

~L2827~;5 ~-- 8 -D. deflecting the tubes within the planar reach toward the second shaft when the rolls being wound on the first shaft are at a selected diameter;
E. expanding the second shaft to the expanded diameter;
F. rotating the second shaft at a peripheral speed equal to the uniform speed;
G. connecting the openings in the second shaft to the vacuum source;
H. capturing the tubes along a line of capture which is aligned with the openings, snapping the tubes along a line of perforation that is between the llne of capture and the first shaFt, and continuing to wind the tubes on the second shaft;
I. endwise unloading the wound rolls from the t`irst shaft without telescoping of the wound rolls; and J. moving the second shaft and the rolls being wound thereon into the winding position of the ~irst shaft and moving the first shaft into the transfer position of the second shaft.
According to a further aspect of the present invention there :Ls provided a ba~e expandable winding shaft for winding traneversely perforated pla~tic ~ilm to form a plurality of center-unwindable rolls at a plurality of winding po~it~ons, said 3haft comprising:
A. a plurality of elongated leaves ~orming a generally cylindrical outer surface upon which said rolls are wound;
B. an intermediate tubular shaft body having apertures for radially movable button~;
C. an elongated central air bladder which is arranged axially within said shaft body, said bladder being adapted to move 6aid buttons radially for changing the ~ffective dinmeter of ~aid outer surface through B

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- 8 ~ a ) an expansion r~nge of at least about 0.64 cm. (0.25 inch) between ~n expanded diameter and a relaxed diameter, said expanded diameter being at least about 7.6 cm. (3 inches);
D. a vacuum leaf which replaces one of said movable leaves at 6aid expanded diameter and is immovably supported in fixed radial position on said tubular shaft body;
E. a plurality of roll winding locations that are spaced axially apart along said shaft, each said roll location having an axially grouped plurality of holes in said vacuum leaf for contacting said plastic film when ~aid rolls are being wound on said sha~t at naid expanded diameter:
F. a vacuum means which is:
(1) aligned with the axis of said expandable shaft, (2) capable of being rapidly connected to a high-capacity vacuum source, and (3) in fluid communication with said holes in said outer ~urface of said vaccum leaf; and G. a friction-reducing means on 6aid outer surface for imparting a selected maximum coefficient of friction between said outer ~ur~ace ~nd said pla~tic film.
A test apparatus ls descrlbed as a means for definlng the maximum acceptable coefflcient of friction for rolls of plastic film on a shaft in the winding position. Using the apparatus, marginally acceptable coefficients of friction between the shaft surface and the inside of a fully wound roll were determined to be within the range of 0.61-1.10. Fully acceptable coefficients of friction were determined to be within the range of up to 0.60.
In the drawings, Figure 1 is a diagrammatic end view of a winding apparatus for large-diameter rolls of plastic film, showing a roll being wound to its full diameter on a bare expandable shaft in the winding position.
Figure 2 is a similar view of the same apparatus and roll shown ln Figure 1 while transfer of the moving film to a roll in the transfer position is being initiated.
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Figure 3 shows the same apparatus while the new roll is being wound on the shaft at the transfer position and as the wound roll is being removed from the shaft at the winding position.
Figure 4 is a top view of the apparatus shown in Figure 3, which is winding four lines of plastic film in the form of perforated and sealed tubes, after one roll has been removed from the shaft in the winding position and as a second roll is telescoping while being removed from the shaft.
Figure 5 is a sectional view of an expandable vacuum shaft, looking in the direction of the arrows 5-5 in Figure 4.
Figure 6 is a perspective view of a test apparatus for determlning the frictional characteristics of a wlnding shaft in its contracted state with respect to a wound roll of plastic film.
As known in the art, film 10 may be wound in either direction and on a wide variety of winding apparatuses. The winding apparatus which is shown in the drawings is intended to be merely illustrative. As shown in the drawings, plastic film 10 is being wound on a bare expandable shaft 30a to form a large-diameter roll 25a which is usually relatively thin in width. Typically, plastic film 10 has been longitudinally slit to form a plurality of narrow strips which may be wound into an equal plurality of narrow rolls of film, such as tape, for specialty pùrposes. Even more typically, each of the strips is forme~ lnto a tube, yussetted, and transversely perforated and sealed, whereby a consumer can snap off one or more bags from a wound roll as desired for vegetable, freezer, or cold wrapping usages. Because telescoping is particularly bothersome for narrow rolls of film strips and tubes, it should henceforth be understood that references to film should be interpreted as meaning narrow strips of film or tubes, which may or may not be gussetted, having transversely disposed seals and lines of perforations.
Film 10 enters the winding operation as a reach 11 moving upwardly in direction 13 and over idler roll 21, then as reach 15 to a second bare expandable shaft 30b, next as reach 17 to idler roll lZ~ 7~`S

23, and finally as reach 19 to plastic roll 25a on shaft 30a.
Reaches 15 and 17 may be combined into a single reach, i.e., shaft 30b need not be in contact with tile film while it is being wound on first expandable shaft 30a.
As is well known in the art, when plastic roll 25a reaches its full size, a lay-on roll 41 moves downw~rdly in direction 43 against reach 17 to bend a lay-on reach 45 against surface 39b of shaft 30b, which is in the transfer position, and a reach 47 which extends to idler roll 23. This movement may be supported by the action of a cut-off knife (not shown in the drawings) moving into air. The fiLm in reach 45 is caught by shaft 30b along a line of capture which coincides with fixed vacuum leaf 31b. Almost simultaneously, the film is snapped across the tube or tubes of film along a line of perforation which is downstream of shaft 30b, particularly if a cut-off knife is employed.
A new roll 25b or a plurality of rolls 25b are then built up on second expandable and coreless shaft 30b while the wound roll or rolls 25a are being unloaded from first expandable shaft 30a.
Such unloading is possible without telescoping of rolls 25a because of the relatively small diameter of contracted shaft 30a, as compared to the diameter of inner surface 26a of roll 25a, and because surface 39a of coreless shaft 30a is provided with a degree of slipperiness that minimizes sticking of the plastic film to *

surface 39a. A ~Teflon~ coating on the outer surEace~ of leaves 31, 34 will provide a marginally acceptable surfacc slipperln~ss for this purpose. F'referably, this ~ra~ ' co~tin~ on the outer ~urface of leaves 31, 3~ is a "Teflon~ impregnated "Sanford Hardlube" fi m sh that is û.0051 mm (0.0002 inch) thick. However, a silicone spray provides an additional coating that further minimizes the coefficient of friction between filrn 10 and surface 39a, creating a fully acceptable winding surface on the shaft.
Telescoping of a roll 25a, such as is illustrated by telescoped roll 25a' in Figure 4, rnust be avoided if at all possible. Center unwindable rolls have a large diameter and are susceptible to telescoping when wound on a coreless shaft.
*Trademark (DuPont) for polytetrafluoroeth~lene resin **Trademark :. .

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Further, when made of a transversely perforated plastic film, such as a tube to be separated by a customer into bags, the roll cannot be built Wit~l sufficient tension to compact it firmly enough for endwise unloading from the shaft without at least a possibility of telescoping. If the coefficient of friction between film 10 and surface 39a is too great, such telescoping is difficult to avoid even though the smaller diameter of contracted shaft 30a, as compared to conventional construction, provides a relatively small area of contact and permits the operator to minimize sliding contact while removing it from shaft 30a.
Leaves 31, 34 have an acceptable winding surface which forms surface 39 of roll 30. This surface has a desired maximum coefficient of friction toward film 10 that is provided by a "Teflon"
impregnated ~San~ord ~rdlube" finish whi(h ls o.ao51 mm (Q.QQ~2 inch) thick and is preferably aided by periodic spraying wlth a silicone lubricant.
As is known in the art, a layer of outwardly moving air can also be employed to reduce friction when axially unloading wound rolls 25a from shaft 30a. However, this procedure is not ideal for handling narrow, spaced-apart rolls 25a, as illustrated in Figure 4. Providing leaves 31, 34 with a grooved surface, thereby reducing the area of possible frictional contact between surfaces 26a, 39a, is consequently preferred over the moving air method as an alternate means for reducing friction when unloatding wound rolls 25a.
Vacuum leaf 31 comprises a central tube or pipe 32, having a plurality of holes 33 which are spaced along pipe 32 according to the width and spacing apart of the plastic rolls 25 to be wound on a shaft 30. When plastic rolls having a different width are to be wound, each shaft 30a, 30b is preferably replaced by another pair of shafts, each comprising a vacuum leaf 31 having a different spacing of holes ~3.
The relaxed state of air bladder 35, as seen in figure 5, allows movable leaves 34 to retract onto shaft body 37 as the compression springs, surrounding the buttons attached to each *Trademark : **l~ademark .X~

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movable leaf 34, urge the pressure flanges to remain in contact with air bladder 35 whlch is made of tear-resistant neoprene with bonded ends. Relaxation of air bladder 35 allows a full 0.64 cm (1/4 inch) (preferably up to 1.3 cm (about 1/2 inch)) of diameter to be available between surfaces 39a and 26a for removing the wound rolls ~5a of film without telescoping thereof.
When leaves 34 are fully expanded to the radius of fixed vacuum leaf 31, as when a roll 3ûb is at the transfer position, as seen in Figure 2, holes 33 provide a suction force which grabs lay-on reach 45 of each tube of plastic film 10 and holds it firmly for wrapping about surface 39b of the roll. Because pipe 32 is small in diameter and at least about 67.5 kPa (20 inches Hg) of vacuum is quickly available frorn a reservoir thereof, the vacuum is very quickly applied and concentrated at holes 33b.
However, vacuum can be provided for shaft 30 by other devices, such as a fixed hollow arcuate leaf of approximately trapezoidal shape, having selectively spaced openings therein. A
plurality of side-by-side tubes, having a diameter equal to the distance from the surface of shaft body 37 to the expanded surface of a shaft 30, can also be attached to each other and to shaft body 37 to simulate a vacuum leaf 31, one or more of the tubes being perforated and connected to a vacuum source.
Bare expandable shafts 30a, 30b are exactly the same in design and are shown ln section in Fi~ure 5 as shaft 30 having a single fixed vacuum leaf 31, a plurality of movable leaves 34, a button assembly 36 for each of the movable leaves 34, an intermediate tubular shaft body 37 having apertures therein, columns 38 which rigidly support vacuum leaf 31 and are attached to shaft body 37, and an elongated central air bladder 35 which is disposed axially within shaft body 37. Each button assembly 36 comprises an elongated pressure flange which has the same curvature as the expanded bladder, a row of buttons or studs which slide within the apertures in shaFt body 37 and are rigidly attached to the flange and to a leaf 34, and a compression spring which surrounds each of ~827~

the buttons. Shaf`t 30, except for vacuum leaf 31, is commercially available from Nim-Cor Inc., 575 Amherst Street, Box K, Nashua, New Hampshire 03061.
A frictional test apparatus 5û is shown in Figure 6. This apparatus is suitable for determining the frictional forces generated by removing a wound roll 25a from a shaft 30a in the inding position. Apparatus 50 comprises a plywood stripper plate 51 having a central hole therein, a pair of eye screws 52 which are attached to one side of plate 51 and on opposite sides of the central hole, a pair of cables 53 which are attached to eye screws 52, a pair of eye screws 54 which are attached to cables 53, an equalizing harness 55 to which eye screws 54 are attached on one side thereof, an eye screw 56 which is attached to the center of the other side of harness 55, a hook 57 which is connected to the eye of eye screw 56, and a strain gage 58 which is attached to hook 57.
To conduct frictional tests with assembled apparatus 50, stripper plate 51 is inserted over the end of a cantilevered shaft 30a, and a fully wound roll 25a of plastic film is next inserted onto shaft 30a and pressed snugly against plate 51. Harness 55 is held so that cables 53 are substantially parallel to surface 39a, and pull 59 is exerted with sufficient force to provide a firm, smooth motion at about 2.54 cm/second (one inch per second). The peak break away or static load and the sliding (dynamic) load are recorded. The dynamic load is divlded by the weight of the tested roll 25a, both being in the same weight units, to produce a dimensionless coefflcient of frictlon.
Tests for winding surface acceptabillty were made in this manner by using apparatus 50 on identical bare aluminum shafts 30a having an outside diameter of 15.2 crn (six inches) and the three following surface conditions for surface 39a:
1) no surface treatment;
2) a "Teflon" impre~nated "Sanford l-~rdlube" finlsh; and 3) a silicone spray coating on the ~Sanford Hardlube" finish.

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A fully wound roll 25a of l,ûO0 plastic bags, weighing 2.6 kg (5.85 pounds), (specification weight), having an outside diameter of 25.4 cm (10 inches), and made of plastic film containina ahout 2,000 ppm of a erucim~de slip agent, was used for each test.
Static load values were difficult to read but did not differ greatly from dynamic load values. The two load values were consequently assumed to be essentially the same, and only dynamic load values were recorded while maintaining a steady pull of about 2.54 cm per second (one inch per second) for these three conditions. The position of vacuum leaf 31 was determined to be immaterial. The value for each condition was the average of five tests, 95% confidence limits being about 0.23 kg (0.5 lb). The coefficient of friction was then calculated as the ratio of the pulling force to the weight of the load, i.e., roll 25a.
The load value, the acceptability, and the coefficient of friction for each condition were as follows:
Load value, kg (lbs) Acceptability Coefficient of Friction 1) 4.3 (9.5) not acceptable ].. 62 2) 2.8 (6.25) marginally acceptable 1.07 3) 1.6 (3.5) fully acceptable 0.60 Generally, the frictional coefficient range for marginal acceptability was 0.61-1.10, and the range for full acceptability was 0-0.60.
While the foregoing embodiments are pre~erred, it ls -to be understood that numerous modifications and variatlons may be made therein by those skilled in the art, and it is intended to cover in the appended claims all such modifications and variations as fall within the principles and scope of the invention.

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Claims (31)

1. A process for axially unloading a center-unwindable roll of transversely perforated plastic film from a first bare expandable shaft without telescoping of said roll while manually applying a sidewise force thereto for unloading of said roll from said shaft, said roll having an inner diameter of at least about 7.6 cm. (3 inches) and said shaft being disposed at a winding position, said process comprising the following steps:
A. providing an expanded diameter for said bare expan-dable shaft that is at least about 0.64 cm. (1/4 inch) greater than the relaxed diameter thereof, said expanded diameter being approximately equal to said inner diameter of said roll;
B. providing said shaft with a plurality of rigidly supported arcuate leaves having an outer surface, one said leaf being a vacuum leaf which is fixed at said expanded diameter and the remainder of said leaves being radially movable to define said expanded diameter and said relaxed diameter;
C. providing a selected coefficient of friction between said outer surface of said bare shaft and said plastic film, that is within the range of 0-1.10, whereby said force required for said unloading is minimized; and D. cantileverly supporting said shaft at one end, whereby said wound roll is axially unloadable from said shaft by said operator toward the unsupported end of the shaft at said winding position without telescoping thereof.

2. The process of claim 1, which comprises providing said coefficient of friction within the range of 0-0.60.

3. In a process for continuously winding, on a first bare expandable shaft which is disposed at a winding position, a plurality of transversely perforated and flattened tubes of plastic film to form a plurality of center-unwindable rolls having an inner diameter of at least about 7.6 cm. (3 inches) said tubes being disposed in parallel, spaced apart and moving continuously at a substantially uniform speed from a manufactur-ing apparatus therefor to form a planar reach which extends toward said winding position, a second said bare shaft being selectively disposed at a transfer position in the vicinity of said reach, wherein:
(a) said tubes are easily broken at a line of perforation by excessive tension, (b) said resultant tension during said winding is inadequate to compact said rolls tightly, and (c) said rolls are easily telescoped during unloading thereof from said first bare shaft, the improvement that:
(1) minimizes the exertion of tensional force upon said moving tubes of film, (2) exerts a strong gripping force upon the inner surfaces of said center-unwindable rolls during the winding thereof, and (3) minimizes the force that is required to unload said center-unwindable rolls from said first bare expandable shaft, said improvement comprising the following steps:
A. providing an expanded diameter for each said bare expandable shaft that is at least about 0.64 cm. (? inch) greater than its relaxed diameter, said expanded diameter being approximately equal to said inner diameter of said rolls;
B. providing a selected maximum coefficient of friction which is no more than 1.10, between the outer surface of each said bare roll and said plastic film; and C. providing a row of openings which are disposed lengthwise of each said shaft and are capable of being rapidly connected to a vacuum source, whereby:
(1) said winding at a selected tension of said tubes on said first shaft, while it is at said expanded diameter, forms said plurality of rolls, (2) said tubes within said planar reach and said second shaft are brought into proximity when said rolls being wound on said first shaft are at a selected diameter, (3) while having said expanded diameter, said-second shaft is rotated at a peripheral speed equal to said uniform speed, (4) said openings in said second shaft are connected to said vacuum source, (5) said tubes are held by said second shaft along a holding line which is aligned with said openings, said tubes are snapped along a line of perforation that is between said holding line and said first shaft, and said tubes are wound on said second shaft at said transfer position, and (6) the wound rolls on said first shaft are axially unloadable therefrom without telescoping of said wound rolls.

4. The process of claim 3, which comprises providing said first and second shafts with cantilever support at one end, whereby said wound rolls are axially unloadable toward the unsupported end of the shaft in said winding position.

5. The process of claim 3 which comprises providing a coefficient of friction equalling 1.10 as said maximum co-efficient of friction.

6. The process of claim 5 which comprises providing a coefficient of friction of 0.60 as said maximum coefficient of friction.

7. The process of claim 5 which comprises providing a vacuum of at least about 67.5 KPa (20 inches Hg) as the vacuum in said source.

8. The process of claim 7 which comprises providing a vacuum reservoir as said vacuum source, whereby said vacuum is quickly available.

9. The process of claim 5 which comprises providing each said shaft with a plurality of arcuate leaves which are rigidly supported and radially movable to define said expanded diameter.

10. The process of claim 7 which comprises providing one of said leaves as a vacuum leaf which comprises said row of openings.

11. The process of claim 8 which comprises providing a straight pipe as said vacuum leaf, said row of openings being spaced along said pipe.

12. The process of claim 11 which comprises rigidly supporting said vacuum leaf at said expanded diameter.

13. The process of claim 12 which comprises providing said straight pipe with selective spacing apart of said openings in accordance with the width and space apart of said tubes.

14. A process for continuously winding a plurality of transversely perforated and flattened tubes of plastic film to form a plurality of center-unwindable rolls having an inner diameter of at least about 7.6 cm. (3 inches) said tubes being disposed in parallel, spaced apart, and moving continuously and at a substantially uniform speed from a manufacturing apparatus therefor to form a planar reach which extends toward said winding, said process comprising:
A. providing at least a first expandable shaft and a second expandable shaft, each said shaft having an outer surface which has:
(1) an expanded diameter that is at least about 0.64 cm. (1/4 inch) greater than its relaxed diameter, said expanded diameter being approximately equal to said inner diameter of said rolls, (2) a selected maximum friction coefficient toward said plastic film of no more than about 1.10, and (3) a row of openings which are disposed lengthwise of said shaft and are capable of being rapidly connected to a source of quickly available vacuum;
B. disposing:
(1) each of said shafts transversely to said flattened tubes, (2) said first shaft in a winding position that is farther from said manufacturing apparatus than said second shaft, and (3) said second shaft in a transfer position that is in the vicinity of said planar reach;
C. performing said winding of said tubes on said first shaft, while it is at said expanded diameter, to form said rolls at a selected tension that does not break said transversely per-forated and flattened tubes;
D. deflecting said tubes within said planar reach toward said second shaft when said rolls being wound on said first shaft are at a selected diameter;
E. expanding said second shaft to said expanded diameter;
F. rotating said second shaft at a peripheral speed equal to said uniform speed;
G. connecting said openings in said second shaft to said vacuum source;
H. capturing said tubes along a line of capture which is aligned with said openings, snapping said tubes along a line of perforation that is between said line of capture and said first shaft, and continuing to wind said tubes on said second shaft, whereby transfer of said tubes to said second shaft is effected without premature breakage of said tubes;
I. endwise unloading the wound rolls from said first shaft without telescoping of said wound rolls as the result of providing said expanded diameter and said maximum friction coefficient that minimize the force that is required to unload said center-unwindable rolls from said first bare expandable shaft; and J. moving said second shaft and said rolls being wound thereon into said winding position of said first shaft and moving said first shaft into said transfer position of said second shaft.

15. The process of claim 14 which comprises cantileverly supporting said first and second shafts at one end, whereby said wound rolls are unloaded toward the unsupported end of the shaft in said winding position.

16. The process of claim 14 which comprises providing at least about 67.5 KPa (20 inches Hg) as the vacuum in said vacuum source.

17. The process of claim 16 which comprises providing a vacuum reservoir as said vacuum source, so that said vacuum is quickly available.

18. The process of claim 14 which comprise providing for each said shaft a plurality of arcuate leaves which are rigidly supported and radially movable to define said expanded diameter.

19. The process of claim 18 which comprises providing one of said leaves as a vacuum leaf which comprises said row of openings.

20. The process of claim 19 which comprises providing said vacuum leaf as a straight pipe in the middle thereof, said row of opening being spaced along said pipe.

21. The process of claim 19, which comprises rigidly supporting said vacuum leaf at said expanded diameter.

22. The process of claim 14 which comprises selectively spacing said openings laterally in accordance with dimensions and spacing apart of said perforated tubes which are gussetted and separable into bags.

23. A bare expandable winding shaft for winding transversely perforated plastic film to form a plurality of center-unwindable rolls at a plurality of winding positions, said shaft comprising:
A. a plurality of elongated leaves forming a generally cylindrical outer surface upon which said rolls are wound;
B. an intermediate tubular shaft body having apertures for radially movable buttons;
C. an elongated central air bladder which is arranged axially within said shaft body, said bladder being adapted to move said buttons radially for changing the effective diameter of said outer surface through an expansion range of at least about 0.64 cm. (0.25 inch) between an expanded diameter and a relaxed diameter, said expanded diameter being at least about 7.6 cm. (3 inches);
D. a vacuum leaf which replaces one of said movable leaves at said expanded diameter and is immovable supported in fixed radial position on said tubular shaft body, E. a plurality of roll winding locations that are spaced axially apart along said shaft, each said roll location having an axially grouped plurality of holes in said vacuum leaf for contacting said plastic film when said rolls are being wound on said shaft at said expanded diameter:
F. a vacuum means which is:
(1) aligned with the axis of said expandable shaft, (2) capable of being rapidly connected to a high-capacity vacuum source, and (3) in fluid communication with said holes in said outer surface of said vaccum leaf; and G. a friction-reducing means on said outer surface for imparting a selected maximum coefficient of friction between said outer surface and said plastic film.

24. The winding shaft of claim 23, wherein said vacuum source contains a vacuum of at least about 67.5 KPa (20 inches Hg).

25. The winding shaft of claim 23, wherein said coefficient of friction is Up to about 1.10.

26. The winding shaft of claim 25 wherein said coefficient of friction is up to about 0.60.

27. The winding shaft of claim 26, wherein said friction-reducing means is a "Teflon"TM coating on said outer surface and a silicone spray coating over said "Teflon"TM coating.

28. The winding shaft of claim 27, wherein said "Teflon"TM
coating is a "Teflon"TM impregnated "Sanford Hardlube"TM finish that is about 0.0005 cm. (0.0002 inch) thick.

29. The winding shaft of claim 25, wherein said friction-reducing means is a "Teflon"TM coating on said surfaces of said fixed vacuum leaf and said plurality of movable leaves.

30. The winding shaft of claim 28, wherein said Teflon coating is a "Teflon"TM impregnated "Sanford Hardlube"TM finish that is about 0.0005 cm. (0.0002 inch) thick.

31. The winding shaft of claim 29 wherein said buttons move said radially movable leaf members through a distance of at least about 1.28 cm. (1/2 inch).