US2490781A - Method and apparatus for preparing and utilizing sheet material for packaging purposes - Google Patents

Description

Decn 13, 1949 w. s. CLOUD 2,490,781

METHOD AND APPARATUS FOR PREPARING AND UTILIZING SHEET MATERIAL FOR PACKAGING PURPOSES Filed Aug. 22,"- 1946 4 She'ets-Sheet l DeC- 13 1949 w. s. cLouD 2,490,781

METHOD AND APPARATUS FOR PREPARING AND UTILIZING SHEET MATERIAL FOR PACKAGING PURPOSES Flled Aug. 22, 1946 4 Sheets-Sheet 2 Dec. 13, 1949 w. s. cLouD 2,490,731

METHOD AND APPARATUS FOR PREPARING AND UTILIZING SHEET MATERIAL FOR PACKAGING PURPOSES 4 Sheets-Sheet 3 Filed Aug. 22, 1946 Dec. 13, 1949 w. s. cLoUD 2,490,781

METHOD AND APPARATUS FOR PREEARING AND UTILIZING SHEET MATERIAL FOR PACKAGING PURPOSES Filed Aug. 22, 1946 4 Sheets-Sheet 4 www Patented Dec. 13, 1949 METHOD AND APPARATUS FOR PREPARING AND UTILIZING SHEET MATERIAL FORj PACKAGING PURPOSES Willian@ s. cloud, wnmette, n1. c Application August 22, 1946, Serial No. 692,323

si claims. (ci. "1a-21) This invention relates to a new and improved method and apparatus for `preparing and utilizing sheetmaterial for packaging purposes.

There has developed in industry a rather widespread demand for packaging in which the packaging material conforms closely to the shapeand size of the various commodities with which yit is used and at the same time oifers a protective covering therefor. An example of a -material that can lbe made to conform is the rubber hydrochloride product sold 'by the Goodyear Tire & Rubber Company, Inc., of Akron, Ohio, under the trade name, lElixfilxrL` Although my invention is described herein as relating to the use of Pliollm, it should be understood, that this is illustrative only and the principles of my method can be applied to any sheet material which or can be made plastic or stretchableand which can be suitably sealed.

lSeveral methods and machines have already been proposed to wrap articles inmaterial such as `Pliofilm. Some methods involve little more than hand-wrapping procedure.-v Others involve the use of a, metal. frame for Asuspending the plastic sheet of P'liofilm in horizontal position, forcing the commodity against'the sheet to form a pocket therein, then twisting thearticle and lby the reaction of hydrochloric acid with rubber.

It possesses peculiar characteristics-which are not entirely explainable but which can be useful, and aresometimes troublesome.

For example, it ybecomes plastic when heated. and, while in this condition, it can be stretched easily toa considerable degree. `However',aft =:r the film has been stretched and then .cooled in the stretched condition, it may berelatively tough and tensilized and may reveal a strong tendency to shrink on being reheated. In this condition, it is rather diilicult to -handle if it is desired to reheat the iilm Vand again make it plastic. ,c l

,Y Generally speaking, Pliolm is manufactured and sold today in sheets of various thicknesses, one of the most commonlyf used beingknown as 100 gauge, it `being 1/1uo,ooo of` an inch thick.

Using known manufacturing processes, there is a practical limit to the thinness to which the sheets can bemade. .When athinner Asheet is desired, it has been necessary to heat and soften the original film, for example, 100 gauge, stretch it, coolit, and rewindit. This adds tothe expense .of manufacture and the resulting product is more diicult tohandle and use in ffstretchthe film by hand to sealthe pocket, after which the excess lmv is cut off by a knife or yother cutting means.v v l Another method of wrapping articles in material such as Pliolm vhas been disclosedand claimed in my patent, Number 2,403,482, issued July 9, 1946, wherein the film is suspended over openings, and tubes are forced against the film, creating pockets therein into which the articles to be enclosedare deposited.

In most vof these methods, there is a certain amount of stretching :of the` sheet material.

Y However. nonev ofthese methods is full adcording to the use intended.

It is rather generally known that v Pliofilm is a substantially moisture-proof, transparent sheet materialchemically known as rubber hydrochlol I ride. It is a complex organic compound obtained wrapping than was the originalfilm. y One o f the objects of my invention is to provide method and apparatus which, preliminary to forming the wrapping pockets, canaccom- .plishboth a lateral and a longitudinal progressive stretch of material in one continuous operation and while being held by the same gripping means throughout the stretching operation'.`

Another` object of myinvention lis to provide method and apparatus for the formation of pockets in the softened and prestretched sheet material andfor, the ,use of such pockets for the reception of articles'tobewrapped.k Another object of my invention is to provide methodand apparatus for the simultaneous use of .two sheets of material,I softened. and pres'tretchedas above indicated, in such away V,that thepockets in kone sheet are placed in'confronting relation with the pocketsof the other sheet so as to form complete closures about y,the articles to.` be, wrapped. A further object o fmy invention is to make available to industrya method,l ofstretching; in two directions a plastic sheet material. such` as Pliofilm, toa predetermined thinneSs.; The conf trol of thestretching. operationisof vvital importance inl certain industries, and i many in'- stances it must be 'closely regulated;r Y A. As as example, I call attention to the 'experimental work of Dr. A. L. Stahl of the University of Florida Experimental station, described in vol. 4 of No. 4 of the pamphlet Citrus published in October 1941, by Florida Citrus Exchange of Tampa. Florida. It is there pointed out that in wrapping articles, such as oranges, with Pliofllm, it is essential that the film be thick enough to protect the article against loss of moisture and thin enough to permit the orange to breathe, carbon dioxide passing through thePlioiilm.

It has been foundthat film of a thickness of about ZO-gauge, or *il/momo of an inch, is most satisfactory for this purpose. My invention where the sheet material is heated, rendered soft and more plastic before it is stretched.

The temperature of drums 3 can be regulated and controlled in a conventional manner so as to heat the sheet material uniformly and maintain uniform plasticity. The heating medium in drums 3 may be steam or hot oil or any other suitable heating agent. As shown in Fig. 9, I prefer Y to imbed electrical heating elements 4i, of the type enclosed in metal tubing, in the drum, being disposed in a helical groove. The drums 3 are preferably at least as wide as the sheet material makes possible the two-way stretching of sheet material of considerable thickness, such as ml/wcm of an inch, to a. predetermined average lesser thickness, such as 2li-gauge, or to so stretch the fiimthat the thickness of the finished wrappers will average about 20 gauge. Furthermore.'

articles are wrapped very emciently and economically, thus avoiding the tedious labor of wrapping in paper by hand, as has been common heretofore.

Other objects and advantages of my invention will appear hereinafter.

This application is in part a continuation of my copending applications Serial No. 436,666, filed March 28, 1942, now abandoned, and Ser. No. 539,971, filed June 12, 1944. The wrapper disclosed herein is claimed in my application Serial No. 532,563, filed April 24, 1944, now abandoned.

In order to illustrate diagrammatically the respective steps of my invention, I have provided the accompanying drawings, all of which are more or less diagrammatic and in which:

Figure 1 is a diagrammatic view of an apparatus for practicing my invention, shown in side elevation and partly in vertical section, some details being omitted for clarity;

Fig. 2 is a top view of the apparatus;

Fig. 3 is a sectional view of a'detail on line 3-3 of Fig. l;

Fig. 4 is a sectional view of a detail taken approximately on line 4-4 o! Fig. 1, some parts being omitted for clarity;

Fig. 4A shows a modified form of clamp;

Fig. 5 is a top view of a part of the apparatus illustrating a film-guide roller, its supports andmotivating means;

Fig. L6 is a side elevation of a detail illustrating the picking up of the film by the fingers;

Fig. 7 is a side elevation of a detail illustrating the releasing of the excess or scrap film by thc fingers;

Fig. 8 is a sectional view of a detail taken on line 8-8 of Fig. l;

Fig. 9 is a fragmentary sectional view of a heating drum;

Fig. 10 is a detail section of an insulating ring and heating wire as located around the periphery of each recess of the chain-carried cut-off mechanism;

Fig. ll is an elevation of a spherical object, such as an orange, wrapped and sealed in sheet material which has been stretched according to my method; and

Fig. l2 is a diagrammatic view of an alternative apparatus for practicing my invention, shown in side elevation and partly in vertical section.

In order to illustrate how my method of preparing sheet material is applicable to a packaging operation, attention is directed to Fig. l wherein webs of sheet material 23, such as Pliofilm, are fed or unwound from rolls 22, around idler rolls 24, thence around heating drums 3 to heat its full width.

As the heated sheet material is tacky, it is advisable either to use drums 3 with polished metal surfaces such as polished chrome plating or chrome steel or some similar substance, or to cover them or the backs of the films with some substance, such as wax, soap, or paper, which will reduce the tendency for the sheet to stick to the heated drums in case of stopping the machine. As shown in Fig. 9, I prefer to cover the drums 3 and the faces surrounding cups 50, best shown in Fig. 8, with a cotton cloth or spun glass sheet 42.

- The spun glass or other heat withstanding exible material is essential on drum 2 because of cooperation with hot cut-olf wires. Guide rolls 43 may also be covered but need not be. according to present experience.

Drums 3 and rolls 24 ordinarily are driven in timed relationship with sprocket chains 8 from any suitable source of power (not shown). The timed relationship is preferably adjusted by a variable speed drive capable of minute change, such as a Reeves drive.

From heating drums 3, the webs of sheet material 23 are passed around guide rolls 43, and thence around parallel filling and sealing drums I and 2, which face each other at a portion of their peripheries and travel in counterclockwise and clockwise directions respectively. Portions of the opposing surfaces of drums I and 2 are in engaged or contacting relation to each other.

Sprockets 4 and 1 are mounted on shafts 5 and 6, respectively, and connected by means of chains 3. The two drums I and 2 are connected by gears or a chain and sprockets. Thus, drums I and 2 may be driven from any suitable source of power (not shown) applied to any of these shafts. In passing from sprockets 4 to sprockets l, chains 8 are supported by angle-irons I6 to prevent sag.

Webs 23 are stretched laterally by a series of stretch arms Ill (Fig. 4) pivotally mounted on bracketed side plates II of alternate or spaced links of each chain l. Each arm carries a spring-pressed clamp or jaw I3 pivotally mounted on pin I4. The spring I 5 may be either the form shown in Fig. 4 or that shown in Fig. 4A, the latter having given better service, In Fig. 4A the jaw I3 is fast on shaft I4. The arms and clamps are adapted to be actuated by stationary cams as described below.

As sprocket chains 8 approach sprockets 4, arms III are progressively forced inward and upward from a vertical to a horizontal position by stationary guide cams 2n. As the arms approach the top of the sprockets in a substantially horizontal position, they come to rest upon pulleys or drums 44 mounted on shafts 5 which support them in a horizontal position. Meanwhile, the pins 25 are engaged by stationary cams 2i which progressively force lthem in a direction to open clamps I3.

As webs 23 pass around idlers 43, they pass just above the tip ends of arms III which are posianonym 4diately thereafter, clamp jaws I3 pass beyond cams 2I and, under the influence of springs I5 (Fig. 4), clamp the webs 23 against the tips of arms I0 and a tight grip is obtained on both sides of webs 23. This grip is maintained during the lateral and longitudinal stretching and the sealing operations, and until released as described below.

As webs 23, held by clamps I3, pass beyond sprockets l, the later pull or stretch is begun. This is accomplished by means of stationary guide cams I1 (Figs. 1, 4, and 6) which contact arms I0 and progressively force them outward and upward from horizontal to substantially vertical positions, said arms I0 pivoting on pins I2.

Arms I ll are carried in substantially vertical positions around drums I and 2 and until they are forced to a horizontal position, as explained above, by stationary cams 20, said arms being prevented from going inward toward a horizontal position by stationary guide cams Il and l1, the latter (Fig. 3) being mounted on manifolds 48, and being prevented by stationary cams (Figs. l and 3) from falling outwardly if the web tears.

As arms Ill are raised, the web-holding tips of those mounted on opposing sprocket chains 3 move away from each other, thus pulling or stretching webs 23 laterally (Fig. 2). The degree to which webs 23 are stretched laterally may be controlled in at least four ways: by varying the length of arms I 0, by varying the extent to which the relative positions of oppositely-disposed arms I0 are changed by guide tracks I1, by causing opposing sprocket chains 8 to diverge at various degrees thus varying the distance between them, and by varying the original width of webs 23.

Upon completion of the lateral stretch of webs 23, said webs arrive at the top of drums I and 2. As they are carried from this position around drums I and 2, the distance between the webholding tips of arms I0, in each of the rows carried on chains 8, is increased longitudinally, thereby stretching webs 23 lengthwise (Fig. l). The percentage to which webs 23 are stretched longitudinally in this manner may be controlled by varying the ratio of the diameter of sprocket wheels 1 to the length of arms I0.

As the heated webs 23 are soft and plastic, the middle portion thereof tends to sag and may contact the drums I and 2 prematurely. This tendency may be eliminated by supporting and controlling the middle portion of each web. As illustrated in Figs. 1 and 5, I prefer to do this by a roller formed of a hose rotatable on a rigid, curved core-rod and driven through a belt I6 by the associated shaft 5. The core-rod extends back and down to a point where it can have access to the frame, by which it is carried.

As best shown in Fig. 3, holes 28 have been formed in sprockets 1. Hollow tubes or castings forming manifolds 48 are mounted on the inside of said sprockets so that the two openings cooperate. At predetermined intervals, cups are mounted over openings in the tops of the said manifolds. As articles to be wrapped by my method can be no larger than the inside dimensions of these cups, I prefer to have these cups easily removable and exchangeable. As best illustrated in Fig. 8, my preferred method of mounting these cups is to have a recess in the necks of these cups, on the shoulders of which sit the heads of hollow screws 5| which are screwed into the manifolds 43, thus forming vacuum conduits 21 extending from the cups it through the hollow screws II. the manifolds Il. and the holes 28 in sprockets 1. l

In sliding contact with sprockets 1 are stationary vacuum chambers Il (Figs. 1 and 3) which are connected with a conventional vacuum pump 52 by tubes 53. A conventional relief valve 5| together with proper regulation of vacuum pump 32 ensures a vacuum of any desired amount.

Thus, the outer surfaces of drums I and 2 are composed of the extended and contacting lips or rims of cups 50 and of the cups themselves which form hemispherical recesses 26, positioned in predetermined locations so that the recesses of drum I cooperate with oppositely-situated recesses of drum 2 when brought in opposed relation thereto to form substantially spherical chambers.

As drums I and 2 rotate, vacuum conduits 21 intermittently register with stationary vacuum chambers 49, at which time the vacuum is applied. This is clear from Fig. l. It should be noted that the application of vacuum occurs after the longitudinal stretch of webs 23 has been completed. The vacuum draws portions of webs 23 into recesses 26 so as to line the concave surfaces of cups 50, or it may draw the portions any lesser amount desired.

At this time, articles to be wrapped, as for example oranges, represented by number 33 (Fig. 1), are fed into a position between opposing hemi spherical recesses 26. This may be done by hand or by any conventional feeder. I prefer to use a separate feeder unit for each longitudinal row of recesses 26. These units are comprised of troughs 55, positioned at a slight angle so that as the articles at their lower extremities fall therefrom, the next articles are automatically positioned by gravity, wheels 58 containing in their outer surfaces hemispherical recesses 51 positioned in predetermined locations, and circular guards 53. The wheels 56 are all mounted fast on shaft 59, which is driven in timed relation to shaft 6 by any convenient means (not shown). I prefer to do this through a chain carried by sprockets mounted on shaft 59 and one of the shafts 6. If this method is used, any variations not compensated for automatically may be met by adjusting one sprocket or its shaft.

The feed may be made more gentle* and more versatile in feeding different orange sizes accurately without adjustment by providing a narrow shelf close to the drums I and 2 onto which the oranges drop. The shelf is preferably padded and formed of two vanes sloping downwardly toward each other which are opened downwardly quickly by cam action to release the oranges. This is to be the subject matter of a separate application.

Articles 38 to be wrapped fall onto wheels Il. The overhang of circular guards 58 allow the articles to fail only into recesses 5l. 'I'he movement of wheels 53 drops the articles within circular guards 68 so that they fall into a position between opposing hemispherical recesses 28. As oppositely-disposed recesses 26 face each other, they form substantially spherical chambers in which articles 3l are placed. The peripheral margins of recesses 2| at this time contact each other under pressure. To ensure a proper contact, I prefer to cover one of these drums rwith a sponge rubber sheet l0 (Fig. 8) or other'cushion. The amount of pressure depends upon the relative positions of drums I and 2 to each other, one of the drums preferably being adjustable. The left-hand drum of l'ig. l 'is the one chosen for auflei -application of the cushion so that the same cushion may cooperate with the: cut-oir units 23.

Since these portions of webs 23 are in plastic and tacky condition when the drums are brought into contact, the opposing portions of webs 23 which are brought together under pressure are sealed. One of the common characteristics of sheet material such as Plioillm is that a seal of two sheets of such material can be accomplished by bringing the same into contacting relation in heated plastic condition under pressure.

Immediately after the sealing operation, the web 23, which passes around drum I, is released from clamps I3. This is done by the action on pins of a stationary cam (not illustrated), the action being identical to that of cam I3, as illustrated in Fig. 7.

At approximately the same time, the vacuum in conduits 21 in drum I is released while the vacuum in conduits 21 in drum 2 is maintained. In this way, the wrapped articles 3! (Figs. l and l1) are carried around drum 2, between the two webs 23, to anydesired position where they may be separated from the excess or unused portion of the webs 30.

This separation of the wrapped articles 38 from the excess or unused portion of webs may be performed in any suitable manner. However, this excess portion is still plastic and in a stretched condition and, as indicated above, material such as Plioillm. upon being released in this condi-- tion, will tend to shrink. Thus, certain dimculties are encountered if the wrapped articles are cut out in a conventional manner. An apparatus for overcoming these diiiiculties is described in my copending applications, Serial No. 536,014, med May 17, 1944, and Serial No. 76,808, tiled February 16, 1949, wherein all features of the invention relating to the cut-oil itself are claimed. f The apparatus of said application which I prefer to use in separating the wrapped articles from the unused portion of the webs and which is diagrammatically illustrated in Fig. l includes a series of severing and holding cups 2S, carried upon transverse supports 3B and corresponding in number to and aligned to cooperate with the cups l0 in the transverse rows of packaging drum 2. 'Ihe opposite ends of each transverse support are mounted in any conventional manner upon oppositely-disposed links of endless chains 3l, traveling over sprocket wheels 32 and 33 which are carried on shafts 3i and 31. which are driven in timed relation with shaft t in any conventional lil held, all around the article, and the following portion held so it will not snap back, the electrical resistance wires 34 are activated in any conventional manner (not shown). The heated wires sever the sheet material. the wrapped articles falling by their own weight into cups 29 which carry them to hopper or conveyor belt 35, depositing them therein as the cups pass around sprocket 32.

The unused, perforated portions of the laminated webs 23 are released from clamps I3 by the action of guide cam I8 on pins 25, as best shown in Fig. 7. This unused portion is then rewound on roll to be sold as scrap. This unused portion is preferably rendered as small as possible (or perhaps eliminated) by the placement of electrical resistance wires 3l. Thus the wires 34 may form squares, or other shapes in which a wire 34 partly around one cup 28 extends approximately to wires on adjacent cups, leaving no scrap between articles.

An oven 68 may be provided for the separated oranges to pass through if desired. This seems to ensure that the film will be satisfactorily shrunk around the article and to relieve any strains which might leave a tendency for subsequent tearing. The heat permits any entrapped air to escape, as would prlcking with a needle. The needle may be heated to cause resealing, but a tiny hole in a skin tight nlm is sometimes not very objectionable.

An alternative form of my invention is illustrated in Fig. 12. Here, instead of having two filling and sealing drums I and 2 (Fig. l), I use only one such drum 6I (Fig. 12) which Is identical in all respects to drum 2. I replace drum I with a continuation or extension of that part of the apparatus described above which was used for separating the wrapped articles from the unused portion of the webs. This continuation or extension is created by lengthening chains 3l and passing them around a higher sprocket I2.

The operation of this alternative apparatus is similar to that of the apparatus rst above described, it being identical as to drum 6I. As before, the web 23 is passed over a horizontal heating drum (not shown). Thence it passes over severing and holding cups 23. As the articles 3l to be wrapped drop into the semispherical recesses manner so that cups and cups 29 move together.

The holding and severing cups 29 are preferably made of refractory or other heat and electrical insulating material and of a diameter suillcient to receive the packaged article 39. The top of the side walls or rim of each cup 23 is curved to conform to the curved surface of the packaging cups 50 and mounts an electrical resistance wire 34, which either by itself or in cooperation with similar wires mounted on adjoining cups 23 substantially surrounds the rim of the cup.

As the wrapped articles 39 are brought to the bottom oi' drum 2, they are still held together by the stretched, unrecessed portion of webs 23. This excess web is ilrmly gripped between the rims or lips of packaging cupsv SII and those of holding and severing cups 29, the packaged articles 39 being contained in the substantially spherical chambers formed by the joinder of these cups. As these cups move, and while the excess nlm surrounding the packaged articles is nrmly caused by the vacuums pulling the web passing over drum 6I into packaging cups 50, the articles themselves push the web passing over the holding and severing cups 29 into those cups. The two webs are then sealed by the contact of drum 6l and the lips or rims oi cups 29, and the operation is identical from this point. The second web may be prestretched and held in the same manner as in the other gures, or held at the edges in any desired way. It need not be held at the edges if the articles being wrapped are small enough to lie within one of the cups il. i

If it is desired to stretch the sheet material 23 more 'than is accomplished by either form of my apparatus as above described, this can be accomplished by an additional longitudinal stretch created by causing heating drums 3 to move at a slower rate than do chains 3. This is also a convenient way to regulate the amount of stretch. the relative speeds being easily adjusted by any convenient means. If smaller articles are being wrapped, an increase in pre-stretching may be required to provide the same thickness o! thefinal wrapper. The guide rolls 43 are preferably driven at the same peripheral speed as vthe chains t.

'Medici Although where the sheet material 2l has not been previously stretched, I prefer the apparatus illustrated in Fig. 1 or in Fig. 12, that apparatus may be modied so'that the sheet, material is gripped by clamps I3 before it is heated and thus rendered plastic. For example, heating drums i could be mounted on shafts 5 (Fig. 1). the webpassing partially around the drum but being gripped before engaging it; or heating drums 3 could be eliminated entirely, the heating being done by hot air blowers adiusted to heat the webs immediately after the gripping. This gripping of the sheet material prior to its heating is of assistance in the handling of material which has been previously stretched, due to the tendency of such material to shrink.

It is desirable to keep the sheet material at a suillciently-high temperature after it has been heated and rendered plastic and during the stretching and packagingoperation to maintain the necessary qualities including plasticity and tackiness. There arevat least the following' four ways of doing this: adjust thegeneral room temperature, provide hot plates spaced below the web, cover the apparatus wlthfa hood, or blow h'ot air on the material. In Fig; 1, I illustrate one method of blowing hot air on the material. The exhaust from vacuum pump 52 is passed through tubes 63 into a heater Il, thence through tubes into manifolds n which direct the hot airV through the cups Il to pass along'the said sheet material. Relief valve supplies an adequate -supplementary supply of air to the pump. At

present it is preferred to use this method of heating and also have the room -temperature around 85 F. j In describing my ilrst form of apparatus for performing my invention, IA have indicated that portions of webs 23 may be drawn into recesses 2l by vacuum so as to line the concave surfaces of cups Il, or the portions may be drawn down any lesser amount desired. 4In describing my alternative form of apparatus, I have indicated that, rather than using 'a vacuum, the articles themselves may be made to push the webs into the cups. It may be desirable in some-situations to utilize a particular one of these two methods, or to combine them.

For example, it may be desirable to wrap articles using cups which were made for a largerv size of articles without changing to smaller cups. In this case, to ensure a package in which the packaging material conforms closely to the shape and size of the articles, rather than merely relying upon obtaining this result due to the tendncy of the material to shrink. -it is preferable to have the articles themselves push thewebs at least partially into the cups.

Also, vit may be desirable to have the cover of the wrapped articles of' constant thickness throughout, or thicker at some` places than at others.

It has been found thatV when heated thermoplastic material is stretched overthel top of a semi-spherical vacuum mold and suction suilicient to stretch the material to engage the sides and bottom of the mold is applied, the stretching reduces the thickness of the material to a greater extent at the center than at the-sides so that the covering of articles wrapped on my machine when the lm isv forced into the cups in this manner might beof greater thickness adjacent the circumferential seal with thinner and weaker covering at points more distant therefrom.

. It has also been found that -when articles are forced into the center of sections of heated thermoplastic material held about the edges, the material is stretched. reducing the thickness of the material to a greater degree at the portions adjacent the held edges than at the point of contact with the article, so that the covering of articles wrapped on my machine when the film is forced into the cups in this manner might be of greater thickness at points distant from the circumferential seal with thinner and weaker covering at points adjacent thereto.

If the cover of packaging material is somewhat larger than the article wrapped therein during the time the material is following its natural tendency to shrink, it may itself form a cover of uniform thickness conforming closely to the article, the thinner portions of the material being under a relatively higher tension and shrinking proportionately more than the thicker portions. By forcing the material into the cups partially by vacuum and partially by the article, uniform thickness of the wrapper is ensured, as described and claimed in my copendlng application, Ser. No. 539,971, filed July 12, 1944. It is particularly desirable to be able to regulate the degree of suction to minimize the trapping of air in the wrappers. The relief valve 54, being ad- Justable, supplies this need for adjustability. Although the invention has been described especially as with respect to Pliofilm, it will be obvious that other elastic films may be used, especially those which are thermoplastic in the sense that they become plastic, at least during the continuation of the process, by the application of heat. 0f course, with any type of film, the manufacturer should be asked to supply the type best suited for this process. In the caseoi Pliolm, forA example, some Plioillms have given better results than others. That which seems .best among those now being furnished by the Goodyear Corporation is that which they designate Plioillm P211, gauge.

Although I have described my invention-in detail and, therefore, utilized certain specific terms and language herein, it is to be understood that the present disclosures are illustrative. rather than restrictive, and that changes and modiiications may be resorted to without departing from :se spirit or scope of the claims appended here- It is believed that the term "stretched wherever used in this application is l intended to mean more than merely being drawn taut or drawn out to the lms natural length. Where a term broad enoughrto cover the latter condition is desired.

the word outstretched is sometimes used. When reference is made to an increase in an overall dimension, this indicates stretching by pulling whether or not there may also be stretching by forming pockets. The term non-stretchable is, of course, not used in an absolute sense, since any material can bestretched inilnitesimally and cold Plioiilm can be stretched appreciably even though its stretchability is not comparable to that .of heated Plioillm.

It is also desired to note that the term "progressively hasbeen intended to connotethe performance of a step on successive parts of a sheet whether or not specific reference-is also made tosuccessive parts of the sheet. In like manner, in stating .that one step is performed y after another,- reference is. of course, to a particu- Y" naad-rsi have an invisible coating resulting from drying iilm of soap solution, to prevent adhesions between wrappers. This may be accomplished by spraying or otherwise coating the under surfaces of the webs before they reach the heating drums I so that the water is evaporated by the lheat of the drums.

Although some reference has been made to oranges. it should be recognized that this is typical of all citrus fruits, with which the invention is especiallyV advantageous. Of course the invention is also highly useful in packaging other articles, including loose or fluid material.

I claim:

1. In the method of preparing sheet material for packaging purposes, the step of stretching said material, which comprises gripping the edges thereof by opposed rows of fingers carried by pivotally-mounted arms, softening said material by application of heat thereto, increasing the lateral distance between oppositely-disposed rows of said fingers and, beginning at a predetermined point, increasing longitudinally the distance between the material-gripping portions of said fingers located on each side of said sheet.

2. The method of stretching plastic sheet material, which comprises gripping the edges of said material by opposed rows of fingers carried on pivotally-mounted arms, increasing the lateral distance between oppositely-disposed rows of said fingers by raising said arms from horizontal to substantially vertical positions and, beginning aty a predetermined point, increasing longitudinally the distance between said fingers carried by said arms located on each side of said sheet.

3. The method of stretching plastic sheet material, which comprises gripping the edges of said material while in motion by opposed rows of gripping members carried on pivotally-mounted arms, increasing the lateral distance between oppositely-disposed rows of said gripping members by raising said arms from a substantially horisontal to a substantially vertical position and.

beginning at a predetermined point. accelerating the forward movement of said gripping members by passing the same through an arcuate path of greater radius than that followed by said pivotally-mounted arms.

4. The method of stretching rubber hydrochloride sheet material both laterally and longitudinally, which comprises gripping the edges of said sheet material by ngers carried on pivotally-mounted arms, passing said sheet material around a heated drum, stretching the sheet laterally by forcing said arms on either side of the said sheet away from the center thereof, and stretching said material longitudinally by carrying said fingers and said sheet material around a portion of the periphery of a circle larger in radius than that followed by said pivotaily-4 mounted arms. Y

5. The method vof stretching rubber hydrochloride sheet material both laterally and longitudinally, which comprises gripping the edges of said material by fingers carried on pivotallymounted arms, passing said sheet material around a heated drum, stretching said material laterally by forcing said arms from a substanpurposes, comprising gripping opposite edges of the sheet at a plurality of spaced points, softening at least a portion of the sheet, then stretching the sheet laterally by gradually pulling the edges of said sheet in opposite directions at said points while moving the sheet lengthwise. and then pulling both edge portions of the sheet longitudinally thereof by increasing the distance between said points at which the edges of said sheet are held, thereby increasing the length of the laterallystretched sheet.

'7. A method of packing articles 'comprising softening at least portions of a plurality of sheets of exible material which is substantially nonstretchable at atmospheric temperature, exerting force on the softened sheets and thereby increasing the width and length of the sheets, then exerting pressure on each sheet in a direction substantially perpendicular to the surfaces thereof to form confronting cavities in the sheets, enclosing an article in the cavities and causing portions of the sheets surrounding the cavities to adhere to one another to seal the articles within the cavities, and finally severing the enclosed article from the unused portion of said sheets.

8. In an apparatus of the character described, first means for moving a web of flexible, normally non-stretchable material, means for softening at least a portion of said web while propelled by said first means, means for gripping the edges of said web, means for stretching. said softened portion of said web longitudinally and laterally while being held by said gripping means, means for forming a cavity in said softened portion after it has been stretched, and means for depositing an article in said cavity.

9. In an apparatus of the character described. first means for moving a web of flexible, normally non-stretchabie material, means for softening at least a portion of said web while propelled by said first means, means for stretching said softened portion of said web longitudinally and laterally, and means for forming a cavity in said softened portion after it has been stretched.

10. In an apparatus of the character described,

means for preparing sheet material for packaging purposes, comprising opposed rows of gripping elements adapted to grip opposite edges of sheet material, each element having a pivotally mounted arm, means for moving the gripping elements of the rows in unison in the same general direction, means for softening the sheet material as it is propelled by said gripping elements, means for increasing the lateral distance between the gripping portions of oppositely-disposed gripping elements as they travel, and means for increasing longitudinally the distance between the gripping portions of the gripping elements of each row for stretching the sheet longitudinally.

11. In an apparatus of `the character described, iirst means for gripping and moving a plurality of webs of flexible, normally nonstretchable material vtoward one another, means for softening at least a. portion of said webs while heid by said rst means, means cooperating with said first means for stretching said softened portions of said webs longitudinally `and laterally while being held by said rst means, means for forming opposed cavities in the softened portions of the webs after they have been stretched, and means for depositing an article in said cavities.

12. In an apparatus of the character described, first means for gripping and moving a plurality of webs of flexible, normally non-stretchable material toward one another, means for softening at least a portion of said vwebswhile held by said first means. means cooperating with said first means for stretching said softened portions of said webs longitudinally and laterally while being held by said iirs't means, means for forming opposed lcavities in the softened portions of the webs after they have been stretched, means for depositing an article in said cavities, and means for severing the enclosed article from said webs.

13. The method of stretching plastic sheet material, which comprises gripping the edges of said material vby opposed rows of fingers carried on pivotally-mounted arms, increasing the lateral distance between oppositely-disposed rows of said iingers by moving said arms about their respective pivots, and beginning at a Ypredetermined point, increasing longitudinally the distance between said fingers carried by said arms locatedA on each side of said sheet.

14. The method of stretching plastic sheet material, which comprises gripping the edges of said material while in motion by opposed rows of gripping fingers carried on pivotally-mounted arms, increasing the'lateral distance between oppositely-disposed rows of said fingers by moving said arms about theirvrespective pivots, and beginning at a predetermined point, accelerating thefforward movement of said lingers by passing the same through an arcuate path of greater radius thanthat followed vby the pivots of ksaid pivotally-mounted arms.

\ 15. The vmethod of stretching rubber hydrochloride sheet material both laterally and longitudinally, which comprises gripping the edges of said material by fingers carried on pivotallymounted arms, passing said sheet material around a'heated drum, stretching said material laterally by moving said arms about their respective pivots and stretching said sheet longitudinally by carrying said fingers around a portion of the'periphery of a circle larger in radius than that followed by the pivots of saidpivotally-mounted arms.

16.i In an apparatusl ofthe character described, iirst meansfor moving a web of flexible, normally non-stretchable material,l means for softening at least a portion of said web while propelled by said first means, means for gripping the edges of said web,l means forV continuously stretching said softened portion of said web longitudinally and laterally while being held by said gripping means throughout theY stretching operation, means lor forming a cavity by Vfurther stretching vsaid softened, stretched portion, and means for depositing an article, jin said cavity.

17. The method of reducing the thickness of plastic material in web form which comprises advancing a webof such material, progressively holding theweb at'spaced points along the longitudinal edges thereof, progressively moving the' opposed points laterallyawayd from oneanother to stretchthe web transversely, and progressively longitudinally"stretchingfthe portion of the web between s aidpoints while said portions of the web are being held against lateral contraction.

"118;` The method' of `reducing the thickness of plastic-material'in web form whichcomprises advancing a web of such material, progressively holding the web at spaced'points'along the longi`` tudinal edges thereof, progressively' moving the opposed points laterally away from oneanother to stretch the web transversely; longitudinally stretching the portion of the web between lsaidipoints while ysaid portions of .the webvv 'arebeing held against lateral contraction, andi'deformingthe'webin a direction perpendicuprogressively lar to its face to form a pocket and furtherstretch the web, and depositing an article in said pocket. 19. The method of stretching plastic material in web form to reduce its thickness, which comprises progressively grasping successive portions of the web by individual gripping means disposed in rows along the opposed longitudinal edges of said web and then progressively increasingthe` lateral distance between the opposed rows of saidy gripping means and increasing .the longitudinal distances between the individual gripping means n each edgeof said-web.

20.f The method of stretching plastic material. which can be softened byheat, in web form to reduce its thickness, which comprises progressively heating said material to soften it, proa 'gressively grasping successive portions of the lweb by individual. gripping, means disposed in rows along the opposed longitudinal edges of said webv and then progressively increasing the lateral distance between the'opposed rows of said grip-- ping'means and increasing'the longitudinal dis-V tances between the individual gripping means 0n each edge ofsaid web.

D21. Packaging apparatus comprising. means for progressiveily stretching a web of eastic terial at least to one-half -ofits original thickness, said portions of the material material sumciently to reduce its thickness and holding itstre'tched, and means effective while it is still held stretched for stretching the materialfurther to form pockets and then enclosing successive articles in said pockets. v

' 22 Apparatus for progressively stretching web material to reduce'the thickness thereof includingl traveling holding means for the opposite lon.- gitudinal edges ofthe web, the holding meansfor at least oneedge comprising a series of hold-.

ers each being carried by atraveling arm pivoted at a point substantially spaced from the holding means on each arm, said arm Ibeing pivotal to move the holder in adirection to stretch the web transversely, and means for-thus pivoting the arm as it travels. y

23. Apparatus for progressively stretching web materialto reduce the thickness thereof including traveling holding means for the opposite longitudinal edges of the web, the holding means' for at least one edge comprising a series of holders eac-li being carried by` traireling arms pivoted ata point substantially spaced from the holding means, on said arm, said armI -being pivotal tomove the holder in a transversely, arm as it travels; said holding means including a member about which the web inwardly from the held portion is wrapped as the arm pivots, wheredirection to stretch the web by the holding of the web is aided by a snubbing'f action.

24. The method of wrapping articles in a strip of thermoplastic materialcomprising progressively stretching successive portions-of the maforming pockets in for further stretching the said portions, deposf itlng successive article to be wrapped in said pockets, closing and sealing said pockets about the retained'articles, andsevering the wrapped articles from the strip.

25V. The method of preparing elastic nlm for packaging purposes comprising progressively stretching successiveportlons of the lrn to decrease its thickness, holding said stretched portions'of` the iilm against contraction, then further st etching the said portions ofthe lm while held against contractionv to form pockets to 7 5 receive 'the article to be wrapped.

and means forthus pivoting the' 26. The method of preparing a continuous web of materialv which may be made more stretchable by softening, comprising progressively softening successive portions of said material, then exerting pulling forces on the softened portions there of in more than one direction and thereby increasing the overall length and width of the successive portions of the web. and afterwards exerting pressure against one face of the successive portions of the web in a direction substantially perpendicular to said face to further stretch said material in a direction substan row while the sheet is held thereby, to stretch the sheet.

28. Apparatus for progressively stretching successive portions of sheet material including spaced rows of traveling holding means including sheet-engaging portions for holding the longitudinal edges of the sheet material at spaced points, means for progressively feeding sheet material to said holding means in generally outstretched condition, and means for progressively separating the rows laterally and progressively longitudinally separating from one another the sheet-engaging portions of each row while the sheet is held thereby, to stretch the sheet.

29. Apparatus for progressively stretching web material to reduce the thickness thereof, including spaced rows of holders, each carried by a traveling arm pivoted at a point substantially spaced from the holder on said arm, said arm being pivotal to move the holder in a direction to stretch the web transversely, means for thus successively pivoting the arms as they travel, and means for successively swinging the arms of each row angularly away from the following arm to progressively separate the holders in each row from one another. v

30. The combination of spaced rows of holders for holding a web therebetween, each holder being carried by a traveling arm, means for progressively feeding sheet material to said holders in generally outstretched condition, means for successively swinging the arms of each row angularly away from the following arms to progressively separate the holders in each row from one another, and means effective on the portion of the web held by the holders which have thus been separated for further stretching the web by forming pockets therein.

31. The combinationof spaced rows of holders for holding a web therebetween, each holder being carried by a traveling arm pivoted at a point substantially spaced from the holder on said arm, said arm being pivotal to move the holder in a direction to stretch the web transversely, means for progressively feeding sheet material to said holders in generally outstretched condition. means for thussuccessively pivoting the arms as they travel, means for successively swinging the arms of each row angularly away from the following arms to progressively separate the holders in each row from one another, and means effective on the portion of the web held by the holders which have thus been separated for further stretching the web by forming pockets therein.

32. Apparatus for progressively stretching web material to reduce the thickness thereof including traveling holding means for the opposite longitudinal edges of the web, the holding means for at least one edge comprising a series of holders each being carried by a traveling arm pivoted at a point substantially spaced from the holding means on'each arm, said arm being ypivotal to move the holder in a direction to stretch the web transversely, means for thus pivoting the arm as it travels, and means for feeding web material to said holding means but retarding it at a point spaced from the holding means to a speed less than that of the holding means to` preliminarily stretch the web longitudinally.

33. Apparatus for progressively stretching suecessive portions of sheet material including spaced rows of traveling holding means including sheetengaging portions for holding the longitudinal edges of the sheet material at spaced points, means for progressively feeding sheet material to said holding means in generally outstretched condition and for controllably retarding the sheet material at a point spaced from the holding means to preliminarily stretch the sheet material longitudinally, and means for progressively separating the rows laterally and progressively longitudinally separating the sheet-engaging portions of each row While the sheet is held thereby, to stretch the sheet.

34. Apparatus for sealing an article in a film of predetermined thickness, thinner than film presented to the apparatus, including opposed rows of traveling holders adapted to hold opposed edges of a film, means for moving the holders apart to stretch the film a predetermined invariable amount, suction means effective on the stretched film to suck pockets into the film, and including means for regulating the strength of the suction to correlate the size of the pocket to the size of the article, means for enclosing the article in the pocket, and means for feeding a web of material to the holders and for adiustably retarding the movement thereof at a point spaced from the holders to adjustably prestretch the film and adjust the net total strength thereof.

35. Apparatus for sealing an article in a skintight film of thermoplastic material including a pair of cooperative rims, vacuum cup means associated with at least one rim, means for applying a strip of heated thermoplastic material over each rim, means for partially exhausting the air in the cup means to draw the film drawn thereover partially into the cup means to form an undersized pocket in the cup means, the effective strength of the exhausting means being such that the total pocket depth of the two films will not be as great as the corresponding dimension of the article, means for inserting an article in the pocket in contact with the center portion of the pocket and pressing it further into at least one film to stretch the film, said apparatus including means for bringing the rims together to seal the two lms together about the article.

36. The method of sealing an article in a skintight film of thermoplastic material, including stretching strips of the heated thermoplastic film over the lips of approaching rims of greater diameter than that ofthe article, applying a partial vacuum to the back of at least one lm to draw the center of the films stretched over the rim rearwardly, said vacuum being so applied and of such force that combined cavity depthof the lms across the two rims is less than the corresponding dimension of the article, embracing the article between the advancing rims, engaging the opposite sides of the article with the center of the lm drawn into each mold, and closing the molds upon each other, thus further stretching at least one of the films and pressing the films stretched over the rims into engagement with each other to form a heat-sealed skin of film. 37. In an apparatus of the character described, means for moving a plurality of webs of flexible, normally non-stretchable material toward one another and curving them to bring their faces into contact, means for progressively softening successive portions'of said webs, means for progressively. stretching said softened portions of said webs `longitudinally and laterally, means for forming opposed cavities in said softened stretched portions, and means for releasing articles above said cavities in timed relation to their movement to cause the articles to drop into a cavity as it is about to be sealed.

38. Apparatus for stretching web material including a drum, means for carrying web material to and around the drum including gripping means adapted to grip the opposite edges of the web and move apart to stretch the web, andsag preventing means adjacent the drum to hold the web away from the drum during stretching.

39. Apparatus for stretching web material including a drum, means for carrying web material to and around the drum including gripping means adapted to grip the opposite edges of the web and move apart to stretch the web, and sag preventing means adjacent the drum to hold the web away from the drum during stretching, including rotary means extending transversely of the web and driven with approximately the peripheral speed of the drum.

40. Apparatus for heating and stretching web material, including a heating drum, means for running the web around the drum with the full width of the web in contact therewith, series of gripping means, and means for applying the successive gripping means to the opposite edges of the web after the web leaves the drum, and means for moving the gripping means along each edge apart from each other lengthwise of the web while the sheet is gripped thereby.

41. Packaging apparatus comprising means for progressively stretching a web of elastic material sufliciently to reduce its thickness and holding it stretched, means effective while it is still held stretched for stretching the material further to form pockets larger than the articles to be wrapped and then for enclosing successive articles in said pockets, and means for heating the closed pockets to allow the escape of any entrapped air holding portions of the pockets away from the enclosed articles.

a2. Packaging apparatus comprising means for progressie-'ely stretching a web of elastic material sufficiently to reduce its thickness and holding it stretched, means effective while it is still held stretched for stretching the material further to form pockets larger than the articles to be wrapped and then for enclosing successive articles in said pockets, and means for shrinking the closed pockets to conform to the size and shape of the articles enclosed therein ing the escape of any entrapped air.

43. Means for wrapping fills including means for stretching a lm to reduce lits thickness while maintaining it substantially nnpocketed, means fp rnstretching it further by forming pockets therein, means for sealing the pockets with additional film, and means for inhibiting adhesions oi the wrappers including means for applying soap solution to the surfarce of the film forming the outer surface of the wrapper, and means subjecting the coating to heat to dry the coating before forming pockets therein. l

44. Means for wrapping illls including means for applying soap solution to the surface of a web of film as it moves, means for heating lthe web to which said solution has been applied to dry the coating and soften the film to permit it to be stretched and sealed, means for thereafter stretching the web to reduce its thickness while by allowmaintaining it substantially unpocketed, means for thereafter stretching it further by forming pockets therein, and means for thereafter sealingr the pockets around a fill in said pockets.

45. The method of sealing a spherical article in a skin tight film of thermoplastic material of uniform thickness throughout its entiresurface including stretching strips of the heated thermoplastic fllm over the lips of approaching similar semi-spherical molds of slightly greater diameter than that of the article, partially exhausting the air in each of the molds to draw the center of the lms stretched thereover substantially halfway to the bottom of each mold, thus reducing the thickness of each iilm at the center, embracing the article between the advancing molds, engaging the opposite sides of the article with the center of the illm drawn into each mold, and closing the molds upon each other further stretching the lms between the lips of the molds and the article, thus reducing the thickness of each film at the sides, while the lips press the films stretched thereover into engagement with each other to form a heat sealed skin of film of uniform thickness about the article.

46. The method of sealing a generally spherical article in a skin tight film of thermoplasticmaterial stretched to uniform thickness throughout its entire surface including stretching strips of heated thermoplastic material over lips of approaching similar suction cups of slightly greater diameter than the article, partially exhausting the air in at least one of the cups to draw the center of the film engaging the lip thereof substantially halfway to the bottom of the cup, thus reducing the thickness of the film especially at A its center, embracing the article between the advancing cups, engaging the opposite sides of the article with the centers of the nlm engaging each cup, and closing the cups upon each other thereby furthed stretching the films between the lips of the cups and the article, thus reducing the thickness of each lm at the sides while the lips press the films stretched thereover into engagement with each other to form a heat-sealed skin of film of uniform thickness about the article.

47. The method of sealing an article in a skin tight film of thermoplastic material including stretching a strip of the heated thermoplastic film over the lips of a vacuum cup of slightly greater diameter than the article, partially exhausting the air in the cup to draw the center of the nlm stretched thereover substantially halfway to its intimate depth, thus reducing the thickness of the film especially at the center. in-

serting the article inthe pocket of the illm thus formed in the cup and engaging the article with the center of the tllm, pressing the article further into the cup thereby further stretching the nlm between the lip oi the cup and the article, thus reducing the thickness of the nlm at the sides, and sealing another strip oi thermoplastic material covering the other side of the article to the first-named strip at the' lip of the cup.

48. The method of sealing a generally spherical article in a film of thermoelastic material having predetermined distribution of thickness including stretching strips of heated thermoelastic material over lips oi approaching similar suction cups of greater diameter than the article; drawing the center oi the film engaging the lipsof at least one oi the cups into the cup a predetermined depth and reducing the thickness of the illm, with greater reduction at its center than adJacent the lip, by -partially exhausting the air in the cup; embracing the article between the approaching cups by engaging the opposite sides of the article with the centers of the lms engaging the lips of the cups; and, by closing the cups upon each other around the article, stretching the illms between the lips of the cups and the article and reducing the thickness of each nlm, with greater reduction adjacent the lips than at the centers, to such an extent that the wall thickness of the nlm previously drawn partially into the cup is made substantially more uniform, while the lips press the films stretched thereover into engagement with each other to form a heat-sealed skin of film-about the article.

49. The method of sealing a generally spherical article in a film of plastic material, which may be rendered stretchable by heating it, having predetermined distribution of thickness including heating strips of said material; stretching said strips over lips of similar suction cups of greater diameter than the article; drawing the centers of said strips 'into the cups a predetermined depth and reducing the thickness kci? said strips, with greater reduction at their centers than adjacent the lips, thereby forming initial hollow shapeshaving predetermined distribution of thickness, by partially exhausting the air in the cups; substantially maintaining said shapes until further stretching begins; engaging the opposite sides of the article with the centers of said shapes while said material is readily stretchable; and, by closing the cups upon each other around the article, enlarging said initial hollow shapes and reducing their thickness, with greater reduction adjacent the lips than at the center, to such an extent that their wall thickness is made substantially more uniform, While the lips press the strips stretched thereover into engagement with each other to form a heatsealed skin oi lm about the article.

50. The method of sealing a generally spherical article in a film of thermoelastic material including stretching heated strips of said material over lips of approaching similar suction cups of greater diameter than the article; drawing the center of the iilm engaging the lip of at least one oi' the cups toward the bottom of the cup and reducing the thickness of the illm, with greater reduction at its center than adjacent the lip, by partially exhausting the air in the cup; embracing the article between the approaching cups by engaging the opposite sides of the article with the centers of the iilms engaging the lips ot the cups; and, by closing the cups upon each other around the article, stretching the films between the lips of the cups and the article and reducing the thickness of eachy nlm, with greater reduction adjacent the lips than at the centers. to such an extent that the wall thickness of the illm previously drawn partially into the cup is made substantially more uniform. while the lips press the illms stretched thereover into engagement with each other to form 'a heat-sealed skin of lm about the article.

51. The method of sealing an article in a wrapper forming a taut elastic skin oi' sheet material including stretching heated strips oi elastic, heat-scalable sheet material over lips of approaching similar suction cups of greater diameter than the article; drawing the center oi the iilm engaging the lip of at least one of the cups toward the bottom of the cup and reducing the thickness of the nlm, with greater reduction at its center than adjacent the lip, by partially exhausting the air in the cup; embracing the article between the approaching cups, by closing the cups upon each other around the article, stretching the illms between the lips of the cups and the article and reducing the thickness of each illm, with greater reduction adjacent the lips than at the centers, to such an extent that the wall thickness of the nlm previously drawn partially into the cup is made substantially more uniform, while the lips press the films stretched thereover into engagement with each other to form a heatsealed skin ci nlm about the article;l and releasing the said elastic skin' to cause it to contract until it has drawn itself tightly about the article.

WILLIAM S. CLOUD.

REFERENCES crrnp UNITED STATES PATENTS Number Name Date 1,481,866 Heist Jan. 29, 1924 1,647,289 Gwinn Nov. 1, 1927 1,989,944 Quigg Feb. 5, 1935 2,047,497 Studt July 14, 1936 2,074,285 Studt et al Mar. 16, 1937 2,079,584 Hazell et al May 4, 1937 2,120,328 Ferngren June 14, 1938 2,141,318 Salsberg Dec. 27, 1938 2,152,101 Scherer Mar. 28, 1939 2,168,651 McCoy Aug. 8, 1939 2,232,783 Hausheer Feb. 25, 1941 2,289,668 Mallory July 14, 1942 2,334,022 Minich Nov. 9, 1943 2,342,977 Snyder Feb. 29, 1944 2,362,653 McGovern Nov. 14, 1944 Certificate of Correction Patent No. 2,490,781 i December 13, 1949.

WILLIAM S. CLOUD It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 30, strike out the comma and Words now abandoned and insert the same after 1944 and before the period in line 28; column 5, line 11, for the Word later read lateral; column 6, line 61, for recesses 58 read recesses 57; column 10 line 75, for is is read 'it is; column 11, line 18, for y, second occurrence, reati on; column 14, line 63, for for read by; line 64, for article read articles; column 18, line 10, for surfarce read surface; line 61, for furthed read further;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the. record of the case in the Patent Office.

Signed and sealed this 18th day of April, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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