US2255117A - Method of making boxes - Google Patents

Description

Sept. 9, 1941. f W. E, HELMSTAEDTER 2,255,117

METHOD oF MAKING BoxEs Original Filed Jan.. 2l, 1937 QJMIJV- aJ WLM ATTORNEY Patented Sept. 9, 1941 lvIETHOD OF MAKING'BOXES William E. Helmstaedter, Newark, N. J., assigner to Celluloid Corporation, alcorporation of` New Jersey Original application January 21,1937, Serial No. 121,615. Divided and this application `April 27, 1938, Serial No. 204,548

1 claim. (ci. ifi- 56) An object of the invention is the economic and expeditious production of boxes or containers from lm, foil or sheet stock containing a thermoplastic material. Another object of the invention is the production of boxes from film, foil or sheet stock, wherein the boxes are formed -Without a buckling or wrinkling of the side walls and with a smooth, clean edge at the open end. Another object of the invention is the production of boxes wherein the open end is smooth and free of reentrant angles or nicks which tend to reduce the tearing strength of the article. A still further object of the invention is the production of boxes formed from cardboard, paper, metal or other rigid or semi-rigid material and having a seamless covering thereover or therein in a snug relation thereto, Which covering is made of a thin lm, foil or sheet of the thermoplastic material. Other objects of the invention -will appear from the following detailed description and drawing.

In the drawing, wherein like reference numerals refer to the same or similar elements in the several views,

Fig. 1 is a front elevation, partly in section, of a device constructed in accordance with this invention showing the former in a raised position;

Fig. 2 is a front elevation, partly in crosssection, of the device shown in Fig. 1 with the former in a lowered position;

Fig. 3 is an enlarged View, partly in crosssection, of the former and die in a position just prior to the severing of the finished box from the remaining part of the blank, and

Fig. 4 is an enlarged View, partly in crosssection, of the former and die in a position after severing and heat-sealing the open edge of the box.

The production of stamp-molded boxes from Iilms, foils and sheets requires the use of a heated former and die. Along with the former and dievv there is necessarily means for severing the formed box from the unused part of the blank. The means for severing, or the cut-01T as it is called by the trade, is a shoulder of steel on the former and its contour is identical with that ofthe die into which it must nt exactly, at the rparticular temperature at which the die is operating. Otherwise, should the temperature of the 4die be reduced slightly, as might be the case when it is desired to retain the polish on the .that are more tear resistant and of blank, the die opening will 4contract and the cutoff will get stuck within it or might not pass through. Also, if it is desired to increase the temperature of the die, the die opening will expand, allowing the cut-off to pass through too freely, thereby not completely severing the material and -producing a buckling thereof and/or -a jagged edge.

With this type of device the temperature of the' die and former must be maintained within close limits, say within 1 C. or 2 C. at the most of the temperature for which they were designed. As each type of film, foil or sheet of thermoplastic material requires different temperatures of molding depending upon the amount and kind of plasticizer they contain, the amount and kind of pigments they contain, the type of gloss or other nish desired and other circumstances, the employment of such devices are extremely limited. By employing the method in accordance with this invention, however, the same die and V-former may be employed successfully over a range of temperature changes that vary as much as 10 C. to 50 C. or more. This permits of the use of the same former and die to be employed With film, foil or sheet stock that differs widely .in amount of plasticizer, pigments, dyes and other materials incorporated therein. This also permits the use of a heated die and a cooled former that is preferable in shaping very thin stock. The method even permits of a variance in the thickness of the film, foil or sheet employed on one set of die and former. Y

The method of this invention results in boxes that are free from wrinkles and that Ihave a clean, smooth and heat-sealed edge. By heatsealed edge is meant an edge in which the thermoplastic material has been allowed, due to heat and pressure, to adjust itself to any internal stresses that may have been developed during the molding operation. In this respect it is similar to the heat treatment given glass tubing, etc. upon a freshly cut edge. -The heat-sealing of the edge removes all small nicks, knife marks, Y therefore reduces the possibility of the container tearing. This method of forming boxes produces boxes better appearance than those heretofore made.

A further advantage of this invention is that the device can be used longer without dismantling and/or changing dies and formers. As there is no sleeve action between the die and cut-olf these parts may be made of glass-hard Vsteel which permits of unlimited use without the necessity of repair. In practice it is preferable to make the die of as hard a steel as possible and the cut-olf slightly softer so that any Wear will be on the cut-olf which can be easilyremoved. and trued up. v

ybe used as a container.

In accordance with my invention, I stampmold boxes from thermoplastic lm, foil or sheet material and sever the boxes from the unused portion of the blank by means of heat and pressure, the pressure being exerted upon a line. Furthermore, in the practice of my invention, I may employ a device for stamp-molding boxes from thermoplastic nlm, foil or Asheet material wherein the cut-off member exerts no shearing action but severs the boxes from the unused parts of the blank by a molding action in such a manner that the edge of the box is completely se'vered from the remaining part of the blank and.k

simultaneously heat-sealed to a smooth tearresistant edge.

This invention is applicable to the formation of boxes from any suitable thermoplastic lm, foil or sheet material. For instance, the blanks from which the boxes are to be formed may be made from thermoplastic materials containing nitrocellulose, of any suitable degree of nitrati-on, or the organic derivatives of cellulose such as the organic esters of cellulose and cellulose others. Examples of organic esters of cellulose are cellulose acetate, cellulose formate, cellulose propionate and cellulose butyrate, while examples of the cellulose ethers are ethyl cellulose, methyl cellulose and benzyl cellulose. The blank material may also be made from the mixed ether esters of cellulose, such as ethyl cellulose acetate, or the mixed esters of cellulose, such as cellulose stearate-acetate. This invention is also applicable to the formation of boxes from blanks containingthermoplastic synthetic resins and polymerization or condensation products, such as Yurea formaldehyde resins, glycerol phthalic anhydride resins or any of the polyhydric alcoholpolybasic acid resins and the polymerization products of vinyl chloride, vinyl acetate, their derivatives and substitution products or mixtures of the same, also the polymerization products of acrylic acid esters such as methylmethacrylate. Synthetic rubbers known as Plioform, Duprene, Tornesite, etc., may be employed as the base material of the sheet stock.

The iilm, fo'il or sheet material may contain any suitable eiect materials, such as plasticizer's, dyes or lakes, pigments, filling materials, iire re'- tardants, nacreous substances, etc. For instance, the ii'lm, foil "or sheet material may be formed from cellulose acetate containing up to of metallic oxide pigment, and from 15% to 150% of a suitable plasticizer such as dibutyl tartrate, dimethyl phthalate, Similarly other plasticizers and pigments may be Yused,'depending upon the base material employed triacetin, etc.

and the desired eifect in the nal product.

This invention is applicable to the formation of k'boxes from iilms, foils and sheet stock of any suitable thickness, for instance, from .O01 to .05`

or Vmore inch in thickness. 'Ihe invention is primarily of importance, however, in the forming of boxes y'from films and foils of very thin material, say from .00'1'to .01 inch in thickness. Prior attempts to stamp-mold boxes from such thin ma.-`

terial has resulted in a great waste due to the buckling or wrinkli'ng of the side walls or overheating due to the cut-onc member on the form- 'in'gdevice becoming lodged in the die. The present invention, however, successfully produces` boxes of such thin material on a commercial basis.

, YThe boxes Vformed of the thicker material may The thinner material made from the extremely. thin foils, however,

lacks suiiicient rigidity for most purposes and collapses when lled. The thin boxes, however, have great utility either as a lining or as a covering for boxes made from cardboard, paper, combinations of paper and cardboard, metal, etc. For instance, the very thin foils may be formed into transparent boxes that are slipped over boxes made of cardboard covered with a printed and/or embossed paper such as those used for cosmetic containers. This gives to the box a highly glossy nish having a smooth surface which neither picks up`v 'powder or other dust and which may be readily wiped clean. These very thin outer boxes or shells may be made to snugly fit the more rigid inner boxes and be placed thereon by slipping the thin container, the thin outer shell, over the more rigid container. An instrument similar to a shoe horn which is slipped between the rigid container and the shell has been found to be effective in placing the shell on the `contain- "be printed, embossing or other marks which will be protected from and therefore unaiiiected by the material contained vin the box due to the protection of the lining. Boxes having the appearance of metals may Vbe formed by employing metallic lpigmented thermoplastic material and using the boxes formed of the same as the outer and/or inner covering on more rigid boxes. It is also withinthe scope of this invention to use the boxes 'made of thermoplastic material alone, and tov use two or more such boxesin conjuncvtion with each other to build upa rigid container.

I-t is also to be understood that by boxes is'meant any suitable shaped container cylindrical or otherwise. The edge of the lbox may not necessa'rily be round, but may have an intricate shape depending upon the die and former. Thus besides cylindrical shape the boxes may be square, hexagonal, corrugated-cylindrical, etc,

By employing dyed, .pigmented or filled thervfri'cplas't'ic materials such as those containing essence 'of pearl, Lahin, bers, metallic flakes, etc., land using these over a printed or embossed paper box, many novel effects which were heretofore impossible may be obtained. "'he boxes made from 'thermoplastic material are seamless and there is, therefore, no doubling of the material to 'form a ridge or 'a deepening of the color which i's normally produced in boxes 'formed with an overlapping seam.

The process of the invention will be described 'conjunction 'with the device shown in the 'drawing The deviceA is carried on a suitable base "l that is provided with an upright frame -member 2 for supporting a former and yother parts of vthe device. Mounted upon the base I is -a die 3 provided `with suitable cavities 4 -in which there rr'iay be 'placed 'a heating element or through which may be circulated -a heating fluid. The heating 'fiid is circulated through the cavities 4 by ineens of a 'pipe or hose connection 5 and is withdrawn Vafter circulation, by a .pipe or hose connection e. The :pipes '6r-nose :connections '5 and S may be connected with any suitable source of heating fluid which may be water, steam and the like. In place of a heating huid, however, electric resistance coils, open flame or other suitable means may be placed in the cavities 4 for the purpose of heating the die 3. The base member I is provided with a cut-out portion 'I adapted to register with the cut-out portion 8 of the die to permit of the removal of the formed boxes therethrough.

Mounted upon the upright members 2 are a pair of journal boxes II adapted to contain bearings for the support of a shaft I2. Mounted on the shaft I2 is a gear I3. Also mounted on the shaft I 2 are retaining means I4 and an operating lever I5, which operating lever is in the form of a collar positively fastened to the shaft I2 and having a handle I6 adapted for operating the shaft I2 by the rotation of the lever or handle I6. Also carried on the upright members 2 is a slideway ll adapted to retain and guide a ratchet I8 provided with teeth I9 that register with the gear I3. Thus, by rotation of the handle I6 the ratchet I8 is raised and lowered.

One end of the ratchet I8 is fastened to a former head 2I. The former head 2l carries a former 22 adapted to register with the die 8 in forming the boxes. Also carried by the former head 2| is an enlarged portion 23 that acts as the cut-o member. The former head 2i is provided with an extending plate 24 that contains a conduit 25 leading to the interior of the former head and former. By means of this conduit electric wires, combustible fuel pipes or other means for supplying heat to the former head may be led to the interior of the same, or, as is more preferable, the conduit 25 may be employed to carry heated iiuid to chambers 2S in the interior of the former head, the former 22 and cut-off 23. 'Ihe heating fluid may be introduced and withdrawn from the former by means of pipe or hose connections 21 and 2S. On very thin material it may be preferable to cool instead of heat the former, in which case cooling fluid is circulated through the pipe or hose connections 21 and 28.

Plate 24 may be provided with holes through which pins 3| may pass freely. 'I'hese pins are attached to a hold-down plate 32 and are equipped with adjustable locknuts or abutment members 33 at their opposite end. If desired, the holddown plate 32 may be formed with means similar to the die for heating or cooling the same. Upon raising of the former head and plate 24 that is attached thereto, the hold-down plate is raised, while upon the lowering of the former head and plate 24, the hold-down plate goes to rest upon the die, or the blank of thermoplastic material which rests upon the die, prior to contact of the former with the thermoplastic blank. This holddown plate rests freely and non-hampered on the die and the article being formed but is lifted from the die before another blank is inserted. The pressure exerted by the hold-down plate is determined by its weight and may be varied according to the thickness or toughness of the material being formed into a box.

'Ihe upper edge 34 of the die 3 is slightly rounded while the lower corresponding edge 35 of the cut-olf member 23 is preferably a sharp or right angle corner but it also may be slightly rounded. As the corner 34 is slightly rounded and the corner 35 is preferably a right angle corner they will always meet in a line contact irrespective of the amount of expansion and contraction of the parts 3, 22 and 23. It is preferable to maintain the corner 35 as sharp as possible and this may be accomplished by periodically trueing-up or squaring-up this edge with a stone. On the other hand, corner 33 isv very slightly rounded. The edge 3d may be made sharp and square and then with an oil stone, or the like, may be rounded by taking olf, say, about .01 inch of the metal. As either or both the cut-off member 23 and the die 3 are heated and in view of the pressure exerted between the cut-olf 23 and the die 3, the thermoplastic material will be subjected to heat and pressure along a line contact, thereby severing the same by a molding operation along that line. Due to the heat and pressure the thermoplastic material is caused to flow slightly at that line to a degree suicient to reduce any stress developed in the material at that point, thus producing a heat-sealed tear-resistant edge. I

In operation of the device a blank 36 made of any suitable thermoplasticl material is placed upon the heated die 3. The shaft I2 is then rotated by the handle I6 lowering the hold-down plate 32, therformer 22 and the cut-off 23. The hold-down plate comes to rest on the blank 3G and acts to smooth out and/or hold the blank in place. The former 22 pushes the blank into the die 3 forming a box 37. The cut-off 23 then contacts the thermoplastic material of the box and with the cooperation of the corner 34 of the die pinches off waste portion 33 of the blank.

There is provided a source of compressed air which is connected to the device by the pipe 4I. The pipe di is connected through a valve 2, having a trip handle 43, to a exible conduit 44. One or a plurality of holes 45 are formed in the former, which holes enter at the working face of the former and end in a tap 46 connected to the flexible conduit 44.

After the box 3l has been severed from the unused portion 33 of the blank, the valve 42 is operated blowing the box olf from the end of the former. If desired the former may be raised slightly or completely before the box is blown from the former,

If desired talc, aluminum hydroxide or other solid lubricating agent may be added between the die 3, the blank and the hold-down plate 32. This permits the blank to move into the die with greater ease.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

In a process for stamp-molding boxes and like containers, the steps of molding said articles under heat and pressure from film, foil and sheet stock of thermoplastic material and severing the molded article from the unused portion of the stock, while said article is still in the mold, by pressing the material along the line of severance between an edge and an opposing surface on the mold, said surface being rigid and curved in the direction of relative motion between said edge and said surface and saidy edge being prevented from moving beyond the curved portion of said rigid surface, whereby the severed edge of the article is smooth, .heat-sealed and tear-resistant. WILLIAM E. HELMSTAEDTER.

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