US3511140A - Device for forming and heat bonding gusset corners of a folding box blank bearing a thermoplastic coating - Google Patents

Description

May 12, 1970 s. J. HOYRUP 3,511,140

DEVICE FOR FORMING AND HEAT BONDING GUSSET CORNERS OF A=FOLDING BOX BLANK BEARING- A THERMOPLASTIC COATING Filed July 1, 1968 4 Sheets-Sheet 1 INVENTOR. Jz'gura J Haj/up May 12, 1970 s. .1. H RU 3,511,140

DEVICE FOR FORMING AND '1 BO ING .GUSSET CORNERS ARING OF A FOLDING BOX BLANK BE A THERMOPLASTIC COATING Filed July 1, 1968 4 Sheets-Sheet 2 INVENTOR. Sigurd J. Hay/up I A TTOR/VEY May 12, 1970 s J. HOYRUP 3,511,140

HEAT BONDING DEVICE F FORMING GUSSET CORNERS A FOLD OX BLANK BEARlNG A THER AS'IIC COATING Filed July 1, 1968 4 Sheets-Sheet 5 INVENTOR. Jzgurc/ J. Hay/0,0

(ML, A TTOR/VEY May 12, 1970 5. J. HOYRUP 3,511,140

DEVICE FOR FORMING AND HEAT BONDING GUSSET CORNERS OF 'AAFOLDING BOX BLANK BEARING A THERMOPLASTIC COATING 4 Sheets-Sheet 4 Filed July 1, 1968 INVENTOR. Sigurd J Hay/11,0

a4, ATTORNEY United States Patent DEVICE FOR FORMING AND HEAT BONDING- aware Filed July 1, 1968, Ser. No. 741,616 Int. Cl. B31b J/44 U.S. Cl. 351 6 Claims ABSTRACT OF THE DISCLOSURE The gusset corner portions of a box blank bearing a preapplied thermoplastic coating are heated, while the blank is still in its fiat state, by jets of compressed heated air applied from opposite surfaces. A higher coating temperature is produced on one surface than on the opposite surface, thereby reducing the stiffness of the corner portion preparatory to the folding of the gusset corners. The higher coating temperature is achieved by nozzles directed against the undersurface from which the blank is closely spaced by elements which also assist in the folding of the gusset diagonals. The relatively cooler side of the blank comes to lie against the surface of a plunger which forces the blank through a folding die to fold and bond the corner gusset panels in a known manner.

It is known to erect and adhesively bond the corners of a gusset-cornered folding box from an appropriately designed fiat box blank bearing a preapplied coating of thermoplastic material on opposite surfaces. According to known practice the blank is partially prefolded by a transport device which carries the blank to a forming die at the corners of which heating elements are installed. The cold blank is prefolded to the extent that its corner gussets make surface-to-surface contact with the heating elements or blocks which act on the blank during a period of dwell from the moment the blank is deposited by a transport device until the moment a forming plunger engages the blank to complete the folding operations and effect the bonding of the corner areas while the blank passes through the die.

In high-speed production difficulties arise which have their cause in the relatively high degree of stiffness of paperboard which is plastic coated on opposite surfaces. If the board is bent abruptly, particularly in the process of prefolding of the corner gussets preparatory to moving the gusset panels into contact with the rectangular heating blocks, the board frequently tears at, or near, the gusset diagonal. Also the creasing of the relatively stiff board at its fold lines is often not precise, resulting occasionally in a misshapen corner. In order to reduce such inaccuracies, the transport devices have been fitted with rules or blades acting on the blank at the folding scores to insure that the paperboard creases along the crease scores previously impressed in the blank by the cutting and creasing die. Such supplementary prefolding means on the transport device complicate the machinery and require exchange or adjustment every time the box size is changed.

Other problems arise by the transfer of soft thermoplastic adhesive onto the heating blocks during heating of the coating and/or onto the plunger during the box erection procedure.

The present invention is based on several related considerations which will be stated irrespective of their order of importance.

It is realized that paperboard used for the packaging of frozen foodsfor which gusset-cornered boxes are primarily employed-is a board of considerable initial stiffness. The stiffness is increased by the thermoplastic coating on opposite surfaces. It is realized that the board stiffness can be reduced considerably, particularly at the gusset corner areas by the softening of the coating while the blank is still in its flat condition, thereby facilitating the subsequent folding operation.

It is further realized that the heating of the board may be carried to a higher degree on the surface of the blank which becomes the outside of the box without danger of transfer of adhesive, and that the heating of the surface which becomes the inside of the box should be carried to a lesser degree in order to reduce the danger of transfer of adhesive onto the plunger.

It is also realized that differential heating produces stress in the board in a sense to cause a desirable tendency of the blank to curl in the direction in which the blank is to be folded.

It is further realized that differential heating can be produced by two jets or streams of compressed heated air of initially the same temperature, one being of greater length than the other and, for this reason, subject to expansion cooling to a greater degree than the other, thereby eliminating the need for separate sources of heated air of different temperature. This principle is disclosed in my copending application Ser. No. 571,264 filed Aug. 9, 1966, now Pat. No. 3,394,635, dated July 30, 1968.

In addition, it is realized that in order to keep the board temperature within close limits the spacing of the blank surface from the nozzles employed for high temperature heating must be very accurately gauged and that the element used for the purpose of spacing may be made to perform the additional function of creasing the corner gussets at their diagonals.

These and other considerations, objects and advantages of this invention will appear more fully from the detailed description which follows, accompanied by drawings showing, for the purpose of illustration, a preferred embodiment of the invention. The invention also resides in certain new and original features of construction and combination of elements, as well as steps and sequences of steps hereinafter set forth and claimed.

Although the characteristic features of this invention which are believed to be novel will be particularly pointed out in the claims appended hereto, the invention itself its objects and advantages and the manner in which it may be carried out may be better understood by referring to the following description to be taken in connection with the accompanying drawings forming a part of this disclosure in which:

FIG. 1 is a perspective view of a plunger, die and blank transport mechanism comprising preheating and gusset folding assemblies at the die corners;

FIGS. 2 and 3 are perspective views of two sequential operations performed on a blank by the mechanism of FIG. 1; and

FIG. 4 is a perspective view of the underside of the mechanism of FIGS. 1 to 3 illustrating the completion of the box folding operation.

In the following description and in the claims various details will be identified by specific names for convenience. The names, however, are intended to be generic in their application. Corresponding reference characters refer to corresponding parts in the several figures of the drawings. The drawings accompanying, and forming part of, this specification disclose certain specific details of construction for the purpose of explanation of broad aspects of the invention, but it should be understood that structural details may be modified in various respects Without departure from the principles of the invention and that the invention may be incorporated in, and practiced by, other structures than shown.

Referring to FIG. 1, the lower portion of a box forming plunger 11 and the vacuum cups 12 of a blank transport device 13 of conventional construction are seen above a forming die whose interior or shaft is designated 14.

The die comprises side folding elements 15, 16 and end folding elements 17, 18 for folding into box shape a flat blank placed over the die and driven into the die 14 by the plunger 11.

Four heating devices are mounted above, and somewhat outside the shaft of, the die. Of these heating devices the pairs located at opposite diagonal corners of the die are identical.

The heating devices are essentially hollow bodies comprising a plurality of air discharge apertures or nozzles supplied with heated compressed air through appropriate ducts from a source of compressed air via heat exchangers 21, 22 (FIG. 4). Heat exchanger 21 serves heating devices 19, at the left of FIG. 1 and heat exchanger 22 serves heating devices 19, 20 at the right.

A riser duct 23 extends upwardly from each heat exchanger, the riser having a T at the top which discharges into L-fittings 24 telescopically fitting over the arms of the T. The L-fittings 24, in turn, telescopically fit over nipples 25 which are integral with the hollow bodies 19 and 20, respectively.

Each hollow heater body comprises a horizontally extending L-shaped portion 26 comprising a plurality of air discharge apertures 27 arranged in an L pattern, and a vertically extending portion 28 which has a plurality of steps or corrugations formed on the surface facing the die, there being three steps in the illustrated form. Such steps are suitably formed by machining V-grooves 29 which extend horizontally across the face of the body. The air discharge apertures 30 are provided in the downwardly facing portions of the steps, there 'being three tiers of apertures in each of the heater bodies.

Air is discharged through these apertures or nozzles 30 in downwardly slanted direction against the surface of a blank (see FIG. 2) overlying the L-shaped horizontal heater portions. By reason of the inclination of the surfaces in which the nozzle apertures 30 are formed the latter are barely visible in the figures.

Physical contact between the blank to be heated and the horizontal heater body portions 20 is prevented by spacer elements. These are suitably in the form of vertically disposed blades 31 rounded off toward the die apertures as seen at 32. The blades 31 approximately vbisect an L-angle and for this reason extend at an angle of approximately degrees to the vertical portions of the folding elements 15 to 18. The top portions of the blades 31 project above the top surface of the L portions 26 and thus maintain the blank at an accurately gauged distance therefrom.

The operation of the heating mechanism is best explained by reference to FIG. 2 showing a flat blank A deposited on the spacer blades by the blank transport device 12, 13.

In the deposited position the outer edges of the blank are caught between aligning posts 33, some of which are serrated or threaded at 34 in order to prevent a deposited blank from escaping after withdrawal of the transport device.

The blank A comprises a bottom panel 35, a cov er panel 36 and a rear wall panel 37 therebetween. The box body portion of the blank comprises further a front panel 38 and end panels 39, 40.

The bottom fold lines along which the wall panels 37, 38, 39 and 49 are articulated to the bottom panel 35 are numbered 41, 42, 43, 44. Their extensions define corner gussets of which each corner comprises a pair of gusset panels 45, 46 articulated to each other along a diagonal crease 47.

The cover portion of the blank comprises a cover front flap 48 and cover end flaps 49, 50 articulated to the cover panel 36 along folding scores 51, 52 ,and 53, respectively.

In deposited position the spacer blades 31 underlie the gusset diagonals 47 and keep the blank out of physical contact with the heating devices 19, 20.

Heated air issuing from the upwardly directed nozzles heat the underside of the blank to a relatively high temperature due to the fact that the temperature loss of the air attributable to expansion of the compressed heated air in the surrounding atmosphere is relatively small. The air blast heats the entire corner areas of the blank and the stiffness of the thermoplastic-coated blank is correspondingly reduced at the scores which define the gussets.

As the surface temperature produced at the underside of the blank exceeds the temperature of the top surface of the blank, the blank has a tendency to curl upwardly, in which sense the wall panels and gusset panels are about to be folded.

While the blank corners at the underside are being heated to a high temperature, the top surface is heated to a lesser temperature by the air blast issuing from the downwardly directed nozzles 30 from which the heated air travels a considerably longer distance to the blank surface, at least twice as far as the air from the underside. The air impact temperature at the blank is correspondingly lower and is so selected that the plastic coating remains sufficiently non-tacky, so that it will not adhere, nor transfer adhesive, to the walls of the plunger 11 in the subsequent folding operation (FIG. 3).

It will be noted that the blank transport device 12, 13 is free from any blank-precreasing devices for prebreaking the bottom scores and the gusset scores as were previously required and employed in order to overcome the stiffness of thermoplastic coated blanks.

Immediately after the instance illustrated in FIG. 2 the vacuum cups 12 of the blank transport device release the blank, whereupon the transport device 13 is retracted and the plunger descends (FIG. 3).

The blank creases at the bottom fold lines, the corner gusset panels are creased at their diagonals 47 by the assistance of the spacer blades, and the corner gussets are folded into shallow recesses 56 provided in the plunger ends to accommodate the additional two thicknesses of board at that area.

The zones of highest surface temperature of the blank are on the underside of the blank and are substantially limited to the gusset panels which are pressed together when the plunger enters the die.

High bonding pressure is executed on the folded corner gussets by rollers 57 past which the plunger 11 moves the blank. The rollers are mounted on axles 58 fixedly supported in depending arms 59 which are pivotally supported on the understructure of the die at 60 and are urged toward the plunger by compressed helical springs 61.

In the position shown in FIG. 4 the blank has assumed box shape A, its corners are bonded after having passed the rollers 57, and the box is about to be discharged.

The plunger 11 has only a short additional distance to travel in order to reach the bottom end of the stroke which brings the top edge of the box body beyond catches or strip-off fingers 62. These prevent the box from following the plunger on its upward return stroke.

Air is supplied to the heat exchangers (not shown) from a suitable compressor through relatively large flexible ducts of which one is visible at 63. The plunger may be fitted with cooling ducts 64 through which a cooling liquid may be circulated (FIG. 3).

EXAMPLE The device was operated at the rate of boxes per minute.

Total air volume: 3 cu. ft./min. (8S l./min.).

Air temperature measured within discharge nozzles 27 and 30: 930 F. (500 C.).

Air impact temperature on underside of gusset panels: 600 F. (315 0).

Air impact temperature on top surface of gusset panels: 420 F. (215 C.).

Extent of heated area: Beyond bordering scores of gussets.

Corner bond failure as determined by tearing apart and examining the gusset areas for tearing of fibres: No failure in 50 successive boxes.

What is claimed is:

1. In a device for forming and heat bonding gusset corners of a folding box blank bearing a coating of thermoplastic adhesive, the device comprising a plunger and a die through which the plunger forces the blank, and means at the die corner for applying heat to the blank, the improvement which is characterized by the heating means comprising an upwardly directed first nozzle means for discharging heated air against the underside of a flat blank placed thereover and a downwardly directed second nozzle means for discharging heated air against the top side of the blank, the first nozzle means being disposed below the blank, the second nozzle means being disposed adjacent to and above the blank, and a spacing means for supporting the blank at a distance above, and out of contact with, the first nozzle means, the second nozzle means being so disposed as to cause the air discharged therefrom to travel at least twice as far to the blank as the air discharged from the first nozzle means when the blank is in contact with said spacer means, both said nozzle means being supplied from the same source of heated compressed air.

2. The device according to claim 1 in which the first nozzle means comprising nozzle apertures disposed in an angular outline and in which the spacing means is positioned between the legs of the angle.

3. The device according to claim 1 in which the second nozzle means comprises downwardly directed discharge apertures arranged in two substantially horizontal tiers which are vertically spaced from each other and from the first nozzle means.

4. The device according to claim 1 in which the first and the second nozzle means are combined into a single housing supplied with heated compressed air through a single duct.

5. In the method of erecting a flat gusset cornered box blank into hollow box shape and bonding the gusset panels together and to a box wall -by means of a preapplied coating of a thermoplastic adhesive and involving the heating of the coating to a state of tackiness and the forcing of the blank through a folding die by means of a plunger to erect the blank, fold the corner gusset structure, and bond the gusset panels together and to a box wall, the step of applying, while the blank is still flat, compressed heated air to opposite surfaces of the corner gussets, thereby reducing the resistance to folding of the gussets along the folding scores which define the gusset.

6. The method according to claim 5 in which that surface of the blank which becomes the outside of the box is acted on by air of higher impact temperature than the surface which becomes the inside of the box.

References Cited UNITED STATES PATENTS 3,028,798 4/1962 Allen. 3,085,479 4/1963 Hoyrup et al. 9351 3,192,837 7/1965 Hoyrup et al. 93-51 BERNARD STICKNEY, Primary Examiner

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