US3085479A

US3085479A - Devices for forming heat sealable blanks into box form and method

Info

Publication number: US3085479A
Application number: US126689A
Authority: US
Inventors: Hoyrup Sigurd Johannes; Richard V Pagendarm
Original assignee: Atlas General Industries Inc
Current assignee: Atlas General Industries Inc
Priority date: 1961-07-25
Filing date: 1961-07-25
Publication date: 1963-04-16
Anticipated expiration: 1980-04-16
Also published as: GB946732A

Description

April 16, 1963 HOYRUP ETAL 3,085,479

DEVICES FOR FORMING HEIAIP SEALABLE BLANKS INTO BOX FORM AND METHOD Filed July 25, 1961 8 Sheets-Sheet 1 A 26 f 25 Q /3 a? i w 4; 22 T 2/ 22 14 20 I i fin. 4 /2 J @7 245 Fig.

INVENTOR.

Sigurd Johannes Hqyrup Richard M Pagendarm BY M A 7TORNEY April 16, 1963 .S. J. HOYRUP ETAL DEVICES FOR FORMING HEAT SEALABLE BLANKS INTO BOX FORM AND METHOD Filed July 25. 1961 8 Sheets-Sheet 2 IN VEN TOR. Sigurd Johannes Hoyrup YR/chara 1 Pagendarm B ATTORIVY E BLA-NKS D 8 Sheets-Sheet 3 Aprll 16, 1963 S.'J. HOYRUP ETAL DEVICES FOR FQRMING HEAT SEALABL Filed July 25, 1961 INTO BOX FORM AND METHO INVENTOR Sigurd Joha s Hay up R hard V P ndam BY ATTORNEY Fig. 5

April 16, 1963 S. J. HOYRUP ETAL v DEVICES FOR FORMING HEAT SEALABLE BLANKS v INTO BOX FORM AND METHOD Filed July 25. 1961 8 Sheets-Sheet 4.

IN VEN TOR. ohannes Hqyrup 1 Pay en darm M A TTORNEY s. JIHOYRU'P ETAL J Apr! 1963 DEVICES, FOR FORMING HEAT SEALABLE BLANKS INTO BQX FORM AND METHOD 8 Sheets-Sheet 5 Filed July 25, 1961 F. 7 d J h INVf/NTOR l 5; ur a annes o ru 9 Rig/ward l4 Pagenda r m {Puma-MA .M ATTORNEY s. J. HOYRUP ETA 1963 DEVICES FOR FORMING HEAT SEALAIELE. BLANKS INTO BOX FORM'AND METHOD 8 Sheets-Sheet 6 Filed July 25, 1961 A ril 1 1963 S W v 3,085,479

. OYRUP ETAL DEVICES FOR F0 me. HEAT SEALABL BLANKS Filed July 25, 1961 INTO BOX FORM D T a Sheets-Sheet 7 INVENTOR. Sigurd Johannes -f-la rup BYR/chard 1 Pagendarm April 16, 1963 3,085,479

S. J. HOYRUP' ETAL DEVICES FOR FORMING HEAT SEAL-ABLE BLANKS Filed July 25, 1961 INTO BOX FORM AND METHOD 8 sheets sheet 8 INVENTOR.

Sigurd Johannes Hay up YRichard M Pagendarm M ATTORNEY 3 085,47 9 DEVICES non FonMrNo HEAT SEALABLE BLANKS INTO BOX FORM AND METHGD Sigurd Johannes Hoyrup, Monta Vista, and Richard V.

Pagendarm, San Mateo, Calif., assignors to Atlas General Industries, Inc., New York, N.Y., a corporation of Massachusetts Filed .luly 25, 1961, Ser. No. 126,689 9 Claims. (Cl. 93--51) This invention relates to machines for forming flat box blanks into box shape and heat-sealing the box corners by attaching to certain wall panels corner flaps hingedly extending from other wall panels, or by attaching panels of corner gussets to themselves, or to wall panels.

Heat-scalable box blanks are coated with a composition which is non-tacky at room temperatures, but becomes tacky when heated, so that application of heat and pressure produces a bond between two coated surfaces or between a coated and a non-coated surface.

The paperboard from which heat-sealable boxes are made is preferably coated with the heat sealing composition before the blanks are cut and scored, so that no adhesive application is required during the handling of the blank in the forming machine.

Box forming and heat sealing machines are known, and are in use at present, in which a plurality of mandrels move box blanks from one station of the box forming machine to another for performance of the various folding, heating, compressing and other operations. Such machines are relatively large, expensive, and are difiicult -to convert from one box size to another, since such con version necessitates an exchange of all the mandrels and of the corresponding forming devices of the machine.

A different type of machine is the plunger-and-die machine. Plunger-and-die machines are widely used at present for the purpose of forming and gluelessly interlocking box blanks. These machines are not difficult to change from one box size to another, as such conversion necessitates little more than the replacement of a plunger and a forming die for one of a different size, together with a replacement or adjustment of elements of the feeder.

The present invention relates to a machine of the plunger and die type which offers the advantage of being considerably smaller in size, as Well as lower in cost, than multi-mandrel machines.

A principal difficulty encountered in the heat-sealing of formed blanks is the heating of the adhesive to a temperature sufficient to produce tackiness. If the heat is applied to the thermoplastic coating directly and by contact, the coated surface tends to adhere to the heating elements. If, on the other hand, heat is applied to the non-coated back surface of board having a coated front surface, a certain amount of time is required for the heat to penetrate the board to the coating. This makes it impossible to heat and seal simultaneously, particularly where more than two thicknesses of board are involved at the bond area. If now the application of heat were to occur in the forming die into which the blank is forced by the plunger, the blank would have to remain in the die for a time sufiicient to permit the heat to penetrate the board. This time depends on the type of adhesive, the thickness of the board and other factors, but the average amount of time is so great that the machine could not be operated successfully except at an exceedingly slow rate of the order of 15 per minute.

The present invention provides a machine capable of much higher production rates. These are attained by moving the blank into the forming die in a partially preheated state. Preferably those portions of the blank are preheated which are farthest remote from the hot surface 3,085,479 Patented Apr. 16, 1963 of the die into which the blank is forced. A preheater is arranged in advance of the die in a position in which the plunger grasps the blank and moves it into the die in an exceedingly short period of time, so as to preclude cooling of the preheated blank portion which, in itself, has a rather low heat capacity.

In order to produce the necessary time of dwell at the preheater, the arrangement is preferably such that a blank feeder moves the blank from a source of supply to the preheater where the blank remains while the feeder moves out of the way and returns to pick up a new blank. The plunger then engages the partially preheated blank and forces it into the die. The latter motion involves shaping of the blank into box form.

The die is then contractedabout the plunger, or the plunger is expanded, in order to put the adhered blank portions under compressive force. The appropriate portions of the die are heated by electricity or steam and the compression time is so chosen as to permit sufiicient heat penetration of non-preheated portions to produce a secure bond.

During compression the plunger is at rest, the preferred arrangement being one in which the remainder of the machine continues in motion so that, for example, the operation of the feeder is not interrupted. A preferred form of mechanism for producing the requisite plunger dwell form the subject matter of the patent to S. J. Hoyrup, No. 2,997,928, dated August 29, 1961.

Preferably, the preheater is constructed to serve the dual purpose of prefolding the blank in preparation of its entry into the folding die and is mounted within the stroke range of the plunger and centered with respect to the main die. The elements of the prefolding die form obstacles in the path of the blank while the blank is being carried by the feeder, and the feeder moves the blank past the obstacles, whereby a portion of the blank is prefolded with respect to the remainder, generally the box bottom. The blank remains in contact with the prefolding elements, at least some of which are heated.

The heated portions of the prefolding die transfer heat to the blank, preferably to the prefolded blank portions which rest against them due to the fight of the board, i.e., the fold resistance of the board at the crease or score.

The blank may be held in the prefolding die either by friction or by suitable detents or catches under which the blank snaps. The plunger then engages the blank, removes it from the prefolding into the main folding die, thus continuing or completing the folding opera-tions.

According to a preferred embodiment of the invention the main folding die is made expansible and contractible by making opposite ends, or sides, movable while the remaining die sides or ends, respectively, are stationary. The movable die portions are heated, Whereas the stationary elements remain unheated. In this manner the application of heat can be controlled by the time of contraction of the die.

Upon expansion of the die, the heated die elements move away from the box, an air space is formed between the box and the hot die elements, and the transfer of heat to the plunger by conduction is interrupted. This is important as an unduly warm plunger would tend to soften the coating of the box and cause it to stick to the plunger. This applies to inside coated boxes where the coating serves the double purpose of liquid or moistureproofing of the box and the purpose of providing heatsealable areas at the corners.

While the compressive force of the die may be imparted by hydraulic means as in plunger and die type formers for assembling glued boxes, it is preferred to employ ShOlteStlOkG pneumatic servomotors, particularly diaphragm-type actuators.

or 3 The various objects, features and advantages of the invention will appear more fully from the detailed description which follows accompanied by drawings show ing, for the purpose of illustration, a preferred embodi ment of the invention. The invention also resides in certain new and original features of construction and comhination of elements 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 under-stood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

FIG. 1 is a plan view of a representative form of blank suited for handling on a machine embodying the invention;

FIG. 2 is a perspective view of a box or tray set up from the blank of FIG. 1;

FIG. 3 is a perspective view of a box corner in the process of assembly;

FIG. 4 is a sectional view of a sealed box corner, the section being taken on line 4-4 of FIG. 2;

FIG. 5 is a perspective view of the die and feeder portion of a.- machine embodying the invention;

FIGS. 6, 7 and 8 illustrate the sequence of operations performed by the blank folding and sealing mechanism;

FIG. 9 is a perspective view of a portion of the mechanism viewed from below; and

FIG. 10 is a perspective view of a portion of the drive mechanism.

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 drawmgs.

The drawings accompanying, and forming part of, the specification disclose certain specific details of construction for the purpose of explanation of broader aspects of the invention, but it is 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 other structural form than shown.

The blank A shown in FIG. 1 consists of paperboard coated on one side with a heat-scalable coating. The coating renders the board liquidor at least moisture-proof and, in addition, furnishes the adhesive material for sea]- ing the box corners. The coating is applied to that side of the board which becomes the inside of the finished tray and individual blanks are cut from the coated stock in the usual manner on conventional cutting and creasing equipment.

The cut and scored blank A is shown in FIG. 1. It comprises a bottom panel 11 to which

end panels

12 and 13 are articulated along

end fold lines

14 and 15.

Side panels

16 and 17 are articulated to the opposite sides of the bottom panel 11 along

side fold lines

18 and 19.

Corner gussets

20, 21, 22 and 23 connect the end panels and the side panels at the four corner-s of the blank. Each gusset is foldable at a

diagonal fold line

24, 25, 26 and 27 subdividing the gusset structure into two panels a and b, panels a lying adjacent the end panels and panels b lying adjacent the side panels.

It will be noted that the otherwise rectangular blank is notched out at the four corners by removal of small rectangular portions whereby the height of the panel b, measured from

fold lines

18 and 19, becomes greater than the height of the panel a measured from the fold lines 14 and 15. The purpose of this arangement will presently become apparent.

The blank is folded into the form of a tray A by folding the

side walls

16 and 17 upright with respect to the bottom 11 and by folding the end panels 12 and 13' up- (it right with respect to the bottom panel in such a manner that the gussets are folded to the inside of the tray, as shown more particularly in FIG. 3.

The gusset panels a and b are folded along the diagonal fold lines, for example line 24 in FIG. 3 and, due to the difference in height of the gusset panels, the top portion of the panel I), which extends beyond the panel a, comes into engagement with a portion of the end panel 12 having a coating of heat sealingmaterial thereon so that a bond is effected between a portion of the panel 11 and a portion of the end panel, for example pmel 12, as shown in FIG. 4. The resulting corner seal is of double ply thickness within the upper portion and of triple ply thickness within the lower portion of the gusset structure.

The finished tray A is shown in FIG. 2.

With the shape and the folding operation of the blank in mind, it will now be easy to follow the construction and operation of the mechanism for performing the folding and sealing functions. 1

Referring first to FIG. 5, a main folding die is composed of lateral

die elements

28 and 29 which in the illustrated form construction are fixed, and a pair of end die

elements

30 and 31 which, in the illustrated form of mechanism, are projectible and retractable by diaphragmtype servo-motors of which one is visible at 32. The lateral element 29 and the end element 31 nearest the observer are not well visible in FIG. 5 as they are partially obstructed by other structures, but are shown in FIG. 9 showing the mechanism as seen from below.

Referring to FIG. 9 it is seen that the

end elements

30 and 31 are mounted on transverse jaws 33 and 34, respectively, fitted with bushings visible at 35 and 36 and slidable on rods 37 and 38 fixed within a die frame 39. The die frame also carries the diaphragm-type servomotors of which one is visible at 32. Its diaphragm actuator comprises a central stud 4t) pivoted to a connecting rod 41 at 42. The other end of the rod is pivotally connected to the jaw 33 at 43. The corresponding connecting rod 44 of the opposite jaw 34 is visible in part in the drawing and its pivotal connection to the jaw 34 may be seen at 45. It is a hollow pivot pin from which a grease fitting projects.

The end elements of the die are electrically heated, flexible cables for the internally mounted heating element being visible at 46 and 47, and

asbestos pads

48 and 49 are provided between the die elements and the jaws to reduce the conduction of heat to the jaws and the die frame.

Returning to FIG. 5, a prefolding die or device is mounted centered with respect to, and in advance of, the main folding and compression die. The prefolding die comprises lateral prefolding elements 50 and 51, end folding elements 52 and 53 and corner folding elements 54. The corner folding elements are electrically heated and carry creasing elements 55 set at an angle of approximately 45 degrees with respect to the die corner. Two heating surfaces '56 and 57 are adapted to be contacted by portions of the prefolded blank, as will later be seen.

Means may be provided for locking a prefolded blank in the position in which heat is being transferred to it through the

surface

56 and 57 and to prevent accidental removal of a prefolded blank to the top. In the illustrated form of device the end folding elements 52 and 53 are provided with a lip adapted to catch the top edge of a prefolded blank. One of these lips is visible at 52.

A blank feeder 62 of otherwise known construction comprises

suction cups

63 and 64 to which a vacuum line is connected at 58 and 59. At the four corners of the feeder folding rules '60 and 61 point to the ends and sides, respectively. The disposition of the folding rules with respect to the "blank is best seen in FIG. 6.

The operation of the device thus far described is as follows:

The blank feeder 62 removes a single blank from a stack of blanks which may be held in the magazine of known construction and carries it to the prefolding die. FIG. 6 illustrates the instant at which the blank A is being swung into a position above the prefolding die. It is seen that the feeder 62 supports the blank along the side-and-end fold lines and that the folding rules 60 and 61 at the corners lie above the fold lines along which the gusset panels are articulated to the side-and-end wall panels, respectively.

After reaching a position above, but centered with respect to the prefolding die, the feeder descends. This causes the blank first to strike the creasing elements 55 which line up with the diagonal fold lines of the gussets, whereafter the side panels and the end panels are folded in an upward direction by engagement with the lateral folding elements 50, 51 and the end folding elements 52, 53 of the prefolding device.

FIG. 7 shows the blank at the instant at which the cups are about to release the blank, whereafter the feeder withdraws leaving the blank in the prefolding die in a position in which the gusset panels a and b overlie the heating surfaces 56 and 57 of the corner folding elements '54.

FIG. 8 shows the blank A after withdrawal of the feeder 62. The blank is now at rest and heat is being imparted to the surfaces about to be bonded. It is seen more particularly that the gusset panels 12, which are two and three plies removed from the exterior of the finished box and which would be difiicult to heat in the main die by transfer of heat through the several thickness of board, are being heated by intimate contact with the heating surfaces 57 against which they are being forced due to the fold resistance of the board.

A folding and forming plunger 65 now descends and forces the blank A from its rest position in the prefolding and preheating device into the main die with regard to which the prefolding and preheating device is centered. In the main die the blank assumes the shape A shown in FIG. 2. .In order to compensate for the difference in thickness of the gusset structures at the corners, the plunger 65 is recessed at 66 to accommodate the third thickness of board within the recess and to permit full compressive force to be exerted between the top portion of the gusset panel I) and the respective end wall.

FIG. 9 shows the box A during the compression phase. Compression is applied during a fraction of a second, the time being so selected as to permit sufficient heating of the end panels for a satisfactory bond. The time depends, of course, on the temperature of the

compression elements

36, 31, On the thickness of the board, on the heat conduction property of the board, and the type of the adhesive used. It is determined by the experiment and may be varied by running the machine faster or slower or by raising or lowering the temperature of the heating elements.

During the compression the plunger 65 remains at rest. Various mechanical drives are known for accomplishing this, a preferred form of mechanism being the pneumatic drive forming the subject matter of the aforementioned Hoyrup Patent No. 2,997,928. The device comprises, in principle, a piston connected to the forming plunger and a cylinder connected to a reciprocating bar of the engine drive mechanism. At a predetermined moment the piston and, hence, the plunger come to rest, whereupon the compression die is contracted to exert compressive force on the box. In the meantime, the drving cylinder continues its motion for a certain distance, comes to rest, reverses its direction, all of which results in changes in the air pressure below and above the piston. A soon as the compression die is expanded and the plunger 65 is released, air pressure drives the plunger in an upward direction out of the die.

Means are provided for stripping the finished box off the plunger. In the illustrated device spring urged latches 67 on the lateral

folding elements

28 and 29 engage the top edge of the box. The latches are best visible in 6 FIG. 9. Vertical grooves 68 in the plunger 65 provide the necessary clearance with respect to the latches.

The finished box A may be removed from the die by any of a number of known devices such as suction cups, air blasts, etc. In the illustrated device the box remains in the die until it is ejected by the box formed during the next cycle. In order to facilitate the ejection of the box, the center portion of the side walls are slightly bowed in by spring urged plungers 69 (FIG. 9) having rounded heads 70 extending through appropriate apertures in the lateral die

elements

28 and 29. Corresponding grooves 71 in the plunger provide plunger clearance with respect to the heads 70. The side walls are bowed in to a dimension smaller than the corresponding dimension of the bottom panel 11 of the box so that the bottom of the next box comes to rest on the bowed-in side walls of the last formed box and pushes it out of the die.

FIG. 10 illustrates a portion of the machine drive. A belt driven pulley 72 has a sprocket gear connected to it (not visible) which drives a drive shaft 73 through a chain 74. The shaft 73 carries a pinion meshing with a spur gear on the main shaft 75 of the machine. The spur gear and pinion are to the right of the observer and not visible in the illustration. The main shaft 75 performs one revolution per operating cycle and carries a crank behind the plate 76 of the machine. The crank oscillates a lever 77 through a link 78. The lever 77 has a push rod 7? connected to it leading to a cross head 80 slidable up and down on a fixed guide rod 81 of the machine. The cross head carries a transverse bar on its upper end to which the pneumatic plunger drive is connected. Details of such construction are illustrated and described in the aforementioned patent to Ho-yrup.

The main drive shaft 75 carries a cam disk 75 on which a follower 82 of an air valve 83 rides. The air valve supplies compressed air to, and vents compressed air from, the servo-motors through

air lines

84 and 85.

It is evident that the invention may be incorporated in other forms of machines and that the illustrated construction may be modified to suit individual requirements.

What is claimed is:

1. A device for folding a heat scalable blank into box form and sealing the box corners, the device comprising, in combination, a preheater; a feeder for moving a blank from a source of supply and depositing the blank in a position on said preheater; a folding die comprising movable elements forming a contractible die throat; means for periodically actuating said elements to contract said die throat; means for heating said elements; a plunger for moving a deposited blank from said preheater into said folding die between said elements; and means for operating said feeder and said plunger in alternating sequence.

2. A device for folding a heat scalable blank into box form and sealing the box corners, the device comprising, in combination, a preheater; blank retaining means for engaging and retaining a blank in contact with said heater; a feeder for moving a blank from a source of supply to said preheater into engagement with said retaining means; a folding die comprising movable elements forming a contractible die throat; means for periodically actuating said elements to contract said die throat; means for heating said elements; a plunger for moving a blank engaged by said retaining means into said folding die between said elements; and means for operating said feeder and said plunger in alternating sequence.

3. A device for folding a heat scalable blank into box form and sealing the box corners, the device comprising, in combination, a main folding die comprising movable elements forming a contractible die throat; a prefolding device in advance of said main folding die; means for heating said prefolding device; a feeder for moving a blank from a source of supply to a point of rest at said prefolding device in a position in which said device prefolds at least a portion of the blank with respect to the remainder of the blank and transfers heat to the blank; a plunger Whose stroke extends past said prefolding device and through said die for moving the prefolded blank from said prefolding device into said main die; means for operating said feeder and said plunger in alternating sequence; and means timed With respect to said operating means for moving the die elements in a direction to contract the die throat.

4. A device for folding a heat scalable blank into box form and sealing the box corners, the device comprising, in combination, a preheater; a feeder for moving a blank from a source of supply and depositing the blank in a position on said preheater; a folding die comprising a pair of opposite fixed throat elements projectible and retractable to vary the distance between them; means for periodically moving said movable elements into projected position; means for heating said movable elements; a plunger for moving a deposited blank from said preheater into a position between said movable elements; and means timed With respect to said moving means for operating said feeder and said plunger in alternating sequence.

5. A device for folding a heat sealable blank into box form and sealing the box corners, the device comprising, in combination, a preheater; a feeder for moving a blank from a source of supply and depositing the blank in a position on said preheater; a folding die comprising a pair of opposite fixed throat elements, and a pair of opposite movable throat elements forming a substantially rectangular die throat with said fixed elements; a pneumatic diaphragm means operatively connected to said movable elements to contract the die throat upon application of compresssed air to the said pneumatic diaphragm means; means for periodically applying compressed air to said diaphragm means; means for heating said movable elements; a plunger for moving a deposited blank from said preheater into a position between said movable elements; and means timed with respect to the compressed air applying means for operating said feeder and said plunger in alternating sequence.

6. A device for folding a heat sealable blank into box form and sealing the box corners, the device comprising, in combination, a main folding die comprising a pair of opposite fixed first throat elements, and a pair of opposite movable second throat elements forming a substantially rectangular die throat with said first elements; means for oscillating said second elements to contract the die throat periodically; means for heating said second elements; a prefolding die in advance of said main folding die and centered with respect to said main folding die; means for heating said prefolding die; a feeder for moving a blank from a source of supply into engagement with said prefolding die to prefold at least a portion of the blank With respect to the remainder of the blank and preheat at least the prefolded portion; a plunger for moving the prefolded blank from said prefolding die into said main die; and means timed with respect to said oscillating means for operating said feeder and said plunger in alternating sequence.

7. A device for folding a heat scalable blank into box form and sealing the box corners, the device comprising, in combination, a main folding unit comprising a die element and a plunger element adapted to pass into the die, one of said elements being expansible and contractible to exert compressive force on a folded blank between said elements; a prefolding die in advance of said die element; a feeder for moving a blank from a source of supply into engagement with said prefolding die, said prefolding die being in the path of the feeder-engaged blank so as to prefold a portion of the feeder-engaged blank with respect to the remainder of the blank, the prefolding die being centered with respect to the main folding die and disposed Within the plunger stroke so that the plunger carries a prefolded blank from the prefolding die into the main die element; means for heating at least that portion of the prefolding die which engages the prefolded blank portion; means for heating at least one of the elements of the main folding die which is subjected to compressive force by the aforesaid expansion and contraction; drive means for periodically moving said plunger into and out of said die element; means timed with respect to said drive means for expanding and contracting the expansible and contractible element at timed intervals; and means timed with respect to said drive means for operating said feeder.

8. The method of setting up a carton from a blank having portions which in the set up condition of the blank are to overlie and be secured to each other by a thermoplastic adhesive composition pre-applied to the blank and which method comprises transporting the blank by a transfer device to a folding die whereafter a plunger moves the blank into the die to eflect setting up thereof, the method being characterized by [the step of applying heat to portions of the blank from the moment of deposit of the blank at the die by the transfer device, and mainrtaining the application of heat at least until the plunger engages the blank and moves it into the die.

9. Method according to claim 8 in which portions of the blank which are to be preheated are prefolded by the action of the transport device moving the blank against the heating means.

References Cited in the file of this patent UNITED STATES PATENTS 3,008,386 Mosse Nov. 14, 1961

Claims

1. A DEVICE FOR FOLDING A HEAT SEALABLE BLANK INTO BOX FORM AND SEALING THE BOX CORNERS, THE DEVICE COMPRISING, IN COMBINATION, A PREHEATER; A FEEDER FOR MOVING A BLANK FROM A SOURCE OF SUPPLY AND DEPOSITING THE BLANK IN A POSITION ON SAID PREHEATER; A FOLDING DIE COMPRISING MOVABLE ELEMENTS FORMING A CONTRACTIBLE DIE THROAT; MEANS FOR PERIODICALLY ACTUATING SAID ELEMENTS