US2367698A - Staying paper boxes - Google Patents

Description

`zm., 23, 1945. c. STRAW 2,367,698

STAYING PAPER BOXES Filed Sept. 28, 1940 2 Sheelzs-Shee'tl l &

Jan. 23, 1945. Q STRAW STAYING PAPER BOXES Filed Sept. 28, 1940 2 Sheets-Sheet 2 @TRA w y @02m-KW,

Patented Jan. 23,y 1945 UNITED STATES PATENT OFFICE STAYI-N G PAPER BDXES Clayton Straw, Henniker, N. H., assigner to Henryv Russell Davis, Jr., Winchester; Mass.

Application September 28, 1940, Serial No. 358,784

(Cl. S23-56) 4: Claims.

The present invention relates; in general to ad'- hesive materials, and in particular to the staystrips of tough paper, cloth, or related material which are adhesively applied to the outside angles of paper boxes where two sides meet, so as to hold these two sides in the desired contiguous relation. to each other and to reinforce the corner of the box thus formed. It likewise relates to the aixing of labels and the like to the surfaces of boxes and other articles.

The primary object of the invention is to, provide an improved stay-strip, and method and apparatus for applying the same, which will overcome the numerous objections present in the use of prior forms of stay-strips.

Such prior stay-strips have nearly always comprised a strip of paper coated on one side with glue or other adhesive which is rendered adherent through being'wetted with water. This wetting of the strip givesv rise to a number of drawbacks, of which probably' the most important is that it softens the strip and tends to render it limp, and hence a much thicker strip than isV needed merely to impart the desired strength to the corners of the box must be used in order that it shall have sufficient stiffness to permit it to be properly fed through the stay-feeding mechanism. The result is that when the box is wrapped with its outer coating of paper adhesively applied to put a finish on the box, the stay-strip holds this wrapping out of the planes of the sides of the box so far that there is a distinct and conspicuous bulge, drop, or break at the line where the covering paper descends from the stay to ther sides of the box. These breaks in the smooth aspect ofr the wrapping are so objectionable that they have forced box makers to resort to many attempts to avoid having the stay show through at the corners of the box, such attempts including winding the stay all the way around the box, or even doing away with the stay-strips entirely and applying the covering directly tothe box.

Another objectionto stay Vmaterial which mustl be wetted to render it adherent is that the glue or gum is not rendered suiciently sticky for use the instant the water is applied, but requires a. brief conditioning period for the water to soak in, and this period is varied by the humidity and temperature of the surrounding air, the latter factors being seldom capable of control. Hence a number of highly specialized devices and provisions for adjustment have to be' resorted to, in the effort to correct undesired conditions arising trom atmospheric changes in the airas well as -even a few seconds. fluently recurring occasion for stoppage is the from changes-in the speedfof' operation ofA the machine and in the depth o1- box being made.

For instance, when staying shallow boxes with the common water-activated glue-type of stay the stay is fed so slowlyA after its wetting'that it adheres to and clogs the feeding devices, or in some cases has dried so muchthat it fails to stick to the box at all. Equally objectionable, thel machine has to be run without Afeeding it any box blanks until all dry stay has passed through the stay-feeding and cutting mechanism and wet stay is in position to adhere tothe sidesof the boxes, before getting down to the work of making boxes. 'I'he waste of stay thus cut up and thrown away is very material, as this operation has'to be repeated every time the machine is stopped for In this connection, a fregummingfup of the cutting knives, feeding rolls, guides, andpressers which operate on the wetted gummed stay-strip in `presenting and applying it mechanically to the box, requiring constant cleaning to keep the parts operating correctly.

With the aim of obviatin'g these and other drawbacks, and of attaining other advantageous results and improvements, I have devised a novel and improved stay which is coated on one side with an adhesive which is changed from its dry non-adherent condition to an adherent state through the application of heat insteadfof through the use of moisture as commonly hitherto in the case of the common glued or gummed stay-strip. Since it does not have to be moistened in order to make it ready for use, the stay-strip is made much thinner than heretofore and still is stiff enough to be fed by conventional stay-feeding appliances in use on existing staying machines, since it retains its maximum stiffness throughout the entire feeding andv applying operation, the thinner stay-strip attaining themuch desired end of being inconspicuous beneath the usual cover applied after the box hasbeen set up. Cellophane and related cellulose products, with their tough but limp nature, can be used. For these purposes, the requirements of the thermo-plastic or vheat-activated adhesive are exacting: It must have a melting point well below the temperature at which paper will burn or char, or, unlike animal glue, low enough to be quickly melted by heat passing through the paper of the stay, vwhich, is a poor conductor; it must not become fluid under- Athe heat, and it must set instantly as the temthe box sides together; the material should not be capable either of penetrating or of staining the box or the stay-strip, and equally the covering paper, after the manner in which tar or pitch would act; it should be proof against dampness; it must have no odor or avor which could be imparted to the contents of the box, and must be non-poisonous; preferably, the adhesive should require a higher temperature for its re-melting than on its rst heat-activation, and ideally should be cured through the heating in such manner as thereafter to resist all softening under heat.

A thermo-plastic adhesive satisfying practically all of these requirements is that disclosed in U. S. Letters Patent No. 2,054,112, granted September 15, 1936, to Abrams and Wagner.

With a stay-strip coated with such an adhesive, rendered adherent only when actually .in place against the surfaces to which it is to be aiixed, all trouble with gumming-up of the feeding and cutting devices for the stay-strip is obviated, as they have to deal only with dry stay-strip. With the adhesive strip rendered adherent only in the act of seating it permanently on the box, all the problems of conditioning the adhesive through the interval between rendering it adhesive and applying it to the box disappear.

The invention also lends itself to the development of a new method or procedure of setting up the boxes by machine, forming a part of the present invention, in which the stay-strips are applied, While the box-blank is in flat relation, to one of the two naps of the blank which are to be subsequently bent up to form the sides of the box at a corner, a portion of the stay-strip being left free so as to be subsequently caused to adhere to the other of the sides and thus to complete the corner of the box, after the sides have been bent up into perpendicular relation tol the bottom of the box. Under this procedure, the pressure used in applying the stay-strips can be utilized in most effective manner because it is applied exactly at right angles to the planes of the surfaces forming the sides.

The principles of the vinvention are equally applicable to the task of applying labels to the sides or tops of paper boxes.

Illustrative embodiments of the invention are shown in the accompanying drawings in whichf Fig. 1 illustrates generally the typical manner of applying the improved stay-strip coated with a heat-activating adhesive.

Fig. 2 shows a conventional single stayer modied to enable it to be employed in practising the invention.

Fig. 3 is a view of the presser-devices of Fig. 2, on an enlarged scale.

, Fig. 4 is a fragmentary perspective View of one corner of a covered box stayed with the novel thin stay of the invention, with the parts drawn substantially to scale to show relative thicknesses.

Fig. 5 is a. perspective view of presser devices adapted to be used in a quadruple stayer for practising the invention therewith.

Fig. G-indicates in plan view the step of applying portions of the four stays for a rectangular box to the blank while in rlat relation, in effecting the two-stage method of staying boxes.

Fig. 7 shows the second stage of the method of Fig. 6.

According to the invention in its broadest concept, the strip I, Fig. 1, which may be stay-strip, label, or other article, coated on one surface with the heat-activated adhesive 3 which has set into its non-adherent condition, is presented with its coated surface toward the box 5 or other receiving surface, which latter is backed up by a fixed backing l, the strip I being then pressed i'lrmly against the surface 5 by a heated plunger 9 moving toward and from the backing 1. The means for heating plunger 5 may be various, that indicated herein comprising an electrical resistancetype heating element I I embedded in the plunger near its Working face and supplied with current through suitable wires (not shown) from a source of electrical energy. Preferably the head of the plunger will be separated from its shank by a heat-damper of some sort, to prevent wastage of heat through conduction along the shank, a simple method of reducing such conduction of heat being shown in the present instance and comprising boring a row of holes I2 in nearly contiguous relation across and through the metal of the plunger between its head portion 9 and its shank i3. Copper or an alloy thereof may be used for the head of the plunger if preferred, ,though completely satisfactory results have been attained with ordinary steel. Only moderate degrees of heat need to be imparted to the plunger, and it has been found that a 1D0-watt electrical heating element operating continuously will supply sufficient heat to enable the improved stay-strip to be applied at the rate of 160 operations per minute.

The relative thickness of the stay with respect to the Walls of a paper box of average wallthickness, and the resulting reduction of the bulge Where the covering I4 descends from the stay to the box-side, are indicated in Fig. f1.

The principle of the invention and of the method of applying the stay-strip just described, admit of easy adaptation to use in existing boxstaying machines. For example, in the single stayer of Well-known type shown in Fig. 2, the vertically reciprocating plunger I5 merely requires to be equipped with a special presser head I'I, Figs. 2 and 3, applied to the plunger I5 with intervening insulation I9 and equipped with an embedded electrical heating element 2|, connected by leads 23 with a suitable source of electrical energy. As usual, the presser head Il is formed with a reentrant right dihedral angle 25 in its under surface, coacting with a iixed anvil 2'I having a corresponding salient right dihedral angle to support the two confronting edge portions cf the turned-up side flaps of a box-blank 29 while the heated plunger I1 is pressing a length of stay into adherent contact with the portions of the side flaps at and adjacent the corner of the box. Conveniently the stay-strip I is fed through a cutter 3| iixed in an aperture in the upright wall 33 forming a part of the machine, with the usual cooperating means behind the cutter which serve to bend or crease the stay I down its central longitudinal line, this bent shape approximating the shape of the box corner to which it is to be applied, and thus to make the stay overlap each of the two meeting sides of the box to an equal extent. On its way down to simultaneously press the stay against the bcx sides and activate the adhesive, the rear edge of the presser head I1 coacts with the slot in cutter 3| to shear oi the extruded length of stay I, the remaining distance of travel of presser head Il being so short that the stay after being cut off has no chance to swerve out of its intended position astride the corner of the box.

Any desired or preferred form of known stayfeeding mechanism can be employed to perform the simple operation of `extruding 'a predetervrmined length of stay l through 'cutter 3| at each machine cycle. Since there is no problem of moistening a gummed stay-strip or of handling and feeding a stay-strip after it has beenwetted and its adhesive-coated surface rendered gummy, slippery, or tacky, allv that is needed `from the known types of stay-feeder is a mechanism for unwinding from the roll of stay-strip and feeding straight forward through cutter 3| a predetermined length of dry strip; any one of a number of existing stay-feeding devices such as that of U. S. Patent No. 728,086, granted to Davis and Webster, or of my Patent No. l2,186,772 is capable of performing this simple operation satisfactorily.

The stay-strip will always be ush with the rim of the box, provided the corresponding edges 'of the side-flaps of the box-blank are vbrought "to the same vertical plane as that-onwhich the stay-strip is sheared on by the coaction of cutter 3| and pressure head |1. through having the exposed end of cutter 3| 'inf the plane of the surface of wall 33 against which the rim of the box is pressed when put on the anvil 21 as shown in Fig. 3 to receive the stayangle to receive the corner of the box, and in accordance with the invention is equipped with an embedded electrical heating element 31 fed with electrical current through flexible leads 39 connecting it with a suitable source of electrical energy. The heat produced by this element, as in the prior forms disclosed herein, keeps the head 35 at a temperature below the burning point of the paper but capable of instantly transmitting heat through the stay-strip 36 to the adhesive on the side thereof presented to the box. As in Fig. l, a row of holes 39 bored horizontally through the plunger adjacent its junction with its shank 4| and in closely spaced relation to each other serves as a heat darn to restrain the flow and waste of the heat back along the shank.

The regular stay-feeding devices of the said patfrom within while the corner is being subjected to the pressure of head 35 as the latter sets the stay onto the box.

The fact that the novel stay-strip does not become adherent until the moment of its application to the box-blank, coupled with the fact that its adhesive sets into its dry or non-tacky condition immediately as its temperature drops below the critical point, whichy drop occurs within an instant after Withdrawal of the heated presser, opens the way to a new system or method'. of staying boxes. As shown in Fig. 6, the boxblank 41 while still in its flat relation has four stay-strips 49, cut oi to match the height the sides of the box will assume, adhesively applied to any four suitable ends of the flaps which form the sides of the box after being set up, these pieces of stay being applied so that only half of their width, that indicated in dotted lines and stippling is in adherent relation to the side-flaps, while the other half as shown in solid lines is This is attainedfree at this stage. The yblank while thus prepared and while'still in 'flat relation is then vfed beneath the usual'forr'n 5I of a box machine such as those of the patents'named, which thereupon 'descends to cause the side-aps to be setupin usual manner. The free portions of the stays 49 are then folded around the corners ofthe box into parallel with the side-flapsnot equipped with stay-strips, by means such 'for instance as shown in my Patent No. 2,082,365, and thereupon hotpressed into adherent relation with -these'latter vside-flaps by plungers 53 heated lafter the manner shown in Figs. '1, 3 and 5. Among the advantages, both those already'recited of theinvention and those obviously flowing from thisform'there is the further gain of 'simplifying the mechanics of the machine parts which out, apply, 'and set the stay material in this two-stage manner, that 'all motions yare at right yangles to the path of travel of thebox-blank toward the 'form 5I.

For example, the four `stay-'strips 50 can be fed in at right angles tothe length 'of the blank and just below the plane 'o'f ythe blank in a plane parallel ythereto by knurled `feed-rolls 52 rotated by 'shafts 54, hot-pressed into adherence with theunderside of blank 41 through a portion only of their'width (the stippled area) 'by flat pressers of the necessary area after the manner shown in Fig. 1, and thereafter out off flush with the sideedges of the blank as indicated in Fig. 6 by any desired suitable means (not shown). The blank .is then passed ron to its 'setting-up station where ferent times has been equally unsatisfactory because of the drying of the areas Whose adhesion needed to be postponed. Through the invention, it becomes practicable to render adherent only such areas as are momentarily needed, extending the activation of the adhesive to other or to the remaining areas as required. In particular, this is of value in applying labels to boxes, bottles, fabrics, and other objects, as the label to be applied may be picked up from the supply or stack of labels by the usual suction means, transported into the desired position against the box or other surface, and then heated pressers of localized extent such as 53 brought into contact with areas of the label exposed outside of the suction devices to anchor the label temporarily in the desired position. After being thus spotted in place and the suction devices removed, the box or other article is then moved, without danger of slipping of the label, to a subsequent location where the entire area of vthe label is subjected simultaneously to heat and pressure, causing com plete adherence throughout the entire area of the label. This does away entirely with the problems incident to endeavoring to handle and apply a label after it has been coated with glue or other adhesive in wet state, as the label is brought into its final position with its adhesive in entirely non-adherent condition, and the adhesive then activated in situ.

While I have illustrated and described certain forms in which the invention may be embodied, I am aware that many modifications may be made therein by any person skilled in the art, without departing from the scope of the invention as expressed in the claims. Therefore, I do not wish to be limited to the particular forms shown, or to the details of construction thereof, but what I do claim is:

1. In a paper-box-making machine, in combination, means for supporting the sides of a setup box adjacent a corner thereof, means for feeding stay-strip coated with heat-activated adhesive in non-adherent condition-into a position across the corner, a presser having in its working face a reentrantdihedral angle fitting the outside of the box-corner, an individual heater embedded in the presser and continuously heating the Working face thereof, and means obstructing heat transfer from the heated portions of the presser at and adjacent the working face thereof to the machine parts engaging the stay-strip before the latter arrives in position across the corner.

2. In a pape1boxmaking machine, in com bination, means for supporting the portions of the sides of a set-up box adjacent a corner thereof, means for feeding paper stay-strip coated with adhesive consisting wholly of material rendered tacky by heat into a position across the corner While in unheated and non-tacky condition, a presser'having in its Working face a reentrant dihedral angle fitting the outside of the box-corner and pressing the stay-strip against the latter, means continuously heating the presser to cause it to render the adhesive on the stay- -against the outside of the box-corner, and heatinsulating material obstructing the transfer of heat from the heating means to the machine parts engaging the portions of the stay-strip which have not yet arrived in position across the corner.

3. In apaper-box-making machine, in combination, means for supporting the portions of the sides of a set-up box adjacent a corner thereof, means for feeding paper stay-strip coated With adhesive consisting wholly of material rendered tacky by heat into a position across the corner while in unheated and non-tacky condition, a presser having in its working face a reentrant dihedral angle fitting the outside of the lbox-corner and pressing the stay-strip against the latter, and means continuously heating the presser to cause it to render the adhesive on the stay-strip tacky in the act of pressing the staystrip against the outside of the box-corner, while avoiding heat transfer to other machine parts and thence to the stay-strip before the latter arrives in position across the corner.

4. In a machine for applying stay-strip coated with adhesive on only one surface to the corner of a set-up paper box, in combination, means supporting the box from within, means feeding stay-strip coated solely with heat-activated adhesive on only one surface and in non-adherent condition into position across the corner of the box, means applying heat to the uncoated surface of the stay-strip passing through the stay-strip and converting the adhesive at the other surface from non-adherent t0 adherent condition after arriving in such position, and simultaneously pressing the stay-strip into adherence with the corner of the box, and means obstructing trans- -strip tacky in the act of pressing the stay-strip 35 fer of heat from the heat-applying means to the portions of the stay-strip not in position across the corner.

CLAYTON STRAW.

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