US3628982A

US3628982A - Method of applying hot-melt glue

Info

Publication number: US3628982A
Application number: US781545A
Authority: US
Inventors: Charles C Krug
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-12-05
Filing date: 1968-12-05
Publication date: 1971-12-21
Anticipated expiration: 1988-12-21

Abstract

A method of applying hot-melt glue to an object consisting of the steps of heating a transfer bar to a temperature high enough to melt the glue, pressing said bar against solid hot-melt glue to coat said bar with a film of liquid glue, and pressing said bar against said object to transfer said glue thereto.

Description

United States Patent Charles C. Krug 607 East 5th St., Summit, Mo. 64063 781,545

Dec. 5, 1968 Dec. 21, 1971 lnventor Appl. No. Filed Patented METHOD OF APPLYING HOT-MELT GLUE 7 Claims, 4 Drawing Figs.

11.8. C1 117/38, 117/12 0,118/202,118/243,118/263 1nl.Cl 844d 1/20, 844d 1/02 Field of Search 101/426; 117/38,63, 121, 120; 118/263, 202, 243;295/290, 291; 320/578 Primary ExaminerA1fred L. Leavitt Assistant ExaminerEdward G. Whitby Attorney-John A. Hamilton ABSTRACT: A method of applying hot-melt glue to an object consisting of the steps of heating a transfer bar to a temperature high enough to melt the glue, pressing said bar against solid hot-melt glue to coat said bar with a film of liquid glue, and pressing said bar against said object to transfer said glue thereto.

METHOD OF APPLYING HOT-MELT GLUE This invention relates to new and useful improvements in the application of glue, and has particular reference to a transfer method of applying hot-melt glue. The method of the present application can be used, for example, in applying inventory control tickets to merchandise for sale, the tickets being removed as the merchandise is sold and used to facilitate a continuous running inventory of stock, and will be so described, although it will be readily apparent that the invention has application generally in many other usages.

Hot-melt glue has certain advantages in the above usages, as well as many others, in that is requires no moisture to activate it, that is provides a more secure attachment than other adhesives, and that it requires very little pressure to make an adequately secure connection, thus making it well adapted for hurried or high-speed manual application of tickets where careful handling is not particularly possible, and for application of the tickets to soft, yieldable merchandise or merchandise packages. The glue is ordinarily quite hard and solid at normal room temperatures, but is prepared for use in present methods by melting it to liquid form in a heated pot, from which it is applied to merchandise tickets or the like by dipping a brush or other applicator into the pot and then daubing the glue on to the ticket, either manually or by some mechanical means. These methods are subject to several substantial disadvantages. First, they require a substantial time period to melt the pot of glue, so that no apparatus dependent thereon can be readied for operation in a conventionally short time. Second, the glue, or its volatile components, vaporize and pass ofi as fumes from the hot glue, with the result that the glue in the pot gradually solidifies and becomes unusable when heated for extended periods, so that large amounts of glue are commonly wasted. Third, the fumes from the hot glue condense and solidify on nearby objects, constituting a messy nuisance, and, if the applicator is a mechanical device, tending to foul the operation of the device so that it requires frequent and difficult cleaning. Fourth, it is difficult by these methods to apply glue solely to a predetermined portion of an object in a predetermined pattern, so that if, for example, the merchandise ticket consists of a base portion to be adhered and one or more perforated sections which may be torn off, the base portion may be inadequately adhered and the perforated sections adhered. Fifth, it is difficult in these methods to regulate closely the amount of glue applied. A thin coat of glue makes the best bond, while a thick coat will make a poorer bond, and excess glue may be squeezed out from the edges of the ticket when it is pressed into place.

Accordingly, the principal objects of the present invention are the provision of a method of applying hot-melt glue which overcomes all of the above enumerated disadvantages of prior methods, in that it permits the use of apparatus which may be readied for use with extreme rapidity, which greatly reduces wastage of glue, which largely eliminates the fouling of nearby objects by glue vapor, which permits application of glue in closely defined areas and patterns, and which permits close regulation of thickness of the glue film applied.

To this end, the invention may be summarized as consisting of the successive steps of first heating a transfer bar to a temperature sufficiently high to melt said glue when applied to said glue in its normal solid form, said transfer bar having an applicator face of the area and pattern in which it is desired to apply glue to an object, then pressing said applicator face against said solid glue whereby the former acquires a film of liquid glue, then pressing said applicator face against said object to transfer said glue film to said object.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawings, wherein;

FIG. 1 is a diagrammatic view illustrating the various steps of the process of applying hot-melt glue embodying the present invention;

FIG. 2 is a view similar to FIG. 1, illustrating a slight modification of the process,

FIG. 3 is an enlarged, fragmentary side elevational view of the transfer bar shown in H6. 1, and

FIG. 4 is an enlarged face view of the applicator face of the transfer bar shown in FIG. 1.

Like reference numerals apply to similar parts throughout the several views. The numeral 2 applies to a block of hot-melt glue, which it will be understood is quite hard and solid at room temperature, carried by a suitable support 4. The numeral 6 applies to a merchandise inventory control ticket or other object to which the glue is to be applied, carried by a suitable support 8. The numeral 10 applies to a transfer bar, formed of metal or other suitable material, said transfer bar having an applicator face 12 of a size and shape corresponding to the pattern of the glue it may be desired to apply to ticket 6. Said applicator face may, as shown, be divided into a larger number of separate areas 14 (see FIGS. 3 and 4) by grooves 16 formed in said face. It is usually important that said grooves be sufficiently wide that they are not likely to become completely filled with residual glue remaining in the applicator face during performance of the process, and that said grooves be vented to the atmosphere through faces of the bar other than the applicator face, as shown.

The process forming the subject matter of the present invention comprises the following steps: First, transfer bar 10 is heated by any suitable means, such as electric heater coil 18 surrounding said bar and connected to a source of electrical power, to elevate applicator face 12 thereof to a temperature sufficiently high to melt glue 2. Second, applicator face 12 of bar 10 is pressed momentarily against face of glue block 2, as shown in position A of the transfer bar, whereby a small amount of glue at the surface of said block is melted and adheres to face 12 as a liquid film. Third, applicator face 12 is pressed against ticket 6, or any other object to which it may be desired to apply glue, as shown at position B of the transfer bar, whereby to transfer the film of glue to said ticket. The ticket is then ready for immediate use, and must of course be adhered, before the glue cools and dries.

The process as thus far described has several advantages. The transfer bar may be heated rapidly, much more rapidly than a pot of glue can be melted, so that an apparatus utilizing the present method can be readied for use in a fraction of the time heretofore required. Substantially only the amount of glue required for each application is melted at one time, so that the entire supply of glue is not subject to vaporization and consequent thickening by being kept constantly in a heated liquid state. For the same reason, nearby machine parts or other objects are not subject to be fouled by condensing glue vapor to any appreciable extent, and so do not require cleaning as frequently as before. The glue is applied to ticket 6 in an accurately controlled pattern, which may be important in many circumstances, for example, when a ticket may consist of two or more sections, some to be adhered and some not.

The process also permits close control of the amount of glue, or thickness of the glue film, applied to each ticket 6, it being understood that a thin film of glue generally provides the best bond and is therefore to be desired. Primarily, this control is provided by regulation of the temperature of the transfer bar, as for example, by thermostatic control of heater coil 18. Generally, a higher bar temperature will melt the glue of block 2 to a more liquid state, with less surface tension, than a lower bar temperature, so that a thinner film of glue adheres to the applicator face of said bar. Thus, the process may be said to include the initial step of regulating the bar temperature to provide a glue film of the desired thickness, and this temperature may vary with the characteristics of the particular glue used. Secondarily, control of film thickness is provided by the grooves 16 formed in the applicator face of the transfer bar. If the transfer bar carries more glue than desirable to ticket 6, said grooves provide zones or pockets into which the excess glue may escape as face 12 is pressed against ticket 6, so that at least portions of the glue area (those portions corresponding to areas 14 of face 12), will have a glue film of the desired thickness. The pressure with which face 12 is pressed against ticket 6 is also a determining factor affecting the film thickness on these areas. In this connection, the formation of grooves 16 of a size not likely to be completely clogged by residual glue, at least in reasonably extended periods of use, and the venting thereof to the atmosphere through bar surfaces other than face 12, is quite important in that this prevents the buildup of air pressure in said grooves which would inhibit the flow of excess glue thereinto. These features also have the additional function of admitting air over the glue film, tending to defeat the vacuum" which otherwise would tend to hold the ticket against face 12 as the transfer bar is lifted therefrom, even when the glue is quite fluid.

TI-Ie division of applicator face 12 into small areas 14 by grooves 16 also has valuable functions even when only the optimum amount of glue is picked up thereby from glue block 2. This optimum amount may be defined as just enough glue to coat areas 14, with no appreciable excess to be squeezed into the grooves when the transfer bar is pressed against ticket 6. Under these circumstances, grooves 16 have the functions of, first, providing passages for the circulation of air between the ticket and the object to which it is adhered after the ticket has been applied, thereby promoting faster drying of the glue, second of providing passages for the escape of air which otherwise might be trapped between the ticket and the object in the form of bubbles", in the area of which there would of course be no adhesion, and third of economizing in the amount of glue used, with no appreciable loss of bonding efficiency. In this connection, it will be noted that areas 14 may be of any desired size, and that if pick-up of only the optimum amount of glue by the transfer bar can be maintained, areas 14 may be as small and closely spaced as the projections" of a half-tone photographic printing plate.

The steps of the process thus far described, with relation to the movement of the transfer bar, could obviously be performed either manually, or by any suitable mechanical means, not shown. When performed by mechanical means in which transfer bar has a fixed path of movement, it will be necessary to feed the glue 2 so that it will always present a usable surface to the transfer bar, despite the fact that the body of glue is gradually consumed. This may be done, for example, by elevating glue support 4 gradually by automatic means or by transporting a tape coated with glue across support 4, or other means. However, these are apparatus considerations not pertinent to the process concept claimed. When the process is performed by mechanical means, such as a self-contained mechanism to which solid hot-melt glue and tickets 6 are fed automatically, it may also be desirable that the process steps be performed in a fixed cyclical sequence, such for example, that one ticket with glue properly applied thereto is delivered each time an operating handle is pressed. That is, each time a cycle is initiated, it will be completed, though not repeated until the operating handle is again pressed. In connection with this type of operation, certain variations of the process are pertinent. For example, as diagrammed in FIG. 1, transfer bar 10 may be provided with a neutral or rest position as indicated at C in which it is not in engagement either with glue block 2 or ticket 6. The cycle of movement of the transfer bar is first from position C to position A, then to position B, and finally back to rest at position C. This cycle has the advantage that any ticket 6 to which glue has been applied is immediately available for use, which may be important if, as is often the case, the tickets are numbered in sequence, so that there may be virtually any time delay between successive cycles. How-- ever, if there are substantial time lapses between cycles, residual glue on face 12 of the transfer bar may vaporize, thicken and solidify, necessitating frequent cleaning. In FIG. 2, the transfer bar also has a neutral position at which it comes to rest after completion of each cycle, but this neutral position is identical to position B, against ticket 6, so that the full cycle of movement consists of only two motions, first from from position B to position A, then back to position B. In this cycle, the ticket 6 under the applicator bar is of course not immediately available for use, but is has the advantage that the glue trapped between the transfer bar and the ticket is largely shielded from the air, and hence remains fluid for much longer periods than it would if exposed to air, as in FIG. 1, durin time lapses between successive cycles. Thus the cycle of FI 2 permits much longer periods of time between successive cycles of operation, with greatly reduced fouling of the transfer bar applicator face by solidified residual glue.

While I have shown and described certain specific embodiments of my invention process, it will be readily apparent that many minor modifications thereof could be made without departing from the spirit of the invention as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent l. A process for applying hot-melt glue to an object comprising the successive steps of:

a. heating a transfer bar having a glue applicator face to a temperature sufi'iciently high to melt said glue when pressed against hot-melt glue in its solid form,

b. moving said transfer bar relatively to a surface of solid, hot-melt glue to press the applicator face of said bar and said surface of solid, hot-melt glue together whereby said glue surface is melted and a portion thereof adheres to said applicator face as a liquid film, and

moving said applicator bar relatively to said object to press said applicator face and said object together, whereby said film of liquid glue is transferred to said object.

2. A process as recited in claim I for applying said glue to said object in a predetermined area pattern, and including the additional initial step of forming the applicator face of said transfer bar to correspond to the desired area pattern.

3. A process as recited in claim I with the additional initial step of regulating the temperature of said transfer bar whereby to vary the thickness of the liquid glue film acquired by said applicator face form said surface of solid, hot-melt glue, higher bar temperatures reducing the surface tension of said liquid glue and hence reducing the thickness of said film.

4. A process as recited in claim 1 with the additional initial step of dividing the applicator face of said transfer bar into smaller component areas by forming grooves in said bar, said grooves opening through the applicator face thereof.

5. A process as recited in claim 4 with the additional step of venting said grooves to the atmosphere through surfaces of said applicator bar other than the applicator face thereof.

6. A process as recited in claim 1 wherein the movements of said transfer bar relative to said glue surface and said object are performed in a fixed cyclic sequence, and wherein said transfer bar is provided with a neutral position not in engagement either with said solid hot-melt glue or with said object, the sequential cycle of movement of said transfer bar beginning and ending with said bar in said neutral position.

7. A process as recited in claim I wherein the movements of said transfer bar relative to said glue surface and said object are performed in a fixed cyclical sequence, said cyclical sequence beginning and ending with the applicator face of said transfer bar pressed against said object.

Claims

2. A process as recited in claim 1 for applying said glue to said object in a predetermined area pattern, and including the additional initial step of forming the applicator face of said transfer bar to correspond to the desired area pattern.
3. A process as recited in claim 1 with the additional initial step of regulating the temperature of said transfer bar wherEby to vary the thickness of the liquid glue film acquired by said applicator face form said surface of solid, hot-melt glue, higher bar temperatures reducing the surface tension of said liquid glue and hence reducing the thickness of said film.
4. A process as recited in claim 1 with the additional initial step of dividing the applicator face of said transfer bar into smaller component areas by forming grooves in said bar, said grooves opening through the applicator face thereof.
5. A process as recited in claim 4 with the additional step of venting said grooves to the atmosphere through surfaces of said applicator bar other than the applicator face thereof.
6. A process as recited in claim 1 wherein the movements of said transfer bar relative to said glue surface and said object are performed in a fixed cyclic sequence, and wherein said transfer bar is provided with a neutral position not in engagement either with said solid hot-melt glue or with said object, the sequential cycle of movement of said transfer bar beginning and ending with said bar in said neutral position.
7. A process as recited in claim 1 wherein the movements of said transfer bar relative to said glue surface and said object are performed in a fixed cyclical sequence, said cyclical sequence beginning and ending with the applicator face of said transfer bar pressed against said object.