US 3293765 A
Description (OCR text may contain errors)
Dec. 27, 1966 R. WINKLER ETAL METHOD AND APPARATUS FOR DRYING THE ADHESIVE ON CLOSING FLAPS OF FLAT-BAGS AND ENVELOPES AND THE LIKE 2 Sheets-Sheet 1 Filed Aug. 4, 1964 L o R r o o o L O EL Q 0k. w -hUIQ d 5 .l. D Q 6 t ill. 7, QQQ w A c 2 w s h V H W m w DIMEPE 2 R. WINKLER ETAL METHOD AND APPARATUS FOR DRYING THE ADHESIVE ON CLOSING FLAPS 0F FLAT-BAGS AND ENVELOPES AND THE LIKE Filed Aug. 4, 1964 Dec. 2 7, 1966 United States Patent Ofiice 3,293,765 Patented Dec. 27, 1966 3,293,765 METHOD AND APPARATUS FOR DRYING THE ADHESIVE ON CLOSING FLAPS F FLAT=BAGS AND ENVELOPES AND THE LIKE Richard Winkler, Burgermeister-Winkl Strasse, Rengsdorf uber Neuwied am Rhein, Germany, and Kurt Diinnebier, Am Birkenhang, Glatlbach, Germany Filed Aug. 4, 1964, Ser. No. 387,415 Claims priority, application Germany, Aug. 17, 1963, W 35,112 14 Claims. (Cl. 341) The drying of the adhesive on paper or the like sheet material, particularly on the closing flaps of flat-bags, envelopes or the like (hereinafter termed only flat-bags) hitherto required a comparatively long time and long drying paths and so prevented a rise in the output of the machines for producing these fiat bags. In addition, the expenditure of energy for the heating of the air displaced by blowers and generally used for the drying, is substantially twice as high as the energy needed for the drive of the machine, because of the inevitable heat losses.
Attempts have already been made to dry the adhesive on the closing flap with infrared rays in a shorter time and over shorter paths. This was also successful up to a certain extent. The intensity of the drying is, however, limited by the blistering of the solvent in the adhesive with excessive heating and by the curling up of the paper during the drying of the strips of adhesive applied only at the margin. Admittedly the power re quirements for infrared drying are only about equal to the driving power for the machine. But infrared drying in the production of fiat-bags involves a great risk of fire because, in the event of a sudden stopping of the machine as a result of disturbances which can never be completely avoided, the paper under the infrared radiators, which continue to glow for a long time, catches fire or at least becomes charred. It is true that the infrared radiators may be automatically swung out on stopping the machine, but this means a further complication of the installation.
The object of the invention is to overcome the said disadvantages and to increase the drying capacity of the machines with a simultaneous reduction in the power consumption for drying. This object of the invention is achieved by drying the adhesive, which may be of any suitable type and is hereinafter called gum, applied to the closing flaps, by means of the heat generated in this adhesive itself in a high-frequency electric field. The energy losses in high-frequency drying are at a minimum in comparison with the above-mentioned types of drying so that, with the same conditions otherwise in an envelope machine for drying the closing-lap gum, there is a ratio of about 12 kw. for the drying with a hot-air blast, -6 kw. for drying with infrared radiators 22.5 kw. for high-frequency drying.
In practice, the high-frequency drying is carried out in such a manner that the freshly gummed closing flaps of the fiat bags travel under or over two or more rodshaped electrodes at the conveying speeds existing in the machine. Between the electrodes there is generated an electric field of high frequency which becomes concentrated in the moist layer of adhesive which is a good conductor, and to some extent also in the moist paper, and heats and dries both from the inside. The path of travel of the parts to be dried is substantially parallel with the longitudinal direction of the electrodes.
According to another embodiment, the freshly gummed closing flaps to be dried are conveyed through the interior of a slotted waveguide, in the longitudinal direction of this waveguide in which there is a high-frequency electric field which extends perpendicularly to the surface of the paper. In this case the effect is the same as in the first case.
Flat bags conveyed individually through the machine are preferably held flat at the closing flaps to be dried, on a conveyor belt of a material which does not convert the high-frequency electrical energy into heat in itself, for example Teflon, i.e. a fluorocarbon resin of the character hereinafter more fully described. If the machine stops, there is no danger of the paper burning even if the highfrequency installation is switched on.
Preferably mounted to one side of a fiat-bag carrier is a high-frequency generator, the output terminals of which carry, on holders, rod electrodes which are substantially parallel to the direction of travel of the carrier and which produce between the and substantially parallel to the surface of the paper, a high-frequency electric field. If the gumming of the closing flaps of the flat bags is relatively wide, the rod electrodes, which are parallel with one another and spaced at an appropriate distance in relation to each other, may be arranged obliquely in relation to the direction of travel of the flat-bag carrier which then brings the zones of the wide gumming successively to the points where the field has its maximum effect and causes drying step-by-step.
In the second embodiment, high-frequency electric voltage is preferably produced by a magnetron in a waveguide of brass or the like consisting of two parallel ilnes, the lines being divided into an upper and a lower pair by a slit; the lower pair may be constructed in the form of vacuum passages. The one end of the waveguide is connected in known manner to a water load, which may contribute several advantages, such as elimination of reflection of the electric field and absorption of the unused energy.
A conveyor belt, which is perforated, is preferably provided to support the closing flaps of the flat bags conveyed along the electrodes or through the waveguides for the high-frequency field; suction means for attracting and holding the closing flaps on the conveyor belt are then provided below the conveyor belt.
The path of travel of the flat bags to be dried may equally well be in the form of an are or a curve and the electrodes or waveguides are then adapted to this shape.
The embodiments of the new method, with the devices appropriate thereto, are illustrated purely diagrammatically in the accompanying drawings. In these:
FIGURE 1 is a plan view of an arrangement of rod electrodes and conveying means for the drying of the closing flaps of fiat bags with a single strip of adhesive;
FIGURE 1A shows an arrangement in which a plurality of flat bags, having relatively wide gummed portions, are disposed on a conveyor belt above which there is mounted a pair of longitudinally extending electrodes inclined at a small angle to the direction of travel of the belt so that all portions of the gummed areas are exposed to an electric field while the flaps are subjected to a suction action;
FIGURE 2 is a vertical section through the arrangement taken along the line IIII of FIGURE 1;
FIGURE 3 is a vertical section through the arrangement taken along the line III-III of FIGURE 2, with the vacuum passage omitted;
FIGURE 4 is a plan view of an arrangement of waveguides and conveyor means for the drying of self-adhesive fiat bags with two strips of adhesive;
FIGURE 5 is a vertical section through the arrangement shown in FIGURE 4, taken along the line V-V of the latter, and
FIGURE 6 is a vertical section through the arrangement shown in FIGURE 5, taken along the line VI-VI of the latter.
According to FIGURES l to 3, the two rod-shaped electrodes 1 and 2 are mounted at a distance of a few millimeters above a conveyor belt 3 which runs over rollers 4, rotating in the direction of the arrows shown in FIGURE 2, at the conveying speed of the machine. Each of the two electrodes 1 and 2 comprises a holder 5 and 6, which are secured by bolts or screws 7 to links 8 and 9 respectively. The links 8 and 9 are each connected by screws 10 to one of the output terminals 11 and 12 of an electric field high-frequency generator designated by 13. The spacing of the eelctrodes 1 and 2 apart from each other and from the conveyor belt 3 can be adjusted as desired as a result of the slots in the pars 5, 6, 8 and 9, the spacing of the electrodes being preferably adjusted to a desired fraction of the wave length of the electric field.
The conveyor belt 3 is perforated, as shown at 14 in FIG. 1, these perforations extending throughout the length of the belt. Below the upper run of the conveyor belt 3 there is a vacuum chamber 15 which is provided with a certain reduced pressure by means of connections through a line 15a with an exhauster, not shown. The closing flaps of the flat-bags 16 are sucked tightly against the surface of the conveyor belt by the action of the vacuum chamber, with the fresh gumming 17 exposed.
The flat-bags 16, the large horizontally extending portions of which are held by a carrier or conveyor means, shown schematically in FIG. 2, and designated 3a therein, included in the flat-bag machine, after having their closing flaps gummed by conventional means (not shown), pass with their freely projecting closing flaps over the conveyor belt 3. These closing flaps are moved by the conveyors under the two electrodes 1 and 2 through the electric field created between the latter. As a result, the paper and gumming become heated and the gumming dries. If desired, the carrier or conveyor means 3a may be upper and lower conveyor belts having their bag conveying runs pressed against each other and the interposed bags being advanced.
If the conveying speed of the parts to be dried is only slow, while the length of the adhesive application across the conveying direction is great, as in the case of overlapped gummed envelope blanks having gummed surfaces extending lengthwise across the conveyor belt 3, with or without the second conveyor belt mentioned, for example, then the electrodes 1 and 2, although parallel with one another, are preferably arranged obliquely in relation to the conveying direction, over the gummed areas, so that the drying begins at one side and is car- :ried over to the other side as the blanks are advanced. This is illustrated schematically in FIG. 1A in which the electrodes 1a and 2a are disposed obliquely to the direction of travel of belt 31) which is perforated and subjected to the vacuum action in the manner shown in FIG. 2. In this use of the invention the belt 3!) may serve to support and convey relatively wide gummed areas of the flat-bags 16a while the main body portions of the fiatbags are conveyed on an extension of conveyor means included in the flat-bag machine, such as that indicated at 3a in FIG. 1.
In FIGURES 4 to 6, 21 is a waveguide of brass or the like. High-frequency electric voltage is supplied to it, at the end designated by M, for example by a magne tron. The end designated by W is connected to a waterload having advantages of the character previously stated. This arrangement is known per se. In its major dimension, the waveguide is in the form of two parallel lines 22, 23. It is divided by a slit 24 for the passage of the closing flaps to be dried, between an upper part 22, 23 and a lower part 22', 23'. The two parallel lines are connected to one another by bends 25, 25.
A conveyor belt 27 with perforations 28, which passes around two rollers 26 rotating in the direction of the arrows, is arranged to have its upper run pass through the slit 24 and serves to support the end portions of flatbags 30 with self-adhesive gumming 31 (only mentioned by way of example). The main body portions of the fiatbag 30 may be suitably supported and conveyed by carrier or conveyor means similar to that designated 3a in FIG. 2. The lower part 22 23' of the waveguide is connected in a suitable way with suction means to provide a vacuum for holding down the closing flaps on the conveyor belt 27. Internal walls designated 22a and 23a are provided vertically in the region indicated in FIG. 4 for enabling suction to be created within the parts 22' and 23 of the waveguide. Suction for this purpose is created by a connection 22'b extending from part 22 of the waveguide to a suitable vacuum producing source.
If the waveguides 21 to 23 receives high-frequency electric oscillations from the magnetron, an electric field prevails in its interior. Electrical energy is converted directly into heat in the paper or the gumming of the flatbags which are moved longitudinally through the portion of the waveguide that is divided by the slit 24, and so the gumming is dried.
Both the examples of the method described can be used for the drying of dextrin, latex and other known adhesives. The conveyor belt 3 or 27 and the vacuum passage 15 must consist of a material which does not concentrate the electrical energy in itself in a high-frequency electric field and convert it into heat, for example fiuorocarbon resins, such as polytetrafiuoroethylene with or without propylene groups, available under the trade mark Teflon.
The invention is not restricted to the examples of embodiments illustrated. The path of travel of the fiatbags to be dried may, for example, be circular if the flat-bags with exposed closing flaps are held on the circumference of a drum by means of a belt. This arrangement has the advantage that the closing flaps are stiffened as a result of the curvature so that the conveyor belt 3 or 27 can be omitted. Furtheremore, more than two electrodes 1 and 2 may be used or, when drying in the interior of a waveguide, this waveguide may be arranged in only one line or in more than two parallel lines.
Other modifications or embodiments of the constructions disclosed may be made within the scope of the appended claims.
What is claimed is:
1. A method of drying moist gum on the closure flaps of fiat-bags, envelopes or the like during their passage through a machine for making the same, comprising advancing the gummed flaps along a path adjacent to at least two spaced, electrodes which extend substantially in the conveying direction and between which there is produced a high-frequency electric field, and applying suction to the gummed flaps to maintain them in fiat condition against a surface on which they are being advanced along said path.
2. A method according to claim 1 in which the electrodes are rod-shaped and the electric field is directed substantially parallel to the surface of the sheet material.
3. A method according to claim 1 wherein the gummed flaps are advanced through a slit formed in a waveguide to provide portions arranged above and below the path of travel of the gummed flaps, and substantially parallel with the longitudinal direction of the active portion of the waveguide, thereby serving to direct a high-frequency electric field perpendicular to the surface of the gummed flaps.
4. An apparatus for drying moist gum on the closure flaps of flat-bags, envelopes or the like which comprises: means for conveying the gummed flaps along a predetermined path, rod-shaped electrodes mounted at a short distance from and substantially parallel with the path of travel of the gummed flaps, a high-frequency generator connected with said electrodes adapted to create a highfrequency electric field between the electrodes which is directed substantially parallel with the surface and transversely to the direction of travel of the gummed flaps, carrier means for the main body of the flat-bags, which is movable at the conveying speed of said conveying means for supporting the gummed flaps, and suction means cooperating lwith said conveying means to hold the gummed parts smoothly thereon.
'5. An apparatus according to claim 4 in which said conveying means comprises a perforated conveyor belt.
6. An apparatus according to claim 4 in which the conveying means and the suction means are formed of materials which are not affected 'by the electric field.
'7. An apparatus according to claim 4 characterized in that the rod electrodes are parallel with one another and are arranged obliquely in relation to the direction of travel of the flat-bags so that successive portions of wide gummed areas come successively to the region in which the field has the strongest action.
8. An apparatus for drying moist gum on the closure flaps of flat-bags which comprises: means for conveying successive fiat-bags having said closure flaps with moist gum thereon along a predetermined path, a waveguide which is fed with high-frequency electromagnetic energy mounted parallel with the path of travel of the flat-bags, said waveguide being provided with an elongated slit, said means for conveying the flat-bags being arranged to carry their gummed flaps through said slit and along the region in Which the high-frequency electric field is established in the interior of the waveguide and directed substantially across the entire width of the gummed flaps as the latter pass along said slit in the waveguide, and means for creating suction in the part of said waveguide below said slit to retain the gummed flaps against the conveying means.
' in that one end of the waveguide is connected to a water load.
11. An apparatus according to claim 8 in which said conveying means comprises two separate carriers which are movable at the same conveying speed, one of said carriers supporting the gummed parts thereof, and said suction means cooperating with said one of the carriers to hold the gummed parts flat on the latter.
12. An apparatus according to claim 11 in which said one of the carriers comprises a perforated conveyor belt.
13. An apparatus according to claim 11 wherein said one of the carriers and the suction means are formed of materials which are not heated by the electric field.
14. An apparatus according to claim 11 characterized in that said one of the carriers is arranged to pass through the slit in the waveguide which is divided by this slit into an upper portion and a lower portion and the lower portion of the waveguide being connected with the means for creating suction.
References Cited by the Examiner UNITED STATES PATENTS 2,212,522 8/1940 Hart et a1. 341 X 3,082,710 3/1963 Holland 12910.81 X 3,197,601 7/1965 Wayne et al. ll910.6l X
FREDERICK L. MATTESON, JR., Primary Examiner. JOHN J. CAMBY, Examiner.