Heater For Sealing Carton Containers

Abstract

A heating apparatus for use with a carton forming machine for selectively heating the sealing surfaces of carton closure elements. A hot air distributor head is formed to receive the closure elements of the carton in adjacent relationship and to selectively heat portions of the closure elements by convection and radiation.

Description

This invention relates to carton forming apparatus and more particularly to heating apparatus for use with a carton forming machine for selectively heating the sealing surfaces of carton closure elements.

Cartons made from scored paper blanks coated with a heat and pressure sensitive thermoplastic substance have been used for some time for packaging fluids and other products. Milk, for example, is commonly marketed in such paper cartons.

Various types of carton forming machines have been developed, and various types of heating arrangements have been used to heat the closure elements of the cartons prior to heat sealing them together. Although these heating arrangements have served the purpose, they have not proved entirely satisfactory under all conditions of service.

For example, the use of gas heaters as described in U.S. Pat. No. 3,364,826, is adequate for unlined paper cartons. However, metallic foil lined cartons are now being used for the packaging of syrups and the like where it is necessary to prevent the deterioration of the paper in the carton or to prevent the paper from coming in contact with the contents of the container. When such foil lined cartons are used, gas heaters, such as that described in U.S. Pat. No. 3,364,826, do not perform satisfactorily because the foil located nearest to the heater is overheated and deteriorates before the portions of the carton further away from the heater are adequately heated for sealing. Thus, there is an overconcentration of heat adjacent the outer ends of the carton closure elements, and proper uniform heating of the outer surfaces of the carton closure elements and of the foil lining is not attained. This, of course, has frequently resulted in a poor seal of the carton with the concomitant leakage of its contents.

Other types of container closure heaters, such as those disclosed in U. S. Pat. Nos. 3,309,841 and 3,392,458 have been used; however, these heaters are not adapted for satisfactory use with foil-lined cartons because an excessive amount of heated air and radiation may act upon the inner foil lining of the carton so as to heat the foil to an undesirably high temperature. Thus, as in the case of a gas fired heater the inner foil may be so overheated that it melts away from the inside of the carton closure members. This, of course, results not only in a poor seal of the carton but exposes the contents of the carton directly to the paper, and if the contents are such that they react in an unfavorable manner with the paper the integrity of the carton may be destroyed and the contents thereof contaminated by portions of the paper cartons.

It is, therefore, an object of the present invention to provide an improved and efficient heater for use in carton forming machines employing metallic foil-lined paper board containers whereby predetermined sealing surfaces of the carton closure elements are properly heated to provide good seals when the heated closure elements are pressed together.

Another object of the invention is to provide a heating apparatus employing a unique hot air distributor head for selectively heating the sealing surfaces of carton closure elements by heated air convection and by radiation so that the volume of heated air required is less than that required in prior art heaters.

Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages are realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve these objects the present invention provides a heating apparatus for use with a carton forming machine for selectively heating the sealing surfaces of carton closure elements. The heating apparatus includes a hot air distributor head for heating the sealing surfaces by heated air convection and by radiation, and also includes means in operative relationship with the distributor head for positioning the head adjacent to the carton closure elements and for introducing heated air into the distributor head. The distributor head includes a first planar surface, first and second elongated hollow projections extending substantially perpendicularly and in substantially the same direction away from the first surface, each of the projections having an air flow passageway therein for passing hot air against certain of the carton sealing surfaces. A plurality of walls extend substantially perpendicularly and in substantially the same direction away from the first surface and form a substantially hour-glass like configuration. The distributor head further includes a cover positioned on the walls whereby an open-ended chamber is formed by the cover and the walls, and the walls further have apertures therein for directing heated air against surfaces of the carton closure elements.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.

In the drawings:

FIG. 1 is a vertical fragmentary section of the heating apparatus;

FIG. 2 is a top plan view of the hot air distributor head;

FIG. 3 is a bottom plan view of the distributor head;

FIG. 4 is a top plan view of the heating apparatus with certain parts removed for clarity; and

FIG. 5 is a side elevation view of the distributor head shown in FIG. 2.

With reference now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a preferred embodiment of the invention. The hot air distributor head of the invention is generally indicated by the numeral 10. Similarly, the numeral 12 generally indicates means in operative relationship with the distributor head for positioning the head adjacent to carton closure elements 14 and for introducing heated air into the distributor head.

The distributor head is illustrated in more detail in FIGS. 2-5 and includes a first planar surface 16. The distributor head is preferably made of metal having a high heat conductivity. A number of metals may be used, but an aluminum-bronze alloy, e.g., "ALUBRONZE" has been found to perform satisfactorily.

A first elongated hollow projection 18 and a second elongated hollow projection 20 extend substantially perpendicularly and in substantially the same direction away from the planar surface 16. First projection 18 has an airflow passageway 22 therein and second projection 20 has an airflow passageway 24 for passing hot air against certain of the carton sealing surfaces of closure elements 14.

A plurality of side walls 26 extend substantially perpendicularly and in substantially the same direction away from planar surface 16 and are located in continuous relationship with respect to one another to form a substantially hour-glass like configuration. As seen in FIG. 2, walls 26 are formed integral with a top wall 28 to provide an open-ended chamber 31 having a top 28 and side walls 26. In addition, the walls have apertures 32 therein which are positioned at the interior acute angle corners of the walls, and these apertures are directed upwardly and outwardly from the walls so that heated air is directed against inner corners of closure elements 14 when the carton is positioned over the distributor head.

Apertures 30 containing screws 34 or other adjustment means are provided in top wall 28 and extend across apertures 32 to adjust the flow of air through the apertures and provide the desired amount of heating of the interior surface corners of the closure members.

First and second projections 18 and 20 are preferably parallel to each other. A first baffle 36 (FIG. 2 and 5) is fastened to the top of first projection 18 by screws 38 positioned in apertures 38' and second baffle 40 is fastened to the top of second projection 20 by means of screws 42. These baffles are positioned adjacent to passageways 22 and 24, and shoulders 44 and 46 (FIG. 1) integral with first projection 18 and with second projection 20, respectively, combine with baffles 36 and 40 to direct the flow of hot air inwardly from the projections and against closure members 14 of the carton. In this way the exterior surfaces of two opposing ones of the closure members are heated as the carton is moved downwardly over distributor head 10 and as it is removed from the distributor head.

Apertures 32 are preferably located at angles of about 45.degree. with respect to top wall 28 so that heated air is directed upwardly and outwardly away from walls 26 to heat the interior corners of closure members 14 as the carton is placed over and removed from distributor head 10. Also a plurality of additional apertures 48 are provided adjacent to one of the apertures 32 and in one wall 26 for directing an additional volume of heated air against the inner surface of one closure member 14. This closure member frequently has an additional wall thickness as a result of overlapping of the paper blank forming the tubular carton. Because of this additional wall thickness, apertures 48 are used to make sure that proper heating of the interior surface of that closure member is accomplished. As a result, proper heating of the interior and exterior of closure members 14 is achieved and the bottom of the carton can be firmly sealed by pressing the closure members together at a later step in the operation as is well known to those skilled in the art.

Slanted passageways 50 and 52 are provided in fluid communication with passageway 22 and 24, respectively, to facilitate passage of hot air into passageways 22 and 24 when distributor head 10 is positioned for operation, as illustrated in FIG. 1. Furthermore, side walls 54 are fastened by screws or other conventional means 56 to opposite ends of first and second projections 18 and 20 to assist in retaining the hot air within the distributor head and to further heat closure members 14 to provide the necessary melting of the thermoplastic coating.

In accordance with the invention, means are provided in operative relationship with distributor head 10 for positioning the head adjacent to the carton closure elements and for introducing heated air into the distributor head. As here embodied, the positioning and heated air introducing means include hydraulic means for moving distributor head 10 toward and away from the cartons to be sealed and the hydraulic means include an hydraulic cylinder 58 of conventional construction having a piston 60 movable therein.

A walled chamber member for receiving heated air is located in fluid communication with distributor head 10, and the walled chamber member receives heated air and directs the heated air into the distributor head. As here embodied, the walled chamber member includes an outer shell 62 and an inner shell 64 fastened to and spaced apart from the outer shell by means of spacer elements 66 to form a heat insulating air space 68.

In accordance with the invention, means are positioned between the hydraulic cylinder and the walled chamber member for shielding the hydraulic cylinder from heat from the distributor head and from the walled chamber member. As here embodied, the shielding means include a heat shield 70 comprised of a suitable heat insulating material attached to outer shell 62 and positioned between the outer shell and hydraulic cylinder 58.

A coolant plate 72 having an essentially "U" shaped fluid flow passageway formed by passageways 74, 75, and 74' is positioned between hydraulic cylinder 58 and heat shield 70, and the "U" shaped passageway is in fluid communication with the interior 76 of the walled chamber via connections 78 and 80. Coolant plate 72 performs the dual functions of shielding hydraulic cylinder 58 from the heat in distributor head 10 and chamber 76 and of pre-heating air entering the coolant plate from a supply line 82. The air is pre-heated prior to entering heater 84, and the air is then directed through connection 80 and through shells 62 and 64 to the interior of chamber 76. The heated air then passes upwardly and into distributor head 10 to ultimately pass into and through passageways 22 and 24 and into chamber 31 and through apertures 32 and 48 to impinge upon closure elements 14 of the carton.

In order to provide stability of movement for distributor head 10 and for piston 60, a base plate 86 is provided adjacent to hydraulic cylinder 58. The base plate may preferably be fastened by conventional means (not shown) to the hydraulic cylinder, and the base plate has an aperture 88 therein for receiving piston 60 and two apertures 80 for receiving guide rods 90. Guide rods 90 are connected to coolant plate 72 by conventional means (not shown), and these rods move through apertures 89 with movement of piston 60 to stabilize the positioning of distributor head 10.

In operation of the heating apparatus of this invention, a distributor head 10 of suitable size, depending upon the size of the cartons to be operated upon, is selected. Each of the distributor heads includes a depressed area 92 (FIG. 1) in cover 28 and a bracket 94 (FIGS. 2 and 4) fastened to the cover and positioned over a portion of the depressed area for facilitating the removal and replacement of the distributor head from walled chamber 76. Thus, the desired distributor head is first placed onto the top of walled chamber 76.

When the apparatus operates in a vertical direction, as illustrated, the distributor head need not be fastened to the walled chamber; however, if the heating apparatus is to operate in other than a vertical direction the distributor head should be secured to one or both of shells 62 and 64 in a conventional manner.

The distributor head is provided with a shoulder 96 (FIG. 5) which fits down inside inner shell 64 (FIG. 1) so that shoulder 96 is in a position closely adjacent to the inside surface of shell 64. In addition, inner shell 64 is provided with a flange extension 64', and surface 98 of the distributor head rests on this flange extension when the distributor head is placed in its operating position.

With the distributor head in position, heater 84 is energized and a forced air source (not shown) is energized to provide a flow of air from line 82 into "U" shaped passageway in coolant plate 72. The air then passes out through connection 78, into heater 84, and through connection 80 into chamber 76. The air quickly fills chamber 76 and is then forced upwardly into distributor head 10.

Slanted passageways 50 and 52 enable the hot air to pass upwardly and into passageways 22 and 24 so that the air ultimately emerges from the passageways adjacent to shoulders 44 and 46 and beneath baffles 36 and 40. Simultaneously, air is forced upwardly into the central chamber 31 to heat side walls 26 and top wall 28 and where it emerges through apertures 32 and 48.

The flow of heated air, as just described, may be interrupted or continuous, and the interruptions may occur at various times in relation to the movement of the cartons and closure elements 14 with respect to distributor head 10. For example, the air could flow continuously as the distributor head is moved to a position adjacent to closure elements 14 and as the head is moved away from a position adjacent to the closure elements.

Alternately, the air could be caused to flow only during those periods of time during which the closure elements are being moved downwardly and into adjacent relationship with the distributor head. In this mode of operation, therefore, the air would cease to flow during those periods of time when the closure elements are being removed from a position adjacent to the distributor head. Still another alternative mode of operation would cause the air to flow and to impinge upon the closure elements only when the closure elements are being withdrawn from a position adjacent to the distributor head.

Although these and other timing arrangements are envisioned by the invention, the discussion herein will concern continuous flow of the air during all phases of operation of the apparatus.

With a carton forming machine as shown in U.S. Pat. No. 3,364,826, after the bottom closure elements have been pre-broken and the mandrel wheel indexed to the bottom heating station, hydraulic cylinder 58 is activated in a conventional manner to move head 10 up into adjacent relationship with the carton's closure elements 14. During this upward movement of piston 60, guide rods 90 also move in an upward direction through base plate apertures 88 to stabilize the movement of the apparatus.

Because air is continuously flowing into chamber 76 and out through passageways 22 and 24 and through apertures 32 and 48, hot air is caused to impinge upon the entire outer surfaces of the two opposed gusset closure panels 14' of the closure elements of the container as they pass by passageways 22 and 24. In addition, apertures 32 provide a continuous stream of heated air against the interior corners of the closure elements and heated air from apertures 48 impinge upon the double-walled thickness of one interior corner of a closure element.

Because the distributor head 10 is made of a highly heat conductive material, such as "ALUBRONZE," the distributor head becomes quite hot. Thus, in addition to heating the closure elements by means of forced air convection currents, the closure elements are also heated by means of radiation from the hot metal of the distributor head.

Because of the large amount of heat present in chamber 76 and in distributor head 10, the heat shielding arrangement is preferably provided to shield hydraulic cylinder 58 and its associated hydraulic system (not shown) from the heat. This is accomplished by the use of air space 68, which has an insulating effect, and is also accomplished by means of heat shield 70. Furthermore, coolant plate 72 acts to shield cylinder 58 from the heat and also serves to preheat the air entering via line 82. The absorption of heat by this incoming air reduces the amount of heat that reaches cylinder 58 and also raises the temperature of the air prior to its entering heater 84.

After the distributor head has reached its upper limit around the closure elements 14, cylinder 58 is again energized by its hydraulic system (not shown) and piston 60 is retracted, again causing the hot air to impinge upon selected surfaces of the closure elements as the distributor head is moved away from the carton. The time selected for movement of the head is set so that all necessary surfaces are uniformly heated for sealing without degradation of the metal foil liner.

Because apertures 32 are positioned at an angle of approximately 45.degree. with respect to cover 28, hot air is forced up into the uppermost corners of closure elements 14 so that the desired heating of the inner foil lining is accomplished and so that a tight seal can be obtained when the closure elements are pressed together in a later operational step, not a part of this invention. Additional apertures 48 are also important in directing an extra amount of air against the extra thickness of the closure elements adjacent to one corner of the carton. This extra thickness is frequently referred to as the fifth wall of the carton and is created by overlapping of the paper, which is necessary to form the tubular carton.

When using metallic foil lined cartons it is extremely important to carefully regulate the amount of heated air that impinges upon the interior of the closure elements so as to avoid excessive heating of the foil. This is accomplished, in part, in this invention by means of adjustment screws 34 which may be rotated to permit more or less air to flow through apertures 32 and against the interior of closure elements 14.

The substantially hour-glass shape of walls 26, as viewed in plan, is significant since it permits the heated walls 26 to be immediately adjacent to closure elements 14' which after having been prebroken have an hour-glass configuration as is well known to those skilled in the art. Thus, radiation from walls 26, in addition to hot air convection currents, acts upon the inner surfaces of the prebroken closure elements to heat the foil lining or other lining of these elements to the desired temperature.

When a different size carton is to be formed, distributor head 10 is removed by placing a tool (not shown) into depressed area 92 and under bracket 94. The distributor head is then lifted off of inner shell 64 and a different sized head is replaced.

The present invention thus provides a simple and effective heating apparatus for heating the closure elements of carton containers prior to the step of pressing the closure elements together to form a tight seal.

The invention in its broader aspects is not limited to the specific details as shown and described, and departures may be made from such details without departing from the principles of the invention and without sacrificing its chief advantages.

Claims

What is claimed is:

1. A heating apparatus for use with a carton forming machine for selectively heating sealing surfaces of carton closure elements, comprising:

a hot air distributor head for heating said sealing surfaces by heated air convection and by radiation;

means in operative relationship with said distributor head for positioning the head adjacent to said carton closure elements and for introducing heated air into the distributor head and wherein said head includes

a first planar surface;

first and second elongated hollow projections integral with and extending substantially perpendicularly and in substantially the same direction away from said first surface, each of said projections having an air flow passageway therein for passing hot air against selected carton sealing surfaces;

a plurality of walls integral with and extending substantially perpendicularly and in substantially the same direction away from said first surface and forming a substantially hour-glass like configuration between said first and second projections;

a top wall integral with said walls whereby an open-ended chamber is formed;

said walls further having apertures therein for directing heated air against surfaces of the carton closure elements; and

means in operative relationship with each of said apertures for enabling the individual adjustment of air flow therethrough.

2. A heating apparatus as in claim 1 wherein said projections are substantially parallel to each other.

3. A heating apparatus as in claim 1 wherein said walls form four interior acute angle corners and wherein said apertures are located at each of said corners.

4. A heating apparatus as in claim 3 further including a plurality of additional apertures located adjacent to one of said corners and in one of said walls for directing an additional volume of hot air against one of the carton sealing surfaces and also including a pair of sidewalls fastened to opposite ends of said first and second projections to help retain the hot air within the distributor head.

5. A heating apparatus for use with a carton forming machine for selectively heating sealing surfaces of carton closure elements, comprising:

a hot air distributor head for heating said sealing surfaces by heated air convection and by radiation;

means in operative relationship with said distributor head for positioning the head adjacent to said carton closure elements and for introducing heated air into the distributor head and wherein said head includes

a first planar surface;

first and second elongated hollow projections integral with and extending substantially perpendicularly and in substantially the same direction away from said first surface, each of said projections having an air flow passageway therein for passing hot air against selected carton sealing surfaces;

a plurality of walls integral with and extending substantially perpendicularly and in substantially the same direction away from said first surface and forming a substantially hour-glass like configuration between said first and second projections;

a top wall integral with said walls whereby an open-ended chamber is formed;

said walls further having apertures therein for directing heated air against surfaces of the carton closure elements;

hydraulic means for moving said distributor head toward and away from cartons to be sealed;

a walled chamber member for receiving heated air and in fluid communication with the distributor head for directing the heated air into the distributor head; and

means positioned between said hydraulic means and said chamber member for shielding the hydraulic means from heat from the distributor head and from the chamber member, said shielding means including

a heat shield attached to the chamber member and between the chamber member and the hydraulic means; and

a coolant plate having fluid flow passageways therein in fluid communication with the interior of the chamber member, said coolant plate positioned between the hydraulic means and the chamber member for shielding the hydraulic means from the heat in the distributor head and the chamber member and for preheating air as it passes into and through the coolant plate passageways on its way into the chamber member.

6. A heating apparatus as in claim 5 further including a heater in position for heating air as it passes from the coolant plate passageways into the chamber member.

7. A heating apparatus as in claim 6 wherein said hydraulic means include an hydraulic cylinder and a piston movable therein, said piston connected to said coolant plate, and further including a base plate having an aperture therein for slideably receiving the piston.

8. A heating apparatus as in claim 7 wherein said base plate has two additional apertures therein and wherein the apparatus further includes two guide rods connected to the coolant plate and movably located within said additional base plate apertures for stabilizing movement of the distributor head.

9. A heating apparatus as in claim 5 wherein said chamber member includes:

an outer shell; and

an inner shell fastened to and spaced apart from the outer shell to form a heat insulating air space.

10. A heating apparatus as in claim 9 wherein the distributor head fits over said chamber member and wherein the interior of said inner shell is in fluid communication with the interior of the distributor head.

11. A heating apparatus as in claim 1 further including first and second baffles positioned adjacent the passageways in said first and second projections, respectively, for directing the flow of hot air against selected carton sealing surfaces.

12. A heating apparatus as in claim 11, wherein:

said air flow passageways extend longitudinally through said projections and terminate at top surfaces of said projections;

said baffles are mounted on said top surfaces of said projections; and

said projections include shoulders formed at said top surfaces to provide inwardly extending passageways beneath said baffles for directing hot air to the carton sealing surfaces.

13. A heating apparatus as in claim 3 wherein said apertures are positioned at angles of 45.degree. with respect to said cover to direct hot air upwardly and outwardly away from said walls.