Apparatus and Method for Sealing a Web of Film in a Form, Fill, and Seal Packaging System

This invention relates to an apparatus and method for sealing two layers of a web of plastic material together. In particular, the present invention relates to an apparatus and method for forming the transverse seals in a web of film in a form, fill, and seal packaging machine.

Typically, form, fill, and seal packaging machines are utilized to package a product in flexible containers. To this end, form, fill, and seal packaging machines are utilized to seal pharmaceuticals, dairy products, wine, food stuffs, cosmetics and other products in flexible containers. The form, fill, and seal packaging machine provides an apparatus for packaging these products in an expedient manner.

In one type of form, fill, and seal packaging machine, a web of heat-sealable film is passed over a former or mandrel that forms the film into a tubular shape. To effect the tubular shape, the film is folded longitudinally and heat sealed along abutting longitudinal edges. The tubular shaped film is then passed around a tubular fill system that deposits the product to be packaged into the tubular shaped film. To create individual packages (hereinafter "bags") the web of film must be sealed across its width. These "transverse seals" function as a seal to form a pouch in the web of film for receiving the material to be packaged, and seal the filled end of a previously filled pouch. After the transverse seals are created, the web may then be severed into an individual bag.

The two usual methods of creating the transverse seals in a web of film are impulse sealing and constant hot bar sealing. Impulse sealing is a technique through which the energy required to heat seal the film together is delivered electrically in precisely measured pulsed charges. Usually, the measured electrical charge is pulsed through a ribbon of resistant metallic material for a predetermined time while the two layers of film are clamped together by jaws in intimate juxtaposition. The energy of the impulse sealer causes the film to soften and bond together. After the film is melted together, it must be cooled to a crystalline condition before the jaws may be opened or the film may separate.

Although the impulse system is effective for creating the transverse seals in a web of film, it requires a great deal of maintenance and utilizes certain consumable components. Accordingly, the production process must be periodically interrupted so that the consumable components may be replaced. One such consumable component is the ribbon element which has a relatively short life and must be replaced at regular intervals. The ribbon elements also include covers--the covers ensure that the melted film does not adhere to the ribbon element--that also have a relatively short life and must be constantly replaced.

In a production machine, replacing and changing these consumable elements can be a costly nuisance. Moreover, interruption of the form, fill, and seal procedure for routine maintenance is especially costly and time consuming in the case of an aseptic packaging system. Interruption of an aseptic production system not only means production interruption, but also necessitates the time consuming process of resterilization of the work area prior to restarting production.

Another method of creating the transverse seals in a form, fill, and seal packaging machine is to utilize a static or hot bar system. The hot bar system utilizes a sealing bar heated to an appropriate temperature by an electric cartridge heater. The sealing bar is then maintained at this temperature by the cartridge heater. The hot bar system suffers two major drawbacks. Because the sealing bar is constantly heated, it is difficult to precisely control the amount of energy, i.e. BTUs, that flow into the web of film while the layers of the web of film are in intimate contact. This is important because the portions of the film that are melted to create the transverse seals must be subsequently cooled to the point of crystallization before the film may be released and a new set of transverse seals created. Moreover, due to the constant heat, it is not possible to release the web of film, after creating the transverse seals, from the sealing jaws without the addition of some type of consumable or replaceable release element or the use of a slip arrangement.

Other methods of sealing a web of film in a form, fill, and seal packaging machine have been utilized, including ultrasonic welding, heated gas, and radiofrequency welding. While in special situations these techniques may be preferred, these methods of creating transverse seals in a web of film to create bags are expensive and slow.

Thus, there is a need for an apparatus and method for creating transverse seals in a form, fill, and seal packaging machine that overcomes the disadvantages of the prior art.

The present invention provides a method and apparatus for forming the transverse seals in a web of film in a form, fill, and seal packaging machine. The apparatus includes a heating member that heats a portion of the web of film to create the transverse seals. Located on an opposite side of the web of film is a cooling member that functions to cool the heating member and melted portions of film. The heating member includes a hot bar, with film contact surfaces, and means for heating the hot bar. The cooling member includes a cold bar, with film contact surfaces, and means for cooling the cold bar. The cold bar and hot bar may have corresponding film contact surfaces.

The hot bar and means for heating cooperate so that the hot bar is disengaged from the means for heating when it contacts the film surface. Therefore, the hot bar contains a fixed amount of thermal energy. The hot bar may include channels that are filled with a phase change material.

The hot bar is heated to approximately a temperature equal to the softening point of the film. The cold is maintained at a sufficient temperature so that the number of BTU's loaded into the hot bar will melt the film and then the film will be cooled to a crystallized condition. Preferably the bar is maintained at 50.degree.-80.degree. F.

The method of creating the transverse seals entails heating a portion of the web of film sufficiently so that it melts. The film is then cooled by the cooling means.

The cooling member may include a hydraulically accuated knife.

The hot bar may include a raised projection having a capability of more rapid conductivity than the surrounding heat seal surface. The cold bar may include the opposing resilient pressure pad. The hot bar would sever the web of film and heat seal simultaneously.

Accordingly, an advantage of the present invention is that it provides an apparatus and method for melting a portion of a web of film to seal the web together, and then cooling the web of film so that the film crystallizes at the melted portion.

Another advantage of the present invention is that it provides a heat sealer that melts a portion of the web of film, but is not heated while it is in contact with the web of film.

A further advantage of the present invention is that it provides a cooling member that cools the heat sealer as the heat sealer contacts the web of film.

Still another advantage of the present invention is that it provides a hot bar that has two film contact surfaces and a cold bar that has two film contact surfaces that correspond to the surfaces of the hot bar.

Moreover, an advantage of the present invention is that it provides a cold bar including channels through which a cooling medium may flow.

A still further advantage of the present invention is that the hot bar may simultaneously sever and seal the web of film.

Another advantage of the present invention is that it provides a hot bar that is hollow and contains a phase change material.

A further advantage of the present invention is that it provides a method for introducing a predetermined amount of energy, i.e. BTUs, into a web of film and then removing the energy from the web of film so that the web of film crystallizes.

Moreover, an advantage of the present invention is that it provides a method of heating a web of film with a hot bar, and cooling the hot bar and the heated portion of the web of film to crystallize the film.

A still further advantage of the present invention is that it provides a method of sealing a web of film together utilizing a heat sealer heated to a temperature sufficient so that momentary contact with the film creates a molten condition in the specific polymeric structure being utilized.

Another advantage of the present invention is that it provides a cutting member located between the two surfaces of the cooling means.

A further advantage of the present invention is that it provides a machine for forming the transverse seals in a web of film in a form, fill, and seal packaging machine utilizing heating and cooling means.

Moreover, another advantage of the present invention is that it provides an apparatus for forming the transverse seals in an aseptic form, fill, and seal packaging machine.

Additional features and advantages are described in, and will be apparent from, the Detailed Description of the Presently Preferred Embodiments and from the drawings.

FIG. 1 illustrates a cross-sectional view of a preferred embodiment of the sealing apparatus of the present invention.

FIG. 2 illustrates a cross-sectional view of the sealing apparatus of FIG. 1 sealing a web of film.

FIG. 3 illustrates a top elevational view of the hot bar of the sealing apparatus of FIG. 1.

FIG. 4 illustrates a top elevational view of the cold bar of the sealing apparatus of FIG. 1.

FIG. 5 illustrates a cross-sectional view of another preferred embodiment of the sealing apparatus of the present invention.

FIG. 6 illustrates a cross-sectional view of the sealing apparatus of FIG. 5 sealing a web of film.

FIG. 7 illustrates a top elevational view of the hot bar of the sealing apparatus of FIG. 5.

FIG. 8 illustrates a top elevation view of the cold bar of the sealing apparatus of FIG. 5.

Referring to FIG. 1, the sealing apparatus 10 of the present invention is illustrated. The sealing apparatus 10 is specifically designed for use in a form, fill, and seal packaging machine to create the transverse seals in a web of film. The sealing apparatus 10 includes a first jaw 12 that includes a heating member 14 and a second jaw 16 that includes a cooling member 18. As described in detail below, the heating member 14 functions to supply a predetermined amount of heat to a web of film 20, and the cooling member 18 functions to withdraw a predetermined amount of heat from the web of film 20 and the heating member.

As illustrated, the first jaw 12 and the second jaw 16 are located on opposite sides of the web of film 20, diametric each other. The jaws 12 and 16 function to advance the web of film 20 through the sealing stage of the form, fill, and seal packaging machine. To this end, the jaws 12 and 16 are hydraulically accuated and are simultaneously raised and lowered with respect to the web of film 20. An automatic advancement of the film 20 is accomplished by intermittently closing and opening the jaws 12 and 16.

The jaws 12 and 16 include gripper members 24 and 26 respectively. As illustrated in FIG. 2, the gripper members 24 and 26 clamp the film layers 21 and 23 of the web of film 20 into intimate contact. This is essential to prevent slippage of the web of film 20 as the sealing apparatus 10 seals the film layers 21 and 23 together creating the transverse seals. To ensure that the web of film 20 is secured between the jaws 12 and 16, the first gripper member 24 includes an elastomeric bead 28 and the second gripper member 26 has a flat surface 30. The elastomeric bead 28 and flat surface 30 ensure that the web of film 20 is secured between the jaws 12 and 16, while at the same time ensuring that the web of film 20 is not cut or otherwise damaged during the form, fill and seal packaging process.

Referring now to FIG. 3, the heating member 14 is illustrated. The heating member 14 includes a hot bar 32 and a heater bar 34. The hot bar 32 includes two film contact surfaces 40 and 42. If desired, the contact surfaces 40 and 42 may be coated with a release coating to prevent the web of film 20 from sticking to the hot bar 32 after the hot bar has melted a portion of the film. The preferred coating is an alloy of Teflon and ceramic sold under the name Cerami-Pak by A&A Co., Inc., South Plainfield, N.J.

The heater bar 34 is designed to heat the hot bar 32. To this end, the heater bar 34 includes a cartridge heater 36. The cartridge heater may be any cartridge heater known in the art. A Chromolax cartridge heater purchased from Chromolax, Pittsburgh, Pa., has been found to function well in the embodiment of the invention described herein. As illustrated, the hot bar 32 is removably received within a notch portion 38 of the heater bar 34. When so received, the hot bar 32 is heated by the heater bar 34.

As illustrated in FIG. 2, when the jaws 12 and 16 move toward each other, the hot bar 32 disengages the heater bar 34. The hot bar 32 disengages the heater bar 34 due to the movement of the jaw 13. Other biasing means for disengaging the hot bar 32 from the heater bar 34 may be used. Because the hot bar 32 disengages the heater bar 34 before it contacts the web of film 20, a fixed amount of energy, i.e. BTUs, is present in the hot bar. Accordingly, after disengaging the heater bar 34, the hot bar 32 begins to lose heat energy, and therefore, the hot bar 32 begins to cool.

As the hot bar 32, and specifically the film contact surfaces 40 and 42 of the hot bar, contacts the web of film 20, a portion of the web of film 20 is melted further causing the hot bar 32 to lose heat energy. As discussed in detail below, the cooling member 18 is designed to contact a second side of the web of film 20. When the cooling member 18 contacts the web of film 20 it begins to cool the melted portion of the web of film crystallizing the film, and effecting the transverse seals. At the same time, the cooling member 18 also absorbs heat energy from the hot bar 32 cooling the hot bar.

The hot bar 32 is preferably made of a material that has good thermal conductivity. Metallic materials, specifically aluminum and alloys of copper, have been found to possess the required thermal conductivity. It has also been found that the lower the mass of the hot bar 32 the better the heat transfer from the hot bar 32 to the web of film 20 and the cooling member 18. The hot bar 32 must lose heat sufficiently fast to allow the cooling member 18 to increase the hot tack strength of the polymers of the film and initiate the crystallization process of the portion of the web of film 20. Moreover, it is necessary that the hot bar 32 is able to be quickly heated so that the heat lost by the hot bar 32 may be regained during the cycling period of the jaws 12 and 16. Preferably, the hot bar 32 may be heated within less than 50% of the cycle time and preferably within 35 to 40% of the cycle time. Approximately 50% of the cycling time is devoted to advancing the film, during the remaining 50% of the cycling time the hot bar contacts the web of film.

It has been found that if the hot bar 32 is hollow and contains cavities (not illustrated) a hot bar with improved thermal conductivity is created. It has further been found that if these cavities are filled with a material that has a phase change at or near the temperature desired for the hot bar, the thermal conductivity properties of the hot bar 32 will increase. Examples of desired phase change materials are water and mercury. During the phase change of these materials there is a release of a great amount of energy that can melt the web of film 20, at the same time causing a substantial loss of energy and therefore a drop in the temperature to the hot bar 32. Thus, the melting and crystallization of the web of film as well as the reheating of the hot bar 32 may be readily accomplished.

Referring now to FIG. 4, the cooling member 18 is illustrated. The cooling member 18 includes a cooling bar 46 having two film contact surfaces 48 and 50. Preferably, the film contact surfaces 48 and 50 correspond to the film contact surfaces 40 and 42 of the hot bar 32.

In the preferred embodiment illustrated, the film contact surfaces 48 and 50 include a resilient face 52. The resilient face may 52 be created from an elastomeric material. The preferred material for the resilient face is a silicon rubber that does not degrade at high temperatures, and is also acceptable to the FDA. The resilient face 52 provides a surface that ensures that the transverse seals are continuous across the web of film 20. Due to unavoidable peculiarities of the film contact surface 40 and 42, if a resilient material 52 is not utilized on the film contact surfaces 48 and 50, it is possible that continuous side seals will not be created across the web of film 20.

The cooling bar 46 includes channels 54. A cooling medium, such as water, is fed through the channels 54 to cool the cooling bar 46. This is especially necessary after the cooling bar 46 has absorbed heat from the web of film 20 and the hot bar 32. Because it is desirable to maintain the cooling bar 46 at approximately ambient conditions, the cooling medium is fed into the channels 54 of the cooling bar 46 at temperatures slightly below ambient conditions. Due to the heat absorbed by the cooling bar 46, the cooling medium exits the cooling bar 46 at approximately ambient temperature.

The cooling bar 46 is preferably constructed from a material with good thermal conductivity. It has been found that a metallic material, specifically, aluminum and stainless steel provide a material with good thermal conductivity.

In the embodiment illustrated in FIGS. 1-4, located between the film contact surfaces 48 and 50 of the cooling bar 46 is a hydraulically operated knife 56. The hydraulically operated knife 56 is utilized to sever the web of film 20 between the transverse seals. The knife 56 is actuated after the cooling bar 46 has cooled the web material 20 at the transverse seals sufficiently to crystallize the seals. It should be noted, that other means besides a hydraulically operated knife 56 may be utilized to sever the film 20 at the transverse seals. One such means is a hot wire (not shown) that may be located on the face of the sealing jaw and heated with impulse energy. Typically, the hot wire is heated with impulse energy to a temperature of approximately 500.degree. F. In use, the transverse seals are created, and the hot wire fires momentarily reaching a temperature 500.degree. F. and severing the web of material between the transverse seals.

A preferred method of operation of the sealing apparatus 10 of this invention is as follows. The jaws 12 and 16 move towards each other pulling a portion of the web of film 20 to the sealing station. As the jaws 12 and 16 grasp the end seams 22 of the web of film 20, the biasing means 44 bias the hot bar 32 away from the heater bar 34. While the heater bar 34 is in contact with hot bar 32, the heater bar is heated to a temperature approximately equal to the softening point of the web of film 20. As the hot bar 32 is biased away from the heater bar 34, the film contact surfaces 40 and 42 of the hot bar contact the surface of the first layer 21 of the web of film 20. The film contact surfaces 40 and 42 cause the film layers 19 and 21 of the web of film 20 to melt. As the layers 19 and 21 of the web of film 20 being the melt, they begin to stick to each other. This hot tack assists the layers of films 19 and 21 to be sealed together.

Simultaneously, as the web film 20 is melted, the cooling bar 46, and specifically film contact surfaces 48 and 50, contact the second layer 19 of the film 20 and begin to withdraw heat from the web of film 20 and the hot bar 32. This withdrawal of heat from the web of film 20 initiates crystallization of the web of film and creation of the transverse seals.

After the transverse seals have been created, the jaws 12 and 16 are urged away from each other causing the cooling bar 46 to retract and the hot bar 32 to be received by the heating means 34. Once received by the heating means 34, the hot bar 32 is again heated to a temperature approximately equal to the melting point of the web of film. At the same time, the cooling bar 46, which has been heated by the hot bar, is cooled by the cooling medium to a temperature of approximately 50.degree. to 80.degree.. The jaws 12 and 16 and thereby the sealing apparatus 10 may now recycle and create a second set of transverse seals.

Referring now to FIGS. 4-8, another embodiment of the sealing apparatus 110 of this invention is illustrated.

The sealing apparatus 110 includes a first jaw 112 that includes a heating member 114 and a second jaw 116 that includes a cooling member 118. The heating member 114 functions to supply a predetermined amount of heat to the web of film 20, and the cooling member 118 functions to withdraw a predetermined amount of heat from the web of film 20 and the heating member.

Referring specifically to FIG. 7, the heating member 114 is illustrated. The heating member includes a hot bar 132 and a heater bar 134. The hot bar 132 includes a face 135 that has a raised projection 137 and body 141. Preferably, the body 141 and face 135 are created from dissimilar heat conductive materials.

The raised projection 137 has a capability of more rapid conductivity than the surrounding surfaces 137 of the face 135. Accordingly, as illustrated in FIG. 6, when the hot bar 132 contacts the film 20, the projection 137 severs the web of film while the surrounding surfaces 139 create the transverse seals. Severing of the film is effected because of the greater conductivity of the projection 137 and because there is more pressure exerted at the contact point of the projection.

As the jaws 112 and 116 move towards each other, the hot bar 132 is biased away from the heater bar 134. Accordingly, after the hot bar 132 is biased away from the heater bar 134 it begins to lose heat.

Referring to FIG. 8, the cooling member 118 is illustrated. The cooling member includes a cooling bar 142. The cooling bar 142 includes a contoured resilient pressure pad 147 that opposes the projection 137 of the hot bar 132.

It should be understood that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the appended claims.