Packaging machine and packages made therewith

This invention relates to a liquid-filled tetrahedral package having a longitudinal fin seal and having a first transverse seal on one end of the package and a second transverse seal on the opposite end of the package, wherein the first and second transverse seals are substantially perpendicular to one another.

TECHNICAL FIELD

The present disclosure relates to improvements in continuous fill packaging machines and, particularly, to machines that produce liquid-filled packages and to the packages produced thereby. Generally, the packages are non-reclosable, tetrahedral-shaped containers having a central longitudinal seal and opposite transverse seals that are oriented perpendicularly to one another. Described herein are equipment and processes for forming fin-shaped seals in the longitudinal direction, which are useful in situations where an overlapping seal may be inadequate or vulnerable. Also described herein are improvements to the heated jaws that produce the transverse package seals and to the corresponding power supply system for such heated jaws. Such improvements enable the continuous production of liquid-filled containers having strong seals in both the longitudinal and transverse directions.

BACKGROUND

Machines that are designed to produce cushion-shaped, parallelepedic-shaped, or tetrahedral-shaped packages from a continuous roll or flat web of packaging material are well known in the packaging industry. Often, such packages are used to hold single servings of consumable food products. Representative items include liquids such as fruit juice and non-carbonated beverages (which may remain liquid or be subsequently flash-frozen into solids) and semi-solids, such as sour cream or other viscous sauces.

Commonly, such packaging machines are of the “form-fill-seal” variety, in which a continuous flat web of suitable packaging material (e.g., wax- or plastic-coated paper) is formed into a vertically oriented tube-like structure by means of passing the web through one or more ring-like guides or forming collars, with a longitudinal seal formed by adhesively or thermally joining the opposed longitudinal edges of the web, often in overlapping configuration.

Once a tube of packaging material is produced, the product is introduced and it is necessary to form transverse seals to create a string of connected, filled packages. Opposed sets of heated and pressure jaws compress the tube, in spaced intervals, as the tube is moved through the machine. The string of connected packages may then be separated from one another by cutting the sealed tube segments in the region of the transverse seals.

Because the transverse seals are bisected to produce individual packages, it has been found that these transverse seals are most prone to leakage. While such leakage is less problematic when the product is frozen or very viscous (such as is the case with sour cream), the leakage rate is typically unacceptable for liquid products (such as juice or other beverages). Most often, the poor transverse seal is attributable to temperature variation from one heated jaw to another. The reason for this problem in machines of this type is that the heated jaws are constantly moving along an oval or elliptical path, which makes monitoring and adjustment of the jaw temperatures difficult.

The present disclosure addresses this deficiency in currently available equipment by providing a closed-loop electrical system for powering the heated jaws that includes equipment for monitoring the temperature of the jaw faces and for adjusting the power supplied to those jaw faces in real-time. As a result, the temperature differential among the heated jaws is considerably smaller than that of previous heated jaws, which are part of an open-loop control system.

Another issue related to existing packages with an overlapping seal is that one of the cut longitudinal edges of the packaging material is exposed to the food product. When the food products are acidic in nature, such as some juices or ketchup, or when the food products are aqueous and the packaging material includes a wickable layer (e.g., paper), the food products tend to “attack” the exposed cut edge of the packaging material. As a result, the longitudinal seals become susceptible to failure. By incorporating a “fin”-type seal in place of the traditional overlap seal, the cut edges of the packaging material remain on the outside of the formed package, and a more reliable longitudinal seal is formed. Provided herein is a subassembly for forming a fin seal on a continuous-fill packaging machine.

SUMMARY

Provided herein is a liquid-filled, non-reclosable tetrahedral or pillow-shaped packaging container having a longitudinal fin seal and a pair of transverse seals. In the case of tetrahedral packages, the transverse seals are substantially perpendicular to one another. These types of packages may be preferred for many applications, because the surface area-to-volume ratio is better than for pillow-shaped packages (that is, less surface area of packaging material is needed per unit of volume). The packages may be formed of paper, film, or foil, which include a meltable layer on one side. The packages are designed to contain liquid and semi-solid food products, including beverages (such as fruit juice, sweetened beverages, and coffee flavorings); condiments (such as ketchup, mustard, and salad dressing); and viscous semi-solids (such as sour cream or mayonnaise).

Also provided herein is an apparatus for the formation of such fin seals as part of a continuous packaging and filling operation. The apparatus includes a tube-forming subassembly, a seal-heating subassembly, a seal-pressing subassembly, and a tube-conveying subassembly. In the tube-forming subassembly, the stock material is fed such that the meltable layer on one side of the stock material is positioned toward the inside of the device. Then, the longitudinal edges of the stock material are positioned through a slot that holds the respective interior sides against one another, such that the meltable layers are in contact with each other. The area adjacent to the longitudinal edges is then heated by the seal-heating subassembly to melt the meltable layer on the stock material, and the longitudinal fin seal is formed by pressing the longitudinal edges together in the seal-pressing subassembly. The tube-conveying subassembly pulls the formed tube through the apparatus and into the transverse sealing subassembly.

A third aspect of the apparatus of the present disclosure is provided in a closed-loop heated jaw system for real-time monitoring and adjustment of the temperatures of the heated jaws, as they are moving. The heated jaw system includes thermocouples that monitor the temperature of the jaw face; wireless transmitters that transmit the temperature readings to an antenna; an antenna that powers the wireless transmitters, receives the data, and transmits the data to a programmable logic controller; a pair of power rails that provide power to the heated jaws and that include a base level portion and a power-correction portion; and a programmable logic controller that controls the power supplied to the base level portion and the power-correction portion of the power rails. Using this closed-loop system, the temperature variation among the heated jaws is minimized, thereby ensuring consistent formation of strong transverse seals.

The various subassemblies described above and herein provide a continuous-fill packaging machine, particularly useful for liquid food products. The resulting packages have reliable and durable seals in both the longitudinal direction and the transverse direction.

DETAILED DESCRIPTION

Filled tetrahedron-shaped containers may be formed from a web of sheet material, such as paper stock, foil, or film, each of which has a meltable coating on at least one side. Such tetrahedral containers2are shown inFIG. 1AandFIG. 1B, which show the relative position of a longitudinal seal4, a first transverse seal6, and a second transverse seal8. The first transverse seal6and the second transverse seal8are positioned perpendicularly to one another. Typically, in production, longitudinal seal4is positioned on the back of tetrahedral container2. As shown, longitudinal seal4has a fin seal configuration (that is, the interior sides of the stock material abut, and are sealed to, one another). Alternately, longitudinal seal4may be an overlap seal, in which the stock material is lapped over itself (that is, an interior side of the stock material is secured to an exterior side of the stock material). The longitudinal seal4is off-set from the outermost edge of the transverse seal6, as shown inFIG. 1B, to ensure that both the longitudinal and transverse seals are robust. This is accomplished by having the longitudinal sealing portion of the packaging machine be off-set (preferably at a 45-degree angle, although other degrees of off-set may be used) to the transverse sealing portion of the packaging machine.

Tetrahedron-shaped containers are preferred for many applications, because of their lower surface-area-to-volume ratio, and, therefore, they will be referred to most often in this disclosure. However, it should be understood that cushion-shaped containers2′ (as shown inFIG. 1C) may also be formed according to the teachings herein by adjusting the position of sealing clamp jaws and pressure jaws, as will be readily apparent to those of skill in the art. Similarly to tetrahedral-shaped containers2, such cushion-shaped containers2′ have a longitudinal seam4′ on one side and transverse seams6′ and8′ at opposite ends.

As shown inFIG. 2, the stock material12is conveyed through a longitudinal sealing portion of the packaging machine120and then through a transverse sealing portion of the packaging machine120. The process of forming tetrahedron-shaped filled containers2begins with a roll14of pre-printed flat package stock12. The stock material12may be any suitable material, such as paper, foil, or film, which includes a meltable coating on at least one side. Representative configurations of multi-layered stock materials are shown inFIGS. 15A-15C, which will be discussed further herein.

The speed and tension of sheet material roll14is controlled by a brake mechanism16. The stock material12is supported on a suitable support member (not shown) and is delivered upwardly over a plurality of guide rolls supported by frame members secured to the machine120. The stock material12is delivered downwardly from the upper portion of the machine120through a web guide20, which ensures that the stock material12is correctly positioned in a horizontal, or transverse, direction for entry into the machine. One representative web guide assembly20is sold by Fife Corporation of Oklahoma City, Okla., although other manufacturers sell devices that function similarly.

In the longitudinal sealing portion of the packaging machine, the stock material12is conveyed through a tube-forming subassembly24, a seal-heating subassembly26, and a seal-pressing subassembly28, with the conveyance of the stock material being accomplished by a tube-conveying subassembly30. The resulting tube of stock material includes a longitudinal seal, which is preferably of the “fin”-seal type.

Once the tube of stock material is formed, the tube is conveyed into the transverse sealing portion of the packaging machine130, which is operated by a motor100. In the transverse sealing portion of the machine, transverse seals are made by the interaction of a heated jaw36(carried on a pair of chains34) with a corresponding pressure jaw38(on a pair of chains32). A second set of heated jaws and pressure jaws is oriented perpendicularly to the set shown to form transverse seals in a perpendicular direction to those formed by the first set of heated and pressure jaws. The package contents are conveyed into the packages in a continuous-fill operation through fill pipe22, which extends through the longitudinal sealing portion of the packaging machine to an area just above where the first transverse seal is formed.

Motor100is connected, via a drive belt, to one of the chains34conveying the heated jaws36. The remaining chains (including chains32and the perpendicularly oriented chains not shown) are connected to one another by a plurality of interacting gears (not shown).

The string of filled, connected packages is then either conveyed to a cutting mechanism, which separates the individual packages by bisecting the transverse seals, or gathered into a bin for transportation to an off-line cutting mechanism. Preferably, for expediency, the cutting mechanism is in-line with the filling-and-sealing operation.

The first station is a tube-forming subassembly24(shown in detail inFIGS. 4 and 5) that bends the material12, such that the longitudinal edges are aligned with one another with the interior sides of the sheet material abutting each other. This configuration forms a “fin” shape around a fill pipe22(as shown inFIG. 5), which acts as a mandrel around which the tube of stock material12is formed. (Alternately, a separate forming mandrel may be positioned over the fill pipe22, if desired.) The fill pipe22extends within the tube50of stock material and that extends to a point above the region where the transverse seals are formed. From the tube-forming subassembly24, the stock material12passes through a fin seal-heating subassembly26(shown in greater detail inFIGS. 6A-6C), where the thermoplastic coating on the stock material is melted so that a bond is formed between the adjacent, abutting edges of the stock material that make the fin.

After being heated by the seal-heating subassembly26, the longitudinal edges of the stock material are joined. The sealed stock material is then conveyed through a seal-pressing subassembly28(shown in greater detail inFIGS. 7 and 8) that applies pressure to the fin seal4to further secure the seal, resulting in the formation of a closed cylinder50(i.e., a tube). Because the tube50is formed around the fill pipe22, it should be evident that the longitudinal seal4is formed when the tube50is empty and the stock material is dry (that is, above the level of the product).

The tube-conveying mechanism30(shown in cross-section inFIG. 9) pulls the stock material through the longitudinal sealing portion200of the packaging machine120. As the tube50of sheet material is conveyed from the longitudinal sealing portion200of the packaging machine120to the transverse sealing portion of the packaging machine, the tube50is brought into contact with a fin-folding guide60, which pushes the longitudinal fin seal4against the tube50. The fin-folding guide60is made of an angularly disposed strip of steel, having a bend at the distal end thereof for contacting the fin seal. The longitudinal sealing portion200of the packaging machine is operated by a servo motor300, shown inFIG. 3. Each of these subassemblies will be discussed in more detail as follows, with respect to their respective Figures.

The stock material tube50is conveyed into the transverse sealing portion of the packaging machine120. The transverse sealing portion of the machine120is operated by a motor100, which is directly connected, via a belt, to one of the chains34, which, in turn, is connected to the other pairs of chains by a plurality of gears (not shown).

To form such transverse seals6,8, as shown inFIGS. 1A and 1B, opposed sets of heated jaws36and pressure jaws38are used. Each transverse seal is formed by a heated jaw36(shown in more detail inFIG. 12and, in an alternate form, inFIG. 13) that acts in cooperation with an unheated pressure jaw (shown in more detail inFIG. 14). For convenience, the heated jaw will be identified throughout this description as heated jaw36; however, it is to be understood that heated jaw436functions in a similar way and may be used instead of heated jaw36, as needs dictate. The heated jaws36melt the coating on the interior of the stock material12, while the pressure jaws38simultaneously push the stock material12against itself to form each transverse seal.

To this end, two sets of opposed, endless chains carrying heated jaws36and corresponding pressure jaws38at fixed locations along the chains are continuously and uniformly rotated by gears (not shown) driven by motor100. One opposed set of endless chains is represented by reference numbers32,34, while the second opposed set of chains is axially displaced perpendicularly to the first set of chains (depicted as chains33,35inFIG. 11). The second set of chains is positioned perpendicularly to the plane of the machine shown inFIG. 2and, as such, is not visible in this view. There are four chains per set, two chains on which the heated jaws are carried and two chains on which the opposing pressure jaws are carried. For ease of illustration, not all chains are shown in this Figure.

Heated jaws36, mounted on the first set of chains32, push against corresponding pressure jaws38and, in the action of pushing against one another, the jaws36,38push the food product (e.g., the liquid contents) from the area where the transverse seal8is to be made. The jaws36,38form a transverse seal below of the level of product in tube50and simultaneously advance tube50, via a pulling action, downwardly through the machine120in a continuous motion. In the production of tetrahedral packages, heated jaws36on each set of chains are spaced two package lengths from one another. The heated jaws on the first set of chains34are located between, and perpendicularly displaced from, the heated jaws on the second set of chains35, so that the formation of a second seal is one package length away from the first seal.

Due to the relative staggered, or interleaved, positioning of the jaws on the first and second sets of chains (as shown inFIG. 11), a first transverse seal will be made by jaws carried on the first set of chains, with a second transverse seal being made by jaws carried on the second set of chains. It can be seen that the continuously moving heated jaws36will form a first seal in a region already occupied by the product, while the product is being supplied from the fill pipe22. The movement of the driven chains advances the tube50downwardly through the machine, where a perpendicularly-spaced pair of jaws forms a second transverse seal (also in a region occupied by the product). The result is a continuous chain of packages that is conveyed to a cutting means (not shown), wherein each of the transverse seals is severed along its length to form individual tetrahedron-shaped packages. The present process creates a string of linked packages that are subsequently cut into individual units through the middle of the transverse seal. For this reason, it is desirable to make the transverse seal as robust as possible.

FIG. 4shows a cross-section of the tube-forming subassembly24, as taken along line4-4ofFIG. 3. The tube-forming subassembly24may be seen in larger scale inFIG. 9B. The tube-forming subassembly24includes a forming ring with an aperture in the center thereof, in which the fill pipe22is centered. The tube-forming subassembly24also includes a first forming ring panel150, a second forming ring panel152, and a pair of adjustable fin spacing guides154. The second forming ring panel152includes a machined slot in which the longitudinal edges of the sheet material12are positioned to facilitate production of the longitudinal fin seal. The forming ring panels150,152are bolted together (bolts not shown), so that one panel may be easily removed to allow for the removal and cleaning of the fill pipe22. The tube-forming subassembly24may have apertures of different sizes to accommodate fill pipes of different sizes (and, consequently, to produce packages of different sizes). The forming ring panels150,152are preferably made of stainless steel, but may be made of other durable, thermally stable material instead.

FIG. 4also shows motor300, which drives a plurality of threaded pulleys304,306,308, which are connected to an idler roll310. The pulleys are connected by a belt302. A pivoting pneumatic cylinder190permits adjustment of the tension on the belt302by permitting the movement of the idler roll310. Pulley304is connected to motor300, via a drive shaft. Pulley306is connected, via a shaft, to a first tube-conveying assembly30, and, likewise, pulley308is connected, via another shaft, to a second tube-conveying assembly30. Idler roll310acts as a belt tensioner and is connected to the frame of the packaging machine.

In the center ofFIG. 4is shown the longitudinal seal-heating subassembly, which has a pair of heater arms160. Heater arms160are opened and closed via pneumatic cylinders162. Such operation will be described in greater detail, in reference toFIGS. 6A-6C.

FIG. 5illustrates tube-forming subassembly24and the positioning of the sheet material12within the machined slot formed in forming ring panel152. The space between the fill pipe22and the aperture in forming ring panels150,152is very small, so that the sheet material12is held securely in position for production of the longitudinal seal. Slots of different dimensions may be used to create fin seals of different size.

Since the filling of the packages is a continuous process, the formation of the longitudinal seal is also a continuous process. The forming of the longitudinal seal4occurs while the stock material12is dry (that is, before introduction of the package contents), whereas the formation of the transverse seals6,8, as will be discussed herein, occurs when the stock material12is wet (that is, the tube50of stock material is filled with the package contents).

FIGS. 7 and 8are cross-sectional views of the seal-pressing subassembly28. The seal-pressing subassembly28includes a pair of pressure rollers128,128′ and a pneumatic pressure roller cylinder130, which moves pressure roller128from an open position to a closed position. Alternately, the pressure rollers128,128′ may be spring-activated. The closed position is illustrated in further detail inFIG. 8, which shows the pressure rollers128,128′ converging on the sheet material and forming the longitudinal seal that produces tube50. Although one set of pressure rollers128,128′ is shown, two sets may instead be used. The pressure rollers128,128′ may be made entirely of steel or may have a steel shaft with a urethane-coated flange.

FIG. 9Ais a cross-sectional view of a portion of the tube-conveying subassembly30. The tube-conveying subassembly30includes a pair of pulleys, which are indicated on either side of fill pipe22as pulleys172(pulleys176are not shown in this view). A stationary flanged guide174is positioned between the pulleys172,176. A rubber belt170is wrapped around the pulleys172,176and the guides174on each side of the packaging tube50. The pulleys172,176are positioned by the action of pneumatic cylinders180, in which the engaged position of the pulleys172,176is at the end of the stroke of the pneumatic cylinders180.

The mechanics of the tube-conveying subassembly30are better shown inFIG. 9B. A motor300is connected to a belt302, which is threaded around pulleys306,308and an idler roll310. The idler roll310may be positioned by an air cylinder190. Pulley306is attached, via a first shaft, to a first pulley176, and a pulley308is attached, via a second shaft, to a second pulley176. As the pulleys306,308are rotated, the shafts turn pulleys176in the directions shown by arrows inFIG. 9B. As a result, the belts170around the pulleys172,176are also set into motion. Because there is a greater friction between the rubber belts170and the packaging tube50than there is between the packaging tube50and the fill pipe22(not shown), the contact between the pulleys172,176and the packaging tube50allows the packaging tube50to be pulled through the packaging machine.

FIG. 10Ais a schematic representation of the transverse sealing subassembly220of the present packaging machine. As shown inFIG. 10A, the pressure jaws38are located along a pair of chains32, and the heated jaws36are located along a pair of chains34. The tube50of stock material is pulled downwardly through the traverse sealing subassembly220. A first pressure jaw38and a first heated jaw36come into contact with one another, as shown, during the rotation of their respective chains along an oval path. The chains32,34carrying the pressure jaws38and the heated jaws36, respectively, rotate in opposite directions, due to their placement within the transverse sealing subassembly220.

The motion of the chains32,34causes a rolling contact between the heated jaw36and the pressure jaw38. Initially, the lower edges of the faces of the pressure jaw38and the heated jaw36come into contact with each other, and the subsequent increasing contact between the jaws36,38forces the product (for example, the liquid contents) out of the transverse seal area (that is, the area between the jaws36,38). The removal of the product from the seal area enables a consistent transverse seal to be made across the width of the package, as the heated jaw36heats the tube50in the area of the seal, causing the meltable coating on the interior of the stock material to become molten. Simultaneously, the pressure jaw38pushes the molten seal areas together, so that a strong, uniform seal6is made. The temperature of the heated jaw36at its face is typically between about 250° F. and 450° F., depending upon the stock material12being used. The force applied by the pressure jaw38over the contact area is typically from about 200 pounds to about 800 pounds. Generally, the dwell time of the packaging material in the area of transverse seal formation is approximately from about 0.1 seconds to about 1 second, depending on the speed of the packaging machine.

As discussed previously, in the formation of tetrahedral packages, an additional set of heated jaws36and pressure jaws38are located perpendicularly to those shown in the illustration, each respectively located along its own pair of roller chains (as will be described with reference toFIG. 11). These perpendicularly oriented sets of heated jaws and pressure jaws form the transverse seals8, in the same manner as described above for transverse seals6.

Although the conveying mechanisms for the jaws36,38are shown as roller chains, other mechanisms may be used, including, for example, solid belts, belts perforated with openings for receiving the jaws, flat chains, linked chains, O-ring chains, and the like. If belts are used, it may be desirable to make the belts from stainless steel to prevent stretching with use, which could cause misalignment of the jaws.

FIG. 10Aalso illustrates a closed-loop, modified electrical system140, which powers the heated jaws36. Each heated jaw36includes an electrical contact-containing back510having at least a pair of electrical contacts, which creates an electrical connection between a heater cartridge inside the heated jaw36and the power rails140. A pair of power rails140is provided, at least one of which is configured with a base level portion142and a power-correction portion144. The base level portion142of the power rails140, which comprises the majority of the length of the power rails, maintains at least a minimum energy level necessary to power the heater cartridges within the heated jaws36. The power-correction portion144of the power rails140comprises a length on the power rails that is approximately equal to one pitch (that is, the distance between two adjacent heated jaws36). The power-correction portion144supplies additional energy to any heated jaw36that has a temperature measurement that is lower than the target temperature for the heated jaws36. The power-correction portion144of the power rails140needs only to be long enough to be in contact with one jaw36at a time.

The power rails140are controlled by a programmable logic controller (or “PLC”)260that includes a data transmission reader (not shown). When the heated jaw36passes a stationary antenna270, the wireless transmitter280is activated, at which time the thermocouple on the heated jaws36takes multiple temperature measurements across the jaw face. These measurements are then transmitted via a wireless transmitter280(shown in more detail inFIGS. 12 and 13) back to the stationary antenna270. The stationary antenna270is mounted in close proximity (for example, between 0.375 inches and 0.5 inches) to the path of the heated jaws36. From the antenna270, the data is transmitted to the PLC260, which determines whether an adjustment needs to be made.

In practice, the PLC260compiles data for all of the heated jaws36on a particular pair of chains and makes adjustments to either the base level portion142of the power rails140or the power-correction portion144of the power rails140. If a particular heated jaw36exhibits temperature readings that are lower than the other heated jaws36, the PLC260increases the power in the power-correction portion144of the power rails140, when that particular heated jaw36contacts the power-correction portion144. If all of the heated jaws36exhibit lower-than-desired temperatures, then the PLC260will increase the power in the base level portion142of the power rails140. Adjustments to the base level portion142of the power rails140are made by setting the heated jaw36with the highest temperature at the desired temperature for all of the heated jaws36.

Conversely, if all of the heated jaws36exhibit higher-than-desired temperatures, then the PLC260may decrease the power in the base level portion142of the power rails140. In this way, the transverse sealing subassembly220provides independent control for consistent temperatures across the face of the heated jaws36and from jaw-to-jaw, thereby ensuring that consistent seals are formed in the transverse direction from package to package. Ideally, the temperature variation across the face of the heated jaws36and among the heated jaws36is no more than about 10° F. (or about 5° C.). The heated jaws on the other pair of chains are similarly controlled by the PLC260.

FIGS. 10B and 10Cillustrate the back510of the heated jaws and the electrical system140ofFIG. 10A. As shown inFIG. 10B, the back510of the heated jaws includes a pair of electrical contacts141′ and142′.FIG. 10Cis an isometric representation of the electrical system140, showing the positioning of seven heated jaws around the power rails141,142. Although seven heated jaws are shown, any number of jaws may be used. Power rail141may be an electrified rail or may be a neutral rail; for the sake of discussion herein, this rail will be referred to as a “common” rail. Power rail142is an electrified rail, which has a power-correction portion144. As discussed above, the power-correction portion144has a length that is approximately equal to one pitch (that is, the length between two adjacent heated jaws). Electrical contact141′ is in contact with power rail141, and electrical contact142′ is in contact with power rail142.

FIGS. 10D,10E, and10F illustrate an alternate embodiment to the heated jaws and electrical system shown inFIGS. 10B and 10C. In this embodiment, an even number of heated jaws are used, half of the heated jaws having a back612with two electrical contacts341′,342′ and the other half of the heated jaws having a back614with two electrical contacts341′,346′. As illustrated, the heated jaws each have an electrical contact341′, which is commonly positioned and which contacts common rail341.

FIG. 10Fis an isometric representation of an electrical system340, showing the positioning of eight heated jaws around three power rails341,342, and346. The heated jaws are arranged in an alternating configuration, such that a heated jaw with back612is positioned between heated jaws with back614(and vice versa). Power rail342includes a power-correction portion344, and power rail346includes a power-correction portion348. Because each heated jaw is powered by a different pair of power rails than its adjacent jaws—for example, a first jaw is powered by rails341,342, and its adjacent jaws are powered by rails341,346—the power-correction portions344,348may be extended, in length, to approximately twice the pitch between adjacent jaws. Thus, two adjacent jaws may be corrected simultaneously, and the length of time available to correct the power for the heated jaws is twice as long as the arrangement shown inFIGS. 10A and 10C.

FIGS. 10G,10H,10I, and10J illustrate yet another embodiment of heated jaws and a corresponding electrical system540, in which the number of heated jaws is divisible by three.FIGS. 10G,10H, and10I represent the backs710,712, and714of three heated jaws, which are arranged sequentially around power rails541,548,546, and542(shown inFIG. 10J). Each of the heated jaws has a common electrical contact541′, which contacts common rail541. The back710of the heated jaw ofFIG. 10Gincludes electrical contacts541′ and542′ and represents jaws that are powered by contact with power rails541,542. The back712of the heated jaw ofFIG. 10Hincludes electrical contacts541′ and546′ and represents jaws that are powered by contact with power rails541,546. The back714of the heated jaw ofFIG. 10Iincludes electrical contacts541′ and548′ and represents jaws that are powered by contact with power rails541and548.

As shown inFIG. 10J, power rails542,546, and548include power-correction portions543,547, and549, respectively. The power-correction portions543,547, and549may be extended, in length, to approximately three times the pitch between adjacent jaws. Thus, three jaws may be corrected simultaneously, and the length of time available to correct the power for the heated jaws is three times as long as the arrangement shown inFIGS. 10A and 10C.

Although the electrical systems described above represent various embodiments that may be successfully employed, it should be understood that numerous variations may instead be used, including a system having an n+1 number of rails, where n is the number of heated jaws. In such a system, each heated jaw is powered by its own dedicated power rail, and all of the heated jaws share a common rail. Using this approach, the power rails may be constantly adjusted during real-time, as measurements indicate are necessary.

Further, although the electrical contacts have been illustrated as being spring-loaded, other types of electrical contacts may be used, including, without limitation, contacts that straddle the power rails and contacts that slide along the power rails in contact with one or both edges of the rails.

FIG. 11illustrates the arrangement of multiple heated jaws36and pressure jaws38and the positioning of the stock material tube50, as it is conveyed through the transverse sealing subassembly. For ease of illustration, each pair of chains32,34,35is represented as a single chain. Each of the pair of chains33is shown. A first set of heated jaws36is located along a pair of chains34, while the cooperative set of pressure jaws38is located along a pair of chains32. A second set of heated jaws is conveyed along chains35, while its cooperative set of pressure jaws38is conveyed along chains33. To create the perpendicular transverse seals6,8that are characteristic of a tetrahedral container2, the respective sets are perpendicular to one another and are spaced one package length apart from one another. Along each chain32,33,34,35, the jaws36or38are positioned two package lengths apart from each other, so that the transverse seals6,8are appropriately spaced.

The longitudinal fin seal4is visible as the stock material tube50enters the transverse sealing area. As indicated by phantom lines, fin folding guide60contacts the longitudinal fin seal4and pushes it against the tube50. In those instances where a meltable coating is present on the outside of the stock material, the formation of the transverse seals6,8tends to melt the fin seal4(in the area of the transverse seal) into position against the package. In instances where a manufacturer chooses to produce a pillow-shaped package2′, only one set of opposed heated jaws36and pressure jaws38is necessary. In both instances, depending on the desired package size, the size, number, and position of the heated jaws36and pressure jaws38may be adjusted.

FIGS. 12 and 13illustrate two different versions of a heated jaw (identified as36and436).

As shown inFIG. 12, the heated jaw36includes a heated jaw base290, which connects to chains34or35. The heated jaw36includes a heated jaw block (made of face component296and rear component298) that houses a heater cartridge284with uniform power density. The rear component298of the heated jaw block is attached to an insulator block294, which couples with a transmitter housing282at one end of the insulator block294. The wireless, digital transmitter280is positioned within the transmitter housing282, which (along with the insulator block294) is attached to base290. The electrical contacts are attached to the back510of the base290via intermediate insulating washers.

A thermocouple281for measuring the temperature of the jaw face is positioned inside an axially bored channel that terminates in the approximate center of the heated jaw block296as close to the jaw face as possible. Readings from the thermocouple are transferred to the wireless digital transmitter280, which is held in a transmitter housing282. As described previously with reference toFIG. 10, the wireless transmitter280digitally transmits the data to a stationary antenna260, which relays the information to a reader and programmable logic controller270. These wireless transmitters280, which are manufactured by MicroStrain, Inc. of Williston, Vt., are accurate, precise, and reliable and show little variation or drift over long periods of use.

The wiring for the heater cartridge284is threaded through the insulator block294and is terminated within the spacer292. Within the base290is an electrical connection housing, which includes a pair of electrical contacts510that contact the power rails described previously.

FIG. 13illustrates a second version of the heated jaw36. In these Figures, the heated jaw is identified as heated jaw436. Connected to the base490is a spacer492(which may optionally be formed into the base490). An insulator block494is connected to, and is positioned between, the spacer492and a heated jaw block496. The heated jaw block496includes a jaw face, a thermally conductive core495, and a heater cartridge484. The heater cartridge484is surrounded by a thermally conductive core495and is held in position by a cartridge holder485. The heater cartridge484has a variable power density, resulting from the localized placement of the heater coils at each end of the cartridge. Such a configuration is useful to combat heat loss at the respective ends of the heated jaw block496and to ensure uniform heat transfer across the jaw face (as the heat is distributed evenly by the thermally conductive core495).

The thermally conductive core495is made of a material that is highly thermally conductive (that is, which exhibits a high k value indicative of ability to conduct heat). For this purpose, the core is preferably made of copper, aluminum, gold, silver, antimony, zirconium, tungsten, alloys of such metals, and the like. Aluminum and copper are the most cost-effective materials. Preferably, the thermally conductive core495is copper or a copper-containing alloy, because of its high thermal conductivity. The thermally conductive core495promotes uniform heating across the face of the heated jaw436and also facilitates the maintenance of the face of the heated jaw436at the desired temperature.

Heated jaw436operates on the same basic principles as heated jaw36. InFIG. 16, the wiring from the transmitter480, which is connected to a thermocouple, is positioned inside a bored channel in the heated jaw face496. The temperature readings from the thermocouple481are transmitted digitally from the transmitter480to the antenna270(shown inFIG. 10). The wiring of the heater cartridge484is threaded through the insulator block494and support component492before being attached on the back of the base490to two or more electrical contacts that contact the power rails described previously.

In the case of both heated jaw36and heated jaw436, the heated jaw face is preferably made of a hard, thermally stable material, such as heat-treated stainless steel having a hardness value on the Rockwell-C hardness scale of about HRC 58. It was found that other materials, such as heat-treated brass, for example, having a hardness value of HRC 27, lacked the hardness to resist damage from repeated contact with the pressure jaws. In those instances where the stock material includes a meltable coating on the outside, it may be desirable to use a heated jaw face with a non-stick coating to facilitate release of the transverse seals from the heated jaws.

The patterned jaw face, as illustrated, using multiple intersecting lines, promotes seal integrity by providing a plurality of channels inside the tube of packaging material through which the liquid contents may be pushed upward as the transverse seal is made. It should be noted that the patterns in the jaw face are formed in the transverse seals on the package and, thus, may be desirably modified for aesthetic purposes as well as functionality, taking the properties of the stock material into consideration.

The concept of package “headspace” is familiar to those skilled in the art of intermittent-fill packaging. In packages such as milk cartons, headspace is the area filled with air between the level of the product and the top of the container. In continuous fill packaging, such as is presently described, the filled packages have no headspace, because there is no air in the filled packages. However, to mimic the effect of having a headspace, it may be desirable under some circumstances to create a “false headspace” by slightly compressing the package as it is being sealed.

This false headspace may be achieved by the addition of curved plates422,488to the top and bottom of the heated jaw436. The upper headspace plate422is attached to mounting plate420, while the lower headspace plate488is attached to a mounting plate498on the bottom of the heated jaw436. The mounting plates420,498are attached to the insulator block494, which prevents the headspace plates422,488from becoming heated by contact with the heater jaw block496. If the headspace plates422,488become heated, as in previous false-headspace mechanism designs, their contact with the stock material may damage the appearance of the stock material (for instance, if the outside of the packaging material is printed, it may be smeared by heat from the headspace plates).

The headspace plates422,488engage the tube of packaging material and slightly compress the tube, just before formation of the transverse seals. This compression results in the sealed package being under tension, such that, when the package is opened, a slight vacuum is formed. As a result, the package contents are “pushed” into the bottom of the package by air rushing into the package, thus preventing the contents from splashing out onto the consumer.

FIG. 14illustrates a pressure jaw38, which acts in cooperative relation with either the heated jaw36or the heated jaw436. The pressure jaw38is a much simpler element, including a base390and a pressure jaw face396. The pressure jaw face396may be made of different materials, depending upon the stock material being used for the packages. For example, if the stock material is a coated paper, the pressure jaw face396may be stainless steel. If the stock material is a multi-layer film, then the pressure jaw face396may be made of rubber or a rubber-like material. In either instance, the pressure jaw face396is preferably made from a heat resistant, resilient, and durable material. When the pressure jaw face396is rubber or rubber-like, it may be made in a domed shape, such that the compression of the pressure jaw38against the heated jaw36helps to force the product contents out of the seal area.

FIGS. 15A,15B, and15C are representative of various stock materials useful for making packages in accordance with the teachings herein. In each Figure, the top layer represents the outermost layer of the packaging container.FIG. 15Aillustrates a multi-layer film structure600, in which the outermost layer is a polymer film layer602. The polymer film layer602may be printed on either side, although, for many applications, reverse printing on the lower side of the polymer film layer602may be preferable. The central layer in the multi-layer film structure600is a polymer film606that is surrounded on each side by a relatively thin film layer604. The relatively thin film layer604acts as a binder for the other layers. The polymer film606may be metallized or otherwise treated for barrier properties, as desired. A meltable sealant film layer608forms the innermost layer of the structure600.

Polyester films are well-suited for layers602,606, though other polymers (such as polypropylene or nylon) may be used instead. These layers602,606preferably have a thickness in the range of about 48 gauge, but other thicknesses may be used.

FIG. 15Billustrates a multi-layer foil structure650, in which the outermost layer is a polymer film layer652. As before, the polymer film layer652may be printed only either side. The central layer in the multi-layer foil structure650is a foil656that is surrounded on each side by relatively thin film layers654,658. It may be desirable to make the film layer654an opaque layer (such as a white layer), so that the foil layer656is not apparent from the outside of the package. A meltable sealant film layer660forms the innermost layer of the structure650.

FIG. 15Cillustrates a multi-layer coated paper structure680, in which the outermost layer is a coated paper layer682. A tie layer688connects the coated paper layer682to a barrier film684that is positioned on the back side of the coated paper layer682. As with the other multi-layer stock materials, a meltable sealant film686forms the innermost layer of the structure680. The paper layer682preferably contains an outer coating, which protects the outside of the packaging container.

When making packages having a longitudinal fin seal, such as those described herein, it is unnecessary to have a meltable coating or layer on the outermost side of the packaging material. This advantage is due to the inside-to-inside sealing of the packaging material, which requires only that the innermost layer of the stock material be meltable. Thus, any printing applied to the face of the outermost layer is maintained throughout the sealing and filling process without being smeared.

Although reference has been made throughout this description to the package contents as being consumable foodstuffs, it should be readily apparent to those of skill in the art that the packages and equipment described herein are equally useful in packaging inedible products, such as adhesives, caulks, detergents, and the like.