PACKAGE SEALING ANVIL

Abstract: A sealing anvil (18) for sealing film to packages, such as trays, includes a replaceable anvil with a resilient upper surface (20). The anvil may be connected to a guide (22) which guides the tray or other package into position on top of the anvil.

Description: Package Sealing Anvil Background This invention relates generally to sealing plastic film onto packages and particularly to techniques for sealing film onto relatively rigid plastic packages. Food products such as meat are commonly contained in a foam tray covered by a plastic film. With more rigid plastic materials used to make trays, some difficulties arise in getting a good seal between the film and the tray. A relatively rigid tray may be slightly irregular and these irregularities may result in inadequate sealing, at particular locations, between the film and the tray. This difficulty maybe addressed by using a sealing platen or anvil which includes a T- shaped grommet which provides a cushioned sealing surface between the lower side of the package tray flange and the sealing platen or anvil. However this solution has its own drawbacks. It is not uncommon for the grommet to fit imperfectly within its seat. This may cause the upper surface of the grommet to be as irregular as the tray being sealed. Again, the result may be inadequate sealing between the film and the tray. In addition, the T-shaped grommets tend to give in the center (where they are less supported) resulting in an inadequate seal at the center and a pair of sealed regions extending to either side. This can also result in inadequate sealing. Thus, there is a continuing need for a sealing anvil which facilitates reliable sealing between the tray and the film particularly with relatively rigid trays or other packages. Summary In accordance with one aspect, a sealing surface for a machine for sealing film onto the sealing flange of a package includes a support and a sealing anvil. The anvil is adapted to conform to the sealing flange. The anvil includes a rigid element and a flexible member secured to the rigid element. The anvil is removably secured to the support. In accordance with another embodiment, a sealing station for a machine for sealing film to the sealing flange of a package includes a sealing anvil and a guide. The anvil has a surface adapted to engage the sealing flange. The guide is secured to the anvil at a point spaced from the surface of the sealing anvil. Brief Description Of The Drawings Figure 1 is a cross-sectional view of one embodiment on a sealing station in accordance with the present invention; Figure 2 is an enlarged perspective view of the sealing anvil shown in Figure 1; and Figure 3 is a cross-sectional view of a portion of the station shown in Figure 1, showing the interaction between a tray and the guide edge in accordance with the embodiment shown in Figure 1. Detailed Description Referring to Figure 1, a sealing station 10 for a packaging machine includes an upper cover 12 and a lower cover 14. The upper and lower covers 12 and 14 may be moveable towards and away from one another to trap a film 34 between the two covers. A seal bar 26 may be mounted on the upper cover 12 for sealing the film 34 to a tray or other package portion 28. More particularly, the film 34 is sealed to the tray flange 32 which extends around the peripheral edge of the tray. The tray 28 is seated on a sealing anvil 18 which is in turn supported on a guide 16. The sealing anvil 18 is connected removably to the guide 16 by threaded fasteners 24. A guide edge 22 is defined as extending outwardly of the sealing anvil 18 and spaced downwardly from its upper edge. The sealing anvil 18 may include a sealing cushion 20 on its upper end, arranged to engage the lower surface of the tray flange 32 below the seal bar 26. The sealing cushion 20 may be made of a variety of flexible or resilient materials including silicon rubber. In one desirable embodiment, the silicon rubber may be coated onto the sealing anvil 18 and pressure and heat cured in place. The anvil 18 may be made of aluminum. When the film 34 is sealed to the upper surface of the tray flange 32, a packaged item 36 may be contained within the package in a desired atmosphere. Subsequent stations may be responsible for trimming the film and implementing other packaging functions. The anvil 18 shown in Figure 2 may be formed from a blank of aluminum of other metal material coated with a resilient material to form the sealing cushion 20. The desired shape to conform to the tray 28 or other package flange 32 may then be defined from the blank. In one advantageous embodiment, a programmable water jet may be utilized to cold cut the shape shown in Figure 2 from the blank. Because of its cold cutting capability, the integrity of the sealing cushion 20 is unaffected by the cutting operation. In this way, a carefully shaped sealing anvil may be formed which can then be secured to the sealing station. If the anvil 18 wears out, perhaps because the cushion 20 fails, the sealing anvil 18 may be easily replaced by undoing the threaded fasteners 24 and providing a new anvil 18. Referring now to Figure 3, the operation of the guide edge 22 is illustrated. When the tray 28 is initially moved towards the guide 16, its tapered lower end 36 is first guided by the upwardly extending anvil 18. As the tray portion 36 extends downwardly, the lowermost edge 37 eventually engages the outwardly extending guide edge 22. The free ends of the guide edge 22 present a smaller opening than that presented by the edges of the sealing anvil 18. This provides a guiding action which causes the tray 28 to self-nest in the sealing station. It may not be necessary in many instances to further push the tray into position. The guiding effect achieved initially by the anvil 18 and subsequently by the outwardly extending sealing edges 22, causes the tray to nest nicely as shown in Figure 1 in position, using only gravity forces in many cases. From the position shown in Figure 1, with the tray 28 seated in the sealing station 10, the guide edge 22 engages a central region 38 of the tray sides 40. For example, the guide edge 22 may engage a de-nesting feature commonly used in many trays. The present invention is particularly useful in connection with relatively rigid trays. Through the provision of the sealing cushion 20, a good seal may be made completely around the periphery of the tray. Even if the tray has some irregularities, the downward force applied by the sealing bar 26 can be distributed about the flange 32, resulting in an even seal around - the entire periphery. Because the anvil 18 is replaceable, the design can achieve substantial cost savings since it is not necessary to replace the entire guide and anvil but only the anvil 18 itself need be replaced. Moreover, through the provision of the guide edge 22, the incoming tray or other package can be guided into position to expedite the sealing operation or to further facilitate sealing by decreasing the need for additional steps to position the tray or package in the sealing station. While the present invention has been described with respect to a single embodiment, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations that fall within the true spirit and scope of the present invention. What is claimed is:

Claims: 1. A sealing surface for a packaging machine for sealing film onto a sealing flange of a package comprising: a support; and a sealing anvil adapted to conform to the sealing flange, said anvil including a rigid element and a resilient member secured to said rigid element, said anvil being removably securable to said support, said resilient member formed by a resident material deposited on said rigid element. 2. The surface of claim 1 wherein said rigid element and said flexible member are cut as an integral unit. 3. The surface of claim 2 wherein said rigid element and said resilient member are cut by a water j et cutting system. 4. The surface of claim 1 wherein said support includes a guide edge arranged generally perpendicularly to said rigid element. 5. The surface of claim 4 wherein said guide edge extends inwardly relative to said rigid element. 6. The surface of claim 1 wherein said anvil is secured to said support by a threaded fastener. 7. The surface of claim 5 wherein said guide edge defines a smaller cross sectional passage than said sealing anvil. 8. The surface of claim 1 wherein said support includes a guide edge adapted to engage said package as said package is dropped into engagement with said sealing anvil and to guide said package flange into engagement with said sealing anvil. 9. A method of sealing a film to a tray over a sealing flange comprising: displacing said tray towards a sealing anvil; guiding said tray into alignment with said anvil before said tray is engaged on said anvil; and engaging said tray on said anvil for sealing. 10. The method of claim 9 including resiliently supporting said tray flange atop said anvil. 11. The method of claim 9 including depositing a cushioning material on a metal blank, and cutting said resilient material and metal blank using a water jet cutter. 12. The method of claim 9 including removing said anvil and replacing said anvil.

Inventors: GORLICH MICHAEL, MCPHERSON ROBERT JR, GORLICH, MICHAEL, MCPHERSON, ROBERT, JR.
Applicants: WORLD CLASS PACKAGING SYST, WORLD CLASS PACKAGING SYSTEMS, INC.
Application year: 1999
Main classification: B65B7
IPC codes: B65B7, B65B51