WO2018046932A1

WO2018046932A1 - Vacuum dome

Info

Publication number: WO2018046932A1
Application number: PCT/GB2017/052623
Authority: WO
Inventors: Stephen James WINDSOR
Original assignee: Proseal Uk Limited
Priority date: 2016-09-08
Filing date: 2017-09-08
Publication date: 2018-03-15
Also published as: GB201615245D0; GB2553768A

Abstract

A vacuum dome 1 for skin packing apparatus has an internal surface 4. At least one aperture 5 is formed in the internal surface through which air may be extracted. At least one aperture 5 is associated with at least one formation 7, such as a channel, on the internal surface. The formation creates a path for air to flow from a position spaced from the at least one aperture to the aperture when the dome is in use and a plastics film is urged onto the internal surface. Multiple elongate channels may be formed in the internal surface and multiple apertures may be disposed in each channel.

Description

VACUUM DOME

Technical Field of the Invention

The present invention relates to a vacuum dome for skin packing apparatus, and to packing apparatus comprising such a vacuum dome. Background to the Invention

Skin packing involves sealing a sheet of transparent plastics film over a product placed on a sheet of material such as card or, where a fresh foodstuff is being packaged, typically a plastics material tray. Vacuum may be used to obtain a close fit of the transparent film over the product and the film is typically heat sealed to the underlying sheet or tray.

An existing skin packing apparatus comprises a vacuum dome. The dome has a smooth internal surface through which an array of circular apertures are formed. In use the apertures are connected to a vacuum pump and the dome is mounted to a heater which heats the dome and thus its perforated surface. Transparent plastics film is drawn out just beneath the dome, extending across the opening to the dome's perforated interior surface. A vacuum is then applied to the apertures in the dome drawing air out of the dome and drawing the plastics film towards and into contact with the internal surface of the dome. The film is heated both by contact with the dome by radiant heat from the dome. A product to be wrapped is placed on a plastics material tray, with at least one aperture extending therethrough. The tray is supported on a seal extending around an opening to a vacuum chamber, which is also connected to a vacuum pump. The seal extends around and adjacent to the perimeter of the tray, and is the same shape as the edge of the dome. The chamber and dome are then brought together so that that the film overlying the edge of the dome and the edge of the tray around its periphery are nipped between the edge of the dome and the vacuum chamber. The heat of the dome, and pressure applied, causes the film to be heat sealed to the edge of the tray.

Vacuum is then applied to the chamber beneath the tray. Air is thus drawn from under the tray and from between the film and the tray, through the aperture in the tray.

The dome is then disconnected from the vacuum pump and atmospheric air admitted into the dome through the apertures in the dome. This air urges the heated plastic film onto the product and the tray and the film adheres to the tray surrounding the film, tightly encapsulating the product onto the tray.

In practice, however, bubbles of air often become trapped beneath the plastic film, preventing the film from adhering to the tray and causing an unsightly appearance. This is thought to be as a result of the film falling into contact with the tray before all of the air beneath the film has been extracted.

It is an object of embodiments of the present invention to address this problem.

Summary of the Invention

According to an aspect of the invention there is provided a vacuum dome for skin packing apparatus, the dome comprising an internal surface, at least one aperture formed in the internal surface through which air may be extracted, wherein the at least one aperture is associated with at least one formation on the internal surface and the formation is configured to create a path for air to flow from a position spaced from the at least one aperture to the aperture when the dome is in use and a plastics film is urged onto the internal surface.

Provision of one or more formations on the internal surface of the dome associated with one or more apertures increases the points from which air can flow out from between film and the dome when the dome is in use. This reduces the amount of air that becomes trapped between a film and dome during use of packing apparatus. This is advantageous as it is thought to be air trapped in this way which leads to bubbles or air being trapped under the film covering a product. This is because air trapped between the film and dome will cause the film to separate from the dome as air is removed from the region beneath the film surrounding a product. The film may thus come into contact with the product and material on which the product is supported, to which it will adhere, before all the air has been evacuated from around the product, and thus trap some of the air to form a bubble.

A plurality of apertures may be formed in the internal surface of the dome. In examples at least 25, 50 or 100 apertures are formed in the internal surface of the dome.

A plurality of apertures may be generally evenly spaced over the internal surface of the dome and may be arranged in a rectangular array.

The or each aperture may be substantially circular.

The cross-sectional area of the or each aperture may be less than 2mm². The or each formation may be a channel. The channel may be recessed into the internal surface. Alternatively or additionally a channel may be formed by raised walls on the internal surface. According to another aspect of the present invention, therefore, there is provided a vacuum dome for skin packing apparatus, the dome comprising an internal surface, at least one aperture formed in the internal surface through which air may be extracted, wherein the at least one aperture is disposed in a channel formed in the internal surface. Other types of formation are possible.

The channel may be elongate. The or each aperture may be disposed approximately mid-way between opposite parallel sides of the channel. The or each channel may be substantially straight.

There may be a plurality of channels, one or more apertures being formed in each channel.

Two or more channels may intersect.

A plurality of adjacent, spaced apart channels may extend in a first direction, and at least one further channel may extend through the adjacent spaced apart channels.

In an embodiment the dome defines a generally rectangular opening, from the inside edge of which the internal surface extends, a plurality of apertures are spaced over the internal surface in a substantially regular rectangular array, first channels are formed along substantially parallel first rows of apertures in the array and second channels are formed along substantially parallel rows of apertures in the array in a direction substantially at right angles to the first rows of apertures, some or all of the second channels intersecting some or all of the first channels. Many variations are of course possible in how the or each channel is arranged. In other embodiments the or each channel may be curved and could, for example, be circular or spiral. Channels could be formed as concentric rings.

The or each channel may comprise an arcuate surface. For example it may have a part or semi-circular cross-section.

The dome may define an opening with any suitable shape, from the inside edge of which the internal surface extends. It could for example be substantially circular, oval or some polygonal shape other than rectangular.

According to another aspect of the invention there is provided skin packing apparatus comprising a vacuum dome according to the invention.

Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a perspective view from below of a vacuum dome for skin packing apparatus;

Figure 2 is a side view of skin packing apparatus incorporating the dome of figure

i ;

Figure 3 is a vertical cross-section through figure 2; Figures 4-6 correspond to figure 3, showing the apparatus during different stages of a packing process; and

Figure 7 is a perspective view of the tray shown in figures 5 and 6. Throughout the drawings the terms up, down, top, bottom and like terms are used to describe the apparatus in the orientation shown in the drawings, which (in figures 2 to 7) is the orientation in which it is intended to be used, and are not intended to be otherwise limiting. Referring to the drawings, skin packing apparatus includes a vacuum dome 1.

The dome has a substantially flat edge 2 surrounding a substantially rectangular opening 3, with rounded corners, into the dome. The interior surface of the dome 4 is generally concave, that is to say it defines a volume behind the opening to the dome. In the illustrated example the interior surface extends away from each of the four straight edges of the dome at an angle of approximately 30 degrees to the plane of the opening

3 into the dome and curves to form a generally flat, rectangular region generally parallel to, but spaced from, the plane of the opening into the dome. Of course, other shapes are possible. For a dome with a substantially circular opening the internal surface could be substantially hemispherical. In general, the internal surface should be free from discontinuities, sharp angles or edges.

A plurality of substantially circular apertures 5 are formed in the internal surface

4 of the dome. The apertures are arranged in substantially evenly spaced apart, substantially parallel substantially straight rows, the apertures being substantially evenly spaced in each row, so as to form a rectangular array of apertures. In the illustrated example there are seventeen short rows of eleven apertures extending in one direction and, correspondingly, eleven long rows of seventeen apertures extending substantially at right angles to the long rows. The apertures have a diameter of about 1.5mm. The number and size of apertures can be varied as desired or as appropriate depending on application. Each aperture extends into a respective counter-bore 6 which opens out to the opposite side of the dome to the internal surface 4.

A plurality of elongate channels 7 are also formed in the internal surface of the dome, each channel extending along at least part of a row of apertures 5, so that each aperture lies substantially mid-way between the opposite long sides of the channel. A channel extends along the entire length of each of the short rows of apertures 5 that extend over the rectangular part of the internal surface 4 of the dome 1. A channel also extends along the entire length of the central long row of apertures 5. A respective channel also extends over the length of the part of each other long row of apertures from the edge of the dome to the edge of the rectangular part of the internal surface 4 of the dome. Each channel extends up to the inner side of the edge 2 of the dome. The channels 7 are formed as recesses in the internal surface 4 of the dome and have a concave cross-section. The cross-section may be part of an arc of a circle.

Additionally, four countersunk apertures 8 of larger diameter than those 5 of the rectangular array are also formed in the internal surface of the dome 1, one positioned in each corner of the rectangular region of the internal surface, for receiving fasteners.

In use the dome 1 is mounted to a packing plate 13 which is, in turn, mounted to the underside of a heated support 9 by way of fasteners, for example screws, passing through apertures 8 in the dome 1 and packing plate 13 and into the support. Alternatively the packing plate 13 may be mounted to the heated support 9 by a first set of fasteners and the dome 1 mounted to the packing plate 13 by a second set of fasteners.

In another embodiment there is no packing plate and the dome 1 is mounted directly to the heated support 1. The support 9 is connected to a controllable vacuum source (not shown) via a pipe 10 which fluidly connects the vacuum source to the counter bores 6.

In use, to package a product 11 the dome 1 is positioned over a transparent plastics film 12. The film is drawn taught beneath and generally parallel to the plane of the opening 3 to the dome 1 and extends beyond the edge 2 of the dome in all directions. The film 12 is closely spaced beneath the edge 2 of the dome 1, as shown in figure 3.

The dome 1 is heated by transfer of heat from the heated support 9 via the packing plate 13 (where present).

Vacuum is applied to the pipe 10, causing air to be drawn out of the dome 1 through the apertures 5. The film 12 restricts airflow into the dome 1, so pressure in the dome is reduced resulting in the film being urged into the dome by atmospheric pressure, as shown in figure 4. As the film 12 is forced into contact with the internal surface 4 of the dome 1 the channels 7 provide conduits for air trapped between the film 12 and the dome to flow to an aperture 5 in the dome. This reduces the amount of air the might otherwise become trapped between the film 12 and the dome 1. Also, film 12 overlying the channels 7 may become at least partially urged into the channels 7, serving to help retain the film 12 against the dome 1.

The product 11 to be packaged is placed onto a rectangular plastics material tray 14. The tray has a central, substantially flat rectangular region 8 for supporting a product, such as a foodstuff. A raised rim 15 extends around the rectangular region, extending from a sidewall which extends up from the periphery of the rectangular region. The rim substantially matches the shape of the edge of the vacuum dome 1. A respective aperture 16 is formed through the tray towards each corner of the flat portion of the tray. An arcuate raised wall 17 is moulded into each corner of the rectangular part of each tray extending to provide a barrier between the flat part of the tray and the aperture 16. This helps prevent material, especially liquids, on the tray being drawn through the apertures during a packing operation. The tray 14 is supported on a seal 18 disposed on an edge 19 of a vacuum chamber 20 connected to the vacuum source (not shown). The edge 19 corresponds in shape to the edge 2 of the dome 1 and hence the rim 15 of the tray 14.

The dome 1 and vacuum chamber 20 are brought together, as shown in figure 5, so that the rim 15 of the tray 14 is brought into contact with the film 12 overlying the edge 2 of the dome 1 and the two are urged together between the edge 2 of the dome and the seal 18 on the edge of the vacuum chamber 20. This causes the film 12 to adhere to the periphery of the try and the seal 18 to create a seal between the tray and the vacuum chamber 20.

The vacuum chamber 20 is then connected to the vacuum source, and air flows out of the chamber reducing pressure in the chamber beneath the tray. In turn this causes air to flow out from under the film 12, through the apertures 16 in the tray 14.

At the same time, or shortly afterwards, the pipe 10 is disconnected from the vacuum source and opened to the atmosphere allowing air to flow into the dome 1 through apertures 3 and build up atmospheric pressure within the dome which forces the film 12 into contact with the product and surrounding tray, to which it adheres, as shown in figure 7. Optionally the pipe could be connected to a pressurised air supply which supplies air at a pressure greater than atmospheric pressure to the dome 10. The vacuum chamber 20 is then disconnected from the vacuum source and air is admitted allowing the tray to be removed. The process may then be repeated.

It will be appreciated by the person of ordinary skill in the art that the skin packing apparatus may be implemented in a variety of different ways and arranged for manual or automatic operation. Where the invention differs from existing apparatus is in provision of the channels 7 in the internal surface of the vacuum dome. The channels aid extraction of air from above the film 12, which has been found to eliminate, or at least reduce the probability of, the film 12 coming into contact with the tray 14 prematurely, before all air has been evacuated from below the film, and thus avoid formation of air bubbles under the film.

The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A vacuum dome for skin packing apparatus, the dome comprising an internal surface, at least one aperture formed in the internal surface through which air may be extracted, wherein the at least one aperture is associated with at least one formation on the internal surface and the formation is configured to create a path for air to flow from a position spaced from the at least one aperture to the aperture when the dome is in use and a plastics film is urged onto the internal surface.

2. A vacuum dome as claimed in either claim 1 wherein a plurality of apertures are formed in the internal surface of the dome.

3. A vacuum dome as claimed in claim 3 where at least 25, 50 or 100 apertures are formed in the internal surface of the dome.

4. A vacuum dome as claimed in either claim 2 or 3 wherein the apertures are generally evenly spaced over the internal surface of the dome.

5. A vacuum dome as claimed in claim 4 wherein the apertures are arranged in a rectangular array.

6. A vacuum dome as claimed in any preceding claim wherein the or each aperture is substantially circular.

7. A vacuum dome as claimed in any preceding claim wherein the cross-sectional area of the or each aperture is less than 2mm².

8. A vacuum dome as claimed in any preceding claim wherein the at least one formation is a channel and the at least one aperture is disposed in the channel. A vacuum dome as claimed in claim 8 wherein the channel is elongate.

A vacuum dome as claimed in either claim 8 or 9 wherein the channel is substantially straight.

A vacuum dome as claimed in any of claim 8 to 10 comprising a plurality of channels, one or more apertures being formed in each channel.

A vacuum dome as claimed in claim 11 where two or more channels intersect.

A vacuum dome as claimed in claim 12 comprising a plurality of adjacent, spaced apart channels extending in a first direction, and at least one further channel extending through the adjacent spaced apart channels.

A vacuum dome as claimed in any of claims 8 to 13 wherein the dome defines a generally rectangular opening from the inside edge of which the internal surface extends, a plurality of apertures are spaced over the internal surface in a substantially regular rectangular array, first channels are formed along substantially parallel first rows of apertures in the array and second channels are formed along substantially parallel rows of apertures in the array in a direction substantially at right angles to the first rows of apertures, some or all of the second channels intersecting some or all of the first channels.

A vacuum dome as claimed in any of claims 8 to 14 wherein the or each channel comprises an arcuate surface.

Skin packing apparatus comprising a vacuum dome as claimed in any preceding claim.