Accordingly, there is a requirement to provide a reclosable package which enables the bag to be closed and substantially re-sealed each time after some of the product has been removed from inside the bag.

Many attempts have been made recently to provide re- closable bags for such purposes. One of the well known ways is to provide so called"zipper strips"which are interlocking extruded plastic strips applied to the open neck of the bag to enable the opposite sides of the bag to be snap-fitted together. Subsequently the zipper strips can be re-opened by pulling the neck of the bag apart and then re-closed by squeezing the zipper strips together by, for example, the user running their finger and thumb along the length of the zipper strips. Usually the open neck of the bag also includes thickened strips to provide finger- gripping portions to enable the interlocking strips easily to be separated and an outer heat seal completely to seal the bag before it is first opened. One of the difficulties with this type of bag is that the user often removes or damages the interlocking zipper strips whilst

initially cutting away the top heat sealed portion during initial opening of the bag.

Another technique that has come into use recently is to provide a reclosable, self-adhesive flap at the top open neck of a bag so that, after some of the contents have been emptied, the top of the bag is folded over the side of the bag and then the self-adhesive flap is adhered to the side to enclose the remainder of the contents. Another similar technique is to provide a strip of self-adhesive tape fixed to the outside of the filled bag which can be peeled off and then subsequently used to adhere the folded down open neck of the bag to its side wall to reclose it. Both of these arrangements suffer from the contents of the bag tending to stick to the self-adhesive strip whilst materials are removed from the bag so reducing the adhesive effect of the self-adhesive strip and wasting the commodity contained in the bag.

It is also known to provide plastics snap together clamps known by the trade name of"Klippits"RTM for clamping together the open end of a neck of a partially used bag. Such snap together clamps are re-usable but tend to get mislaid and may not be to hand when the bag is opened. It also has to be remembered to remove them before discarding the empty bag. More recently it has also been proposed to form the neck portion of a plastics bag from a different material which is less resilient than the remainder of the bag so that the top of the bag can be rolled over or scrunched together and, once rolled over or scrunched together retains this shape so holding the bag closed.

Thus, whilst there are plenty of ideas on how to make a paper or plastics bag reclosable so that it can safely store its part-used contents in a reasonably air-tight manner, none are cheap, simple and convenient to use by the consumer.

SUMMARY OF THE INVENTION According to this invention a reclosable paper or plastics bag includes towards its closed end a strip of elastic fixed to the bag only at its ends, the elastics strip having a length and an extensibility sufficient to enable it to be stretched to make a turn around the longest dimension of the bag when filled.

Preferably the present invention is used by rolling up or folding over the top of a filled bag after part of the contents have been used and then pulling the elastics strip away from the bag and looping it around at least part of the longest dimension of the bag to hold the rolled over top closed. In this way the rolled or folded over top of the bag, whilst formed from inherently resilient material is held into its rolled or folded over and substantially sealed configuration by the loop of elastic. When further contents of the bag are required, it is straightforward merely to release the loop of elastic from around the top of the bag, pour out or spoon out further contents from the bag, roll or fold over the top once again and then reclose it using the elastic strip. During material removal the elastic strip is remote from the neck ùL the bag and so does not interfere in any way with the removal of further contents from the partially filled bag nor do the contents adhere to it. The present invention thus securely closes the package and maintains a reasonably air-tight seal as a result of holding the rolled over or folded over top of the bag in its closed position even though the dimensions of the bag reduce with each additional portion of the contents being removed.

The elastic strip may extend substantially in the direction of the longest dimension of the bag. In this case, in use the elastic strip may be stretched from one side of the bag, over the top and bottom and extend along the other side of the bag so that it is formed into a C- shape. Alternatively, the elastic strip extends

transversely to the longest dimension and, in this case, the strip is pulled away from the bag, twisted upon itself to form a loop and then the loop placed around the bag to encompass both the base and the rolled or folded over top, with the strip making a full turn around the bag.

As the contents of the bag are removed it may be desirable to wind the elastic strip more than one full turn around the bag to ensure that there is sufficient tension in the elastic strip to hold the rolled or folded over top of the bag securely.

The bag may be a plastics bag made from PVC, polyethylene, polypropylene or any other thermoplastics film or a combination of these or a bag made of plain or coated paper or a laminate. The plastics material of the bag or plastics/paper laminate may also have an evaporated metallised coating to enhance its protective nature and/or be formed by a laminate of plastics and metal sheets.

The elastic strip may be fixed to the base or be fixed to or form part of the heat seal of a plastics bag or it may merely be attached to a side wall portion of the bag, preferably adjacent the base. Preferably the elastic strip is not under a significant tension when initially attached to the bag and preferably it is under so little tension that it does not tend to crumple up the bag whilst, at the same time, not drooping under its own weight away from the surface of the bag. To enable the elastic strip to have a sufficient extension to make a complete loop around the longest dimension of the bag when filled, it is preferred that it is able to accommodate an extension of around 800%.

The elastic strip can be made from any material of high elasticity and low plasticity such as natural or synthetic rubber or thermoplastic elastomer. These include vulcanised natural rubber; synthetic polyisoprene; synthetic nitrile polymers; ethylene propylene diene rubber (EPDM) based polymers; Lycra (Registered Trade Mark) a thermoplastic elastomer made by E. I. du Pont de Nemours and Company of 1007 Market Street, Wilmington, Delaware 19898,

USA; and polybutadiene polymer. To be suitable for long term use the elastic material should be formulated to avoid ozone stress cracking by incorporating additives like waxes such as Negozone (RTM) wax made by Dussek Campbell of the UK, chemicals such as Antiozonat AFD (RTM) made by Bayer of Germany or EPDM based polymers such as Royalene 505 (RTM) made by Uniroyal of the USA.

When the elastic strip is merely mounted on the outside of a bag it never comes into contact with the contents of the bag and accordingly it is not necessary to provide a particularly high grade of elastic material.

Nevertheless, when the bag is intended to contain food, it may still be preferred to provide a"food grade"elastic material that has been accepted as being satisfactory for contact with food because all its ingredients meet the Food and Drugs Administration (FDA) list 177.2600 of ingredients for use in rubber products which come into contact with foods. This is especially preferred when the bag is to be filled with food material and there is some possibility of the food contacting the elastic strip material, for example, as a result of ends of the elastic strip material being present on the inside of the bag in some constructions.

The elastic strip may be fixed at its ends by trapping it, or welding it in seams forming the side edges of the bag or a heat sealed base of the bag and, in either of these cases the ends of the elastic strip may be trapped in a folded over hem. Preferably however the strip is merely adhered or welded at its opposite ends to the bag. In this case it may be welded or adhered to the outside surface of the sheet from which the bag is formed, to the outside surface of the bag during the formation of the bag or to the outside surface after the bag is filled with the product. Thermoplastic elastomers are suitable for attachment, by heat sealing or ultrasonic welding to plastics materials and natural and synthetic rubbers may be attached to plastics materials or to paper based materials

by a hot melt adhesive of the reactive or rubbery elastomer type such as that known as Dispomelt RTM 322 made by National Starch and Chemical Company of 10 Findern Avenue, New Jersey, 08807-3300, USA.

Especially where the elastic strip is attached by welding it is convenient to attach it to the plastics bag as part of the formation of a heat seal on the base of a bag or on a longitudinally extending heat seal extending from the top to the bottom of the bag. In this case an aperture may be provided in the bag material forming at least part of the heat seal and the elastic strip span the aperture so that its ends are welded to the bag in the heat seal but its middle portion is exposed in the aperture so that it can be grasped by a user and formed into a loop around the bag. Alternatively the elastic strip may be located behind a folded longitudinally extending heat seal.

This protects the elastic strip during handling of the resulting package and prevents it being"caught"during transport and movement of the package whilst the elastic strip is still readily accessible to the user of the bag.

BRIEF DESCRIPTION OF THE DRAWINGS Three examples of a bag in accordance with this invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a perspective view from the front, one side and below a first example of filled bag; Figure 2 is a perspective view from front, below and one side of the first example of bag when reclosed after part of its contents have been used; Figure 3 is a side elevation of a second example of filled bag; Figure 4 is a side elevation of the second example of filled bag when part of its contents have been removed; Figure 5 is a perspective view from the front, one side and below a third example of filled bag; and,

Figure 6 is a perspective view of the third example of bag when reclosed after part of its contents have been used.

DESCRIPTION OF PARTICULAR EXAMPLE The first example of bag is a gusseted type of bag 1 having a substantially rectangular cross-section with a folded base 2 and a heat sealed top 3. A strip 4 of elastic material of vulcanized natural rubber and cross- section 0.3 x 3mm is adhered by a hot melt adhesive to the folded base.

To use the contents of the bag, the top heat seal 3 is cut away or, pulled apart and some of the contents removed. To reclose the bag the open top of the bag is then folded or rolled over as shown by reference numeral 5. The elastic strip 4 is then pulled away from the base 2, twisted upon itself to form a closed loop 6 which is then placed over the longitudinal extent of the bag to hold the rolled over top 5 closed as shown in Figure 2.

The second example of plastic bag in accordance with this invention is essentially a flat bag 10 having bottom and top heat seals 12 and 13. An elastic strip 14 of vulcanized natural rubber and cross-section 0.3 x 3 mm is fixed to the side wall of the bag adjacent its lower heat seal 14.

Again to use part of the contents of the bag the top heat seal 12 is manually pulled apart or cut-away and part of the contents removed. The open top of the bag is then folded or rolled over on itself as shown by reference numeral 15 and the elastic strip 14 pulled away from the bag and twisted upon itself to form a loop which is then used to wrap around the longitudinal extent of the bag to hold the rolled over top 15 of the bag closed as shown in Figure 4.

The third example of bag is a gusseted type of bag 21 having a substantially rectangular cross-section with a

folded base 22 and heat sealed top 23. A strip 24 of elastic material of vulcanized natural rubber and cross- section 0.3 x 3 mm is adhered by a hot melt adhesive to the outside of a longitudinally extending heat sealed seam 25.

The strip 24 may alternatively be attached to the underside of the seam 25 and so be hidden from view and, to some extent, be protected during handling of the package. In this case the strip 24 may be sandwiched, at least at its ends between the inside of the seam 25 and the side wall of the bag and attached to both. Also in this case the strip may extend along the entire length of the seam 25 and be attached at its ends in the heat seals at the top and bottom of the bag. However, instead of a natural rubber the strip 24 is preferably a thermoplastic elastomer to enable it to be attached by welding.

To use the contents of the bag the top heat seal 23 is pulled apart and some of the contents removed. To reclose the bag the open top is then rolled over as shown by reference numeral 26. The elastic strip 24 is then pulled away from the seam 25 and placed over the top and bottom of the bag and along the other side of the bag from the seam 25 to form it into a C-shape as shown in Figure 6. When more of the contents have been removed it is preferred to form the strip 24 into a full turn before placing it around the top and bottom of the bag.