FR2497497A3 - Flexible plastic bags have stiffened base - obtd. using thermoplastic coated panels which are easily inserted and anchored by local welding - Google Patents

Abstract

A sheet insert for stiffening a flat base within a flexible plastic bag is coated with a fusible thermoplastic matl. compatible with that of the bag, e.g. polyethylene, so that the insert can be fixed in position by localised welds. The insert may be of e.g. stiff card. Simpler to assemble than use of overlapping ancillary folds to hold the base in place.

Description

 The present invention relates to a plastic bag with a flat bottom.

 Currently known plastic bags consisting of two walls arranged face to face, joined along their vertical sides by parts folded in bellows, and provided at the base, closed, a stiffening frame capable of rendering the bottom of the flat bag.

Said bags are generally made from a tubular film of heat-sealable plastic material, cut to measure and closed at one end by welding, once the said walls and said side bellows have been folded. At the opposite end, the bags are moreover provided with a handle which commonly also forms a closure device.

 The stiffening frame of the bottom has a generally rectangular shape and is made in most cases of a material of the type of a cardboard. Said frame is introduced inside the bag and fixed to the bottom of the latter by gluing or tabbing, that is to say insertion under tabs formed on said bottom by folding the side parts with bellows.

 This technique of producing the flat bottom of the bag turns out to be rather complex and has significant effects on the cost of the product.

 The object of the invention is to design a plastic bag with which the production of the flat bottom is particularly simple.

 Said objective is achieved according to the invention, by a plastic bag with a flat bottom, of the type which comprises two walls arranged face to face, joined along their vertical sides by folded bellows portions, and at the base by a continuous welding line, and a flat rectangular reinforcement for stiffening the bottom of said bag, said bag being characterized in that said stiffening reinforcement has at least its lower face coated with a plastic film or film so that once introduced inside the bag, said frame is suitable for additionally made securely attached to the bottom thereof by thermal welding.

Other characteristics and advantages of the invention will emerge more clearly from the following detailed description of a preferred embodiment of the plastic bag with a flat bottom, given by way of indicative example, but in no way limiting, with reference to the drawings. annexed, in which:
Figure 1 shows a perspective view, partially broken away, of the bag of the invention; and
Figure 2 shows on the other hand, also in perspective and in a partially cut away view, the bottom of said bag.

 With particular reference to said figures, it can be seen that a bag made of plastic material, of the polyethylene type, is generally indicated by 1, in which there is a pair of walls 2 arranged face to face and joined along their vertical sides by bellows folded parts 3. The upper end of the bag is open and has a handle 4 of any shape, while at the other end, the bag is closed by a continuous welding line 5, which determines a kind of edge 5a facing outwards. The folding of the lateral bellows parts 3 also determines the formation at the base of these, of triangular tongues which are turned on the bottom, towards the interior of the bag.

 This bottom is stiffened and made flat by a frame 7 of rectangular shape, made of a rigid material of the type of a cardboard. The frame 7 has at least its lower face 7a coated with a plastic film, of the polyethylene type.

 I1 is therefore possible, once the armature 7 introduced on the bottom of the bag, to fix it stably on said bottom by means of a pair of sections 8 of thermal welding, lateral to the edge 5a.

 The problem of fixing the frame, necessary to make the bottom of the bag flat, is in this way solved in a particularly simple manner, all to the advantage of the economy of the product.

 Naturally, the welding sections 8 can be replaced by a dotted or continuous weld, while the upper face of the frame can be, moreover, raw or metallized or else itself coated with plastic.

 In the implementation of the invention in practice, the materials, as well as the shapes and the dimensions can be any according to the requirements without departing from the scope and the spirit of the said invention.

Claims (2)

 1. Plastic bag with flat bottom, of the type which comprises two walls (2) arranged face to face and joined along their vertical sides by folded bellows portions (3), and and at the base by a line of welding (5) continuous, and a frame (7) of rectangular flat shape for stiffening the bottom of said bag, said bag being characterized in that said stiffening frame (7) has at least its lower face (7a) coated with a film or plastic film so that once introduced into the bag (1), said frame (7) is capable of being made stably secured to the bottom thereof by thermal welding (8) .  2. Bag according to claim 1, characterized in that said plastic coating of the stiffening frame (7) is made of a material of typepdLyethylene, this same material can also be used to make said bag (1) itself .