Pressure fastening system for joining the edges of plastic films.

The present invention relates to a device of the type snap closure to bring the longitudinal edges of two sheets in plastic kits, or both longitudinal edges of a sheet of plastic formed into tubular sheath.

Have long been known many types of closures to pressure, for example in sacks or bags of plastic sheets, and having means engaging, generally one or more cooperating hooks, closing and opening being obtained by engagement and disengagement respectively, hooks, usually by means of a cursor.

In some cases, the fastening means are made integrally with the plastic sheet forming the bag and in other cases the attachment means are formed on a profiled strip having a heel in the form of sailing, generally fixed by heat sealing, the sheet of plastic corresponding. In some cases (e.g. GBA 642 636), the lug has a reinforcing bead at its end.

It has sought to use such bands shaped to achieve closures pressure for joining webs of plastic or comply as tubular sheaths a sheet of plastic, for example to achieve a thermal insulation sheath piping.

Is fixed to this end, for example heat sealing a strip profiled in the vicinity of each of the binding edges of the web or, in the case where one seeks to bring together two or more plies, along the longitudinal edges to bring together successive layers, the meeting edges being carried by interengaging fastening means of profile strips.

Experience shows, however, that in the case of relatively thick webs and / or made of cellular plastic, it is found deformations of surface of the web of the profiled strip heat sealed adjacent the edge of the longitudinal web, this which results in folding and a little solid fixing of the profiled strip on the corresponding web.

The present invention proposes to avoid a particularly simple and economic means such drawbacks.

The present invention is characterized by the fact that the web of the profiled strip has at least one intermediate longitudinal rib projecting from one face of the web formed between the hooking means and the end of the sail.

In addition to this or these intermediate ribs, the veil may comprise a rib projecting end of one of its faces.

In a preferred embodiment, the rib or ribs are arranged on the side of the web opposite to that fixed on the web.

It is however possible within the scope of the invention to fix the curtain on the web corresponding with the rib or ribs in contact with the web. It is also possible to mount the profile strips to assemble one with his or her ribs in contact with the surface of the water, the other with his or her ribs facing away. This latter embodiment allows to use the same band contoured to achieve the two sides of the closure and n'exige therefore only die extrusion for making the tape.

The experiments carried out by the company Applicant have shown only with the ribs on the veil, is obtained when welding hot band profiled on the corresponding table a bonding surface very solid, no warping or puckering significant at the sail.

It is believed that this good result is due to the fact that the thickenings materialized by the longitudinal ribs have the effect better distribute the heat applied when welding in the entire sail.

In order to better understand the invention, will now be described in no way limited, an embodiment with reference to the accompanying drawings in which: - Figure 1 illustrates a plastic web provided at its both longitudinal ends of profiled strips carrying the closure device according to the invention, - Figure 2 illustrates the web of Figure 1 shaped tubular sheath.

Illustrated in Figures 1 and 2 show a possible application of the device for closing according to the invention for producing such sheaths tubular thermal insulation capable of being set in place around pipes for example heating or cooling. To this end, is fixed along each longitudinal edge of a sheet of plastic 1, a profiled strip 2<u>at</u> and 2 respectively<u>b</u>, Each of the profiled strips comprising means for attachment 3<u>at</u> and respectively 3<u>b</u>. In the example illustrated, each hooking means 3a and 3b is constituted as conventional by a set of three ribs of which two ends having hook-shaped, cooperating during the application of pressure, as shown in Figure 2, to achieve the interlocking profiled strips 2a and 2b.

Each of the profile strips has for its fixing by heat sealing on the sheet 1 a thin veil 4a, 4b respectively and having in the illustrated example each one longitudinal rib projecting intermediate 5a and 5b respectively, and a rib end 5'a and 5'b, respectively.

In the example illustrated, the two profiled strips are not identical such that the ribs of the two strips when the latter are secured to the sheet 1, are all facing away from the surface of the web attached to the tablecloth.

It would however have replaced the band 2b contoured by a band shaped identical to the band 2a which case the ribs of one of the bands have been in contact with the table.

The profiled strips for the embodiment of the device snap closure may be made of any suitable material, eg polyethylene, polypropylene or PVC.

In the example shown, the webs 4a and 4b of the two profiled strips have a thickness of 3 / 10ths of a millimeter, each of the ribs 5a, 5'a, 5b, 5'b having a thickness of about 1 mm, and each of the webs having a width 10 mm.

While the invention has been described in connection with a particular application, it is obvious that it is in no way limited and which can for example be implemented for two or more layers of protection meeting the meeting of wall formwork, the meeting plies constituting elements covers, tarpaulins, etc ...