Slide fasteners

A slide fastener has a coating of waterproof plastics material formed by extrusion onto the closed fastener. The slide fastener comprises two woven elongate stringers, each having a series of spaced locking members which interlock when the fastener is closed, and coating which encloses the fastener and includes a longitudinally slit projection formed on each side of the locking members. The fastener has improved waterproofing as the fastener is fully enclosed by the plastics material when it is closed, and the plastics material moulds itself round both sides of the locking members. To be accompanied, when published, by FIG. 1 of the drawings.

FIGS. 1 and 2 show a waterproof slide fastener 1 . The fastener 1 comprises two elongate stringers 2 , 3 of woven material, each stringer 2 , 3 having a series of spaced locking members in the form of teeth 4 , which interlock when the fastener 1 is closed. The stringers 2 , 3 and teeth 4 have an extruded coating 5 of waterproof plastics material, the coating 5 enclosing the whole fastener, extending beyond the stringers 2 , 3 and including a longitudinally slit projection 6 , 7 formed on each side of the locking teeth 4 . The slit 8 in each projection 6 , 7 enables the fastener 1 to be opened and closed by means of a conventional slider (not shown). The adjacent edges 9 , 10 of each slit 8 abut when the fastener 1 is closed and flat, to provide a seal against moisture. If the fastener 1 is twisted or flexed so as to open up one of the slits 8 , the other slit 8 will be compressed, thus ensuring that a seal is maintained. Extrusion of the coating 5 ensures that the plastics material fills the gaps between the teeth, which also helps with the sealing properties of the projections 6 , 7 . The waterproof plastics may for example be Dupont's Hytrel (RTM), a polyester, or a polyurethane or the like. The fastener 1 is made using the apparatus shown schematically in FIG. 3 . FIG. 3 shows a cross-head extruder 11 , and a slitting tool 12 having two opposed cutting blades 13 . A slide fastener 1 of conventional construction, with the two stringers 2 , 3 having locking teeth 4 is pulled through the die of the extruder 11 , which applies the plastics coating 5 , including the projections 6 , 7 which are formed without the slits 8 . The plastics material is allowed to cool and harden, and is then passed through the slitting tool 12 , where the cutting blades 13 cut the slits 8 in each projection 6 , 7 . In a modification, a further processing step is carried out following the slitting tool 8 . to enhance the seal between abutting edges of each slit 8 . This step is carried out by a heating and pressure-applying tool 14 , through which the fastener 1 passes. The tool 14 firstly heats the top surface of each projection 6 , 7 at at least one edge of each slit 8 and then applies pressure to the heated edge by a roller 15 , to deform the edge slightly, biassing it towards the other edge. After passing through the tool 14 the fastener 1 is allowed to cool, and the deformed edge provides an enhanced seal for the slit 8 . It will be appreciated that the slider used to open and close the fastener, and any end stops for it will also need to be waterproofed. In the embodiment illustrated the locking teeth 4 are separate members crimped or moulded into an edge of each stringer 2 , 3 . It is also known for the locking members to be formed from a spiral member, and fasteners with this type of locking member can also be waterproofed in accordance with the invention. The slide fastener according to the invention is particularly useful for tents, as well as clothes and bags that need to be waterproof.