Injection molding machine for producing slide fasteners

Claim 1

An injection molding machine for fabricating sliding fasteners, especially zippers, by injecting molding closure elements onto support bands in a bipartite mold, comprising: a bipartite mold, means for opening and closing said mold, an injection molding unit for injection molding material into said mold, a band feed mechanism for feeding support bands through said mold, said band feed mechanism comprising a to-and-fro movable band clamping mechanism provided with clamping elements and arranged in the band feed direction after the mold, pneumatically actuated means for displacing said to-and-fro movable band clamping mechanism, means for selectively opening and closing said clamping elements, stop means cooperating with said band clamping mechanism; said band clamping mechanism being synchronously controlled with the opening and closing movement of the mold in such a manner that when the mold is open the clamping elements fixedly clamp the support bands at the region of the mold, the clamping mechanism is then advanced in the feed direction until reaching said stop means in order to draw the support bands with the closure elements molded thereon out of the mold and to draw a new length of band into the open mold, upon impact of said clamping mechanism against said stop means the clamping elements release the support bands, and then the clamping mechanism is again retracted towards the mold and in its terminal position upon closing of the mold the clamping elements again fixedly clamp the support bands; said clamping elements comprising a relatively stationary clamping element and a clamping element movable with respect to the stationary clamping element and cooperating therewith, the support bands being guided between and through both clamping elements, said displacing means comprising guide rod means along which move said clamping mechanism, piston rod means for connecting said clamping mechanism with pneumatically actuated piston means for moving said clamping mechanism to-and-fro between said stop means and the mold; said movable clamping element being provided with a pressure compartment closed by a diaphragm, means for supplying compressed air to said pressure compartment, slide valve piston means for controlling connection of said pressure compartment with said compressed air supplying means, and venting channel means; so that when the clamping mechanism has reached the end of its stroke at the region of the mold and said piston means is impinged in order to displace the clamping mechanism in the feed direction against the other end of the stroke, said slide valve piston means opens connection of the compressed air supplying means to said pressure compartment in order to press the diaphragm against the movable clamping element and to displace said movable clamping element against the fixed clamping element for the purpose of fixedly clamping the support bands, whereas at the other end of the stroke of the clamping mechanism, said slide valve piston means impinges against said stop means and the pressure compartment is connected with said venting channel means to release the support bands.