Apparatus for producing thermoplastic tubing having interchangeable mold blocks

In an apparatus for producing thermoplastic tubing, the apparatus comprising a frame structure and a pair of complementary mold assemblies mounted thereon, each mold assembly comprising an endless chain of articulately interconnected mold units which are recirculated along an endless path defining a forward run and a return run, the mold units providing respective half molds cooperating in pairs along said forward run to define a longitudinally extending mold cavity, the improvement in which each mold unit comprises a rigid support member and a die member mounted thereon, the die member providing a plurality of transversely separated half molds, and said members providing respective interengaging guide means permitting transverse displacement of the die member for selectively moving the half molds thereof to a predetermined operative position, the apparatus further comprising selectively operable cam means mounted on said frame structure, said cam means being engageable with said die members along said return runs for displacing said die members thereby to bring the selected half molds thereof to the operative position, said frame structure further providing, for each mold assembly, a longitudinally extending guide member engaging said support members along the return run thereof, and a rigid support structure adjacent said guide member transversely spaced therefrom, said cam means comprising respective first cam means extending transversely from said die members, and selectively operable second cam means mounted on said support structure, said second cam means being selectively engageable with said first cam means for displacing said die members during such engagement.