Mixing head, especially for reactive components such as those in thermosetting synthetic resins

A mixing head for at least two flowable components, comprising:

• housing means including means defining an internally located axially extending bore, means defining at least one pair of inlet ports opening into said bore transversely and connected to respective sources of said components, means defining at least one pair of return ports opening into said bore at a location axially spaced from said inlet port means, said return ports being connectible to respective reservoirs of said components and means defining an axial outlet located at the downstream end of said bore means for discharge of a mixture of said components delivered by said inlet ports;
• means forming an elastic wall along said bore and having a variable inner diameter;
• a control plunger axially shiftable in contact with said wall between a first position wherein said mixture is expressed through said outlet and a second position wherein said plunger is retracted from said outlet and said inlet ports open into a mixing chamber formed within said wall between said plunger and said outlet, said plunger being formed with a pair of bypass passages angularly spaced apart around said plunger and axially extending to connect each inlet port with a respective return port in said first position of said plunger, the elastic wall bearing upon said plunger between said passages for sealing said components against mixture between said plunger and the wall, said means forming said wall including a thin-walled elastic sleeve received in said bore, said housing means being formed between said passages with at least one pressurizable compartment closed by said sleeve, and
• means for pressurizing said compartment to deform said sleeve against said plunger at least between said return ports.