A vacuum forming apparatus for fixing and shaping animal tissue into the shape of a cardiac valve prosthesis, including a tapered form, with elongated through apertures, suspended in a reservoir of fixative and vacuum means for producing a reduced pressure within the tapered form....http://www.google.de/patents/US4758151?utm_source=gb-gplus-sharePatent US4758151 - Apparatus for manufacture of valve flaps for cardiac valve prostheses
