Screen changer apparatus

A screen changer assembly for screening out particulate matter in a flow of fluid comprising:

• a support of generally tubular shape comprising means defining an interior fluid flow path and a perforate wall enclosing said interior flow path means;
• a screen having a mesh size sufficient for preventing the particulate matter from passing therethrough and configured substantially as a closed tube and surrounding said support and supported on its exterior surface thereby for permitting the flow of the fluid through said screen, said perforate wall means and said interior flow path means, while screening out the particulate matter;
• and
• means directing the flow of the fluid with generally unidirectional rotation about said screen for minimizing clogging of said screen.

A screen changer assembly for use in an extruding apparatus of fluid plastic material having an extruder and a die, comprising:

• a housing having an inlet and an outlet for providing a path of flow of the fluid plastic material;
• means defining a screen and support therefor in said housing and in the path of flow of the fluid plastic material for screening out any particulate material therein of predetermined size;
• and
• means in and cooperable with said support means and at least one of said inlet and said outlet of said housing for exerting a milling pressure of the fluid plastic material in the extruder.

A screen changer assembly for screening out particulate matter in a flow of fluid comprising:

• a screen having a mesh size sufficient for preventing the particulate matter from passing therethrough and configured substantially as a closed cylindrical tube;
• a support of substantially cylindrical shape coaxially centered with said screen on an axis and supporting said screen, said support comprising means defining an interior flow path, a wall enclosing said interior flow path means, and means extending through said wall defining a plurality of openings, thereby for permitting the flow of the fluid through said screen, said openings means and said interior flow path means, while screening out the particulate matter;
• a housing surrounding and supporting said support and said screen;
• and
• means defining an inlet in said housing positioned adjacent to said screen and said support and offset from the axis for directing the flow in a generally unidirectional rotational flow pattern about and over the exterior surface of said screen, thereby for enabling screening of the fluid through the entire cylindrical surface of said screen and for flowing of the fluid through said openings means in said support wall, while continuously moving the particulate material about the exterior surface of said screen for minimizing clogging thereof by the particulate material.

A screen changer assembly for use with and coupled to an extruder for screening out particulate matter in a flow of plastic material, including:

• at least two screens each having a mesh size sufficient for preventing the particulate matter from passing therethrough and configured substantially as a closed tube;
• a housing having means therethrough defining a threaded cylindrical bore having an axis, and means defining an inlet to and on outlet from said bore means for flow of said plastic material through said housing, said inlet means having an axis offset from intersecting with the bore axis for imparting a generally unidirectional rotational flow of said plastic material into and around said housing bore means, and said outlet means being spaced from said inlet means along the bore axis of said housing;
• a plug having an axis coaxial with the bore axis of said housing and comprising at least three cylindrical portions having threaded external surfaces for engaging said threaded cylindrical bore means of said housing and for enabling rotation and axial movement of said plug in said housing, said cylindrical portions being spaced from one another with adjacent ones thereof integrally joined together respectively by perforate tubes of lesser diameter than that of said cylindrical portions, said perforate tubes each having an interior flow path and a generally tubular shape for supporting each of said screens;
• and
• all of said cylindrical portions but one each having
• means therein defining an interior cavity having a closed inclined end and coupled with and forming an extension of said interior flow path means of said perforate tube,
• means defining a bore extending at an angular inclination to the plug axis in communication with said interior cavity means at said closed inclined end and through said threaded external surface for enabling communication with said housing outlet means, and
• means defining an annular groove formed in said threaded external surface and communicating with said bore means for providing a pressure relief for said plastic material when said bore means is not in communication with said housing outlet means;