Self-purging screen changer and strainer plate

Claim 2

In combination, a strainer plate for a screen changer having a slot through which said strainer plate is moved from a storage position to an operating position in an opening for straining extruded material, said strainer having a leading edge, a trailing edge, a central strainer portion, a supporting portion surrounding said strainer portion, said supporting portion having a surface in sealing engagement with a sealing plate on said screen changer, a groove in said surface extending in a direction from said leading edge to said central strainer portion, said groove being closed by said sealing plate when said strainer is in said storage position and said groove being open and in communication with said central strainer portion and said opening in a preliminary change position of said strainer with said strainer moved a predetermined distance from said storage position towards said operating position for prefilling said central strainer portion in the storage position and venting air out of said central strainer portion prior to movement of the strainer from said preliminary change position to said operating position.

Claim 3

The combination of claim 1 wherein said central strainer portion is recessed at the surface opposite to said surface of said supporting portion containing said groove to provide a vent space at said central strainer portion for venting air out of said strainer.

Claim 4

The combination of claim 1 wherein the distance from the ends of said groove to said leading edge is less than the length of said groove.

Claim 5

The combination of claim 1 wherein said central strainer portion includes a recess for a screen and a central reinforcement having a plurality of holes for conveying extruded material through said strainer and said recess being on the same side of said strainer as said surface of said supporting plate containing said groove.

Claim 6

The combination of claim 1 wherein said opening in said screen changer is circular and said central strainer portion is circular to conform with said opening.

Claim 7

The combination of claim 1 wherein said strainer plate is rectangular with a trailing edge at the opposite side from said leading edge and a second groove located in the surface of said supporting plate between said central strainer portion and said trailing edge.

Claim 8

In combination, a screen changer having a storage area for storing a replacement strainer plate in a storage position, an opening for conveying extruded material, a slot extending from said storage area to said opening, a sealing plate at one side of said slot for sealing engagement with said strainer plate, a groove in the surface of said sealing plate extending in a direction between said storage area and said opening, said groove being in communication with a central strainer portion of said strainer plate and said opening in a preliminary change position of said changer with said replacement strainer plate moved a predetermined distance from said storage position towards said opening and vent means in said storage area for venting air out of said central strainer portion prior to movement of said strainer to an operating position covering said opening.

Claim 9

In combination, a screen changer having a storage area for storing a replacement strainer plate in a storage position, an opening for conveying extruded material, a slot extending from said storage area to said opening, a sealing plate at one side of said slot for sealing engagement with said strainer plate, a groove in the surface of said sealing plate extending in a direction between said storage area and said opening, said groove being in communication with a central strainer portion of said strainer plate and said opening in a preliminary change position of said changer with said replacement strainer plate moved a predetermined distance from said storage position towards said opening and vent means in said storage area for venting air out of said central strainer portion prior to movement of said strainer to an operating position covering said opening.

Claim 10

The combination of claim 7 wherein said storage area has a removable cover plate for removal during insertion of said strainer plate into said storage area and said cover plate includes vent means for releasing air from said central strainer portion.

Claim 11

The combination of claim 8 including ram means for moving said strainer plate from said storage position to said operating position covering said opening.

Claim 12

The combination of claim 7 wherein said sealing plate has a second screen changer groove extending in the same direction as said first groove and the distance between said first and second grooves is less than the length of said grooves.

Claim 13

In combination, a screen changer having a storage area, a replacement strainer plate in a storage position in said area, an opening for conveying extruded material adjacent said storage area, a slot extending from said storage area to said opening and said strainer plate being slidably mounted in said slot, said strainer plate having a central strainer portion and a supporting portion surrounding said strainer portion, a sealing plate on one side of said slot, said supporting portion of said strainer plate having a surface in sealing engagement with said sealing plate, a strainer groove in said surface of said supporting portion extending in a direction between said storage area and said opening, a sealing plate groove in the surface of said sealing plate extending in the same direction as said strainer groove, said strainer groove and said sealing plate groove being in communication with said opening and said central strainer portion in a preliminary change position of said screen changer with said strainer plate moved a predetermined distance from said storage position towards said opening to convey extruded material to said central strainer portion and vent means in said storage area for venting air out of said central strainer portion prior to movement of said strainer plate from said change position to a position covering said opening.

Claim 14

In combination, a screen changer having a storage area, a replacement strainer plate in a storage position in said area, an opening for conveying extruded material adjacent said storage area, a slot extending from said storage area to said opening and said strainer plate being slidably mounted in said slot, said strainer plate having a central strainer portion and a supporting portion surrounding said strainer portion, a sealing plate on one side of said slot, said supporting portion of said strainer plate having a surface in sealing engagement with said sealing plate, a strainer groove in said surface of said supporting portion extending in a direction between said storage area and said opening, a sealing plate groove in the surface of said sealing plate extending in the same direction as said strainer groove, said strainer groove and said sealing plate groove being in communication with said opening and said central strainer portion in a preliminary change position of said screen changer with said strainer plate moved a predetermined distance from said storage position towards said opening to convey extruded material to said central strainer portion and vent means in said storage area for venting air out of said central strainer portion prior to movement of said strainer plate from said change position to a position covering said opening.

Claim 15

The combination of claim 11 wherein said sealing plate has a second sealing plate groove extending in the same direction as said first groove and located between said first sealing plate groove and said opening, an operating strainer plate in said opening for straining extruded material having a central strainer portion extending over said opening and a supporting portion surrounding said central strainer portion, said supporting portion of said operating strainer plate having a surface in sealing engagement with said sealing plate and a strainer groove in said surface extending in a direction between said storage area and said opening, said second sealing plate groove and said strainer groove in said surface of said operating strainer plate being in communication with said opening and said central strainer portion of said replacement strainer plate in said preliminary change position of said screen changer with said operating strainer plate moved said predetermined distance from said opening away from said storage area.

Claim 16

The combination of claim 12 wherein said operating strainer plate has a leading edge and a trailing edge, said replacement strainer plate has a leading edge and trailing edge and said leading edge of said replacement strainer plate being in engagement with said trailing edge of said operating strainer plate, ram means in engagement with said trailing edge of said replacement strainer plate for moving said operating strainer plate and said replacement strainer plate.

Claim 17

The combination of claim 13 wherein the distance between said grooves is less than the length of the grooves and the distance between the edge of the central strainer portion and said strainer grooves is less than the length of said strainer groove whereby a passage from said opening through said grooves to said central strainer portion of said replacement strainer plate is provided to convey extruded material from said opening to said central strainer plate in said preliminary change position of said screen changer.