Apparatus for conditioning a paper machine felt having a paper side and a back side, comprising a stationary air supply plenum chamber defined by a top wall and upstanding front, rear, and end walls and extending substantially the entire width of the felt in the cross machine direction, the plenum chamber having an open face which, in use, lies in confronting relationship with the back side of the felt, a plurality of rib members mounted across the open face between the front and rear walls of the plenum chamber for abutting the back side of the felt being conditioned, the rib members each having a curved felt-abutting surface lying along a given radius of curvature with respect to the open face of the plenum, the rib members being spaced from each other in the cross machine direction to define a plurality of air passages extending from the front wall to the rear wall of the plenum chamber so that the interior of the plenum chamber communicates with the back side of the felt thereby permitting air flow from the plenum chamber through the felt with minimum obscuration by the ribs, sealing means at the edges of the open face to abut the felt to prevent escape of air from the open face along the surface of the felt, and means for supplying conditioning air at a pressure of from 3 to 15 inches of Mercury (10 to 51 kPa) to the plenum chamber to flow therethrough in a direction substantially radially of the felt and for passing through the felt at a flow rate of from 7 to 25 ft 3/min/in2 (0.031 to 0.11 m3/min/cm2) of plenum opening to remove dirt and water from the felt. GBAB- GB2162558 B Apparatus for conditioning a paper machine felt having a paper side and a back side, comprising a stationary air supply plenum chamber defined by a top wall and upstanding front, rear, and end walls and extending substantially the entire width of the felt in the cross machine direction, the plenum chamber having an open face which, in use, lies in confronting relationship with the back side of the felt, a plurality of rib members mounted across the open face between the front and rear walls of the plenum chamber for abutting the back side of the felt being conditioned, the rib members each having a curved felt-abutting surface lying along a given radius of curvature with respect to the open face of the plenum, the rib members being spaced from each other in the cross machine direction to define a plurality of air passages extending from the front wall to the rear wall of the plenum chamber so that the interior of the plenum chamber communicates with the back side of the felt thereby permitting air flow from the plenum chamber through the felt with minimum obscuration by the ribs, sealing means at the edges of the open face to abut the felt to prevent escape of air from the open face along the surface of the felt, and means for supplying conditioning air at a pressure of from 3 to 15 inches of Mercury (10 to 51 kPa) to the plenum chamber to flow therethrough in a direction substantially radially of the felt and for passing through the felt at a flow rate of from 7 to 25 ft 3/min/in2 (0.031 to 0.11 m3/min/cm2) of plenum opening to remove dirt and water from the felt. - GB2162558 B Apparatus for conditioning a paper machine felt having a paper side and a back side, comprising a stationary air supply plenum chamber defined by a top wall and upstanding front, rear, and end walls and extending substantially the entire width of the felt in the cross machine direction, the plenum chamber having an open face which, in use, lies in confronting relationship with the back side of the felt, a plurality of rib members mounted across the open face between the front and rear walls of the plenum chamber for abutting the back side of the felt being conditioned, the rib members each having a curved felt-abutting surface lying along a given radius of curvature with respect to the open face of the plenum, the rib members being spaced from each other in the cross machine direction to define a plurality of air passages extending from the front wall to the rear wall of the plenum chamber so that the interior of the plenum chamber communicates with the back side of the felt thereby permitting air flow from the plenum chamber through the felt with minimum obscuration by the ribs, sealing means at the edges of the open face to abut the felt to prevent escape of air from the open face along the surface of the felt, and means for supplying conditioning air at a pressure of from 3 to 15 inches of Mercury (10 to 51 kPa) to the plenum chamber to flow therethrough in a direction substantially radially of the felt and for passing through the felt at a flow rate of from 7 to 25 ft 3/min/in2 (0.031 to 0.11 m3/min/cm2) of plenum opening to remove dirt and water from the felt. USAB- US4474644 A The papermaking felt (20) travels in a curved path over the curved open end of a plenum chamber (28) of curvature radius 2-5 in. The chamber (28) delivers air at 40-120 deg.F at between 3-10 p.s.i gauge, at a flow rate between 7-25 cfm per sq. in. of felt running over the open end of the plenum chamber. - The mouth of the plenum chamber is defined by an array of current spaced transverse ribs, across the mouth between its front and rear walls.