Patent ID: 7753103

Claim:
A method of casting a vented rotary friction plate having a central hub portion and pair of circumferentially continuous, radially extending friction plates carried on the hub with friction faces that face opposite of one another, said method comprising: preparing a casting core having an upper surface, an annular wall portion projecting upwardly from the upper surface in surrounding and radially outwardly spaced relation to a central opening in the core to provide a cup-shaped primary distribution reservoir on the top of the core around the central opening, a plurality of circumferentially spaced secondary distribution reservoirs disposed radially outwardly of the wall, and a vent forming disc portion radially outward of the wall portion and formed with a plurality of holes; preparing a metal casting mold having a mold cavity configured to form the rotary friction plate and including a central sprue extending down into the mold cavity from above along a central axis of the mold cavity; mounting the core in the casting mold with the central opening aligned axially with the sprue, and with the top wall of the core in spaced relation to an upper wall of the cavity to keep the primary distribution reservoir open and to cooperate with the wall and to provide a plurality of circumferentially spaced choked openings in the wall leading to the secondary distribution reservoirs, and with the vent forming disc portion positioned in the cavity to provide an upper friction plate region of the mold cavity and a lower friction plate region of the mold cavity, and providing a hub forming region of the mold cavity, and with the wall of the cavity further cooperating with the core to provide a plurality of circumferentially spaced choked inlets leading from the secondary distribution reservoirs into the upper friction plate forming region; introducing molten metal into the sprue whereupon the metal flows across the upper surface of the core into the primary distribution reservoir, through the plurality of choked openings and into the plurality of secondary distribution reservoirs, and then through the plurality of choked inlets and directly into the upper friction plate forming region of the cavity where the molten metal begins to fill the upper friction forming region while some of the molten metal flows downward through the plurality of holes in the vent forming portion to begin filling the lower friction plate forming region and the hub forming region from above.