a rotary feeder feeds sheets or board - like articles to nip rolls in a box - making machine . the boards are successively and individually fed from the bottom of a stack whose forward edge engages a gate below which the boards are fed by driven feed members such as wheels , rolls or endless belts which engage the underside of the lowermost board . to raise and lower the boards relative to the surface of the feed members , a vertically reciprocable grate is provided between the drive members . the grate and drive members are mounted in a vacuum box in which a vacuum is established to hold the boards in proper position on the feed members when the grate is lowered . the vacuum is also utilized to hold the boards with sufficient force to produce necessary friction between the boards and the feed members for feeding . the feed members are driven through an oscillating rocker shaft and gearing in two opposite directions , one of which serves to convey the boards below the gate to the nip rolls and the other of which serves to relieve pressure of the board against the gate prior to conveyance to the nip rolls . the grate is actuated through oscillatable shafts connected to the grate and driven from a cam and cam - follower assembly which , in turn , is driven from a crank gear that is also employed to drive the rocker shaft through a linkage or quick return slide mechanism . a latch device is also provided to releasably hold the grate in raised position above the feed members to interrupt the feeding operation .