GB827951A - Improvements in or relating to sheet separating and forwarding machines - Google Patents

Abstract

827,951. Feeding sheets. BACKHOUSE, H. T. July 13, 1955 [July 14, 1954], No. 20544/54. Class 100(1) In apparatus for separating sheets one at a time from the top of a pile wherein an edge portion of each uppermost sheet is raised from the pile and the sheet is then transferred to a forwarding mechanism which advances the sheet for a short distance to move, or control movement of, the sheet over the pile and then returns to receive a further sheet, the forwarding mechanism comprises two or more suction grippers which move in succession around an endless path and engage successive sheets respectively. Sheet separators:- A single central separator means effecting the separation of the central portion of the rear edge of each uppermost sheet of a pile 20, Fig. 1, comprises a fixed air-blast nozzle 21, a flip 22 to arrest separation, a combined presser foot and air-blast nozzle 23, and a combined suction gripper 25 and stop 26. The gripper is of the "collapsing" type which, when sealed by a sheet 70 which is blown upwardly by the air-blast, collapses with an arcuate movement around an axis 28 which is the centre of the stop 26. The sheet is bent about the stop 26 at first, but when the gripper assembly is raised, the sheet is straightened somewhat by the engagement of a fixed roller 34 with a cam surface 36 fixed to the gripper cylinder 30. Sheet forwarders:- On each side of the central separator means there is a suction roll 40, Fig. 12, each in the form of a cylinder with two segments cut away to leave flat parallel faces 41 and rotatably mounted on a shaft 43, Fig. 17, fixed to an arm 44 which can be adjusted towards the pile. Each roll is chain-driven about its shaft 43, the shaft and a fixed member 64 thereon have air passages 66, 67 therein connected to a source of vacuum by a pipe 17, and radial air passages 62 are provided in the cylindrical surfaces of the roll, so that suction is established to the surfaces about to engage a lifted sheet 70. Air-blasts from the presser-foot 23 assist the rolls 40 to forward the sheet along the pile to a conveyer means. The following three modifications can be applied to sheet separating and forwarding apparatus as described in Specifications 427,041 and 774,874. In the first form (Fig. 19, not shown), there are two suction rollers each chain driven about a hollow shaft which is rocked towards and away from the pile by cam means, and each roller has three distinct groups of radial air passages therein communicating with the bore in the shaft. The bore in the shaft is connected to a source of vacuum. The suction rollers are lowered in timed relation with the separating means, and each group of air passages in turn forwards a sheet from the pile. In the second form, Fig. 20, near each corner of the pile 120 there is a forwarding gripper unit comprising a hub 121 rotatable on a hollow stub shaft carried on an arm 123 which is rocked towards and away from the pile by a cam 139. The hub has three radial hollow arms 125 each carrying a sucker 126 of the "collapsing" type. A ratchet-wheel 130 secured to the hub 121 has three teeth adapted to be engaged by a pawl 134 on a sprocket 132. A chain 135 secured to the free end of a pivoted lever 136, which is adapted to be rocked by a cam 137, passes over the sprocket and is secured to a return spring 138. The hub is thus rotated and raised intermittently in timed relation to the sheet separator so that each sucker 126 forwards a sheet. In the third modification, Fig. 22, at each corner of the pile 150 three "collapsing" forwarding suckers 151 are carried on an endless chain 152 running over sprockets 153, and are connected by flexible air tubes 154 to a rotatable suction control valve 155. The motion of the chain may be intermittent, and the chain may be moved up and down. Instead of chains and sprockets, the suckers could be carried on bands passing over pulleys.