Patent GB-699704-A (GB)
Title: Improvements in a sheet feeding mechanism
Inventor: BRUNS HERBERT FREDERICK
IPC: B65H3/08
Filed: 1951-04-25
Abstract: 699,704. Feeding sheets. DITTO, Inc. April 25, 1951. No. 9656/51. Class 100(i) In a sheet-feeding apparatus comprising a sheet lifter which lifts a sheet by suction from a stack of sheets and releases it in operative relation to a suction conveyer which moves the sheet laterally of the stack, suction is established in the lifter to adhere a sheet to a movable part of the lifter and to elevate the movable part relatively to the main body of the lifter to a predetermined position, and in this position suction is established in the conveyer and that in the lifter is modified, whereby the movable part is maintained in the elevated position and the sheet is freed from adherence to the movable part. The invention is described as applied to a rotary offset lithographic machine of the type comprising a main cylinder 1, Fig. 1, to which the sheets are conveyed, an offset roller 2, a receiving tray 5, and moistening and inking devices 6, 7. The sheets are placed on a feed table 3, are lifted therefrom by suction separators which lift a sheet into contact with an endless suction belt conveyer 4 which feeds the sheet laterally of the table into the grippers of the cylinder 1. Sheet-forwarders:-A sheet lifted from the table 3 by two suction lifters (Fig. 9) is fed to the grippers of the cylinder 1 by a sheet-forwarder 4 comprising an endless belt 32, Figs. 1, 4 and 7, trained about a main pulley 22, secured to an intermittently-driven shaft 10, and a pair of rolls 24, 26, Fig. 7. The pulley 22 fits between side plates 8, 9 which are recessed to engage a supporting rod 16 having eccentric adjustment in the machine side frames 13, 14. The belt 32 has holes 36 therein, and a suction box 33 is arranged behind the lower run of the belt whereby sheets are fed by the belt. Suction to the box 33 is established through a pipe 37, a passage in the side plate 8, apertures 40 in the pulley 22, and a pipe which leads from a coupling 44, Fig. 9, in each sheet-lifter. In a modification, a suction box and perforated belt are provided as above, but the construction of the ports and passages through the pulley and side plates is modified. The means for imparting intermittent rotation to the shaft 10 comprises a toothed driving belt passing around a toothed pulley 251, Figs. 4 and 33, which is freely mounted on a stub shaft 11 carried in the bearing sleeve of a plate 253 secured adjustably in an enlarged opening in the machine side plate 14. A gear sector 263 pivoted on a pin 262 to the inner face of the pulley 251, is provided with a roller 266 which engages a cam 267 secured to the inner face of the fixed plate 253. The sector gear 263 meshes with another sector gear 269 secured to the stub shaft 11, so that, as the pulley rotates, due to the action of the' cam 267, the gear 269 and shaft 11 are rotated intermittently. To facilitate the removal of the sheet-lifting and conveyer device 4 as a whole from the machine, the shaft 10 is connected by detachable couplings to the driving stub shaft 11, and to a stub shaft 12 at the opposite end. Sheet-separators:-There are two sheet-lifters, Fig. 9, comprising an upper cylinder 48, secured to one of the side plates 8, 9 of the sheet-forwarder 4, a lower cylinder 50 adjustably-secured within the upper cylinder, and a hollow piston 54 slidable in the lower cylinder and provided with a plain or flared suction foot 55. The piston is closed at its inner end by a cap 58, but the bore 57 communicates with the cylinder through openings 63. Two rubber pads are fitted into peripheral recesses in the piston, one pad 61 limiting the downward movement of the piston and adapted, in certain circumstances as described below, to open a valve 69, and the other pad 62 forming a seal with a face 80 when the piston is raised. In operation, with the piston resting on the top sheet of the pile, suction is applied through a pipe 85 to the upper cylinder, and the piston 54 rises, carrying the sheet from the table 3, until the pad 62 strikes the face 80: in this position suction to the bore of the piston is cut off and the sheet is released, but the piston is still held by the suction above the end of the piston. A rubber pad 59 on the cap 58 lifts a valve 90, whereby the pipe 85 communicates with the pipe 44, and suction is applied to the suction box 33 of the sheet-conveyer 4. When the sheet has been fed by the conveyer, a cam 120, as described below, opens a valve in the suction system to destroy the suction, and the sheet is released by the conveyer and the piston 54 is allowed to fall on to the pile of sheets. The return of the piston is assisted by the action of a compression spring 95 on the valve 90. The timing of the application and release of suction to a sheet in both the lifters and conveyer is not rigidly linked with any other operations of the machine. Separation of sheets from the pile is facilitated by air blasts and spring fingers bearing on the front edge of the pile. A transverse vertical plate 147, Fig. 36, secured at its ends to the machine frame, is slotted at 149, and a block 150 is adjustably secured thereto by screws 173 which pass through vertical slots therein and through the slots 149. The block 150 has an air pipe 143 at its lower edge, communicating with three vertical bores 151, 152, 153, and has several pairs of arms 155-160 to which face plates 161, 162, 163 are secured. Curved air baffles 164, 165, 166 are secured to the arms 155-160. End guide blocks 176, 177 are adjustably secured to the plate 147, and guide fingers 180, on a transverse shaft 181, co-operate with the end blocks to prevent the corners of a separated sheet from curling upwardly and to guide them below the shaft 181. Compressed air delivered to the pipe 143 is projected upwardly and is directed by the baffles 164-166 towards the leading edges of the uppermost sheets in the pile. In the spaces between the pairs of vertical arms are two pairs of leaf springs 167, 168 which are curved at their free ends to engage over the front end of the pile to exert a combing action thereon. Pile supports:-The feed-table 3 comprises an inclined base 3<SP>1</SP>, Figs. 13 and 41, supported by bellows 77 to which compressed air is supplied through a pipe 76 which communicates with a supply pipe 75 when a valve 69, Fig. 9, is open. If the pile is high enough, the piston 54 of the sheetlifter does not descend low enough for the rubber cap 61 thereon to open the valve 69, but when the pile is low, the valve is opened, and compressed air is admitted to the bellows 77 to raise the pile. Air is exhausted from the bellows, to lower the table support 3<SP>1</SP>, by a pipe 228 and a valve 229 under the control of a manually-operable handle. The lower end of the bellows is supported on tierods, and the upper end comprises a wedge-shaped block 186 secured to the base 3<SP>1</SP> of the table 3. The base 3<SP>1</SP> has side plates 187 provided with guide rollers 190, Fig. 41, engaging vertical slots 191 in the machine frames, and a tranverse shaft 193 mounted in the plates 187 has pinions in mesh with fixed racks adjacent the guide slots 191, whereby the support 3<SP>1</SP> is guided for vertical movement. Two adjustable side guides 199 on the support 3<SP>1</SP> each carry a rotatable shaft 208 on which is adjustably secured a tail guide 210, comprising a head portion and a depending wedge-shaped wing portion 215. Pneumatic system:-A motor-driven combined air compressor and vacuum pump 101, Fig. 1, has a suction pipe 102 leading to a Y-connection 103, from which one branch 112 goes to an atmospheric relief valve 104, Fig. 22, and the other branch 105 leads to a pipe 106, Fig. 4, arranged in the form of an endless loop trained about pulleys 107, 108 carried by the machine side frames. Branches from the looped pipe lead to the connections 85, 86 in the suction-lifter devices for the sheets and the sheet-conveyer 4, whereby lateral adjustment of the conveyer and lifters as a whole along the drive shaft 10 is facilitated. The relief pipe 112 is clamped to the outside of the machine frame, and the open end comprises a valve seat 114 adapted to be closed by a plate 115, pivoted at 117, and provided with a roller 119 co-operating with a cam 120 secured to a stub shaft 12 connected to the main shaft 10. Normally, the cam rocks the plate 115 to open the pipe 112 to atmosphere, but the plate can be latched in open position by a spring- urged bell-crank lever 123 when the latter is released by a piston 127 due to the failure of compressed air supplied to the latter. Thus when the supply of compressed air fails or is cut off manually, the pipe 112 is open continuously to atmosphere, and sheet separation is prevented. Compressed air is supplied from the pump 101 through a pipe 133 to a control panel 136 (not shown) and then to the pipe 143 at the end of the sheet pile as described above. A branch line extends about the pulleys 107, 108, and is connected to the pipe 75, Figs. 9 and 13, for supply to the bellows 77.