High speed sheet feeder singulator

Abstract

High speed sheet feeders receive blocks or bricks of paper sheets, cards or folders stacked edgewise on a downsloping supply ramp, and singulate these for edgewise feeding in rapid succession. The frontmost sheets ready for feeding are buckled and fanned at their upper edges, and their lower edges are arched forward to form a dimple or ridge-shaped pocket by an underlying central traction singulator. A pair of ganged or synchronized feed belts engage the frontmost sheet and propel it rapidly downward edgewise, and a slanting discharge belt receives and diverts the sheet at even higher speed between the discharge belt and a tractive pinch roller. A transfer assembly beneath the discharge belt may receive sheets from an adjacent feeder and interleave them upon command with sheets delivered by the discharge belt.

What is claimed is: 
     
       1. A high speed sheet feeder comprising: a supporting base having a feed end and a delivery end,   an upstanding feed pedestal mounted at the feed end of the base and slanting steeply downward toward a central portion of the base,   a supply ramp mounted on and spaced above the base, slanting downward toward the feed pedestal and defining therewith a feed slot region therebetween,   .[.sheet supply.]. means .Iadd.for supplying sheets .Iaddend.mounted on the supply ramp and positioned to support a large plurality of individual sheets stacked as a brick thereon with their edges facing the supply ramp and with the face of the forwardmost sheet leaning against the pedestal above the feed slot region,   a pair of endless flexible feed belts mounted on power-driven .[.roller means.]. .Iadd.rollers .Iaddend.on the pedestal with substantially straight and parallel portions of their respective outer traction surfaces spaced apart along descending paths facing said forwardmost sheet, defining a feed plane, and traveling in synchronism downward toward the feed slot region,   a downwardly curving central singulator positioned at the feed end of the supply ramp extending across the feed slot region and the feed plane between the pair of feed belts, and presenting a traction face to the side of the forwardmost sheet opposite to said feed belts' traction surfaces,   an endless flexible discharge belt mounted on power-driven roller means, below the feed slot region, having a downwardsloping upward-facing traction run crossing the feed plane below the supply ramp, midway between the descending feed belt paths,   a discharge pinch roller rotatably mounted beneath the supply ramp tractively engaged with and depressing the traction run of the discharge belt to produce tractive engagement thereof with the pinch roller over an arcuate sector of the pinch roller leading to a delivery path extending between the base and the supply ramp toward the delivery end of the base,   and means driving the discharge belt's traction run at a substantially faster linear velocity than the velocity of the synchronized feed belts traveling downward in the feed plane,   whereby each forwardmost sheet of the brick of stacked sheets in turn is tractively engaged by the feed belts with its lower edge arched between the feed belts by the singulator, thereby breaking the fibre-lock friction bond between the forwardmost sheet and its next adjacent sheet, and whereby the forwardmost sheet is propelled downward edgewise by the synchronized feed belts along a feed path substantially coinciding with the feed plane, with the centered discharge belt receiving and guiding its lower edge between the discharge belt and the discharge pinch roller, through the arcuate sector of their tractive engagement, thereby propelling the sheet along the delivery path.   
     
     
       2. The sheet feeder defined in claim 1 wherein the feed pedestal defining the descending paths of the feed belts is positioned in the central portion of the forwardmost sheet of the supply brick, whereby the upper corners of said sheet and the next succeeding sheets are unsupported by the feed belts or the feed pedestal and are free to lean fanningly forward admitting air therebetween. 
     
     
       3. The sheet feeder defined in claim 1, wherein the singulator is adjustable to change the distance by which the singulator extends beyond the feed plane and intrudes between the feed belts. 
     
     
       4. The sheet feeder defined in claim 1 wherein the singulator is formed by the feed slot portion of an endless elastomer singulator belt supported by a plurality of rollers on the supply ramp with its outer traction face presented in the feed slot protruding through the feed plane, and including indexing drive means advancing the singulator belt in periodic increments upon command. 
     
     
       5. The sheet feeder defined in claim 1 wherein the discharge belt comprises a ribbed endless elastomer timing belt. 
     
     
       6. The sheet feeder defined in claim 1 wherein the discharge pinch roller is adjustably mounted to advance and retract the pinch roller between an extended position of maximum deflection of the traction run of the discharge belt and maximum angular arcuate engagement sector, and a retracted position of minimum deflection and minimum angular engagement sector. 
     
     
       7. The sheet feeder defined by claim 1 including a plurality of sheet sensor means each responsive to the presence of a sheet at a predetermined point in the device, the output signals from all said sensor means being connected to control circuitry governing the drive components producing movement of the traction runs of the feed belts and the discharge belt. 
     
     
       8. The sheet feeder defined by claim 1, further including a brake plunger positioned to urge the forwardmost sheets arriving at the feed plane away from the feed belts to provide instant interruption of feeder operation. 
     
     
       9. The sheet feeder defined in claim 1, further including a back plate pivotally mounted on the feed pedestal and presenting a guide surface facing the feed plane provided with guide grooves aligned to receive the substantially parallel portions of the feed belts in sliding engagement therein. 
     
     
       10. The sheet feeder defined in claim 9 wherein the back plate is pivotally adjustable to change the distance by which the singulator extends beyond the feed plane and intrudes between the feed belts. 
     
     
       11. The sheet feeder defined in claim 1, further including buckling means mounted on the feed pedestal positioned to depress the upper edges of the forwardmost sheets advanced by the .[.supply.]. means .Iadd.for supplying sheets .Iaddend.in a buckled, arched configuration, admitting air between the upper facing regions of adjacent sheets arriving at the feed plane. 
     
     
       12. The sheet feeder defined in claim 11 wherein the buckling means comprises a plurality of rollers positioned with their rims depressingly engaging the upper edges of the arriving adjacent sheets. 
     
     
       13. The sheet feeder defined in claim 1, further including a transfer assembly positioned between the discharged belt and the base, comprising a pair of transfer pinch rollers, a transfer ramp leading to a convergence line of tangent contact between the pinch rollers and defining therewith a transfer path extending from the feed end of the base through said line of tangent contact to the delivery end of the base, and also including clutch drive means connected to deliver driving force from the discharge belt to turn the transfer pinch rollers upon command. 
     
     
       14. A first sheet feeder defined in claim 13, aligned with at least one second sheet feeder positioned to deliver sheets along a delivery path to the transfer ramp near the feed end of the first sheet feeder, said delivery path of the second sheet feeder coinciding with the transfer path of the first sheet feeder, whereby a sheet from the second sheet feeder may be delivered via the transfer path for addition at a preselected position to the sheets successfully delivered along the delivery path of the first sheet feeder. 
     
     
       15. The sheet feeder defined in claim 1 wherein the .[.sheet supply.]. means .Iadd.for supplying sheets .Iaddend.comprises endless ribbed elastomer timing belt means with a traction run arrayed down the length of the supply ramp, operatively connected to belt drive means positioned to move said traction run and the brick of sheets supported thereon toward the feed pedestal upon command. 
     
     
       16. The sheet feeder defined in claim 15 wherein the .[.sheet supply.]. means .Iadd.for supplying sheets .Iaddend.comprises two substantially parallel endless ribbed elastomer timing belts spaced apart on the supply ramp. 
     
     
       17. The sheet feeder defined in claim 15, further including a supply sensor mounted on the feed pedestal disabled by the presence of a plurality of forwardmost sheets on the supply ramp and actuated by the absence of said sheets to initiate advancing movement of the traction run and the brick of sheets supported thereon toward the feed pedestal. .Iadd. 
     
     
       18.  A high speed sheet feeder comprising: a supporting base;   a supply ramp and a feed pedestal each having a respective end, each end converging and being positioned above the base, each of the supply ramp and the feed pedestal sloping downwardly toward a point of convergence proximate the base, the supply ramp and feed pedestal defining, at the point of convergence, a feed slot for allowing sheets to pass between the feed pedestal and the supply ramp in a lengthwise direction extending downwardly toward the base;   a sheet supply conveyor for moving a stack of sheets on the supply ramp, each of the sheets in the stack having a face, the forwardmost of the sheets in the stack having a face in engagement with the feed pedestal and a lowermost edge of the forwardmost sheet being proximate the feed slot;   a pair of movable feed conveyors mounted on the feed pedestal, the feed conveyors being spaced-apart from each other in a widthwise direction transverse to the lengthwise direction, the feed conveyors having traction faces constructed and arranged to define a feeding plane adjacent the stack and the feed conveyors being constructed and arranged so that the traction faces engage a forwardmost face of a forwardmost sheet in the stack to drive the forwardmost sheet in a downward direction through the feed slot at a first velocity;   a singulator positioned at the end of the supply ramp proximate the point of convergence, the singulator extending into the feed slot at a location with respect to the widthwise direction aligned between each of the spaced-apart feed conveyors, the singulator extending through the feeding plane of the feed conveyors toward the feed pedestal so as to cause a lowermost edge of a sheet driven thereover by the feed conveyors to arch about a midsection of the sheet away from an adjacent sheet in the stack to break a fibre-lock frictional contact with the adjacent sheet; and   a sheet discharge conveyor positioned below the feed slot to receive sheets driven by the feed conveyors through the feed slot, the discharge conveyor being oriented to drive sheets to a discharge point remote from the feed slot and the discharge conveyor driving sheets at a second velocity that is faster than the first velocity. .Iaddend. .Iadd.   
     
     
       19.  The sheet feeder as set forth in claim 18 wherein the sheet discharge conveyor comprises a discharge belt and a pinch roller positioned against the discharge belt and the pinch roller deflecting a surface of the discharge belt to form a nip for receiving sheets. .Iaddend. .Iadd.20. The sheet feeder as set forth in claim 18 wherein the feed pedestal is sloped downwardly toward the base at a steeper angle than an angle of slope of the supply ramp toward the base. .Iaddend. .Iadd.21. The sheet feeder as set forth in claim 20 wherein the feed pedestal and the supply ramp define planar surfaces for contact with the stack and wherein the planar surfaces form an approximately right angle at the point of convergence. .Iaddend. 
     
     
        .Iadd.22.  The sheet feeder as set forth in claim 18 wherein the singulator is adjustable to change a distance of extension thereof toward the feed pedestal so that the size of the arch caused thereby in the sheets is variable. .Iaddend. .Iadd.23. The sheet feeder as set forth in claim 18 wherein the singulator comprises an elastomeric singulator belt having a traction face positioned along a direction of sheet travel through the feed slot. .Iaddend. .Iadd.24. The sheet feeder as set forth in claim 23 wherein the singulator belt includes an indexing drive to advance the singulator belt in periodic increments. .Iaddend. .Iadd.25. The sheet feeder as set forth in claim 18 wherein the discharge conveyor comprises a ribbed endless elastomeric timing belt. .Iaddend. .Iadd.26. The sheet feeder as set forth in claim 19 wherein the pinch roller is adjustably mounted to move the pinch roller between a maximum deflection of the discharge belt and a minimum deflection of the discharge belt wherein a respective maximum and minimum engagement of an arc of the pinch 
     
     
        roller with the discharge belt is obtained. .Iaddend. .Iadd.27.  The sheet feeder as set forth in claim 18 further comprising a controller for controlling movement of the sheet supply conveyor, the feed conveyors and the discharge conveyor. .Iaddend. .Iadd.28. The sheet feeder as set forth in claim 27 further comprising a plurality of sheet sensors, each responsive to the presence of a sheet at a predetermined point in the sheet feeder for signalling the controller. .Iaddend. .Iadd.29. The sheet feeder as set forth in claim 18 further comprising a brake plunger positioned to bias the forwardmost sheet in the stack away from the feed conveyors to interrupt feeder operation. .Iaddend. .Iadd.30. The sheet feeder as set forth in claim 18 wherein the feed conveyors comprise endless feed belts and the feed pedestal includes a back plate having lengthwise directed grooves thereon for guiding the feed belts. .Iaddend. .Iadd.31. The sheet feeder as set forth in claim 30 wherein the back plate is pivotally adjustable to change the positioning of the feed belts relative to the singulator. .Iaddend. .Iadd.32. The sheet feeder as set forth in claim 18 further comprising a buckling means mounted on the feed pedestal to depress upper edges of the forwardmost sheet and adjacent sheets thereto in the stack into a buckled arched configuration, thereby admitting air between upper ends of the forwardmost and the adjacent sheets thereto. .Iaddend. .Iadd.33. The sheet feeder as set forth in claim 32 wherein the buckling means comprises a plurality of rollers positioned to engage the upper edges of the forwardmost sheet and the adjacent sheets thereto. .Iaddend. .Iadd.34. The sheet feeder as set forth in claim 19 further comprising a transfer assembly positioned between the discharge belt and the base, comprising a pair of transfer pinch rollers, a transfer ramp having a face that extends into a tangent line between each of the pinch rollers and a clutch for delivering a driving force from the discharge belt to the transfer pinch rollers at predetermined times. .Iaddend. .Iadd.35. A sheet feeder as set forth in claim 34 including a means for interconnecting the sheet feeder to a second sheet feeder positioned to deliver sheets along a delivery path to the transfer ramp of the first sheet feeder, the delivery path of the second sheet feeder coinciding with a transfer path of the sheet feeder, whereby a sheet from the second sheet feeder is delivered to the transfer path of the sheet feeder for addition at a preselected time to the sheet feeder. .Iaddend. 
     
     
        .Iadd.36.  The sheet feeder as set forth in claim 18 wherein the sheet supply conveyor comprises endless ribbed elastomeric timing belts positioned along the length of the supply ramp, the belts including a drive to move the belts along the ramp toward the feed pedestal. .Iaddend. .Iadd.37. The sheet feeder as set forth in claim 36 further comprising a supply sensor positioned on the feed pedestal, the sensor signalling an absence of sheets to control driving of the conveyor to advance additional sheets of the stack toward the feed pedestal. .Iaddend.