GB2247450A - Apparatus for separating signatures from a stack - Google Patents

Abstract

An apparatus is provided for separating signatures in a stack located at a pick-up station (13), for example in an arrangement for opening and bursting folded signatures. At least one suction head is provided for adhering to one leaf of each signature in the stack for transporting it to a delivery station (91) via rollers (46), (47), the other leaf being burst from the signature as it is fed via rollers (60), (61) to delivery station (92). Vacuum is drawn at the suction head by means of a Venturi device (26) (Fig 4) connected to a source of air pressure and means are provided to interupt the air flow to the Venturi device when the transport mechanism reaches the delivery station (91) to terminate the vacuum at the suction device and thereby allow the leaf to be released. <IMAGE>

Description

INPROVENENIS IN OR RELATING TO SHEET SEPARATING APPATATUS This invention relates to apparatus for separating sheets from a stack of sheets and is particularly although not exclusively applicable to separating the leaves of a folded sheet and, if required severing the leaves from one another.

This invention provides an apparatus for separating sheets froze a stack of sheets comprising; a sheet pick-up station, means to hold a stack of sheets at the pick-up station with a sheet at the top of the stack free to be removed, a sheet delivery station to which sheets removed from the stack are to be delivered; a sheet transport mechanism having means for engaging and holding an edge of a sheet adjacent one face of the stack for transporting the sheet from the stack to the delivery station, the sheet transport mechanism comprising at least one suction head for adhering to an edge portion of a sheet, a venturi device having a connection to a remote source of air pressure, an outlet for air pressure and an inlet at which a vacuum is drawn whereby the action of the air flow through the venturi device connected to the suction pad draws vacuum at the suction head and thereby adheres a sheet to the head and means to interrupt the air flow through the venturi device when the transport mechanism reaches the delivery station to release the sheet to the delivery station.

In one embodiment of the invention the means to interrupt the air flow through the venturi device at the delivery station may comprise a blocking element to engage over the outlet of the venturi device when the venturi device reaches the delivery station to prevent air flow through the outlet and thereby cause air flow through said inlet to discharge the sheet from the suction pad at the delivery station.

The sheet transfer mechanism may comprise at least two spaced suction heads each having a respective venturi device connected to said remote source of air pressure and having outlets from which air is released in creating suction at the inlets of the venturi devices and separate blocking elements being provided at the delivery station to obstruct the respective outlets of the venturi devices at the delivery station to cause the sheet to be discharged from the suction heads at the delivery station.

In any of the above arrangeitents said transfer mechanism may include means for rotating the suction head at the pick-up station between a position in which the suction head lies parallel to the stack adjacent an edge of a sheet in the stack to engage and adhere to the sheet and a position in which the suction head is angled with respect to the stack to raise the edge of the sheet to which the suction head is adhered from the stack prior to linear movement to transfer the sheet edge to the delivery station where the sheet is released.

For example the transfer mechanism may include shaft means on which the or each venturi device and suction head are mounted and means may be provided for both rotating the shaft means at said pick-up station to raise an edge of the sheet from the stack once the suction head has adhered to the sheet and for displacing the shaft means linearly from the pick-up station to the delivery station for release of the sheet at the delivery station.

More specifically the shaft means may be mounted in spaced guideways extending between the pick-up and delivery positions and a drive mechanism is provided for rotating the shaft means as aforesaid and displacing the shaft means between said pick-up and delivery positions.

Further, the mechanism for rotating and displacing the shaft means may comprise a rotary crank mechanism connected to the shaft means for turning the shaft means at the pick-up position and then displacing the shaft along the guideways to the delivery position and thence restoring the shaft means to the pick-up position.

The apparatus is particularly suitable for opening leaves of a folded sheet, in which case first sheet drive means are provided at the delivery station for receiving one free edge of one leaf from the stack, second sheet drive means are provided at a further delivery position located nearer to the stack holding means than the first sheet drive means to receive the free edge of the other leaf and means are provided to guide the other leaf towards the second drive means as the first leaf is moved toward the first drive means, the arrangement being such that said other leaf is engaged with the second drive means and in being displaced thereby, cause the first leaf to move towards the first drive means.

In one arrangement according to the invention a sheet splitter means is provided between the drive means to split the leaves as they are drawn through the respective drive means. For example the splitter may comprise a wedge shaped member disposed between the respective sheet delivery means with its tapered end facing towards the sheet pick-up station to engage and sever the fold of a folded sheet as the leaves of the sheet are moved by the sheet drive means.

The sheet drive means may comprise first and second sets of nip rollers to engage and draw through the respective sheets of the folded leaf to separate the sheets, each set of rollers including a drive roller having drive means for rotating the roller to deliver leaves placed in the nips of the respective set of rollers through the rollers.

The drive rollers for the sheet delivery means may be driven by a coon drive means with the sheet transfer mechanism.

The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a front view of an apparatus for unfolding and splitting the leaves of a folded sheet in accordance with the invention; Figure 2 is a longitudinal sectional view through the apparatus of Figure 1 showing a leaf pick-up device of a sheet splitting device and two pairs of rollers for feeding the separate leaves of the sheet; Figure 3 is a further detailed view of the leaf pick-up device including one of a pair of spaced suction cups; Figure 4 is a diagramatic sectional view of a venturi effect device for creating suction at one of the suction cups; Figure 5 is a view of one side of the apparatus showing a part of the drive mechanism for moving the leaf pick-up device and for driving other related parts of the apparatus;; Figure 6 is a view of the other side of the apparatus showing the corresponding parts of the drive mechanism; Figure 7 is a detailed view of a device for "fluidising" the sheets in the stack; and Figures 8 to 11 illustrate the lifting, separating and feeding of a folded sheet by the apparatus.

The apparatus which will now be described with reference to the drawings is intended for a paper handling operation in which a folded sheet of paper formed with a line of micro-perforations at the fold is split or burst into two separate leaves. The apparatus is particularly suitable for unfolding and separating leaves of self-carboning paper in which the leaves are, in sequence, carbon back, carbon front and back, carbon front, carbon back, carbon front and back and so on and it is necessary to preserve the sequence of sheets in the separate stacks of leaves formed from the separated sheets.

The apparatus as illustrated in the drawings comprises a frame formed by a pair of spaced parallel upright side plates 10 interconnected at spaced locations by rigid rods 11 and a base 8 formed with feet 9. Towards the lower end of the front of the apparatus, mountings 12 are provided to receive and support an open top cassette 13 at a steep upwardly inclined angle from the front of the apparatus for holding a stack of folded sheets to be separated.

The folded sheets in the stack are oriented with the fold of each sheet towards the front of the apparatus and the free-edges of the folded sheet towards the rear. The cassette has an inner base plate 14 supported on a parallel linkage 14a and sprung upwardly by a coil spring 14b designed to maintain the top sheet of the stack of sheets in the tray generally flush with the upper perimeter of the tray as sheets are withdrawn from the tray. A stack of folded sheets to be separated is disposed in the tray with the micro-perforated fold in each sheet at the end of the tray adjacent the front end of the apparatus and the free-edges of each folded sheet disposed at the raised end of the cassette towards the centre of the apparatus.

A mechanism is provided for lifting the upper leaf of each pair of leaves from the tray opening the leaves and then splitting the leaves.

The cassette is angled steeply without side lays to the paper so that: 1. A misfeed falls back and the mechanism can have a second go at it; 2. Single sheets cannot be fed, they simply fall back each time; 3. Sheets in the cassette oriented 'spine up' instead of foredge up suffer the same fate.

All this is important since the cassette normally handles pre-collated sections alternating - CB CFB CF, CB CFB CF etc. (carbon back, carbon front and back, carbon front) and getting out of sequence would cause difficulties.

The sheet lifting mechanism comprises an elongate bar 16 extending along the apparatus and terminating in down turned legs 17 to which outwardly projecting spindles 18 are secured. The spindles run in vertically extending slots 19 (see Figures 5 and 6) formed in the respective side plates 10 of the apparatus to constrain the arms and thereby the bar 16 to move vertically within the slot 19 and to rotate about the horizontal axis defined by the spindles 18. A rotary shaft 21 extends through the spaced plates 10 supported in bearings in the plates. The ends of the shaft 21 project beyond the plates and one projecting end has a toothed wheel 22 secured thereto which is engaged by an electric motor driven chain drive 23 to rotate the shaft 21. The drive motor is mounted within the house towards the rear thereof as indicated in dotted outline in Figure 2.Crank arms 24 are fixed to both ends of the shaft and are linked by connected rods 25 to the ends of the spindles 18 projecting from the slots. The crank mechanisms are designed to reciprocate the bar 16 in a vertical direction within the confines of the slots 19 and at the same time to impart a large rotational movement to the bar about the axis of the spindles 18. At the upper and lower ends of its travel the ratio of the length of the rotating arm 24 to the length of the connecting arm 25 is carefully selected to provide pure relatively slow rotation of the bar at the bottom of the travel of the bar without linear movement followed by a relatively fast linear movement of the bar up the slots 19.

A pair of "venturi" effect suction generating devices 26 are mounted at spaced locations along the bar 16. A T connector 27 is mounted on the bar between the suction devices and is connected to a remote source of air pressure outside the apparatus by flexible tubing 28. The T connector has outlets 29 connected to the respective suction devices 26.

One of the suction devices 26 will now be described in greater detail with reference to Figures 3 and 4 of the drawings.

The suction device has an inlet 30 connected to the T connector 29 and has a gradually widening venturi passage 31 having a series of annular openings 32 and a discharge orifice 33. Air under sufficiently high pressure is driven through the widening passage 31 to exhaust with suction developed at each of the openings 32. Each opening 32 is located within an individual suction chamber 34. The chambers 34, in turn open via resilient flap valves 35 to a common chamber 36. A resilient suction cup 37 is mounted on the suction device 26 by a connector 38 to link the chamber 36 to the cap to draw a vacuum or suction within the cup. The suction cup 37 has a rim 39 to engage the surface of a leaf to be picked up. The connector 38 has a short inlet tube 40 projecting into the cap.The free end of the tube 40 is heavily chamfered on either side as indicated at 41 so that when the cup is compressed on one side onto the stack as the cup is rotated to raise an edge of a leaf from the stack the inlet tube on the side disposed away from the stack remains open to preserve the suction effect in the cap.

As shown in Figure 2 of the drawings the discharge orifice 33 of each "venturi device" is connected by a conduit 30a which extends to the adjacent lug 17 of the bar where it is connected to an upturned nozzle 17a having a flap valve 17b formed by a flexible brass shim overlying the nozzle outlet. When free the flap valve 17b is raised by air pressure in the nozzle to allow air flow from the "venturi" device 26. When obstructed as described later the nozzle is closed and the resulting break down in air flow through the venturi device terminates the suction effect to suction cup 37.

Referring to Figure 2 of the drawings, the bar 16 carrying the suction devices is shown in the leaf pick-up position with the respective suction cups 37 of the two suction devices facing downwardly to engage a free-edge of a leaf of a folded sheet in the stack of sheets supported in the tray 13. To assist the separation of the uppermost leaf from the leaf below it an air jet is delivered at the upper end of the stack from an air jet 42 embodied in an elongate plate 42a extending across the apparatus. The plate is pivotally mounted between the side plates of the apparatus and an arm 43 is provided for adjusting the angle of the plate, one of the side plates 10 having a series of holes 10a to receive an inturned end of the arm to lock the arm in position. The air jet acts to "fluidise" the upper leaves in the stack and thereby assist in their separation from the stack.

The leading edge of the sheet is lifted by the suction caps into the nip 45 of a pair of horizontally spaced contra-rotating rollers 46, 47.

As can be seen in Figures 5 and 6, the rollers are mounted on shafts 48, 49 which in turn, are supported in bearing housings 50, 51 slidably located in horizontally extending slots 52 in the plates 10.

Compressions springs 53 act between the ends of each slot and the adjacent bearing housing 50 for one of the shafts 48 to bias resiliently the rollers 46, 47 carried by the shafts 48 and 49 together to create the nip to receive the edge of the sheet of paper as described earlier.

On one side of the apparatus, as shown in Figure 5, the shafts 48 and 49 are extended and carry tooth pinions 54 and 55 around which the chain drive mechanism 23 on that side of the apparatus extends to rotate the shafts in opposite directions.

In order to release the suction or vacuum drawn in the caps 37 two resilient obdurating members 56 are mounted on brackets 56a on the side walls 10 of the apparatus. The obdurating members 56 are formed from spring steel and the ends of the members are covered by plastic boots. The members are positioned in the paths of the nozzles 17a on bar 16 to engage the flap valves 17b to close the nozzles 17a when the bar 16 has reached the upper limit of its travel. Obstructing the airflow from the outlets 33 increases pressure in the chambers 35 and terminates the vacuum or suction drawn in the suction caps 37 thereby releasing the edge of the sheet from the caps.

A second pair of contra-rotating rollers 60, 61 is mounted in the apparatus spaced horizontally from the upper end of the cassette. The second pair of rollers are mounted on a vertically spaced pair of shafts 62, 63 mounted in bearing housings 64, 65 which are located in vertical slots 66 with a compression spring 67 acting between the upper end of the slot and the adjacent bearing block 64 to hold the rollers 60, 61 resilently together. The ends of the shafts 62, 63 to one side of the apparatus carry pinions 68, 69 engaged by the chain drive 23 to rotate the shafts in opposing directions. On the other side of the apparatus a gear device 80, 81 is taken from the lower shaft 63 to a further shaft 82 to which a sprocket 83 is fixed to receive the chain drive 23 from pinion 22 is described earlier.

A wedge shaped plate 71 is disposed with its edge 71a over the cassette and the faces of the plate leading towards the nips of the respective pairs of drive rollers to guide the leaves to the rollers. An air jet may be incorporated at the opening of the wedge to assist in separating the leaves.

Referring to the step-by-step sequence illustrated in Figures 8 to 11, a leading edge of a leaf in the cassette is turned up by the sheet lifting mechanism and raised towards the upper pair of rollers 46, 47. As the edge of the upper leaf is lifted upwardly into the upper nip 45 between the rollers 46 and 47, the lower leaf is automatically drawn upwardly and rearwardly of the tray to engage in the rollers 60,61. The length of the paper path to the second (lower) rollers is shorter than the vertical path so that as bar 16 reaches the top of its travel and vacuum at the suction pads 37 is released so the lower leaf is engaged in the lower rollers 60, 61. The lower rollers then control movement of the sheet and movement of the lower leaf through the lower roller causes a corresponding movement of the upper leaf into the upper rollers 46, 47.

As the leaves of the sheet are drawn through the respective pairs of rollers the perforated spine between the leaves of the sheet is drawn against the edge 71a of the wedge and is burst to separate the leaves.

Since the upper leaf of the sheet is engaged in the upper rollers only by movement of the lower leaf through the lower rollers a single sheet or a double sheet placed the wrong way round in the tray will not be fed by the apparatus and the sheet would simply be raised by the suction caps towards the upper rollers released to fall back to the tray and they raised again until the machine is stopped and the offending sheet removed.

The upper leaf fed through the rollers 46 and 47 is deflected by a curved plate 90 mounted at the upper end of the apparatus downwardly into a first receiving tray 91 disposed at the front of the apparatus over the tray 14. The lower pair of rollers 60, 61 delivers beneath directly into a receiving tray 92 mounted at the rear of the apparatus. Thus the folded sheets loaded in the tray 14 in the apparatus are separated into individual leaves which are then accumulated in separate stacks, preserving their original sequence.

The invention is not exclusively applicable to apparatus for separating the folded sheets. The "venturi" suction operated devices for engaging and lifting an edge of a sheet into a nip between a pair of rollers can be equally utilised in other applications of the sheet feeding. Similarly the apparatus is not exclusively applicable to paper handling and can be utilised for handling other client sheet materials. Also the apparatus may be constructed to draw sheets from the bottom of a top feed stack rather than from the top of the stack as described above.

The advantages arising out of the use of vacuum generators of the type described above in the apparatus according to the invention are: one compressor does both jobs vacuum and air blast, vacuum can be switched to air blast, by closure of vacuum generator exhaust, in a split second thereby pushing the paper away. Normally vacuuming takes a finite time to die and therefore release a problem for a high speed paper machine; vacuum systems suck in paper dust causing troublesome blockages. Our arrangement clears the suction head once a cycle (every second!); as the suction cups return to their original positions by travelling downwards, paper is moveing upwards close by. Air blas from the suction cups whose exhaust is closes ensures no contact between the highly abrasive paper and the delicate sucker in "Hoovercraft".

The disadvantage with systems having two more suckers driven by vacuum pumps is that failure of one sucker to make contact evacuates the system to ambient air causing the oter sucker to fail also. To avoid this each sucker must be independently driven which is both expensive and complex.

The compressed air systems of the present invention does not suffer from this problem at all and will happily operate or "fly" on one sucker only.

Claims (16)

CLAIMS:

1. An apparatus for separating sheets from a stack of sheets comprising; a sheet pick-up station, means to hold a stack of sheets at the pick-up station with a sheet at the top of the stack free to be removed, a sheet delivery station to which sheets removed from the stack are to be delivered; a sheet transport mechanism having means for engaging and holding an edge of a sheet adjacent one face of the stack for transporting the sheet from the stack to the delivery station, the sheet transport mechanism comprising at least one suction head for adhering to an edge portion of a sheet, a venturi device having a connection to a remote source of air pressure, an outlet for air pressure and an inlet at which a vacuum is drawn whereby the action of the air flow through the venturi device connected to the suction head draws vacuum at the suction head and thereby adheres a sheet to the head and means to interrupt the air flow through the venturi, device when the transport mechanism reaches the delivery station to release the sheet to the delivery station.

2. An apparatus as claimed in Claim 1, wherein the means to interrupt the air flow through the venturi device at the delivery station comprises a blocking element to engage over the outlet of the venturi device when the venturi device reaches the delivery station to prevent air flow through the outlet and thereby cause air flow through said inlet to discharge the sheet from the suction head at the delivery station.

3. An apparatus as claimed in Claim 2, wherein the sheet transfer mechanism comprises at least two spaced suction heads each having a respective venturi device connected to said remote source of air pressure and having outlets from which air is released in creating suction at the inlets of the venturi devices and separate blocking elements being provided at the delivery station to obstruct the respective outlets of the venturi devices at the delivery station to cause the sheet to be discharged from the suction pads at the delivery station.

4. An apparatus as claimed in any of the preceding claims, wherein said transfer mechanism includes means for rotating the suction head at the pick-up station between a position in which the suction head lies parallel to the stack and adjacent an edge of a sheet in the stack to engage and adhere to the sheet and a pcsition in which the suction head is angled with respect to the stack to raise the edge of the sheet to which the head is adhered from the stack prior to moving linearly to transfer the sheet edge to the delivery station.

5. An apparatus as claimed in Claim 4, wherein the transfer mechanism includes shaft means on which the or each venturi device and suction head are mounted and means are provided for both rotating the shaft means at said pick-up station to raise an edge of the sheet from the stack once the suction head has adhered to the sheet and for displacing the shaft means linearly from the pick-up station to the delivery station for release of the sheet at the delivery station.

6. An apparatus as claimed in Claim 5, wherein the shaft means is mounted in spaced guideways extending between the pick-up and delivery positions and a drive mechanism is provided for rotating the shaft means as aforesaid and displacing the shaft means between said pick-up and delivery positions.

7. An apparatus as claimed in Claim 6, wherein the mechanism for rotating and displacing the shaft means comprises a rotary crank mechanism connected to the shaft for turning the shaft means at the pick-up position and then displacing the shaft means along the guideways to the delivery position and thence restoring the shaft means to the pick-up position.

8. An apparatus as claimed in any of the preceding claims for separating leaves of a folded sheet, wherein first sheet drive means are provided at the delivery station for receiving one free edge of one leaf from the stack, second sheet drive means are provided at a further delivery position located nearer to the stack holding means than the first sheet drive means to receive the other free edge of the other leaf and means are provided to guide the other leaf towards the second drive means as the first leaf is moved towards the first drive means, the arrangement being such that said other leaf is engaged with the second drive means and, in being displaced thereby, causes the first leaf to move towards the first drive means.

9. An apparatus as claimed in Claim 8, wherein sheet splitter means are provided between the drive means to split the leaves of the folded sheet as they are drawn through the respective drive means.

10. An apparatus as claimed in Claim 9, wherein the sheet splitter means comprises a wedge shaped member disposed between the respective sheet delivery means with its tapered edge facing towards the sheet pick-up station to engage and sever the fold of a folded sheet as the sheet is drawn over said edge by the respective sheet drive means.

11. An apparatus as claimed in any of Claims 8 to 10, wherein the sheet drive means comprises first and second sets of nip rollers to engage and draw through the respective sheets of the folded leaf to separate the sheets each set of rollers including a drive roller having drive means for rotating the roller to deliver leaves placed in the nips of the respective set of rollers through the rollers.

12. An apparatus as claired in Claim 11 wherein the drive rollers for the sheet drive means are driven by a common drive means with the sheet transfer mechanism.

13. An apparatus as claimed in any of the preceding claims wherein the suction head or heads comprise resiliently flexible walled suction cups and a suction inlet tube is provided in each cap having an angle inlet to enable the cup to be engaged obliquely with a surface whilst maintaining the suction action in the cap.

14. An apparatus for separating sheets from a stack of sheets substantially as described with reference to and as illustrated in the accompanying drawings.

15. An apparatus for separating leaves of a folded sheet in a stack of folded sheets substantially as described with reference to and as illustrated in the accompanying drawings.

16. An apparatus as claimed in any of the preceding claims, wherein an air jet is provided adjacent the stack holding means to direct air at said one face of the stack to "fluidise" the sheets in the stack and thereby facilitate separation of an uppermost sheet from the stack.