GB2176465A - Device for drawing off sheets from a sheet stack - Google Patents

Abstract

Sheets are separated from a stack by two parallel take-off rolls (17, 19) one above the other, the sheet stack (11) being urged resiliently upwardly against the lower take-off roll (19). The lower take-off roll (19) is freely rotatably mounted on a pivotable control rail (23) and urged by spring (27) against the driven, upper take-off roll (17). As long as no sheet (13) is introduced between the take-off rolls (17, 19), the lower take-off roll (19) separates sheets from the stack (11) and transfers them to between the take-off rolls (17, 19), but when the uppermost sheet (13) is introduced between the take off rolls (17, 19) the control means moves the lower take-off roll (19) away from the upper take-off roll (17). The take-off device is capable of withdrawing from the sheet stack even sheets sticking to one another or stapled to one another. The control means may comprise dogs (47) on rail (23) engaging in circumferential grooves in the upper take-off roll (17). <IMAGE>

Description

SPECIFICATION Device for drawing off sheets from a sheet stack The invention relates to a device for drawing off sheets from a sheet stack, having a carrier floorfor supporting the sheet stack, a take-off roll mechanism which comprises at least one take-off roll arranged above the carrierfloor and driven by a motor about an axis of rotation parallel to the carrier floor and a feed device for the sheet stack which resiliently moves the carrierfloorandthetake-offroll mechanism towards one another.

In known sheet intake devices of this kind the motor-driven take-off roll engages in frictional engagementwith the uppermost sheetofthe sheet stack and displaces the sheet along the sheet stack.

The friction force displacing the uppermost sheet is determined by the pressure application force with which the take-off roll and the sheet stack are pressed against one another. The sheet stack here forms the counter-pressure face for the uppermost sheet in each case to be withdrawn. Since the take-offforces achievable with such a take-off device are relatively small, faults can occur in the singling of sheetstacks with sheets adhering for example electrostatically to one another. The known take-off device more especially cannot be used as sheet-intake apparatus for willowing machines in which the sheets are to be fed singly from sheet stacks connected by metal clips, or the sheets of the sheet stack are crinkled ortorn.

Itisthe problem ofthe invention to showacon- structively simple way in which the take-offforce of a device for drawing sheets off from a sheet stack can be increased. More especially the object is to be achieved that even sheets adhering to one another can be withdrawn singly from the sheet stack.

On the basis of the device as already explained this problem is solved in accordance with the invention in that between the motor-driven first take-off roll ofthe take-off roll mechanism and the carrierfloorthere is arranged a freely rotatable second take-off roll guided parallel with the axis ofthe first take-off roll and transversely ofthe axis of rotation, which second take-off roll in a first position is driven by the first take-off roll for the take-off of sheets of the sheet stack in frictional engagement and in a second position is lifted away from the first take-off roll, in that seen in the sheet withdrawal direction of the second take-off roll, at a distance therefrom an abutment is provided at least for the uppermost sheet in each case of the sheet stack, in that to the firsttake-off roll there is allocated a counter-pressure device forthe transport of sheets introduced between the two take-off rolls and in that to the second take-off roll there is allocated a control device responding to sheets introduced between the two take-off rolls, which moves the second take-off roll into the first position in the absence of sheets and into the second position when sheets are present.

In this device the uppermost sheet of the sheet stack is moved by the second take-off roll over a comparatively short distance contrarily of the take-off direction ofthefirsttake-off roll and is curved upwards afterthe uppermost sheet abuts on the abutmentwith its edge remote from the take-off roll. The uppermost sheet is partially lifted and introduced between the two take-off rolls. Thefirsttake-off roll grasps the uppermost sheet between itself and the counter-pressure device separately allocated to it, whereby substantially higher friction and take-off forces can be achieved.The second take-off roll is driven intermittently in frictional engagement by the firsttake-offroll,while a control device lifts the second take-off roll from the first and thus halts it when the uppermostsheet has entered the take-off path between the first take-off roll and preferably the counter-pressure device. In this way the object is achieved that the sheets are drawn off individually one afterthe other.

When sheets are to be introduced between the two take-off rolls it must be ensured that the second takeoff roll is lifted for halting away from the first take-off roll by more than the sheet thickness. This can take place in various manners. Thus the control device controlling the intermittent operation of the second take-off roll can be an electrical device which by means of an electric sensor, for example a sensor switch or a light barrier, detects the entry of a sheet into the take-off path and lifts the second take-off roll from the firstfor example electromagnetically.A comparatively simple, purely mechanical construction for the intermittent controlling of the second take-off roll consists in that the second take-off roll is freely rotatably mounted on a control rail which is pivotable axially parallel with the axis of rotation of the firsttake-off roll and initially stressed resiliently towards the firsttake-off roll, in that the first take-off roll comprises circumferential grooves and in that the control rail comprises control dogs which, at least in the first position ofthesecondtake-offroll, engage in the circumferential grooves.The sheet entering the take-off path forces the control dogs at least partially, but by more than the sheet thickness, out of the cir cu mferential grooves, whereby the second take-off roll is lifted away from thefirsttake-off roll by more than the sheet thickness and is halted.

The mechanical control arrangement as explained above can lead to a stressing of the sheets to be withdrawn which is undesired for many areas of use.

Protective drawing off of the sheets from the sheet stack with adequate lifting away ofthe second takeoff roll can be achieved if the second take-off roll is freely rotatably mounted on a control rail which is pivotable axially parallel with the rotation axis of the first take-off roll and initially stressed resiliently towards the first take-off roll and the control rail carries control faces cooperating with thefirsttake-off roll for the control movement of the second take-off roll, the distance ofwhich faces from the pivot axis ofthe control rail is less than the distance of the axis of rotation of the second take-off roll from the pivot axis.

The control rail here forms a lever linkage by which the second take-off roll is lifted by means of the controy faces by more than the sheet thickness. The con- trol faces can atthesametimeformthecounter- pressure faces ofthe firsttake-off roll and are preferably formed as counter-pressure rolls mounted freely rotatably on the control rail.

In a preferred form of embodiment the control rail consists of a plurality of mutually relatively movable segments arranged side-by-side in the axial diretion and carrying the control faces or control dogs. The second take-off roll here consists of a plurality of take-off rolls mounted axially parallel on the seg- ments,the movement ofwhich is controlled by the control faces of the segments on which they are mounted. This measure improves the operational reliability ofthetake-off device. More especially even creased orfolded sheets ortorn or marginally damaged sheets can be drawn off satisfactorily.The sheet to be lifted from the second take-off roll is transmitted out beneath the second take-off roll even ifforexam ple by reason of the crease ortear parts of this sheet are already grasped bythefirsttake-off roll.

The control rail expedientlyatthesametimeforms counter-pressure faces which are initially stressed resiliently towards the first presser roll. The counterpressure faces can be circumferential faces of additional rolls or cylinders mounted axially parallel and freely rotatably on the control rail. To simplifythe construction however it is preferredly provided that the counter-pressure faces are formed by prolongations ofthe control dogs engaging in the circumferential grooves of the first take-off roll, so that a direct abutting contact between the counter-pressure faces and the first presser roll is avoided.Since admittedly in this version the sheetto be withdrawn is conducted in serpentine form through the circumferential grooves, this version is to be used primarily in applications, as for example willowing machineapplica- tions, where protective treatment of the sheets is not important.

The take-off roll mechanism and the carrierfloor are initially stressed resiliently towards one another and guided movably in relation to one anotherforthe feed ofthe sheet stack. In a preferred form of embody mentthe take-off roll mechanism is held fastwith the machine while the carrier floor is guided substantially vertically displaceably in a frame and initially stressed by means of at least one spring upwards towards the second take-off roll. This configuration permits the arrangement ofthe abutment and of a stop limiting the upward curvature of the sheets fastwith the frame above the carrier floor between thefirsttake- off roll and the abutment. By means of such a stop it is possible to ensure in a constructionally simple mannerthatthe uppermost sheet in each case, by reason of its stress caused by the upward curvature reliably spreads out to between the two take-off rolls as soon as its pushed out beneath the second take-off roll.

The stop can be pivotablyfitted on the frame in order to facilitate the charging of the carrierfloorfrom above.

The sheet intake device according to the invention as a rule detaches sheets sticking to one another already bythefactthatthe second take-off roll upwardly curves the uppermost sheet and thus lifts it from the sheet stack before the firsttake-off roll grasps and withdraws the uppermost sheet. Especially in willowing machine applications, staples orthe like which clip the sheets stacked together at the end remote from the take-off rolls can prevent the withdrawal ofthe uppermost sheet. In orderthatthe up permostsheetmay be torn out of the staple, preferably at least one tearing tooth penetrating into the sheet stack is provided on the frame in the region of the abutment.Thetearing tooth penetrates the uppermost sheet and engages with its sharp point in the sheet lying therebeneath. In the withdrawal ofthe uppermost sheetthe tearing tooth tears into the uppermost sheet, while it holds the sheet lying therebeneath, including the staple, fast.

In orderthattheframe may be charged in a simple mannerwith the sheet stack, it is expedientlyformed as a container displaceable in relation to the take-off roll mechanism,fromwhich stop projectionsprot- rude towards one another above the carrier floor in the region ofthetake-off roll mechanism and the side opposite to the take-off roll mechanism. In this way the sheet stack can be laid from above on the carrier floor and pressed downwards pastthestop projections againstthe springs ofthe carrierfloor.

The carrierfloor can perse have a flat upper side.

Howevertheupperside is preferablyofconvexform corresponding to the upward curvature effected by the take-off roll mechanism, that is to say it rises from the regionsofthesecondtake-offroll and ofthe abutmenttowardsthe middle.

The construction expense ofthe sheettake-offde- vice can be considerably reduced if an independent drive motor is omitted and the take-off roll mechanism is driven by means ofthe motor of a processing appliance, for examplethe willowing machine, which receives the sheets. The device for this purpose is expediently secured as a unit detachably on the processing appliance and the take-off roll mechanism is coupled through a push-in coupling with the drive motorofthe processing appliance.

An example ofembodiment of the invention is to be explained in greater detail hereinafter by reference to drawings, wherein:- Figure 1 shows a diagrammatic, partially sectional lateral view of a sheet intake appliance,withdrawing sheets from a sheet stack, in combination with a paperwillowing machine, and Figure2 shows a detail view of a take-off roll mechanism ofthe sheet intake appliance, seen along a line Il-Il in Figure 1.

Figure 1 shows a paperwillowing machine 1 having two cutter cylinders 3,5 rotating oppositely with parallel axes, which shred paper sheets introduced between them on a feed path 7, entered in dot-and-dash lines, and feed them to a waste container (notshown further). The willowing machine 1 as such is notthe object ofthe invention and is notto be explained in greater detail, since it is a matter of a known construction. A sheet intake appliance 9 is detachably fitted on the upper side of the willowing machine 1, which appliance successively draws the uppermost sheet 13 in each case from a sheet stack 11 and feeds it along the feed path 7 to the willowing machine 1. The sheet intake appliance 9 comprises a take-off roll mechanism 15, stationary in relationtothewillowing machine 1, in the region of one ofthe edges ofthe sheet stack 11. The take-off roll mechanism 15 comprises two take-off rolls 17, 19 arranged with parallel axes one above the other.The uppertake-off roll 17 is driven buy a motor 20 (Figure 2) in the direction of an arrow 21 in such mannerthatthe sheet 13 entering between the two take-off rolls 17,19 is fed along the conveying path 7 to the willowing machine 1.The lower take-off roll 19 is mounted freely rotatably on a control rail 23 which in turn is pivotable on the side of thetake-off rolls 17,19 lying forward in thetransport direction of the sheet 13, at a distance from these rolls, about a pivot axis 25 parallel to the axes of rotation of the take-off rolls 17, 19. The take-off roll 19 is initially stressed by a spring indicated at 27 against the presser roll 17, in such a manner that it is drivable in frictional engagement by the uppertake-off roll 17 oppositely thereto in the direction of the arrow 29.

The sheet stack 11 lies on a carrier floor 31 which is vertically displaceably guided in a container 33 and is stressed by compression springs 35 together with the sheet stack 11 upwards againstthe lower take-off roll 19. On the upper edge of the container 33 there are provided inwardly extending stop projections 37,39 which limitthe stroke movement of the sheet stack 11. The stop projections 37 on the side opposite to the take-off roll mechanism 15 furtherform an abutment which prevents the displacement of the uppermost sheet 13 in its sheet plane by the take-off roll 19 acting in frictional engagement on the uppermost sheet 13.

The sheet stretched in between the stop projection 37 and the take-off roll 19 is curved upwards, as illustrated at 13', until it is pushed outwards beneath the take-off roll 19.

The sheet is introduced by the take-off roll 19 between thetake-off rolls 17,19 and a curved stop 41 prevents the sheet from wandering out beyond this position.

The uppermost sheet 13, introduced between the take-off rolls 17, 19 is drawn offfrom the sheet stack 11, being clamped in between the control rail 23 and theuppertake-offroll 17. During the drawing off movementthe lower take-off roll 19 is lifted away from the take-off roll 17 and halted by the sheet 13 stretched in between the upper take-off roll 17 and the control rail 23. The take-off roll 19 is thus intermittent lydriven in orderto prevent more than one sheet ata time being introduced between the take-off rolls 17, 19.

Figure 2 shows details ofthetake-off rolls 17,19 and ofthe control rail 23. The take-off roll 17comprises esa pluralityofcoaxiallyarrangedtake-offcylinders 43 connected fast in rotation with one another through a shaft 42 and forming circumferential grooves 45 between them. The control rail 23 comprises a plurality of segments 46 each with several control dogs 47 which engage in the circumferential grooves 45 when the take-off roll 19 is in frictional contact with the take-off cylinders 43. The take-off roll 19 consists of a plurality of take-off cylinders 49 arranged with parallel axes with spacing from one another between the control dogs 47. The take-off cylinders 49 are freely rotatably mounted by groups by means of axie pins 50own the segments 46.The segments 46 in turn are mounted pivotably in relation to oneanotheron the common spindle 25 in frame 52 of the take-off roll mechanism 15. As long as there is no sheet betwee the circumferential grooves 45 and the control dogs 47, the take-off cylinders 49 are driven by the take-off cylinders 43. When a sheet is introduced, it lifts the control dogs 47, possibly with serpentine deformation, at least partially out of the circumferential grooves 45 whereby the take-off cylinders 49 are lifted by more than the thickness of the sheet from the take-off cylinders 43.The control dogs 47 extend with spacing from the circumferential grooves 45 so thatwhen the take-off roll mechanism 15 is idling no sliding friction forces occur between the take-off roll 17 and the control rail 23. in thewith- drawal of the sheet 13 the control dogs and possibly further zones of the control rail 23 generate the counter-pressureforces of thetake-off roll 17.

Provided the distance of the control faces ofthe control dogs 47 from the pivot axis 25 is less than the axial distance of the spindle 50 from the pivot axis 25, the control rail 23 acts as a step-up levertransmission, so thatthe take-off roll 19 itself lifts away from the take-off roll 17 by more than the sheet thickness if the control faces do not protrude beyondthe circumference of the take-off roll 17 towards the shaft 42. The control faces of the control dogs can also be formed by counter-pressure cylinders or the like rotatably held on the control rail 23.

The wire arch 41 is held on a lid 51 pivotablyfitted on a side of the container 33 remote from the take-off rolls. The lid 51 furthermore carries at least one, preferably several, tearing teeth 53 the points of which point towards the carrier floor 31 and penetrate at least the two uppermost sheets of the sheet stack 11 by reason ofthe pressure of the springs 35. The tearing teeth 53 hold the second-uppermost sheet fast while the take-off roll mechanism 15 draws the uppermost sheet away. In this way the uppermost sheet can be withdrawn from the sheet stack 11 even when its sheets, as indicated at 55, are attached to one another by a metal staple. The uppermost sheet is torn out of the metal staple 45, being slotted bythetearingteeth 53.

In orderthatthe container 33 may be loaded it is horizontally displaceable on a sliding guide 57. After the lid 51 is hinged open the sheet stack 11 can be laid from above on to the carrier floor 31 and pressed past the stop projections 37,39 into the container 33. In order to reduce the danger of injury on the tearing teeth 53, these are hingeably held on the lid 51, preferably so that they disappear into a socket or the like when the lid 51 is hinged up.

In order to facilitate the curvature of the sheets to be withdrawn, the upper side ofthe carrierfloor 31 is of convex curvature, that is to say it rises from the side of thetake-offroll mechanism 15 and from the stop projection 37forming the abutmentforthe upward curvature movement towards the middle.

The control rail 23 is divided into a plurality of segments, each of which carries one of the control dogs 47, and which are each independently pivotably mounted on the spindle 25. This measure reduces the production expense and permits a better mutual abutment of the friction cylinders 43 and 49. The friction cylinders 43,49 can have rubber-elastic outer surfaces to improvethefriction.

In orderto reducetheconstruction expenseofthe take-off devicethetake-off roll mechanism 15 is drivenbythemotor20ofthewillowing machine 1.

The frame 52 ofthetake-off roll mechanism 15ex- tendswith an arm 61 (through an opening (notillus trated further) in the housing ofthe willowing machine 1 and carries at its free end a toothed wheel 63 which meshes with a pinion 65 coupled with the motor 20. The toothed wheel 63 is connected through a toothed belt 67 with the shaft 42 and aligned so that on application ofthe take-off device it engages inthe manner of a push-in clutch in the pinion 65.

Claims (16)

1. Device for drawing off sheets from a sheet stack, with a carrier floor (31) for supporting the sheet stack (11), a take-off roll mechanism (15) which comprises at least one take-off roll (17) arranged above the carrierfloor (31) and driven by a motor (20) about an axis (42) of rotation parallel to the carrierfloor (31) and a feed device (35) forthe sheet stack (11) which moves the carrier floor (31) and the take-off roll mechanism (15) resiliently towards one another, characterised in that between the firsttake-off roll (17), driven by the motor (20) of the take-off roll mechanism (15) and the carrierfloor (31) there is arranged a freely rotatable second take-off roll (19) movablyguided axially parallel in relationtothefirst take-off roll (17) and transversely ofthe rotation axis (42), which second roll in a first position is driven in frictional engagement by the first take-off roll (17) for taking offsheets from the sheetstack (11) and in a second position is lifted away from the first take-off roll (17), inthatseen inthesheet-withdrawal direction ofthesecondtake-offroll (19) at a distance therefrom an abutment (37) is provided at leastforthe upper- most sheet (13) in each case of the sheet stack (11), in thatto thefirsttake-off roll (17) there is allocated a counter-pressure device (23) for the transport of sheets introduced between the two take-off rolls (17, 19) and in that to the second take-off roll (19) there is allocated a control device (45,47) responding to sheets introduced between the two take-off rolls (17, 19), which movesthe secondtake-off roll (19) into the first position in the absence of sheets and into the second position when sheets are present.

2.) Device according to Claim 1, characterised in thatthe second take-off roll (19) is freely rotatably mounted on a control rail (23) which is pivotable axially parallel with the rotation axis (42) ofthefirst take-off roll (17) and initially stressed resiliently to- wardsthefirsttake-offroll (17) and in thatthe control rail (23) carries control faces (47) co-operating with the firsttake-off roll (17) for the control movement of the second take-off roll, the distance of which faces from the pivot axis (25) of the control rail (23) is less than the distance ofthe rotation axis (50) ofthe second take-off roll (19) from the pivot axis (25).

3.) Device according to Claim 1 or 2, characterised in that the second take-off roll (19) is freely rotatably mounted on a control rail (23) which is pivotable axially parallel with the rotation axis (42) ofthefirst take-off roll (17) and resiliently initialIystressedto- wards the firsttake-off roll (17), in thatthefirsttake-off roll (17) comprises circumferential grooves (45) and in that the control rail (23) comprises control faces, especially control dogs (47), which at least in thefirst position ofthe second take-off roll (19) engage in the circumferential groove (45).

4.) Device according to Claim 2 or3, characterised in thatthe control rail (23) consists of a plurality of segments (46) arranged one beside the other in the axial direction, movable in relation to one another and carrying the control faces (47) and the second take-off roll (19) consists of a plurality of take-off cylinders (49) mounted axially parallel on the segments (46).

5). Device according to one of Claims 2to 4, characterised in thatthe control rail (23) is mounted pivotably on the side of the second take-off roll (19) remote from the abutment (37) on a frame (52) ofthe take-off roll mechanism (15) and comprises, at least on the side remote from the abutment (37), counterpressure faces initially stressed resiliently towards thefirst presser roll (17).

6.) Device according to one of Claims 1 to 6, characterised in that the carrierfloor (31) is guided substantially vertically displaceably in a frame (33) and is initially stressed upwards towards the second takeoff roll (19) by means of at least one spring (35).

7.) Device according to Claim 6, characterised in that a stop (41) limiting the upward curvature ofthe sheets is provided on the frame (33) above the carrier floor (31) between the firsttake-off roll (17) and the abutment (37).

8.) Dvice according to Claim 7, characterised in that the stop (41) and the abutment (37) are arranged in such mannerthatsheets resting on the abutment (37) and the stop (41) extend with their edge remote from the abutment between the two take-off rolls (17, 19).

9.) Device according to Claim 7 or 8, characterised in that the stop (41) is fitted pivotably on the frame (33).

10.) Device according to one of Claims 6to 9, characterised in that at least one downwardly protruding tearing tooth (53) which penetrates into the sheet stack in the region of the abutment (37) is arranged on the frame (33).

11.) Device according to one of Claims 6 to 10, characterised in thatthe frame is formed as a container (33) displaceable in relation to the take-off roll mechanism (15), from which stop projections (37) protrude towards one another above the carrierfloor (31) in the region of the take-off roll mechanism (15) and oftheside oppositetothetake-off roll mechanism (15).

12.) Device according to Claim 11, characterised in thatthe stop projections (37) remote from the takeoff roll mechanism (15)form the abutment.

13.) Device according to one of Claims 1 to 12, characterised in that the upper side of the carrierfloor (31) rises towards the middle from the regions ofthe second take-off roll (19) and ofthe abutment (37).

14.) Device according to one of Claims 1 to 13, characterised in thatthe take-off roll mechanism (15) is secured on a processing appliance (1) receiving the sheets, which comprises a drive motor (20), and in thatthefirsttake-off roll (19) is coupled with the drive motor through a drive connection (63,67) which can be disengaged in operation.

15.) Device according to Claim 14, characterised in that it is secured as a unit detachably on the processing appliance and in thatthe take-off roll mechanism is coupled with the drive motor (20) through a push-in clutch (63,65).

16.) A device as claimed in claim 1, substantially as described herein with reference to any one ofthe examples shown in the accompanying drawings.