GB2114546A - Sheet feeding device - Google Patents

Abstract

A shaft (10) with flap (12) rotates in the direction of arrow (11) each time a sheet is to be fed. A stripper element in the form of a resiliently flexible flap (12) bearing a high friction layer (31) wipes against the top sheet (24) of a stack (26) to initiate sliding of the top sheet off the stack. The sheet advances in the direction of arrow (32) between the flap (12) and a reject roller (34) which rotates in the same direction as the flap (12) and shaft (10). The coefficients of friction of the flap (12) and reject roller (34) are chosen so that if two sheets are fed, the lower one is returned to the stack by the reject roller (34). The use of such a flap to separate sheets ensures that the sheets are fed without damage or marking. <IMAGE>

Description

SPECIFICATION Sheet feeding device The present invention relates to a sheet feeding device for feeding sheets from a stack, comprising a stripper element which isona rotatable shaft perpendicularto the direction of advance movement and which element bears on the top sheet of a stack of sheets to initiate sliding the top sheet off the stack.

In another known stripper device, the stripper element is formed by an oscillatory mass fixed to one end of a rod, the other end of which is eccentrically pivoted on the rotary shaft. In each revolution of the shaft, the oscillatory mass strikes against the top sheet of the stack of sheets and, by virtue ofthe resulting impact, the first sheet ofthe stack is separated from the sheets disposed therebelow.

Such a device suffers from the disadvantage of leaving an impression on the sheets at the point at which the oscillatory mass strikes against the sheet, thereby jeopardizing subsequent uses of the sheets.

The object of the present invention is to provide a stripper device which is capable of reliable separating and advancing the first sheet of a stack of sheets, without leaving impressions or other markings on the sheets.

The sheetfeeding device according to the present invention is defined in claim 1 below.

The invention will now be described in more detail, byway of example, with reference to the accompanying drawings, in which: Fig. lisa perspective view of part of a sheet feeding device embodying the invention, Fig. 2 is a view in longitudinal section of the device shown in Fig. 1, Fig. 3 is a view in section taken along line Ill-Ill in Fig.

2, and Fig. 4 shows an example of application of the device according to the invention as shown in Fig. 1, to a copying machine.

In a sheet feeder in which the sheets are individually withdrawn from a stack 26 in a container 27 (see Figs. 1 and 4), it is necessaryto ensure that additional sheets are not entrained together with the first sheet.

The device embodying the invention comprises a shaft 1 0 which is perpendicular to the direction of advance movement and parallel to the top surface of the top sheet 24 and which is rotatable intermittently in an anti-clockwise direction, as indicated in Fig. 1 by an arrow 1 1.Athin, curved and resilientlyflexibleflap 12 is fixed on the shaft 10 by means of a screw 16. The flap 12 is made from a thin sheet of elastic material, for example steel.

The flap 12 is bent rearwardlywith respect to the direction of rotation 11, substantially in accordance with a spiral arc, in such a way that, when it is in the rest position, the distance thereof from the shaft 10 increases in proportion to increasing distance from a fixed end l4towardsthe distal end 18 oftheflap 12.

During the rotary movement of the shaft 10, the flap 12 drags a portion indicated at 22 against the top surface of the top sheet 24 ofthe stack 26 which is contained in the container 27. The length of the portion 22 of the flap 12 is not precisely defined insofar as it is determined by the height of the stack or the distance of the sheet 24from the shaft 10. The surface 30 of the flap 12 which is towards the sheet 24 is covered by a layer 31 of material with a high coefficient of friction, for example soft rubber. The coating 31 applies two the sheet 24 a frictional force which is higher than the frictional force between one sheet and another, and is sufficient to move it in the direction indicated by the arrow 32.

A roller34which is referredto as a reject roller is fixed on a shft 36 which is parallel to the shaft 10, and is continuously rotated in the same direction as the shaft 10, as indicated by an arrow 37. In each revolution,theflap 12 comes into engagementwith the roller34 and consequently each sheet which is entrained by the flap 12 is brought into engagement with the roller 34, between the flap 12 and the roller 34.

The roller34 is formed of a material having a coefficient offriction relative to the paper which is less than the coefficient of friction of the layer 31 on the flap 12, but still higherthanthe coefficient of friction as between one sheet and another.

In the region of contact between theflap 12 and the roller 34, the peripheral speed ofthe roller 34 is ofthe same magnitude as the peripheral speed oftheflap 12, but in the opposite sense, that is to say, towards the container 27.

In this way, the roller34 does not impede the advance movement of a single sheet in the direction 32, but repels any second sheet which may be taken bytheflap l2atthesametimeasthefirstsheet.

In orderto improve the effect of separation of the sheets by means of the roller 34 and the flap 12, the flap 12isformed bytwo parallel tongues 18Aand 18B which are spaced by a distance D1 (see Figure 3) that is equal to about double the thickness D2 of the roller 34.

In this way, the two tongues 18A and 18B, interfering with the periphery 35 of the roller 34, form a small hump 42 in the sheet 24 which permits any second sheet to be easily separated from the first and entrained by the action of the roller 34.

The sheet feeding device according to the invention can be suitably used in a copier machine 44 (see Fig.

4).Thecopiermachine44comprisesan exposure surface 50foran original 51 to be copied, an optical system for reflecting the image of the original onto a rotary drum Ton which an electrostatic image of the original is formed and developed. Afeed device 53 transports the sheets which are selectively taken from oneorotheroftwo containers 27 and 27' arranged within the copier machine 44 on a support 45 (see Fig.

2) towards a transfer station 55, by means of a belt 54 and rollers 58. The sheets are successively transfer- red to a fixing station 56 and then discharged into a collecting means 57.

When a sheet 24 is to be fed forward, the shaft 10 is set in rotation by a coupling of known type (not shown in the drawings), which causes the flap 12 to perform a rotary movement of 360 at an angular speed which isforexample between 50 and 100 revolutions per minute. Atthesametime,the roller34 is rotated at a speed for example of 200 revolutions per minute, in the direction indicated by the arrow 37, to resist the movement therepast of any second sheet. During its rotary movement in the direction indicated by the arrow 11 (see Figs. 1 and 2), the flap strikes by means of its portion 22 against the first sheet 24 in the stack 26 in the central region and in the vicinity of the front edge thereof.By an impact effect, the sheets in the stack 26 are compressed at the location ofthe region againstwhich the flap 12 bears, and consequently the first sheet is transversely curved, raising the side edges. In this way. the first sheet is separated from the subsequent sheets and can be advanced in the direction 32 by the effect of the friction between the rubber coating 31 and the sheet 24.

If other sheets beside the first sheet are also entrained, when those sheets are fed between the flap 12 and the roller 34, the first sheet 24 continues towards the rollers 62, whereas the other sheets disposed belowthefirst sheet are held back by the action ofthe roller 34.

A single sheet of paper 24 thus passes over the roller 34 and is pushed forward by member 12 until it is engaged by two rollers 62, to be advanced in a direction 64. A guide member 66 co-operates with each roller 62, the member 66 being pivoted on a shaft 68 and normally being capable of guiding the sheet24around the rollers 62, over an arc of about 180 , for directing it correctly towards the feeder 53, in the direction indicated at 64.

The guide member 66 is connected by a pin and slot connection to the armature 69 of a solenoid 70 while being connected by means of a connecting link 71 to a crank 73 fixed to a shaft 79.

The member 66 can be selectively rotated by the solenoid 70 into two positions, ofwhich the position shown in solid lines in Fig. 2 is the normal sheet feed position. In a second position 72 as indicated by dash-dotted lines in Fig. 2, the member 66 permits movement therepast of sheets 74 arriving on a path 75 (see Figs. 2 and 4) from the copier machine 44 during the double copying phase, after having been copied on one face.

In that phase, the guide member 78 which is pivoted on the bar 79 is held in the position shown in dash-dotted lines in Fig. 2 bythe solenoid 70 while in the phase of feeding sheets from the container 27, it remains in the position shown in solid lines.

Itwill be appreciated that various modifications may be made in the above-described device without departing from the scope of the invention as claimed hereinafter. For example, the flap 12 need not have the gap D1 (see Fig. 3), in which case it bears against the roller 34, compressing the sheets 24 in the phase offeeding towards the rollers 62. There may be a plurality of the flaps 12 spaced along the shaft 10.

Claims (6)

1. A sheetfeeding device forfeeding sheets from a stack, comprising a stripper element which is on a rotatable shaft perpendicularto the direction of advance movement and which element bears on the top sheet of a stack of sheets to initiate sliding the top sheet off the stack, characterised in thatthe stripper element comprises a resilientlyflexibleflap extending in an arc aboutthe shaft so that, in each revolution of the shaft, the flap strikes the top sheet of the stack to detach and initiate the sliding of the top sheet off the stack.

2. A device according to claim 2, wherein the flap is covered on the surface which strikes the top sheet with a layer of material having a high coefficient of friction.

3. Adeviceaccordingto claim 1 or2,whereinthe flap extends away from the shaft in the shape substantially of a spiral arc.

4. A device according to any one of claims 1 to 3, further comprising a reject roller which rotataes concurrently with the shaft and which co-operates with flap to repel any second sheet which is entrained by the top sheet.

5. A device according to any ofclaims 1 to 3, wherein the flap comprises a plurality of laterally spaced tongues which are parallel to each other.

6. A device according to claim 4 and claim 5, wherein the reject roller acts in the space between two tongues oftheflap.