GB2091701A - Sheet Separating and Restraining Mechanism - Google Patents

Abstract

A sheet separating mechanism including a friction member which resiliently contacts a feed roller is mounted in a holding member and which can be adjusted towards or away from the feed roller. An adjustment member, which is supported adjustably by a carrier, supports the holding member pivotably about an axis, preferably positioned in such a way that an increased clamping effect on a sheet occurs when the sheet is pulled in the feeding direction. <IMAGE>

Description

SPECIFICATION Sheet Separating Mechanism for a Printing and Copying Machine, in Particular a Duplicating Machine The present invention relates to a sheet separating mechanism for printing and copying machines, in particular duplicators, which are to be operable with paper of various qualities. The mechanism is provided with a pivotable friction member having a friction surface that contacts a feed roller in such a manner that several paper sheets fed simultaneously into the gap between the feed roller and the friction member are separated, the sheet in contact with the feed roller being frictionally advanced thereby and the contiguous sheet retained by the friction member.

Such a mechanism will be referred to herein as "of the type referred to".

Known separating mechanisms of this type, see e.g, the Japanese Patent Nos. 31-9991 and 51-24929, are particularly suited for spirit duplicators and similar devices which are not intended for operating with paper of various qualities. They offer, however, operational advantages over other forms of separating mechanism in which use is made of corner separators placed at the front edge of the supply stack together with adjustable side rubbers designed for retaining underlying. sheets.

It is an object of the present invention to provide a separating mechanism of the type referred to which while offering the usual advantages of its type is also adapted to be operated satisfactorily with paper of various qualities, without requiring expensive manufacturing processes with a view to producing machines having sufficient precision and uniformity in operation.

The present invention is based upon the recognition that irrespective of the fact that the friction member abuts resiliently against the feed roller and thus should be able to compensate automatically for any manufacturing inaccuracy due to the fact that the two cooperating parts are mounted independently of one another in the machine, some unacceptable deviations may occur. Whereas it might be supposed that this deficiency could be overcome by an increase of the degree of accuracy in the manufacturing process, for instance by using cast parts instead of parts made of bent sheet metal, this would however increase the cost and result in a more bulky product.

Accordingly the present invention provides a sheet separating mechanism for a printing or copying machine, which mechanism is provided with a pivotal friction member having a friction surface to form a nip with a feed roller in such a way that several paper sheets fed into the nip between the feed roller and the friction member will become separated, the sheet contacting the feed roller being advanced thereby and the underlying sheets being retained by the friction member, wherein the friction member is a holdback member which is mounted pivotably about an axis parallel to the friction surface, the axis is defined by an adjustment member which is slidable towards and away from the friction roller, and two separate adjustment mechanisms are provided, one providing for coarse adjustment of the position of the friction member by locking the adjustment member in a particular position along its path of sliding movement, and the other providing a fine adjustment controlling the limit of pivotal movement of the hold-back member with respect to the adjustment member.

Thus the problem is solved by mounting the friction member, so as to be pivotable about an axis parallel to the friction surface, on an adjustment member displaceable towards and away from the friction roller and able to be releasably fixed in the desired position.

Before leaving the factory, the machines can be subjected to an adjustment resulting in each and every friction member being positioned so as to ensure a uniform operation of all the machines for any quality of paper within a predetermined range of paper types.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the drawings, in which: Figure 1 shows a front view of an embodiment of a sheet separating mechanism according to the invention, and Figure 2 shows a section through the mechanism of Figure 1 along the line lI-Il, and further a feed roller against which the friction surface of the mechanism abuts.

The separating mechanism shown in the drawing comprises a carrier member 1 which may for example be made of metal and is provided with two drilled bosses 2 for screws (not shown) intended for securing the sheet separating mechanism to the front sheet fence 3 of the machine and with two threaded holes 4 and 5 for a mounting screw 6 (serving as a 'coarse adjustment screw') and a fine adjustment screw 7, respectively.

The mounting screw 6 is intended to secure an adjustment member 8 which, when the screw 6 is slackened, is displaceable in relation to the carrier member 1, the screw 6 passing freely through a slot 9 in the adjustment member 8. The displacement is also guided by the second (fine adjustment) screw 7 which likewise passes freely through a slot 10 (aligned with the slot 9) in the adjustment member 8.

At its top the adjustment member 8 is connected by means of a spindle 11 with a holding member 12 provided with two lugs 13 and 14 having clearance-holes for the spindle 11.

The spindle 11 is held in place by means of the circlips 1 a (Figure 1). A friction member 15 made of suitable friction material, for example natural or synthetic rubber foam or polyurethane foam, is secured in a suitable manner, e.g. by glueing or compression fit, to the holding member 12. The holding member 12 has a downwardly extending lever arm 1 6 positioned substantially at right angles to the upper friction surface of the friction member 15, said arm being provided with two slots 17 and 18. The upper slot 17 allows the mounting screw 6 to be loosened to release the adjustment member 8 for sliding towards and away from the feed roller 21 to achieve "coarse" positioning of the friction member 15, relative to the feed roller 21.The lower slot 18 serves a similar function in that it allows vertical movement of the adjustment member 8 (i.e.

movement generally towards and away from the feed roller 21) but also receives the adjustment screw 7 which acts as a second or 'fine' adjustment means for positioning the friction member 1 5 relative to the surface of the feed roller 21 by movement generally chordally of the roller 21 as will be described below. A self-locking nut 1 9 on the fine adjustment screw 7 adjustably limits pivotal movement of the holding member 12 about the spindle 11. A helical tension spring 20 (Figure 1) retains the arm 1 6 in abutment against the nut 19 and thereby fixes the normal position of the holding member 12.Hence, by adjustment of the nut 19, the abutment pressure of the friction member 15 against the feed roller 21 can be finely regulated by means of a lever arm 16 having a greater moment arm between the nut 1 9 and the spindle 11 than the moment arm between the friction member 15 and the spindle 11. Thus 'fine' adjustment of the positioning can be made independently of the coarser adjustable positioning of the adjustment member 8 with respect to the machine by means of the mounting screw 6 which achieves coarse adjustment.

As shown in Figure 1, the helical tension spring 20 is fastened at its ends to horizontally extending bent flanges 1 a of the carrier member 1. Furthermore, Figure 2 shows a lug 1 6a of the arm 16, with the centre of the spring 20 stretched under that lug. Clearly, the effect of the tension in the helical spring 20 suspended between the two flanges 1 a is to lift the lug 1 6a and consequently to pivot the entire holding member 12 in the clockwise direction. This action presses the friction member 1 5 towards the friction surface of the feed roller 21 to close the sheet separating nip therebetween.

A friction clamping plate 22 is drilled to receive, with narrow tolerances, the threaded shanks of the coarse adjustment screw 6 and the fine adjustment screw 7 and serves to clamp the adjustment member 8. This facilitates adjustment of the member 8 in that the screw 6 need only be loosened slightly to allow the adjustment member 8 to be moved vertically against the frictional holding of plate 22 (the plate being fixed in position by its engagement with screws 6 and 7).

The spring 20 not only exerts the abovedescribed action of biasing the holding member 12 for rotation in the anti-clockwise direction in order to assist the fine adjustment of the contact pressure at the nip between friction member 15 and feed roller 21, but also facilitates coarse adjustment in that, once the coarse adjustment screw 6 has been slackened off, the squeezing action between the vibration-resisting strap washer 22 and the supporting member 1 is released and consequently the tension in the bowed coil spring 20 pulls the lug 1 6a upwardly to bias the entire holding member-adjustment member assembly upwardly so as to close the separating nip.

This closing action may, for example, be useful in the setting up procedure by equipping the mechanic with a spacer member which is intended to fit in the nip between the friction member 1 5 and the roller 21. The coarse adjustment screw or "mounting screw" 6 is slackened off and the holding member 12 and the adjustment member 8 carrying it are then pulled downwardly to allow insertion of the spacer member in the nip, whereupon release of the adjustment member 8 will allow the spring 20 to pull both the adjustment member 8 and holding member 12 vertically upwardly into contact with the inserted spacer member with a predetermined force.The mounting screw or "coarse adjustment screw" 6 can then be tightened to lock the adjustment member 8 in its new position, and the fine adjustment can be made either by using a different spacer in the nip, or by observing the efficiency of sheet separating action in use of the machine.

An arrow P in Figure 2 shows the direction in which the sheets are advanced into the gap between the friction member 1 5 and the feed roller 21. It is important to choose precisely this direction and not the opposite, which will appear when a new stack of sheets 3a is to be placed in the paper feed tray (not shown) placed to the left of the front fence 3 in Figure 2. When feeding sheets to the separating mechanism, very often two sheets will be fed, the upper one being frictionally gripped by the rotating feed roller 21 and carried forwardly, while the underlying sheet is frictionally stopped by the friction member 1 5.

If the machine stops in this situation, the formerly underlying sheet will now be squeezed between the friction surface (for example of natural or synthetic rubber foam or of polyurethane foam) of the roller 21 and the friction member 15. it will, however, be possible, on account of the construction and the positioning of the separating mechanism in relation to the feed roller 21, to draw the underlying sheet back, because the holding member 12, under the influence of the withdrawal force, will pivot about the spindle 11 against the action of the spring 20, so as to move the friction member 1 5 leftwardly in generally chordal direction to open the gap between the roller 21 and the friction member 15. This removal could not be performed if the sheets were moving in the opposite direction, cf. the Japanese Patent 51-24929, or if the friction member, as is the case in the structure disclosed in Japanese Patent 31-9991, were pressed against the feed roller in the radial direction, because the generally chordal movement of the friction member in response to forward pulling will be prevented by the nut 19 on the fine adjustment screw 7.

Although in the above description we refer to 'coarse' adjustment generally radially of the feed roller 21 and 'fine' adjustment generally chordally thereof, it will be understood that in the illustrated embodiment both coarse and fine adjustments involve a composite chordal and radial movement and it is the direction of the greater of these two constituent components of movement which is denoted by the terms 'generally chordal' and 'generally radial'. It might seem superfluous to provide two adjustment possibilities in the sheet separating mechanism, as ultimately both adjustments relate to movement towards, and away from, the feed roller. However, the coarser adjustment possibility achieved by the fact that the adjustment member 8 is displaceable generally radially in relation to the carrier member 1 results in some manufacturing advantages.

Instead of making use of pressure diecast parts for the sheet feeding members, which would make it possible to achieve a greater degree of accuracy in manufacture, use can be made of parts of bent sheet metal, which is cheaper and requires less space. A preadjustment of the separating mechanism can be made in the factory, but this does not prevent the user of the machine from making any suitable adjustments in view of the task to be performed and of the paper quality to be used.

The shape of the various parts making up the mechanism according to the present invention is not decisive, provided that the dual adjustment possibility exists. The arrangement of the axis of rotation of the holding member 12 such that the axis on the one hand and the paper insertion passage (the entry to the separating nip between the roller 21 and the friction member 15) on the other hand are on opposite sides of the radial plane of the feed roller, along the line of contact with the friction member, and biasing the friction member 15 against the feed roller 21 during the separating operation, are advantageous for the sheet separation action and for releasing any jam which is to be cleared manually by pulling the jam leftwardly back through the nip.

The holding member 12 and the adjustment member 8 can suitably be made of plastics by injection-moulding and a resilient tongue integral with the arm 1 6 or the adjustment member 8 and abutting against the opposite part can replace the coil spring 20. Alternatively the spring 20 can be replaced by a weight on a lever fixed to the holding member 12. As a further possible alternative, the spring 20 may be replaced by a shorter helical compression spring between the arm 1 6 and the adjustment member 8 positioned coaxially around the fine adjustment screw 7.

The contact surface of the friction member 1 5 can be planar or curved, and can have grooves in the feeding direction P of the sheets.

The friction member 1 5 can be fixed on the holding member 12, for example by adhesive means such as double-sided adhesive tape, or can be arranged for easy exchange, for example with a dovetail connection in the holding member 12.

Claims (9)

Claims

1. A sheet separating mechanism for a printing or copying machine which mechanism is provided with a pivotal friction member having a friction surface to form a nip with a feed roller in such a way that several paper sheets fed into the nip between the feed roller and the friction member will become separated the sheet contacting the feed roller being advanced thereby and the underlying sheets being retained by the friction member, wherein the friction member is a holdback member which is mounted pivotably about an axis parallel to the friction surface, the axis is defined by an adjustment member which is slidable towards and away from the friction roller, and two separate adjustment mechanisms are provided one providing for coarse adjustment of the position of the friction member by locking the adjustment member in a particular position along its path of sliding movement, and the other providing a fine adjustment controlling the limit of pivotal movement of the hold back member with respect to the adjustment member.

2. A sheet separating mechanism according to claim 1, wherein the adjustment member is mounted slidably on a carrier member which is arranged to be releasably fastened to a said printing or copying machine.

3. A sheet separating mechanism according to claim 2, wherein said adjustment mechanisms include respective ones of first and second screws connecting the carrier member to the adjustment member, said screws being engageable in first and second threaded holes in the carrier member and passing through first and second slots, in the adjustment member, said first screw serving to fix the adjustment member in relation to the carrier member for achieving said coarse adjustment while the said second screw serves for adjustment of the contact pressure of the friction member against the feed roller.

4. A sheet separator mechanism according to claim 3, wherein the friction member is a friction lining carried by a holding member which has, at the side opposite to the friction surface and substantially perpendicular thereto and parallel to the adjustment member, an arm with a first slot through which the said first screw can be actuated, and a second slot for the second screw which has a nut which adjustably limits the movement of the arm and hence of the holding member about the axis of rotation, and including a spring keeping the said arm in abutment with the nut.

5. A sheet separating mechanism according to claim 4, wherein said spring is a helical compression spring coaxially around said second screw and positioned between said adjustment member and said arm.

6. A sheet separating mechanism according to claim 4 or 5 wherein movement of said adjustment member by slackening of said first screw in its said first slot is in a direction generally radially of the feed roller, and adjustment of said contact pressure by screwing said nut along said second screw is in a direction generally chordally of said feed roller.

7. A sheet separating mechanism as claimed in one or more of the claims 1 to 6, wherein it is arranged for being mounted in such a way in relation to the feed roller with which it cooperates in the machine that pulling on a sheet which is clamped between the feed roller and the friction member, in a direction counter to the normal feed direction of the sheet, entails a rotation of the holding member releasing the sheet.

8. A sheet separating mechanism according to claim 7, when mounted in a printing or copying machine adjacent a friction feed roller thereof wherein the sheet entry to said nip is to one side of the plane radial to said feed roller and passing through the line of contact between the friction member and the feed roller, and the axis of pivoting of said friction member relative to said adjustment member is on the other side of said plane.

9. A sheet separating mechanism substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawing.