GB2046712A - Sheet-feeding apparatus - Google Patents

Abstract

In apparatus for feeding sheets singly from a stack of sheets, the stack of sheets is urged against a support plate having a bifurcated end (13). The leading edges of the sheets abut a restraining member (15). A drum (5) has suction ports (7) in an arc of its periphery and these impart a transverse curvature to the front sheet, deflecting its leading edge clear of the end of the restraining member (15). The front sheet is fed forward as the drum rotates. To facilitate the feeding of used or worn sheets past the end of the restraining member (15), two sheet-guiding belts (10, 11) move along paths tangential to the drum and parallel to the stack, one on each side of the suction ports and between the ends 13 of the support plate. Additionally the end of the restraining member (15) is sloped on its side facing the leading edge of the sheets and suction ports (20) are provided in the sloped portion to assist in retaining the sheets immediately behind the first sheet. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sheet-feeding apparatus This invention relates to apparatus for feeding flexible sheets singly from a stack at high speed.

British specification No. 938212 discloses a sheet feeding apparatus in which the sheets are urged against a front retaining plate having an opening through which the suction ports of a rotary drum act on the first sheet in the stack to impart to it a double curvature and to feed it past a restraining member placed against the leading edges of the sheets of the stack. The double curvature materially contributes to sheet separation and reduces the likelihood of the multiple feeding of sheets. In addition, British specification No. 938212 discloses the used of a rear sheet restraining means in the form of a fixed vacuum device acting on the rear portion of the face of the front sheet in the stack, the vacuum being periodicaliy removed to permit the periodic feeding of the sheets by the sheet feeding drum in a precisely timed manner.

We have found in practice that whilst the above described apparatus feeds new sheets or sheets in a good condition very successfully, difficulties may arise when handling used or worn sheets or sheets which are naturally soft. For example, the restraining means at the leading edges of the said sheets in the above-mentioned specification has, at the extremity past which the sheets are fed, a sharply defined corner in order to effect reliable sheet separation. This is satisfactory for handling sheets with reasonably intact leading edges but is liable to promote a misfeed or jam condition when handling imperfect sheets, for example used banknotes with worn or torn edges. The chamfering of the corner of the restraining means reduces the number of misfeeds due to imperfect leading edges, but increases the risk of multiple feeding.

According to the present invention, appratus for feeding sheets singly for a first face of a stack of sheets in a direction substantially parallel to the sheets of the stack comprises: stack-retaining means including a retaining member, means for biasing the stack to urge its first face against the retaining member, and a restraining member disposed adjacent the leading ends of the sheets of the stack for normally preventing movement of the sheets in the feed direction; a driven sheetfeeding drum disposed adjacent the leading end of the front face of the first sheet of the stack and having at least one suction port in its peripheral surface, the suction port acting on the first sheet during rotation of the drum to deflect its leading edge clear of the extremity of the said restraining member and to displace the first sheet in the feed direction; and two sheet-guiding belts and means for driving the belts along given paths of movement, the paths of the belts extending in the feed direction substantially tangentially to the drum, one on each side of the suction port or ports and passing closely adjacent the said extremity of the restraining member, whereby the belts contact the first sheet downstream of the suction drum and assist its displacement past the restraining member.

Thus, in apparatus embodying the present invention, the sheet advanced by the suction drum is contacted by the belts along tracks which are outside the central track of the sheet to which a convex curvature was imparted by the drum suction. The belts assist in propelling the sheet to the point at which it can be seized by a further propulsion means in a flow line downstream of the sheet feeder defined above. We have found that the provision of these belts, acting on sheet portions outside the middle track subjected to the action of the suction drum, permits the sheet feeding apparatus to have a greater tolerance to quality and thickness variations in the sheets.

Preferably, the retaining member is a plate having a bifurcated leading end through which the suction drum acts on the first sheet of paper, and the belt paths extend between the two portions constituting the bifurcated end. A subsidiary feature of the present invention is that the extremity of the restraining member, across which the sheets are fed by the suction wheel, is formed so as to slope in the direction facing the stack; the "slope" may be a chamfering of the edge, or the provision of a radiused or curved but non-radial edge. With such an arrangement, the sheets adjacent the front of the stack assume a forwardly stepped configuration when the apparatus is in operation.In the preferred form, this sloping portion at the extremity of the restraining member is also provided with a plurality of small suction ports, the effect of which is to discourage the feeding of more than one sheet at a time. The restraining member is preferably constructed, at least at the said extremity, of a high-friction material.

In order that the invention may be better understood, one example of apparatus embodying the invention is shown in the accompanying drawing, in which: Figure 1 is a perspective view of the salient parts of the apparatus; Figure 2 is a plan view of the apparatus of Figure 1; Figures 3 and 4 are fragmental enlarged schematic front and end views, respectively, of a portion of the apparatus in a static position; Figures 5 and 6 correspond to Figures 3 and 4 but illustrate the apparatus feeding a sheet; Figure 7 is a perspective view of the restraining member of the apparatus, and Figure 8 is a partially cut-away perspective view of the portion of the apparatus indicated by symbol X in Figure 7, drawn to an enlarged scale.

In this example the apparatus comprises a horizontal bed plate 1 upon which is disposed a vertical stationary tubular stub-shaft 2 having fixed thereto an air commutator 3 which incorporates a radial distribution conduit 4. The conduit communicates with the bore of the shaft 2, which is in turn connected to a source of vacuum VI (not shown) by a control valve system of known construction. Disposed concentrically about the commutator in a free-running manner there is provided a 90mm. diameter cylindrical sheet feeding drum, generally indicated by symbol 5, which is driven in a clockwise direction by a notched-belt drive system (not shown).The drum includes on its cylindrical surface an array of arcuately diposed radial conduits 6 which terminate at vacuum ports 7, and axially spaced therefrom in opposite directions, there are annular grooves 8 and 9 which serve to carry respective belts 10 and 11 of circular cross-section. The belts. which are manufactured from polyurethane, are of 2mm. diameter and the grooves 8 and 9 are of such depths that the external extremities of the belts lie 1 mm. below the cylindrical surface of the drum. The radial conduits 6 communicate sequentially with the distribution conduit 4 of the commutator through a predetermined angle of revolution of the drum (see Figure 2).

Also disposed on the bed plate 1 there is provided a sheet retaining means in the form of an upstanding stack support plate 12 having bifurcated extremity 1 3 which straddles the periphery of the feeding drum 5. The support plate 12 is provided with a vacuum hold-back device VHB which is connected to a source of vacuum V2 via a control valve (not shown). The purpose and construction of the hold-back device and its associated control valve are fully described in UK patent No. 938212, but briefly, it serves to provide a precise time control for the release of each sheet into the flow-line. The control valve is phased in unison with the rotation of the vacuum feed drum so as to release a sheet at each revolution of the drum thereby to define an exact time interval and linear separation between sheets fed along the flow-line.

A stack of sheets S, disposed on edge upon the bed plate 1, is biassed towards the support plate 12 by means of a spring-loaded pressure pad member 14, the construction of which is well known in the sheet handling art.

The leading end of the stack is located by means of a fixedly mounted restraining member 1 5 disposed normally to the support plate 12. The said member comprises a horizontally extending body portion 1 6 having an extremity 17 which, in end view, is seen to be convex, with a radius of 60mm. In plan view, the extremity 17 merges with a stack-abutment face 1 8 via a radiused corner 19. The corner 1 9 may comprise a radius of between 3 and 1 Omm., but we have ascertained that 5mm. is particularly suitable for handling used bank-notes. Alternatively, the corner may be chamfered or comprise a convex profile of nonradial configuration.The member is adjustable in a direction Y by screw means, not shown, to provide a predetermined "mesh" with respect to the working surface of the stack support plate 1 2.

The radiused portion 1 9 of the restraining member is drilled at 20 to provide five 1.5mm diameter vacuum ports 21 which collectively serve to arrest sheets tending to move forward with the frontmost sheet. The ports 21 communicate with a source of vacuum V3 via a vertical pipe 22 and a manifold 23, defined by a cavity formed in the side of the body portion 1 6 and a detachable cover plate 24. The effective port areas of the three innermost ports are increased by means of 1 mm. grooves 25 (see especially Figure 8).

The belts 10 and 11, which are in endless form, are each carried upon two jockey pulleys 26, 27 and 28, 29 respectively. The pulleys 26 and 28 are freely mounted upon a common vertical shaft having a fixed axis Z positioned so that the portions of the belts between the feed drum 5 and the pulleys 26 and 28 are disposed substantially parallel to the output flow-line FL and to the working surface of the stack support plate 12. The jockey pulleys 27 and 29 are independently mounted upon the ends of respective pivotal levers, one of which is indicated by symbol 30 (see Figure 2). The levers are spring-biased in a clockwise direction, as shown by the arrow, to tension the belts in substantially constant manner.

Sheets fed from the front of the stack by the feeding drum are seized between opposed sets of traction belts which are indicated by the chain dotted outlines 31 in Figure 2. For clarity, only one set of belts 31 is shown, in chain-dotted lines in Figure 1.

OPERATION OF THE APPARATUS The restraining member 1 5 is adjusted in a direction Y so that its convex extremity 17 very lightly contacts the belts 10 and 11 when the apparatus is in its static condition (see Figure 4).

Upon positioning a stack of banknotes S against the stack support plate 12 and actuating the pressure pad member 14 the banknotes will assume the position shown in Figure 3.

Upon creation of vacuum in the system and energisation of the driving mechanism of the apparatus the feed drum 5 rotates in a clockwise direction, the belts 10 and 11 move ;nearly (see Figure 5) and the operative surfaces of the traction belts move in the direction of the flow-line (see Figure 2). A feeding cycle commences when the conduits 6 of the drum align in turn with the conduit 4 of the commutator 3 and vacuum is applied to the ports 7 which causes the leading end of the frontmost banknote S1 of the stack to adhere to the drum. The central portion of the leading edge of the banknote tends to follow the curvature of the surface of the drum and upon release of the hold-back device VHB it moves forward and passes across the extremity 1 7 of the restraining member 1 5.

Immediately prior to the cut-off of vacuum at the leading ports of the drum by the commutator 3 the lateral portions (viz on either side of the central portion) of the banknotes are restrained from following the drum by the bifurcated ends 1 3 of the supported plate 12, thereby creating transverse curvature to the banknote. The said lateral portions are further restrained by the belts 10 and 11 which effectively serve to propel and guide the banknote along the fiow-line FL and into the nips of the traction belts 31.

From Figure 5 it will be seen that the subsequent banknotes have move forward in stepped formation against the radius 1 9 of the restraining member but these are retarded by means of the five vacuum ports 21 formed therein.

When the banknote S, passes clear of the feed drum the following banknote will be exposed to the feed drum but will be braked by the vacuum hold-back device until the appropriate'release time thereby to initiate a further feeding cycle.

We have found that the apparatus described provides a greater tolerance to variation in sheet thickness and variation in sheet quality than the previously known apparatus, in which such variations, especially at the leading edges of the sheets, sometimes resulted in jams. We attribute the improvement mainly to the fact that in addition to the vacuum drum, which applies suction to and causes convex curvature at a middle track of the leading end of the sheet and initiates movement of the sheet, we provide belts which provide a degree of propulsion to the portion of the sheet which has left the vacuum drum, along tracks on each side of the said middle track to which the convex curvature was imparted by the drum, the belts providing this propulsive effect and preventing the moving sheet from bending beyond the plane of the retaining or support plate up to the point at which the sheet is seized by a propulsion means in the flow line downstream of the sheet feeder described.

Another factor of considerable importance in this increased tolerance to variation in sheet thickness and quality is the chamfered or radiused "corner" facing the sheets in the stack at the extremity of the leading edge restraining member, in combination with the provision of suction ports on this chamfered or radiused face.

These suction ports, which are in contrast to the compressed air port proposed in the earlier British specification No. 938212, do not exert a high degree of suction on the sheets but are sufficient to discourage these sheets from moving with the first sheet, especially when the restraining member (at least at its extremity) is of a high friction material.

Claims (12)

1. Apparatus for feeding sheets singly from a first face of a stack of sheets in a direction substantially parallel to the sheets of the stack, comprising: stack-retaining means including a retaining member, means for biasing the stack to urge its first face against the retaining member, and a restraining member disposed adjacent the leading ends of the sheets of the stack for normally preventing movement of the sheets in the feed direction; a driven sheet-feeding drum disposed adjacent the leading end of the front face of the first sheet of the stack and having at least one suction port in its peripheral surface, the suction port acting on the first sheet during rotation of the drum to deflect its leading edge clear of the extremity of the said restraining member and to displace the first sheet in the feed direction; and two sheet-guiding belts and means for driving the belts along given paths of movement, the paths of the belts extending in the feed direction substantially tangentially to the drum, one on each side of the suction port or ports and passing closely adjacent the said extremity of the restraining member, whereby the belts contact the first sheet downstream of the suction drum and assist its displacement past the restraining member.

2. Apparatus in accordance with Claim 1 in which the retaining member is a plate having a bifurcated leading end through which the suction drum acts on the first sheet of paper, the extremities of the bifurcated end projecting beyond the restraining member and one on each side of the restraining member, the belt paths extending between the said extremities.

3. Apparatus in accordance with claim 1 or 2, wherein the said extremity of the restraining member is formed so as to slope in the direction facing the stack, so that sheets adjacent the front of the stack assume a forwardly stepped configuration.

4. Apparatus in accordance with claim 3, in which the said sloping face of the extremity of the restraining member is provided with suction means, for connection to a source of suction, to discourage the feeding of more than one sheet at a time.

5. Apparatus in accordance with claim 4, in which the suction means comprises a pluralirl of suction parts, at least one of which is extended by a groove formed the surface of the said sloping face.

6. Apparatus in accordance with any one of the preceding claims, in which the said extremity of the restraining means is convex in a direction transverse to the feed direction.

7. Apparatus in accordance with claim 6, in which at least the extremity of the restraining member is made of a high-friction material.

8. Apparatus in accordance with any one of the preceding claims comprising grooved rotary members fixedly mounted with respect to and coaxial with the drum, the belts passing round the said grooved members.

9. Apparatus in accordance with claim 8, in which the said drum comprises a circumferential groove between each end of the drum and the suction port or ports, the belts being carried in the said grooves.

10. Apparatus in accordance with claim 9, wherein each belt extends around two pulleys and the drum, the axes of all the pulleys being parallel to the axis of the drum, and in which the shaft of one of the pulleys is pivotally mounted and is resiliently biased to maintain a substantially constant belt tension.

11. Apparatus in accordance with any one of the preceding claims, further including a rear restraining member comprising a suction port which is connected to a source of suction and which is periodically disconnected from the said source in timed relationship with the rotation of the said drum to release a sheet which has been subject to the action of the drum suction port.

12. Apparatus for feeding sheets singly from a stack of sheets, substantially as herein described with reference to the accompanying drawings.