Document feed systems are generally based on friction or vacuum methods and examples of vacuum based apparatus are described in EP-A-0445514, US-A-2956804, US-A-3782716 and US-A-2004882. US-A-4008889 also describes a vacuum feed system comprising a document stack hopper for supporting a stack of documents, the hopper having a planar base part slidable in a feed direction while carrying a lowermost document in the stack; a drive system for cyclically sliding the base part to and fro beneath the stack; and a feed assist system for selectively assisting the feeding of documents by the base part, the feed assist system comprising a vacuum generating system for selectively applying vacuum to a port extending through the base part, wherein movement of the base part in the feed direction generates a vacuum in a chamber communicating with the port while movement of the base part in the opposite direction stops the generation of vacuum.

A draw-back of this apparatus is that as the base part slides back beneath the stack hopper, air is expelled though the vacuum chamber which can disturb the documents in the stack.

In order to overcome this problem and in accordance with the present invention, we provide a document feed assembly characterised in that the assembly further comprises a bleed port coupled with the vacuum chamber and to a control system which closes the bleed port when a vacuum is being generated and opens the bleed port when a vacuum is not being generated.

The invention overcomes the problem mentioned above by providing a control system which opens the bleed port when

the vacuum is not be generated thus allowing air to escape without having to pass through the vacuum port.

The vacuum system preferably includes a linear evacuating device such as a bellows or piston pump driven sympathetically with the action of the base part, vacuum being applied at desired points in the movement of the base plate either electro-mechanically or wholly mechanically to optimise performance.

Thus, in one example, the vacuum system comprises a bellows coupled to the base part so as to be expanded as the base part moves in the feed direction and contracted as the base part moves in the opposite direction.

The bleed port control system could be a passive one- way valve but preferably is coupled with the base part so as to be actuated upon movement of the base part. This enables the control system to be actively and positively controlled. For example, the bleed port control system may include a cam follower arrangement which could be either directly mechanically coupled to a closure member for the bleed port or electrically coupled. The advantage of positive control is that the bleed port can be opened after the base part has moved to its extended position so as to release a document in contrast to the prior art in which the downstream feed system must"pull"the document away from the vacuum.

Typically, it is necessary to provide some means for ensuring that only single documents are fed from the stack.

In the preferred example, one or more separating members are located above the position of the base part when the base part is moved in the feed direction, the location of the separating member (s) being chosen so as to prevent more than one document being fed. The separating members may comprise contra-rotating rollers, stationary blocks, or any other conventional separator system.

It is important that the gap defined between the or each separating member and the base part is carefully controlled. Typically, this involves regular inspections

and, if necessary, manual adjustment of the position of the separating members. However, one of the significant advantages of the present invention is that the or each separating member may be mounted on a support which is guided to follow transverse movements of the base part. In this way, the separation gap can be maintained irrespective of the vertical position of the base part.

There are a variety of ways in which the support may be guided. For example, the support could be journalled in bearings in opposite side plates of the assembly while a follower depends from the support onto the base plate.

Conveniently, however, the or each separating member comprises a roller supported on a shaft which is mounted in bearings which rest on the base part.

A further advantage of the present invention relates to its use with detection systems.

Conventionally, document detection systems for verification and validation such as pattern, magnetic, W and IR are built into the transport of the host system and not included in the feed mechanism. This requires such features to be read at the speed at which the host processes the documents, which may be up to 12 m/s. With the new assembly, there is no relative movement between the base part and the lowermost document whilst the document is being fed. Thus, one or more detection devices could be included in the base part to observe the document while it remains stationary with respect to the base part and so without the disadvantage of dealing with relative motion between the document and the detector. Furthermore, the distance of the document from the detector (s) is well defined.

Some examples of document feed assemblies according to the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic side elevation of a first example with the feed plate retracted ;

Figure 2 is a schematic side view of the first example with the feed plate extended; Figures 3 and 4 are views similar to Figures 1 and 2 but of a second example; Figures 5A to 5C are side, front and plan views respectively of a separation system which can be used in either the first or second example; and Figures 6A and 6B are a plan and side view respectively of an alternative separation system.

The example shown in Figures 1 and 2 comprises a document stack hopper 100 having a planar base or feed plate 3 on which a stack of documents such as banknotes 101 is provided in use. The hopper 100 also includes a guide plate 4 having an angled section 4a at its base which defines a gap 4b with the feed plate 3.

The feed plate 3 is mounted for reciprocal, sliding movement beneath the stack 101, the movement being controlled by a motor 110 which rotates a drive eccentric 1. The drive eccentric 1 is connected via a drive pin la with a con-rod 2 which, in turn, is connected via a drive pin 2a to the feed plate 3.

Figure 1 illustrates the feed plate 3 in its fully retracted position while Figure 2 illustrates the feed plate in its fully extended position.

The feed plate is ported at 12a and connected via a manifold at 12 to a vacuum chamber 9a of a vacuum pump 9.

In the example shown, the pump 9 is in the form of a bellows, however, a piston style pump could be used. The manifold end 12 of the bellows reciprocates sympathetically with the feed plate 3 and the opposite end is fixed via a mounting bracket 8 to part of the machine casing (not shown). This means that the reciprocating action of the feed plate 3 also performs the action of actuating the bellows.

A bung 10 performs the action of sealing a bleed port 9b of the bellows in order that a vacuum may be applied.

The bung 10 is actuated by the action of a cam follower 17

running against a fixed cam surface 16. The cam follower is driven by the action of the feed plate 3.

Documents, once picked, are guided into a "conventional"transport system comprising belts or rollers by guide plate 4. In the example described, rollers 6,7 are shown as being the document transport medium.

Doubles are separated by a contra roller 5 which counter rotates a fixed distance from the feed plate 3 which is defined as being more than a single document thickness but less than a multiple document. A method of maintaining this required distance is described later.

Documents, once picked, are transported away by transport pinch rollers 6,7. The lower pinch roller 6 is not shown for reasons of pictorial clarity, suffice to say that the roller would overlap the leading edge of the feed plate.

Figure 1 shows the feed plate 3 fully retracted prior to pick. In this position, the cam surface 16 lifts the cam follower 17 and hence, via the bung 10, seals the bleed" port 9b of the bellows 9. As the feed plate 3 is driven forwards (from left to right on the sketch), the bellows is expanded and hence applies a vacuum to the lowermost document via the manifold 12 and ports 12a. The document thus moves with the feed plate 9.

Figure 2 shows the feed plate fully extended towards the transport pinch, at this point the bellows 9 is also fully extended. At this point, the profile of the cam surface 16 allows the bung 10 to open the bleed port 9b and hence release the vacuum and allow the document to progress into the transport by the action of the transport pinch rollers 6,7.

The counter rotating action of the contra roller 5 that is shielded from damaging the documents by the guide plate 4 against the feed plate 3 restrains the feeding of multiple documents in this example, however other separation means could be employed, e. g. friction balance, corrugation, etc. (See Figure 6.)

An optional document detector 50 is shown mounted to the underside of the feed plate 3, so as to move with the feed plate, in alignment with a window extending through the feed plate 3 so that the facing surface of the lowermost document in the stack 101 can be seen. The detector 50 can be of any conventional type as used, for example, for determining validity and authentication of documents of value such as banknotes. Examples include pattern, magnetic, W and IR detectors. The detector 50 (and other detectors if provided) is positioned beneath the expected position of the characteristic to be sensed and is connected to a conventional microprocessor which controls overall operation of the apparatus.

In this example a direct acting single bellows is described as the means by which the vacuum is generated, however multiple bellows/piston pumps (or any other linear device) may be employed which may have their stroke optimised by, for example, a lever action.

As an alternative to a cam and follower action directly opening and closing the bellows bung 10, the action can be achieved by using a solenoid and microswitch cam follower. See Figures 3 and 4.

In this instance, the bleed port 9b and bung 10 are stationary with respect to the reciprocating feed plate 3, however the bellows 9 is sealed to pick a document by the action of an electrical device such as a solenoid 11 which is fixed to the mounting bracket 8. The switching action of the solenoid 11 is controlled by a cam surface 13, which is mounted on the feed plate 3 and hence reciprocates with said plate, acting against the follower 14 of a device such as a microswitch 15. Figure 3 shows a view of the microswitch 15 switching the power supply directly to the solenoid 11, however, the microswitch could be part of a relay circuit.

As an alternative to the cam and microswitch, an optical device and control flag could be employed, with the flag blocking the passage of light across the optical

device when the feed plate is in the appropriate position and hence triggering the solenoid.

The remaining elements of the design such as the drive mechanism for the feed plate, document separation and transportation remain unchanged from that described in Figures 1 and 2.

Figure 3 shows the feed plate 3 fully retracted prior to pick. In this position, the cam surface 13 depresses the cam follower 14 of the microswitch 15 and hence switches power to the solenoid 11. The energised solenoid 11 closes and hence, via the bung 10, seals the bleed port 9b. As the feed plate 3 is driven forward (from left to right in the drawing), the bellows 9 is expanded and hence applies a vacuum to the lowermost document via the manifold 12 and ports 12a. The document thus moves with the feed plate.

Figure 4 shows the feed plate fully extended towards the transport pinch, at this point the bellows 9 is also fully extended. At this point, the profile of t~he~ cam surface 13 opens the microswitch 15, de-energises the solenoid 11 and allows the bung 10 to open the bleed port 9b. Hence the vacuum is released and allows the document to progress into the transport by the action of the transport pinch rollers 6,7.

Figures 5A to 5C illustrate the manner in which the separating components are mounted in Figures 1 to 4. The contra roller or rollers 5 are non-rotatably mounted on a contra mounting shaft 18 which itself is rotatably mounted and supported a fixed distance above the feed plate 3 in datum bearings 20. The datum bearings 20 are placed outboard of the document path and are biased against the feed plate 3 by datum springs 19. Linear or rotary mounting systems may be used to support the contra/shaft system. In the illustration, the datum bearings 20 are supported on swinging arms 21 that are pivoted on drive shaft 22 which in turn is rotatably mounted from the feeder chassis via bearings 26. The pivoting action of the

swinging arms is independent of the drive rotation of shaft 22. The datum springs 19 act upon these swinging arms.

These springs may be of extension, torsion, compression or cantilever in nature, the illustration showing a design based on the use of compression springs, fixed to the feeder chassis and acting on the swinging arms 21. Reverse drive can be provided to the contra rollers 5 by a number of means such as via a gearbox transmitting rotary motion from the host system, or by an independent gear motor. In this instance, an eccentric drive 23, transmission yoke 24 and one-way clutch 25 transfers drive from the drive shaft 22 of the host system.

The contra gap is defined by the difference in radius between the datum bearings and the contra roller.

The feed assemblies described can be used in a wide variety of different applications including document counters, sorters and dispensers as will be readily apparent to a person skilled in the art.

Figures 6A and 6B illustrate an alternative separation system for use in either of the examples of Figures 1 and 2. In Figures 6A and 6B, the counter rotating contra roller 5 is rigidly but rotationally mounted facing a rigidly mounted separator roller 5a. This roller 5a is driven in a direction which is complementary to the feed direction of the feed plate 3 and either it or the contra roller 5 is capable of adjustment to define a gap or corrugation or combination of both through which only a single document at a time may pass.

Figures 7 and 8 demonstrate a possible friction assist arrangement and Figures 9 and 10 demonstrate a system whereby the vacuum pick is completely replaced by a friction pick mechanism.

To assist the feed function of the base plate 3, the base plate may be provided on its upper surface with a high coefficient of friction material.