This invention relates to apparatus for the detection of counterfeit documents and more particularly to apparatus for the detection of counterfeit banknotes or security papers.

Counterfeit documents are a serious problem for people who have to handle documents and supply goods or services in exchange for or as guaranteed by the documents. The most obvious examples are banknotes, bonds, share certificates and similar doquments used in finance and banking, but problems also exist in other less spectacular situations such as forged gift tokens or tickets for a sporting occasion, concert or theatre. In all cases the chances of the counterfeit documents passing undetected are improved the more the person receiving the document is under pressure and therefore the less time the person has to notice or query a suspect document.

Moreover, as counterfeiting techniques have become more and more sophisticated it has become much harder for an untrained person to identify a counterfeit banknote quickly, particularly if the counterfeit note is only one of a number tendered simultaneously.

It is an object of the present invention to provide apparatus that can quickly and reliably detect a counterfeit document.

The present invention is apparatus for detecting counterfeit documents, comprising a gate for receiving a document to be checked, a reservoir for a liquid that will react with in a known way to a component of or an ingredient in the printing or composition of the document, a nib within the gate to be charged with liquid from the reservoir and disposed to apply

the liquid to the document received into the gate, and a seal around the nib to reduce loss of the liquid when there is no document in the gate.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Fig. 1 is a side elevation of apparatus comprising, a reservoir and a gate, according to the present invention before assembly, the gate being partially cut away to show an internal detail;

Fig. 2 is a side elevation of the reservoir and gate of Fig. 1 when assembled, the gate again being partially cut away;

Fig. 3 is a front elevation of the assembly of Fig. 2;

Fig. 4 is a section on the line IV-IV of Fig. 3; and

Fig. 5 is an exploded view of the components of the gate which is again partially cut away.

Referring now to the drawings, apparatus according to the present invention for detecting counterfeit documents comprises a gate 10 and a reservoir 12 which lock together in use but also allow the reservoir to be replaced when its contents are exhausted.

The reservoir 12 is circular in cross section and has a wall 14 extending from the closed front wall 16 of the reservoir to a lip 18 around the periphery of the top of the wall 14 at the rear of the reservoir. The lip 18 carries a plate 20 which seals the rear of the reservoir apart from a central hole surrounded by an axially outwardly extending collar 22. The lip 18 is also provided with a number of projections 23, in this embodiment three such projections, which extend radially outwards, each projection extending counterclockwise from a ramp 24 to a top surface 26 in which is provided a groove 28.

On the interior of the front wall 16 of the reservoir 12 is provided an axially extending wall 32 which surrounds, supports and locates one end of a nib 34 of fibrous material, the other end of the nib 34 being located in and supported by the collar 22 round the hole in the plate 20 at the rear of the reservoir.

The gate 10 consists of two rectangular covers 40 and 42 which are secured together at their bottom flanges by fixing means such as rivets 44. The cover 40 has a central circular wall 46 on its rear surface and an inwardly directed flange 48 at the top of the wall. The flange 48 has three gaps 50 equally spaced around the circumference of the wall and extending outwardly from the inner periphery of the wall. On the inner radial face of the flange are formed three axially extending ridges, each ridge being located slightly clockwise of one of the gaps 50.

At the bottom of the wall 46 the rear end surface of the cover 40 is an inwardly (i.e. forwardly) extending annulus 52 with a central recess 54 which has a central hole passing therethrough. In the recess 54 is secured an annular seal 56 (see Fig.5). Immediately below the recess 54 is a rearwardly extending projection 58.

The cover 42 also has a circular central wall projecting rearwardly and at the top of which is an annular rear end wall 62 around a central recess having a peripheral channel 64, the bottom of the channel 64 lying in the plane 66 between the covers 40 and 42. On the annular end wall of the cover 42 is provided a ring 53 having an adhesive outer surface to allow the device to be secured to a suitable surface when in use.

The top edges 68 and 70 of the covers 40 and 42 are splayed apart to provide a guide path 72 into the plane between the covers, and the side edges of the covers 40 and 42, on their internal

surfaces as shown in the drawings, have a small interfitting recess 74 and projection 75 which are out of the plane between the covers.

The covers 40 and 42 are made of a plastics material which combines the necessary strength with a degree of natural resilience.

In use the reservoir 12 is mounted on the cover by inserting the projections 23 into the holes 50 in the flange 48 so that the projections lie below the flange and then twisting the reservoir clockwise relative to the cover 46 until the ridges on the inner surface of the flange ride up the ramps 24 and engage the grooves 28 to lock the reservoir in position on the cover 40

As seen in Fig. 4 the tip of the nib 34 then extends slightly through the plane between the covers and is surrounded by the seal 56 which engages the bottom of the recess 54 and the front surface beneath the bottom of the channel 64 to seal the nib 34 from the outside atmosphere and restrict or prevent evaporation of the contents of the reservoir from the tip of the nib.

The reservoir is filled with a liquid which reacts in a known way with a component or one or more ingredients within the printing or makeup of a document to be checked, such as a secure paper or banknote, to provide a visible distinction between genuine and counterfeit documents when applied thereto. Preferably the liqμάd leaves virtually no mark when applied to a genuine document bu leaves a clearly visible mark when applied to a counterfeit document.

When a paper or banknote is inserted into the guide path 66 and moved down the plane between the two covers 40 and 42 it encounters the projection 75 within the covers and forces the covers to move apart about the hinge, effectively formed by the

flanges at the bottom of the covers, against the natural resilience of the material of the covers. This movement opens up a path down between the covers by moving the seal and the nib away from the cover 42 allowing paper to pass down beyond the nib while remaining in contact with the nib; the projection 58 acts as a stop limiting the downward movement of the paper by engaging its bottom edge. From this position withdrawal of the paper causes the nib to apply a line of the liquid to the paper and show the paper to be genuine or counterfeit.

The embodiment described may have added to it a light box located behind the guide path so that a banknote left in the guidepath as in a cl p is illuminated from the rear to make visible watermarks and the like markings which are present in genuine banknotes but which may be absent from counterfeits.

A further modification is the addition of a metal detector to detect the metal strip in a banknote as the note is drawn through the gate. The detector causes a visual or audible indication if metal is detected indicative of a genuine banknote.

Further modifications include the use of a refillable reservoir secured to the gate and the use of an absorbent pad within the reservoir.