EP0133818A1

EP0133818A1 - Sheet feeding machines

Info

Publication number: EP0133818A1
Application number: EP84305410A
Authority: EP
Inventors: Kevin John Bond; David Edward Wake
Original assignee: De la Rue Systems Ltd
Current assignee: De la Rue Systems Ltd
Priority date: 1983-08-10
Filing date: 1984-08-08
Publication date: 1985-03-06
Also published as: GB8321518D0; JPS60112549A

Abstract

In sheet feeding apparatus including a detector for sensing multiple feeds, the sheets are fed between two rollers (4, 6) mounted on respective shafts (1,2) extending between side frame members (3). A transducer comprising two relatively movable parts (17,19;25,26-27) is arranged to detect the excessive movement of separation of the rollers when two or more sheets are fed together between them. According to the invention, one end of one roller-carrying shaft (1) is coupled to the corresponding side frame member (3) through a spring (14;24) which allows movement of this shaft end relative to its side frame member. One (19;25) of the two relatively movable transducer parts moves with the spring-mounted end of the shaft (1) and the other (17:26-27) of the relatively movable transducer parts is rigid with the side frame member (3).

Description

This invention relates to machines for the high speed feeding of single sheets and for detecting an increase in thickness in the fed sheets indicative of a double feed. The invention is particularly applicable to a banknote handling machine.
In our copending application no. we have described and claimed a machine for detecting the feeding of multiple sheets comprising first and second parallel rotatable shafts mounted between fixed side frame members and carrying first and second respective rollers, the rollers meeting to form a nip between which the sheets pass, and sheet thickness detecting apparatus comprising a transducer having first and second parts mounted for relative movement to produce a transducer output signal indicative of sheet thickness; the first and second parts of the transducer are mounted on middle portions of the first and second rotatable shafts, respectively, so that the relative motion of the rotatable shafts is conveyed directly to the transducer.
This arrangement required the provision of rigid plates supporting the two parts of the transducer and coupled to the shafts through bearings. The present invention has for its object to simplify the mounting of the transducer.
Sheet feeding apparatus according to the present invention, including multiple-feed detection means, comprises a pair of rollers mounted on respective shafts extending between side frame members, means for feeding the sheets between the rollers, and sensing means comprising first and second relatively movable portions respectively mounted on different parts of the apparatus for detecting displacement of the rollers due to the passage of sheets, characterised in that at least one end of a first of the shafts is coupled to the corresponding side frame member through resilient means allowing movement of the said first shaft end relative to the side frame member, and in that only the first of the said relatively movable portions of the sensing means is mounted for movement with the said end of the first shaft, whereby during passage of a sheet of superimposed sheets between the rollers the said end of the first shaft is deflected and the resultant relative movement of the said first and second portions of the sensing means provides an indication of the multiple feed.
The resilient means is preferably a simple flexural spring; this may be, for example, a spring steel bracket comprising two spaced plane parallel portions connected by another plane portion which, in the normal state, extends at right-angles to each of them. In an alternative construction, the resilient means is a leaf-spring having one end anchored to a mounting means fixed on the side frame member and having its other free end supporting a floating bearing in which the end of the first shaft is supported.
Such an arrangement has the advantage over that disclosed in our above-mentioned earlier application that the mounting of the transducer parts is considerably simplified.
In addition, where the flexural mounting is provided at one end only of the shaft, there is an amplification of the movement of separation of the shafts at the end at which the transducer is connected.
In one embodiment, the sensing means is a linear variable differential transformer. In another embodiment, the sensing means comprises a first portion in the form of a light source and a light sensor mounted on the side frame member in optical alignment to provide a light path between them, the second of the relatively moving portions of the sensing means comprising a light barrier mounted for movement with the shaft end so that relative movement of the shaft end and side frame member causes the barrier to be interposed in the light path to an extent dependent on the size of the relative movement.
In order that the invention may be better understood, an example of apparatus embodying the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 shows the sheet feeding apparatus including the multiple-feed sensor; and
Figure 2 shows an alternative form of shaft mounting in apparatus using a different kind of multiple-feed sensor.

As shown in Figure 1, the sheet-feeding apparatus comprises two parallel shafts 1 and 2 mounted between a side plate 3 and a similar side plate (not shown) at the opposite ends of the shafts. The shaft 1 is a datum shaft and the shaft 2 is the sensor shaft. The datum shaft 2 carries rollers 4 and 5 and the sensor shaft 1 carries rollers 6 and 7 co-operating with the rollers 4 and 5. The rollers 4, 5, 6 and 7, which are freely mounted for rotation on the shafts, are driven in rotation by respective belts 8, 9, lO and 11. When a sheet (for example a banknote) is fed through the system, one end of the sheet passes between rollers 4 and 6 and at the same time the other end passes between rollers 5 and 7.
The datum roller 2 is mounted in the side plate 3 by means of a bearing 12 and is similarly mounted at its other end. The sensor shaft 1, on the contrary, passes through a hole 13 in the side plate 3 and this end of the shaft 1 is connected to one end section of a spring plate 14. As will be seen from the drawing, this spring plate comprises three sections, the end section to which the shaft end is connected, an opposite end section mounted on the side plate 3, and an intermediate section which in the normal position of the sensor shaft extends between the two end sections at right angles to each of them.
In this embodiment, the sensing means, or transducer, is a linear variable differential transformer 15. This transducer 15 comprises a frame 16 which is connected to the side plate 3 and supports the cylindrical body portion 17 of the transducer. To the bottom of the transducer frame 16, there is attached a block 18 of compressible material (for example, silicone rubber) through which passes an armature 19 of the transducer. At its lower end 20, the armature rests upon the sensor shaft 1.
It will be clear that when a sheet passes between the co-operating rollers on the two shafts, the sensor shaft 1 undergoes a movement of separation from the datum shaft 2 and this results in movement at the free end of shaft 1 and flexure of the spring 14, as indicated by the chain-dotted line. As a consequence, the block 18 is compressed and the armature 19 moves further into the body 17 of the transducer, resulting in a change in the transducer output.
The passage of two superimposed sheets between the co-operating rollers results in the greater separation of the shafts and a greater penetration of the armature 19 into the body 17 of the transducer, causing a further change in transducer output.
If desired, the transducer shown in the drawing can be repeated at the other end of the shaft 1 to increase the sensitivity to uneven sheet thicknesses produced, for example, by the presence of adhesive tape at one end of the note.
However, if the spring mounting is provided at one end only, or if the thicknesses between the two pairs of rollers are not the same, the error is magnified at the floating end of the shaft.
It will be seen that this arrangement allows a very inexpensive mounting of the sensor shaft and transducer, since it requires no additional support plates.
In a further arrangement, both shafts may be mounted on one of the side plates by means of flexural springs, and the transducer can be mounted between them, i.e., its body connected to one of the shafts and its armature to the other.
In the arrangement shown in Figure 2, the end of the sensor shaft is mounted in a floating plastics bearing 22 in a moulded plastics box 23. The plastics bearing 22 is supported on the free end of a leaf spring 24 fixed in a mounting block 29 attached to the moulded box 23. A downwardly extending sensor vane 25 is integrally formed with the plastics bearing 22. A light source 26 and a light sensor 27 are fixedly mounted within the moulded box 23 on opposite sides of the vane 25. The box 23 is closed by a removable snap-on lid 28. The light sensor 27 is connected in an electrical circuit, not shown.
It will be evident that the extent to which the movable vane 25 intercepts the beam from the light source 26 in its passage to the light sensor 27, depends upon the extent to which the end of the sensor shaft is deflected by the passage of sheets between the rollers.

Claims

1. Sheet feeding apparatus including multiple-feed detection means, and comprising a pair of rollers (4, 6) mounted on respective shafts (1,2) extending between side frame members (3), means for feeding the sheets between the rollers, and sensing means (15) comprising first and second relatively movable portions (19, 17) respectively mounted on different parts of the apparatus for detecting displacement of the rollers due to the passage of sheets, characterised in that at least one end of a first of the shafts (1) is coupled to the corresponding side frame member (3) through resilient means (14) allowing movement of the said first shaft end relative to the side frame member, and in that only the first (19) of the said relatively movable portions of the sensing means (15) is mounted for movement with the said end of the first shaft, whereby during passage of a sheet or superimposed sheets between the rollers (4, 6) the said end of the first shaft is deflected and the resultant relative movement of the said first and second portions (19, 17) of the sensing means provides an indication of the multiple feed.

2. Sheet feeding apparatus according to claim 1, wherein the second (17) of the relatively movable portions of the sensing means is mounted on the said corresponding side frame member (3).

3. Sheet feeding apparatus in accordance with claim 1, in which the resilient means is a spring (14) mounted to flex in response to movement of the first shaft end relative to the side frame member.

4. Sheet feeding apparatus in accordance with claim 3, in which the spring (14) comprises two spaced plane parallel end portions, a first connected to the shaft end and the second connected to the associated side frame member, and an intermediate portion connecting the two end portions and, in the normal unflexed state, extending at right-angles to each of them.

5. Sheet feeding apparatus in accordance with any one of claims 1 to 4, in which the rollers (4, 6) are freely mounted on the shafts (1, 2) and are belt-driven.

6. Sheet feeding apparatus in accordance with any one of claims 1 to 5, in which both ends of one shaft are connected to their respective side frame members through resilient means allowing movement of the shaft end towards and away from the other shaft.

7. Sheet feeding apparatus in accordance with any one of the preceding claims in which the corresponding ends of both shafts are mounted on one of the side plates through resilient means allowing movement of the shaft ends towards and away from one another, and in which the two relatively movable portions of the sensing means are mounted to move with the respective ends of the two shafts.

8. Sheet feeding apparatus in accordance with claim 3, in which the spring is a leaf spring (24) having one end anchored to a mounting means (25) fixed to the said side frame member (3), the other end of the leaf spring supporting a floating bearing (22) in which the said end of the shaft (1) is supported.

9. Sheet feeding apparatus in accordance with any one of the preceding claims, in which the sensing means is a linear variable differential transformer (19, 17).

10. Sheet feeding apparatus in accordance with any one of claims 1 to 8, in which one of the two relatively moving portions of the sensing means comprises a light source (26) and a light sensor (27) in optical alignment to provide a light path between them and the other of the relatively movable portions comprises a light barrier (25) so arranged that relative movement of the two portions of the sensing means causes the barrier to be interposed to varying extents in the light path between the light source and light sensor.