Friction wheel separator for separating sheetlike items

A friction wheel singler is proposed for singling sheet material, in particular bank notes, comprising sheet magazine 5 for receiving stack of sheets 1, singling cylinder 2 having one or more friction elements 4 for contacting and conveying sheet 1a to be singled out of the magazine, and retaining device 3 forming with singling cylinder 2 singling gap 7 through which sheets 1a to be singled out of the magazine are conveyed one by one, retaining device 3 having one or more friction areas 3a for contacting sheets 1a to be singled out of magazine 5. Friction elements 4 of singling cylinder 2 and friction areas 3a of retaining element 3 have the same friction material, whereby different frictional forces transferred to sheet 1a by singling cylinder 2, on the one hand, and retaining device 3, on the other hand, are obtained by selecting the contact area between friction elements 4 of singling cylinder 2 and sheet 1a to be singled to be substantially larger than the contact area between friction areas 3a of retaining element 3 and sheet 1a to be singled. Any further contact areas of retaining device 3 and/or singling cylinder 2 with the sheet to be singled have a substantially lower coefficient of friction than the friction material of friction elements 4 of singling cylinder 2 and friction areas 3a of retaining element 3. According to a special aspect of the invention, it is proposed that the sheet material is deposited in sheet magazine 5 on driven feed rolls 11 to 14 to guarantee a reliable supply of sheets to be singled to singling gap 7 regardless of the stack height.

BACKGROUND

This invention relates to a friction wheel singler for singling sheet material, in particular bank notes, comprising a sheet magazine for receiving a stack of sheets, a singling device with a singling cylinder having one or more friction elements for contacting and conveying a sheet to be singled out of the magazine, and a retaining device forming with the singling cylinder a singling gap through which sheets to be singled out of the magazine are conveyed one by one, the retaining device having one or more friction areas for contacting sheets to be singled out of the magazine.

Friction wheel singlers are used for quickly singling stacks of sheets, for example bundles of bank notes, in the transverse or longitudinal direction so that the singled note can be supplied to a sensor system for determining the authenticity, qualitative nature, value or other characteristic properties of the note.

Friction wheel singlers are based on the principle of a singling cylinder attacking the surface of a note of a bank note stack for example, this specifically contacted note being conveyed in a transport direction due to friction by rotation of the singling cylinder while the other notes of the bank note stack are retained by a retaining device. The retaining device and singling cylinder form for this purpose a singling gap through which the note is conveyed. The retaining device can slightly engage grooves of the singling cylinder, the engagement depth being adjustable. To ensure that the note contacted by the singling cylinder is conveyed and the other notes of the bank note stack retained, a higher force must be exerted on the note in the singling gap by the singling cylinder than by the retaining device on the opposite side of the gap. Therefore, the singling cylinder is usually provided with friction elements whose friction linings have a substantially higher coefficient of friction than the corresponding friction linings of the retaining device, the ratio of coefficients of friction being about 2:1 for example.

It proves to be disadvantageous that the different friction materials of the singling cylinder and the retaining device partly show very different operating characteristics, for example with respect to resistance to environmental influences, moisture absorption, temperature coefficient, aging and wear resistance. This can lead to different service lives and influences the ratio of friction, which can lead to singling errors or even double picks, i.e. more than one sheet being grasped by the singling cylinder.

Singling errors can also occur for other reasons. It is thus usual for the stack of sheets to rest on a supporting plate in the sheet magazine, with feed rolls disposed on a common axle protruding out of the front area (in the sheet transport direction) of the supporting plate in the manner of a hopper. Said feed rolls contact the underside of the lowermost sheet of the stack, thereby lifting the stack from the supporting plate in this area, and convey the lowermost sheet or the stack toward the singling device. Singling gaps occasionally occur when, for example, the sheet material is especially large and the stack of sheets especially heavy (in which case the frictional force between stack and supporting plate is too great), or when the last sheet or sheets to be singled are not, or not completely, grasped by the feed rolls due to a sheet arch.

Singling errors often occur in the singling of stacks of sheets of different kinds and qualities, e.g. bank note stacks with used notes of very different denominations.

GB 2 035 268 A and JP 07 309466 A moreover disclose friction wheel singlers using friction material with approximately the same coefficient of friction for both singling cylinder and retaining cylinder. However, in these friction wheel singlers both singling cylinder and retaining cylinder must be driven. Moreover, the known friction wheel singlers do not permit synchronous singling.

SUMMARY

The problem of the present invention is thus to provide a friction wheel singler for singling sheet material, in particular mixed-format bank notes in poor condition, that has a low risk of singling errors, singles reliably after a long operating time and under very different ambient conditions, and singles sheet material at defined intervals.

According to the first aspect of the invention, the friction elements of the singling cylinder and the friction areas of the retaining device have the same friction material or friction material with the same coefficient of friction. This means that they have the same wear resistance, environmental resistance, moisture absorption, temperature expansion coefficient, aging and the like, so that the ratio of friction of the friction materials remains unaffected by such parameters and the service life of the friction wheel singler increases while the singling quality is constant.

To ensure that the singling cylinder force acting on the sheet material to be singled is sufficiently far above the force exerted by the retaining device despite the use of substantially the same friction material, it is in addition provided that the contact area—whether areal or linear—between the sheet material and the friction elements of the singling cylinder is substantially greater than the contact area between the sheet material and the friction areas of the retaining device. The term “contact area” is to be understood in connection with the present invention to mean that an overlap of singling cylinder and retaining device causes a perpendicular singling force and a perpendicular equal force to be exerted by singling cylinder and retaining device on the sheet material to be singled, which leads to singling and retaining forces corresponding to the coefficients of friction of the friction material and the effective area of the friction material. Preferably, half of the area of the retaining device is formed by a material with a negligibly low coefficient of friction. The ratio of the particular active area with friction material is then about 2:1. This ratio simultaneously determines the ratio of frictional forces between singling cylinder and retaining device because of the substantially identical friction materials, regardless of the condition or age of the friction material.

The influence of any further contact areas between retaining device and/or singling cylinder, on the one hand, and the sheet material to be singled, on the other hand, is kept low because such further contact areas are equipped with a substantially lower coefficient of friction than the areas of the retaining device and singling cylinder with friction material. The surfaces of the retaining device and singling cylinder in such further contact areas preferably consist of smooth metal, smooth plastic or another smooth material so that the frictional influence of said further contact areas is negligibly small compared to the frictional forces exerted on the sheet material to be singled by the areas with friction material.

In connection with synchronous singling of sheet material, that is, singling of sheet material at defined intervals between consecutive singled sheets, the friction elements of the singling cylinder are formed as friction segments only over a limited circumference of the singling cylinder. Sheet material is thus singled only when the friction segments come in contact with sheet material in the singling gap. Only then is the frictional force applied by the singling cylinder to the bank note to be singled higher than the frictional force of the retaining device. When the singling cylinder contacts sheet material outside the friction segments only with its smooth surface, however, the frictional force transferred to the sheet material is lower than the frictional force of the retaining device so that the sheet material is retained. This specifically means that a friction segment of the singling cylinder with a predetermined contact area or line has disposed opposite at the singling gap a retaining element of the retaining device that has a friction area with the same coefficient of friction as the friction segment of the singling cylinder, on the one hand, and a sliding area, for example of smooth metal, on the other hand, the contact areas or lines of the friction and sliding areas of the retaining device each corresponding to half the contact area or line of the friction segment of the singling cylinder. When the friction segment of the singling cylinder is located in the area of the singling gap, the ratio of friction contact areas between singling cylinder and retaining device is 2:1, so that sheet material is singled. After the friction segment has moved out of the area of the singling gap, the ratio between the friction contact areas of the singling cylinder and the retaining device is about 0:1, so that sheet material is retained.

The retaining element of the retaining device can preferably be formed by a freewheeling retaining roll or by retaining pads or a combination of retaining roll and retaining pad. A retaining pad, straight or in particular also curved, supports the guidance of the bank note around the singling cylinder but is subject to higher wear due to the sliding friction between note and block. The retaining roll held with freewheeling, on the other hand, permits higher service lives due to lower wear, since the freewheeling guarantees that the retaining roll is worn over its total circumference. It is therefore advantageous to combine retaining pads with sliding areas and retaining rolls with friction areas in the retaining device.

It is preferably provided that the support plane on which the stack of sheets rests in the sheet magazine is formed by a plurality of feed rolls disposed one after the other in the transport direction of the sheet material and disposed on driven shafts. The feed rolls are preferably distributed on the shafts over the total width of the support plane, and the shafts with the feed rolls over the total length of the support plane. The stack of sheets thus rests only on rolls, so that rolling frictional forces substantially occur in the support plane, which are lower compared to sliding frictional forces. The feed rolls disposed one after the other in the transport direction over the total length of the support plane with feed rolls over the total width of the support plane form a virtually all-over, effective feed for the supported stack of sheets up to the last sheet to be singled.

A preferred embodiment provides that the feed rolls are equipped over a limited circumference with friction segments having a high coefficient of friction relative to the remaining feed roll surface, the friction segments of all feed rolls on their associated shafts assuming the same angular position with respect to the support plane. If thus disposed feed rolls are synchronized with a singling cylinder likewise equipped with friction segments, especially reliable singling can be achieved if the friction segments of the singling cylinder take effect, that is, single sheet material, at the singling gap at the moment when the friction segments of the feed rolls are dipping into the support plane and thus not exerting any appreciable propulsion on the sheet to be singled.

A further preferred embodiment provides that the back feed rolls in the transport direction are equipped with a lower coefficient of friction than the feed rolls disposed therebefore in the transport direction, which prevents higher forces from occurring on the trailing edges of the sheet material to be singled than on the leading edges.

DESCRIPTION OF VARIOUS EMBODIMENTS

FIG. 1ashows a friction wheel singler in cross section, andFIG. 1bthe same friction wheel singler in a plan view. Bank note stack1is placed in the friction wheel singler in cross format. Lowermost note1ato be singled next thus lies with its long side against singling cylinder2. The force with which bank note stack1deposited in sheet magazine5, formed here as a slanted guiding plate, acts on singling cylinder2is determined solely by gravity and therefore depends on the weight and thus substantially the height of bank note stack1.

Singling cylinder2can be equipped with a friction lining over its complete circumference if continuous singling of notes with no interval between individual notes is desired. However, notes should usually be singled at a certain interval apart. For this purpose the circumferential surface of singling cylinder2has provided therein friction segment4having a high coefficient of friction compared to the remaining circumferential surface of cylinder2. Said remaining circumferential surface of cylinder2consists of smooth material, preferably smooth metal or smooth plastic.

Press-down rolls6ensure that sheet1ato be singled is supplied to singling gap7formed by singling cylinder2with retaining device3formed as a retaining roll. Retaining roll3is formed as a freewheeling roll, the direction of freewheeling allowing rotation of retaining roll3contrary to the direction of singling of sheet material to be singled. Freewheeling is always triggered for example by machine vibrations when no stack of sheets is placed on. Retaining roll3, due to suitable geometrical division of its surface into friction areas3aand smooth sliding areas3b,exerts only half as much frictional force on note1ato be singled as friction segment4of singling cylinder2, whereby the friction materials of friction segment4of singling cylinder2, on the one hand, and friction areas3aof retaining roll3, on the other hand, have a coefficient of friction that is substantially equal. The same friction materials are preferably used. This will be explained in more detail below with reference toFIGS. 3a,3b.Note1asingled through singling gap7is supplied with the aid of downstream transport rolls8to a processing device not shown, which determines the quality or value of the note for example.

InFIG. 1bit can be seen that singling cylinder2and retaining rolls3have circumferential grooves. The circumferential grooves of retaining rolls3are offset from the circumferential grooves of singling cylinder2and adapted in their width so that retaining roll3, which is designed to be displaceable, can dip into the grooves of singling cylinder2to increase the frictional forces. Friction segments4of singling cylinder2are marked by hatching, as are friction areas3aof retaining roll3. Sliding areas3bof retaining roll3and smooth sliding surfaces2bof singling cylinder2have no hatching, in contrast.

With reference toFIGS. 3a,3bthe principle of singling and retaining sheet material will now be described.FIG. 3ashows singling cylinder2and retaining roll3in cross section from the front (left picture) and in cross section from the side (middle picture) as well as a detail (right picture) of the left picture.

Singling cylinder2is in an effective position with friction segment4inFIG. 3a.That is, friction segment4forms together with retaining roll3singling gap7through which note1ato be singled is guided (middle picture). Friction linings10or friction areas2a,2bof friction segment4, on the one hand, and retaining roll3, on the other hand, preferably consist of the same friction material but have at least substantially the same coefficient of friction. Reference no.9designates the smooth surfaces or sliding areas2b,3bof singling cylinder2, on the one hand, and retaining rolls3, on the other hand (left picture).

The detail shown in the right picture ofFIG. 3aillustrates the effective ratio of the retaining force produced by retaining roll3to the singling force applied by friction segment4of singling cylinder2. On retaining rolls3two edges of associated friction area3aare effective on note1ato be singled, and on friction segment4four edges of friction area2aare effective on note1ato be singled. The edges of sliding areas3bof retaining roll3exert a negligibly low retaining force on sheet1ato be singled in comparison to friction areas3a,resulting altogether in a ratio of retaining force to singling force of 1:2. A different geometrical division of friction lining surfaces2a,3ato smooth surfaces2b,3bcan of course be used to achieve different ratios. In any case the singling force clearly outweighs the retaining force when friction segment4is effective on singling gap7, so that sheet1ato be singled is conveyed through gap7.

It can be derived fromFIG. 3bin corresponding fashion which ratio of retaining force to singling force arises when friction segment4of singling cylinder2has been moved out of the effective position, that is, out of singling gap7, with an otherwise identical geometrical design of the friction wheel singler. As can be seen from the right picture ofFIG. 3b,two edges of friction areas3aand two edges of negligible sliding areas3bof retaining roll3still act on sheet1ato be singled. Simultaneously, only four edges of negligible sliding areas2bof singling cylinder2act on the opposite side of sheet1ato be singled, resulting in a ratio of friction between retaining roll3and singling cylinder2of 1:0. A sheet lying against singling gap7is thus not singled but retained until friction segment4of singling cylinder2takes effect at gap7again.

Retaining roll3need not necessarily be formed as freewheeling. Its friction linings3aand smooth areas3bcan also be designed singly or both as fixed elements. Singling cylinder2also need not necessarily be segmented but can also be unsegmented, i.e. have no friction segments4, for the abovementioned case of asynchronous singling. Moreover, retaining roll3and singling cylinder2can be formed of individual disks or rings that are individually placed on shafts and fixed thereon at desired positions. The individual rings or disks are advantageously selected so that the above-described grooves result when the rings or disks are disposed on the shafts.

FIG. 4shows an enlarged detail of the friction wheel singler shown inFIG. 1a.However, in the embodiment shown inFIG. 4retaining element3is not realized as a retaining roll but as retaining pad20. Retaining pad20has a curvature adapted to the surface of singling cylinder2, but can also be of rectilinear design on the side facing cylinder2. Retaining pad20also has grooves to permit cooperation with singling cylinder2in the above-explained fashion. Retaining pad20shown inFIG. 4has friction areas and sliding areas therebehind, which are not visible in the selected sectional view because of the identical geometry. The friction areas are divided up geometrically in relation to the contact area of friction segment4of singling cylinder2so that a sufficiently great ratio of singling force to retaining force arises when friction segment4is completely effective.

The wear of retaining pad20on its friction areas is comparatively high, however, due to the sliding friction with the sheet material to be singled. An embodiment is therefore preferred in which retaining rolls and retaining pads are combined, friction areas3abeing formed on the retaining rolls and retaining pads20having sliding areas3b.Retaining pads20then consist of smooth material, e.g. smooth metal or smooth plastic.

InFIG. 1ait can in addition be seen that bank note stack1rests with lowermost note1ato be singled on feed rolls11,12. As to be seen inFIG. 1b,a plurality of feed rolls11and a plurality of feed rolls12are distributed on shafts15mounted one behind the other in the transport direction of note1ato be singled over the total width of said shafts15, resulting in an all-over effective feed over the total support width and support length of the sheet magazine. Shafts15are driven in order to feed sheet1ato be singled up to singling gap7, unlike what is shown inFIG. 1a.

Uniform support of bank note stack1with as many support points as possible in the support plane is obtained by feed rolls11being offset from feed rolls12so that they closely adjoin shaft15of the closest feed rolls (FIG. 1b).

Feed rolls11,12consist of smooth material, e.g. smooth metal or smooth plastic, and have friction segments11a,12a.Friction segments12aattacking the trailing edge (in the transport direction) of note1ato be singled advantageously have a lower coefficient of friction than friction segments11aof front feed rolls11. This prevents a greater feed force from being exerted on the trailing edge of the note than on the leading area of the note, since uniform conveyance of note1ato be singled can otherwise be problematic.

Friction segments11a,12aare all disposed on their associated shaft15at same angle α relative to the support plane of bank note stack1(FIG. 1a). Since shafts15are driven in synchronism, friction segments11a,12asimultaneously come in contact with note1ato be singled to be supplied to singling gap7and also simultaneously dip down into the support plane again. The dip-down moment is shown inFIG. 1a.At this moment the feed function of feed rolls11a,12ais substantially over since the feed effect of feed rolls11,12is now low outside friction segments11a,12a.At the latest when friction segments11a,12adip down into the support plane, stack of sheets1and in particular next note1ato be singled should lie against singling gap7. But singling of note1ais effected only when friction segment4of singling cylinder2takes effect, that is, when friction segment4reaches singling gap7, as described above. It is therefore provided that friction segment4of singling cylinder2enters singling gap7and takes effect exactly at the moment when friction segments11a,12aof feed rolls11,12dip down into the support plane, as shown inFIG. 1a.

The frictional forces of friction segments11a,12aare in total below the frictional forces of retaining device3, since singling would otherwise be effected solely due to the feed force applied by feed rolls11,12on the sheet to be singled. The coefficient of friction of friction segments11a,12ais to be correlated accordingly with the coefficient of friction of friction areas3aof retaining device3, assuming a maximum stack of 500 sheets.

FIGS. 2aand2bshow a friction wheel singler comparable to the friction wheel singler according toFIGS. 1a,1b,but for singling bank note stack1in long format rather than cross format. Four instead of two shafts15are accordingly provided with feed rolls11,12,13,14distributed over the shaft length, the width of shafts15being selected in accordance with the maximum width of the notes to be singled and the number and distance of shafts15in accordance with the maximum length of notes to be singled. Feed rolls11to14again consist of smooth material, e.g. smooth metal or smooth plastic, and have friction segments11ato14a,whereby friction segments12ato14aof feed rolls12to14attacking the trailing end (in the transport direction) of note1ato be singled have a friction material with a lower coefficient of friction than friction segments11aof feed rolls11located on the front shaft (in the transport direction).

Additionally or alternatively to the choice of different friction materials for the friction segments of back feed rolls12to14, on the one hand, and front feed rolls11, on the other hand, it can be provided that friction segments11aprotrude slightly out of the circumferential plane of feed rolls11and thus also of the support plane, so that the bank note stack is slightly lifted. Friction segments11athus act as a hopper and transfer more feed force to note1ato be singled than friction segments12ato14aof downstream feed rolls12to14, the friction material otherwise being identical. Friction segments12ato14a,on the other hand, are flush with the circumferential surface of feed rolls12to14. Friction segments11aof front feed rolls11can be profiled to increase the frictional adhesion, just like friction segments4of singling cylinder2. Such a hopper can of course also be realized for the above-described embodiment according toFIGS. 1a, bfor singling in the transverse direction.

Synchronization of feed rolls11,12or11to14with feed roll2is facilitated by the circumference of feed rolls11to14and of singling cylinder2being identical. Feed rolls11,12or11to14feed the note to the singling gap preferably at their surface speed, which corresponds to the transport speed of the note after singling has been effected. Deviating from this, it is also possible to use feed rolls11,12or11to14synchronized with singling cylinder2or with friction segment4that have a smaller diameter and thus a lower surface speed. In such a solution, lowermost note1ain bank note stack1slides slightly over feed rolls11,12or11to14after being grasped in singling gap7because of the lower surface speed of feed rolls11,12or11to14. However, since feed rolls11,12or11to14consist of smooth material in these areas, as described above, the frictional forces that take effect are very low and can be neglected.