This invention relates to a tab inserter - that is to say, apparatus arranged to insert a tab between two sheets of a stack of flexible sheets, part-way along the stack, which tab is to serve as a marker. Tab inserters are frequently used in association with counting apparatus arranged to count the number of sheets in a stack thereof. For example, in the counting of sheets of paper, it may be desirable to insert a tab each time a defined number of sheets have been counted in the stack, to permit the subsequent easy separation of the stack of sheets into smaller stacks each containing a known quantity of sheets. This is especially important in the case of printed sheets which are produced in a security environment - for example, in the case of bank note printing or the printing of other vouchers having a face value.

A known form of tab inserter comprises means defining a feed path for tabbing tape, drive means for feeding predetermined lengths of tabbing tape and a cutter for severing a fed length of tape so as to form a tab for insertion, or which was inserted during the feeding step, between two sheets of a stack thereof. Such a tab inserter will hereinafter be referred to as a "tab inserter of the kind described". Known designs of counters for sheets of paper or paper-like materials are able to operate with a count rate of a few thousand sheets per minute. If such a counter is to be used in conjunction with a tab inserter of the kind described, it is most desirable to avoid interruption of the counting, so as to permit high average count rates still to be achieved. The speed of operation of the tab inserter must therefore be sufficient to enable the insertion of a tab without suspending the counting. Attempts have been made to

increase the speed of operation of the known forms of tab inserter, but problems have arisen with these, resulting in an incorrect length of tape being fed, or of the tape moving out of the optimum position for feeding by the drive means. In addition, and typically after there has been a mis-feed, there is a risk that the tape may jam within the tab inserter, resulting in the need partially to disassemble the tab inserter in order to clear the tape jam - and the counting operation must be suspended throughout the relatively long time it takes to clear the jam and re-feed the tape through the tab inserter.

The present invention aims at addressing some of the problems associated with operating known forms of tab inserters of the kind described at relatively high speeds, to avoid the necessity to suspend counting while permitting the insertion of a tab at a required place in a stack of sheets being counted. Preferred aspects of the invention also aim at minimising the down-time for re-feeding tabbing tape through the tab inserter, for example after a roll of tabbing tape has been consumed or after clearing a tape jam.

According to one aspect of the present invention, in a tab inserter of the kind described, the drive means comprises a drive wheel to one side of the feed path and a rocker arm pivotally mounted over the path on the other side thereof to the drive wheel, the arm carrying to one side of its pivotal mounting a pinch wheel engageable with the drive wheel and to the other side of its pivotal mounting a tape brake member whereby pivoting of the arm causes either the brake member to engage the tape or the pinch wheel to form in conjunction with the drive wheel a nip for feeding the tape. It will be appreciated that with the arrangement described above, when the rocker arm is in one limiting

position the tape is being driven by the tape drive means, and when the arm is in its other limiting position, the tape is being held against movement by the brake member. Thus, except during the transition of the arm between its two limiting positions, the tape is always controlled by the tab inserter, so minimising the likelihood of a mis-feed or of an incorrect length of tape being fed. By appropriate configuration of the shape of the rocker arm, the angular movement thereof between its said two limiting positions may be made relatively small, so minimising the time during which the tape is not positively controlled.

The rocker arm may be resiliently biased to one of its limiting positions, and preferably to the position where the brake member engages the tape. The movement of the rocker arm to its other limiting position may conveniently be effected by an electromagnetic solenoid, acting against the resilient bias. The tape will then be held stationary at all times other than when a tab is to be fed, even when power has been removed from the inserter.

The brake member may comprise a friction material engageable with the tape, or preferably comprises a projection provided on the rocker arm, which projection is pointed at its tape-engaging end. In either case, the path defining means should provide a suitable anvil on the other side of the tape to the brake member, against which that brake member may operate.

According to a second aspect of the present invention, there is provided a tab inserter of the kind described, wherein the drive means comprises a drive wheel to one side of the feed path and an opposed pinch wheel on the other side of the path thereby defining a nip between which the tape passes, the feed path means comprising a main body having guide means to constrain the tape to follow said path and the main body also

carrying one of said wheels, the other of said wheels being mounted on a sub-frame pivoted to the body for pivoting movement between a first position where a part of the sub-frame overlies the guide means of the main body and the other of said wheels is juxtaposed to said one of the wheels, and a second position where the guide means is exposed and the two wheels are relatively separated.

By providing a tab inserter having a main body and a sub-frame which are relatively separable in the manner described above, the feeding of tape through the tab inserter is much simplified, as is the clearing of a tape jam which not infrequently may occur with the known designs of tab inserters. The feeding operation merely requires the two parts to be separated, so giving immediate access to the guide means for the tape, feeding the tape along that guide means and through the cutter and then closing the two parts, whereafter the tab inserter is ready for use once more. The guide means may define an elongate path with said one of the wheels being disposed at the forward end of the path, having regard to the normal feed direction of the tape, the sub-frame being pivoted to the main body at a position adjacent but forward of the two wheels. In this way, access may readily be gained to the guide means and moreover the relative separation of the wheels may be maximised to facilitate the tape feeding therebetween. The guide means may comprise a channel formed in a surface of the main body. Preferably, an over-centre mechanism interconnects the main body and the sub-frame, at a position upstream of the two wheels, having regard to the normal feed direction of the tape. Such an over-centre mechanism may comprise an operating lever pivoted to one of the main body and the sub-frame, and spring means linking

the operating lever to the other of the main body and the sub-frame.

According to yet another aspect of the present invention, there is provided a tab inserter of the kind described wherein the cutter comprises a fixed bar of circular cross-section with a slot extending thereacross and through which slot fed tape passes, and a cutting member of at least part-circular form and mounted on the bar for rotation about the axis thereof, the cutting member having a cutting edge for cooperation with an edge of the slot in the bar upon rotation of the member.

Most preferably, the slot edge with which the cutting member cooperates is formed at the forward end of the slot, having regard to the normal direction of tape feed. Smooth operation of the cutter may be obtained by providing at least one of the slot edge and the cooperating cutting member edge to extend in a non- parallel manner to the axis of the bar - that is, the edge may extend helically. In this way, the tape cutting action will be progressive upon rotation of the cutting member about the bar.

The cutter of this invention as described above serves to sever tape by the cooperation of an edge of the cutting member with an edge of the slot in the bar; the trailing edge of a cut tab will therefore be pushed by the cutting member away from the slot in the bar. There is a tendency for an inserted tab to move slightly, immediately following its insertion between two sheets in a stack thereof, and any such movement will cause the trailing edge of the tab to be retained by the bar away from the cutting edge thereof, even following return of the cutting member back to its original position. In turn, this assists in preventing possible interference between the trailing edge of a cut tab and the forward edge of the next tab to be fed,

so minimising the likelihood of mis-feeds and tape jams.

A tab inserter of this invention may of course include any of the features of the various aspects of this invention as described above - and the specific embodiment of tab inserter described hereinafter includes all of the preferred features of those various aspects of this invention.

By way of example only, one specific embodiment of tab inserter constructed and arranged in accordance with the present invention and intended for use in conjunction with a paper counter (not shown) will now be described in detail, reference being made to the accompanying drawings, in which:- Figure 1 is a diagrammatic side view of the embodiment of tab inserter, in a closed position but with a side plate removed for clarity; and

Figure 2 is a diagrammatic side view of the tab inserter of Figure 1, but in an open position and with the side plate in position.

The embodiment of tab inserter comprises a main body 10 which defines a tape feed path 11 for a paper tabbing tape 12, fed from a roll thereof (not shown) in the direction of arrow A along that path 11. The tape feed path 11 is defined by a channel-shaped groove formed in the upper surface of the main body 10, the channel being slightly wider than the width of the tape whereby the tape may slide freely therealong.

Pivoted to the main body 10 about shaft 13 is a top housing 14 which is moveable between a closed position, illustrated in Figure 1, and an open position, illustrated in Figure 2. An over-centre mechanism including a triangular lever 15 having a finger-grip 16 is pivoted at 17 to the top housing 14, a helical tension spring 18 linking the lever 15 to a lug 19 formed as a part of the main body 10. The

geometry is such that when the top housing is in its closed position, the lever 15 bears on a stop 20 formed as a part of the top housing and is maintained in that position by tension in the spring 18, but on moving the lever 15 in the direction of arrow B, the spring 18 moves across the pivot 17 and then acts in compression to cause the top housing to pivot to the open position illustrated in Figure 2.

A drive roller 24 is rotatably mounted on the main body 10 at the forward end of the tape feed path 11, such that tape fed along that path is tangential to the periphery of the drive roller 24. An electric motor

(not shown) is arranged continuously to drive the roller 24. A rocker arm 25 is pivoted to the top housing 14, such that the arm extends along, but above, the tape feed path 11. The rocker arm 25 supports a freely rotatable pinch roller 26, immediately opposed to the drive roller 24 but on the opposite side of the tape feed path 11, whereby the drive roller 24 and pinch roller 26 define a drive nip for tape 12. Towards the opposite end of the rocker arm 25, there is provided a brake stud 27, pointed at its free end and arranged to be engageable with tape located in the tape feed path 11. An armature 28 of a solenoid 29 is connected to the rocker arm 25 adjacent the stud 27, a compression spring 30 urging that end of the rocker arm away from the solenoid. The arrangement i such that the spring

30 urges the brake stud 27 to engage tape in the tape feed path 11, in which position the pinch roller 26 is clear of the drive roller 24; but on actuation of the solenoid 29, the rocker arm is pivoted so lifting the stud 27 clear of the tape and engaging the pinch roller

26 with the drive roller 24, so driving tape. At the forward end of the main body 10, there is supported a cutter 34 comprising a fixed round bar 35

having a generally transverse slot 36 of tapering height in the direction of advancement of tape 12, and a rotary cutter sleeve 37 mounted on the bar 35 and defining a cutting edge 38 cooperable with the lower edge 39 of the slot 36 at the forward end of that slot. When tape has been fed through the cutter 34, rotary movement of the sleeve 37 in the direction of arrow C serves to sever advanced tape from that tape remaining within the tab inserter, so defining a tab for use in marking counted sheets.

In use, the tab inserter described above is appropriately connected to a paper counter, adjacent the counting head. The lever 15 is operated to open the top housing and then tape may easily be fed through the inserter and the slot 36 in the cutter 34, whereafter the lever 15 is operated to close the top housing. Thereafter, when it is desired to insert a tab at a particular position in a stack of sheets, during the counting thereof, a drive pulse is provided to the solenoid 29. This releases the stud 27 from the tape within the tab inserter and causes a length of tape to be advanced through the cutter 34, by the action of drive roller 24 together with pinch roller 26. The length of tape advanced may be controlled by varying the duration of the pulse supplied to the actuator 29. On de-energising the solenoid 29, spring 30 returns the rocker arm 25 to its original position, so allowing stud 27 to brake and hold stationary the tape. At this time, the sleeve 37 of the cutter 34 is moved in the direction of arrow C, so as to sever the projected length of tape advanced through the cutter. The edge 38 of the cutter moves the trailing edge of the severed tab below the lower arcuate surface of the bar 35, and that edge tends to remain there following return of the sleeve 37 to its initial position, so minimising the likelihood of interference between the

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leading edge of the next tab to be generated and the trailing edge of the last tab, just severed from the tape.

In a preferred form of counter, the leading edge of a tab is directly inserted into a gap between two sheets, as the tape is advanced by the inserter. The tab is immediately severed by the cutter 34, and the counting operation continues uninterrupted, with the tab inserter ready to insert the next tab, where required.