IL30755A - Method and apparatus for severing a continuous web to form a plurality of discrete portions - Google Patents

Description

METHOD AND APPARATUS FOR SEVERING A CONTINUOUS WEB TO FORM A PLURALITY OF DISCRETE PORTIONS THIS INVENTION relates to a method of and apparatus for severing a continuous web to form discrete articles and especially relates to a method and apparatus in which the severed articles are delivered in a continuous stream* More particularly the invention relates to the pro-duction of separate sachets by severing from a continuous web* In the production of sachets it is desirable to convert a continuous web of material into a stream of discrete sachets which have been severed individually from the incoming web* According to one aspect of the present invention I provide a method of severing a continuous web to form a plurality of discrete portionsI such method comprising feeding one end of the web to one pocket of a rotatable star wheel as herein defined, and having a fixed knife blade associated with each pocket, moving a co-operating knife blade past said fixed blade to effect severance of an end portion of the web from the remainder of the web, such portion being disposed within said one pocket of the star wheel, carrying the severed end portion round the axis of the star wheel to a delivery station and moving the severed portion radially outwardly and circumferentially rearwardly with respect to the star wheel prior to arrival at the delivery station* The term "star-wheel" used throughout this specification is intended to denote a wheel having an undulated periphery defined by peaks and troughs, the peaks corresponding to the points of a star and the troughs forming pockets within which articles may be placed* Preferably but not essentially the peripheral contour may be so modified as to retain ah article in place in a pocket, for example by inclining the points of the star rearwardly with respect to the intended direction of rotation of the star-wheel* Advantageously the co-operating knife blade may be moved radially inwardly of the star wheel past the fixed knife blade to effect severance* severance of the web occurs while the etar wheel is continuously rotating* Advantageously the severed portion of the web may be moved circumferentially rearwardly of the star wheel causing radially outward movement, thereby effecting retardation of the severed portion before it is deposited on a stationary delivery chute.

According to a further aspect of the present invention I provide apparatus or severing a continuous web to form a plurality of discrete portions * such apparatus comprising a star wheel as hereinbefore defined, means for feeding one end of the web to a pocket of the star wheel, a delivery station for receiving the severed portions after discharge from the star wheel, a plurality of knife blades fixed to the star wheel each associated with a pocket of the wheel, at least one movable knife blade co-operable with a fixed blado to sever from the web a portion in said poket, and means for moving the severed portions radially outwardly and circumferentially rearwardly of the star wheel during travel towards said delivery station* Desirably a plurality of movable knife blades may be provided* each movable blade being co-operable with a different one of the fixed blades* Preferably the movable knife blades may be mounted on a severing element which moves along an arcuate path substantially coincident with a part of the periphery of the star wheel* Advantageously the severing element may comprise a continuous chain having movable knife blades pivot- ally attached to link pins of the chain, each movable knife blade being provided with a cam follower for co-operation with a cam track to effect pivotal motion between cutting and withdrawn positions* Conveniently each movable knife blade may be attached to an arm which is pivotally mounted on a link pin of the chain, said arm being resiliently biased towards the withdrawn position* Alternatively the cam follower may be a wheel riding in a groove or slot in a cam member, the movement of the cam follower to planar and have a cutting edge, each said blade being mounted on an arm formed of sheet material bent into an L shape, the knife blade being mounted on one limb of the L and the end of the other limb being pivotally connected to the severing element, the arrangement being such that the end edge of the first mentioned limb is disposed parallel to the axis of the star wheel and projects further radially inwardly of the star wheel than does the cutting edge of the blade* Suitably the cutting edge of each movable blade may be inclined with respect to the axis of the star wheel, and the fixed knife blades may each have cutting edges parallel to the axis of the star wheel* In one particularly convenient embodiment of this aspect of the invention each movable knife blade may have an alignment tooth at one end of the cutting edge so that said alignment tooth engages the fixed knife blade and ensures the two co-operating blades are aligned, the arm being made of a resilient material to accomodate any aligning adjustment induced by the alignment tooth. Preferably registering bars may be connected to other link pins of the chain and may be arranged to co-operate with the fixed knife blades so that the web is firmly held between the fixed knife blade and an associated registering bar while an associated movable knife blade effects severance of the web.

In an alternative form of this aspect of the invention the star wheel may be provided with article delivery members which effect radially outward displacement of the severed portions during travel of the portions round the axis of the star wheel towards a delivery station* Preferably the article delivery members may also effect retardation of the articles with respect to their linear velocity imparted by virtue of rotation of the star wheel* Desirably the article delivery members may be in form of V-shaped wing members which move along an arcuate path between an angularly position and entrain the articles in so doing, thereby lifting the articles clear of the star wheel pockets. Preferably the wing members may be pivotally connected to the star wheel and be provided with cam followers which are deflected radially outwardly during passage along a fixed cam surface, the cam follower of each wing member, considered with respect to the direction of rotation of the star wheel, being angularly advanced with respect to the point of pivotal connection of the same wing member* Advantageously the wing members may be resiliently biased towards their radially inner positions to hold the cam followers in contact with the fixed cam surfaces* Conveniently a delivery chute may be arranged to extend substantially radially of the star wheel and may be provided with at least one extractor tooth for removing articles from the pockets of the star wheel* If desired, means may be provided for introducing spacer elements to selected pockets of the star wheel* In order that the present invention may more readily be understood one embodiment of article handling apparatus will now be described, merely by way of example, reference being made to the accompanying drawings in which:- Figure 1 is a transverse sectional view, taken along the line 1-1 of Figure 2, of an article handling apparatus of this inventionf Figure 2 is a sectional view taken on the line 2-2 of Figure 1, Figure 3 shows a detailed view of a modified form of tea-bag severing machine according to the invention; and Figure 4 shows a sectional view of a movable knife blade and is taken on the line IV-IV of Figure 3.

Referring now to the drawings, a web 1 comprises a plurality of full tea bags 2 which have been formed by placing two continuous webs *► edges and at selected transversely extending lines on the webs, the space between adjacent transversely extending lines having previously been partly filled with tea chopped, dried tea leaves* The web 1 is fed into the space between a star-wheel 3 and a continuous chain element 4 and is synchronised with the pockets of the star-wheel so that the welded lines defining the borders between successive tea bags are in register with the "points"of the star-wheel. This synchronisation is described in detail below* The star wheel includes a plurality of pockets 5, corresponding to the depressions between the points of the star-wheel and points 6 at which fixed knife blades are positioned, each knife blade 7 having an alignment tooth 8 (see Figure 2) at one end thereof. The star-wheel 3 is formed of two spaced circular discs 9 and 10 freely rotatably mounted on a common shaft 11. The periphery of each disc 9 and 10 includes a plurality of sprocket teeth 12 appropriately spaced for driving engagement with the chain element 4.

The chain element 4 comprises a pair of identical transmission chains 13 and 14, each engaging with one of the toothed wheels 9 and 10. Registering bars 15, positioned at every fifth link along the chains, are fixed to the link pins of the chains so as to form a ladder construction having the chains 13 and 14 as the supporting elements and the registering bars 15 as rungs, the ends of the registering bars 15 being joined to the chain link pins. Displaced by a spacing of two chain links to one side of each registering bar 15 is a pintle 16 which again is joined by its ends to the appropriate link pins of the chain. The pintles 16 which are always constrained to be parallel with the registering bars 15 support freely rotatable sleeves 17 having integrally formed hooked arms 18 at the free end of each of which is secured a knife blade 19· The knife blade is arran ed so that u on rotation of the sleeve 17 about intle 16 the knife Suitable biasing springs will be incorporated in the apparatus but are not illustrated in the accompanying drawings. For example, a helical torsion spring may be associated with each pintle l6 and the surrounding sleeve 17 so as to bias the arm 18 and blade 19 in an anticlockwise direction as viewed in Figure 1· This anticlockwise motion corresponding to movement towards an inoperative position of the knife blades* Integrally formed with each hooked ana 18 is a cam follower which slides on a generally arcuate fixed cam surface 21· In addition to being engaged by the teeth 12 of the discs 9 and 10t the chains 13 and ( not shown) / 14 also ride over idler wheels 22, 23 and 24, 25 respectively so as to provide for more positive location of the chains* The idler wheels 22 and 23 are mounted on a supporting shaft 26 and the idler wheels 23 and 25 are mounted on a similar parallel supporting shaft 27* The supporting shafts 26 and 27 also serve to support the fixed cam surface 21 as shown in Figure 1* As shown in Figure 2 the knife blades 19 each have an angled cutting edge 28 so that upon movement of a knife blade 19 past an associated knife blade 7 a "scissor action" is obtained. Such movement of the knife blades 19 is obtained by co-operaticn of the associated cam followers 20 with the cam surface 21* As the associated cam follower 20 of each knife blade 19 rounds that end of the fixed surface 21 surrounding supporting shaft 26, the hooked arm 18 is allowed to pivot in a clockwise sense about pintle 16 so as to move the knife blade 19 to its withdrawn position. As the cam follower 20 commences to track along the concave cam surface 21* the cam follower 20 is progressively urged outwardly in a direction pivoting the hooked arm 18 anticlockwise about pintle 16 and moving the knife blade 19 into cutting engagement with the fixed knife 7* The alignment between fixed knife blades 7 and movable knife blade 7 engaging behind the registering bar 15 nearest the path of movement of this associated knife blade 19· Thus the chain elements 13 and 14 are maintained in correct synchronisation with the star wheel 3 by means of the engagement of the teeth 12 with the chain and also by means of the alignment teeth 8 abutting the registering bars 15· As the cam follower approaches that end of cam surface 21 * nearest supporting shaft 27 the action of the biasing spring serves once again to rotate the hooked arm 16 in a clockwise sense so as to withdraw the movable knife blade 19 to its inoperative position, before tracking round the back of the fixed cam surface 21· Instead of the spring-biased return movement incorporated in the device of Figures 1 and 2, it may be preferable to arrange the camming movable knife blade actuating device so that it is in the form of a slot which locates a cam follower wheel attached to the knife blade* Such an arrangement is illustrated in Figure 3 in which a cam plate 50 is provided with a track or slot having inner and outer walls 5 and 2 respectively ,ΙΧ.68 and defining a passage along which successive cam follower wheels 53 may pass* Each of the cam follower wheels 53 is rotatably mounted on a spindle 5 passing transversely through a cam follower arm 55 secured to the back of the arm 18 and thereby effects pivotal movement of the arm during movement of the chain about the idler wheels 22 and 23. Clearly, this arrangement of cam and follower where the follower is a wheel constrained by two opposed walls 51 and 52 of a slot will effect automatic return of the arm 18 to its inoperative position as the chain progresses further round its arcuate path, with the result that no spring-biasing device will be necessary and the construction of the pivotal mounting of the arms 18 on the pins 16 will therefore be simplified* The embodiment of Figure 3 also includes a modification of the combination of the alignment tooth and registering bar in that the registering ao that the registering bar 6 contacts the leading edge of the fixed knife blade 7 (considered with reference to the direction of rotation of the star wheel). This advance is effected by angular reorientation of the sprocket 12 with respect to the star wheel 3 so that the chain, along the arcuate area of contact between the chain and star wheel, now adopts a slightly advanced position with respect to the star wheel. Such realignment will necessitate slight lengthening of the various arms 18 so that the knife blades 19 still co-operate closely with the fixed blade 7.

In this case the alignment tooth 57 is formed at one lateral extremity of the movable knife blade 19 and, upon pivotal movement of the arm 18 to effect the cutting operation, the registering tooth 57 contacts the corresponding lateral extremity of the fixed knife blade 7 and aligns the fixed and pivot ble knife blades 7 and 19 to effect the desired "scissor" cutting action.

Thus the registering mechanism has now been reversed in the sense that the alignment tooth on the movable knife blade co-operates with the fixed knife blade whereas previously an alignment tooth on the fixed knife blade co-operated with the registering bars of the chain severing element.

As can be seen clearly in Figure 1, each registering bar 1 * upon orbitting the fixed supporting shaft 26, moves into engagement with the fixed knife blade 7 so as to pinch the weld line between successive tea bags adjacent the lower end of a bag 2 in one of the pockets 5· The upper end of the pinched bag is being severed by the movable knife blade 19 while the above mentioned pinching action is taking place. In fact the engagement between the registering bar and the associated fixed knife blade 7 is such that the thin material at the weld line is able freely to slide between the nip of the registering bar 15 and knife blade 7 but the increased Thus, as the upper end of a particular bag 2 is severed, the lower end of the bag which contains a wedge shaped body of tea is able to slide rear— wardly slightly, under the action of the weight of the web 1 of tea bags entering the apparatus until the bottom of the bag site just above the nip between the associated registering bar and the fixed knife blade 7« After further rotation of the star-wheel and chain assembly this bag will be severed from the web 1 which will then fall back until the bottom of the next succeeding bag 2 is supported by the associated registering bar and fixed knife blade 7» For this purpose spacing between the bottom edges of each two adjacent tea bag 2 is slightly less than the straight line distance between the cutting edges of successively fixed knife blades 7* The effect of the weight of the web 1 of tea bags may be increased by providing an unsupported loop of tea bags at the entry to the star- wheel so that the downward pull on a tea bag 2 entering the nip between the chain assembly 4 and star-wheel is effectively the catenary tension of the loop of the web 1· The modified embodiment of Figure 3> as explained above, has the registering bars 6 repositioned with respect to the registering bars 15 of Figure 1· In the Figure 1 embodiment it is possible for the severed edge of the bag 2c, which is still attached to the free loop 1 of the bags to be severed, to be lifted up out of the pocket of the star wheel during JX.68 retraction of the movable knife blade 19· In order to prevent such retraction of the bag with the possible consequence that the bag 2c may strike other parts of the machine and may be damaged or cause jamming, a slot 58 is provided at the leading edge of each pocket and is able to receive a severed edge after the knife blade has been retracted,, A further factor contributing to the more secure location of the bag 2c after severing is the extension of the limb 59 of the L~shaped arm 18 so that the pivotable blade 19 is completely concealed behind the limb 59, in other words the extreme end 60 of the limb 59 projects further radially inwardly (considered with respect to the radius of the star wheel 3) than does the cutting edge 28 of the knife blade 19· The operation of this modified embodiment of severing apparatus is as follows* During clockwise rotation of the. star wheel, the bag 2c of the web enters its associated pocket 5c in the wheel* The leading edge of the bag 2c is at this stage resting on the radially outer surface of the fixed knife blade 7 a is held in position by the abutting contact between the registering bar 6 and the knife blade 7· As rotation of the star wheel continues, the chain, entrained by the sprocket 12, moves in an anti-clockwise direction about its arcuate path and the inclination of the camming walls 1 and of the cam track results in a pivotal movement of the arm 18c to effect severing of the bag 2c from the adjacent preceding bag. Initially the registering tooth 57£ on the knife blade 19c will contact the associated fixed blade 7 a will align the two knife blades for the required scissor cutting action. Further rotation of the star wheel and chain will result in continued dow^ard movement of the movable blade 7 so that the bag 2c is severed from the preceding bag. At this stage the leading edge of the bag 2c will be pressed radially [inwardly of the star wheel 3 by the cutting edge 28 during severance, but will also be held down in this radially inward position by contact with the end 60c of the arm l8c.

Whereas previously the leading edge of the bag 2c would have been able to contact the inclined rear face of the cutting edge 28, the extension of the limb 59 of the arm l8c has resulted in complete shielding of the leading edge of the bag 2c from such inclined face. After severance of the leading edge of the bag 2c from the preceding bag, the extremity 60c of the limb 59£ vrill hold the bag in its radially inward position until the knife blade 19c commences its retraction as the cam follower 53 rides up over the retreating wall 5 of the slot.

However, at the instant when the knife blade 19c commences As shown in Figure 1, the contact between the chain assembly k and the star-wheel 3 extends over substantially a quarter of the periphery of the circular star-wheel 3· Throughout this contact length the pivotal movement of the hooked arm 18 carrying the movable knife blade 19 is un- hindered by any part of the star-wheel 3, and upon approaching the end of the contact length nearest the supporting shaft 27, the knife blade 19 has once again retracted to its inoperative position. A delivery chute 29 is positioned so as to extend horizontally radially outwardly of the star-wheel on the side at which the pockets are descending during rotation of the floor 29b which is provided with an extractor tooth 30 which extends radially inwardly of the star-wheel 3 but is just clear of the circular path of the movement of the fixed blades 7* Clearly in order for a tea bag situated in a descending pocket 5 to be withdrawn from the pocket it.must contact the extractor tooth 30, and hence must be displaced radially outwardly of the star-wheel in order to come within the zone of influence of the extractor tooth 30· Such radially outward movement is achieved by 4 means of a movable wing member associated with each of the pockets 5· Each wing member 31 includes an abutment face 32 and a retaining arm 33 formed integrally therewith* The abutment face 32 is disposed inwardly of the pocket 5 until the pocket 3 approaches the delivery chute 29· At this point the abutment face 2 moves radially outwardly and, in so doing, displaces the bag 2 radially outwardly from the pocket towards the position in which the extractor tooth 30 of the delivery chute 29 will arrest the bag 2· The bag retaining arm 33 is joined to the abutment face 32 at a crooked portion 3^· A freely pivotable am 35 is mounted at pivot pin 36 to the star-wheel assembly 3 and carries at its free end, the article displacement member 31· The arm 35 has a lug 35 ' within which the spindle of a wheel 37 is freely rotatably mounted and the wheel 37 rolls on a fixed eccentric cam surface 38 held adjacent the star-wheel assembly 3 by means of a bracket 39.

The operation of the wing members or article displacement members 31 is as follows* Upon clockwise rotation of the star-wheel assembly 3 the pivot pins 36 execute a circular orbit about the shaft 11* In so doing the pivotable arms 35 are carried round the shaft 11 during which movement the wheels 37 roll along the eccentric cam surface 38 which is so arranged that its surface is at a maximum displacement from the axis of shaft 11 at the part adjacent the article delivery chute 29* In rolling along the the contour of cam surf ce 38 causing anti-clockwise rotation of the arm with respect to the star-wheel assembly 3. Such anti-clockwise rotation causes the abutment face 32 to move radially outwardly and to move rearwardly, with respect to the direction of the rotation of the star-wheel, until it abuts the tea bag 2 carried in the associated pocket 5· Further anti-clockwise rotation of the arm 35 causes displacement of the tea bag out of the pocket and also causes the crooked portion 34 to approach the now lower edge of the tea bag 2. During this movement the bag 2 is prevented from falling out of the pockets since the article retaining element 33 moves to a position in which it lies radially outwardly from the tea bag 2· During the final stages of the movement of the tea bag 2 towards the delivery station the now lower edge of the bag 2 is lifted clear of the star-wheel 3 and is moved further radially outwardly until it lies outside the circular path of the fixed knife blades 7· At this stage the tea bag 2 is in a position in which it will be arrested by the presence of the extractor tooth 30 of the delivery chute 29· In order to prevent striking of the article displacement member 31 by the extractor tooth 30t the displacement member 31 has a central cut-out portion corresponding to the width of the extractor tooth 30. This leaves the abutment face 32 and article retaining element 33 as comprising thin strips which are spaced apart and form one unit by being secured to the same pivotable arm 35· As shown clearly in Figure 1} the article retaining element 33 serves not only to prevent accidental premature despatch of the tea bag 2, but also to advance the stack of tea bags in the delivery chute 29 outwardly to provide room for the next bag 2 being delivered; this is achieved by sliding of the outer convex face of the article retaining element 33 against the last previously delivered tea bag and, due to the resilience of the article retaining element 33j rightward movement (as viewed in Figure 1) of the 32 and article retaining elements 33 then pass downwardly on either side of the extractor tooth 30 after which time the displacement of the wheel 37 from the axis of shaft 11 decreases as the wing assembly 32, 33» 3¾, 35 t 36 and 37 moves clear of the lobe of the cam surface 38. The article displacement element 31 then moves inwardly to a retracted position in which it lies radially inwardly of the path of movement of the knife blades 7» and is also clear of the radial path traced by the moving knife blades 19· It will be appreciated that the illustrated arrangement of the tea bag depositing device comprising the article delivery members 3 pivoted at 36, not only effects radially outward movement of the tea bag lifting it clear of the pocket 5, but also effects retardation of the tea bag by causing anti-clockwise movement of the bag about the axis of shaft 11 and relative to the star wheel 3· This retardation, which is caused by virtue of the pivotal mounting of the delivery member 31 so that the associated cam follower wheel 37 is angularly advanced with respect to the pivoting mounting 36, has two advantages. The first advantage is that the angular speed of the bag about the axis of the shaft 11 is reduced so that the effect of impact of the soft leading edge of the bag on the extractor tooth 0 is reduced causing the peripheral speed of the tea bag at the instant of impact of the extracted tooth to be considerably less than that of the star wheel, thereby enabling high star wheel speeds to be obtained without sustaining damage to the bags being delivered. The second advantage of this retardation is that, when employing the arrangement illustrated in Figure 3, the bag 2 will be lifted clear of the slot 58 due to the relative anti-clockwise motion caused by the article delivery member 31 and thus there will be no chance of the leading edge of the bag being torn as the bag is moved radially outwardly of the star wheel 3· Naturally once the tea bag has been deposited and the cam resulting clockwise motion, caused by virtue of the tension in spring 44 tending to maintain the cam follower 37 in contact with the cam 38, will effect an increase in the peripheral speed of the article delivery member 31 until it returns to its retracted position ready for collection and severance of the next bag for that particular pocket* A plurality of spacer elements 40 is disposed in a spacer element introducing chute 4l by means of which spacer elements 40 may be intermittently introduced into certain pockets of the star-wheel 3, If, for example the tea bags in delivery chute 29 are to be packaged into bundles of ten then, since the star-wheel illustrated has ten pockets, a spacer element 40 will be released and permitted to enter a pocket 5 ' of the star-wheel during rotation thereof. After one complete revolution of the star-wheel a further spacer element will enter the same pocket 5· and will delimit the end of a batch of ten tea bags deposited on the delivery chute 29 during one rotation of the star-wheel* The construction of the spacer elements and the possible methods of packaging the tea bags In the apparatus described and illustrated in the present application release of the spacer element 40, which will be carefully synchronised with the passage of the appropriate pocket 5Ί past the outlet aperture of spacer chute 4l, will allow the spacer element 40 to fall into the pocket 5' alongside an already present tea bag 2· The tea bag 2 and the spacer element 40 will both be deposited on the delivery chute 28 together and will be advanced along the chute by the article retaining element 33 of the next following pocket 5· Clearly, some form of biasing will be required in order to control the tendeacy of the arms 35 to execute anticlockwise movement relatively to the star-wheel 3 which would result due to the centrifugal effect of in Figure 2, in which a stud 42 on the arm 35 and a further stud 43 on the star-wheel 3 are linked by a helical tension spring 44 thus urging them to move together, i.e. urging the stud 42 to move radially inwardly towards stud 43. The effect of this biasing spring will be to maintain the cam follower wheel 37 in contact with the cams surface 38· As also shown clearly in Figure 2, the shaft 11 is freely journalled in a supporting plate 45 which also carries the supporting shafts 26 and 27 and a further pin 46 which serves to locate the bracket 39 holding cam surface 38 in position. The other end of the shaft 11 is journalled in a support bracket 47 which is spaced from support plate 4 by a distance sufficient to accomodate the star-wheel assembly 3 between the plate 45 and bracket 47 and to prevent axial motion of the star-wheel 3 with respect to the shaft 11. As explained above the star-wheel 3 is freely rotatably mounted on the shaft 11. The disc 10 is fixedly mounted on a cylindrical extension 48 of the star-wheel 3 and also carries an integrally formed pinion 49. The pinion 49 is driven by a suitable transmission train and, because of the force fit between sprocket disc 10 and a similar sprocket disc 9 with the star-wheel assembly, the entire assembly 3, 9, 10 is driven for rotation about the axis of shaft 11* The operation of the described apparatus will be continuous and will enable high speed severing and packaging tea bags to be achieved.

Similarly, it is possible to use the apparatus of this invention for other operations where a continuous web is severed into discrete portions which are then to be delivered at a common station.

Clearly the adoption of the Figure 3 cam track arrangement would present certain problems if the cam 5 were to be positioned at the same place as the cam 21 in Figure 2, namely within the confines of the chain path. Thus it has been found advantageous to move the cam to a position clear of the chain path and hence free from interference with the movement axially of the shaft 26 so that it lies either between the chain 14 and the main frame 45 or at the opposite end of the apparatus alongside the chain 13· The various arms 18 and cam follower mounting brackets 55 will then need to be redesigned so that the cam follower wheel 53 is positioned laterally to one side of the associated knife blade 18 as depicted in Figure 4·

Claims (1)

1. I CLAIM: 1* A method of severing a continuous web to form a plurality of discrete portions, such method comprising feeding one end of the web to one pocket of a rotatable star wheel as herein defined, and having a fixed knife blade associated with each pocket, moving a co-operating knife blade past said fixed blade to effect severance of an end portion of the web from the remainder of the web, such portion being disposed within said one pocket of the star wheel, carrying the severed end portion round the axis of the star wheel to a delivery station and moving the severed portion radially outwardly and circumferentially rearwardly with respect to the star wheel prior to arrival at the delivery station* 2· A method according to claim 1, wherein the co-operating knife blade is moved radially inwardly of the star wheel past the fixed knife blade to effect severance. 3· A method according to claim 1 or 2, wherein the fixed and movable knife blades are synchronized to move together round a portion of the circumference of the star wheel so that severance of the web occurs while the star wheel is continuously rotating* 4· A method of severing a web, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings* 5· Apparatus for severing a continuous web to form a plurality of discrete portions, such apparatus comprising a star wheel as hereinbefore defined, means for feeding one end of the web to a pocket of the star wheel, a delivery station for receiving the severed portions after discharge from the star wheel, a plurality of knife blades fixed to the star wheel each associated with a pocket of the wheel J at least one movable knife blade co-operable with a fixed blade to sever from the web a portion in said pocket and moans for moving the severed portions radially outwardly and circumferent ally rearwardly of the star wheel during travel towards said delivery station* 6· Apparatus according to claim 5» and including a plurality of movable knife blades each one being co-operable with a different one of the fixed blades* 7* Apparatus according to claim 6, wherein said movable knife blades are mounted on a severing element which moves along an arcuate path substantially coincident with a part of the periphery of the star wheel* 8· Apparatus according to claim 7, wherein the severing element comprises a continuous chain having the movable knife blades pivotally attached to .link pins of the chain, each said knife blade being provided with a cam follower for co-operation with a cam track to effect pivotal motion between cutting and withdrawn positions* 9* Apparatus according to any one of claims 5 to 8t wherein a cutting edge of each movable blade is inclined with respect to the axis of the star wheel, and the fixed knife blades each have cutting edges parallel to the axis of the star wheel* 10* Apparatus according to any of claims 5 to 9» wherein said means for moving the severed portions radially outwardly and circumferentially rearwardly comprise article delivery members carried by the star wheel and movable between radially spaced locations during rotation of the star wheel* 11· Apparatus according to claim 10, wherein the article delivery members are in the form of V-shaped wing members which move along an arcuate path between an angularly advanced radially inner position and an angularly retarded radially outer position and entrain the severed portions in so doing, thereby lifting the severed portions clear of the star wheel pockets* 12, Apparatus according to claim 11, wherein the wing members are pivotally connected to the star wheel and are provided with cam followers which are deflected radially outwardly during passage along a fixed cam surface, the cam follower of each wing member, considered with respect to the direction of rotation of the star wheel, being angularly advanced with respect to · the point of pivotal connection of the aamo wing taedbbr* 13· Apparatus according to claim 12, wherein the wing members are resiliently biased towards their radially inner position to hold the cam followers in contact with the fixed cam surface, l4. Apparatus according to any one of claims 5 to 13, and including a delivery chute extending substantially radially of the star wheel and provided with at least one extractor tooth for removing severed web portions from the pockets of the star wheel* 15· Apparatus according to any one of claims 5 to 14, and including means for introducing spacer elements to selected pockets of the star wheel* l6, - Apparatus according to claim 8 or any ono of claims l 9 to 15 when appendant thereto, wherein registering bars are connected to other link pins of the chain and are arranged to co-operate with the fixed knife blades so that the web is firmly held between the fixed knife blade and an associated registering bar while an associated movable knife blade effects severance of the web* 17· Apparatus according to claim 8 or any one of claims 9 to 16 when appendant thereto, wherein the movable knife blades are substantially planar and have a cutting edge, each said blade being mounted on an arm formed of sheet material bent into an L-shape9 the knife blade being mounted on one limb of the L and the end of the other limb being pivotally connected to the severing element, the arrangement being such that the end edge of the first mentioned limb is disposed parallel to the axis of the star wheel* ·ΧΧ·68 18. Apparatus according to claim 17 wherein said first mentioned limb projects further radially inwardly of the star wheel than does the cutting edge of the blade* 19* Apparatus according to claim 17 or 18, wherein each movable knife blade has an alignment tooth at one end of the cutting edge so that said alignment tooth engages the fixed knife blade and ensures the two co-operating blades are aligned, the arm being made of a resilient material to accommodate any aligning adjustment induced by the alignment tooth* 20* Apparatus according to claim 8, or any one of claims 9 to 16 when appendant thereto, wherein each movable knife blade is attached to an arm which is pivotally mounted on a link pin of the chain* said arm being resiliently biased towards a withdrawn position* 21· Apparatus according to claim 8, or any one of claims 9 to 16 when appendant thereto, wherein the cam follower is a wheel riding in a groove or slot in a cam member( the movement of the cam follower to either its cutting or its withdrawn position being effected by means of one or other of the walls of the groove or slot* 22· Apparatus for severing a continuous web to form a plurality of discrete portions such apparatus being constructed and arranged substantially as hereinbefore described with reference to and as illustrated io Figures 1 and 2 of the accompanying drawings* 23· Apparatus according to claim 22, modified substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings·