Accordion, folding and cutting apparatus

Abstract

Apparatus for forming accordion folds in a longitudinally traveling web of substantially uniform width and indefinite length including web cutting means disposed upstream or downstream of said folding apparatus.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

The present application is a division of my earlier application Ser. No. 176,487 filed Aug. 31, 1971 and now issued as U.S. Pat. No. 3,784,188.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of paper converting and comprises apparatus for accordion folding and cutting of a continuous paper web supply.

2. Description of the Prior Art

The continuous, mechanized, accordion folding of a paper web of indefinite length has long been a valuable technique in the process of converting large, roll quantities of paper into smaller, more convenient units suitable for individual consumer handling. Through the years, many devices to perform this function have evolved as the demand for greater web speed has increased.

Among such prior art devices have been the inventions of Meisel, U.S. Pat. No. 568,307, and Teall, U.S. Pat. No. 1,290,800. Both of these inventions, like that of the present, utilize identical link chain carriers on opposite sides of an oncoming web having a multiplicity of projections secured with uniform spacing around the periphery of each chain set which operatively cooperate to displace the web first to one side of a center plane and then to the other, forming a small radius crease at the position of direction reversal. However, both of said earlier inventions require substantial dynamic mass as related to the fold length: an intolerable characteristic for high speed machinery.

Moreover, due to the large turning radius of such prior art machines, similarly large clearances from the point of crease formation to other cooperating machinery such as web cutters are required. An undesirable incident of such large clearances is the long, uncontrolled paper "tail" following a prefold web cut which must be caught and drawn into the accordion fold machinery to a point of positive control.

The present invention discloses a continuous web, accordion folding apparatus suitable for construction with small, light weight elements commensurate with high speed operation.

Another object of the present invention is to provide accordion folding apparatus requiring small operational clearance to decrease the proximity between a pre-creasing web cutter and the first point of positive control within the folding apparatus.

Other objects of the present invention include the disclosure of a post-creasing web cutting apparatus for severing a continuous web in the bight of a crease after the formation of same.

SUMMARY OF THE INVENTION

The folding apparatus of the present invention comprises two identical pairs of link-chain circuits, each pair being disposed on opposite face sides of an oncoming web of paper or other thin sheet material of indefinite length. Chain circuits respective to each pair are disposed for running in parallel planes around respective sprocket sets. Each chain in a pair has secured thereto the respectively opposite ends of several tucker and gripper bars extending between and across the two chains of a pair. Said tucker and gripper bars are positioned perpendicularly to the chain running plane and distributed alternately at uniform intervals around the circuit periphery.

Each gripper bar comprises two, channel shaped structural members, each having one leg thereof secured to one of two longitudinally contiguous chain links. The bight openings of said channels are disposed in facing opposition and filled with a soft, compliant substance such as elastomer.

Each tucker bar comprises a structural "T" element having the crossmember thereof secured to respective chain links and the T leg projecting perpendicularly therefrom.

Operationally, the two chain pairs are synchronized whereby the tucker bar on one chain pair coincides with the gripper bar nip opening of the other chain pair. As the two, longitudinally contiguous links retaining the gripper bar are turned over a small diameter sprocket, the consequent angular divergence between the gripper faces causes a nip to open therebetween. Said nip opening receives the tucker bar leg as it rolls a projection of the web into meshing contact with the nip opening. Separation from the sprocket returns the two contiguous gripper bar carrier links to a straight line geometry thereby closing the gripper faces on the web held therebetween.

Since the straight-run sections of chain circuit departing from the meshing sprockets are aligned for slight relative divergence, the tucker leg is withdrawn from the gripper nip at very slight planar misalignment. As soon, however, as the tucker leg is withdrawn from the gripper, the chain angle of divergence is increased greatly by turning around an idler sprocket having a chain engagement profile such as to retain a straight line geometry between the two contiguous gripper bar carrier links. This geometry prevents the gripper from opening and prematurely releasing the crease.

This increased divergence angle rapidly advances the web crease to the desired release position where at the chain circuit is directed around another, small diameter, conventional profile, sprocket for the purpose of opening the gripper to release the web.

If the web is to be cut following folding, a reciprocating blade engages the web along the crease bight. Simultaneously, a set of chain driven, cylindrical rollers are positioned against the web on the side opposite from the blade edge for loaded rolling contact there along to cut the web.

As an alternative embodiment of the invention, an interleaved series of short sheets may be accordion folded into a rectangular dispensing stack by prefold cutting the webs of two, independent supply streams into sheet length increments, merging the two supply streams into one, double layer stream with the transverse edges of one stream indexed to coincide with the midpoint between sheet edges of the other stream and orienting the double layer stream with the present folding apparatus to grasp, within the nip of a single gripper, two, serially adjacent, transverse sheet edges within the linking bight of a laterally adjacent sheet crease.

BRIEF DESCRIPTION OF THE DRAWINGS

Relative to the drawings wherein like reference characters designate like or corresponding parts throughout the several views;

FIG. 1 is a line schematic of the accordion folding apparatus of the present invention integrated with a post-fold cutting apparatus;

FIG. 2 is a partial elevational view of the folding apparatus of FIG. 1 as seen at cut II--II;

FIG. 3 is a detail of the chain carried tucker and gripper elements of the folding apparatus;

FIG. 4 is a schematic illustrating the mechanics operative in placing a transversely creased portion of web within the open nip of a gripper element;

FIG. 5 is a geometric detail of the cam element for turning the folding apparatus chain direction without prematurely opening the grippers;

FIG. 6 is a plan detail of the rolling cutter apparatus for cutting a web after the accordion fold is formed;

FIG. 7 is an isometric schematic showing the power transmission train to the rolling-cutter apparatus;

FIG. 8 is a plan view of an alternative scheme for selectively retracting the rolling cutters from the reciprocating blade table plane;

FIG. 9 is a sectional elevation of FIG. 8 as seen across cut IX--IX;

FIG. 10 is a second alternate to the rolling-cutter apparatus of the invention;

FIG. 11 is an exaggerated schematic of folded product from the apparatus illustrated in FIG. 12;

FIG. 12 is a folding apparatus of the present invention integrated with a prefold-cutting apparatus for producing the interleaved sheet product of FIG. 11.

FIG. 13 is a schematic of an alternative blade shape and associate web cutting pattern available from the roller-cutter apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

1. Operation Flow Sequence

Starting with the FIG. 1 schematic, a paper web W of indefinite length is shown as delivered to the accordion folding apparatus at a controlled rate by pulling rolls 20. Right and left roller chain circuits 3a and 3b functionally cooperate in the proximal region A to alternately engage the web W at regularly spaced distances along the web length. The engagement forms a straight crease or pinch line extending perpendicularly transverse to the web length axis with the bight openings of successive creases facing in alternately opposite directions, i.e. away from the chain supporting that particular crease.

Each crease is carried by its respective supportive chain to the lower, release proximity B where the web panel W.sub.4 is substantially horizontal and will gravity drop to a flat position without wrinkling.

Although this disclosure of the preferred embodiment describes the endless carrier elements 3a and 3b as roller chains, it should be appreciated that numerous alternatives, generically characterized as endless traction means, may be equally suitable for particular applications. Among such alternative may be included other types of chain drives, belts, ropes or cables. Relative rotational timing between the two circuits 3a and 3b is critical since rigid elements structurally secured to each circuit must physically cooperate by meshing. However, it is entirely possible to design a belt carrier system in which the inherent slippage between the traction carriers and the associate sheaves (sprockets) is not so great as to be within meshing tolerance from one meshing half cycle to the next. Coincident therewith, each incident of meshing would physically correct any misalignment of relative index occurring within the preceding half cycle of operation.

To cut the infinite length web W into uniform lengths terminating precisely along a crease bight centerline, a post-fold cutting mechanism 4 is disposed between the folding apparatus and product receiving hopper 9. If provision for cutting web creases falling on either side of web flow centerline C is desired, cutting mechanism 4 may comprise two blade tables 41a and 41b and two roller-cutting units 42a and 42b. Blade table 41a and roller unit 42a functionally cooperate as a set to sever crease lines on the right side of centerline C whereas table 41b and roller unit 42b cooperate for left side cuts, exclusively.

An alternative embodiment is illustrated by FIG. 12 where prefold cutting is performed on two web sources 10 and 11 for the purpose of interleaving one panel section of a folded sheet between integral panels of a second, folded sheet.

2. Folding Mechanism

Each chain circuit 3a and 3b in FIG. 1 comprises a pair of roller chains 30 encompassing sprockets 31, 32, 33 and cam 34. There being two, parallel, chain running planes, R and L, (FIG. 2), having rigid transverse structural ties (tucker 35 and gripper 36), in each chain circuit 3a and 3b, a total four chain closures, L30a, R30a, L30b and R30b, are described herein. It should be understood, however, that the number of running planes, e.g. R and L, may be increased for the purpose of folding wider paper. To do so, would increase the number of chain closures by two for each running plane added.

Both chain circuits 3a and 3b being of identical construction, further description will be focused on circuit 3a.

Relative to FIGS. 2 and 3, it may be seen that each gripper bar 36 comprises two, longitudinal structural channel elements 61 filled with elastomer 62. The interface between the two elastomer portions 62 is separable to form respective gripper jaws 66. The two elements 61 of each gripper bar 36 are respectively carried by the two, relatively articulatable, contiguous, link pairs 63o and 63i forming link set 64. Tabs 65, integral with the links 63, may be used as attachment platforms for the channels 61 to the links 63.

Tucker bar 35 is shown to be a unitary, extruded T or "L" element comprising cross-bar 51 and leg projection 52. Like the gripper 36, tucker bar 35 may be secured to link pair 53 by means of an attachment platform 55.

The number of tuckers 35 and grippers 36 allowed on each chain circuit is arbitrary above the permissible minimum of 2 tuckers and 2 grippers. For purposes of timing, coordination, etc., there should be a whole number ratio between the sum of grippers and tuckers and the length of the circuit in pitches.

The distance D between a gripper 36 and adjacent tuckers 35 on the same chain is related to, but not the same as, a panel length S. Therefore, the linear quantity of web W pushed by the rolls 20 between chain circuits 3a and 3b in the interim between points of tucker-gripper engagement is greater than the distance D as represented by the sag in FIG. 1 web sections W.sub.1 and W.sub.2.

The opening and closing operations of grippers 36 are functions of relative geometry as the chains are drawn over the periphery of sprockets 31 and 32. The distance P (FIGS. 3 and 5) between chain rollers 37 is held constant by the interconnecting rigid links 63. Accordingly, the sprocket pitch P may be defined as a chord subtending an .alpha. degree arc on the pitch circle M of radius of N (FIG. 4). Gripper faces 66 are placed at a distance K (FIG. 3) above the plane including the axes of two adjacent rollers 37 and disposed to abut, or nearly so, between sprockets when the roller center beneath the gripper face 66 falls into a plane common to the centers of those rollers adjacent both sides. Since the geometry of a link pair 63 between adjacent rollers 37 is rigid, when a gripper bar unit 36, having cooperative jaw elements on two adjacent link pairs 63i and 63 o of a link set 64, is drawn over the periphery of a sprocket, the jaws 66 are separated by a mean distance substantially equal to 2(K) (Sin .alpha.). As the chain departs from contact with a sprocket, the roller centers return to the straight line relationship thereby closing the jaws 66.

Rotational timing of the chain circuits 3a and 3b is as shown by FIGS. 1 and 4 whereby the tucker leg 52 of one chain circuit rolls between the opened jaws 66 of gripper 36 on the opposite chain circuit. Since the meshing of cooperative tuckers and grippers is from opposite sides of the web W, a portion thereof is pressed between the open gripper jaws 66 as shown in FIG. 4. As the chain rolls off the sprocket 31b, jaws 66 are pulled together to close on tucker leg 52, clamping the web W therebetween.

In order to withdraw the tucker leg 52 from the nip of jaws 66 without disrupting or damaging the web therebetween, the chains course half angle of departure .alpha. from sprockets 31a and 31b must be held to shallow maximums. The exact angle may be analytically derived by those of ordinary skill in the art but for purposes of example, half angle .alpha. may be in the order of 5.degree..

At this point in the operation, gripper 36 has established a crease in the web and leg 52 of tucker 35 has been withdrawn therefrom. Moreover, the crease held by chain circuit 3b is slightly to the left (FIG. 1) of center plane C. The next succeeding crease will be held by chain circuit 3a and will be drawn to the right of center plane C thereby establishing an accordion geometry bias. However, no reliably repetitive fall pattern may be acquired or positive control exercised if the web is released. Wrinkles and irregular stacking patterns will result if the web is released from the positions W.sub.2 or W.sub.1. Therefore, the generally vertical disposition of the accordion must be reoriented to a generally horizontal disposition as represented by web sections W.sub.3 and W.sub.4. To accomplish this result, the creased end of web section W.sub.3 held by chain circuit 3b must be advanced laterally (to the left) from the center plane C at a greater rate than the circuit 3a held crease of the same section W.sub.3. Simultaneously, the vertical displacement between the two ends of section W.sub.3 must be reduced.

An obvious technique of such reorientation is to increase the rate of circuit divergence by the half angle quantity of .beta. , 25.degree. for example, as by bending around an intermediate cam 34. But if the idler includes a conventional profile, gripper jaws 66 will open and release the web prematurely as the gripper bar 36 passes thereover.

To avoid this result, cam 34 of the present invention are provided with notches 38 which are rotationally timed to receive the center roller of the three roller groups supporting a gripper bar link set 64. As represented by FIG. 5 the centers of the three link set 64 supportive rollers 37 are allowed to sustain a straight line relationship at the point of chain tangency to the idler 34. The depth and profile of the notch 38 may be determined analytically by those of ordinary skill in the art from chain pitch P, chain roller radius r, the initial departure angle .alpha. and the final departure angle .beta. . Since link pairs 63i and 63o are precluded from relative angular displacement as the set 64 turns about idler 34, jaws 66 are held tightly closed on the crease of web W.

The next critical design point of the present invention is the vertical placement of release sprocket 32 below idler 34. The controlling criterion is the length of a moderately tensioned web section W.sub.3 so that gripper bar 36 on chain circuit 3b will open as the gripper 36 on chain circuit 3a moves into position to pull the 3b circuit crease from between jaws 66.

If only continuous and rapid accordion folding of web W is desired, the aforedescribed apparatus will flawlessly deliver a rectangular column continuum of accordion folded web to a receiving station such as chute or hopper 9.

However, if finite lengths of folded web, in whole number increments of web sections between creases, are desired, the aforedescribed folding apparatus may have integrated therewith the post-fold cutting mechanism 4.

3. Post-Fold Cutting Mechanism

The preferred embodiment of the post-fold cutter comprises two blade tables 41a and 41b disposed in the same plane below release sprockets 32.

The two tables 41a and 41b function alternately with one, 41a of FIG. 1, penetrating the material flow column between web sections W.sub.4 and W.sub.5 from the left of center plane C and the other, 41b, penetrating between web sections W.sub.3 and W.sub.4 from the right of center plane C.

Both tables 41a and 41b are provided with knife edges 43a and 43b for positionment within the bight of a crease.

Rotating into position against the knife edges 43a and 43b but from opposite sides of the web W.sub.1 are respective roller mechanisms 42a and 42b. As best illustrated by FIG. 6 relatively wide, flat tread wheels 44 cut the web W by pressing same against the knife edge 32a with rolling contact. Resiliently loaded backing bar 45 maintains a relatively constant contact pressure between wheels 44 and the web W to assure complete cutting across the full web width as the edge and tread surfaces wear. The treads of wheels 44 should be "flat," i.e. relatively long surface elements of a regular cylinder, to provide broad accommodation for the degree of functional misalignment as eventually, if not initially, occurs in high speed, cyclically reversing machinery.

Rollers 44 are mounted on carrier links 47 of a sprocket driven roller chain 46. Spacing between rollers 44 along the chain 46 may be as desired, one factor of consideration being the length of allowable cutting interim within an operational cycle: a smaller separation distance between rollers yields a shorter cutting time for a given chain speed.

It should be appreciated that a cutting operation performed by the aforedescribed apparatus of this invention is not only rapid due to simultaneous cutting of several small increments across the web width but is also neat, there being no opportunity for shredding due to blade misalignment. The present invention allows only one cut line, that allowed by the continuous line of knife edge 43a or 43b, regardless of the variance the edge line may follow from true (within the limits of the wheel 44 tread width). Therefore, a single, continuous cut line may be achieved with the rapidity of multiple cutters.

Although any number of mechanisms may be devised for selectively engaging the knife edges 43 with rollers 44, the schematic shown in isometric by FIG. 7 is of a particularly successful example. Knife tables 41a and 41b are mounted on guide bars 70 and reciprocably driven by four-bar crank mechanisms 71a and 71b. Since the web cutting operation is cyclical over an interrupted period, greatest flexibility for programing the cycle period is afforded by linking the input power line shaft 72 with the lateral, power transfer shafts 75a and 75b carrying lateral spur gears 73a and 73b through electrically latched, single revolution clutches 74a and 74b such as a Type 6 as specified by the Hilliard Corporation of Elmira, New York.

Condition sensory means such as a limit switch or photo sensory switch, not shown, for actuating either of clutches 73a or 73b by the emission of a suitable electrical signal, may be responsive to select portions of the folding mechanism or drive therefor such as the notched cam 34.

With each operational cycle of the blade tables 41a and 41b, so too, are positioned roller-cutter units 42a and 42b by means of carriage 48, parallel swing arms 49 and eccentric 77 driven connecting rod 76.

With clutch 74a engaged, for example, power is transferred from shaft 72 to shaft 75a via spur gear 73a. Shaft 75a transfers power to the four-bar linkage 71a via chain transmission 78a (thereby sliding blade table 41a between web panels W.sub.4 and W.sub.5 (FIG. 1)). Simultaneously, chain transmission 79a draws power from shaft 75 a to rotate eccentric 77a for raising the roller-cutter unit 42a into operative engagement with knife edge 43a mounted on blade table 41a.

Roller chain 46 carrying cutting wheels 44 is driven continuously by direct power take-off 80a from main input power shaft 72 thereby further minimizing the cutting delay time.

As of the aforedescribed point of operation, the cutting cycle for the crease joined web panels W.sub.4 and W.sub.5 is only half complete although the web is completely severed. However, since the ratio between the power shaft 72 gear is 2:1 for a complete cycle, the one revolution clutch 74a must be actuated a second time to withdraw blade table 41a from the web flow column. This second actuation may be keyed to such an event as the completion of a dump cycle for hopper 9 to remove the material collected therein and severed from the web W by the rolling-cutter apparatus.

After the cutting plane between guide bars 70 has been cleared by the retraction of roller-cutter 42a and blade table 41a therefrom, the circuit for actuating cutting apparatus 41b and 42b is prepared for completion by a second panel counting circuit. In this manner, web creases on sequentially opposite sides of the material flow axis C are cut with a predetermined number of integrally connected panels therebetween.

It should be understood that the scale and disposition of elements in FIG. 7 is distorted to further the ends of clarity and disclosure. Although the gear and sprocket ratios of the FIG. 7 mechanism are critical, they are so for a very limited product range. These are matters within the competence of ordinarily skilled practitioners of the art and need no further elaboration.

It should be noted, however, that depending on associated machine geometry and the nature of power available, the rolling-cutter mechanisms disclosed by FIGS. 8, 9 and 10 may be more suitable.

The FIGS. 8 and 9 embodiment, for example provides an alternative to physically displacing a driven sprocket under load as required the FIG. 7 mechanism. In FIGS. 8 and 9 the rolling contact surfaces are frustums of regular cones 81 carried on an expansible chain circuit 82 loaded tensionally by reciprocable load shoes 83a and 83b. Linking piston rods 84 fitted through cylinder block 85 rigidly unitize shoes 83a and 83b whereby fluid pressure resiliently biased against an annular collar piston surface (not shown) within the cylinder block 85 engages the rolling contact surface 81 with the knife edge 43a. When the cut is complete, fluid pressure bias on the piston collar is reversed to retract all chains and roller elements from the blade table reciprocation plane.

The rolling cutter mechanism of FIG. 10 is highly simplified and represents the basic elements of an application where the most convenient power application is a single or double stroke linear displacement of a machine element from point Y to point Z. The elements of FIG. 10 include the arcuate segment of a cylinder having a radius E. The cylindrical surface 86 is rolled into contact with the knife edge 43a by driving a rod or roller element 87 along arcuate slot 88 from point Y to point Z. As surface 86 rolls about the axis F, the axis position translates to point F'.

FIG. 13 further illustrates the design flexibility available to the present invention by allowing complex cutting patterns such as the undulating or scalloped edge of panel W.sub.5 ' without sacrifice of cutting speed or precision. Since the thread width of rollers 37 exceeds the amplitude of knife edge 43c undulations, the cut line for web W.sub.5 ' will follow exactly that of the knife edge notwithstanding the fact that several rollers 37, rapidly traversing short increments of the web width, serve as separate anvils over respective increments.

Many variations of the scalloped edge scheme of FIG. 13 may be comprehended within the teaching of the invention, such as Greek scroll or sawtooth, the primary criterion being that the web W is pressed against all transverse elements of the edge 43c by loaded, rolling, contact pressure.

4. Prefold Cutting Mechanism

Due to the relatively short radial clearance required by the sweep of tucker 35 and gripper 36 devices of the present invention, it is also possible to integrate the present accordion folding apparatus with prefold cutting apparatus to deliver a continuum of interleaved, single folded sheets as schematically represented by FIG. 11. Distinctive characteristics of the FIG. 11 product include sheets 23, folded so as to open to the left of the center line, and sheets 24, folded so as to open to the right of the center line. The upper panels 23u of sheets 23 are disposed to overlie the lower panels 24L of sheets 24. Conversely, panels 24u overlie panels 23L. An integral pair of panels, 23a and 23L for example, are joined by the bight of a crease 23b.

Relating now to the FIG. 12 apparatus for producing the product of FIG. 11, there are shown two web supply streams 13 and 14 pulled from reels 10 and 11 by pulling rolls 15 and 16. Rotary knives 17 and 18 cut the respective webs into a continuum of sheets 23 and 24, respectively.

Subsequent to cutting, the two supply streams are merged into a single plane of supply 21 by the converging nip 22 between belt conveyors 25 and 26. Rotation of the knife 17 is timed for 180.degree. angular phase displacement from the rotation of knife 18 so that upon emergence from the nip 22, the transversely cut edges of serially adjacent sheets 23 from supply stream 13 align with the approximate midpoint between transverse edges of laterally adjacent sheets 24. From the nip 22, the single supply stream 21 is delivered to the pickup area A between sprockets 31a and 31b where the junction between serially adjacent edges of sheets 23 and the midpoint of sheets 24 is pressed into the nip of grippers 36.

As the foregoing cycle is reversed and repeated, panels from respective webs are interleaved in the manner represented by FIG. 11.

Claims

Having disclosed a specific, preferred embodiment, I claim as my invention:

1. An apparatus for folding thin sheet material of relatively constant width and indefinite length into a continuum of reverse folded panel sections of uniform length comprising:

A pair of flexible tensile elements having first and second opposed faces, respectively, each tensile element disposed in respective closed, parallel-planar circuits around a plurality of wheel elements having rim portions rotatable about axes positioned within the periphery of a respective circuit and substantially perpendicular to the plane thereof, the first face of said tensile elements being disposed adjacent said rim portions;

Sheet material tucker means and gripper means secured to and projecting from the second face of each tensile element in uniformly spaced, alternate positions thereabout, each gripper means comprising a cooperative pair of gripping elements, each gripping element being rotatable about a pair of articulation axes rigidly positioned relative to said gripping element, passing through the respective tensile element and disposed substantially perpendicular to the plane of the respective closed circuit, said cooperative pair of gripping elements being adjacently positioned longitudinally along said tensile element whereby projecting portions of each gripping element are relatively drawn to a closed position to cooperatively grip a transverse portion of sheet material therebetween when all articulation axes respective to said cooperative pair are disposed in a common plane;

A first of said wheel elements respective to each closed circuit being relatively positioned to guide said tensile elements into a meshing region of sufficient proximity for registered tucker means on one tensile element to mesh between a cooperative pair of gripping elements on the other tensile element that are opened by an arcuate disposition of the articulation axes respective to said gripping elements against the rim of the respective first wheel element whereby a transverse portion of sheet material is tucked between said gripping elements;

A second of said wheel elements respective to each closed circuit being positioned relative to said first wheel element whereby a first portion of the respective closed circuit therebetween follows a first substantially straight line path between tangency with said first and second wheel elements, said first straight line paths respective to both closed circuits being aligned to relatively diverge at a first included angle from said meshing region to withdraw said tucker means from between said gripper elements;

A third of said wheel elements respective to each closed circuit being positioned relative to said wheel element whereby a second portion of the respective closed circuit follows a second substantially straight line path between tangency with said second and third wheel elements, said second straight line paths respective to both closed circuits being aligned to relatively diverge from tangency with said second wheel element at a second included angle that is greater than said first included angle; and

Each of said second wheel elements further comprising profile means in the rim surface thereof that is rotatively registered to engage all articulation axes of a cooperative pair of gripping elements with a rim surface discontinuity, said profile means simultaneously supporting all of said articulation axes associated with said cooperative pair of gripping elements in a common plane that is substantially perpendicular to the plane of the respective closed circuit to prevent said gripping elements from opening to release said sheet material while said gripping elements are carried by the movement of a respective tensile element along a respective closed circuit from said first straight line path to said second straight line path.

2. Apparatus as described by claim 1 wherein each laterally spaced flexible tensile element of said pair comprises a pair of tensile members circulating about laterally spaced, parallel-planar closed courses, said gripping elements comprise a pair of parallel gripping bar elements spanning between respective pairs of said tensile members, said tucker means comprising a single bar element spanning between respective pairs of said tensile members.

3. Apparatus as described by claim 2 wherein said gripping bar elements are drawn to the closed position by tensile forces within respective tensile elements while in traverse along said first and second straight line paths.

4. Apparatus as described by claim 3 wherein said tensile members comprise a closed loop of pivot journal joined rigid link elements, said second wheel element rim surface discontinuity comprising a notch in said rim of sufficient depth to receive a pivot journal between a cooperative pair of gripping bar supporting link elements in the same plane as adjacent link pivot journals while in traversal about the rotational axis of said second wheel element between said first and second straight line paths.

5. Apparatus for folding a continuous web comprising:

A pair of continuous link chain assemblies, each assembly comprising an endless loop of pivot journal joined rigid link elements, each loop having respective inner and outer peripheries, each assembly being disposed in a respective closed planar circuit around at least three sprocket wheels having rim portions rotatable about axes positioned within the periphery of a respective closed circuit and substantially perpendicular thereto the closed circuits respective to said pair of assemblies being substantially coplanar aligned;

Web material tucker means and gripper means alternatively positioned around and projecting from the outer periphery of each chain assembly and secured to respective links therein, each said gripper means comprising a cooperative pair of gripper elements secured respectively to two longitudinally adjacent links that are relatively pivotable about an axis through a common journal whereby a web of material is gripped between said cooperative pair of gripper elements, when all pivot axes respective to the respective two gripper element supportive links are disposed in a common plane;

A first pair of said sprocket wheels comprising one sprocket wheel within each circuit being relatively positioned whereby a tucker means secured to a link in one chain assembly will mesh between a cooperative pair of gripper elements on the other chain assembly to tuck a transverse crease of said web material between said gripper elements when link journals respective to said meshing gripper elements and tucker means are arcuately disposed against respective first sprocket wheel rim portions;

A second pair of said sprocket wheels comprising one sprocket wheel within each circuit, each being positioned relative to respective first sprocket wheels whereby a portion of the respective chain assembly circuit follows a first substantially straight line path between tangency with said first and second sprocket wheels, said first straight line paths respective to said pair of chain assembly circuits being relatively diverging at a first included angle from tangency at said first sprocket wheel to withdraw said tucker means from between said cooperative pair of gripper elements;

A third pair of said sprocket wheels comprising one sprocket wheel within each circuit, each being positioned relative to respective second sprocket wheels whereby a portion of the respective chain assembly circuit follows a second substantially straight line path between tangency with said second and third sprocket wheels, said second straight line paths respective to said pair of chain assembly circuits being relatively diverging at a second included angle from tangency with said second sprocket wheel, said second included angle being greater than said first included angle; and

Each of said second pair of sprocket wheels further comprising profile means in the rim surface thereof that is rotatively registered to engage all pivot journals respective to a cooperative pair of gripper element supporting links with a rim surface discontinuity, said profile means simultaneously supporting all of said supporting link pivot axes in a common plane that is substantially perpendicular the plane of respective chain assembly circuits to prevent said gripper elements from opening to release said web material while said gripper means are carried by the movement of a respective chain assembly along a respective circuit from said first straight line path to said second straight line path.