Web Folding Apparatus And Method

Abstract

A machine for interfolding tissue webs which includes a series of folding devices having successive left and right pairs of curved folding shoulders, with the shoulders in each pair being spaced apart to define a generally slot-shaped opening therebetween. An adjustable conveyor draws the longitudinal edge portions of each web along the respective folding shoulders of the corresponding folding device, and the device holds the received edge portions in spaced-apart relationship with each other until after the web reaches the second succeeding folding device. The second succeeding device then closes the edge portions to fold the web into a continuously moving stack of webs. As each web is received by the corresponding folding device, a shallow trough is formed in the web, and the infeed portion of the device directs this trough at approximately a right angle with respect to the path of the continuously moving stack. The trough is then turned inside out, and the web direction is changed so that it is substantially parallel to the path of the stack. The trough is gradually closed as it moves along the curved folding shoulders of the device and on past the next and then the next device. Before the trough is completely closed, an edge portion of the succeeding web is inserted therein. The webs are led to the folding devices from a plurality of supply rolls disposed along a single side of the machine. One supply roll is provided for each group of four folding devices, and the material from each roll is cut to the appropriate width to form the webs as it is advanced toward the folding devices. The various supply rolls include inflatable core assemblies which may be quickly and easily inserted in and withdrawn from the paperboard cores of the rolls. When the material from a given roll is exhausted, a back-up roll is moved into position, and the spent core is deposited on a conveyor which transports it to one end of the machine.

Description

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and method for interfolding a succession of webs and more particularly to an apparatus and method for advancing the webs along a feed path and interfolding the webs through the use of a series of folding devices positioned along the path.

There has been developed over the years a number of tissue interfolding machines. Representative machines of this type are disclosed, for example, in U.S. Pat. No. 2,642,279 granted June 15, 1953; U.S. Pat. No. 3,285,599 granted Nov. 15, 1966, U.S. Pat. No. 3,472,504 granted Oct. 14, 1969, and U.S. Pat. No. 3,542,356, granted Nov. 24, 1970. As will be understood, consumer size boxes of tissue commonly contain 100 or more separate sheets in short lengths cut from a long stack. The stack is assembled by bringing together a corresponding number of tissue webs from separate supply rolls. As the webs are assembled in the stack, they are interfolded by a series of folding devices to produce one or more longitudinal folds on each web. The assembled stack is cut off into convenient lengths which are then packaged in wrappers or paperboard boxes for use by the consumer.

In interfolding apparatus and methods employed heretofore, difficulties were encountered in assembling the webs in the stack at the requisite high speed while at the same time avoiding wrinkles, creases or breakage of individual webs. In many types of interfolding machines, the various folding devices included boards, rods or other structural elements which formed well-defined line contacts, and the webs tended to wrinkle or crease as they moved over such elements. The wrinkling and creasing of the webs was of special moment in cases in which the webs were folded too quickly or were otherwise subjected to unnecessary handling, such as in machines where a given web was folded and then reopened for insertion of an edge portion of a succeeding web, or where an edge portion was turned sharply over or under itself in a so-called "reverse" fold, for example. These problems represented a serious deficiency in machines used heretofore and often resulted in a substantial wastage of material and an inferior product.

Still another difficulty encountered in several previous machines arose because of the increasing height of the stack of webs as it moved along its feed path toward the outfeed end of the machine. As the stack approached the outfeed end, it frequently exhibited a tendency to bind, with the result that the overall efficiency of the machine was further impaired.

Additional difficulties exhibited by many prior interfolding machines resulted from the core assemblies used within each supply roll to facilitate the handling of the roll and its positioning on the machine. When a given roll exhausted its supply of tissue, for example, the spent core was manually removed from the machine, and the handling assembly within the core was detached in a more or less haphazard manner. The time required to remove the core, detach the handling assembly, insert the assembly in a fresh roll and position the fresh roll on the machine was excessive and resulted in unnecessary delays in the tissue folding operation.

SUMMARY OF INVENTION

The present invention is useful wherever a stack or package of folded webs is desired. The invention overcomes the foregoing and other disadvantages and achieves its primary object particularly in facial tissue manufacture by the provision of a new and improved machine and method for interfolding a succession of webs.

More specifically, an object of this invention is to provide such interfolding apparatus and method which avoids the unnecessary formation of creases and wrinkles in the webs being folded.

Another object of the invention is to provide an apparatus and method of the character indicated in which the handling of the various web supply rolls and cores therefor is greatly facilitated.

An additional object of the invention is to provide a web interfolding machine which is capable of high speed operation but which may be rapidly brought to rest without substantial breakage or slackness of the webs.

A further object of this invention is to provide an interfolding machine which is adjustable in accordance with the varying heights of the stack of webs being folded.

Still another object of the invention is to provide an interfolding apparatus and method in which the core assemblies for the individual supply rolls are readily inserted in and removed from the roll cores.

A still further object of the invention is to provide a high speed web folding machine utilizing comparatively simple mechanical components which is economical to manufacture and thoroughly reliable in operation.

In one illustrative embodiment of the invention, there is provided a machine and method for interfolding a group of webs from a plurality of supply rolls of tissue or other sheet material. The webs are led in a unique manner to a series of folding devices, one for each web, which are disposed in spaced relationship with each other along a feed path. Successive folding devices have alternate left and right pairs of curved folding shoulders, and the shoulders of each device are arranged to form a trough in the corresponding web and to initiate the gradual closing of the trough. As the web moves past succeeding folding devices, the gradual closing of the trough is continued, but the trough is not fully closed until after an edge portion of the next web is located in the trough. The thus interfolded webs are advanced in a stack by a belt type conveyor, and the stack is cut to appropriate lengths at the outfeed end of the conveyor for packaging and delivery to the purchaser.

In accordance with one feature of several embodiments of the invention, each folding device (except the first device) is provided with a guide member which receives the web from the immediately preceding folding device and continues the gradual closing of the trough while positively preventing the completion of the fold. The trough is not closed until after an edge portion of the succeeding web has been laid down and the web has moved past a following folding device. The arrangement is such that the trough in each web is closed in an extremely gradual manner by three successive folding devices, and there is no necessity for folding and then reopening the edge portions of the web in order to insert a succeeding edge portion therebetween.

In accordance with another feature of the invention, in certain preferred embodiments, the curved folding shoulders on each folding device are of comparatively large radii and are arranged such that the webs seek their own position as they approach the continuously moving stack. During the interfolding operation sharp reverse folds and other abrupt changes in direction of the edge portions of the webs are avoided, and the incidence of unwanted creases or wrinkles in the assembled webs is greatly reduced.

In accordance with a further feature of certain advantageous embodiments of the invention, as each web is received by its folding device a shallow trough is formed in the web, and the trough is then turned inside out and the web direction changed so that it is substantially parallel to the path of the stack. The inside out trough passes smoothly and easily over the curved folding shoulders of the folding device and is closed by the second succeeding folding device to fully interfold the web into the stack.

In accordance with an additional feature of several embodiments of the invention, the curved shoulders of each folding device are spaced apart to define a generally slot-shaped opening therebetween. The fold is initiated in the portion of the web which passes along the slot-shaped opening, with the result that an extremely smooth and uniform fold is produced.

In accordance with still another feature of the invention, in several good arrangements, the supply rolls for the webs are located along only a single side of the web feed path but include novel infeed mechanisms which direct the successive webs to the conveyor from opposite sides of the path. With this arrangement, the handling of the supply rolls and the spent cores therefor is greatly facilitated.

In accordance with a further feature of certain advantageous embodiments of the invention, there is provided a cutter mechanism for each supply roll which divides the sheet material from the roll into a plurality of webs. The number of supply rolls is substantially less than the number of webs, and the time needed for monitoring and replacing the rolls is accordingly reduced.

In accordance with a still further feature of the invention, in some embodiments, the machine includes a mechanism for depositing the spent cores for the supply rolls on a conveyor which transports the cores to a central location adjacent one end of the machine. A back-up roll adjacent each supply roll is then moved into an operative position on the machine. As a result, the time required for replacing a given roll is substantially reduced.

In accordance with another feature of the invention, in certain arrangements, the cores for the supply rolls are provided with core assemblies which may be readily expanded and contracted from one end of the core. The assemblies are readily inserted in and withdrawn from the cores in a rapid and straightforward manner.

In accordance with still another feature of the invention, in some embodiments, the assembled webs are advanced along the stack by a conveyor having an outfeed portion which is adjustable to conform to the height of the stack. To avoid unnecessary strain on the webs, each of the supply rolls is provided with an independent drive mechanism which is synchronized with the stack conveyor, thus providing an extremely smooth and uniform flow of material from the supply rolls to the outfeed end of the machine. The cutter mechanism also includes an independent drive for the material. In addition to its other advantages, the use of a plurality of independent drive mechanisms facilitates the rapid and smooth stopping of the material when the machine is shut down without substantial breakage or slackness of the webs.

The present invention, as well as further objects and features thereof, will be understood more clearly and fully from the following description of certain preferred embodiments, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a plurality of tissue webs being interfolded into a stack of webs in accordance with one illustrative embodiment of the invention.

FIG. 2 is a sectional view of the interfolded webs taken along the line 2--2 in FIG. 1.

FIG. 3 is a perspective view of portions of two successive folding devices which are representative of the devices used to form the folds shown in FIGS. 1 and 2.

FIG. 4 is a top plan view of one of the folding devices illustrated in FIG. 3.

FIG. 5 is a side elevational view of the folding device shown in FIG. 4.

FIG. 6 is a rear view of the folding device as seen from the left of FIG. 5.

FIG. 7 is a front view of the folding device as seen from the right of FIG. 5.

FIGS. 8, 9 and 10 are vertical sectional views taken along the corresponding lines 8--8, 9--9 and 10--10 in FIG. 5, with portions of the structure omitted for purposes of clarity.

FIG. 11 is a front view of the device as seen from the line 11--11 in FIG. 5, with portions of the structure omitted for purposes of clarity.

FIG. 12 is a sectional view taken along the line 12--12 in FIG. 5.

FIG. 13 is a side elevational view similar to FIG. 5 but showing additional structure.

FIG. 14 is a fragmentary top plan view of a series of folding devices and their associated webs in position on the machine.

FIG. 15 is a fragmentary side elevational view of the portion of the machine shown in FIG. 14.

FIGS. 16 and 17 are vertical sectional views taken along the respective lines 16--16 and 17--17 in FIG. 15 to illustrate the folding of one of the webs by a right-hand folding device, with portions of the structure omitted for purposes of clarity.

FIGS. 18 and 19 are vertical sectional views taken along the respective lines 18--18 and 19--19 in FIG. 5 to illustrate the folding of one of the webs by a left-hand folding device, with portions of the structure omitted for purposes of clarity.

FIGS. 20 and 21 are vertical sectional views of the webs taken along the respective lines 20--20 in FIG. 15 to illustrate the webs at succeeding points along the path of the stack.

FIG. 22 is a fragmentary top plan view of a folding bar and associated parts for changing the direction of movement of a web preparatory to its insertion into the stack.

FIG. 23 is a vertical sectional view taken along the line 23--23 of FIG. 22.

FIGS. 24 and 25 are sectional views taken along the respective lines 24--24 and 25--25 in FIG. 23.

FIG. 26 is an end elevational view of a machine for interfolding a series of webs, with certain parts omitted and others shown in section.

FIG. 27 is a vertical sectional view, partly broken away, of a tissue supply roll for the machine having an expandable core assembly, taken along the line 27--27 in FIG. 26.

FIG. 28 is a top plan view of a portion of the machine as seen from the line 28--28 in FIG. 26, with some of the backup rolls omitted for convenience of illustration.

FIG. 29 is an enlarged fragmentary sectional view taken along the line 29--29 of FIG. 28.

FIG. 30 is an enlarged end elevational view similar to a portion of FIG. 26 but showing certain of the parts in different positions.

FIG. 31 is a side elevational view of the machine frame and associated components adjacent the outfeed portion of the machine.

FIG. 32 is a side elevational view of the machine frame and associated components adjacent the infeed portion of the machine.

FIGS. 33, 34 and 35 are schematic illustrations of the varying positions of the conveyor for the stack of webs.

FIG. 36 is a perspective view of two folding devices and cooperating components in accordance with another illustrative embodiment of the invention, together with a schematic representation showing the location of the tissue webs being interfolded.

FIG. 37 is a vertical sectional view of the webs taken along the line 37--37 in FIG. 36.

FIG. 38 is a fragmentary side elevational view of a folding device in accordance with a further illustrative embodiment of the invention, together with a schematic representation showing the location of the tissue webs being interfolded.

FIG. 39 is a vertical sectional view of the webs taken along the line 39--39 of FIG. 38.

FIG. 40 is a fragmentary vertical sectional view of an alternative conveyor and adjustment mechanism useful in connection with the invention.

FIG. 41 is a fragmentary sectional view taken along the line 41--41 in FIG. 40.

DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

As will be understood, the process of producing facial tissues includes the drawing together and folding into a continuous stack many tissue webs from a long line of tissue supply rolls. The stack is cut off into convenient lengths which are then packaged in wrappers or paperboard boxes which go to the consumer.

In the version of the present invention illustrated in the drawings, the supply rolls are supported about fixed axes, and the webs are fed through a series of folding devices onto a stack which is moved relative to the supply rolls. In other versions of the invention, however, the supply rolls may be supported about axes which travel in a closed path countercurrent to the direction of movement of the stack, so that the relative movement of the webs and the supply rolls is the resultant of the combined movement. These latter versions are substantially shorter than the illustrated version and are of particular utility in cases where space is at a premium. For a more detailed description of the countercurrent movement of the supply rolls and the webs, reference may be had to U.S. Pat. Nos. 3,285,599 and 3,472,504 identified above.

In order to facilitate the description of the illustrated embodiments of the invention, there will first be given a description of the construction and mode of operation of the various folding devices for interfolding the webs into the stack. There will then be described the construction and operation of the overall interfolding machine, including the supply rolls and their core assemblies, the roll drive mechanisms, the tissue cutting assemblies and the conveyor for the stack. That description will be followed by a description of various alternative folding devices that may be employed on the machine.

THE WEBS AND THEIR FOLDING DEVICES

Referring to FIGS. 1 and 2 of the drawings, there is shown a plurality of facial tissue webs 50 being interfolded and assembled into a longitudinally extending stack 51 which defines a feed path. In the drawings, the reference numerals for the webs 50 are followed by an alphabetical suffix in order to differentiate therebetween. Thus, FIG. 1 is illustrative of five successive webs 50a, 50b, 50c, 50d and 50e as they are interfolded into the stack 51. During the folding operation, a median or "V" fold 52 is formed in each web along its longitudinal center line, and this fold divides the web into a pair of edge portions, such as the edge portions 50a1 and 50a2 of the web 50a. The edge portions of the various webs extend in transverse cross-section continuously from the fold 52 to the opposite edges of the web. The lowermost edge portion of each web is interfolded between the edge portions of the immediately preceding web, with the result that after the stack has been cut to box-size lengths and packaged, the removal of a given tissue from the box causes an edge portion of the tissue therebeneath to "pop up" into removal position.

The webs 50 are introduced into the stack 51 from opposite sides of the feed path. The web 50a is folded with the opening between its edge portions to the right, when viewed in the direction of movement of the stack, thus forming a right-hand fold. The successive webs are folded alternately to provide a left-hand fold in the web 50b, a right-hand fold in the web 50c, a left-hand fold in the web 50d, a right-hand fold in the web 50e, and so on.

As each of the tissue webs 50 approaches the stack 51, the web is traveling in a direction which meets the path of the stack at approximately a right angle. A shallow trough 53 is formed in the web, and the web direction is then changed so that it is substantially parallel to the stack. As the web changes direction, the trough 53 is turned inside out to produce a longitudinally extending trough 54, the inversion of the web being assisted by the natural stretchability of the tissue. The trough 54 is gradually closed by moving the edge portions of the web along gradually curving paths to initiate the formation of the fold. The fold for each web is not completed, however, until after the web passes the point along the stack at which the trough 54 is formed in the second succeeding web. With respect to the web 50a, for example, the edge portions 50a1 and 50a2 are positively maintained in spaced-apart relationship with each other to prevent the completion of the fold as the first succeeding web 50b reaches the stack and its lowermost edge portion 50b1 is inserted between the open edge portions of the web 50a. The edge portions 50a1 and 50a2 continue in spaced relationship as the web 50a moves past the point at which the trough 54 is formed in the second succeeding web 50c. The edge portions 50a1 and 50a2 are then closed, and the webs proceed along the path of the stack in interfolded relationship with each other.

The interfolding of the various webs 50 is performed through the use of a series of folding devices 55 which are mounted in spaced relationship with each other along the feed path defined by the stack 51. One of these folding devices is provided for each of the webs to be interfolded, and alternate devices are mirror images of each other to initiate the formation of right-hand and then left-hand folds. In FIG. 3, for example, there are shown a right-hand folding device 55c for the web 50c and a left-hand folding device 55d for the web 50d. The devices 55c and 55d are each provided with a pair of surfaces 56 and 57 which have curved folding shoulders 58 and 59. As each of the webs 50c and 50d approaches the corresponding device 55c or 55d, it passes over a guide roller 60 immediately adjacent the infeed side of the folding device and is then drawn along the device with its upper and lower edge portions in respective contact with the folding shoulders 58 and 59. The shoulders direct the edge portions along gradually curving paths to initiate the formation of the fold.

Each of the folding devices 55 is of one-piece construction and illustratively may be cast from aluminum or other material or may be bent from a single flat sheet of rectangular configuration. FIGS. 4-13 depict a right-hand folding device, it being understood that the left-hand folding devices are of similar construction but are reversed as shown by the device 55d in FIG. 3. The folding shoulders 58 and 59 of all of the devices are spaced apart to define a generally slot-shaped opening 62 therebetween. The opening 62 extends in a direction substantially parallel to the feed path of the stack of webs but gradually slopes downwardly toward the path such that the inner longitudinal edges 63 and 64 (FIG. 5) of the surfaces 56 and 57 form small acute angles .theta. amd .theta.' with the stack. As best shown in FIG. 4, the edge 64 of the surface 57 lies in a vertical plane which is parallel to the direction of movement of the stack.

The rearward portion of each of the folding devices 55 is provided with a triangular infeed surface 65. Two additional triangular surfaces 66 and 67 are interposed between the respective surfaces 56 and 57 and the infeed surfaces 65. The intersections between the surfaces 56 and 66 and between the surfaces 57 and 67 are of relatively large radii to form the respective folding shoulders 58 and 59. The common intersection of all of the surfaces includes a keyhole-shaped opening 68 to eliminate the slight hump that would otherwise be present. The opening 68 is contiguous with the infeed end of the slot 62, and the major portion of the opening is disposed in the surface 65.

A guide member 70 (FIG. 13) is bolted or otherwise rigidly secured to the lowermost surface 67 of each of the folding devices 55. The guide member 70 includes a curved shoulder 71 which is disposed immediately beneath the folding shoulder 59. The shoulder 71 slopes downwardly toward the stack of webs therebeneath.

As best shown in FIG. 14, the infeed rollers 60 for alternate ones of the folding devices 55 are positioned on opposite sides of the feed path defined by the stack of webs 51. Thus, the rollers 60 for the right-hand folding devices 55a and 55c are located on one side of the feed path, and the rollers for the left-hand folding devices 55b and 55d are located adjacent the opposite side of the feed path. The folding devices 55 are staggered with respect to the feed path, with the folding shoulders 58 and 59 (FIG. 13) of successive devices arranged in alternate right and left pairs. The additional shoulders 71 on the devices 55 likewise alternate, such that the shoulders 71 on successive devices extend over the feed path from opposite sides.

Pivotally mounted adjacent each of the rollers 60 is a guide bar 74. The bar 74 meets the direction of movement of the stack of webs at an acute angle which illustratively is of the order of forty-three degrees but which may be quickly and easily adjusted to provide a smooth and uniform flow of tissue around the bar. The lower end of the bar 74 is pivotally supported in a recess 76 (FIGS. 22-25) in a mounting block 77. A forwardly extending arm 78 is disposed within the recess 76 and is affixed at one end to the lower end of the bar. A bolt 79 at the opposite end of the arm 78 extends through oblong slots 80 in the block 77. To adjust the angle between the bar 74 and the direction of movement of the stack of webs, the bolt 79 is loosened to permit pivotal movement of the bar relative to the block.

The mounting block 77 for each of the guide bars 74 is welded or otherwise secured to a slidable plate 82. As best shown in FIG. 25, the plate 82 is interposed between a pair of fixed guides 83 which are respectively disposed along the longitudinal edges of the plate to permit movement of the plate and the attached guide bar in a direction parallel to the stack of webs. A knurled knob 84 adjacent the forward end of the plate 82 controls a threaded post 85 which extends through an oblong aperture 86 in the plate 82 into a fixed plate 87 mounted on the frame of the machine. Upon the loosening of the knob 84, the plate 82 and its attached guide bar 74 may be moved in a forward or rearward direction along the path of the stack to permit an additional adjustment in the position of the bar, and hence the position of the web 50 on the roller 60.

The successive webs 50a, 50b, 50c and 50d (FIGS. 14 and 15) approach the corresponding folding devices 55a, 55b, 55c and 55d from above and from opposite sides of the feed path. Each web passes around the angularly extending guide bar 74 to change the direction of movement of the web from a substantially vertical direction to a rearward direction. The web then moves over the roller 60 and enters its folding device with the web in contact with the triangular infeed surface 65. As the web proceeds along the folding device, the upper and lower longitudinal edge portions are drawn along the triangular surfaces 66 and 67, respectively.

The portion of the web 50 in contact with the infeed surface 65 is moving in a direction substantially transverse to the direction of movement of the stack of webs. The portions of the web in contact with the surfaces 66 and 67, on the other hand, are disposed in planes which are substantially parallel to the direction of movement of the stack. As a result, during its movement over the surface 65 the web becomes slightly bowed to form the shallow trough 53.

The web 50 moves from the infeed surface 65 into contact with the folding shoulders 58 and 59. As the web contacts these shoulders, it changes direction approximately ninety degrees so that it is travelling substantially parallel to the path of the stack. Simultaneously, the shoulders 58 and 59 act on the web to turn the trough 53 inside out, thus forming the trough 54. Upon continued movement of the web along the folding device, the edge portions of the web ride along the shoulders and are gradually urged toward one another to begin the closing of the trough along the fold line.

At the time the web 50a, for example, nears the outfeed end of its folding device 55a and reaches the position shown in FIG. 17, the formation of the trough 54 has been initiated, and the edge portion 50a1 is disposed above the edge portion 50a2. However, the edge portions 50a1 and 50a 2 are maintained in spaced-apart relationship with each other at this point along the path of travel to prevent the completion of the fold.

As the web 50a continues its movement along the feed path and reaches the immediately succeeding folding device 55b, the folding shoulder 71 on the guide member 70 is located within the trough 54. As best shown in FIG. 18, the guide member 70 is interposed between the edge portions 50a1 and 50a 2 to affirmatively prevent the completion of the fold in the web 50a. The succeeding web 50b moves around the corresponding bar 74 and the roller 60, and the web enters the folding device 55b with the web in contact with the infeed surface 65. In the position shown in FIG. 19, the edge portions 50b1 and 50b2 of the web 50b are in facing contact with the surfaces 56 and 57, respectively, on the folding device 55b. In this position the edge portion 50a1 of the web 50a rests on the upper surface of the edge portion 50b2 and is interposed between the portions 50b1 and 50b2.

The trough 54 in the web 50a remains open as the web moves from the folding device 55b to 55c. The web 50a passes beneath the device 55c, and by the time it reaches the position shown in FIG. 20 it is fully interfolded into the stack.

In a similar manner, the fold in the succeeding web 50b is initiated as the web passes along the folding shoulders 58 and 59 of the folding device 55b. As the web 50b continues its movement, the completion of the fold is affirmatively prevented by the shoulder 71 on the folding device 55c. Upon the movement of the web 50b from the position shown in FIG. 20 to that shown in FIG. 21, the web leaves the folding device 55d and reaches its fully interfolded position.

Each successive web is interfolded into the stack in similar fashion as it moves along three succeeding folding devices. The folding devices are positioned in close proximity with one another along the path of the stack. In addition to its other advantages, the use of three folding devices to complete the interfolding of a given web insures that the edge portions of the web move along gradually curving paths without abrupt changes in direction, with the result that extremely smooth folds are produced with a minimum of wrinkles and creases in the webs.

THE MACHINE SUPPLY ROLLS AND CORE ASSEMBLIES

Referring to FIG. 26, the tissue or other sheet material from which the webs 50 are formed is fed to the various folding devices 55 from a series of supply rolls 90. One of the rolls 90 is provided for each group of four folding devices 55, and the material from each roll is slit, in a manner to be more fully described hereinafter, into four separate webs which are led to the individual folding devices.

Each of the supply rolls 90 is supported between a pair of horizontal beams 92 and 93 (FIG. 28). The beams 92 and 93 are mounted intermediate their ends on upright columns 94 and angularly disposed braces 95. The braces 95 extend from the lower ends of the columns 94 to a group of posts 96 which form portions of the frame 97 of the machine.

A back-up roll 98 is disposed immediately adjacent the supply roll 90 in position to be moved to an operative location on the machine when the material on the supply roll is exhausted. The back-up roll 98 is carried by a cart 100 having two horizontal beams 101 and 102 which are arranged to mate with the corresponding beams 92 and 93 on the machine. The beams 101 and 102 are each provided with a tongue 103 which abuts the adjacent beam 92 or 93 to locate the cart 100 in position.

The supply rolls 90 and the back-up rolls 98 include the usual paperboard cores 104. Removably mounted within each core is an expandable core assembly or chuck 105. As best shown in FIG. 27, each of the chucks 105 includes a central shaft 106 surrounded by a sleeve 107 which is rotatable with respect to the shaft. The sleeve 107 is provided with bearings 108 which serve to maintain the sleeve in spaced relationship with the shaft 106.

Affixed to the opposite ends of the sleeve 107 are generally disk-shaped wheels 110 and 111. Inflatable tubes 112 and 113 of rubber or other resilient material are respectively mounted on the wheels 110 and 111. The tube 112 communicates with a conventional air inlet 115 through a four-way connection 116, and the tube 113 similarly communicates with an air inlet 117 through a four-way connection 118. The inlets 115 and 117 are disposed at opposite ends of the chuck 105 in locations which are readily accessible to a suitable air hose (not shown). The connections 116 and 118 are provided with normally closed vent valves 120 and 121, respectively. These valves are located immediately adjacent the corresponding inlet 115 and 117. The connections 116 and 118 communicate with each other through a conduit 122 which is located within the rotatable sleeve 107.

The chuck 105 is manually inserted into one end of the core 104 in a deflated condition and may be controlled entirely from that end of the core. When the chuck 105 is in position, air is supplied to the tubes 112 and 113 through one of the inlets 115 or 117. Upon the admission of air into the inlet 115, for example, the air flows through the connection 116 to the tube 112 and also along the conduit 122 and the connection 118 to the tube 113. As the tubes 112 and 113 are inflated, they bear against the inner cylindrical surface of the core 104 to rigidly hold the tubes, the wheels 110 and 111, and the sleeve 107 within the core and to maintain the shaft 106 in coaxial relationship therewith. The shaft 106 is free to rotate relative to the core 104 and the surrounding roll, however, to facilitate the feeding of the material on the roll to the machine.

To remove the chuck 105 from the core 104, either of the vent valves 120 or 121 is actuated to release the air within the tubes 112 and 113. For example, upon the opening of the valve 120 at the left end of the chuck 105, as viewed in FIG. 27, the air within the tube 112 is exhausted through the connection 116 and the valve 120, while the air within the tube 113 is exhausted through the connection 118, the conduit 122, the connection 116 and the valve. Upon the deflation of the tubes 112 and 113, the chuck 105 is manually pulled from one end of the core. The arrangement is such that both the inflation and deflation of the tubes 112 and 113, as well as the insertion and removal of the chuck 105, may be handled from the same end of the core, and there is no need for the operator to move around the roll from one end of the core to the other in order to perform these operations.

The chuck shafts 106 for the supply rolls 90 rest on the horizontal beams 92 and 93, where they are located in position by a series of stops 125. The stops 125 are affixed to the beams intermediate the upstanding columns 94 and the inner ends of the beams.

Pivotally supported beneath the inner ends of each of the beams 92 and 93 is an angularly disposed arm 127. In its normal position (the position shown in full lines in FIG. 26), the upper end of the arm 127 abuts the inner end of the corresponding beam, and the arm forms an acute angle with respect to the horizontal which preferably is not greater than about 80.degree. and illustratively is about 75.degree.. The arm is movable from this position to the substantially horizontal position shown in dotted lines. The upper end of the arm is provided with a notch 128. A coil spring 130 and a shock absorber 131 are interposed between each arm and the adjacent brace 95.

When the tissue on the supply roll 90 becomes exhausted, the core 104 and the chuck 105 therein are moved over the stops 125 and are rolled to the inner ends of the horizontal beams 92 and 93. The chuck shaft 106 is received within the notches 128 on the pivotally mounted arms 127. The angular disposition of the arms 127 is such that the weight of the core 104 and the chuck 105 causes the arms to automatically move from their full line position to the position shown in dotted lines (the position shown in FIG. 30). The movement of the arms 127 is resisted by the springs 130 and the shock absorbers 131, with the result that the arms pivot smoothly to their dotted line position.

As the arms 127 reach their new position, the core 104 and the chuck 105 roll off the outer ends of the arms onto a belt-type conveyor 132. The coil springs 130 thereupon return the arms 127 to their initial position in contact with the beams 92 and 93. The conveyor 132 extends from one end of the machine to the other in a direction parallel to the direction of the tissue stack 51 and is effective to carry the spent cores to a central location at one end of the machine. The chucks 105 within the cores are then removed by actuating either of the vent valves 120 (FIG. 27), and the chuck is inserted into the core for a fresh roll in the manner described heretofore.

THE ROLL DRIVE MECHANISMS

Each of the supply rolls 90 is independently driven by a drive mechanism indicated generally at 135. The mechanisms 135 are controlled by a common shaft 136 rotatably mounted on cross ties 137 which form portions of the main frame 97 of the machine. As best shown in FIG. 30, a series of sprockets 138 is affixed to the shaft 136, the number of sprockets corresponding to the number of rolls to be driven. Each of the sprockets 138 is connected by a drive chain 139 to a rotation reversing box 140, and the box 140 in turn drives a variable speed pulley 141 which is adjustable to change the speed of the roll drive. The pulley 141 is connected to a second pulley 142 by a belt 143. The box 140 and the pulley 141 are supported by the cross tie 137, while the pulley 142 is disposed immediately beneath the cross tie adjacent the upstanding post 96.

An electrically controlled clutch 145 interconnects the pulley 142 and a coaxial pulley 146. The pulley 146 is mounted on a shaft 148 for rotation about a fixed axis. Pivotally connected to the shaft 148 is one end of a generally horizontal frame 150 which extends outwardly over the corresponding supply roll 90. A drive belt 152 extends around the pulley 146 and a second pulley 153 rotatably carried at the outer end of the frame 150.

The drive shaft 136 is continuously rotated in a counterclockwise direction, as viewed in FIGS. 26 and 30, by a variable speed drive 155 (FIG. 28) connected to an electric motor 156. As the shaft 136 rotates, the sprocket 138 and the chain 139 likewise are driven in a counterclockwise direction, and the direction of rotation is reversed by the box 140 to produce clockwise movement of the pulleys 141, 142, 146 and 153. The drive belt 152 similarly rotates in a clockwise direction, and the lower surface of the belt bears against the periphery of the roll 90 to continuously rotate the roll counterclockwise and thus feed the sheet material on the roll to the machine. In the event of a break in the material on one of the rolls, a limit switch (not visible in the drawings) may be provided to deenergize the corresponding clutch 145 and thus interrupt the drive for that roll.

The weight of the frame 150 on the supply roll 90 is counterbalanced by a pneumatic cylinder 158 connected between the frame and the upper portion of the post 96. As the diameter of the supply roll 90 decreases during the withdrawal of the sheet material, the frame 150 pivots about the axis of of the shaft 148 to maintain the belt 152 in driving contact with the periphery of the roll. When the supply of material on the roll is exhausted, the frame 150 is moved to its uppermost position by the cylinder 158.

The arrangement is such that the drive mechanism 135 for each of the supply rolls 90 maintains the peripheral speed of the roll substantially constant irrespective of the roll's diameter. The roll speed is synchronized with the linear speed of the stack of webs and with the speed of the tissue slitting assemblies in a manner that will become more fully apparent hereinafter.

THE TISSUE SLITTING ASSEMBLIES

Mounted on every third cross tie 137 is a jack shaft 160. The shafts 160 are in coaxial relationship with each other and extend in a direction parallel to the direction of movement of the tissue stack 51. Each stack is continuously rotated in a counterclockwise direction, as viewed in FIG. 30, by the main drive shaft 136. The shafts 136 and 160 are interconnected by a belt 162, a variable speed pulley 163 and a pulley 164.

A sprocket 165 is carried by each of the jack shafts 160. The sprocket 165 drives a chain 166 which extends around a second sprocket 167 on an anvil shaft 168. One of the shafts 168 is provided for each jack shaft 160, and the shafts 168 are journaled in suitable bearings immediately beneath the cross ties 137. As best shown in FIG. 28, each of the shafts 168 extends between three of the ties 137, there being one shaft for every three supply rolls 90 on the machine. Three anvil rollers 170 are affixed to each shaft 168, with one roller being provided between each pair of adjacent ties 137. There is thus one of the rollers 170 for each of the supply rolls 90.

Carried by the cross ties 137 immediately adjacent the anvil shafts 168 is a slitter shaft 172. The shaft 172 is supported by appropriate pillow blocks 173 (FIG. 30) affixed to each cross tie, and the shaft extends in a direction parallel to the shafts 160 and 168 and the stack 51. Successive groups of three slitting disks 175, 176 and 177 are affixed at intervals along the shaft 172. Each of these groups is disposed between adjacent cross ties 137 such that the disks bear against the corresponding anvil roller 170.

The tissue or other sheet material on each supply roll 90 is led from the roll around a direction changing roll 180. The roll 180 is supported adjacent the post 96 and directs the tissue upwardly toward the cross ties 137. The tissue then passes over a bowed rod 181 and around a roller 182. The rod 181 has a smoothing effect as the tissue moves thereover.

The incoming tissue then moves around the anvil roller 170. The roller 170 is continuously rotated in a counterclockwise direction, as viewed in FIG. 30, to provide an additional independent drive for the tissue. The rate of feed is adjustable by controlling the speed of the variable speed pulleys 163. The three disks 175, 176 and 177 adjacent the roller 170 serve to slit the tissue into four equal-width webs, such as the webs 50a, 50b, 50c and 50d shown in FIGS. 14 and 15. The webs thereupon move around a bowed smoothing roller 184 and an additional roller 185 prior to being received by the individual guide bars 74 adjacent the folding devices 55.

It will thus be apparent that the sheet material from each of the supply rolls 90 is divided into four separate webs by the slitting assembly including the slitting disks 175, 176 and 177 and the cooperating anvil roller 170. The number of supply rolls on the machine is only one-fourth the number of webs. With this arrangement, the monitoring and replacement of the rolls is greatly facilitated.

THE STACK CONVEYOR MECHANISM

The various folding devices 55 and the adjacent guide bars 74 are mounted in spaced relationship with each other on a longitudinal table 190. As best shown in FIGS. 29, 31 and 32, the table 190 includes a centrally located longitudinal opening 191 which is provided with a series of depending U-shaped members 192. The legs of each of the members 192 are spaced by a distance approximately equal to the width of the tissue stack 51. An elongated plate 195 extends along the length of the stack between the legs of the members 192, and the plate and the legs serve to partially confine the interfolded webs in the stack as they move along their feed path. The plate 195 is disposed in a substantially horizontal plane but is provided with a slight downward slope toward the outfeed end of the machine to accomodate the increasing thickness of the stack as additional webs are interfolded therein.

The upper reach 196 of a conveyor belt 197 is arranged to ride on the plate 195 between the legs of the U-shaped members 192. At the outfeed end of the machine (the end shown in FIG. 31), the reach 196 passes over supporting rollers 198 and 199 and then around a drive roller 200. The belt 197 follows a closed path, and its lower reach 201 is directed beneath the table 190 by a series of guide rollers 203 and steadying rollers 204. The reach 201 also is directed around one or more pairs of tensioning rollers 206 and 207 which are adjustable in the usual manner to insure proper tension in the belt.

At spaced intervals along the length of the machine, the lower reach 201 of the conveyor belt 197 passes around groups of four direction changing rollers 210, 211, 212 and 213, only one of these groups being shown in FIGS. 31 and 32. The rollers 210 direct the lower reach 201 upwardly toward the table 190, the rollers 211 direct the reach horizontally immediately beneath the table, and the rollers 212 and 213 return the reach to its initial path. The arrangement is such that successive openings 215 are provided beneath the table along the length of the machine, thus permitting the machine operators to quickly and easily move from one side of the stack to the other.

Pivotally mounted adjacent the outfeed end of the machine is a generally horizontal frame 220. The frame 220 is disposed a short distance above the conveyor belt 197 and illustratively may be formed from two spaced channels. A shaft 221 is carried at one end of the frame 220 for rotation about a fixed axis, while a second shaft 222 is carried at the opposite end (the outfeed end) of the frame. The shafts 221 and 222 respectively support rollers 224 and 225 which are provided with a belt 226.

The lower reach of the belt 226 rests on the upper portion of the tissue stack 51 even for stacks which vary widely in height. Referring to FIG. 33, for example, there is shown a schematic representation of the belt 226 in the position it normally would occupy for a full count stack of two-ply tissue of normal height. In cases in which a smaller number of two-ply webs are being interfolded to produce a stack of reduced height, the frame 220 and the belt 226 automatically pivot in a clockwise direction about the axis of the shaft 221 to the position shown in FIG. 34. During the interfolding of a full count stack of single-ply tissue, the belt pivots even further to the position shown in FIG. 35. With this arrangement, the various stacks are uniformly fed from between the belt 226 and the drive belt 197 onto the outfeed conveyor 228 of the machine.

MACHINE OPERATION

Prior to the initiation of the interfolding operation, the various supply rolls 90 (FIG. 30) are located in their operative positions (the positions shown), and the sheet material from each roll is threaded around the roller 180, past the bowed rod 181 and around the roller 182. The material is then directed between the anvil roller 170 and the slitting disks 175, 176 and 177 to divide the material into individual webs. The webs are led around the rollers 184 and 185, the folding bars 74, the guide rollers 60 (FIG. 3) and along the folding surfaces 56 and 57 on the folding devices 55 to the conveyor belt 197.

Upon energization of the motor 156 (FIG. 28), the drive shaft 136 is rotated to drive the roll belts 152 and the anvil rollers 170 in the manner described heretofore. The belts 152 rotate the supply rolls 90 in a counterclockwise direction, as viewed in FIGS. 26 and 30, to feed the sheet material toward the folding devices 55.

The drive shaft 136 is connected through a chain 230 to a gear box 232 (FIG. 31). The box 232 is provided with a sprocket 233 which drives a chain 234 connected to a similar sprocket 235 for the roller 200. As the shaft 136 rotates, it drives the roller 200 to rotate the conveyor belt 197 in a clockwise direction, as viewed in FIGS. 31 and 32, in synchronism with the roll drive belts 152 and the anvil rollers 170. The belt 197 draws the webs past the folding devices 55 to form the longitudinal folds, and the belt advances the thus interfolded stack of webs toward the outfeed end of the machine. To insure a constant relative speed between the periphery of each of the rolls 90, the anvil rollers 170 and the interfolded webs on the belt 197, the variable speed pulleys 141 and 163 may be adjusted to produce the desired speed correction.

With this arrangement, the power for rotating the supply rolls 90 is derived from the drive mechanisms 135, the power for slitting the sheet material is derived from the anvil rollers 170, and the power for moving the webs past the folding devices 55 and along the path of the stack 51 is derived from the belt 197. Periodic increments of energy are thus added to the tissue at three separate points along its path of travel, and the applied energy at each point is independently adjustable in accordance with the parameters of the particular tissue folding operation. As a result, the webs flow smoothly onto the infeed surfaces 65 (FIG. 3) of the folding devices 55 at a uniform speed. In the manner described heretofore, the shallow troughs 53 are formed in the webs as a result of the pairs of triangular surfaces 66 and 67, the webs change direction and the troughs are turned inside out to form the troughs 54, and these latter troughs are gradually closed by the folding shoulders 56 and 57 and the guide members 70 as the webs move past three successive folding devices.

When the machine is shut down, the roll drive mechanisms 135, the anvil rollers 170 and the conveyor belt 197 each act as a brake on the rapidly moving tissue. The arrangement is such that the operation of the machine is arrested without substantial slackness or breakage of the tissue.

THE FOLDING DEVICES OF FIG. 36

FIG. 36 is illustrative of two folding devices 240 and 241 which may be employed to interfold adjacent webs 50 into the stack 51. The folding device 240 is arranged to form a right-hand fold, such as the fold in the web 50f of FIG. 37, while the device 241 is arranged to form a left-hand fold, as shown by the fold in the web 50g. Functionally, the devices 240 and 241 are similar in some respects to the folding devices 55c and 55d (FIG. 3) described heretofore. Thus, each of the devices 240 and 241 includes a pair of gradually curving folding shoulders 243 and 244 which respectively receive the longitudinal edge portions of the web and initiate the formation of the fold. The shoulders 243 and 244 merge into comparatively flat surfaces which intersect at an acute angle. Contrary to the folding devices 55, however, the slot-shaped opening between these surfaces has been omitted.

Affixed to the lower portion of each of the folding devices 240 and 241 is a web guide member 246. The guide member 246 is provided with a shoulder 247 thereon of a configuration which is generally similar to that of the shoulder 71 (FIG. 13) of the guide member 70. The shoulder 247 on each folding device receives a partially folded web from the immediately preceding device and maintains the edge portions of the web in spaced-apart relationship with each other to prevent the completion of the fold.

Extending upwardly from each of the folding devices 243 and 244 is a curved infeed plate 250. The plate 250 and its folding device are integrally formed from a single piece of material and are suitably supported above the path of the stack of webs by a mounting bracket 251. A guide roller 252 is rotatably mounted at the upper end of each of the plates 250. The axis of each roller 252 extends horizontally in a direction parallel to the direction of the stack, as does the upper edge of the plate 250. The plate 250 curves downwardly from the roller 252 and meets the surfaces adjacent the shoulders 243 and 244 in a smooth continuous bend.

The various webs 50 to be interfolded are led directly to the guide rollers 252 for the folding devices 240 and 241, no folding bars or other direction changing means being employed. The webs move in a vertically downward direction along the plates 250 and follow the gradually curving paths of the plates to the folding shoulders 243 and 244. As the webs move along the shoulders 243 and 244, the formation of a V-shaped trough is initiated in each web. Upon movement of each web to the immediately succeeding folding device, the shoulder 247 thereon enters the trough and maintains the edge portions of the web in spaced-apart relationship with each other as an edge portion of the next web is laid down. In a manner similar to that described above, the edge portions continue in their spaced-apart relationship until after the web passes the next succeeding folding device, at which point the web becomes fully interfolded into the stack.

THE FOLDING DEVICE OF FIG. 38

In order to adapt the machine for the formation of Z-shaped folds, there is provided an alternative folding device indicated generally at 255. Ajacent folding devices 255 are substantially identical to each other, there being no alternate left-hand and right-hand devices as in the previously described embodiments. Each device 255 is supported on the machine by an upstanding post 256 and has a main body portion 257 which is substantially similar to the folding device 240 of FIG. 36. The portion 257 includes a pair of gradually curving folding shoulders 258 and 259 which are oriented along the feed path in the manner shown by the folding shoulders 58 and 59 on the right-hand folding device 55c (FIG. 3) and by the folding shoulders 243 and 244 on the device 240. The shoulders 258 and 259 merge into comparatively flat surfaces which intersect one another and are contiguous with a gradually curving infeed plate 260 extending upwardly therefrom.

Mounted in close juxtaposition with the body portion 257 is a generally triangular plate 262. The plate 262 is maintained in spaced-apart relationship with the upper surface 264 of the portion 257 to define a gradually curving slot 265 therebetween. The slot 265 slopes downwardly adjacent the infeed side of the folding device 255 at an acute angle with respect to the path of the stack 271, and the slot then curves in a direction almost parallel to that of the stack. The outfeed end of the slot 265 is disposed a short distance above the folding shoulders 258 and 259.

The folding device 255 may be utilized to form either standard or interlocking Z-shaped folds in the webs. FIG. 39, for example, is illustrative of a group of standard Z-fold webs 270 as they are interfolded into a stack 271. Each of the webs 270 includes a pair of longitudinally extending edge portions, such as the edge portions 270a1 and 270a2 of the web 270a, and also an intermediate longitudinal portion 270a3. The webs are interfolded with the lowermost edge portion of each web interposed between the intermediate and upper edge portions of the immediately preceding web. As is well known, interlocking Z-fold webs are arranged in similar fashion but with the lowermost edge portion of each web positioned between the intermediate edge portion of the immediately preceding web and the uppermost edge portion of the next preceding web.

The webs 270 to be interfolded are led to the successive folding devices 255 from above and are received by the infeed plates 260. As the web 270a, for example, moves along the gradually curving surface of the plate 260, the edge portion 270a2 enters the slot 265 between the main body portion 257 of the folding device and the plate 262 thereabove. The edge portion 270a2 is carried along the surface 264, while the intermediate portion 270a3 remains in contact with the curved surface of the plate 260, thus initiating the formation of a trough for the upper of the two folds in the web. Upon continued movement of the web 270a along the folding device, the edge portion 270a1 and the intermediate portion 270a3 come into respective contact with the folding shoulders 259 and 258 to initiate a trough for the lower fold in the web.

Each of the troughs in the web 270a is maintained in an open condition during the movement of the web along the immediately succeeding folding device 255 and the second succeeding folding device. The immediately succeeding device is effective to position the lowermost edge portion 270b1 of the web 270b between the edge portion 270a2 and the intermediate portion 270a3 of the web 270 in the manner shown in FIG. 39. The second succeeding device then proceeds to complete the folds in the web 270a. The successive webs are interfolded in a similar manner to provide a stack of Z-folded webs which is cut into box-size lengths for packaging and delivery to the consumer.

FIGS. 40 AND 41

Referring to FIGS. 40 and 41 of the drawings, there is shown a portion of an alternate conveyor mechanism that is particularly useful in advancing and guiding the continuously moving stack of webs along its feed path. The mechanism includes a series of tubular members 300 of rectangular cross-section which are positioned in longitudinal alignment with each other along the path of the stack. A plurality of plate-shaped fingers 302 and 303 protrude from the respective ends of each of the members 300. The fingers 302 and 303 at the adjacent ends of the members 300 are interleaved and are provided with oblong apertures 304 which accomodate an interconnecting pivot pin 305 to permit relative movement between the members. The upper surfaces of the members support a web conveyor belt 306 in a manner similar to that described heretofore with respect to the belt 197 (FIG. 29).

Carried adjacent one end of each of the tubular members 300 is a laterally extending pin 310. The pin 310 is maintained in pivotal relationship with a jack 312. A series of the jacks 312, one for each of the members 300, is disposed at spaced locations along the length of the conveyor, and each jack may be raised or lowered through the use of a manually operable crank 314.

The jacks 312 permit the rapid and straightforward adjustment of the height of the conveyor belt 306 in accordance with the particular type of tissue and number of sheets being interfolded. Upon movement of the crank 314, the pin 310 moves upwardly or downwardly to vary the level of the pivot pin 305 between the adjacent members 300. As the pin 305 changes position, the adjacent members pivot about the axis of the pin to provide a precise adjustment of the level of the belt 306. Each section of the web conveyor similarly is adjusted such that the level of the belt is maintained in precise correspondence with the parameters of the particular tissue folding operation.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention.

Claims

What is claimed is:

1. In apparatus for longitudinally interfolding a plurality of webs and for advancing the interfolded webs in a continuously moving stack along a feed path, in combination:

a plurality of folding devices mounted in spaced relationship with each other along the feed path, each of said folding devices having an infeed surface and an outfeed surface extending from and continuous with said infeed surface in the direction of movement of the stack along the feed path, said outfeed surface including a pair of gradually curved diverging folding shoulders, at least one of said folding shoulders extending at an angle from a portion of the infeed surface adjacent the feed path obliquely across at least a portion of the feed path, and outfeed surface portions extending laterally from said folding shoulders defining a concave surface, as viewed from the preceding folding device, between the folding shoulders for concavely folding the portion of a web drawn therebetween, said folding devices being disposed along the feed path so that the concave outfeed surface portion of each folding device can receive the portion of the folded web from the preceding folding device to be interfolded with the web supplied to said folding device;

means associated with each of said folding devices for guiding the portion of the folded web from the preceding folding device to be interfolded with the web supplied to said folding device into the concave outfeed surface portion of said folding device so that the folding shoulder which extends across the feed path is interposed between said portion of the folded web to be interfolded and the remainder of said folded web opposite said portion;

means for supplying a web to each of the folding devices; and

means for drawing the web supplied to each of the folding devices over the infeed and outfeed surfaces of said folding device and into the stack so that said web is folded concavely around the portion of the folded web from the preceding folding device guided into the concave outfeed surface portion of said folding device as said web passes the outfeed surface of said folding device and so that a portion of said web on the side of the fold adjacent the interposed folding shoulder is gradually interposed between the folded surfaces of the web from the preceding folding device by said interposed folding shoulder to interfold said web and the web from the preceding folding device, and a portion of the web on the other side of the fold is positioned by the other folding shoulder for guiding into the concave outfeed surface portion of the succeeding folding device.

2. The apparatus defined in claim 1 wherein the infeed surface of each folding device is substantially perpendicular to the feed path.

3. The apparatus defined in claim 2 wherein the infeed surface of each folding device is substantially triangular.

4. The apparatus defined in claim 44 wherein the folding shoulders of each folding device extend from the region of a corner of the triangular infeed surface of said folding device.

5. The apparatus defined in claim 1 wherein said means for supplying comprises:

a plurlaity of supply rolls of sheet meaterial;

means for longitudinally slitting said sheet material from said supply rolls to produce a plurality of webs; and

means for respectively directing said webs to said folding devices.

6. The apparatus defined in claim 1 wherein said means for drawing comprises conveyor means for supporting the stack of interfolded webs and for advancing said stack along said feed path.

7. The apparatus defined in claim 6 further comprising means for adjusting the position of said conveyor relative to said folding devices in accordance with the number and thickness of webs in said stack.

8. The apparatus defined in claim 1 wherein the outfeed surface of each of said folding devices further includes an extension of the folding shoulder which is not interposed between portions of the folded web from the preceding folding device for longitudinally creasing the portion of the web supplied to said folding device adjacent said folding shoulder extension in the opposite direction from said concave fold and wherein said apparatus further includes means associated with each of said folding devices and disposed in spaced relationship therewith for defining an opening therebetween for receiving the portion of the web extension from the crease formed by said folding shoulder extension in the direction away frm said concave fold and for further positioning the received portion of the web for guiding into the concave outfeed surface portion of the succeeding folding device.

9. In apparatus for longitudinally interfolding a plurality of webs and for advancing the interfolded webs in a continuously moving stack along a feed path, in combination:

a plurality of folding devices mounted in spaced relationship with each other on alternate sides of the feed path, each of said folding devices having an infeed surface and an outfeed surface extending from and continuous with said infeed surface in the direction of movement of the stack along the feed path, said outfeed surface including a pair of gradually curved diverging folding shoulders extending from a portion of the infeed surface adjacent the feed path obliquely across at least a portion of the feed path, and outfeed surface portions extending laterally from said folding shoulders, said outfeed surface portions and folding shoulders respectively defining convex surfaces as viewed from the preceding folding device, outside the folding shoulders and a concave surface between the folding shoulders, said outfeed surface being substantially convex adjacent the infeed surface and becoming substantially concave as the folding shoulders diverge toward the outfeed end of the folding device, for forming a convex longitudinal trough in a web drawn over the outfeed surface of the folding device and for gradually inverting said trough as the web is drawn over the folding shoulders and into the concave outfeed surface portion between the folding shoulders, the outfeed surface portions defining the bottom of the concave outfeed surface being sufficiently close together to concavely crease the portion of the web drawn therebetween;

means associated with each of said folding devices for preventing the inverted trough in the web from the preceding folding device from closing and for guiding one edge of the web from the preceding folding device into the concave outfeed portion of said folding device so that one of the folding shoulders of said folding device projects at least partially into said inverted trough for interfolding said edge with the web supplied to said folding device;

means for supplying a web to each of the folding devices; and

conveyor means for drawing the web supplied to each of the folding devices over the infeed and outfeed surfaces of said folding device and into the stack so that said web is creased concavely around the edge of the web from the preceding folding device guided into the concave outfeed surface portion of said folding device as said web passes the outfeed surface of said folding device, and so that at least a portion of the web on the side of said crease adjacent the folding shoulder projecting into the inverted trough in the web from the preceding folding device is gradually introduced into said inverted trough by said projecting folding shoulder and is thereby interfolded with the web from said preceding folding device.

10. The apparatus defined in claim 9 wherein the infeed surface of each folding device is substantially perpendicular to the feed path.

11. The apparatus defined in claim 10 wherein the infeed surface of each folding device is substantially triangular.

12. The apparatus defined in claim 11 wherein the folding shoulders of each folding device extend from the region of a corner of the triangular infeed surface of said folding device.

13. The apparatus defined in claim 12 wherein the outfeed surface portions of each of said folding devices defining said convex surface extend from the two sides of the triangular infeed surface adjacent the region of said corner of the triangular infeed surface of said folding device.

14. The apparatus defined in claim 13 wherein the periphery of the triangular infeed surface of each of said folding devices is indented in the region of said corner of said triangular surface to define a keyhole-shaped aperature in said infeed surface between said folding shoulders for initiating formation of the inverted trough in the web drawn over said folding device.

15. The apparatus defined in claim 9 wherein said means for supplying comprises:

a plurality of supply rolls of sheet material;

means for longitudinally slitting said sheet material from said supply rolls to produce a plurality of webs; and

means for respectively directing said webs to said folding devices.

16. The method of longitudinally interfolding a plurality of webs to produce a stack of interfolded webs moving continuously along a feed path comprising the steps of:

respectively guiding said webs to a plurality of locations on alternate sides of said feed path;

forming a convex longitudinal trough in each of said webs as it is guided to said feed path, said trough being convex as viewed from the preceding web approaching the feed path and having a longitudinal axis which meets the feed path at an acute angle;

gradually inverting a medial portion of the convex trough in each of said webs as said web merges with the stack of webs to form a concave longitudinal trough in said web;

guiding a first edge portion of the concave trough in each of said webs into the concave trough of the preceding web to interfold said web with the preceding web;

guiding the remaining edge portion of the concave trough in each of said webs into the concave trough of the succeeding web to permit the succeeding web to be interfolded with said web; and

closing the concave trough in each of said webs following completion of the two immediately preceding steps for said web.

17. The method of longitudinally interfolding a plurality of webs to produce a stack of interfolded webs moving continuously along a feed path comprising the steps of:

respectively guiding said webs to a plurality of locations along one side of said feed path;

forming a convex longitudinal trough in each of said webs as it is guided to said feed path, said trough being convexly bowed out toward one lateral side of the feed path as viewed from the preceding web approaching the feed path and having a longitudinal axis which meets the feed path at an acute angle;

gradually inverting a portion of the convex trough in each of said webs as said web merges with the stack of webs to form a concavely bowed trough facing said one lateral side of the feed path in a portion of said web while maintaining a parallel convex trough in the lateral portion of said web adjacent the concave trough;

guiding an edge portion of the concave trough in each of said webs into the convex trough of the preceding web to interfold said web with the preceding web;

guiding an edge portion of the convex trough in each of said webs into the concave trough of the succeeding web to permit the succeeding web to be interfolded with said web; and

closing the concave and convex troughs in each of said webs following completion of the two immediately preceding steps for said web.