US3919019A

US3919019A - Method of heat-sealing superimposed layers of sheet material

Info

Publication number: US3919019A
Application number: US407070A
Authority: US
Inventors: Winfried Bottcher
Original assignee: POLYGRAPH LEIPZIG KOM FUWE POL
Current assignee: POLYGRAPH LEIPZIG KOM FUWE POL; VEB POLYGRAPH LEIPZIG KOMBINAT FUWE POLYGRAPHISCHE MASCHINEN und AUSRUESTUNGEN
Priority date: 1971-07-20
Filing date: 1973-10-17
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A stack of superimposed sheet material is advanced continuously in a predetermined path, and successive lengths of thread are advanced to it and pressed against one major side of the advancing stack for movement therewith. Spaced end portions of each length of thread are pushed through the stack so as to project in part from the opposite major side of the same and these parts are then deflected into engagement with this opposite major side and heat-sealed thereto, all during continuous advancement of the stack.

Description

United States Patent n91 Bottcher METHOD OF HEAT-SEALING SLPERIMPOSED LAYERS OF SHEET MATERIAL [75] Inventor: Winfried Bottcher, Leipzig.

Germany [73] Assignee: Veb Polygraph Leipzig Kombinat Fuwe Polygraphische Maschinen und Ausruestungen, Liepzig. German 3' Filed: Oct. 17. 1973 Appl, No: 407,070

Related US. Application Data {63] Continuation-impart of Ser. No. l64.307. July 20.

i97l. abandoned.

[52] US. Cl. 156/91; ill/21; 156/229 [5 l] Int. Cl. B32B 7/08 [58] Field of Search 156/91. 92. 93. M8. E79.

156/229.52l.5l3.475;227/71.8l; llZ/Zl. 79 R; 270/37. 53

[56] References Cited UNITED STATES PATENTS 154L367 Z/IJSI Kitcat I 12/7) R [451 Nov. 11, 1975 3.319.863 5/[967 Dritz Z27/7l 3.514.027 5/l97t) 227M! 3.6|U.U87 lU/l97l 227/7l X 3.653.570 4/1972 237/81 3.654.004 4/[972 Piesche I56/9l Primary E.\'umi'nerCharles E. Van Horn Assistun! E\'am[nerMichael Ball Attorney. Age/u, or Finn-Michael S. Striker [57] ABSTRACT A stack of superimposed sheet material is advanced continuously in a predetermined path. and successive lengths of thread are advanced to it and pressed against one major side of the advancing stack for movement therewith. Spaced end portions of each length of thread are pushed through the stack so as to project in part from the opposite major side of the same and these parts are then deflected into engagement with this opposite major side and heat-sealed thereto. all during continuous advancement of the stack.

4 Claims. 8 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 015 3,919,019

INY/ENTOR. w/Nm/L'D BUTTCHE R US. Patent Nov. 11, 1975 Sheet 2 of5 3,919,019

FIG. 2

INV NTOR. l wm/m/eb B TTCHER .dfudhd ATTORNEY US. Patent Nov. 11, 1975 Sheet 3 of5 3,919,019

FIG. 3

INVENTOR.

WWW/ED B07704 FR BY US. Patent Nov. 11, 1975 Sheet 4 of5 3,919,019

INVENTOR. Wm FRIEJ) BTTCk/[R TT T l Tl .N trukc o hp 411M.

US. Patent Nov. 11, 1975 Sheet50f5 3,919,019

FIG. 7

FIG. 8

INY/ENTOR. W/NFR/ED BOTTCHER //i'u J $44 A METHOD OF HEAT-SEALING SUPERIMPOSED LAYERS F SHEET MATERIAL The present application is a continuation-in-part of my earlier application Ser. No. 164,307, filed July 20, 1971 and now abandoned.

CROSS-REFERENCE TO RELATED APPLICATIONS Related applications Ser. Nos. 213,255 (now US. Pat. No. 3,763,798) and 214,232 (now US. Pat. No. 3,763,799), have been filed in my name on Dec. 29, 1971, and Dec. 30, 1971, respectively, under the titles "Apparatus for Stitching Sheet Materials, and "Method for Connecting Superimposed Layers of Sheet Material and Apparatus for Carrying out the Method."

BACKGROUND OF THE INVENTION The present invention relates generally to the connecting of superimposed layers of sheet material to one another, and particularly to a method for effecting such a connection and to an apparatus for carrying out the method.

The invention is concerned with "binding" of books, brochures, pamphlets and the like, with the word "binding" here being used in its broadest sense to imply only the connection of superimposed sheet material layers to one another, a process which may or may not be followed (for instance if a book is involved) by providing a separate cover, a spine or the like.

In this broad binding" or connecting of superimposed sheet material layers, such as sheets of paper which may be printed or not, with one another it is known to either staple the layers or to stitch them with thread. The stitching with thread can be carried out in different ways, which may basically be subdivided into continuous stitching, that is in sewing as with a sewing machine, or in the formation of individual stitches each of which is composed of a single length of thread spaced end portions of which are pushed through the stack of superimposed sheet materials so that the stitch somewhat resembles a conventional stable, with the free parts which the pushed through being sealed to the opposite side of the stack as disclosed in the present invention is concerned in particular with this latter type of stitching. In the known approach to this type of stitching or thread-sealing it is known to effect such stitching of superimposed sheet materials and subsequently to fold the stack along the stitching line. The prior art as disclosed GDR Pat. No. 10,106, teaches that the stack is to be advanced in a direction at right angles to the line which is to be formed by stitching on the stack when the latter reaches a working station, and at the working station there is located a plurality of stitching arrangements corresponding in number to the number of stitches to be provided in the stack. When the stack is located beneath these stitching arrangements, which are located in a line coincident with the line of stitches to be formed in the stack, the latter is briefly arrested in its movement and the stitches are provided in it while it is stationary. Thereupon the now stitched stack is again advanced and usually moved to a folding station where it is folded along the line of stitches which have just been provided.

The self-evident disadvantage of this prior-art teaching is that the operation must be discontinuous because each stack of sheet materials must be arrested while the line of stitches is formed in it. Because of this the throughput capacity of an apparatus utilizing this priorart teaching is considerably limited with the result that it cannot be used either with high-speed supplying apparatus (such as rotary printing presses) or with highspeed user apparatuses. On the one hand the supply of stacks of material would arrive too fast to be handled, and on the other hand the supply of stitched stacks to a high-speed user apparatus would be too slow. Moreover, the technical requirements which must be fulfilled in this type of apparatus are out of all proportion to the economy of operation which can be achieved with it, especially because such apparatus requires as many stitching devices as stitches must be formed in each and every stack of sheet materials.

A further disadvantage is the fact that the technical complexity as well as the physical dimensions of these stitching devices make it impossible to locate them so closely together in a row that the stitches can be pro vided immediately consecutively, as is often desired.

According to a further prior-proposal made in US. Pat. No. 3,654,004, a rotary stitching device is provided which forms a row of stitches in the stack of sheet materials which is advanced in the direction in which the row is to be formed. In this prior-art device the sheet material or sheet materials move between a pair of rollers over one of which the thread required for forming the stitches is placed, which thread is to be cut into pieces of requisite length also called thread changes whose opposite ends are then pushed through the stack, to be secured thereto in known manner.

With the type of stitching here under discussion, it is a basic requirement that a length of thread of requisite elongation be cut off, engaged and maintained taut on a major surface of the sheet material or stack of sheet materials, until it is pushed by the needles of the stitching device through the sheet material. The needles are provided with substantially wedge-shaped recesses in their leading ends which are placed over the end portions of the thread and then push the end portions through the stack of sheet materials. Because of the necessity to hold each thread piece taut on a surface of the stack until its end portions are pushed through the latter, it is necessary that the thread supply arrangement and the needles, if both are to be utilized for forming stitches in continuously advancing stacks of sheet materials so that both devices must be mounted for rotation, be capable of rotating about the same axis. The thread supply device must withdraw the thread from a supply, such as a bobbin and must sever it into pieces of requisite lengths. This, of course, requires that a cutting device must be provided in addition. The thread supply device must be constructed as a hollow drum which on its outer periphery is provided with clamping devices and cutting devices for the thread, and inwardly must have journals for the needles which must always be moved radially with reference to a counter cylinder or roller, whereas in the interior of the hollow drum there must be provided control devices which effect the movement of the cutting device and the needles in a sense causing the latter to push the end portions of the thread increments through the stack. On the other hand it is necessary that the diameter of the hollow drum or roller be as small as possible be cause the number of thread holders and needles increases as the diameter of the drum increases, but this in turn is a requirement which contradicts with the necessity for having adequate space in the interior of the drum for the necessary control devices. The result in the prior art is a compromise according to which the thread supply device as well as the control devices are made as small as possible, but on the other hand are given a reasonable life expectancy and reliability consistent with the requirement that they be as small as possible.

Once the end portions of a respective thread piece have been pushed through the stack they will project in part beyond the opposite major surface thereof. These parts must then be deflected into engagement with this opposite major surface and must be sealed thereto, and usually the scaling is effected as heat sealing with the thread being a heat-bendable thread of known type, e.g. polyesters, cellulose triacetate, polyethylene, polyproprylene, polymiychloride and mixed polyesters. Such materials are, for example, disclosed in British Pat. No. 1,048,847 to which reference may be had for further details. The means for effecting the deflection and the bonding utilizes stationary instrumentalities over which the stack is moved.

The second-mentioned prior-art approach, utilizing a rotating thread supply arrangement and needles which are guided and controlled in it, permits a substantial increase in throughput over the first-mentioned arrangement. However the construction is complicated as pointed out above, and all components are located within a very small space, which facts not only facilitate breakdowns but make it exceedingly difficult to effect repairs when breakdowns do occur. All in all, the priorart device of the second type therefore does not meet the requirements made as to speed and reliability especially in continuously operating machines. In order to avoid a complete shut-down of such a machine it would be necessary to have at least two of the secondmentioned stitching devices which can operate in parallelism and of which one can take over while the other is being repaired. In addition it would be necessary to provide means for switching over the flow of sheet material stacks from one to the other of the stitching devices, depending upon which of them is operative at any given time. All of this of course is expensive and the loss of reliability is disadvantageous. [t is also found that the disadvantages mentioned above occur at the output side of printing machines utilizing such stitching arrangements, and it is further pointed out that the control devices for the thread severing device and for the needles are subject to rapid and considerable wear because of the movements involved, so that the advantage of being able to thread stitch a stack of sheet materials during continuous movement in accordance with the second-mentioned prior-art approach is almost or completely counteracted by these disadvantages.

SUMMARY OF THE INVENTION It is thus a general object of the present invention to overcome the disadvantages of the prior art.

More particularly it is an object of the present invention to provide an improved method of connecting su perimposed layers of sheet material which advance continuously in a predetermined path, which method is not possessed of these disadvantages.

in pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention resides in a method of sealing superimposed layers of sheet material which advance continuously in a predetermined path. This method comprises the steps of continuously advancing a stack of superimposed sheet materials in a predetermined path, and pressing a cut length of thread which forms a stretched thread clamp against one major side of the advancing stack for movement with the same. While the length of thread is held in place on the advancing stack, spaced end portions of the length of thread are pushed through the stack so as to project in part from the opposite major side thereof. The projecting parts are deflected into engagement with this opposite major side and sealed thereto during the continuous advancement of the stack in the path.

The deflecting and sealing effected by stationary instrumentalities or a single instrumentality, and it is advantageous according to a further concept of the invention that the stack is provided with openings during this advancement but before the end portions of the pieces of thread are pushed through the stack, so that subsequently these end portions can be pushed through the thus-provided openings. This is not, however, a prerequisite of the present invention and constitutes merely one advantageous aspect.

It will be appreciated that the present invention essentially differs from the aforedescribed prior art by pressing thread pieces of requisite length against a surface ofthe advancing sheet material stack, and moving these thread pieces with the advancing stack until they reach a device which pushes their spaced opposite end portions through the stack. Because of this, a physical and local separation of the thread supply and cutting device and of the device which actually effects stitching of the thread piece ends through the stack, can be readily obtained; this makes it possible to construct the various devices in such a manner that they will have optimum dimensions without influencing one another of interfering with one another. This avoids the necessity for excessive miniaturization and the concomitant disadvantage of ready susceptibility to breakdowns. More over, in an apparatus for carrying out the present method the various constituent components and devices can all be so mounted because of the space availability that any one device or component can be readily removed and replaced without interfering with or being interfered by other devices or components, and of course also being readily accessible.

As mentioned earlier, materials suitable for the thread lengths which are used as thread staples, are known from British Pat. No. l,048,857. They include polyesters and, cellulose triacetate as materials having a high melting point, and polyethylene, polypropylene, polymiylcloride and mixed polymers as materials having a low melting point.

It is important that the thread lengths be both relatively thin and flexible. because otherwise the back of a stack of sheets connected with the thread staples constituted by these thread lengths (e.g. the back of a book) will become excessively thick. To meet these requirements, the thread lengths are cut from a thread which is composed of a plurality of their filaments which may all be of one of the aforementioned heatsealable materials, or different filaments may be of different ones of these materials. However, only one or some of the filaments may be of such materials, and the remaining filaments of the thread may be non-scalable material, for instance cotton. The filaments may be spun together, twisted together or braided together. Thus. non-scalable filaments may surround a core of one or more heat-scalable filaments.

According to the present invention it is advantageous that an endless transporting device be provided which extends in parallelism at least in a portion of its path with a transporting device for the stack of superimposed sheet materials, with sections of the endless transporting device entering into recesses provided in the periphery ofa continuously rotating thread supply device whose periphery contacts and rolls on one major surface of the stack of sheet material. The sections thus enter into such recesses where they contact a thread piece of requisite length which spans the respective recess, pressing this thread piece against the one major surface of the stack and pulling it loose from engagement with the thread supply device during continued advancement of the endless transport device together with the stack. The transporting device is advantageously configurated as an endless chain which is mounted for movement in parallelism with the direction of advancement of the stack of sheet materials at a speed corresponding to the speed of advancement of the stack. The chain will have sections carrying pressure elements which contact the respective thread pieces pressing them against the one major surface of the stack and having a width or length in the longitudinal direction of the thread piece which is smaller than the distance between two cooperating needles of the subsequently arranged stitching device, which needles engage the opposite end portions of the thread piece and push it through the stack forming a thread clamp. The movement of the needles is so synchronized with the movement of the endless chain that the two needles will always push through the sheet material at the opposite ends of the respective pressing element, thereby contacting and pushing through the stack the spaced end portions of the thread piece which is located beneath and being held in place by the pressing element. The center portion of the clamp to be formed continues to be held during this process by the pressing element.

It is usual procedure that the stack of sheet material layers is positioned on a conveyor belt or the like by which it is advanced in its predetermined path. According to the present invention such a conveyor belt may utilize an upper and a lower conveyor which engage the stack between them in order to transport the stack without slippage. However, in place of the belts it is of course possible to use endless chains, just as only a lower belt may be provided for support of the stack whereas the function of the upper belt may be taken over by the endless chain whose pressing elements engage and hold the respective thread pieces. This is all the more readily possible because the endless chain is advanced at the same speed and in the same direction as the lower conveyor belt supporting the stack. Such use can be further facilitated by providing on the contact or pressing elements friction-promoting surfaces which should remain clean at all times and which contact the stack.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a somewhat diagrammatic side view of an apparatus according to the present invention as seen from line I-I of FIG. 2;

FIG. 2 is a top-plan view of FIG. 1;

FIG. 3 is a fragmentary end view, on an enlarged scale, of FIG. 1 as seen in the direction of the arrow A in FIG. 1;

FIG. 4 is a fragmentary enlarged detail view of the detail shown in the circle IV of FIG. I;

FIG. 5 is a fragmentary enlarged view of the detail shown in the circle V of FIG. 1;

FIG. 6 is a fragmentary enlarged view of the detail shown in the circle VI of FIG. 1;

FIG. 7 is a fragmentary plan view of an apparatus according to a further embodiment of the invention; and

FIG. 8 is a side view of the apparatus shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly the embodiment illustrated in FIGS. 1-6 it will be seen that the invention is described by way of example on hand of an arrangement or apparatus for stitching stacks of superimposed sheet materials which (irrespective of the previous treatment which they have received) are subsequently intended to be folded once more along the line of stitches which is formed on them. Thus, the output for instance of printing machines can be directly supplied to the novel apparatus, or it can undergo preliminary folding except for the final holding before it reaches the novel apparatus. It is emphasized. however, that the novel apparatus and method can also be utilized for stitching stacks of sheet materials which have already received the final fold but which must then, of course, be unfolded again and advanced on a proper support to the apparatus for stitching purposes.

Keeping this in mind, and now referring to FIG. 1, it will be seen that reference numeral 1 identifies two stacks of superimposed sheet materials which are to be continuously advanced in the direction of the arrow A, that is from the left towards the right in FIG. I. These stacks move between a lower conveyor belt 2 and a cooperating upper conveyor belt 5 between the juxtaposed runs of which the stacks 1 are engaged and advanced. The lower conveyor belt is composed of belt portions 20, 2b, 2c and 2d as shown in FIG. 3, which pass around axially parallel spaced rollers 3 and 4. The upper belt 5 is similarly constituted by belt sections 50, 5c and 5d which are trained about upper rollers 6 and 7 and which are respectively in contact with the corresponding belt sections 2a, 2c and 2d of the lower belt 2. Suitable drive means (not illustrated because conventional) are provided which drive the rollers 4 and 7 at identical circumferential speed but in mutually opposite direction (compare the arrows in FIG. I) so that the abutting runs of the belts 2 and 5 move in one and the same direction, namely towards the right in FIG. 1. Thus, the stacks l are transported between the belts 2 and 5 without slippage.

Upwardly of the belt section 2b an endless chain 8 is provided which is trained about sprocket wheels 9, 10 and II and rotates in the same direction and at the same speed as the adjacent belt sections a and 5c. The chain 8 is provided at identical distances with pressure springs I2 of springy sheet metal or other sheet material. which are so mounted that they will press above the belt sections 2b and 2c at the middle and along the so-called sealing line 5-5 (see FIGS. 2 and 3] lightly against the upper surface of the stack 1. The springs 12 which contact the stacks 1 thus move with the latter without performing any relative movement with respect to the stacks l. A pressure rail or member 13 exerts a uniform pressure upon the support rollers of the chain 8 so that the latter cannot be deflected upwardly by the pressure of the stacks 1 against the springs 12. If desired, corresponding rails or members can also be provided along or laterally adjacent to the sealing line 8-5 beneath the stacks I, that is beneath the run of the conveyor 2 which supports the stacks I, in order to prevent the stacks 1 from being downwardly deflected at least at or in the region of the sealing line SS.

Midway intermediate the ends of the roller 6 there is mounted in this embodiment a punching disc 14, and beneath it, also midway of the opposite ends of the roller 3 which is located below the roller 6, a cooperating counter disc 15, both being shown more clearly in FIG. 3. The disc 14 is provided on its periphery with a plurality of equiangularly distributed needles 140 which each enter into a corresponding small recess. aperture or groove 150 provided in the periphery of the cooperating disc 15. Thus, a stack 1 passing between the discs I4 and into the space between the belts 2 and 5, is provided with apertures or perforations la (see FIG. 4) along the line S--S of FIG. 2, and these perforations Ia are so spaced from one another in the direction of elon gation of the line SS that any two consecutive perfo rations la have from one another a distance which corresponds to the length of the center portion ofa clamp 25 (see FIGS. 5 and 6). Any two consecutive perforations la are also spaced from one another in the direc tion of the line 8-5 by a distance which is somewhat greater than the elongation of the springs 12 in the same direction, it being understood that these springs 12 will subsequently engage the stack 1 intermediate the consective ones of the perforations la. This prepunching or perforating of the stack 1 is intended to facilitate the subsequent passage of two pushing members or needles 23 (see FIG. 5) of a stitching device 22 through the stack 1, which needles push the spaced opposite end portions of a thread piece through these apertures or perforations Ia. However, it is emphasized that such prepunching and providing of the apertures Ia can be omitted without in any way influencing the validity of the basic inventive concept.

Reference numeral 16 in FIG. I identifies a bobbin or similar supply of a thread I7 which in the illustrated embodiment is assumed to be of heat-sealable type, for instance a filament or a rnulti-filament of a thermoplastic material. A thread supply disc 18 withdraws the thread 17 from the bobbin I6 and a thread cutting device l9 cuts it into successive pieces 20 the length of which corresponds to the length required for forming a single clamp as shown in FIGS. 5 and 6. The severed thread pieces 20 are maintained in taut condition (see FIG. 4) on the periphery of the thread supply disc I8 by engagement with clamping springs 21, being so located that each thread piece 20 spans a recess 27 provided in the periphery of the disc I8. The arrangement of the recesses 27 corresponds with the arrangement of the spring members I2 on the chain 8 in such a manner that, when the chain 8 and the disc member 18 are synchronously driven, there will always be one spring member 12 entering into a recess 27 of the member 18 5 before the thread 17 is tautened across the associated recess 27 and held in taut condition by the clamping springs 21 upon cutting from the remainder of the thread 17.

The periphery of the disc member 18 rolls on the upper surface of the stack l, and this results in the position IV shown in FIG. I, which is illustrated in more detail in FIG. 4. It will be seen that when the member 18 turns. the pressure spring 12 which is located in the respective recess 27 and presses the thread piece 20 associated therewith against the surface of the stack 1, will move along with the stack I in a straight line whereby the opposite end portions of the thread piece 20 are pulled loose from the clamping springs 21. Because the spring 12 is located precisely over the middle portion of the thread piece 20, i.e.. over that portion which will become the back of the finished thread clamp 25, mid way between two apertures la in the stack 1 (if such apertures are previously provided, which is not necessary as already pointed out) continuous advancement of the stack with the thread piece 20 held thereon by the associated spring member 12 causes the thread piece 20 to reach a thread stitching device 22 of any desired construction. This is shown in FIG. 5 and it will be seen that here the two associated needles 23 push the end portions of the thread piece 20 which project in opposite directions beyond the associated spring member 12, through the aperture la (or form such apertures and push the end portions through them if apertures have not been previously prepunched). Moreover, the needles 23 do not perform any relative movement with respect to the continuously advancing stack 1, but instead advance along with the stack 1. This means that at the position V of FIG. 1 it is possible to use continuously rotating needle carrying discs drive utilizing pairs of needles such as disclosed in one of the aforementioned copending related applications. The drawing clearly shows the somewhat wedgeshaped recesses in the free needle ends, which straddle the thread movement end portions.

In FIG. 5, in which a device such as the one just men tioned above with respect to the copending application is utilized, the deepest penetration of the needles 23, immediately before their upward movement for retracting purposes is illustrated. By contrast. FIG. I shows the beginning of their movement into and through the stack 1. It will be seen in FIG. 5 that when the needles 23 have reached the illustrated position, the end portions of the thread pieces 20 have been pushed through the perforations Ia by the needles 23 of the device 22, whereby the thread increment 20 has been transformed into a stitch 25 whose configuration essentially resembles that of a conventional metal staple (clamp). The end portions 26 of the stitch 25 pass vertically through the stack 1. On continued movement of the stack 1 the needles 23 move along with the same and are simultaneously withdrawn in vertical direction upwardly through and out of the stack 1, with the form and position of the stitch 25 being maintained unchanged because the spring l2 continues to press the center portion of the thread piece 20 against the upper surface of the stack 1.

with controlled needles, or a parallel flange needle In FIG. 6, which illustrates the encircled portion VI of FIG. I, l have illustrated the beginning of the operating step at which the parts of the end portions 26 which project beyond the lower side of the stack 1, are deflected into engagement with this lower side and sealed thereto. For this purpose there is provided beneath the stack 1 coincident with the sealing line 8-5 a heated sealing or bonding element 24 which is spring mounted or mounted for floating movement with very little spacing from the underside of the stack 1. The edge portion 24a of the member 24 which forms oppositely the direction of advancement of the stack 1 is slightly inclined as illustrated, and as the projecting parts of the end portions 26 move against it, they are deflected in upward direction, and by contact with the heated material of the member 24 they are sealed against the underside of the stack 1. Such sealing by heat is of course already well known and it is emphasized that sealing could also be effected in other manner, for instance by separately applying an adhesive. Once any one stitch moves in downstream direction beyond the member 24, the material of the stitch can cool and finally the associated spring member 12 is lifted off the stitch due to the change in the direction of movement of the chain 8 as the latter passes around the sprocket I0. Ultimately, the now stitched stack 1 is released by the belts 2 and 5 and can be received in a receptacle or can be passed on to other processing stations of user stations.

In FIGS. 7 and 8 I have illustrated one additional embodiment among the many which can be realized without departing from the scope and concept of the present invention. Here there are provided at opposite sides of the sealing line 8-8, extending in parallelism with the same, two walls or

plates

28 and 29. Located intermediate these are the non-illustrated thread supply arrangements, thread stitching arrangements and thread sealing arrangements which may operate in the same manner as previously described.

A toothed belt 30 which is endless is trained about two

wheels

31 and 32 of which the latter is driven and journalled on the plate 28. An equally long endless toothed belt 33 is trained about the wheels 34 and 35 of which the latter is driven and both of which are journailed in the plate 29. The

belts

30 and 33 are located at opposite sides of the sealing line 8-8 and in accordance with the present invention the journal bores for the

wheels

31 and 32 on the one hand, and the wheels 34 and 35 on the other hand, are each spaced from one another by identical distances and located at the same level, but are offset longitudinally by a distance D (see FIG. 7) which corresponds to the length of the desired thread pieces and therefore also to the spacing of the successive pressure-exerting elements which engage consecutive ones of the thread pieces.

A plurality of carrier bolts 37 extend through the gap defined between the upper and lower runs of the belt 30, being spaced from one another at the aforementioned distance D, and similar bolts 38 extend through the gap defined between the upper end lower run of the belt 33. Spring carriers 36 are pivotally mounted on the

bolts

37 and 38 and to these carriers 36 there is mounted by means of two rivets 39 a spring plate 40 which, as shown in FIG. 8, presses each thread piece against the respective stack 1.

In FIG. 8, which is a side-elevational view of FIG. 7, the plate 29 has been omitted for the sake of clarity. It will be appreciated that due to the coupling of the

belts

30 and 33 via evenly distributed pivotable spring carries 36 a drive of the belt 30 by means of the wheel 32 is sufficient to take along the belt 33. During such movement the carrier 36 will always maintain (due to 5 their pivotal mounting) the identical relative position in space. In FIG. 8 it is shown that each spring plate 40 will move vertically onto a thread piece which is held spanning a recess 27 of a disc member 18 (as described with respect to FIG. 4) and will press the thread piece against the upper surface of the stack 1 which in turn is advanced in the manner already described, for instance by means of the belt 33 shown in FIG. 8.

It will be understood that each of the elements de scribed above, or two or more together, may also find a useful application in other types of construction differing from the types described above.

While the invention has been illustrated and described as embodied in an apparatus of the type discussed, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the spirit of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

I. A method of thread-sealing superimposed layers of sheet material which advance continuously in a path. comprising the steps of continuously advancing a stack of superimposed sheet material in a straight-line path; withdrawing a heat-sealable thread from a supply; severing a length of thread from said heat-scalable thread at a location spaced from said path; moving the severed length of thread in stretched condition to and in direction lengthwise of said path and of the direction of advancement of said stack; placing the stretched length of thread onto and pressing it against one major side of the advancing stack so that it moves with the same; pushing spaced end portions of said length of thread through said stack so as to project in part from the opposite major side thereof; deflecting the projecting parts into engagement with said opposite major side; and heat-sealing each of said projecting parts directly to said opposite major side of said stack during the continuous advancement of said stack in said path.

2. A method as defined in claim I, wherein the steps of deflecting and sealing comprise moving said projecting parts past and effecting their contact with a stationary abutment located adjacent said path proximal to said opposite major side.

3. A method as defined in claim 1, wherein the step of heat-sealing said projecting parts to said opposite major side comprises heat-softening said parts and urging them against said opposite major side.

4. A method as defined in claim 1, and further comprising the preliminary step of forming openings in said stack during said advancement thereof and at locations of said stack where said end portions are to be pushed therethrough.

Claims

1. A METHOD OF THREAD-SEALING SUPPERIMPOSED LAYERS OF SHEET MATERIAL WHICH ADVANCE CONTINUOUSLY IN A PATH, COMPRISING THE STEPS OF CONTINUOUSLY ADVANCING A STACK OF SUPERIMPOSED SHEET MATERIAL IN A STRAIGHT LINE PATH, WITHDRAWING A HEAT-SEALABLE THREAD FROM A SUPPLY, SEVERING A LENGTH OF THREAD FROM SAID HEAT-SEALABLE THREAD AT A LOCATION SPACED FROM SAID PATH, MOVING THE SEVERED LENGTH OF THREAD IN STRETCH CONDITION TO AND IN DIRECTION LENGTHWISE OF SAID PATH AND OF THE DIRECTION OF ADVANCEMENT OF SAID STACK, PLACING THE STRETCHED LENGTH OF THREAD ONTO AND PRESSING IT AGAINST ONE MAJOR SIDE OF THE ADVANCING STACK SO THAT IT MOVES WITH THE SAME, PUSHING SPACED END PORTIONS OF SAID LENGTH OF THREAD THROUGH SAID STACK SO AS TO PROJECT IN PART FROM THE OPPOSITE MAJOR SIDE THEREOF, DEFLECTING THE PROJECTING PARTS INTO ENGAGEMENT WITH SAI OPPOSITE MAJOR SIDE, AND HEAT-SEALING EACH OF SAID PROJECTING PARTS DIRECTLY TO SAID OPPOSITE MAJOR SIDE OF SAID STACK DURING THE CONTINUOUS ADVANCEMNT OF SAID STACK IN SAID PATH.

2. A method as defined in claim 1, wherein the steps of deflecting and sealing comprise moving said projecting parts past and effecting their contact with a stationary abutment located adjacent said path proximal to said opposite major side.