HUT76608A - Packing material, packing pillow and equipment for producing packing material - Google Patents

Description

Packaging material, packaging pads and equipment for the production of packaging material

BACKGROUND OF THE INVENTION The present invention relates to an improved packaging material for protecting fragile objects during transport.

US-A-2294478. and US-A-4105724. Packaging material is known from U.S. Patents, consisting of a flat sheet material (such as paper) having transverse rows of a plurality of longitudinally spaced slits, the slots of one row being offset relative to the slots of the adjacent row, such that the notches open to form islands that protrude from the plane of the sheet, thereby increasing the thickness of the sheet and making the material suitable for use as packaging material. Such a material is hereinafter referred to as an expandable material.

A sheet of such material can be used in many different ways, but due to its elasticity, when the tension is loosened, the notches tend to close and take on a more or less flat shape. In general, therefore, the object to be protected must be packaged with the sheet material in its tensioned state. Difficulties in using said sheet material occur mainly when it has to be used as filler when placed under, over or around the article to be protected.

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US-A-3306513. It is known from U.S. Pat. No. 4,011,123 that the expanded sheet is blown with a suitable liquid, which is suitably flame retardant and which, when dried, retains the expanded sheet, thereby allowing it to be used as packaging material, even as a layered sheet. However, such spraying makes the sheet rigid, thereby reducing the benefits of the soft wrapping material and, in addition, possibly adding unwanted chemicals to the wrapping material.

The packaging material according to the invention consists of a base plate of non-expandable material and a second base plate of expandable material, the second plate having longitudinally spaced notches arranged so that the notches of one row are offset from those of the adjacent row. the plate is fixed to the base plate when expanded.

By "non-expandable" is meant that it is non-expandable from the point of view of use and not in all absolute terms. In particular, it is understood to be significantly less expandable than the expandable material used to achieve the desired purpose.

In the simplest embodiment of the invention, said expandable material is a specific quality expandable material, such as wrapping paper or kraft paper, of any suitable weight, generally 45 to 150 mg / m2, having a parallel row of notches transverse to one of the rows. the notches being offset relative to the notches of the adjacent row, the paper is stretched longitudinally to open the notches and, in this state, the tensioned paper is secured to a non-expandable kraft paper having a similar density.

The second plate may be secured to the base plate by its edge, such as by means of an adhesive or, for example, by knurling or pressing welding, for which no other component is used.

The thickness of the bilayer sheet of the present invention can thus be about ten times the thickness of a single sheet, which remains unlimited when expanded. This material can be used as packaging material without the need for special measures to maintain the expanded material in its expanded state. One or more pieces of this material can be laid and fragile materials placed on it.

According to the invention, the sheet material preferably comprises a plurality of sheets, for example two, preferably three or more expandable materials, which are fastened to the base sheet when expanded, thereby providing a significant increase in thickness and a relatively inexpensive increase in impact absorption capacity. Preferably, one of the plates of the expandable material is reversed. As a result, the protruding portions of one of the plates are joined to the openings of the adjacent plate, thereby increasing the stability of the packaging material.

If necessary, a further non-expandable sheet material may be used and the expandable material sheet is sandwiched between two non-expandable sheets.

Optionally, the non-expandable material may have an outer surface or surfaces printed so that it may include the name of the product, the name of the manufacturer, the dealer, may include drawings, and the like.

The packaging material according to the invention can be wound, which can be cut off from the roll or stored in pre-cut lengths.

The invention also relates to a process for the manufacture of a packaging material according to which

a) using a first long sheet material,

b) using a second long sheet material,

c) making short notches substantially transverse to the longitudinal direction in the second long sheet material, forming the notches longitudinally adjacent to one another in a displaced position relative to one another; and

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d) securing the second long sheet material to the first long sheet material when tensioned.

The present invention also relates to an apparatus for the manufacture of packaging material

a) a first storage device for feeding a non-expandable sheet material;

b) a second storage means for dispensing a second sheet material having a plurality of longitudinally spaced slots in the second sheet material and the slots in one row being offset relative to the slots in the adjacent row;

c) means for contacting each of the first and second disk material during removal from their respective storage means; and

d) means for securing the two disks together to the first disc in an expanded state.

The storage device has fittings for coils of expandable and non-expandable materials. However, if necessary, the assemblies may have coils of non-expandable material and the apparatus may have means for making cuts in one of the rolls which are peeled off to provide expandable sheet material.

Preferably, the first sheeting means comprises a first pulling means for removing the first sheet material from the first storage means and a second drawing means for stripping the second sheet material from the second storage means, and the first drawing means operates proportionally faster than the second drawing means.

Preferably, the second drawing means consists of cylinders spaced relative to one another and preferably has at least some elastic deformation of its surface.

Preferably, the device comprises a second tensile material expanding means following the pulling means to generate tension.

Preferably, the expanding means engages the second plate and draws tension therein while pulling from the pulling means,

-5 · · · ···········································································································································································································································. If necessary, the cylinders may have a plurality of radially protruding protrusions extending into the notches. Such protrusions can be formed by the creasing on the outer surface of the cylinder. Preferably, however, the rollers of the expanding device are serrated, which teeth extend through the openings under tension, and the sheet material is pulled away from the stripping device at a speed greater than the speed of the stripping device from the second sheet material roll on the second assembly.

The longitudinal cross-section of the teeth is preferably triangular, preferably having a prism. Preferably, the rows of circumferential teeth are spaced relative to one another, and the cylinders are preferably offset relative to one another, and the teeth on one cylinder are axially disposed so that the periphery of the other cylinder is directly opposite two adjacent rows of teeth.

The distance between the rollers is preferably such that there is no or only a small gap between the crowns of the teeth of the two rollers.

Preferably, one roll is driven, the other roll rotates freely and rotates by engaging the teeth thereon to extend into the slits of the expandable sheet material and pull the sheet material through the expanding member.

In this way, the synchronization difficulty between the two toothed rollers can be minimized.

Thus, the expanding means preferably draws the sheet material at a substantially similar rate as the first stripping means feeds the non-expandable sheet material from its roll.

The surfaces of the two sheet materials may be contacted directly at the point of entry before the contact line of the expanding device or immediately after the expandable sheet material exits the expanding device.

Preferably, the anchoring means is located downstream of the contact line of the expanding means for the movement of the material. Preferably, the fastening means connects the plates along longitudinal lines, at least two of which are along the edges of the plates.

Preferably, the locking means is a ratchet means.

The holding means hold the plates between the expanding means and the fixing means, which are preferably formed with support strips of rubber or similar elastic material.

In a further preferred embodiment, the apparatus comprises further assemblies for one or more additional rolls of expandable sheet material, and preferably further assemblies for a further roll of non-expandable sheet material, wherein the structure and arrangement are such that the expandable sheet material expanding means, preferably in contact with at least one non-expandable sheet material. Thus, if necessary, the sheets of expandable material are passed together through the expanding means by guiding the sheets of expandable material between the sheets of non-expandable material during passage through the expanding rollers, but preferably one of the non-expandable sheets is passed through the expanding means. , but is in contact with expandable plates prior to passing through the fixing means (slotted rollers).

In the following detailed description, the packaging material according to a preferred embodiment of the invention will be described with reference to the accompanying drawings, which are exemplary only of the invention. for the purpose of illustration, the process for manufacturing the packaging material and the apparatus for producing the packaging material according to the invention are exemplified. design.

In the drawings it is

Fig. 1 is a schematic view of a packaging material according to a preferred embodiment of the invention, with a portion broken away for a clearer understanding of the inner layers; the

0000 00 0 0 0 0 00 0 0 0

Figure 7 is a schematic diagram of the apparatus for producing the material in question;

the

Figure 3 illustrates a pattern of notches applied to a sheet material as they are formed as the sheet material passes through a pair of notch rolls; the

Fig. 4 is a sectional view taken along line 4-4 of Fig. 2, showing a pair of knurled rollers used to make the preferred embodiment; the

Figure 5 is a schematic side view of a device according to a preferred embodiment of the invention; the

Figure 6 is an enlarged view of the means for expanding and securing the apparatus; the

Figure 7 is a perspective view of the arrow in Figure 5 showing the front view of two cylinders of the expanding device and

Fig. 8 is an enlarged view of the passage of the plates through the expanding means.

The packaging material according to a preferred embodiment of the invention consists of three sheets 4, 6 and 8 of wrapping or kraft paper, which are stored in rolls 5, 7 and 9 of Figure 2. The plates 6 and 8 are guided through a pair of notch rolls 10, 12, each of which produces a plurality of notches 13. The notching rollers 10, 12 also act as a pulling means for pulling sheet material from the rolls 7 and 9.

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The notches 13 in the plates 6 and 8 are formed substantially in the pattern shown in Figure 3, i.e. the notches are arranged in several rows and the notches of each row X are in the same direction and parallel to the notches of an adjacent row Y; and each notch 13 is laterally offset relative to the longitudinally adjacent notches. Such material, as is known in the art, stretches longitudinally (in the direction A in FIG. 3) and expands in the direction of thickness to form islands in the sheet material which are inclined to the plane of the sheet and allow the sheet material to used as packaging material.

Passing through the plates 6 and 8 between the notched rollers 10, 12, the two plates 6 and 8 are in contact and inserted between additional rolls 14, 16 which constitute the expanding means of the apparatus and which rotate faster than the plates 10, 12. rollers in order to extend the discs 4 and 6, thereby opening the notches as described above. Immediately thereafter, the sheets 4 and 6 are joined to and passed through a pair of notched (unexpanded) wrapping paper between a pair of knurled rolls 18, 20, whereby the sheets 4 and 6 are flattened to the sheet 8 in their flange region (19a, 19b). so that the plate 8 keeps the plates 4 and 6 in their tensioned, i.e. expanded, state.

Consequently, the knurled rollers 18 and 20 also serve as a pulling means for pulling material from the roll 5.

As shown in Figure 2, the paper is pulled off the rolls 7 and 9 in opposite directions, i.e., the top of the paper faces each other. In this orientation, it has been found that, when the paper is tensioned, the resulting islands are inclined in opposite directions and, while they tend to interconnect, are not embedded to the same extent as when the paper is led in the same direction.

-9 • · * · Thus, if two or more disks are used as an intermediate packing layer, the top of the disks will alternate in different directions.

The packaging material produced in this way can be wound into a roll which can be unwound into sections of appropriate length during use. When cutting the length of the wrapping material, this is preferably done in combination with a transverse compression welding device combined with a cutting scissor, whereby the ends of the wrapping material are sealed in the same way as the edges are sealed. This prevents the tensioning of the inner plates at the end portions from loosening.

It is also possible to provide further longitudinal compression welding or welding between the edge regions of the layer, e.g. such that two such welds are applied relatively close to one another in the center between the edges of the cut sheet, e.g. cut between two such welds with a knife to form two half-width plates.

The packaging material according to a preferred embodiment of the invention consists of two layers of expandable sheet material and one layer of non-expandable sheet material, but if necessary three or more layers of expandable sheet material may be used and, if desired, the expandable sheet material may be sandwiched between two layers of non-expandable sheet material. In such cases, the ribbed rollers 18 and 20 are provided with pulling means for both sheets of non-expandable sheet material.

The non-expandable sheet material may be a flat material on which appropriate labels, warnings, trademarks, names and the like may be printed.

A preferred embodiment of the apparatus of the present invention comprises a housing 106 having a base 108 having assemblies 108 comprising assemblies 108a, 108b, 108c and shafts 109 on which rolls 110a, 110b, 110c of paper or similar material can be placed.

In the use of an apparatus according to a preferred embodiment of the invention, the sheet material 108a,

- ΙΟΙ 08b and 108c mounted on fittings. The long sheet material 112a, 112b, 112c is aligned with its planes by the pulling means 116 formed by a pair of driven rollers 118a, 118b having a rubber-coated surface and the three-layer material 120 as shown in FIG.

122 to an expanding device.

As shown in Figure 5, the sheet materials 112a, 112b and 112c are pulled off of the rolls 110a and 110c with the same orientation and from the rolls 110b in the opposite orientation.

The apparatus has an expanding means 122 consisting of an upper cylinder 124a and a lower cylinder 124b, each of which has teeth arranged in a circumferential row having an axial cross-section as shown in FIG. 6, but having a longitudinal cross-section as shown in FIG. Figure 7.

The circumferential rows 126a-126z of the upper cylinder 124a are spaced relative to one another and the lower 127b rows 127a-127z are laterally offset, as shown in Figure 7, so that each row 127a is adjacent to one another e.g. 126a, 126b and vice versa.

The diameter distance between the crowns of the teeth of the cylinder 124a and the crowns of the teeth of the cylinder 124b is zero or near zero.

The rollers of the expanding device 122 rotate proportionally faster than the pulling rollers 118a, 118b, so that when three layers of expandable sheet material pass through the pulling rollers 118 into the expanding rollers, the material is stretched longitudinally and the notches on them open to form prominent islands. as is known per se. The teeth 125 of the lower cylinder penetrate into the openings in the lower layer and pull the material through the stretching means. At the same time, the teeth 127 of the upper cylinder extend into the openings formed in the upper layer, whereby the three layers are partially nested, as shown in FIG. This is due to the fact that the intermediate sheet material 112b is inverted. By engaging teeth 126 in the openings in the top layer, cylinder 124a is provided

- 11 · · ··································································································NING: 11 11 11ön 11ön 11 11 11 11ön 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11ön 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 ön 11 11 11ön 11 11 11 11 11 11 11 11önönönönönönönönönönönönönönönönönönönönönönönönönönönönönönönön j jönönönönönönön j j j jönönön j jönönönönön nehéz nehéz nehéz nehézön nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehézhetőkhetőkhetőkhetőkhetők nehéz nehéz nehéz nehéz nehéz nehéz nehéz nehézkerül nehézhetőkhetőkhetők nehéz nehéz nehéz nehéz. However, if necessary, the upper cylinder 124a may be driven by a structure synchronized with the lower cylinder 124b.

In one embodiment of the rollers provided with teeth, the rolls have a rough (hairy) surface along the periphery of the rolls, and the expandable sheet material is introduced between the rolls. The razor is easy to penetrate through the notches and openings, as the islands protrude from the plane of the material surface, the razor has an elasticity that is selected so that it does not deform or tear the material. Under these conditions, the shaving is preferably configured on the peripheral surface of one or each of the rolls to have a relatively high density so as to ensure that the plurality of strands extend into the openings of the sheet material in each case, thereby extending the stretching load in the sheet material. risk of paper tearing.

Preferably, the shirring is formed on a circumference of one or each of the rolls on a relatively small width of ribbon-like substrate applied to the peripheral surface of the roll along a helix. The two rollers are spaced at a short distance from each other so that the creases extend into each other so that the creases can properly extend into the openings in the sheet material.

By providing adequate elasticity of wrinkling, wrinkles that do not need to penetrate into the material are bent into an inactive position and contact the sheet material as it passes between the two rollers.

In this way, the razor may be a natural razor such as that used with a brush, but may be made of a synthetic material such as a razor. made of plastic or rubber.

Supporting means formed by the rubber bands 132a, 132b which hold the expanded sheet material after the expansion rolls are arranged around the rollers 124a and 124b and further rollers 130a and 130b.

-12 · kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil kil 12 12 kil 12 12 kil 12 kil 12 12 kil kil 12 kil kil 12 kil kil kil kil kil kil kil kil kil kil kil 12 12 kil kil 12 12

The apparatus according to a preferred embodiment of the invention further comprises fittings 140 consisting of holders for the cylinders 142a, 142b on which coils 146a, 146b of the non-expandable sheet material are disposed, e.g. wrapping paper or kraft paper. Instead of expandable material directly exiting from the expanding means 122, there are locking means 150 formed by a pair of overlapping wrinkling rollers 152a, 152b which are used to secure the edges of the composite sheet material by shirring together.

Leaving the rollers 130, a non-expandable sheet material 148a, 148b is guided in close connection therewith under and over the composite expanded material, and the five layers are guided through a retaining means 150 which secures at least one, preferably both, edges of the composite sheet. Placing and fixing the expanded sheet material between the non-expandable sheet materials prevents longitudinal movements of the expandable sheet material that would occur if the expandable sheet material could contract to an unexpanded form. The presence of the two non-expandable sheet materials thus maintains the stretched state of the core of the expandable sheet material and thereby maintains the cushioning effect of the packaging material during use.

However, if necessary, a single non-expandable sheet material can be used alone, i.e. one of the rolls 142 or 144 may be omitted.

Particularly in such cases, the fastening device 150 secures the composite layers to one another at intermediate locations but along a longitudinal line.

In the embodiment shown in Fig. 2, the fastening means also serves as a pulling means for the sheet material to pull the material from the rolls 146a, 136b. However, if necessary, separate pulling devices may be applied to one or both sheet materials.

• · · ·

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In a preferred embodiment, the dispensing means has racks for the respective expandable (notched) sheet material and expandable (uncut) sheet material. If necessary, the apparatus may be provided with holding rollers for feeding expandable (non-slit) material, e.g. five rolls of kraft paper, the second dispensing means further having means for cutting three sheets of material in addition to the holding means of the three rolls, thereby subjecting the sheets to a proper cutting operation after being removed from the rolls and before being inserted between the expanding means 122.

While in the preferred embodiment, both non-expandable sheet materials 148a and 148b are contacted with the expandable sheet material or sheets after passing these sheet materials through the expanding means, if necessary, one of the sheet materials may be contacted prior to passing the expandable material through on expanding devices. Under these conditions, the teeth of adjacent rollers corrugate the non-expandable material as the material deforms upon contact with the teeth and as the teeth enter the openings of the expanded material. Preferably, however, not more than one layer is contacted in this way prior to introduction into the expanding means.

The present invention has been described above in connection with the use of sheet material which has recesses formed in a regular, parallel pattern with an even lateral displacement. If desired, other notch arrangements may be used, including randomly arranged notches or notches that allow the material to expand in a manner other than expansion by purely longitudinal pulling. For example, a notch arrangement may be provided in which the notches are at an angle to the longitudinal axis, thereby allowing the material to expand by lateral drawing.

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In addition, although the invention has been described above using wrapping paper as both expandable and non-expandable sheet material, materials comprising a combination of different types of materials may be used if desired.

The features discussed in the above description, either in the accompanying drawings, are embodied in the specified form, or are described in terms which correspond to their function or are described as a method of achieving the desired result or are appropriately classified in the appropriate class of materials. they can be combined in any way to carry out the invention in different ways.

Claims (28)

Packaging material, characterized in that a base plate (4; 18a; 148b) of a non-expandable material and a second base plate (6 or 8; 112a, 112b or 112c) of expandable material are formed by longitudinally spaced slits (13). ) are arranged in rows such that the slots in one row are offset relative to the slots in the adjacent row and the second plate is fixed to the base plate when expanded. Packaging material according to Claim 1, characterized in that the base plate (4; 148) is made of paper and the second plate (6 or 8; 112) is made of paper formed by cuts (13) in parallel rows, one of the rows (X). its notches are offset from those of the adjacent row (Y). Packaging material according to Claim 1 or 2, characterized in that the second plate (6 or 8) is fixed to the base plate (4) by a physical process, without the use of any additional component, for example by kneading or pressing welding on the edge (19a, 19b). it is. 4. Packaging material according to any one of claims 1 to 3, characterized in that a plurality of expandable material sheets (6, 8; 112a, 112b, 112c) are attached to the base sheet (4; 148) in their expanded state. Packaging material according to Claim 4, characterized in that the adjacent plates (4, 6; 112a, 112b, 112c) of the expandable material have an inverse orientation with respect to one another. • · - 16 • · ·> · · ··· · · · «4» ·· • «·« · 6. Packaging material according to any one of claims 1 to 3, characterized in that a further sheet (148) of non-expandable material is provided and the sheet (112) of expandable material is inserted between two non-expandable sheet materials. 7. A process for the manufacture of packaging material, characterized in that: a) using a first long sheet material (4; 148), b) using a second long sheet material (6 or 8; 112a, 112b, 112c), c) making short notches (13) substantially transverse to the longitudinal longitudinal direction of the second long sheet material, and forming laterally adjacent notches in a laterally offset position; d) securing the second long sheet material (6 or 8; 112) to the first long sheet material (4; 148) in the tensioned state. The method of claim 7, wherein the first long sheet material and the second long sheet material are paper. Packaging cushion, characterized in that it has outer layers (148a, 148b) of non-expandable sheet material and at least one layer (112) of expandable sheet material is fastened between the outer layers along its longitudinal edge, whereby the expandable sheet material (s) remain in an expanded state against their longitudinal contraction. Apparatus for the manufacture of packaging material, characterized in that: a) a first storage means (5; 142, 146) for feeding a non-expandable sheet material; b) a second storage means (7, 9, 10, 12; 108, 109, 110) for feeding a second sheet material (6, 8, 112), the second sheet material being large, - has a notch (13) spaced longitudinally and the notches (13) of one row (X) are offset relative to the notches of the adjacent row (Y); c) means (18, 20; 150) for contacting the first and second sheet material during disconnection from their respective storage means; and d) a means (18, 20; 150) for securing the two sheet materials (4, 6, 8; 148, 112) together in the expanded state of the first sheet material. Apparatus according to claim 10, characterized in that the first sheet material is pulled from the first storage means (18, 20; 152) and the second sheet material is drawn from the second storage means (10, 12; 116). and the first pulling means (152) operates proportionally faster than the second pulling means (116). Apparatus according to claim 10 or 11, characterized in that the second drawing means (116) consists of cylinders (118a, 118b) spaced relative to one another. Apparatus according to claims 11 and 12, characterized in that, after the pulling means (10, 12; 116), the second material has an expanding means (14, 16; 122) for generating tension in the second material. Apparatus according to claim 13, characterized in that the expanding means have rollers (124a, 124b) for receiving the second sheet material and for generating tension during pulling from the pulling means. Apparatus according to claim 13, characterized in that the rollers of the expansion device are serrated, the teeth (126) extending through the openings created by the tensile stress and the sheet material from the extraction means. - 18 · «· • · * is pulled at a speed greater than the speed of the peeling device from the second material coil on the second assembly. Apparatus according to claim 15, characterized in that the teeth (126) have a triangular cross-section. Apparatus according to claims 15 and 16, characterized in that the rows of circumferential teeth are spaced relative to one another and the cylinders are preferably offset relative to one another and the teeth (126) of one of the cylinders (124a) are positioned so that they are directly opposite the space between two adjacent rows of circumferentially of the other roller (124b). Apparatus according to claims 15, 16 and 17, characterized in that the distance between the rolls is such that there is no or only a very small gap between the crowns of the teeth (126a, 126b) of the two rollers. 19. Apparatus according to any one of claims 1 to 4, characterized in that one cylinder (124a) is driven and the other cylinder (124b) rotates freely. 20. The apparatus of claim 13, wherein at least one of said rollers is provided with radially protruding protuberances, said protruding extending into tension openings in said material, said material being removed from said pulling means by said pulling means on said second assembly. pulls at a speed greater than the second roller. 21. Apparatus according to any one of claims 1 to 3, characterized in that the expanding means (122) is substantially sheet material -19 passes at a similar speed as the first puller (150) feeds the unexpanded sheet material from its roll. 22. A 10-21. Apparatus according to any one of claims 1 to 4, characterized in that the retaining means (150) is located downstream of the contact line of the expanding means for the movement of the material. 23. A 10-22. Apparatus according to any one of claims 1 to 4, characterized in that the recording means interconnects the discs along longitudinal lines, at least two of which are disposed along the edges of the discs. 24. A 10-22. Apparatus according to any one of claims 1 to 5, characterized in that the fixing means comprises a knurling means. 25. A 10-24. Apparatus according to any one of claims 1 to 3, characterized in that the holding means (132a, 132b) holds the plates between the expanding means (122) and the fixing means (150). 26. A 10-25. Apparatus according to any one of claims 1 to 3, characterized in that it comprises further fittings (108a, 108b) for one or more further coils (110a, 110b) of expandable sheet material and preferably further fittings (144) for additional coils (146) of non-expandable sheet material. Apparatus according to claim 25, characterized in that the plates of expandable material are guided together through the expanding means (122) by passing the sheets of expandable material between the sheets of non-expandable material during passage through the fixing means (150). . 28. The apparatus of claim 26, wherein the plates of non-expandable material are guided through the expanding means, One of the non-expandable material sheets is contacted with the expandable material sheets during passage through the expanding rollers, the other non-expandable material sheet after passing through the expanding means but prior to passing through the locking means.