PAPER STRAW MANUFACTURE

Abstract

A method of manufacturing a bendable paper straw and a paper straw made in accordance with the method, the method including the steps, in any convenient order, of coating plies of flexible material, such as paper, with a generally liquid adhesive, such as food grade glue, forming on a mandrel having a generally smooth outer surface a tube composed of a plurality of plies of such coated flexible material, such as helically-wound plies, if necessary, cutting the tube into lengths suitable for forming finished straws, and before the adhesive has set, mounting the or each tube on a respective mandrel having a smooth outer surface and thereafter forming a series of generally concentric grooves on the outside the tube, such as by rolling, pressing or crimping the grooves, and thereafter moving one end of the tube towards the other end along its major axis, such as by pushing or pulling, whereby to axially compress the series of grooves to form a set of annular corrugations, and thereafter allowing the adhesive to set, whereby to form a straw bendable around the corrugated region into a temporarily deformed shape.

Claims

1. A method of manufacturing a bendable paper straw (as defined below), the method including the steps, in any convenient order, of coating plies of flexible material, such as paper, with a generally liquid adhesive, such as food grade glue, forming on a mandrel having a generally smooth outer surface a tube composed of a plurality of plies of such coated flexible material, such as helically-wound plies, if necessary, cutting the tube into lengths suitable for forming finished straws, and before the adhesive has set, mounting the or each tube on a respective mandrel having a smooth outer surface and thereafter forming a series of generally concentric grooves on the outside the tube, such as by rolling, pressing or crimping the grooves, and thereafter moving one end of the tube towards the other end along its major axis, such as by pushing or pulling, whereby to axially compress the series of grooves to form a set of annular corrugations, and thereafter allowing the adhesive to set, whereby to form a straw bendable around the corrugated region into a temporarily deformed shape.

2. A method according to claim 1 wherein the wall thickness of the paper tube exceeds the thickness necessary for making a stiff paper straw, the extra thickness allowing the formation of corrugations without the risk of damage being caused to the walls of the tube.

3. A method according to claim 1 wherein the generally concentric grooves are formed on the outer surface of the at least partially wet tube by one or more bladed rollers on an armature which press into but do not cut the outer surface of the tube.

4. A method according to claim 1 wherein the grooves are formed continuously i.e. helically but approaching concentrically.

5. A method according to claim 1 wherein the grooves are formed by a clamping process, such as by the use of a split die, each die half having internally matching grooves, such that when the die halves are clamped together they form concentric grooves around the tube which, on unclamping of the die halves, can then be used to form the corrugations in the tube when it is axially compressed on the mandrel before being ejected and subsequently allowed to dry.

6. A paper straw made in accordance with the method of according to claim 1.

7. A straw 15 according to claim 6 wherein the dipping end 13 of the straw is provided with a sharply defined blade 17 at 45 from the major axis of the straw 15 such that the blade 17 can be used to pierce an otherwise sealed opening in the container 16.

8. A straw according to claim 7 wherein the blade 17 is suitably formed before the straw blank 10 is dry and while still supported on a mandrel such that the walls of the dipping end 13 are supported as it is cut.

9. A drinks container 16 in combination with a paper straw in accordance with claim 6 in which the straw is pre-bent to a desired angle and releasably secured to an outside surface of the container, either directly or indirectly, such as in a sealed sachet.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0015] The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0016] FIG. 1 is a view of a prior art bendable paper straw in accordance with D1,

[0017] FIG. 2 is a view of the paper straw of FIG. 1 in which the top end is bent at right-angles for use,

[0018] FIG. 3 is a schematic view of a 3-ply paper tube formed on a smoothly-surfaced mandrel,

[0019] FIG. 4 is a view of part of a cut length of part of the paper tube of FIG. 3 onto which has been formed a series of grooves,

[0020] FIG. 5 is a view of the part of the tube shown in FIG. 4 after being axially compressed to form a series of corrugations,

[0021] FIG. 6 is a view of a finished straw in which the drinking end has been folded through 180 via the corrugations of FIG. 5, and

[0022] FIG. 7 shows the finished straw of FIG. 6 temporarily secured to the side of a drinks container.

DETAILED DESCRIPTION

[0023] Referring firstly to FIGS. 1 and 2 there is shown a prior art tubular paper straw 1 as taught by D1, the straw having an upper, drinking, end 2 for insertion between the lips of a user of the straw (not shown), a lower, dipping, end 3 for insertion into a drinks container (not shown). Immediately below the upper end 2 is a bendable section 4 having a series of nine crimped joints 5, between respective pairs of which are undeformed tubular segments 6 of the straw 1, the arrangement therefore allowing the upper end 2 of the straw 1 to be bent at approximately 90 to the major axis A of the straw in the manner as shown in FIG. 2. As explained in the teaching of D1, the formation of the joints 5 requires a fairly complicated arrangement involving several machines, the first for forming tubes from helically-wound plies of paper secured together with a suitable food-grade adhesive which, after drying, produces a stiff but waterproof tube which is then cut into lengths corresponding to individual straw blanks. Each tubular straw blank is then mounted on a corrugated mandrel in a corrugation machine which deforms part of it at spaced intervals by forming the joints 5 which thereafter act as living hinges, allowing limited angular movement between respective pairs of stiff tube segments 6. As a consequence of the stiffness of the tube segments 6 and the need to form corrugations therebetween at regular intervals along the length, which intervals correspond to the corrugations in the corrugation mandrel, they collectively impose a practical upper limit on the amount of joints 5 that may be provided in the finished straw 1 which, in turn, imposes a practical limit on the amount by which the straw can be bent. This prior art straw is therefore somewhat complicated to make and has limited bendability, only achieving a 90 bend by using roughly a third of the length of the entire straw.

[0024] In contrast to the prior art paper straw as taught by D1, the present invention provides a paper straw which is relatively easy to make, requiring no corrugated mandrel, and in which the corrugations can be much more numerous per unit length of straw in the relevant region. This is achieved by adopting a different approach to the conventional one of forming corrugations after formation of a stiff straw blank.

[0025] In accordance with the method of the invention and as shown in FIG. 3, a smooth mandrel 7 is used on which to form a correspondingly smooth-bored tube 8 made from helically-wound plies of paper 9, typically a layer of three overlapping plies, the plies being pre-coated with a suitable food-grade liquid adhesive such as AQUENCE BG 9040 LM supplied by Henkel AG. The length of the tube 8 is sufficient to be cut into several straw blanks 10, the end of one of which is shown in FIG. 4, which, before the adhesive has dried, is provided with a set of concentric finely-pitched grooves 11 in a manner to be described.

[0026] As shown in FIG. 5 the drinking end 12 of the straw blank 10 is then moved towards the dipping end 13, by pulling or pushing in the direction arrowed, whereupon a set of finely-pitched corrugations 14 is formed as a consequence of the presence of the grooves 11, the axial length of the straw blank 10 thereby being correspondingly reduced. By way of specific example, if the grooves 11, typically around 40 grooves, are formed over a length of 50 mm on the straw blank 10 and subsequently axially compressed to form corrugations 14 the length of the finished straw is typically reduced by around 15 mm.

[0027] In practice it has been found to be preferable to form a wet straw tube in accordance with the method of the invention with a wall thickness greater than is usually the case when making non-bendable paper straws, such that instead of the walls typically being 0.35 mm thick as is conventionally the case, by making the wall thickness 0.50 mm or some other suitably increased thickness, the additional material allows it to be more easily formed into corrugations without the risk of damage that may otherwise occur with walls of standard thickness, especially when they are not fully dried. It is to be expected that such additional wall thickness and the need therefor will depend upon the type of material used to construct the paper straw, as well as variations in the diameter or shape of the tube.

[0028] As will be appreciated, although the size of the corrugations 14 is relatively small as compared to the much more pronounced corrugations of D1 and D2, their number is relatively great, typically 40 such small corrugations over a distance of 35 mm of finished tube length, compared to the relatively few corrugations spread over a large distance as taught in D1. This large number of small corrugations 14 means that after the straw blank 10 has been dried and become stiff, the corrugated part can be easily bent to almost any angle up to around 270 from its major axis.

[0029] FIG. 6 shows the finished straw 15 in which the drinking end 12 has been bent through 180 relative to the major axis of the dipping end 13, this being made possible by virtue of the presence of the corrugations 14. Whilst being a considerable improvement over the bendability of the straws taught by D1 and D2, it has been found in practice that the dipping end 12 can be bent by up to 270, although this is generally not a requirement for such bendable straws. Nevertheless, it illustrates that the mechanical performance of the straw 15 is able to substantially match the mechanical performance of a bendable plastics straw, over which it has the obvious advantage of being biodegradable.

[0030] FIG. 7 shows the finished and folded straw 15 releasably mounted on the side of a drinks container 16, such as by being stored within an openable paper sachet (not shown) or simply by being secured directly thereto by means of a suitably light adhesive. The drinking end 12 has been bent through 180 prior to packaging and upon removal from the side of the drinks container 16 can be further bent to any desired angle in the same way as a bendable plastics straw. As such, the finished straw 15 represents a direct and easily manufactured replacement for such a bendable plastic straw whilst having essentially the same functionality.

[0031] In accordance with a refinement to the invention and as also shown In FIG. 7, the dipping end 13 of the straw 15 is provided with a sharply defined blade 17 at 45 from the major axis of the straw 15 such that the blade 17 can be used to pierce an otherwise sealed opening (not shown) in the container 16. The blade 17 is suitably formed before the straw blank 10 is dry and while still supported on a mandrel such that the walls of the dipping end 13 are supported as it is cut.

[0032] A further benefit of the invention arises due to the simplicity of manufacture, which does not require differently-shaped mandrels, one for forming a smooth-bored tube capable of supplying a number of straw blanks and another for forming corrugations in individual straw blanks after they have dried. Instead, the entire forming process can be performed on mandrels having smooth outer surfaces and a cross-section of shape and size substantially corresponding to the inside of the finished straw. This has significant cost-saving advantages over mandrels that are formed with corrugations, which are expensive to make and, necessarily, prevent them from easily ejecting the finished straw in the axial direction.