GB2094702A

GB2094702A - Laminated tube

Info

Publication number: GB2094702A
Application number: GB8206364A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-12
Filing date: 1982-03-04
Publication date: 1982-09-22
Also published as: AU8127982A; JPS57197147A; FR2501573A1; DE3208625A1

Abstract

In a method of constructing a laminated tube, a pre-formed tube neck 3 is mounted on a mandrel 1 (Figure 2), a first sleeve 7 of heat shrinkable plastics material is then applied to the mandrel so as to at least partially overlay the neck (Figure 3), the first sleeve is then heat shrunk into conformity with the mandrel and into engagement with the tube neck, an intermediate layer 9 of material e.g. Al foil is then applied to the outer surface of the first sleeve and a second sleeve 10 of heat shrinkable plastics material is then applied over the intermediate layer, the second sleeve extending for substantially the entire length of the tube and substantially covering the tube neck (Figure 6), the second sleeve is then heat shrunk into conformity with the intermediate layer and the neck and the finished product is then removed from the mandrel. <IMAGE>

Description

SPECIFICATION Laminated tube The present invention relates to dispensing tubes.

Such tubes are well known and there are numerous methods available for constructing them. One such method is illustrated, for example, in Australian Patent 460,172.

Known construction techniques work well with single layer tubes but difficulties are encountered with techniques used for constructing laminated tubes. These laminated tubes are useful if it is necessary to protect the packaged product from contamination such as absorption of flavour or odour through a conventional plastics tube or incompatibility of the product with an internally coated metal tube. In some cases, the total cost of a laminated tube can be lower than that of a corresponding aluminium tube.

Unfortunately, known methods for producing laminated tubes result in a product which has several serious disadvantages. The laminate is first constructed by joining two or more layers of material such as plastics film and aluminium foil. This laminate is then cut and rolled to form the cylindrical body of the tube with a longitudinal join extending throughout the length of the tube. This longitudinal seam can be joined by well known techniques such as welding or double folding. The cylindrical body is then attached to the neck of the tube by any one of a number of processes including injection moulding, ultrasonic welding, spin welding or heat welding.

Regardless of which technique is used, the finished product incorporates a longitudinal joint throughout the length of the tube and a circumferential joint at the junction between the tube body and the neck. The resulting product suffers from the following disabilities: (a) The laminating process and subsequent tube forming technique is highly technical and requires high investment in equipment without, as yet, a consistently satisfactory product, safeguarded by adequate automatic quality controls to guard against separation or delamination of the various layers.

(b) Since the tube body must be joined both longitudinally and circumferentially by welding or other suitable process, there is a serious problem in maintaining the quality of the joints, which are prone to separation and delamination.

(c) The final closure of the tube by crimping and welding after filling is very slow and troublesome if any product (such as toothpaste) remains in contact with the tube walls. This results in an unacceptable product which must be discarded.

(d) Known techniques for joining the laminated sheets in longitudinal or circumferential seams frequently expose the inner laminates to the product at the edges of the sheet, resulting in tube corrosion and product contamination.

(e) Due to the method of constructing the tube body and the longitudinal seam, it is impossible to decorate the tube body for the full 360 degrees circumference of the tube.

(f) The existence of the longitudinal and circumferential seams frequently detracts from the overall appearance and feel of the final product.

It is an object of the present invention to provide an improved laminated tube and a method for constructing this product which eliminates or at least substantially lessens the above disadvantages.

According to one aspect of the invention there is provided a method of constructing a laminated tube comprising the steps of: mounting a pre-formed tube neck on a mandrel, applying a first sleeve of heat shrinkable plastics material to said mandrel so as to at least partially overlay said neck, heat shrinking said first sleeve into conformity with said mandrel and engagement with said neck, applying an intermediate layer of material onto the outer surface of said first sleeve, applying a second sleeve of heat shrinkable plastics material over said intermediate layer, extending for substantially the entire length of said tube and substantially covering said neck, heat shrinking said second sleeve into conformity with said intermediate layer and said neck; and removing said tube from said mandrel.

Preferably the neck is threaded and an additional capping stage is incorporated whereby an internally threaded closure cap is applied to the threaded neck over the outer layer of plastics material shrunk onto the neck, thereby to seal the tube neck and conform the outer plastics layer to the thread on the neck.

Preferably also, the intermediate layer is formed of aluminium foil, either pre-assembled or wound in a spiral onto the inner plastics layer whilst on the mandrel.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevation illustrating an empty mandrel prior to the commencement of the tube forming method.

Figure 2 illustrates a plastic tube neck in position on the mandrel.

Figure 3 shows the application of the first sleeve of plastics material over the mandrel and partially covering the neck.

Figure 4 shows the application of a heat shrinking step to the assembly illustrated in Figure 3.

Figure 5 shows the addition an intermediate layer in the form of of a spiral winding of aluminium foil, wound directly onto the first plastics layer shrunk into conformity with the mandrel.

Figure 6 shows the application of a second sleeve of plastics material, substantially covering the tube neck.

Figure 7 shows the application of a heat shrinking step to shrink the second plastics layer into conformity with the intermediate layer and tube neck.

Figure 8 shows the application of a closure cap to the threaded tube neck.

Figure 9 illustrates the finished product being removed from the mandrel.

Referring to the drawings, a series of mandrels 1 are secured to a rotatable turret 2 mounted for indexed rotation through a number of assembly stations.

At the commencement of the tube assembly process, a preformed plastic tube neck 3 is applied to the mandrel as shown in Figure 2 and supported on the end of an axially slidable spindle 4. The neck includes a threaded head portion 5 and a conical shoulder portion 6.

The turret next rotates to the station illustrated in Figure 3 and a first sleeve 7 of heat shrinkable plastics film material is applied overthe mandrel so as to partially cover the neck 3. The sleeve 7 is preferably cut from a seamless length of plastics tubing.

The turret next brings the mandrel into proximity with a heating unit 8 which shrinks the first layer 7 into close conformity with the mandrel and at least the shoulder portion 6 of the tube neck 3.

At the next assembly station illustrated in Figure 5, an intermediate layer 9 of aluminium foil is spirally wound onto the inner plastics layer 7. The spiral winding may be overlapped slightly or the strip may simply be butted in close edge-to-edge contact.

Alternatively, the foil may be pre-assembled in sleeve form and presented axially to the mandrel.

In the next assembly station illustrated in Figure 6, a second sleeve 10 of heat shrinkable plastics film material is applied to the mandrel and partially assembled tube in the same manner as shown in Figure 3. In this case, however, the forward end 11 of the sleeve substantially covers the neck.

The turret next indexes the mandrel into proximity with a further heating unit 12 which shrinks the outer plastics layer into close conformity with the two inner layers to form the final laminated tube. The forward sleeve portion 11 shrinks into conformity with the threaded head portion 5 of the neck 3.

Figure 8 illustrates a capping station where an internally threaded closure cap 13 is screwed into engagement with the threaded portion of the tube neck. This closely conforms the outer plastics layer 10 to the threaded neck to complete the formation of the thread and seal the forward end of the tube.

At station 9, the finished laminated tube 14 is ejected from the mandrel by the spindle 4, in readiness for filling or other subsequent processing.

If required, two or more of the assembly steps can be performed at a single station. For preference, however, the individual stations are spaced around a rotatable mandrel turret. The same turret may be simultaneously engaged in the formation of more than one tube in order to increase the tube production rate.

It will be appreciated that the laminated tube formed by the method described and illustrated above has unitary internal and external plastics walls, free from longitudinal seams. There is no exposure of the intermediate layer or layers to the product or layers to the product at joined edges.

Furthermore, the heat seal of the inner and outer tube layers to the neck is consistently strong and durable, being less prone to separation than the joining tschniques generally used for conventional laminated tubes. The method may be employed to produce tubes having any required number of laminations from two layers upwards. It is particularly useful, however, in the three layer embodiment illustrated, where a single intermediate layer is employed. In other cases where additional strength is required, additional layers of plastics or intermediate material may be applied.

The equipment required to perform the method is relatively inexpensive to construct and operate and product quality is superior to conventionally laminated tubes.

The method can, if required, be used with a longitudinally seamed intermediate layer or layers as well as longitudinally seamed heat shrinkable plastics film. Preferably, however, the plastics film is in the form of seamless tubing.

The outer layer of seamless tubing may be printed or decorated before or after the construction of the tube. In any event, the decoration of an outer seamless layer can extend throughout the full 360 degrees circumference of the tube.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in manyotherforms.

Claims

1. A method of constructing a laminated tube comprising the steps of: mounting a pre-formed tube neck on a mandrel, applying a first sleeve of heat shrinkable plastics material to said mandrel so as to at least partially overlay said neck, heat shrinking said first sleeve into conformity with said mandrel and engagement with said neck, applying an intermediate layer of material onto the outer surface of said first sleeve, applying a second sleeve of heat shrinkable plastics material over said intermediate layer, extending for substantially the entire length of said tube and substantially covering said neck, heat shrinking said second sleeve into conformity with said intermediate layer and said neck; and removing said tube from said mandrel.

2. A method as defined in Claim 1 wherein said neck is externally threaded and an internally threaded closure cap is applied to the threaded neck over said second sleeve, thereby conforming said second sleeve to the thread on said neck.

3. A method as defined in Claim 1 or Claim 2 wherein said intermediate layer of material is aluminium foil.

4. A method as defined in Claim 3 wherein said aluminium foil layer is wound in a spiral onto said first sleeve while on said mandrel.

5. A method as defined in Claim 1 wherein said mandrel is one of a plurality of mandrels circumferentially spaced around a rotatable mandrel turret.

6. A method as defined in Claim 5 wherein more than one tube is constructed simultaneously on said turret.

7. A method as defined in Claim 1 wherein said sleeves are longitudinally seamless.

8. A method as defined in Claim 7 wherein said second sleeve is pre-decorated.

9. A method substantially as herein described with reference to the accompanying drawings.

10. Alaminated tube formed by the method defined in any one of the preceding claims.