EP0210052A2

EP0210052A2 - A packaging tube

Info

Publication number: EP0210052A2
Application number: EP86305502A
Authority: EP
Inventors: Patrick Francis Mcdonnell
Original assignee: Henkel Loctite Ireland Ltd
Current assignee: Henkel Loctite Ireland Ltd
Priority date: 1985-07-17
Filing date: 1986-07-17
Publication date: 1987-01-28
Also published as: IE851792L; EP0210052A3

Abstract

A packaging tube for dispensing liquid materials, particularly cyanoacrylate adhesives, comprises:-

(a) an outer hollow cylinder (1) having a crimp (4) at one end and a nozzle (2) at the other end to dispense material from the tube, the outer hollow cylinder (1) being made of a ductile material; and
(b) an inner hollow cylinder (3) located within the outer cylinder (1), the inner cylinder (3) being made of an elastic material such as plastics or stainless steel, the inner cylinder (3) being located adjacent the outer cylinder (1) and containing the material to be dispensed, such that upon compression of the outer cylinder (1) the inner cylinder (3) is compressed from its original shape, thereby dispensing material out of the nozzle (2) and upon release of compression of the outer cylinder (1) the elastic material of the inner cylinder (3) resumes its original shape and concurrently reforms and retracts nondispensed material contained in the nozzle.

Description

This invention relates to a packaging tube for dispensing liquid materials and is particularly intended for use with adhesives, more especially cyanoacrylate adhesives, including thixotropic adhesives, but is also useful for other reactive liquid materials.
Metal tubes, in particular aluminium tubes, are widely used for packaging purposes because they are impervious to atmospheric moisture, oxygen or contaminants. Such tubes are generally regarded as the ideal package for cyanoacrylate adhesives in particular.
The tubes generally have a nozzle at one end and are initially open at the other end. They are filled with material by charging the appropriate quantity through the open end of the tube before it is crimped. In order to avoid part of the contents being expressed during the crimping process, the tube is not filled completely and so air is usually trapped inside the tube, between the crimp and the contents. As crimping is completed, the pressure of this trapped air is increased.
The closed end of the tube usually has a membrane or nozzle which is punctured when the contents are about to be dispensed. Generally the tube is held with the crimped end downwards during the puncturing procedure. With low viscosity materials the contents will usually flow downwards and the air pressure will be normalised. However with thixotropic grades of material the compressed air at the crimped end of the tube is prevented from escaping by non-mobile material in the nozzle area.
When the membrane or nozzle of such a package has been pierced, a slight finger pressure on the tube body causes material to be dispensed through the nozzle and the package is permanently deformed. With both low-viscosity and thixotropic materials, it is difficult to dispense discrete drops from the tube. Furthermore with thixotropic materials the compressed air in the tube, combined with the permanent deformation of the tube, causes the material to continue to be dispensed even when finger pressure on the body of the tube has ceased. Substantial quantities of material in excess of the desired quantity are wasted, the excess is messy and can cause problems of contamination. In the extreme case, almost the whole contents of the tube can be dispensed on the first use.
With thixotropic adhesives, there is the additional problem that the presence of adhesives in the nozzle area can result in blockage because adhesives have a tendency to set under such conditions and in the case of cyanoacrylates can set to a very hard condition.
Resilient plastics tubes are known for packaging purposes, and are used for example with anaerobic adhesives. Due to the elastic properties of the wall of such a tube, discrete drops of material can be dispensed by finger pressure and the tube then resumes its original shape. However the plastics tubes currently available are pervious to moisture, oxygen and pollutants and are unacceptable for cyanoacrylates and other reactive materials which must be kept sealed, from moisture in particular, during a shelf life which, desirably, can be as long as 2 years.
Various proposals have been made in the past for resilient support structures for collapsible tubes. U.S. Patent 1,352,355 Cleveland, issued in 1920, describes the use of flexible spring strips applied longitudinally or as annular rings on the outside or the interior of a tube, to produce a retracting effect on the contents within the tube when the pressure of distortion has been relieved. However this disclosure relates to tubes for toothpaste, library paste, mucilage and the like plastics or semiplastic materials. These materials are dispensed in substantial quantities and are different in nature from reactive adhesives such as cyanoacrylates which should be dispensed at a rate of one or two drops at a time. It follows therefore that the aluminium tubes used for reactive adhesives are much more sensitive to finger pressure than those described in the Cleveland Patent, and the problem of adhesive setting in the nozzle area is much more acute.
U.S. Patent 2,596,592 Parker describes a collapsible dispenser tube having arcuate resilient bands arranged longitudinally therein, which bands retain the tube in its expanded condition when the tube is not in use. However these bands are part of a tube closing mechanism of special structure. U.S. Patent 2,123,558 Altheide describes a device for applying fluid to the scalp, which device is wedge shaped and has a U-shaped sheet of metal or other spring material within it to urge the walls normally outwardly.
All of these prior art devices require a special construction of container or a special modification of it. In the case of the Cleveland patent, the spring strips or rings must be secured to the tube in some undescribed manner so that they will stay in place.
It is an object of the present invention to overcome the long- recognised problems of packaging tubes for reactive adhesives, particularly cyanoacrylate adhesives, and to overcome these problems in a way which enables the conventional aluminium tubes to be continued to be used, so as to minimise expense.
The present invention provides a packaging tube for dispensing liquid materials comprising:-

(a) an outer hollow cylinder having a closed end and a dispensing end, said dispensing end comprising a tip means to dispense material from said packaging tube, said outer hollow cylinder being made of a ductile material; and
(b) an inner hollow cylinder located within said outer cylinder, said inner cylinder being made of an elastic material, said inner cylinder being located adjacent said outer cylinder and containing the material to be dispensed, whereby upon compression of the outer cylinder the inner cylinder is compressed from its original shape, thereby dispensing material out of the tip, and upon release of compression of the outer cylinder said elastic material of the inner cylinder resumes its original shape and concurrently reforms and retracts nondispensed material contained in said tip means. Preferably the tip means is adapted for dropwise dispensing of thixotropic or liquid adhesives.

In a preferred embodiment the outer cylinder is a metal tube particularly an aluminium tube while the inner cylinder is a cylindrical sleeve of resilient material, suitably plastics material such as polyethylene, more particularly high density or medium density polyethylene. Normally the sleeve has an external diameter marginally less than the internal diameter of the outer cylinder. Preferably the sleeve has a wall thickness in the range 0.1 - 1.0 mm, more particularly 0.1 - 0.5 mm, especially about 0.2 - 0.25 mm. The wall thickness is such that the tube is easily compressed by finger pressure (to dispense contents) and yet is sufficiently resilient to ensure that the tube regains its original shape without permanent dents being formed. The sleeve suitably extends continuously for a major part of the length of the tube, preferably from the closed end of the tube to a point adjacent to the crimping region.
The inner cylinder may alternatively consist of a sleeve with diametrical struts inside it or it may have a more elaborate structure inside the sleeve, for example a three dimensional honeycomb matrix made from a suitable plastic material. This type of insert could be specially shaped to conform with the shape of the crimped tube.
The inner cylinder may also consist of a stainless steel liner of appropriate gauge to achieve the desired springiness as described above for the plastic cylinder, although care must be taken to use a well-machined stainless steel cylinder which has no sharp edges which could cut through the outer cylinder.
A further alternative insert may be a strip of plastic or spring metal rolled into a cylindrical coil of suitable length and inserted in the metal tube. The coil will then take up the internal shape of the tube and provide the necessary resilience.
The inner cylinder can be manufactured in a range of materials and various shapes or designs. The materials would be chosen not only for functionality but also with due regard to compatibility with cyanoacrylate adhesive or other proposed contents. Particularly suitable materials are the grades of polyethylene which are used in making bottles for cyanoacrylate adhesives.
The structure of the inner cylinder should be such that it does not interfere appreciably with the flow of the contents to the nozzle when the tube is compressed under finger pressure. The volume of the inner cylinder should be sufficiently small that it does not occupy an excessive proportion of the volume of the tube and in particular should not prevent the normal charge of contents being filled in to the tube without the contents occupying part of the crimp region of the tube. The available volume in a tube intended to hold 3 g of cyanoacrylate adhesive is approximately 5.5 cc. Preferably the inner cylinder does not occupy more than about 29%-30% of this volume.
The inner cylinder is preferably designed so that it can be used to support the walls of existing standard metal tubes. In an alternative embodiment a laminated sheet material comprising metal and plastics material may be used to form the tube such that the metal forms the outer cylinder and the plastics material forms the inner cylinder.
A resilient support means in accordance with the invention converts a metal tube (having the desired barrier properties) into a resilient package which eliminates unwanted material being dispensed by spontaneous emission with resultant wastage and risk of contaminating surfaces, which is an especially important consideration when reactive materials such as cyanoacrylate adhesives are involved.
Suitable inner cylinders can be added to existing metal tubes during tube manufacture, or by a manual or automatic operation prior to filling.
The exact degree of springiness required can be defined by changing the material and/or shape of the inner cylinder. The package of the invention permits material to be dispensed in discrete drops from the metal tube. This is a significant advance in safety when using reactive adhesives such as cyanoacrylates. This safety factor applies to both thixotropic grades and conventional low viscosity cyanoacrylatte products and other materials.
In addition, with thixotropic materials, the package permits or induces suck-back of material from the nozzle area when finger pressure is released. This event reduces or eliminates blockage of the narrow nozzle area which can occur by setting up of materials, especially adhesives, and therefore facilitates frequent re-use of the package.
One embodiment of the invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic longitudinal cross section of the packaging tube before crimping,
Fig. 2 is a cross section on the line A-A in Figure 3,
Fig. 3 is a longitudinal cross section of the tube after crimping.

As shown in the drawings, a conventional metal tube 1, preferably of aluminium, has a sealed nozzle 2 at the closed end 5 and is initially open at the other end 6 (Fig. 1). A cylindrical plastics sleeve 3 has been inserted into the tube from the open end 6 and pushed to the closed end of the tube. The sleeve extends for approximately two thirds of the length of the tube, from the closed interior end of the tube (i.e. the point where the cylindrical wall terminates and the tube tapers to the nozzle 2) to a point 7 which will be adjacent to the crimping region.
The tube 1 is filled with thixotropic cyanoacrylate adhesive from the open end and crimped at 4 in the usual way, trapping air between the crimp and the contents. When the membrane sealing the end of the nozzle 2 is pierced and finger pressure applied to the body of the tube, it is found possible to dispense discrete drops of adhesive without wastage due to oozing. This satisfactory event is brought about by the presence of the internal sleeve insert which is so designed that the package regains its original shape after finger pressure is released. This phenomenon is achieved by the sleeve insert acting as a spring which maintains the shape of the tube.
While the crimped package still contains pressurised air, spontaneous emission of material does not occur when the nozzle membrane is pierced but only when the body of the tube is in addition deformed by finger pressure. The internal insert sleeve prevents the occurence of the permanent deformation and therefore avoids spontaneous emission of adhesive even in the presence of compressed air.
The following examples further illustrate the invention.

EXAMPLE 1

An aluminium tube of length 62 mm and internal diameter 13.6 mm was fitted with an insert consisting of a plastic cylindrical sleeve of length 40 mm, external diameter 13.0 mm and wall thickness 1 mm. The tube was then filled with 3g. of thixotropic cyanoacrylate adhesive and the open end crimped. The nozzle was then pierced to allow adhesive to be dispensed by applying finger pressure to the body of the tube. It was found that adhesive only dispensed when finger pressure was applied and ceased instantly on release of finger pressure. The adhesive was also observed to be sucked back or withdrawn from the nozzle area.
A control aluminium tube of identical dimensions was filled with thixotropic grade cyanoacrylate as above but without inclusion of the insert. On piercing the nozzle and applying hand pressure to dispense the adhesive, it was observed that adhesive continued to ooze from nozzle for several minutes after finger pressure was released.

EXAMPLE 2

Strips of acetate film (as used to make photocopier slides) of width 40 mm and lengths 30, 50, 70 and 100 mm were prepared. The various lengths of film were then rolled to fit the open end of 62 mm x 13.0 mm diameter aluminium tubes. As the roll of film was under tension, it expanded to conform with the interior of the tube. The tubes were then filled with 3g. of thixotropic grade cyanoacrylate adhesive and crimped in the normal way. The nozzles were then pierced and finger pressure applied to the tube to express the adhesive. Results with the various length of acetate film were as follows:
These results show that with the appropriate length of film, sufficient to define a resilient cylinder within the tube, the desired properties can be obtained.
The invention is not limited to the specific embodiments described, many of which can undergo considerable variation without departing from the scope of the invention.

Claims

1. A packaging tube for dispensing liquid materials comprising:-

an outer hollow cylinder (1) having a closed end (6) and a dispensing end (5), said dispensing end (5) comprising a tip means (2) to dispense material from said packaging tube, said outer hollow cylinder being made of a ductile material, characterised by an inner hollow cylinder (3) located within said outer cylinder (1), said inner cylinder (3) being made of an elastic material, said inner cylinder (3) being located adjacent said outer cylinder (1) and containing the material to be dispensed, whereby upon compression of the outer cylinder (1) the inner cylinder (3) is compressed from its original shape, thereby dispensing material out of the tip means (2), and upon release of compression of the outer cylinder (1) said elastic material of the inner cylinder (3) resumes its original shape and concurrently reforms and retracts nondispensed material contained in said tip means (2).

2. A packaging tube according to claim 1 characterised in that the tip means (2) is adapted for dropwise dispensing of thixotropic or liquid adhesives.

3. A packaging tube according to claim 1 or 2 characterised in that the inner cylinder (3) is a cylindrical sleeve of plastics material.

4. A packaging tube according to claim 3 characterised in that the plastics material is high density or medium density polyethylene.

5. A packaging tube according to claim 3 or 4 characterised in that the sleeve (3) has a wall thickness in the range 0.1 - 1.0 mm.

6. A packaging tube according to claim 5 characterised in that the sleeve (3) has a wall thickness in the range 0.1 - 0.5 mm, especially about 0.2 - 0.25 mm.

7. A packaging tube according to any of claims 3-6 characterised in that the sleeve (3) extends from the closed interior end of the tube to a point (7) adjacent to the crimping region.

8. A packaging tube according to claim 1 or 2 characterised in that the inner cylinder (3) consists of a stainless steel liner.

9. A packaging tube according to claim 1 or 2 characterised in that the inner cylinder (3) is a strip of plastic or spring metal rolled into a cylindrical coil of suitable length and inserted in the outer cylinder (1).

10. A packaging tube according to any of the preceding claims wherein the inner cylinder (3) occupies no more than about 30% of the available volume of the tube.