GB1577934A

GB1577934A - Collapsible tubes

Info

Publication number: GB1577934A
Application number: GB6177/76A
Authority: GB
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1976-02-17
Filing date: 1976-02-17
Publication date: 1980-10-29
Also published as: CA1046027A; NL7701597A; DE2705868A1; AU2227777A; JPS52101189A; CH603422A5; SE7701569L; BR7700968A; ZA77929B; BE851412A; DK66977A; IT1073259B; FR2341496A1

Description

(54) IMPROVEMENTS IN OR RELATING TO COLLAPSIBLE TUBES (71) We, UNILEVER LIMITED, a company organized under the laws of Great Britain, of Unilever House, Blacltfriars, London E.C.4, England, do hereby declare the invention for' which we 'pray that a patent may be granted to us and'the method by which it' is to be performed, to be .particularly described in and by the follow ing statement: This invention relates to improvements in or relating to collapsible tubes for dispens ing toothpaste, 'salves, creams and the like and particularly to a collapsible tube of flexible plastics material.

The replacement of the conventional tube of lead, tin and other ductile materials by a tUbe of flexible plastics material has been inhibited by the problem that after a quanti ty of the contained material has been squeezed out the material at the tube outlet is sucked back into the tube as the squeezing pressure on the tube body'is released. This so-called "suck-back" problem gives rise to difficulties both to the user and for the contained material itself due to the entry of air into the tube as it is emptied.

Conventionally collapsible tubes are sea led at one end with a transverse flat seal and are provided at the other end with a circular head having the circular portion secured within thebody.df the tube and an annular shoulder portion tapering' inwardly away from the tube body to an outlet which can be closed, for example. bqi ,a'threaded cap.

The diameter of the:circular portion is of course. one of' thel'pa'rarrilters determining the volume of the tube but th'is circular portion also' r'ntakes it difficult to expel the last of the contained material. particularly when the body is of flex'but plastics material and cannot be rolled up; as can a tube of ductile material.

'.It has been propdsed to provide the tube with an el tical head, that is a' head in which the skirt portion which is secured to the tube body is elliptical. This minimises the problem of expelling then last of the contained material. Such an elliptical head when used with a body of flexible plastics material gives however a reduced volume for a given area of the flexible plastics material as compared to the use of a circular head because of the generally flattened cross-section of the tube body.It is of course possible to fill such a tube having . an elliptical head under pressure to achieve a greater volume of contained material but this is unacceptable to the user-since the contained material would be expelled by the pverpressure on. opening the tube.

It is therefore an obJect of the present invention to provide a collapsible tube of flexible plastics material which minimises both the problem of suck-back and that of squeezing out the entire contained material without unduly reducing the contained volume.

According to the present invention there is provided a collapsible tube having a tubular body portion of flexible plastics material closed at one end by a transverse flat seam and provided at the other end with a head having a skirt portion secured within the body portion, the skirt portion having an oblong shape with a major axis aligned with the transverse flat seam and a minor axis transverse thereto, the body portion being provided with two longitudinal preformed crease lines each extending from a respec tive one of the ends of the major axis to a respective one of the ends of the transverse 'flat seam and two pairs of curved preformed crease lines, each. pair extending generally lengthwise of the body -one on either side of a respective one of the longitudinal crease lines with both ends of each curved crease line joining the respective longitudinal crease line and the curved crease lines defining at the location ,where they ,are spaced most distant from their respective longitudinal creases a rectangular transverse cross-section of the filled body having an area greater than the transverse crosssectional area of the body at the head.

The curved crease lines in the tube according to the present invention enable the tube body to be gradually collapsed from the filled condition as the contained material is squeezed out. This is because the curved lines define a pre-determined filled shape of the body and when the body is squeezed from this shape towards the empty or flattened condition the shape of the body is determined by the longitudinal crease lines and the shape and size of the head.

In the filled condition the body portion of the tube takes up a shape defined by the curved crease lines, the body wall between each of the two curved lines which join one of the longitudinal crease lines when viewed in a transverse plane being a substantially straight line. As the contained material is reduced this substantially straight line becomes a "V" shaped line having one of the longitudinal creases at its apex, the longitudinal crease lines at each side of the tube progressively moving outwards reducing the included angle of the "V" as the quantity of contained material reduces. The curved crease lines allow this flattening of the body to take place from the flat seam at the base of the tube progressively towards the head.

In that the head is not circular in crosssection where it fits the body portion squeezing out of the last of the contained material is facilitated since the free state of the empty tube is inherently more flattened that if the head was circular. Nevertheless the volume of the tube in the full condition, and in which the contained material is not subject to pressure from the tube tending to collapse, is increased for a given area of body material by reason that the body portion has a maximum cross-sectional area greater than that of the head.

The curved crease lines are preferably arranged symmetrically about the longitudinal crease lines and advantageously join the longitudinal crease lines at the intersection of the latter with the transverse flat seam at one end of the body and at the intersection with the innermost edge of the skirt portion of the head at the other end of the body.

In order that the tube has a maximum volume it can be provided that at location where the curved crease lines are spaced most distant from the respective longitudinal crease lines the transverse cross-section of the filled body is a square.

The invention will now be more particularly described with reference to the drawing accompanying the provisional specification in which Figure 1 shows a front view of a collapsible tube in the fully filled condition; Figure 2 shows a side view of the tube of Figure 1; Figure 3 shows a plan view from above of the tube of Figure 1; Figure 4 shows a transverse cross-section along the line IV-IV of Figure 2; Figure 5 shows the tube of Figure 1 in a partially empty condition; Figure 6 shows a cross-sectional elevation of the tube of Figure 5 similar to Figure 4; and Figure 7 shows the side view of the tube of Figure 1 almost empty.

Referring to Figures 1 to 4 there is shown a collapsible tube having a body portion 1 of polypropylene film 300 micron thick and an injection moulded head 2 of plastics material. The head has a skirt portion 3 which is secured within the body portion 1, the body portion abutting with a shoulder 4 defining one end of the skirt. The skirt has an oblong shape having a major axis 5 and a minor axis 6 with a curved profile extending symmetrically about the major axis. The intersections of the curved profile with the major axis are substantially points at 7.

From the shoulder 4 the head has an inwardly sloping shoulder portion 8 terminating in an outlet 9 threaded at 10 to receive a closure cap (not shown). The length of the minor axis 6 of the skirt is determined primarily by the size of the outlet and the closure cap, the length of the minor axis being kept as small as practical.

The body portion is closed at the end opposite the head by a transverse flat seam 11 parallel with the major axis of the head.

From each end of the flat seam longitudinal pre-formed crease lines 12 extend the length of the body portion to the ends 7 of the major axis of the head. From positions 14 just below the innermost edge 13 of the skirt portion of the head 4 curved pre-formed crease lines 15 extend from the longitudinal crease lines, two curved crease lines being associated with each longitudinal crease line. The curved crease lines 15 are symmetrical about their respective longitudinal crease lines and curve away from the longitudinal crease lines towards the mid point of the body length and then curve back to meet the intersection af the respective longitudinal crease lines with the transverse flat seam thereby defining with the longitudinal crease lines body side wall portions 16 and 17. The maximum distance 18 which the curved lines are spaced from the longitudinal crease lines lies substantially mid-way along the body and is greater than one half of the minor axis 6 of skirt 3 so that at the mid position of a filled tube the transverse cross-section as shown in Figure 4 is a rectangle having an area greater that the area of the skirt.

In the filled condition as shown in Figures 1 to 4 the shape of the. body portion is determined by the curved crease lines 15.

Side wall portions 16 and 17 between the two curved crease lines associated with one longitudinal crease line are substantially aligned with one another as shown in Figure 4 and in this condition the tube is stable so that it ciin contain material. without the contained material being under pressure.

As the tube is squeezed to expel the contained material the side wall portions 16 and 17 collapse outwardly to a "V" shape having the longitudinal crease line 12 at the apex of the "V" as shown in Figures 5 and 6.

In this partially empty condition there is no tendency of the body to revert to the shape of a fully filled container. Moreover, after the side wall portions 17 and 18 together form a "V" shape the preformed crease lines tend to urge the body of the tube gently towards the flattened condition. This minimizes any tendency towards "suck back".

As the tube is further emptied the body takes up a shape shown in Figure 7. The natural tendency of the tube when empty 'its to take up a tapered shape having its widest part determined by the minor axis of the head and tapering from the head towards the transverse flat seam. Thus in the extreme case that the minor axis of the head was nil the natural shape of the tube when empty would be flat with no contained colume. The minor axis of the head is therefore kept as small as possible and it has been found in practice that the natural stickiness of remaining traces of the contained material keep the body walls together in the empty part of the tube as shown at 19 in Figure 7. This stickiness is sufficient to maintain material in the outlet and thus prevent air being sucked back into the tube, the remaining contained material staying at the top of the tube.The generally flattened transverse cross-sectional shape of the head allows substantially all the contained material to be squeezed out and generally assists in keeping the body of the tube in the flattened state to which it has been squeezed.

It will of course also be appreciated that because the sum of the maximum lengths 18 of the side wall portions 16 and 17 associated with one of the longitudinal crease lines is greater than the length of the minor axis of the head the volume of the tube in the stable filled condition is greater than if the curved lines were not present. The maximum volume of the tube is achieved when the maximum length 18 of each of the side wall portions 16 and 17 is equal to th of the transverse peripheral length of the body so that the cross-section of maximum area is a square.

Without the curved lines the tube would have only one stable shape, i.e. tapered from the head to the transverse flat seam similar to that of the tube of the present invention when empty. Such a tube could of course -be filled under pressure with a greater volume of contained material but would result in a large amount ofthe material being expelled as soon as the closure cap was removed. When the contained material is only used in small quantitites at any one time e.g. tooth paste, this is most undesirable.

The body portion of the tube can be made from a flat sheet of the flexible plastics material and the preformed crease lines formed by upsetting the material in any conventional manner. The sheet of material can then be folded along the two longitudinal crease lines and joined by a longitudinal seam (not shown) to form a tube Whilst the described embodiment of the invention has curved crease lines extending symmetrically substantially the entire length of the body portion of the tube it will be clear that other configurations of the curved crease lines can be adopted which provide a tube having a stable condition in the filled condition and having a volume in excess of the volume of a filled tube in the stable condition utilising the same area of material for the body portion but without the curved crease lines.

WHAT WE CLAIM IS: 1. A collapsible tube having a tubular body portion of flexible plastics material closed at one end by a transverse flat seam and provided at the other end with a head having a skirt portion secured within the body portion, the skirt portion having an oblong shape with a major axis aligned with the transverse flat seam and a minor axis transverse thereto, the body portion being provided with two longitudinal preformed crease lines each extending from a respective one of the ends of the major axis to respective one of the ends of the transverse flat seam and two pairs of curved preformed crease lines, each pair extending generally lengthwise of the body on on either side of a respective one of the longitudinal crease lines with both ends of each curved crease line joining the respective longitudinal crease line and the curved crease lines defining at the location where they are spaced most distant from their respective longitudinal creases a rectangular transverse cross-section of the filled body having an area greater than the transverse crosssectional area of the body at the head.

2. A collapsible tube according to Claim 1 in which the curved crease lines are arranged symmetrically about the longitudinal crease lines.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. area of the skirt. In the filled condition as shown in Figures 1 to 4 the shape of the. body portion is determined by the curved crease lines 15. Side wall portions 16 and 17 between the two curved crease lines associated with one longitudinal crease line are substantially aligned with one another as shown in Figure 4 and in this condition the tube is stable so that it ciin contain material. without the contained material being under pressure. As the tube is squeezed to expel the contained material the side wall portions 16 and 17 collapse outwardly to a "V" shape having the longitudinal crease line 12 at the apex of the "V" as shown in Figures 5 and 6. In this partially empty condition there is no tendency of the body to revert to the shape of a fully filled container. Moreover, after the side wall portions 17 and 18 together form a "V" shape the preformed crease lines tend to urge the body of the tube gently towards the flattened condition. This minimizes any tendency towards "suck back". As the tube is further emptied the body takes up a shape shown in Figure 7. The natural tendency of the tube when empty 'its to take up a tapered shape having its widest part determined by the minor axis of the head and tapering from the head towards the transverse flat seam. Thus in the extreme case that the minor axis of the head was nil the natural shape of the tube when empty would be flat with no contained colume. The minor axis of the head is therefore kept as small as possible and it has been found in practice that the natural stickiness of remaining traces of the contained material keep the body walls together in the empty part of the tube as shown at 19 in Figure 7. This stickiness is sufficient to maintain material in the outlet and thus prevent air being sucked back into the tube, the remaining contained material staying at the top of the tube.The generally flattened transverse cross-sectional shape of the head allows substantially all the contained material to be squeezed out and generally assists in keeping the body of the tube in the flattened state to which it has been squeezed. It will of course also be appreciated that because the sum of the maximum lengths 18 of the side wall portions 16 and 17 associated with one of the longitudinal crease lines is greater than the length of the minor axis of the head the volume of the tube in the stable filled condition is greater than if the curved lines were not present. The maximum volume of the tube is achieved when the maximum length 18 of each of the side wall portions 16 and 17 is equal to th of the transverse peripheral length of the body so that the cross-section of maximum area is a square. Without the curved lines the tube would have only one stable shape, i.e. tapered from the head to the transverse flat seam similar to that of the tube of the present invention when empty. Such a tube could of course -be filled under pressure with a greater volume of contained material but would result in a large amount ofthe material being expelled as soon as the closure cap was removed. When the contained material is only used in small quantitites at any one time e.g. tooth paste, this is most undesirable. The body portion of the tube can be made from a flat sheet of the flexible plastics material and the preformed crease lines formed by upsetting the material in any conventional manner. The sheet of material can then be folded along the two longitudinal crease lines and joined by a longitudinal seam (not shown) to form a tube Whilst the described embodiment of the invention has curved crease lines extending symmetrically substantially the entire length of the body portion of the tube it will be clear that other configurations of the curved crease lines can be adopted which provide a tube having a stable condition in the filled condition and having a volume in excess of the volume of a filled tube in the stable condition utilising the same area of material for the body portion but without the curved crease lines. WHAT WE CLAIM IS:

1. A collapsible tube having a tubular body portion of flexible plastics material closed at one end by a transverse flat seam and provided at the other end with a head having a skirt portion secured within the body portion, the skirt portion having an oblong shape with a major axis aligned with the transverse flat seam and a minor axis transverse thereto, the body portion being provided with two longitudinal preformed crease lines each extending from a respective one of the ends of the major axis to respective one of the ends of the transverse flat seam and two pairs of curved preformed crease lines, each pair extending generally lengthwise of the body on on either side of a respective one of the longitudinal crease lines with both ends of each curved crease line joining the respective longitudinal crease line and the curved crease lines defining at the location where they are spaced most distant from their respective longitudinal creases a rectangular transverse cross-section of the filled body having an area greater than the transverse crosssectional area of the body at the head.

3. A collapsible tube according to Claim

1 or Claim 2 in which one end of the curved crease lines join the longitudinal crease lines at the intersection of the transverse flat seam therewith and the other end of the curved crease lines joins the longitudinal crease lines adjacent the intersection therewith of the innermost edge of the skirt portion of the head.

4. A collapsible tube according to any one of the preceding claims in which at the location where the curved crease lines are spaced most distant from their respective longitudinal crease lines the transverse cross-section of the filled body is a square.

5. A collapsible tube substantially as hereinbefore described with reference to the drawings accompanying the provisional spe cification.