GB1594812A

GB1594812A - Containers having screw caps

Info

Publication number: GB1594812A
Application number: GB2672677A
Authority: GB
Original assignee: PEERLESS PLASTICS Ltd
Current assignee: PEERLESS PLASTICS Ltd
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-08-05

Description

(54) IMPROVEMENTS RELATING TO CONTAINERS HAVING SCREW CAPS (71) We, PEERLESS PLASTICS LIMITED, a British Company, of Priory Road, Aston, Birmingham 6, 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 following statement: This invention relates to containers having screw caps and more particularly to such containers which have bodies made of plastics material.

Known containers of the aforesaid kind are generally prone to one or more of the following problems, namely: effective sealing of the screw cap on the container, selfunscrewing of the cap and, because of the flexibility of the plastics material of the body, jumping of the screw cap thread off the thread of the body if the cap is overtightened. These problems are especially prevalent in containers, such as jars, which have shallow screw caps retained on the container bodies by perhaps just one turn of the mating threads.

The present invention seeks to overcome or at least reduce the problems.

According to the present invention there is provided a container which comprises a body of plastics material having an externally screw-threaded neck and a screw cap fitted to the neck, and wherein the neck has an upwardly and inwardly inclined rim and below the screw thread an external, upwardly-facing annular shoulder which is spaced from the rim by a distance corresponding substantially to the depth of the skirt of the cap and the outer diameter of which is greater than the internal diameter of the bottom of the skirt, the arrangement being such that when the cap is fully screwed onto the neck the inner, upper edge of the rim abuts against the crown of the cap and the bottom of the skirt abuts against and wedges on the shoulder which prevents further tightening of the cap.

Preferably the upper edge of the rim is spaced from the shoulder by a distance which is slightly greater than the depth of the skirt, such that the abutting engagement of the rim with the crown of the cap causes the rim to be downwardly deflected. The crown may have a sealing ring applied to it against which the rim abuts. The sealing ring may be wadding, such as paper, or plastics separately inserted and retained in the cap, or moulded in the cap, or it may be of any other suitable form. A satisfactory seal may be obtained without necessarily providing a sealing ring as well.

The abutment of the rim against the crown of the cap helps to seal the connection between the cap and the container, the more so if the rim is caused to be downwardly deflected as then complete seating contact between the cap and rim to produce the seal can more readily be obtained. Abutment of the skirt of the cap against the shoulder prevents the cap from being over-tightened so that the thread of the cap cannot jump off the thread of the neck. Furthermore the wedging action between the skirt and the shoulder resists self-release of the cap from the neck.

The shoulder may be formed by a flank of an annular bead or rib on the neck. At least when so formed the provision of the shoulder has the added advantage that it strengthens the neck against possible distortion. The should may be of other forms. It may slope downwardly, in a curve or in a straight line, or it may be in a plane normal to the axis of the neck.

The threads of the neck and cap may be of any convenient form.

An embodiment of the invention as applied to a jar having a shallow screw cap will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a fragmentary section through the neck of the jar, and Figure 2 is a similar section but showing the screw cap fitted on the neck.

The jar is blow moulded from a plastics material, preferably of the polyethylene group but other thermoplastics may be used.

Its neck 1 is formed with a standard, half round, external bottle thread 2 which extends through approximately two convolutions. A rim 3 of the neck 1 comprises an inwardly and upwardly inclined annular flange. The rim 3 as illustrated is inclined at approximately 15 to the horizontal but it may be inclined at another angle if desired. In general an inclination of between 5"--40" is the most satisfactory. We have found that in practice 3 mm to 8 mm is a generally suitable width for the rim to minimise the effects of any distortion in the rim from the moulding process but again in some instances other widths may be more appropriate. Below the thread 2 the neck 1 is shaped to form a continuous external, annular bead 4 of rounded section. The bead 4 projects further than the thread 2.An upwardly facing flank of the bead 4 defines a shoulder 5.

The cap, which is generally indicated by reference 6, is of conventional construction made from metal or plastics. It has a crown portion 7, on the inside surface of which is a sealing ring 8 of known form of a suitable resilient material, and a skirt portion 9 in which there is a single convolution of a thread 10 complementary to the thread 2 on the neck. Thc skirt portion 9 is rolled over outwards at its bottom 11. The depth of the skirt is substantially equal to the vertical distance between the shoulder 5 an the inner, upper edge of the rim 3. The sealing ring 8 may be omitted.

The outer diameter of the bead 4, and thus of the shoulder 5, is greater than the internal diameter of the bottom 11 of the skirt.

The cap 6 screws onto the neck until the bottom II abuts against the shoulder 5, as shown in Figure 2. Before the bottom meets the shoulder, the inner edge of the rim 3 is engaged by the sealing ring 8, which causes the rim to be deflected downwards as the cap is tightened further. The inner edge presses into the sealing ring. Thus a good seal is produced between the neck and the cap.

Further tightening of the cap is prevented when the bottom 11 abuts against the shoulder. Because of the downward inclination of the shoulder. a wedging action occurs between the skirt and the shoulder as the bottom 11 is tightened onto the shoulder, and that action serves to restrain the cap from unscrewing of its own accord from the neck.

The bead 4 strengthens the neck to resist distortion of the neck as the cap is tightened.

The rim also has a strengthening effect on the neck.

It will be appreciated that the invention is applicable not only to containers having shallow caps but to containers having deeper caps as v 11.

WHAT WE CLAIM IS: 1. A container which comprises a body of plastics material having an externally screw-threaded neck, and a screw cap fitted to the neck, and in which the neck has an upwardly and inwardly inclined rim and below the screw thread an cxlcrnalz up wardly-facing annllllr shoulder which is spaced from the rim by a distance corresponding substantially to the depth of the skirt of the cap and the outer diameter of which is greater than the internal diameter of the bottom of the skirt, the arrangement being such that when the cap is fully screwed on to the neck the inner, upper edge of the rim abuts against the crown of the cap and the bottom of the skirt abuts against and wedges on the shoulder which prevents further tightening of the cap.

2. A container according to claim 1 wherein the upper edge of the rim is spaced from the shoulder by a distance which is slightly greater than the depth of the skirt such that the abutting engagement of the rim with the crown of the cap, when the cap is fully screwed on to the neck, causes downward deflection of the rim.

3. A container according to claim 1 or claim 2 wherein the rim is inclined upwardly and inwardly at 5"--40" to the horizontal.

4. A container according to claim 3 wherein the rim is inclined upwardly and inwardly at 15 to the horizontal.

5. A container according to any preceding claim wherein the rim has a width of 3 mm to 8 mm.

6. A container according to any preceding claim wherein the shoulder is formed by a flank of an annular bead or rib on the neck.

7. A container according to any preceding claim wherein the shoulder slops downwardly.

8. A container according to any of claims I to 5 wherein the shoulder is in a plane normal to the axis of the neck.

9. A container substantially as described herein with reference to and as illustrated by the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the neck of the jar, and Figure 2 is a similar section but showing the screw cap fitted on the neck. The jar is blow moulded from a plastics material, preferably of the polyethylene group but other thermoplastics may be used. Its neck 1 is formed with a standard, half round, external bottle thread 2 which extends through approximately two convolutions. A rim 3 of the neck 1 comprises an inwardly and upwardly inclined annular flange. The rim 3 as illustrated is inclined at approximately 15 to the horizontal but it may be inclined at another angle if desired. In general an inclination of between 5"--40" is the most satisfactory. We have found that in practice 3 mm to 8 mm is a generally suitable width for the rim to minimise the effects of any distortion in the rim from the moulding process but again in some instances other widths may be more appropriate. Below the thread 2 the neck 1 is shaped to form a continuous external, annular bead 4 of rounded section. The bead 4 projects further than the thread 2.An upwardly facing flank of the bead 4 defines a shoulder 5. The cap, which is generally indicated by reference 6, is of conventional construction made from metal or plastics. It has a crown portion 7, on the inside surface of which is a sealing ring 8 of known form of a suitable resilient material, and a skirt portion 9 in which there is a single convolution of a thread 10 complementary to the thread 2 on the neck. Thc skirt portion 9 is rolled over outwards at its bottom 11. The depth of the skirt is substantially equal to the vertical distance between the shoulder 5 an the inner, upper edge of the rim 3. The sealing ring 8 may be omitted. The outer diameter of the bead 4, and thus of the shoulder 5, is greater than the internal diameter of the bottom 11 of the skirt. The cap 6 screws onto the neck until the bottom II abuts against the shoulder 5, as shown in Figure 2. Before the bottom meets the shoulder, the inner edge of the rim 3 is engaged by the sealing ring 8, which causes the rim to be deflected downwards as the cap is tightened further. The inner edge presses into the sealing ring. Thus a good seal is produced between the neck and the cap. Further tightening of the cap is prevented when the bottom 11 abuts against the shoulder. Because of the downward inclination of the shoulder. a wedging action occurs between the skirt and the shoulder as the bottom 11 is tightened onto the shoulder, and that action serves to restrain the cap from unscrewing of its own accord from the neck. The bead 4 strengthens the neck to resist distortion of the neck as the cap is tightened. The rim also has a strengthening effect on the neck. It will be appreciated that the invention is applicable not only to containers having shallow caps but to containers having deeper caps as v 11. WHAT WE CLAIM IS:

1. A container which comprises a body of plastics material having an externally screw-threaded neck, and a screw cap fitted to the neck, and in which the neck has an upwardly and inwardly inclined rim and below the screw thread an cxlcrnalz up wardly-facing annllllr shoulder which is spaced from the rim by a distance corresponding substantially to the depth of the skirt of the cap and the outer diameter of which is greater than the internal diameter of the bottom of the skirt, the arrangement being such that when the cap is fully screwed on to the neck the inner, upper edge of the rim abuts against the crown of the cap and the bottom of the skirt abuts against and wedges on the shoulder which prevents further tightening of the cap.