GB2288390A

GB2288390A - Screw cap for container

Info

Publication number: GB2288390A
Application number: GB9413414A
Authority: GB
Inventors: Harold Birkett
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-04-15
Filing date: 1994-07-04
Publication date: 1995-10-18
Anticipated expiration: 2014-07-04
Also published as: GB9412889D0; GB9412180D0; GB9413414D0; GB9407501D0; GB9412314D0; GB2288390B

Abstract

A cap screws onto a container in less than half a turn with pins 6 carried on the cap engaging between screw threads 5 provided on the container, the threads being variably pitched to give a decreased final angle of pitch along length 13. Slots 7 may be provided in the underside of the threads such that if the container holds a carbonated beverage the pressure of gases escaping from the beverage imparts an upward force to move pins into slots 7. An undulating profile on the lower thread may also be provided to lift the cap and give increased pressure release (17, Fig. 7). The cap may be childproof and include two additional shorter pins 14, the cap being pressed inwardly at the region of these pins to allow the other pins to ride over chamfered obstructions, (16, Fig. 5). Part of the threads 18 may bend when overstressed to form a barrier above the pins 6 to hold the cap captive, (Fig. 1, Sect. D-D). The cap may include a continuous tamper evident band or four bands which are retained on the cap after opening. The container may contain liquids, powders, or pharmaceutical tablets. The cap may be profiled for easy gripping (Fig. 8), the pressure release passages formed in such a cap providing both horizontal and vertical pressure force components. <IMAGE>

Description

NEW CLOSURE FOR PRESSURE AND NON-PRESSURISED CONTAINERS.

This invention relates to a closure for most types of containers, pressurised or non-pressurised, containing liquids, powders, tablets, pharmaceuticals or any other product where a screwed or other type of cap closure is normally used which will fulfil the following requirements;-.

1. Form a perfect seal 2. Be removed by hand as easily as possible especially when used by the old, young and infirm, who may be tempted to use mechanical means with the potential of shearing the threads especially through turning the cap clockwise.

3. Prevent missiling, which may result in possible injury for someone in the case of gaseous liquids, carbonated beverages especially those contained in PET bottles for an example, the full force of the trapped gasses being released instantly resulting in the cap being propelled at high velocity.

4.. Prevent large tail end blow off with gaseous liquids, carbonated beverages especially those contained in PET bottles for an example.

5. Be child proof when used for pharmaceuticals and domestic caustic substances and also have high quality safety for industrial use.

6. Can be resealed easily and effectively.

The material of construction can be plastic or any other material to suit and manufactured using state of the art technology.

Existing state of art pressurised screwed capped containers ( carbonated mineral water containers for an example ) have pressure relief slots inside extending from the top to the bottom of the cap or container threaded portion parallel to the axis of the container. These caps are made so that they can't be unscrewed in less than two movements to allow sufficient time for the pressure to reduce irrespective of if the pressure is too high or not, this is primarily to avoid tail end blow off and to a lesser degree the cap nissiling, the threaded portion having an angle of pitch to suit the axial component force required for an effective seal and length to give the required number of turns to open the closure and to give the required shear strength.

According to the present invention the closure satisfies the above requirements such that it provides the following advantages and increased safety over state of art closures: See typical example Fig 1.

1. Cap 1, is screwed onto container 2, in less than half a turn, with the required closure pressure against seal 10, being achieved due to the required sealing vertical component force exerted onto threadpins 6, by the decreased final angle of pitch 9, along length 13, of variable pitched threads 5.

2. The cap is unscrewed more easily from the container in less than a quarter of a turn yet will resist the high forces created when the cap is inadvertently tightened up by mechanical means due to the threadpins 6, being forced to the end of there travel lengths 13, and the mechanical force being resisted by the direct and nearly opposite reactive forces of thread profiles 5.

The threads of state of the art screwed closures can be sheared off due to the much higher shear forces caused by the resulting component force exerted between the mating threads bearing surfaces this shear force being equal to the applied mechanical force multiplied by the cosec of the pitch angle i.e. the finer the pitch the higher the shear force, taking a pitch angle of 2.5 degrees for an example would give a resulting component force 23 times greater than the applied mechanical force which means that the total effective shear area of the screw threads have got to be 23 times greater than the total shear area of the screw pins for the same strength.

3 The rare occurrence of a cap missiling as previously described will be prevented by the resistance to shear of the threadpins 6, see section C-C, due to the better quality control in manufacture inherent with this method and will not suffer fran the occasional poorly fitting threads during manufacture due to inherent difficulties with quality control when manufacturing large quantities of state of art threaded closure.

In the event that even this is not sufficient then the sacrificial shear piece means 18, are mede sufficiently weak in shear area so that they peel away under the pressure of the threadpins 6, see developed section D-D, in such a manner that each forms a barrier above in the space between the adjacent variable pitched threads 5, creating a continuous barrier which allows the screw pins 6, to pass under resulting in a captive cap.

4. If the pressure of the escaping gasses is too high the cap is impeded or prevented from being unscrewed further by the upwards pressure on the underside of the top of the cap 1, imparting an upwards force and movement to attached thread/pins 6, into slots 7, profiled and positioned to suit, on the underside of variable thread profile 5, where they are held captive until the pressure from inside the container reduces sufficiently to allow the captive pins to be released allowing the cap to be unscrewed completely.

5. See Fig 3, 3A, 4 and 5. This captive type of cap would be used for child proof closures and also as an additional safeguard for caustic and other toxic substances.

The cap is screwed onto the container in less than half a turn with thread/pins 14 and 15, riding over chamfered obstructors 16.

The cap is unscrewed from the container in less than a quarter turn the outside of the cap being pressed inwards at diagonally opposite positions marked on the cap located over the two shorter chamfered end thread/pins 14, resulting in the plain end of longer thread/pins 15, moving radially outwards thus being able to slide/ride over chamfered obstructions 16, when the cap is turned sufficiently to allow chamfered thread/pins 14, to slide/ride over the other two remaining chamfered obstructions 16, thus allowing the cap to be completely unscrewed.

This child proofing invention is an improvement over existing state of art because the thread pin is part of and integral with the child proofing.

6. Can be resealed more easily and effectively with less than half a turn using less effort due also to the more user friendly profiles, shown in Figs 8 to 11, when used.

See Fig 2, dimension 11, which is a function of stress angle 12, will increase proportional to the pressure contained this being in order to prevent deflection and leakage along mating surface of cap with seal 10.

The number of thread profiles 5, with pin/threads 6, spaced around the container will be two or more but is not restricted in number, size or shape to those illustrated being examples only there being others to suit the various requirements and types of container used which will perform the functions required using the invention described including having pins on the container and threads inside the cap for an example.

It may be that serrated or notched or undulating profiled mating surfaces are used for an example to impede the removal of the cap under excessive pressure.

It may be that the profile of the threadpins are elongated or rectangular or sane other empirical size and shape to suit the stresses imposed and other requirements of the closure the ones shown being examples only.

There are varied combinations and modifications of methods described which may be used to suit the requirements of the closure and the manufacturing processes using this invention.

Fig 3, shows a plan section B - B similar to Fig 1, but modified to be a captive closure.

Fig 3A, has square ended pins 14, which clear obstructors 16, when cap is unscrewed. This arrangement requires increase in depth of variable thread profile 5.

Fig 4, shows developed section C - C for non-pressurised closure.

Fig 5, shows developed section C - C for pressurised closure also showing serrated or undulating mating surface for increased retention of tamper evident band.

The following are variations with open ended threads: Fig 6, shows developed section C - C for non-pressurised closure.

Fig 7, shows another example of a developed section C - C for a pressurised closure with an undulating thread profile 17, which lifts the cap up and down resulting in increased pressure relief prior to the threadpins being released from captive slots 7, and the cap unscrewed.

The positions and shapes of the obstructors 16, will be to suit the requirements of the closure.

Fig 8, shows a cap where the gasses ejected through the passageways formed around the exterior are directed in such a manner that the horizontal component reactive forces acting upon the cap are clockwise and offer resistance to the cap being unscrewed this resistance being in proportion to the pressure whilst their vertical component reactive force will act as previously described and shown in Fig 1.

The profile of this cap also makes it more user friendly and is such that it is easier to grip, unscrew and tighten with less effort whilst still achieving the required sealing pressure.

Fig 9, shows an example of cap used for a pressurised closure with continuous tamper evident band.

Fig 10, shows an example of a cap with captive closure similar to that shown in Figs 3 and 5, with four tamper evident bands around, the bands being retained by the cap after opening the container Fig 11, shows conventionally screwed cap closure but with passageways formed around the exterior as shown which perform the same functions as described in Fig 8. This vent profile may also be used without projecting outside the outside diameter of the cap it being formed with sufficient depth inside the cap screw threads Any combination of the methods and construction described can be used to suit the requirements of the closure used.

Claims

CLAIMS.

1. A closure for pressurised or non pressurised containers comprising at least two variable pitch threads on container with mating threadpins inside the cap to suit so that the cap is able to be screwed onto the container in less than one turn and off in less than half a turn.

2. A closure as claimed in Claim 1, where the required axial sealing pressure exerted between the thread and threadpins is a function of and is controlled by the decreased final angle of pitch of the variable pitch threads.

3. A closure as claimed in Claim 1, which when due to the cap being inadvertently tightened will resist high thread component shearing forces due to these forces being opposed by the opposite or nearly opposite radial reactive forces of the thread profile at the end of variable pitch threads and not by the much greater axial component force upon the thread due to the angle of the thread.

4. A closure as claimed in Claim 1, where the variable pitch threads are by moulding means made to shear off and bend when over stressed in such a manner so as to form a barrier above the screw pins and make the cap captive on the neck of the container thus preventing the cap missiling.

5. A closure as claimed in Claim 1, whereby if the pressure of the escaping gas is too high when the cap is unscrewed it is impeded or prevented from being unscrewed further by the upwards movement imparted by this pressure onto the cap and thread pins which are pushed into slots on the underside of the variable thread profiles located around the neck of the container and held captive until the pressure from inside the container reduces sufficiently to allow the captive thread pins to be released thus allowing the cap to be unscrewed completely.

6. A closure as claimed in Claim 1, or Claim 5 where gas pressure relief passageways formed around the exterior are directed in such a manner that the horizontal component reactive forces acting upon the cap are clockwise and offer resistance to the cap being unscrewed proportional to the gas pressure.

7. A closure as claimed in Claim 1, where the variable thread upper profile is undulating which lifts the threadpins and cap up and down whilst being unscrewed thus releasing gas pressure prior to the threadpins being released from the captive slots when the cap can be fully unscrewed.

8. A closure as claimed in Claim 1, which is made child-proof by preventing the cap being removed until the diagonally opposite sides of the cap located over two shorter chamfered end thread pins are pressed resulting in the plain ends of longer thread pins located at right angles moving radially outwards thus being able to move then slide over chamfered obstructions whilst the chamfered thread slide over the other two remaining chamfered obstructions.

9. A closure as claimed in Claim 1 or Claim 8, where the thread pin means are integral with and also act as child proofing means.

10. A closure as claimed in Claim 1, where a tamper evident band means is divided into separate sections which remain attached to the cap after being unscrewed from the container.

11. A closure substantially as described herein with reference to Figures 1 to 10 of the accompanying drawings.