Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
  • B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
  • B65D41/04—Threaded or like caps or cap-like covers secured by rotation
  • B65D41/0407—Threaded or like caps or cap-like covers secured by rotation with integral sealing means
  • B65D41/0428—Threaded or like caps or cap-like covers secured by rotation with integral sealing means formed by a collar, flange, rib or the like contacting the top rim or the top edges or the external surface of a container neck
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
  • B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
  • B65D41/04—Threaded or like caps or cap-like covers secured by rotation
  • B65D41/0435—Threaded or like caps or cap-like covers secured by rotation with separate sealing elements
  • B65D41/0442—Collars or rings

Definitions

• the present invention relates to closure caps for screw-threaded containers and in particular to internally screw-threaded caps for glass or plastic bottles, the caps being moulded from a thermoplastic material.
• the caps of the invention are primarily intended for retaining substantial gas pressure within the bottle, for example, pressures up to 160 p.s.i. as are sometimes encountered in carbonated beverages and pasteurised beverages, such as beer.
• the caps may also be employed for vacuum retention or non-pressurised containers.
• thermoplastic pressure-retaining bottle caps comprising an internally screw-threaded body and an integral gasket, composed of one or more flexible ribs which bear against the surface of the neck of the bottle.
• a cap for an externally screw-threaded container comprising a thermo ⁇ plastics outer shell, having a top and a skirt, formed with internal thread formations and an .inwardly directed rib located between the upper end of the thread formation and th top of the shell, and to form in situ a p.v.c. plastisol liner, covering the whole underside of the top of the closur and forming a thickened annulus occupying the annular space between the rib and the top of the shell.
• the present invention provides a closure cap, having a shell moulded in a tough thermoplastics material having a top panel and an internally threaded skirt, an inwardly directed lip on said skirt between the top panel and the skirt thread and having an internal diameter less than the nominal external -.11- diameter of the sealing surface on the container for which it is designed, a downwardly extending rib on the top panel dimensioned to fit within the mouth of such container and a liner, formed of a more compressible material than said tough thermoplastics material, located in the recess between said lip and said rib, the inner rib preferably has an axial extent less than the distance between the top panel of the shell and the inner edge of the inwardly extending lip.
• the liner is preferably a cured plastisol. In any event the liner material may be a foamed material to render it more readily compressible.
• a lined thermoplastics cap of the present invention there is no liner on the central area of the top panel and accordingly there is no risk of "ballooning".
• the essentially annular liner can be formed by depositing a flow- able plastisol into the recess between the lip and the rib and, after spinning the upturned cap to cause centrifugal flow of the liner material, the plastisol may be cured in situ by micro-wave radiation.
• the liner material may be introduced in molten form and may in addition be a foamed material. Such molten material may be injected into the recess in the closure shell and spun out to form a liner which sets on cooling.
• the plastisol In a closure of the present invention the plastisol
• the plastisol (or other lining material) may be injected into the annular recess between the lip and the rib while the closure is turned slowly relatively to an injection nozzle (thus the nozzle(s) may orbit in relation to a stationary closure shell).
• the duration of the plastisol injection is such that the shell and nozzle(s) turn relatively through slightly more than a whole number of revolutions during the injection of plastisol, so that there is no local redudction in thick ⁇ ness of the plastisol " layer. In practice it is not possible to time the plastisol injection precisely to coincide with a whole number of revolutions of the shell and consequently a
• OMPI slight local thickness of the liner at one position is accepted. However that is not found of much significance. The extent of the local thickening may however be kept small by dispensing the plastisol during two or more revolutions of the shell. Even the relatively slow rotation of the shell leads to some centrifugal flow of the dispensed plastisol and it is possible to charge more plastisol to the annular space between the ribs than would be possible (with ⁇ out overflow) if the shell was stationary. After dispensin the plastisol the rate of rotation of the shell may be increased to increase the centrifugal action on the plastiso before it is cured.
• a variety of expedients may be employed alone or together for this purpose.
• a further expedient is to apply some local roughening or patterning to the undersurface of the top panel of the shell between the ribs.
• the liner is sometimes found to be preferable to allow the liner to turn in the shell so as to avoid skidding ' on the container sealing surface(s).
• the surface on the shell, contacted by the liner is made as smooth as possible and may be coated with a slip agent to lower friction between the liner and the shell.
• the shell of a closure in accordance with the present invention is therefor preferably designed so that, in section, the surfaces of the lip and the rib are rounded and also the surface at the spac between them. This assists not only the avoidance of the formation of cracks in the moulded shell, but also in the easy spread of the plastisol within the liner space in the shell and in particular it greatly reduces the risk of en- trapment of air between the retaining rib and the panel top during outward spreading of the plastisol.
• closure shells from a tough, but somewhat resilient plastic, such as polypropylene
• the closure shell should be constructed so that when exposed to the pressures commonly occurring with carbonated beverages, the amount of lifting of the top panel of the closure in the area where the liner lies is minimised. Any lifting of the top of the closure is accompanied by local extension of the shell plastic. It is therefore preferred to reinforce the peripheral region of the shell top against radial stress.
• the liner of a pressure-retaining plastic cap requires to seal 5 both with the top end of the bottle and with a cylindrical or conical side sealing surface surrounding the mouth of the bottle and lying above the neck threads (also with the radiused corner lying between the side sealing surface and t top end surface of the bottle).
• the thickness of the liner material in the location for sealing with the top end surface should be more controllable than is readily achieved when the liner is formed by placing a shot of plastisol centrally of the closure, distributing it over the 15 top panel of the closure by centrifugal action and curing it
• a closure of the present type is screwed down firmly onto a standard container, the mouth portion of the container neck bites into the soft cured plastisol which 20 flows locally to a.limited extent -to enable the formation of a seal between the container and the closure, extending, in the radial direction, over at least a major part of the top end surface of the container, round the radiused corner to the side sealing surface.
• the lip Since the internal diameter of the lip is slightly smaller than the neck of the bottle, the lip is slightly bent upwards and is restrained from being bent downwardly by reason of its contact with the bottle neck. The lip thus forms a strong barrier to downward flow movement of the liner 30. material when the cap is tightened down. This effect may be further accentuated by shaping the lip so that its under- surface slopes slightly downwardly towards the axis of the shell. Plastic flow of the liner material is thus confined within the space bounded by the relatively rigid top and 35 skirt of the shell and the lip, having its free edge supported by the neck of the bottle. With this arrangement the amount of liner material required to form the desired efficient pressure seal is low.
• the liner material By reason of the confined lower margin of the body of liner material, the liner material will flow in a peripheral direction to make good - any irregularity in the shape of the side sealing on the container neck. It also has the further advantage that the vertica extent of the side seal is controlled and the seal between cap and bottle is vented after a predetermined turn of the cap on the bottle thread.
• the vertical distance between the lip and the top which is a major facto in determining the vertical extent of the side seal between the cap and the bottle, is preferably in the range of 1.5 to 2.5 mm, measured between the inner margin of the lip and the closure top.
• the upper surface of the liner-retaining lip is preferably also sloped slightly downwardly (towards the open end of the cap) at an angle, for example, of up to 15 but more preferably in the range of 3 - 7 .
• the inner diameter of the lip is then preferably chosen to be slightly less than the minimum permissible diameter of the sealing surface on the bottle which the cap is designed to fit. There are in fact well recognised ranges of tolerances for the sealing surfaces of standard bottle neck finishes.
• the external diameter of the inner rib is preferably slightly less than the minimum permissible internal diameter of the container mouth, so as to hold the internal rib clear of contact with the inside of the neck.
• the vertical extent of the inner rib is conveniently in the range of 1.0 - 1.5 mm, its size being essentially controlled by the amount of plastisol to be contained.
• Screw-threaded pressure-holding closures in accordance with the invention are primarily intended for application to standard bottles for carbonated beverages.
• Well known examples of such standard bottles have external neck diameters of 26 mm, 28 mm, and 38 mm respectively.
• Figure 1 illustrates one form of closure cap in accordance with the invention
• Figure 2 illustrates a further form of closure cap in accordance with the invention
• Figure 3 illustrates two forms of a further development of the closure cap of the present invention
• Figure 4 illustrates the two forms of caps, shown in Figure 3, when fitted to appropriate forms of container.
• the caps of Figures 1 and 2 comprise a moulded polypropylene shell having a top 1 and a skirt 2.
• the skirt 2 of the cap shell has an internal thread formation 3 and vertically extending external gripping ribs 4.
• a cured plastisol liner 5 is confined between an inwardly projecting retaining lip 6 and a downwardly projecting inner rib 7. It will be seen that the surfaces of the lip 6 and rib 7 and the portion of the top 1 lying between them is smoothly curved for reasons explained earlier.
• the rib 7 may be provided with projections 8 at intervals around its outer periphery for engagement with the inner periphery of the liner 5.
• shallow transverse ribs 9 may be provided on the underside of the top 1 extending outwardly from the rib 7 and the ribs 9 may be extended round the radiused corner to meet the lip 6, as shown.
• the quantity of plastisol charged into the annular space outward of rib 7 somewhat exceeds the amount that could be charged if the then inverted shell had been stationary, instead of ⁇ ⁇ turning at a relatively slow rate.
• the quantity of liner material provides a satisfactorily thick portion for engaging the top end sealing surface of the container and for becoming properly cured by micro-wave curing.
• Figure 2 differs from the con ⁇ struction of Figure .1 principally in that the inner rib 17 is arranged to overhang and retain the inner edge portion of the liner 5. It will also be seen that the top of the shell is locally thickened at 1 ' over the inner thinner portion of the liner 5. Although not shown in Figure 2 the projections 8 and/or shallow ribs 9 might be incorporated with advantage in this construction.
• closure cap illustrated in Figures 3 and 4 is in fact two separate caps, respectively designed to fit (left half) a standard moulded plastic P.E.T. bottle for holding pressurised beverages and to fit (right half) a standard glass bottle.
• the shell is injection- moulded through a gate at the centre of the top panel 21, which is slightly thickened centrally and decreases in thick ⁇ ness outwardly towards its periphery to allow better flow of plastic material in the mould outwardly to the skirt 22. This local thickness also improves the resistance of the top panel 21 to "doming" under upward pressure.
• a moulded p.v.c. plastisol gasket 25 is retained between an inner rib 27 and a retaining lip 26.
• the lip 26 at the left hand side is essentially the same as the lip 6 in Figure 1 , and has a downwardly and inwardly facing under-surf ce 28.
• Lip 26 ⁇ at the right hand side has a similar und ⁇ r-surface
• the lip 26a has a rounded head portion 29 and is reduced in thickness at 30, so as to render it more flexible in the upward direction. This is necessary because the range of tolerances on the neck diameter of a glass bottle is necessarily wider than for a moulded plastics bottle. In both constructions the internal diameter of the lip is set at the minimum permitted diameter of the container neck.
• these two caps there are no radial ribs or similar formations provided to prevent turnin movement of the liner 25 in the shell. According to whether it is desired to reduce such movement or to promote it, the surface 32 of the shell may be subjected to appropriate post- treatment before the liner 25 is formed.
• the caps of Figures 3 and 4 may be used with bottles having vertical vent slots cut in the thread in known way (not illustrated in Figure 4).
• the distance between ribs 26 and 26a_ and the top panel are dimensioned in such a way that the seal between liner 25 and the container is dis ⁇ engaged before the cap thread 34 is released from the con ⁇ tainer thread to allow gas to vent before such disengagement. It would be possible to provide vent slots in the cap thread 34, but it is preferred not to do so, because of the weaken ⁇ ing effect of such slots on the thread and consequently of the hoop strength of the skirt 22. It will be seen that the vertical extent of the thread 34 greatly exceeds the distance between the top panel 21 and the lip 26.
• Both of the forms of closure shown in Figure 3 may be provided with an integral security band of any known construction, as shown in Figure 4.
• the security band 40 shown in dotted lines, is connected ' to the cap skirt 22 by a series of spaced bridges 41, in the well known way.
• the security band 40 has an integral internal rib 42, adapted to be sprung over and re ⁇ tained under the ring R on the bottle. It is one of the advantages of the liner-forming method employed in the present invention that it renders it ' possible to incorporate a liner having a maximum outer diameter equal to or greater than the internal diameter of a security band, having a mechanical clip-under retaining rib, such as 42.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Closures For Containers (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=10531573

Family Applications (1)

Country Status (6)

Cited By (1)

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• 1983
  • 1983-07-06 WO PCT/GB1983/000168 patent/WO1984000346A1/en not_active Application Discontinuation
  • 1983-07-06 JP JP58502319A patent/JPS59501203A/ja active Pending
  • 1983-07-06 EP EP83902113A patent/EP0112879A1/en not_active Withdrawn
  • 1983-07-07 IT IT8321970A patent/IT1206691B/it active
  • 1983-07-07 ZA ZA834957A patent/ZA834957B/xx unknown
  • 1983-07-08 ES ES1983273410U patent/ES273410U/es active Pending

Non-Patent Citations (1)

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