WO1990011232A1 - A screw cap of thermoplastics material - Google Patents

A screw cap of thermoplastics material Download PDF

Info

Publication number
WO1990011232A1
WO1990011232A1 PCT/EP1990/000485 EP9000485W WO9011232A1 WO 1990011232 A1 WO1990011232 A1 WO 1990011232A1 EP 9000485 W EP9000485 W EP 9000485W WO 9011232 A1 WO9011232 A1 WO 9011232A1
Authority
WO
WIPO (PCT)
Prior art keywords
cap
washer
seat
container
annular rib
Prior art date
Application number
PCT/EP1990/000485
Other languages
French (fr)
Inventor
Mario Margaria
Original Assignee
Alplast S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alplast S.P.A. filed Critical Alplast S.P.A.
Publication of WO1990011232A1 publication Critical patent/WO1990011232A1/en

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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
    • B65D41/0435—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 a screw cap which is produced by the injection moulding of thermoplastics material and has a horizontal end wall, a cylindrical skirt with internal threading for the screwing of the cap on to the externally-threaded neck of a container by means of a screw-capping machine, and an annular sealing washer made from a plastisol which, after moulding of the cap, is cast in an annular seat and polymerised by heating, the seat being defined by a peripheral annular portion of the internal surface of the horizontal end wall of the cap, by an annular rib which projects from the internal surface, and by a substantially triangular-section annular rib which projects radially from the top of the internal surface of the cylindrical skirt of the cap.
  • the cap may be overtightened, that is, it may be rotated through a greater angle than the predetermined angle relative to the container neck so that the internal surface of the horizontal wall of the cap is brought into contact with the end face of the mouth of the container.
  • the washer is cut by the container neck and split into two concentric, annular parts, to the detriment of its sealing effect.
  • the subject of the present invention is a screw cap of thermoplastics material, of the type specified above, which has the characteristic defined in the characterising part of
  • Figure 1 is a partial axial section of a cap according to the invention
  • Figure 2 is a diagram showing the arrangement of the projections of the cap shown in Figure 1,
  • Figure 3 shows a variant of the cap of Figure 1
  • Figure 4 shows a detail indicated by the arrow IV of Figure 3, at an intermediate stage of production and on an enlarged scale.
  • the cap shown in Figures 1 and 2 comprises a horizontal end wall 1 and a cylindrical skirt 2 with internal threading 3 whereby the cap can be screwedon to the externally-threaded neck A of a container.
  • the internal surface of the horizontal end wall 1 of the cap has an annular rib 4 at a certain distance from the cylindrical skirt 2.
  • the internal surface of the cylindrical skirt 2 of the cap has an annular radial rib 5 with a substantially .triangular cross-section. Together with the peripheral portion of the internal surface la, the two ribs 4 and 5 define an annular seat for housing a sealing washer 6 which is made from a plastisol which has been poured in and subsequently polymerised by heating.
  • the internal surface of the horizontal wall 1 of the cap has acircular row of projections 7 of equal height and spaced around a circle.
  • the projections 7 have downwardly-converging frusto-conical shapes; they could, however, also be in the shape of regular frusto-pyramids.
  • the height of the projections is of the order of 0.3 mm and the diameter of the end face of each projection is between 1/2 and 1/3 of the thickness of the wall of the container neck A. Normally this diameter is between 1 and 1.5 mm.
  • each projection 7 is provided and the central axis of symmetry X of each projection 7 intersects the central line of symmetry Y of the end face B of the container neck A.
  • the cap is shown when it has first been screwed on to a container by means of a screw-capping machine.
  • the end faces 7a of the projections 7 would form a stop against the end surface B of the neck A of the container, thus preventing the washer 6 from being split into two concentric annular parts as a result of contact between the surfaces la and B.
  • the projections 7 act as punches on the washer 6 and form a small hole therein in correspondence with each projection; however, since the diameters of the projections 7 are less than the thickness of the neck A of the bottle, the continuity of the washer 6 is not broken and the sealing effect is ensured even in this event.
  • the cap is made from a very rigid thermoplastics material, such as polypropylene filled with mineral fibres and having a hardness greater than 75 Shore D.
  • the cap shown has an opening tear-strip 8 interposed between the cylindrical skirt 2 and a lower ring 9 which has an internal annular rib 10 which snap engages beneath a corresponding rib on the neck of the container as a result of the first screwing-on of the cap, as described in detail in the European application mentioned above.
  • caps of this type in addition to the problem of preventing the washer from being cut during the first screwing-on, there is also the problem of preventing it from being released accidentally from its seat during the processing of the product.
  • the cap shown in Figure 3 has an additional annular rib 11 which projects from the periphery of the internal surface la of the horizontal end wall 1 so as partially to enter the seat for the washer 6.
  • the rib 11 extends adjacent the top of the cylindrical skirt 2 and projects towards the tip of the annular rib 5 which projects radially from the top of the cylindrical skirt 2.
  • the cross-section of the rib 11 is tapered from its base towards its free end and the diameter D 1 of the circumference defined by the tip of the rib 11 is approximately 1mm longer than the diameter D_ of the circumference defined by the tip of the annular rib 5.
  • the rib 11 is incorporated in the washer and therefore helps to prevent the washer from becoming disengaged from its seat subsequently.
  • a further characteristic which tends to prevent the accidental release of the washer 6 from its seat lies in the fact that the inner periphery of the seat 12 is defined by an annular rib 13 which has a thinner end portion 14 which projects horizontally towards the seat so as to form an engagement lip for the washer.
  • the vertical section of the rib 12 has a root portion 13 with inclined, downwardly-converging sides.
  • the outer side (that is that which faces the seat) is shorter than the inner side and is more inclined to a vertical axis.
  • the sealing ring also has an end portion 14a with an outer vertical side and a slightly- inclined inner side.

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

Abstract

A screw cap of thermoplastics material is provided with a seat adjacent the periphery of the inner surface of its horizontal end wall (1a) for housing a sealing washer (6) made from a plastisol which is poured in and polymerised by heating. In order to prevent the washer (6) from being damaged, to the detriment of the seal, during the first screwing of the cap onto the threaded neck (A) of a container by machine as a result of the over-tightening of the cap due to the imperfect adjustment of the screw-capping machine, the internal surface of the horizontal end wall (1a) of the cap is provided with a plurality of circularly-spaced projections (7) which cooperate with the end surface (B) of the container neck (A) to prevent the washer (6) from being cut. In the case of caps used for the closure of containers for food products which are to be pasteurised, the anchorage of the washer (6) in its seat is improved by the provision of an additional, axial, annular rib (11), which partially penetrates the washer (6), and an annular rib (12) which defines the inner periphery of the seat and has a lip (14) which is bent horizontally towards the seat.

Description

A screw cap of thermoplastics material
The present invention relates to a screw cap which is produced by the injection moulding of thermoplastics material and has a horizontal end wall, a cylindrical skirt with internal threading for the screwing of the cap on to the externally-threaded neck of a container by means of a screw-capping machine, and an annular sealing washer made from a plastisol which, after moulding of the cap, is cast in an annular seat and polymerised by heating, the seat being defined by a peripheral annular portion of the internal surface of the horizontal end wall of the cap, by an annular rib which projects from the internal surface, and by a substantially triangular-section annular rib which projects radially from the top of the internal surface of the cylindrical skirt of the cap.
When a cap of the type defined above is screwed on to the threaded neck of a container by machine, the machine is adjusted so that, at the end of the screwing stage, during which the end of the container neck penetrates the washer, this end surface stops at a certain distance, generally between 0.7 and 0.5 mm, from the inner surface of the horizontal end wall of the cap.
If the screw-capping machine is imperfectly adjusted, the cap may be overtightened, that is, it may be rotated through a greater angle than the predetermined angle relative to the container neck so that the internal surface of the horizontal wall of the cap is brought into contact with the end face of the mouth of the container. In this event, the washer is cut by the container neck and split into two concentric, annular parts, to the detriment of its sealing effect. In order to avoid this problem, the subject of the present invention is a screw cap of thermoplastics material, of the type specified above, which has the characteristic defined in the characterising part of
Claim 1.
Further characteristics and advantages of the present invention will become clear from the description which follows with reference to the appended drawings, provided by way of non-limiting example, in which:
Figure 1 is a partial axial section of a cap according to the invention,
Figure 2 is a diagram showing the arrangement of the projections of the cap shown in Figure 1,
Figure 3 shows a variant of the cap of Figure 1, and
Figure 4 shows a detail indicated by the arrow IV of Figure 3, at an intermediate stage of production and on an enlarged scale.
The cap shown in Figures 1 and 2 comprises a horizontal end wall 1 and a cylindrical skirt 2 with internal threading 3 whereby the cap can be screwedon to the externally-threaded neck A of a container.
The internal surface of the horizontal end wall 1 of the cap has an annular rib 4 at a certain distance from the cylindrical skirt 2.
Near its top, the internal surface of the cylindrical skirt 2 of the cap has an annular radial rib 5 with a substantially .triangular cross-section. Together with the peripheral portion of the internal surface la, the two ribs 4 and 5 define an annular seat for housing a sealing washer 6 which is made from a plastisol which has been poured in and subsequently polymerised by heating.
In correspondence with the seat for the washer 6, the internal surface of the horizontal wall 1 of the cap has acircular row of projections 7 of equal height and spaced around a circle.
In the embodiment illustrated, the projections 7 have downwardly-converging frusto-conical shapes; they could, however, also be in the shape of regular frusto-pyramids.
The height of the projections is of the order of 0.3 mm and the diameter of the end face of each projection is between 1/2 and 1/3 of the thickness of the wall of the container neck A. Normally this diameter is between 1 and 1.5 mm.
As shown in Figure 2, eight equiangularly-spaced projections 7 are provided and the central axis of symmetry X of each projection 7 intersects the central line of symmetry Y of the end face B of the container neck A.
In Figure 1, the cap is shown when it has first been screwed on to a container by means of a screw-capping machine.
As can be seen from this drawing, in this fully-screwed position, the presence of the projections 7 is not detrimental to the seal achieved by the washer 6 since they are of small height and their end faces 7a remain at a certain distance from the end face B of the container neck A.
If, due to defective adjustment of the screw-capping machine, the cap were to be rotated through a greater angle than the predetermined angle during its initial screwing on, the end faces 7a of the projections 7 would form a stop against the end surface B of the neck A of the container, thus preventing the washer 6 from being split into two concentric annular parts as a result of contact between the surfaces la and B.
In this event, the projections 7 act as punches on the washer 6 and form a small hole therein in correspondence with each projection; however, since the diameters of the projections 7 are less than the thickness of the neck A of the bottle, the continuity of the washer 6 is not broken and the sealing effect is ensured even in this event.
In the variant illustrated in Figure 3, a screw cap of the type described in European patent application EP-A-0261645 by the same Applicant is shown and is intended, in particular, for use in closing jars or bottles for use in the food industry to contain products which are to be pasturised.
In this case, the cap is made from a very rigid thermoplastics material, such as polypropylene filled with mineral fibres and having a hardness greater than 75 Shore D.
The cap shown has an opening tear-strip 8 interposed between the cylindrical skirt 2 and a lower ring 9 which has an internal annular rib 10 which snap engages beneath a corresponding rib on the neck of the container as a result of the first screwing-on of the cap, as described in detail in the European application mentioned above.
In caps of this type, in addition to the problem of preventing the washer from being cut during the first screwing-on, there is also the problem of preventing it from being released accidentally from its seat during the processing of the product.
In order to solve this further problem, in addition to the ring of projections 7 described with reference to Figures 1 and 2, the cap shown in Figure 3 has an additional annular rib 11 which projects from the periphery of the internal surface la of the horizontal end wall 1 so as partially to enter the seat for the washer 6. The rib 11 extends adjacent the top of the cylindrical skirt 2 and projects towards the tip of the annular rib 5 which projects radially from the top of the cylindrical skirt 2.
The cross-section of the rib 11 is tapered from its base towards its free end and the diameter D1 of the circumference defined by the tip of the rib 11 is approximately 1mm longer than the diameter D_ of the circumference defined by the tip of the annular rib 5.
When the washer 6 is cast in its seat and polymerised, the rib 11 is incorporated in the washer and therefore helps to prevent the washer from becoming disengaged from its seat subsequently.
A further characteristic which tends to prevent the accidental release of the washer 6 from its seat lies in the fact that the inner periphery of the seat 12 is defined by an annular rib 13 which has a thinner end portion 14 which projects horizontally towards the seat so as to form an engagement lip for the washer.
The said shaping of the rib 12, which is shown in Figure 3, cannot be produced during the injection moulding of the cap and the rib is therefore moulded in the' shape shown in Figure 4 and its end is subsequently deformed permanently by pressure with a punch.
As shown in Figure 4, after the injection moulding of the cap, the vertical section of the rib 12 has a root portion 13 with inclined, downwardly-converging sides. The outer side (that is that which faces the seat) is shorter than the inner side and is more inclined to a vertical axis. The sealing ring also has an end portion 14a with an outer vertical side and a slightly- inclined inner side. This shaping of the sealing ring of the rib 12, which is produced by moulding, enables the end portion 14a to be deformed outwardly by means of a punch into the position indicated 14 in Figure 3.

Claims

1. A screw cap which is produced by the injection moulding of thermoplastics material and has a horizontal end wall (1) , a cylindrical skirt (2) with internal threading (3) for the screwing of the cap, on to the externally-threaded neck (A) of a container by means of a screw-capping machine, and an annular sealing washer (6) made from a plastisol which, after the moulding of the cap, is cast in an annular seat and polymerised by heating, the seat being defined by a peripheral annular portion of the internal surface (la) of the horizonal end wall (1) of the cap, by an annular rib (4, 12) which projects from the internal surface (la) , and by a substantially triangular-section annular rib (5) which projects radially from the top of the internal surface of the cylindrical skirt (2) of the cap, characterised in that: in correspondence with the seat for the washer (6) , the internal surface (la) of the horizontal wall (1) of the cap has aαtiαϊlar row of projections (7) of equal height and spaced around a circle; the projections (7) being of such a shape and height that:
- when the cap is engaged by a screw-capping machine for screwing it on to the threaded mouth (A) of a container, each projection (7) faces a central portion of the en anilar ϋΞce (B) σf the mouth (A) of the container,
- upon completion of the screwing stage with the screw-capping machine operating normally, the end face (7a) of each projection (7) is spaced from the end face (B) of the container neck (A) , whilst, should the machine operate incorrectly so as to cause overtightening of the cap, the projections (7) strike the end face (D) of the container neck (A) so as to prevent the washer (6) from being split into two concentric annular parts as a result of the contact between the internal surface (la) of the horizontal wall (1) of the cap and the end face (B) of the container neck (A) .
2. A cap according to Claim 1, characterised in that: the projections (7) have circular or regular polygonal cross-sections, the diameter (or the diagonal) of the end face (7a) of each projection (7) is between 1/2 and 1/3 of the thickness of the wall of the container neck (A) , - when the cap is screwed on to a container, the central axis of symmetry (X) of each projection (7) intersects the central line of symmetry (Y) of the end annular face of the container neck (A) .
3. A cap according to Claim 2, characterised in that the diameter (or the diagonal) of the end face (7a) of each projection (7) is between 1 and 1.5 mm.
4. A cap according to Claim 2, characterised in that the projections (7) are frustoconical.
5. A cap according to Claim 2, characterised in that the height of each projection (7) is of the order of 0.3 mm.
6. A cap according to Claims 1 to 5, characterised in that it has eight equally-spaced projections (7) .
7. A cap according to Claim 1, characterised in that the internal surface (la) of the horizontal end wall (1) has an additional annular rib (11) in its peripheral region, which extends partially into the seat for the washer (6) adjacent the top of the cylindrical skirt (2) and projects towards the tip of the annular rib (5) which projects radially from the top of the cylindrical skirt (2) .
8. A cap according to Claim 7, characterised in that the cross-section of the additional annular rib (11) tapers from its base towards its free edge.
9. A cap according to Claim 8, characterised in that the diameter (D..) of the circumference defined by the tip of the additional rib (11) is approximately 1 mm longer than the diameter (D2) of the circumference defined by the tip of the annular rib (5) which projects radially from the top of the cylindrical skirt
(2).
10. A cap according to Claim 1, characterised in that the annular rib (11) which defines the inner periphery of the seat for the washer (6) has a thinner edge portion (14) which is bent horizontally towards the seat.
11. A cap according to Claim 10, characterised in that, after the injection moulding of the cap, the vertical section of the annular rib (12) has a root portion (13) with outwardly-converging sides, the outer side being longer than the inner side, and an end portion (14a) with an outer vertical side and an inner side which is inclined slightly towards the free end and in that the end portion (14a) is deformed inwardly to form the horizontal portion (14) before the casting of the plastisol in the washer seat.
PCT/EP1990/000485 1989-03-29 1990-03-27 A screw cap of thermoplastics material WO1990011232A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT8967217A IT1232058B (en) 1989-03-29 1989-03-29 SCREW CAPS OF THERMOPLASTIC MATERIAL
IT67217A/89 1989-03-29

Publications (1)

Publication Number Publication Date
WO1990011232A1 true WO1990011232A1 (en) 1990-10-04

Family

ID=11300577

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1990/000485 WO1990011232A1 (en) 1989-03-29 1990-03-27 A screw cap of thermoplastics material

Country Status (3)

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AU (1) AU5337290A (en)
IT (1) IT1232058B (en)
WO (1) WO1990011232A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2686065A1 (en) * 1992-01-14 1993-07-16 Sincoplas BOTTLE CLOSURE DEVICE WITH SEAL.
DE102010028522A1 (en) 2010-05-04 2011-11-10 Robert Bosch Gmbh Screw cap for soft packaging
FR3128697A3 (en) * 2021-10-28 2023-05-05 Massilly Holding Cap to close a packaging body by screwing

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH464721A (en) * 1966-10-26 1968-10-31 Ciba Geigy Container closure cap with inner seal
FR2334579A1 (en) * 1975-12-11 1977-07-08 Valves & Produits Industriels Sealing ring of the thermoplastic cap of a pneumatic tyre valve - held in place by burring the thermoplastic under heat
EP0095326A2 (en) * 1982-05-20 1983-11-30 National Plastics Limited Container closure blank
EP0155021A1 (en) * 1984-02-09 1985-09-18 Kornelis' Kunsthars Producten Industrie B.V. A closure cap provided with a gasket and a sealing ring from an olefin polymer
US4570811A (en) * 1985-01-30 1986-02-18 Continental White Cap, Inc. Plastic closure with flowed-in plastisol lining

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH464721A (en) * 1966-10-26 1968-10-31 Ciba Geigy Container closure cap with inner seal
FR2334579A1 (en) * 1975-12-11 1977-07-08 Valves & Produits Industriels Sealing ring of the thermoplastic cap of a pneumatic tyre valve - held in place by burring the thermoplastic under heat
EP0095326A2 (en) * 1982-05-20 1983-11-30 National Plastics Limited Container closure blank
EP0155021A1 (en) * 1984-02-09 1985-09-18 Kornelis' Kunsthars Producten Industrie B.V. A closure cap provided with a gasket and a sealing ring from an olefin polymer
US4570811A (en) * 1985-01-30 1986-02-18 Continental White Cap, Inc. Plastic closure with flowed-in plastisol lining

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2686065A1 (en) * 1992-01-14 1993-07-16 Sincoplas BOTTLE CLOSURE DEVICE WITH SEAL.
EP0552086A1 (en) * 1992-01-14 1993-07-21 Societe Industrielle Et Commerciale De Matieres Plastiques - Sincoplas Bottle closure with annular seal
DE102010028522A1 (en) 2010-05-04 2011-11-10 Robert Bosch Gmbh Screw cap for soft packaging
WO2011138062A1 (en) 2010-05-04 2011-11-10 Robert Bosch Gmbh Screw closure for soft packagings
FR3128697A3 (en) * 2021-10-28 2023-05-05 Massilly Holding Cap to close a packaging body by screwing

Also Published As

Publication number Publication date
IT1232058B (en) 1992-01-23
IT8967217A0 (en) 1989-03-29
AU5337290A (en) 1990-10-22

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