PLASTIC CAP WITH GASKET

Abstract: The present invention relates to a plastic cap (1) with a gasket, the cap comprising a skirt (2), a top (3), a connecting region (4) between the skirt and the top, a security ring (5), and a gasket (6) fixed to the top by fusion of the contact surfaces between the top and the gasket, characterized in that the gasket extends on the top of the cap internally and radially to an extent such as to leave a portion (12) of the connecting region (4) exposed.

Description: DESCRIPTION "Plastic cap with gasket" The present invention relates to a plastic cap with a gasket, the cap comprising a skirt with an internal thread, a top, a connecting region between the skirt and the top, a security ring, and a gasket formed integrally with the internal wall of the top. It is known that there are basically two types of plastic bottle caps with gaskets currently on. the market . The first type of cap consists of a body formed by a skirt, a top, a connecting region between the skirt and the top, a security ring, and a gasket applied to the top of the cap in various ways. This type of cap is thus constituted by two separate parts, the cap itself and the gasket, which are moulded separately and then assembled. The second type of cap differs from the first in that it is made as a single piece, the gasket being integral with the top of the cap. With regard to this second type of cap in particular, the gasket is in the form of a plastics film which adheres firmly to the top of the cap, extending so far as also to cover the connecting region between the top and the skirt of the cap. This structure is produced by a method with three steps in which the first step consists of the injection and/or compression moulding of plastics material in a suitable mould to form the body of the cap. The second step consists of the deposition, in the top of the cap, of a predetermined quantity of plastics material suitably heated so as to render it fluid. The last step consists of the insertion of a punch into the body of the cap to form the gasket, without sealing elements acting at the level of the neck of a bottle. Clearly, during this last step of the method, the quantity of fluid plastics material is compressed and distributed uniformly over the entire surface of the top of the cap until it reaches and also covers the connecting region between the top and the skirt of the cap. However, the above-mentioned plastic caps with gaskets have some disadvantages. With regard to the first type of cap, the gasket formed separately from the body of the cap is normally fitted in the top of the cap. There is therefore always the possibility that the gasket may be detached from the top during normal manipulation of the cap, compromising its leaktightness. Problems of leaktightness of bottles containing carbonated drinks have also been encountered. In any case, the fact that the cap as a whole is formed by two separate components does not meet with particular approval by purchasers. As an alternative to being fitted in the top of the cap, the gasket could be fixed thereto by means of biocompatible glues. In this case, however, the cap would adopt a degree of structural complexity and would have unacceptable costs. The second type of cap, on the other hand, does not have the above-mentioned disadvantages since it is constructed as a single piece. However, the disadvantage connected with leaktightness achieved purely by vertical pressure on the gasket is not removed. This problem is noticed, in particular, because a minimal movement in the unscrewing direction suffices to undo the seal, resulting in leakage of the gas content. There is therefore a great need to provide a plastic cap with a gasket which solves the problems of the prior art, particularly with regard to sealing under pressure. The problem upon which the present invention is based is therefore that of devising a plastic cap with a gasket which has structural and functional characteristics such as to satisfy the above-mentioned requirements and at the same time to prevent the problems of plastic caps with gaskets of the prior art. This problem is solved as recited in the appended claims . Further characteristics and advantages of the plastic cap with a gasket according to the present invention will become clear from the following description of two preferred embodiments thereof, given by way of non-limiting example, with reference to the appended drawings, in which: Figure 1 shows, in section, a plastic cap with a gasket according to the invention, Figure 2 shows, in section, a variant of the plastic cap with a gasket according to the invention, Figure 3 shows, in section, a further variant of the plastic cap with a gasket according to the invention. With reference to Figure 1, a plastic cap with a gasket according to the present invention is generally indicated 1. The cap 1 comprises a skirt 2, a top 3, a connecting region 4 between the skirt and the top, a security ring 5, and a sealing gasket 6. The skirt 2 has an internal wall having a thread 7 with one start and an outer wall having knurling 8 for facilitating the screwing of the cap 1 onto the neck of a bottle (not shown) and its unscrewing therefrom. In particular, the knurling 8 is created by a plurality of ribs arranged longitudinally relative to the outer wall of the skirt 2 so as to extend substantially throughout its length. The top 3 is a substantially flat disk connected to the skirt 2 by means of the connecting region 4. The connecting region 4 is therefore in the form of a ring with substantially flat internal and external walls. Alternatively, the internal and external walls may also be of other shapes such as, for example, a rounded shape . The security ring 5 comprises a shoulder 9 facing towards the top 3 of the cap 1. The shoulder 9 acts as a stop means for restraining the security ring 5 on the neck of the bottle by abutting a corresponding projection provided on the base of a bottle neck. Moreover, the security ring 5 has bridges 10 connecting it to the skirt 2 of the cap 1. The bridges are intended to break when the bottle is opened for the first time. The sealing gasket 6 is in the form of a thin disk which extends radially from the centre of the top 3 of the cap to an extent such as to leave a portion 12 of the connecting region 4 exposed. The sealing gasket 6 in fact has an outer edge 11 which terminates in the connecting region 4, of which it leaves a space 12 exposed. The exposed space 12 preferably corresponds substantially to half of the width of the internal wall of the connecting region 4. In particular, the gasket 6 has an annular lip 13 having, on its outer wall, an undercut with a corresponding projection 14. This projection 14 defines a sealing point for interfering with the internal wall of the neck of a bottle to prevent the liquid contained therein from leaking out once the cap 1 is screwed onto the neck. The particular function of the space 12 is to allow the outer edge 11 to deform resiliently, expanding radially in response to the squashing exerted by the upper edge of the neck of a bottle when the cap 1 is screwed onto it. This resilient deformation allows the gasket to adhere better to the upper edge of the bottle neck. For a bottle containing a carbonated drink in particular, the advantage which is achieved by the use of a plastic cap with a gasket according to the present invention is that leaktightness can be improved. This advantage is particularly valued when the bottles are stored for a fairly long period and/or are subjected to a fairly high temperature. In these cases, the pressure inside the bottle in fact increases substantially and may give rise to undesired leakages of gas . It should be noted, however, that the plastic cap with a gasket according to the present invention may also be used for closing containers in general, such as jars and pots for preserves. In fact, in this case, it is important to achieve a seal, for example, after the food contained in the containers has been pasteurized. With reference to Figure 2, a plastic cap with a gasket according to a variant of the present invention is generally indicated 101. The cap 101 comprises a skirt 15, a top 16, a connecting region 17 between the skirt and the top, a security ring 18, and a sealing gasket 19. The skirt 15, the connecting region 17, and the security ring 18 are not described here since they correspond to those already described above. The top 16 is a substantially flat disk joined continuously to the skirt 15 by means of the connecting region 17. The top 16 also has a plurality of anchoring elements 20 facing towards the inside of the cap and arranged around a circle located in the vicinity of the connecting region 17. These anchoring elements 20 have dovetail-shaped profiles. The sealing gasket 19 is in the form of a thin disk which extends radially from the centre of the top of the cap to an extent such as to leave a portion 21 of the connecting region 17 exposed. The sealing gasket 19 has recessed undercuts which can form a shaped coupling with the projecting undercuts defined by the dovetail-sectioned profiles of the anchoring elements 20: The particular function of the anchoring elements 20, in cooperation with corresponding recessed undercuts of the gasket, is to fix the gasket 19 to the top 16 of the cap 101. The outer edge 22 of the sealing . gasket 19 terminates at the level of the connecting region 17 of which it leaves exposed a portion 21 corresponding substantially to half of the surface of the internal wall of the connecting region 17. The outer edge 22 is also thickened. The sealing gasket 19 also comprises an annular lip 23 projecting from the surface of the gasket 19 towards the inside of the cap 101. In particular, the annular lip 23 has, on an outer wall, an undercut portion with a corresponding projection 24. This projection 24 defines a point for sealing by interference against the inner wall of the neck of a bottle to prevent leakage of a liquid contained therein once the cap 101 has been screwed onto the neck. An annular tooth-shaped element 25 is formed between the outer edge 22 and the annular lip 23 of the gasket 19. The thickening of the outer edge 22 and the annular tooth-shaped element 25 have the function of creating points of greater leaktightness in case there are irregularities in the surface of the upper edge of the bottle neck. With reference to Figure 3, a plastic cap with a gasket according to a further variant of the present invention is generally indicated 102. The cap 102 comprises a skirt 25, a top 26, a connecting region 27 between the top and the skirt, a security ring 28, and a sealing gasket 29. The skirt 25, the top 26, the connecting region 27, and the security ring 28 will not be described further here since they correspond to those already described above with reference to Figure 1. The sealing gasket 29 is in the form of a thin ring which extends over a peripheral portion 30 of the top 26 of the cap 102 so as also to cover a portion of the connecting region 27. The sealing gasket 29 in fact has an edge 32 which terminates in the connecting region 27 of which it leaves exposed a space 31 preferably corresponding to approximately half of the internal surface of the connecting region. The advantage achieved by the variant just described lies in the fact that this cap with a gasket is easily adaptable to containers for preserves and, in particular, to pots or jars which are subjected to a pasteurizing process immediately before they are hermetically closed. Naturally, in cases in which it is not necessary to produce a gasket in the form of a complete disk, this latter embodiment also permits a saving in thermoplastic material . The plastic cap with a gasket according to the present invention can be produced by adaptation of a conventional, widely known, rotary mould. A rotary mould of the type currently used for producing plastic caps with gaskets comprises a fixed plate having a series of cavities or female die portions, the plate being generally divided into one half having cavities suitable for forming gaskets and one half having cavities suitable for forming caps themselves. Moreover, injectors for injecting fluidized thermoplastic material are connected to the moulding cavities of the fixed plate by means of suitable holes. The mould also comprises a rotary plate having a series of cores or male mould elements which can be inserted in all of the respective moulding cavities so as to close them and which are involved both in the formation of the gaskets and in the formation of the caps . The two plates, that is, the fixed plate and the rotary plate, are consequently arranged facing one another so as to permit the above-mentioned insertion of the cores in the moulding cavities . In particular, in order to produce caps with gaskets according to the present invention, the head end portion of each male element is modified so as to have an annular outer surface for abutting and hence sealing against, the connecting region between the top and the side walls of the cavities for moulding the gasket . During a first step of the process of the moulding of the cap with -a gasket according to the present invention, the rotary plate is moved towards the fixed plate so that the head portion of each core enters either a gasket-moulding cavity or a cap-moulding cavity. In particular, in the region of the gasket-moulding cavities, the cores are positioned with the above- mentioned annular upper surfaces in abutment with the connection regions between the ends and the side walls of the cavities. Thermoplastic material is then injected to form solely the gasket in the gasket-moulding cavity. Once the gaskets have been moulded, the mould opens, allowing the cores to leave the respective cavities. In particular, the cores leaving the gasket-moulding cavities carry the moulded gaskets on their end portions . The rotary plate, that is, the plate carrying the cores, then rotates through 180° about an axis perpendicular to its surface which engages the fixed plate. The cores with the gaskets positioned on their head ends are thus disposed in the region of the cap-moulding cavities, whilst the cores which do not carry gaskets on their head ends are disposed in the region of the gasket- moulding cavities. At this point, the rotary plate is moved towards the fixed plate again, the cores carrying the gaskets enter the cap-moulding cavities, defining a closed moulding chamber for the formation of the cap itself, and the cores without gaskets enter the gasket-moulding cavities as described above, for the formation of the gasket. Thermoplastic material can now be injected both into the gasket-moulding cavities and into the cap-moulding cavities . Naturally, once again, solely gaskets are formed in the portion of the fixed plate carrying the gasket- moulding cavities, whereas the caps themselves are formed in the portion of the plate carrying the cap-moulding cavities, and are moulded directly around the already- moulded gaskets. Finally, the mould opens to allow the finished caps to be released from the cores leaving the cap-moulding cavities. A further rotation of the rotary plate through 180° returns the mould to the initial condition enabling a second moulding cycle to start . In order to mould anchoring elements according . to the variant of the present invention, the end of each moulding cavity will have a circular projection with a dovetail-shaped cross-section suitable for creating the recessed undercuts in the thickness of the gasket 19 during the gasket-moulding step, and then the anchoring elements 22 and the recesses 21 in the top 16 of the cap 101 during the moulding of the cap itself. With regard to the moulding of the annular gasket 29 as shown in Figure 3, it will suffice simply to provide a mould with two coaxial male elements of which the outer element will have an upper annular surface, as described above, for abutting the connecting region between the top and the side walls of the gasket-moulding cavity. The inner male element, on the other hand, will have an upper surface such as to abut the end of the moulding cavity during the gasket-moulding step. An annular chamber will thus be formed, into which the material will be injected to mould the gasket. The steps for moulding the cap with an annular gasket will be identical to those described above. The plastic cap with a gasket according to the present invention may undergo variations of shape on the basis of contingent requirements. For example, the anchoring elements may be provided on the gasket so that their projecting undercuts are coupled with respective recessed undercuts formed in the thickness of the top of the cap. In this case, the end of the moulding cavity will be modified so as to have a circular recess with a dovetail- shaped profile in order to be able to produce this variant . The threading may have one start or several starts, according to the type of bottle neck on which it is to fit. The gasket may not have a thickening of its outer edge or an annular tooth-shaped element if the gasket is made of particularly soft materials such as thermoplastic rubbers . There may be a variable number of anchoring elements which may be of any desired shape or may constitute a continuous ring. Moreover, the anchoring elements may also be provided for a conventional gasket which extends over the inner surface of the top of the cap so far as also to cover the connecting region between the top and the skirt of the tap completely. In order to form a gasket of this last type, it will suffice to adapt the gasket-moulding cavity as described above with the use of a conventional core . The plastics materials of which the cap and the gasket are made may vary according to requirements . For example, the cap may be made of polypropylene and the gasket of low-density polyethylene. As can be appreciated from the foregoing description, the cap with a gasket according to the invention satisfies the requirements referred to in the introductory portion of this description and at the same time overcomes the disadvantages of caps with gaskets of the prior art . The present invention is in fact implemented by a bottle cap with a gasket which is simple and functional, particularly in certain conditions such as high pressures of the bottle contents. Naturally, in order to satisfy contingent and specific requirements, an expert in the art may apply to the above-described cap with a gasket many modifications and variations all of which, however, are included within the scope of the invention as defined by the following claims .

Claims: CLAIMS 1. A plastic cap (1; 101; 102) with a gasket, the cap comprising a skirt (2; 15; 25), a top (3; 16; 26), a connecting region (4; 17; 27) between the skirt and the top, a security ring (5; 18; 28), and a gasket (6; 19; 29) fixed to the top by fusion of the contact surfaces between the top and the gasket, characterized in that the gasket extends on the top of the cap internally and radially to an extent such as to leave a portion (12; 21; 31) of the connecting region (4; 17; 27) exposed. 2. A plastic cap (1; 101) with a gasket according to Claim 1, in which the gasket (6;.19) extends from the centre of the top (3; 16) of the cap so as to form a complete, substantially uniform disk. 3. A plastic cap (102) with a gasket according to Claim 1, in which the gasket (29) extends in the form of a ring starting a predetermined distance from the centre of the top (26) so as to coyer a peripheral internal portion (30) thereof. 4. A plastic cap (1; 101; 102) with a gasket according to any one of Claims 1, 2 and 3, in which the exposed portion (12; 21; 31) of the connecting region (4; 17; 27) corresponds substantially to half of the extent of the connecting region. 5. A plastic cap (1; 101) with a gasket according to Claim 1 or Claim 2, in which the gasket (6; 19) comprises an annular lip (13; 23) projecting towards the inside of the cap, the annular lip comprising, on its outer side wall, an undercut with a corresponding projection (14; 24) for forming a sealing point by interference with a bottle neck. 6. A plastic cap (101) with a gasket according to Claim 1 or Claim 2, comprising anchoring means (20) for anchoring the gasket to the top. 7. A plastic cap (101) with a gasket according to Claim 6, in which the anchoring means comprise at least one projection (20) formed integrally with the top (16) of the cap, the at least one projection having projecting undercuts which form a shaped coupling with corresponding recessed undercuts of the gasket (19) . 8. A plastic cap (101) with a gasket according to Claim 7, in which the at least one projection (20) has a dovetail-shaped cross-section. 9. A plastic cap (101) with a gasket according to Claim 8, in which the at least one projection (20) is located on a circle situated in the vicinity of the connecting region (17) . 10. A plastic cap (101) with a gasket according to any of Claims 6 to 9, in which the gasket (19) comprises a thickened outer edge (22) and a tooth-shaped projection (25) positioned between the outer edge and the annular ip (23) .

Inventors: CARUANA ALFONSO, CARUANA, ALFONSO
Applicants: CARUANA ALFONSO, GEFIT SPA, CARUANA, ALFONSO, GEFIT S.P.A.
Application year: 2000
Main classification: B65D41
IPC codes: B65D41