Abstract:
A plastic screw cap includes a cylindrical cup provided with an internal thread and with a tamper-evident ring which is coupled to the rim of the cup by means of a plurality of bridges forming a fracture line; the ring has a collar or expansion for retaining it below an annular raised portion of a container whereto the cap is applied. Incisions are formed on the outside of the tamper-evident ring, the incisions do not cross the entire thickness of the ring and allow an elastic radial expansion of the ring, such as to pass beyond the annular raised portion during the application of the cap to the container.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a plastic screw cap with tamper-evident ring. 
     Caps of the above type are already known commercially and comprise a cylindrical cup which is internally threaded in order to be screwed onto the top of the container (bottle). 
     A so-called tamper-evident ring is coupled to the rim of the cup by means of breakable bridges and is internally provided with engagement elements constituted by flaps or by a collar which, when the cap is applied so as to close the container, engage under an annular raised retention portion of the container. By unscrewing the cap, the flaps or the collar abut against the annular raised portion and retain the ring, while the resulting axial traction force breaks the bridges. 
     Conventional caps entail the problem of ensuring that during application to the container the flaps or collar can widen or otherwise be elastically deformed in order to pass over the raised retention portion of the bottle and then close again below said raised portion, so as to allow the separation of the tamper-evident ring during the unscrewing of the cap and clearly indicate that the container has been opened. 
     However, in currently commercially available caps the tamper-evident ring, in order to ensure that the teeth or collar remain engaged below the annular raised portion of the container during unscrewing and can thus ensure the breaking of the bridges, has an excessively rigid structure and therefore passing over the raised portion when the cap is applied to the container is critical. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a plastic cap which is capable of substantially obviating the shortcomings of conventional caps. 
     This aim is achieved by a plastic screw cap of the type composed of a cylindrical cup provided with an internal thread and with a tamper-evident ring which is coupled to the rim of the cup by means of a plurality of bridges forming a fracture line, said ring having a retention means for retaining it below an annular raised portion of a container whereto the cap is applied, incisions being formed on the outside of said tamper-evident ring, said incisions do not cross the entire thickness of the ring and allow an elastic radial expansion of the ring, such as to pass beyond said annular raised portion during the application of the cap to the container. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the present invention will become apparent from the following detailed description, on the basis of the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a cap provided with a tamper-evident ring, whose outside diameter is smaller than the diameter of the cup, and with an internal annular expansion provided with retention flaps; 
     FIG. 2 is a partially sectional view, taken along an axial plane, of the screw cap of FIG. 1; 
     FIG. 3 is an enlarged-scale view of a detail of FIG. 2; 
     FIG. 4 is a partially sectional view, taken along an axial plane, of the cap in the position for application to a container; 
     FIG. 5 is a partially sectional view, taken along an axial plane, of a variation of the cap; 
     FIG. 6 is an enlarged-scale view of the cross-section of the tamper-evident ring of the cap of FIG. 5; 
     FIG. 7 is a partially sectional view of another variation of the cap; 
     FIG. 8 is an enlarged-scale view of the cross-section of the tamper-evident ring of the cap of FIG. 7; 
     FIG. 9 is a partially sectional view of another variation of the cap; 
     FIG. 10 is an enlarged-scale view of the cross-section of the tamper-evident ring of the cap of FIG. 9; 
     FIGS. 11 and 12 are partially sectional views, taken along an axial plane, of the cap according to two further variations; 
     FIGS. 13 to  15  are partially sectional views, taken along an axial plane, of three variations of a cap provided with a tamper-evident ring, whose outside diameter is equal to the outside diameter of the cup, and with an internal retention collar. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1,  2  and  3 , the reference numeral  1  generally designates a cap according to the present invention, formed by molding plastics according to conventional methods. The cap  1  comprises a cylindrical cup  2  which is composed of a bottom  3 , which is internally covered by a liner  4 , and of a cylindrical wall  5  inside which a thread  6  is formed. 
     A tamper-evident ring  7  protrudes from the rim of the cylindrical wall  5  of the cup  2  and is composed of a cylindrical wall whose rim is connected to the rim of the cup  2  by means of a plurality of bridges  8  which are spaced by slits  9 . The bridges  8  and the slits  9  form a fracture line which allows to separate the tamper-evident ring  7  from the cup  2  when the cap is unscrewed from the container whereto it has been applied. 
     The opposite rim of the ring  7  is internally provided with an annular expansion  10 , whose inside diameter is substantially equal to the inside diameter of the wall  5 . The bridges  8  and the slits  9  can be provided in any manner, for example during the molding of the cap by providing suitable mold shapes or by means of cutting operations performed after molding. 
     A connecting region is formed between the rim of the cup  2  and the expansion  10  and is constituted by a wall  11  whose outside diameter is smaller than the outside diameter of the wall  5  and whose inside diameter is greater than the inside diameter of the expansion  10 , so that the wall  11  is significantly thinner than the wall  5  of the cup. This difference in thickness allows the wall  11 , by exploiting the elasticity of the plastics material, to follow any widening occurring during the application of the cap to a container and to assume a conical shape which tapers toward the bottom  3  of the cup  2 , as occurs for example during application to a container. 
     From the above description it is thus evident that the expansion  10  is significantly thicker than the wall  11  and protrudes from the inner face thereof, so that the inside diameter of the expansion  10  is significantly smaller than the inside diameter of the wall  11 . 
     The greater thickness of the annular expansion  10  ensures that said expansion has, in relation to the elasticity of the plastics material the cap is made of, a reduced ability to widen with respect to the wall  11 . 
     The difference in inside diameter between the expansion  10  and the wall  11  forms a steplike connecting region, wherefrom multiple flaps  12  protrude toward the inside of the cup  2 ; said flaps are inclined toward the bottom  3  of the cup at a preset angle. The flaps  12  are equidistant and mutually separated by spaces  13  and their thickness is preferably greater than the thickness of the wall  11  but smaller than the thickness of the expansion  10 . Moreover, the upper and lower faces of the flaps  12  are connected to the internal faces of the wall  11  and of the expansion  10  by radiused regions  14  and  15 . 
     The different thickness of the wall  11 , of the expansion  10  and of the flaps  12  causes on the one hand easier application of the cap to a container  16  (shown in dashed lines in FIG. 4) and, on the other hand, firmer retention of the tamper-evident ring  7  below the annular raised portion  17  of the container  16  whereto the cap  1  is applied and, ultimately, safer separation thereof when the cap is unscrewed. 
     However, the greater thickness of the annular expansion  10  constitutes a considerable critical point in the application of the cap to the container. Indeed, when applying the cap, due to the lower elasticity of the expansion  10  the contrast to the widening of the thinner region of the wall  11  which is close to the expansion  10  can cause the bridges  8  to break. 
     According to an important aspect of the present invention, this drawback can be obviated with surprisingly positive results by providing a plurality of incisions  18  which are distributed along the outer peripheral region of the tamper-evident ring  7  and affect the region of the expansion  10 . Said incisions  18  have an axial orientation and do not pass through the thickness of the expansion. In this manner, when the cap is applied to the container  16 , the radial expansion of the tamper-evident ring  7  is facilitated by the opening of the score lines  18  in a circumferential direction (see FIG.  4 ), which by entailing an increase in the diameter of the expansion allow the tamper-evident ring  7  to slide above the annular raised portion  17  of the container below which it must engage. 
     It should be observed that since the incisions  18  are not through cuts, they do not compromise the strength of the expansion  10  and therefore the engagement of the flaps  12  below the annular raised portion  17  of the container. 
     The number of the incisions  18  is chosen as a function of the greater flexibility to be given to the tamper-evident ring  7 . 
     It should be observed that the ability of the tamper-evident ring  7  to expand radially is limited so that the tamper-protection of the container is not compromised. Moreover, the greater flexibility of the tamper-evident ring and the reduced stresses whereto the bridges  8  are subjected during the application of the cap allow to reduce the thickness of the bridges and therefore to facilitate their breakage when the cap is unscrewed. 
     In its practical embodiment, the cap according to the present invention is susceptible of numerous modifications and variations, all of which are within the scope of the same inventive concept. 
     FIGS. 5 and 6 are views of an embodiment in which instead of the axial incisions a circumferential incision  19  is provided in the outer face of the wall  11 , arranged between the fracture line formed by the slits  9  and the expansion  10 . It is of course possible to combine axial incisions  18  with a circumferential incision  19 , as provided in the embodiment of FIGS. 7 and 8. In particular, it should be observed that the axial incisions can partially extend into the wall  11  as well and join the circumferential incision  19 . 
     FIGS. 9,  11  and  12  relate to the application of the inventive concept to a cap in which the tamper-evident ring  7  is not provided with the annular expansion  10  and retention of the cap on the container is achieved with a continuous internal collar  20  instead of with flaps  12 . Advantageously, the axial incisions  18 , as shown in FIG. 10, affect the region of the collar  20  and continue into the wall  11 . FIGS. 13 to  15  illustrate a cap according to still a further aspect of the invention, wherein the tamper-evident ring has an outside diameter which is equal to that of the cup  2 . In this case also, the axial incisions  18  can continue into the wall  11 . In the practical embodiment of the invention, the incisions  18 ,  19  can be formed during molding. However, said incisions are preferably formed by means of a cutting machine provided with a blade which allows to precisely adjust the depth of the incisions. 
     The disclosures in Italian Patent Application No. BO98A000296 from which this application claims priority are incorporated herein by reference.