Bottom of preforms

Abstract

The invention relates to a preform which includes, centred on a single axis xx′: a neck ( 5 ), a cylindrical body ( 12 ), and a sealed spheroidal bottom ( 13 ), and is defined relative to the dimensions of a predefined bottle model ( 1 ) which includes: a bottom ( 3 ), a body ( 2 ) and a neck ( 5 ), said neck ( 5 ) of said bottle model ( 1 ) being identical to the neck of said preform ( 11 ).

1 .- 10 . (canceled) 
     
     
         11 . A preform comprising, centered on a single axis xx′: a neck, a cylindrical body, and an enclosed bottom that is spheroidal in shape, said preform being defined relative to the dimensions of a pre-established bottle model which comprises: a bottom, a body, and a neck, said neck of said bottle model being identical to said neck of said preform,
 said cylindrical body of said preform comprises an outside diameter Ae, a mean diameter Am measured at the neutral axis of the wall of said cylindrical body and of said bottom, and an inside diameter K, and 
 said cylindrical body as well as said spherical bottom of said preform comprise half-lengths L 3  and L 4  which are measured along the neutral axis of their wall: a half-length L 3  which extends from a connection between said neck and said cylindrical body to a center of said bottom and in particular to a point On of said bottom which is located at an intersection of said neutral axis and of said axis xx′, and a half-length L 4  which extends from said center On to a point NP which is located at a connection between said cylindrical body and said bottom of said preform, 
 said diameter Am of said preform is determined by applying, to the value of the maximum diameter Ab of the body of said pre-established bottle model, a reduction ratio chosen from among values which range from 3.7 to 4.5, due to the biaxial orientation; 
 said half-length L 3  is determined from half-length L 1  of said bottle model by applying to the value of half-length L 1  a reduction ratio that is also related to the biaxial orientation and which is chosen from among values ranging from 2.8 to 3.5, and 
 said half-length L 4  corresponds to said half-length L 3  multiplied by twice the value of the ratio between half-length L 2  of said bottle model and half-length L 1  of its base, in other words: L 4 =2×(L 3 )×(L 2 /L 1 ), and said half-length L 2  of said base corresponds to the mean radius of said base of said bottom of said bottle, 
 and, starting from the position of said point NP, which is determined from L 4 : 
 an external contour of said preform between said point NP and an external central point OP of said bottom, which is located on said axis xx′, is defined starting from said point OP, said point OP being located at a distance from said point On which corresponds to half a thickness C of said bottom of said preform and its value being in relation to a thickness B of the wall of said cylindrical body of said preform, measured near said neck, 
 said external contour of said preform comprising:
 starting from said central point OP, a spherical cap which is generated by an arc of a circle having a center P located on said axis xx′, at a distance from said central point OP which corresponds to a radius RE for which the value is in relation to said outside diameter Ae of said preform, and 
 starting from said point NP, a tapered surface which starts at said point NP and which extends towards said spherical cap, and which has a tip on said axis xx′, beyond said central point OP and external to said bottom of said preform, said tapered surface forming a half-angle M at the top which is chosen to allow said tapered surface to be secant with said spherical cap generated by an arc of a circle of radius RE, and 
 still for said external contour of said preform, a connection between said spherical cap of radius RE and said tapered surface consists of a toroidal ring generated by an arc of a circle of radius RG, and the surface of said toroidal ring is tangent to said spherical cap and to said tapered surface, and said radius RG is in relation to said outside diameter Ae of said preform, and 
 
 an internal contour of said bottom of said preform extends from the end of the envelope of a pseudo-cylindrical inner cavity of said body of said preform to a central point S located on said axis xx′, said central point S being positioned at a distance C from said central point OP, measured on said axis xx′, of which the value is in relation to a thickness B of the wall of said body of said preform, said internal contour of said bottom being defined in the following manner: 
 starting from said point S, said internal contour is generated by an arc of a circle of radius RH of which the center, positioned on said axis xx′, is located beyond said bottom, externally to said preform, so as to form a central rounded portion in the shape of a spherical dome, said radius RH being in relation to said outside diameter Ae of said preform, and 
 starting from a point T which is located at the end of the envelope of said pseudo-cylindrical inner cavity of said body of said preform, said internal contour comprising a spherical surface generated by an arc of a circle of radius RK of which the length is equal to half the inside diameter K of said preform and a center V of said arc of a circle of radius RK is located on said axis xx′; said point T is located at the same level as said center V, meaning that projection of said point T onto said axis xx′ coincides with said center V, and a distance Z between said center V and said point OP of said bottom of said preform corresponds to ½K+(C−D), meaning to half the inside diameter K of said preform, plus the thickness C of said bottom of said preform, measured along said axis xx′, and minus a thickness D which corresponds to a difference between said radius RK and a distance separating said center V of said arc of this radius RK relative to said central point S, said value of D being defined as a function of said thickness B of the wall of said cylindrical body of said preform, and
 still for said internal contour of said bottom of said preform, a connection between said spherical dome of radius RH and said spherical surface created by said arc of a circle of radius RK, consists of a toroidal annular surface created by an arc of a circle of radius RL which is located in a generating plane passing through said axis xx′ and having a center Y located between said central point S and said point V, in a plane perpendicular to said axis xx′, said center Y being positioned on a circle centered on said axis xx′ and having a radius RI for which the value is established as a function of said outside diameter Ae of said preform, and 
 both for said internal contour and for said external contour of said bottom of said preform, the values of RE, M, RG, RH, RK, RL, D, RI, and C are determined in the following manner: 
 
 for RE: 0.5×Ae<RE<0.7×Ae, 
 for M: 5°<M<20°, 
 for RG: 0.25×Ae<RG<0.5×Ae, 
 for RH: 0.7×Ae<RH<1.3×Ae, 
 for RK: RK=½K, 
 for RL: 0.6×RK<RL<RK, 
 for D: 0.2×C<D<0.6×C, 
 and for RI: 0.05×Ae<RI<0.1×Ae, 
 where: 
 Ae is an outside diameter of said body of said preform; 
 B corresponds to a thickness of the wall of said body of said preform at the start of said cylindrical portion of said preform; 
 C corresponds to the thickness of the wall of said preform at said bottom of said preform, along said axis xx′, with, for C: B<C<1.1×(B); 
 K is the inside diameter of said pseudo-cylindrical cavity of said cylindrical body, at said bottom of said preform. 
 
     
     
         12 . The preform according to  claim 11 , wherein, for said external contour of said bottom, said connection between said outside envelope of said cylindrical body and said tapered envelope, at a point N, is in the form of a rounded surface of a radius RF that is on the same order as radius RE and, preferably, is equal to ½×(Ae). 
     
     
         13 . The preform according to  claim 11 , wherein said radius RE of said spherical cap of said external contour is on the order of 0.53×(Ae). 
     
     
         14 . The preform according to  claim 11 , wherein said half-angle M at said top of said tapered surface of said external contour is on the order of 10°. 
     
     
         15 . The preform according to  claim 11 , wherein said radius RG of said toroidal ring of said external contour, which extends between said spherical surface and said tapered envelope, is on the order of 0.32×(Ae). 
     
     
         16 . The preform according to  claim 11 , wherein said radius RH of said central spherical dome of said internal contour is substantially equal to ½(Ae), meaning to half said outside diameter Ae of said cylindrical body. 
     
     
         17 . The preform according to  claim 11 , wherein said radius RL of said toroidal annular surface of said internal contour, which acts as said connection between said spherical surface and said central spherical dome, is on the order of 0.8×(K/2). 
     
     
         18 . The preform according to  claim 11 , wherein said radius RI of a circle which is traced by a center of the toroidal annular surface has a value which is on the order of 0.07×(Ae). 
     
     
         19 . The preform according to  claim 11 , wherein said construction thickness D of the wall of said bottom, along said axis xx′, is on the order of 0.41×(C). 
     
     
         20 . The preform according to  claim 11 , wherein said thickness C of the wall of said bottom, along said axis xx′, is on the order of 1.02×(B).