U.S. patent number 3,648,874 [Application Number 05/054,956] was granted by the patent office on 1972-03-14 for press-on, twist-off bottle cap.
This patent grant is currently assigned to Continental Can Company, Inc.. Invention is credited to Jens L. Moller.
United States Patent |
3,648,874 |
Moller |
March 14, 1972 |
PRESS-ON, TWIST-OFF BOTTLE CAP
Abstract
The closure cap herein described has a generally cylindrical
skirt with a circular lowermost edge. Corrugations in the form of
axial ridges and flutes terminate downwardly in a plane spaced from
the edge. The crests of the ridges and the cylindrical lip are
elements of a common cylinder. When the cap skirt is uniformly
constricted about threads of a bottle finish, material along the
lines of the flutes forms female thread elements, securing the cap
to the bottle. The ridges, the thread elements and the lip
constitute a knurling grid which affords a comfortable, sure finger
grip for twisting the cap off the bottle, with the smooth lip
surface shielding the edge.
Inventors: |
Moller; Jens L. (Westmont,
IL) |
Assignee: |
Continental Can Company, Inc.
(New York, NY)
|
Family
ID: |
21994609 |
Appl.
No.: |
05/054,956 |
Filed: |
July 15, 1970 |
Current U.S.
Class: |
215/252; 215/337;
215/328 |
Current CPC
Class: |
B65D
41/348 (20130101); B65D 41/0464 (20130101) |
Current International
Class: |
B65D
41/34 (20060101); B65D 41/04 (20060101); B65d
041/20 (); B65d 041/10 (); B65d 041/04 () |
Field of
Search: |
;215/40,43,42,39 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3303955 |
February 1967 |
Osborne et al. |
3465907 |
September 1969 |
Dorn et al. |
|
Primary Examiner: Hall; George T.
Claims
What is claimed is:
1. A closure cap for application to a bottle or the like, said cap
comprising: a top panel with a generally cylindrical skirt
depending therefrom and terminating downwardly in a circular
lowermost edge, at least that portion of said skirt which extends
from a first plane below said panel to said edge being formed of
sheet material of substantially uniform single thickness, said
skirt portion being corrugated so as to define a circumferential
series of straight outward ridges and straight flutes therebetween
extending from said first plane to a second plane spaced from said
edge, the crests of said ridges and the outer surface of said skirt
from said second plane to said edge lying on a common substantially
cylindrical surface.
2. The invention as defined in claim 1, said corrugated skirt
portion being sized for constriction about external thread
formations on the finish of a bottle so as to deform inward
portions of said material along the lines of said flutes over and
about portions of the thread formations and thereupon to form
female thread elements in said skirt conforming to the external
thread formations.
3. The invention as defined in claim 2, the depth of said flutes
being approximately the same as the depth of the external thread
formations, whereby, subsequent to said constriction, the outside
diameter of said skirt across the major diameter of said thread
elements will be substantially the same as the diameter of said
cylinder.
4. The invention as defined in claim 3, the depth of said flutes
being greater than the thickness of said material, whereby upon
generally uniform said constriction of the entire said skirt below
said first plane, the inside diameter of said skirt between said
second plane and said edge will be not less than the major diameter
of the external thread formations.
5. The invention as defined in claim 1, said skirt being weakened
around a circle in a plane between said second plane and said
edge.
6. The invention as defined in claim 5, said cap being adapted for
application to a bottle having a downwardly facing external
shoulder below the thread formations on the finish, said skirt
being of such length that a lip portion thereof below said circle
of weakening will extend below the shoulder when said cap is
applied to the bottle, whereby said lip portion can be formed into
engagement with the shoulder so as to form a tamper-proof closure
for the bottle.
7. A twistably removable closure cap for engaging external thread
formations on the finish of a bottle or the like, said cap
comprising: a top panel and a generally cylindrical skirt depending
therefrom and terminating downwardly in an edge, at least that
portion of said skirt which extends from a first plane below said
panel to said edge being formed of sheet material of substantially
uniform single thickness, said skirt being corrugated so as to
define straight outward ridges extending from said first plane to a
second plane spaced from said edge, there being flutes between said
ridges, portions of said skirt along the lines of said flutes being
conformed to elements of the external thread formations so as to
define female thread elements between said ridges, the crests of
said ridges and a circumferential band of said skirt immediately
downward of said second plane being elements of a hollow cylinder
having an inside diameter not substantially less than the major
diameter of the external thread formations, the other portions of
said skirt below said first plane lying substantially within the
outside diameter of said cylinder.
8. The invention as defined in claim 7, said ridge crests and the
crests of said female thread elements being rounded, the outside
diameter of said skirt across the major diameter of said female
thread elements being substantially equal to the outside diameter
of said cylinder, said ridges, said thread elements and said band
thereby defining a grid around said skirt adapted to shield said
edge and to afford a sure and comfortable finger grip for twisting
said cap off and on said finish.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a bottle cap of the press-on, twist-off
type. More particularly, the cap of this invention is of the type
adapted for formation of thread elements in the skirt upon
application of the cap to the threaded finish of a bottle so as to
secure the cap thereto.
2. The Prior Art
Crown caps have been generally used for beverage bottle closures. A
crown cap has a corrugated skirt which is normally crimped under a
collar or bead on the bottle neck. It has been proposed to apply a
crown cap to a finish having external threads or thread formations
to form a twist-off closure. However, the short, flared skirt of a
typical crown cap does not afford sufficient thread engagement upon
crimping to assure a secure closure with dependable twist
characteristics. The sharp corrugation ridges and the undulated,
projecting sharp edge do not afford a satisfactory grip for
twisting the cap. The cap is often hard to turn and the user may
cut his fingers on the edge. Reclosure is usually difficult and
impractical.
It has also been proposed to provide a cap of the crown type with a
protected edge. The lip of the cap may be curled, bent inwardly or
otherwise formed to shield the edge when the cap is on the bottle.
Such caps usually involve additional operations, additional
material, or both, as compared with crown caps heretofore in more
general use. Even the relatively small cost increases are a
considerable disadvantage in a highly competitive market.
Furthermore, there remains the difficulty of forming adequate
threads in the corrugated skirt typical of crown caps.
Caps suitable for roll-on thread formation have been marketed. For
this purpose, the cap is usually made of aluminum and is provided
with a cylindrical skirt which slips over the bottle threads when
the cap is pushed on. While the cap is held in sealing position
against the bottle lip, threads are rolled in the skirt, the
threaded finish constituting a die.
The material costs for the aluminum roll-on cap are generally
rather high. It is not ordinarily feasible to use commercial tin
plate or the like, because low cost varieties of such material do
not have satisfactory thread-rolling characteristics. The thread
rolling operation involves extra equipment and is generally slow,
as compared to the usual crown crimping operation. Furthermore,
thread rolling requires that most of the skirt be free of
corrugations or other such reenforcement, so that the skirt tends
to warp due to irregular stresses, fatigue and the like. Hence, the
twist-torque and reclosure characteristics of the roll-on cap are
often unsatisfactory. Reinforcing the skirt by means of beads,
curls, pockets or similar formations involves special tooling,
extra operations, or both, still further increasing the cost of
manufacture.
SUMMARY OF THE INVENTION
The cap according to this invention is designed to overcome the
several above-noted disadvantages of previously proposed caps,
affording a dependable press-on, twist-off cap for beverage bottles
and the like at a cost which compares favorably with that of
regular crown caps.
The cap has a generally cylindrical skirt depending from a top
panel. The skirt terminates downwardly in a circular edge. The
skirt is formed from single-thickness sheet material and includes a
corrugated portion whose length is about equal to the overall
length of the threads on the finish. The circumferential series of
corrugations define straight flutes and ridges, the crest elements
of which constitute elements of a common cylinder. The ridges
extend downward from a plane just below the top panel to a plane
spaced from the edge. The lower skirt or lip, extending from the
lower termini of the ridges to the edge, is a cylinder of
substantially the same diameter as that of the ridge crest
elements.
The root elements of the flutes lie on a cylinder sized for close
telescopic fit over the external threads on the finish to which the
cap is to be applied. The depth of the flutes is greater than the
thickness of the skirt material and about equal to the depth of the
finish threads. When the skirt is uniformly constricted about the
thread formations, female thread elements are formed in the skirt
by bending of material along the lines of the flutes, but otherwise
the skirt maintains its generally cylindrical configuration. The
flute depth being not less than the effective thread depth, the
constricted lip will clear the crests of the finish threads when
the cap is twisted off.
The cap according to this invention can be readily formed from
sheet material in a single stroke of a double-acting punch press,
using a simple blank-and-form die set. The cap configuration lends
itself to use of light-gauge tin-free steel, minimizing stress
cracking and spoliation of coating and decoration. The corrugations
are more numerous than is usually feasible on crown caps. The
closely spaced ridges provide a high degree of radial stiffness,
minimizing buckling upon constriction, so that the skirt thread
elements can be well-conformed to the finish thread formations,
providing secure retention and minimal tendency to warping of the
skirt. A greater lineage of thread engagement with given skirt
length is obtainable than with the corrugations usually provided in
standard crown caps.
After constriction, the outside diameter of the skirt across the
major diameter of the thread elements is about the same as the
diameter of the ridge crests and the subjacent smooth lip. The
resultant surface constitutes a knurl grid which affords a sure and
comfortable finger-grip for twisting the cap off and on the
bottle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a bottle cap according to this
invention;
FIG. 2 is an enlarged, fragmentary elevational view similarly to
FIG. 1, a portion of the cap being shown in vertical section taken
through one of the corrugation ridges;
FIG. 3 is a fragmentary vertical sectional view similar to the
sectional portion of FIG. 2, but taken through the root of one of
the corrugation flutes;
FIG. 4 is a fragmentary horizontal sectional view taken on line
4--4 of FIG. 2, showing the corrugation contour;
FIG. 5 is a view similar to FIG. 4, showing a variant of the
corrugation contour;
FIGS. 6 and 7 are views similar to the sectional views of FIGS. 2
and 3 respectively, but showing the cap applied to a bottle,
preparatory to constriction of the skirt;
FIG. 8 is an elevational view of the cap applied to a bottle, after
constriction of the skirt about the finish;
FIG. 9 is an enlarged fragmentary view similar to FIG. 8, partially
in section, showing details of the skirt thread elements;
FIGS. 10, 11 and 12 are views similar to FIGS. 2, 3 and 9
respectively, showing a modified form of the cap.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, cap 10 is proportioned for application to
thread formations on the finish of a bottle such as is used for
carbonated beverages. Skirt 11 is generally cylindrical,
terminating downwardly in a circular edge 12. The skirt 11 is sized
to telescope closely over the finish and to be secured thereto by
substantially uniform constriction of the skirt.
As seen in FIG. 2, cap 10 has a domed top panel 13, which is
connected to skirt 11 by a radiused portion 14, which defines a
seal recess, as subsequently seen. Skirt 11 is formed with a
circumferential series of corrugations 15 defining outwardly
projecting axial ridges 16 and flutes 17, extending from the bottom
of portion 14 to lowermost termini 18 in a horizontal plane spaced
from circular edge 12. The surface of lip 19, extending between the
plane of flute termini 18 and edge 12, lies on a cylinder of
substantially the same diameter as the cylinder on which lie the
crest elements of ridges 16. As best seen in FIG. 3, the depth of
flutes 17 is somewhat greater than the thickness of the material of
skirt 11, the depth being about that of thread elements to be
formed in the material along the lines of the flutes.
Referring to FIG. 4, the preferred corrugation pattern is
characterized by ridges 16 somewhat narrower than flute width W.
The cap may be made of 55 No. steel sheet. A cap of that material
for a standard beverage bottle opening, preferably has about 40
corrugations. This corrugation pattern provides the radial
stiffness and circumferential contractibility requisite to
retention of the generally cylindrical configuration upon
application of radially inward pressure uniformly around and along
the skirt. The material indicated is substantially less costly than
the 75-90No. tin plate in general use for conventional crown caps
intended for the same service conditions as the cap here shown. The
root material is conformed to the inner circle, providing a
substantial lineage of material lying thereon. The material
defining the flutes 17 being thus preformed, fairly high temper
characteristic of double-reduced, light gauge material is feasible,
requiring only moderate constrictive force to form thread elements
therein. Less severe deformation is involved in forming thread
elements along the lines of the flutes than is the case with
typical crown cap corrugations.
FIG. 5 shows another corrugation pattern for the same size cap as
that of FIG. 4. In the pattern of FIG. 5 the corrugations are
generally sinusoidal, the flutes 217 having substantially the same
radii as the ridges 216. This corrugation pattern provides generous
radii at crests and roots which minimize malformation and tearing
in the forming operation.
FIGS. 6 and 7 show cap 10 in position upon a bottle 20, preparatory
to constriction of skirt 11 about the thread formations 21 on
finish 23. A gasket or liner 24 extends along panel 13 and radius
14, so as to seal on top and around the side of lip 25, when cap 10
is pressed down. Flutes 17 are substantially coextensive with the
axial extent of threads 21, the material of the skirt along the
lines of the flutes closely opposing the crests of the threads. The
ridges 16 and lip 19 are radially spaced from threads 21, the
clearance corresponding to the depth of the flutes.
Cap 10 can be applied in a crowning machine of the type generally
used for applying crown caps. Suitable tooling is indicated
fragmentarily in phantom lines, comprising sealing punch 40, sleeve
punch 50, squeeze die 60 and back-up ring 70. Die 60 is made of an
elastomeric material, rubber for example. While cap 10 is held in
the sealing position shown, by means of punch 40, punch 50
descends, compressing die 60 against ring 70. Die 60 deforms and
exerts uniform inward radial pressure around and along skirt 11,
constricting it about finish 23.
FIGS. 8 and 9 show the cap 10 after constriction of skirt 11, with
female thread elements 22 formed therein upon constriction. As here
shown, threads 21 comprise half-turn elements of a compound thread.
The pitch is somewhat greater than the thread width at the pitch
circle. This is a preferred form of threading, providing ample
thread engagement, yet with wide roots to accommodate thread
elements 27 formed by radially inward displacement of material
along the lines of flutes 17 between threads 21. The coarse thread
pitch will establish rather high localized bending stresses in the
skirt material bearing along the crests of threads 21. This assures
close conformation of the skirt material along the lines of flutes
17, across and about the threads 21, thereby creating a number of
female thread elements 22 engaging elements of finish threads 21.
The total pitch-line lineage of engagement is about equal to WxNxT,
wherein W is the flute width (FIGS. 4, 5), N the number of flutes
and T the number of thread turns of the finish threads. This
structure provides excellent retention characteristics under high
thrust, even with a large thread helix angle. Compounding the
threads 21, as shown, enhances ease of removal and replacement of
the cap. A short twist frees the cap for removal and develops a
tight seal on reclosure, at moderate torque.
When uniform constrictive forces are applied, the material of the
skirt along the lines of flutes 17 bears on the crests of the
threads 21. The material bends over and around the threads due to
the high localized bending stresses developed. The material
defining the ridges 16 does not bear on the threads. Hence,
substantial bending stresses do not develop in the ridge material.
Furthermore, the ridges 16 are sufficiently stiff to obviate
buckling under shear stresses imposed by bending of the material
along the flutes. The ridges 16 remain straight, while providing
the accordion effect to evenly accommodate reduction of the skirt
diameter. This accordion effect obviates irregular buckling or
wrinkling. Upon completion of the constrictive deformation, the
diameter across the crest elements of ridges 16 is less than the
original diameter by an amount about equal to the double depth of
the threads 21. Also, the outside diameter of the skirt across the
major diameter of the female thread elements 22 is about the same
as the diameter across the crests of the ridges 16.
The cylindrical contour of lip 19 is substantially unaffected by
constriction stresses, the lip being restrained against scalloping
or curling by the stiffening effect of the ridges 16. Upon
constriction, lip 19 has an inside diameter slightly greater than
the major diameter of thread formations 21. Then, upon unscrewing
cap 10, lip 19 clears thread formations 21.
The length of flutes 17 is substantially the same as the total
axial thread length of the threads 21, thus assuring ample thread
engagement. The depth of the flutes is about equal to the depth of
the threads 21, this dimensioning being conducive to forming
well-defined thread elements 22, closely conformed about the
threads. Because of the stiffening effect of the ridges 16, the
constricted cap has good shape-retention characteristics, conducive
to true-running thread engagement, for low-torque twist-off and
good reclosure characteristics. The general stiffness of the skirt
is such as will afford good resistance to warping, which might
otherwise result from irregularities or locked-in stresses
developed either in originally forming the cap or in forming the
closure.
As previously observed, lip 19 is cylindrical. The crests of ridges
16 and thread elements 22 are of the same diameter, being elements
of a common cylinder, and are rounded. The generally cylindrical
grid thus formed constitutes a fine knurl with smoothly contoured
outermost surfaces, affording a comfortable, sure finger grip. The
skirt can be gripped firmly without cutting or abrading one's
fingers. With moderate grip pressure required there is little risk
of a finger being cut by curling over the edge. Easy twisting of
the cap is facilitated by the well-formed threads in the skirt and
minimal tendency to ovality, warping, or cocking, which assures a
low ratio of torque to sealing pressure, yet with relatively coarse
threading, as preferred for quick release and reclosure. These
easy-opening features are particularly advantageous in soft-drink
bottles which are commonly opened by children.
The configuration of FIG. 4 is particularly conducive to good
thread formation and retention characteristics. Root elements 217
are initially inwardly concave. Less severe deformation is involved
in conforming the material upon and about the threads 21. The
necessary constriction of the skirt can be generally achieved with
somewhat less radial pressure than will be the case of the inwardly
convex root configurations of the corrugations shown in FIG. 5.
However, the choice as to number and form of corrugations requires
giving due consideration to the properties of the cap material, cap
size, thread form, bottle finish quality and related factors.
MODIFICATION
FIGS. 10 and 11 illustrate a tamper-proof form of the cap, parts
corresponding to those in FIGS. 1-9 being given the same reference
numbers with the addition of 100. Cap 110 is similar to cap 10,
except for greater skirt length beyond the corrugations,
corrugation length being the same in both caps, for the same
threading. Skirt 111 depends from panel 113 along radius portion
114, with ridges 116 and flutes 117 having termini 118 in a plane
spaced from the edge 112. However, there is a longer cylindrical
portion 119 between the plane of corrugation termini 118 and edge
112 than the corresponding marginal portion or lip 19 of the
regular cap.
Portion 119 is lanced intermediate the corrugation termini 118 and
edge 112, so as to cut a circumferential series of narrow slots
130. Then a series of short, frangible bridges 131 connect the
upper and lower bands of marginal portion 119. The orientation and
spacing of bridges 131 are so selected that each bridge is aligned
with a ridge 116. Except for minor adaptation of the tools to
accommodate the longer skirt and for the lancing operation, cap 110
can be made in the same manner as cap 10.
Aluminum is a preferred material for the cap 110. Aluminum is
usually more satisfactory and economical than steel for caps of the
tamper-proof type. Aluminum generally provides the most desirable
combination of ductility for forming and requisite frangibility of
the bridges.
Referring to FIG. 12, cap 110 is applied to the finish 120 in the
same general manner as above described with respect to the regular
cap of FIG. 1. Lip 132 is crimped under shoulder 133, below threads
121. This crimping operation can be performed simultaneously with
the general constriction of the skirt, by means of a compressible
die similar to die 60 (FIG. 6). Lip 132 being remote from ridges
116, and aluminum being highly ductile, a generally uniform radial
constrictive pressure sufficient to conform skirt 116 to the thread
formations 121 will usually suffice to crimp the lip 132 against
shoulder 133. Alternatively, lip 132 can be crimped, rolled or spun
under with an auxiliary die or tool. Collar 135 prevents excessive
constriction of skirt portion 134 and bridges 131. Cap 10 can also
be applied to this style of finish, if desired.
After completion of the closure as described, the tamper-proofing
means of cap 110 operates in the same manner as with other caps
having similar frangible bridge structure. The engagement of
inturned lip 132 under shoulder 133 inhibits rise of the cap upon
initial application of twist-off torque. Thereafter the twist
torque and camming action of the threads impose sufficient stress
on bridges 131 to fracture them. The lip portion 132 then drops
down, visually signalizing attempted opening, even though the body
of the cap be not actually twisted off. After the bridges are
broken, the body of the cap can be twisted off to open the bottle.
The body of cap 110 is substantially the same as cap 10, as to
form, thread formation, grip, easy twist-off and reclosure. The
inside diameter of the constricted skirt portion 134 and the bridge
circle are slightly larger than the major diameter of threads 121.
Hence, the body lip and remnants of the bridges will clear the
threads when the body of the cap is unscrewed.
Referring again to FIGS. 2, 3, 9 and 10, it will be seen that the
cap shell of either type can be readily formed from sheet material
in a punch press with simple blank-and-form tooling. The equipment
and set-up used can be substantially that used for manufacturing
conventional crown caps, with comparable production rates and
overall economy. Dies for the regular and tamper-proof types may be
of similar design, differing essentially only in blank size and
depth.
The regular cap of FIG. 1 has a skirt 11 of about the same length
as that of a conventional crown cap for a similar bottle. Hence,
the blank size for the plain cap of the invention is about the same
as the blank for the crown cap; correspondingly, the same quantity
of caps in each case can be made from about the same square footage
of material. Since the regular cap here described can be produced
from low-cost tin plate or tin-free steel of lighter gauge than has
been found feasible with crown caps, for reasons above noted, the
total material and cost thereof for the cap of this invention is
generally less than for conventional crown caps.
The tamper-proof cap of FIGS. 10-12 has the same length and form
above bridges 131 as the complete regular cap, for the same bottle
size and finish. Only so much additional material is required as
corresponds to the width of the tamper proofing band 132. Either
regular or tamper-proof type may be made shorter than the nearest
equivalent practical roll-on type of cap.
The caps according to this invention are adaptable to relatively
fine threads, because of their suitability to thread formation by
means of a compressible die. In contrast, a cap designed for
roll-on thread formation is generally suitable for application only
to fairly wide, coarse-pitch threads. The localized high tool
pressure involved with thread rolling necessitates liberal tool
bearing spun to obviate tearing of the cap skirt and to minimize
tool or bottle breakage consequent upon jamming of the solid
rolling tool between threads or excessive side pressure on the
tool. Correspondingly, a roll-on cap generally requires a
substantially longer skirt than that of an equivalent cap of this
invention for comparable thread engagement. Thus, the caps here
described afford greater economy of material as compared with
roll-on types, with respect to both blank size and gauge. Lighter
gauge is feasible due to lesser risk of tearing or warping when
applying uniform overall pressure, as compared with the highly
concentrated pressure of the thread-rolling operation.
It will be seen from the foregoing that the closure cap according
to this invention affords improved performance and economy, as
compared to prior caps employed in similar applications. The caps
above described are designed for application to the threaded bottle
finish shown by way of example. It will be understood that the cap
of this invention is adaptable to thread forms other than that here
shown, or to thread equivalents such as cam lugs, or the like.
* * * * *