U.S. patent application number 12/775712 was filed with the patent office on 2010-09-16 for tapered thread structure.
This patent application is currently assigned to PORTOLA PACKAGING, INC.. Invention is credited to RIchard D. Lohrman, Mike Lynn Peters.
Application Number | 20100230374 12/775712 |
Document ID | / |
Family ID | 38610377 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100230374 |
Kind Code |
A1 |
Peters; Mike Lynn ; et
al. |
September 16, 2010 |
TAPERED THREAD STRUCTURE
Abstract
In one embodiment there is provided a novel container neck
finish having a substantially cylindrical exterior wall surface
surrounding an orifice defined in the container and a thread
structure positioned about the exterior wall surface. The thread
structure in one aspect has at least a first portion, a second
portion positioned substantially axially below the first portion,
and a third portion positioned substantially axially below the
second portion. The first, second, and third portions, being
inclined with respect to the other portions provide a screw on neck
finish. The effective maximum diameter of the first portion is less
than the effective maximum diameter of the second portion to define
a first to second separation distance. And the effective maximum
diameter of the second portion is less than the effective maximum
diameter of the third portion to define a second to third
separation distance.
Inventors: |
Peters; Mike Lynn; (New
Castle, PA) ; Lohrman; RIchard D.; (North Aurora,
IL) |
Correspondence
Address: |
JAMES P. HANRATH
191 NORTH WACKER DRIVE, SUITE 1800
CHICAGO
IL
60606
US
|
Assignee: |
PORTOLA PACKAGING, INC.
Batavia
IL
|
Family ID: |
38610377 |
Appl. No.: |
12/775712 |
Filed: |
May 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11379101 |
Apr 18, 2006 |
7735664 |
|
|
12775712 |
|
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Current U.S.
Class: |
215/44 ; 215/252;
215/256; 215/329 |
Current CPC
Class: |
B65D 1/0246 20130101;
B65D 41/3428 20130101 |
Class at
Publication: |
215/44 ; 215/252;
215/329; 215/256 |
International
Class: |
B65D 39/08 20060101
B65D039/08; B65D 41/04 20060101 B65D041/04 |
Claims
1. A method of applying a threaded cap to a threaded neck of a
container, the method comprising the steps of: providing a threaded
neck of a container that includes thread structure having at least
one single thread extending entirely around the exterior wall
surface, the at least one single thread having at least a first
portion, a second portion positioned substantially axially below
the first portion, and a third portion positioned substantially
axially below the second portion, the first, second, and third
portions, being inclined with respect to the other portions to
provide a screw on neck finish, the first, second, and third
portions further having a corresponding effective maximum diameter,
and wherein the effective maximum diameter of said first portion is
less than the effective maximum diameter of said second portion and
the effective maximum diameter of said second portion is less than
the effective maximum diameter of said third portion, whereby the
effective maximum diameter of the thread structure changes
throughout the section of the exterior wall surface, said threaded
neck further having a neck wall having an exterior with a bead-like
structure surrounding said neck positioned axially below said
thread structure; placing a threaded cap at an angle offset from a
vertical axis defined by said threaded neck; moving the container
and/or moving the cap towards each other such that a neck edge
defined by the exterior of said neck wall comes into contact with a
cap edge defined by an interior wall of said cap, wherein upon said
contact a clearance space is defined between an upper edge of the
exterior defined by said neck wall and a free edge of the interior
wall of said cap; leveling said cap onto said threaded neck of said
container such that said cap is urged towards a substantially
vertical position on said threaded neck.
2. The method of claim 1 wherein the step of leveling said cap in a
substantially vertical position on said threaded neck further
includes contacting said cap with a skid plate or roller to level
and align the cap and container to one another.
3. The method of claim 1 wherein the step of leveling said cap onto
said threaded neck of said container urges a tamper-evidencing band
defined on said cap vertically downward past said thread
structure.
4. The method of claim 1 further including the step of screwing
said cap on said container in complimentary threaded
engagement.
5. The method of claim 1 further including the step of snapping
said cap on said container in complimentary threaded engagement by
axial force.
6. The method of claim 3 further including the step of downwardly
urging said cap onto the threaded neck such that said
tamper-evidencing band defined on said cap is placed over said
bead-like structure surrounding said neck wall.
7. The method of claim 6 wherein said placement over said bead-like
structure includes said tamper-evidencing band having an
upwardly-inwardly extending annular flange whose free edge engages
said bead-like structure and, in a stressed state, diametrically
expands while traveling over said bead-like structure during said
downward urging and ultimately returns to an unstressed state of
reduced effective diameter following passage over said bead-like
structure.
Description
CROSS REFERENCE TO RELATED INVENTION
[0001] The present invention is a divisional application of U.S.
patent Ser. No. 11/379,101.
FIELD OF THE INVENTION
[0002] The present invention relates to tapered thread structures
on a container finish and a corresponding closure.
BACKGROUND
[0003] Thread structures used on containers can take a wide variety
of designs. The details of any one particular thread structure on a
container is influenced by many factors, including the contained
contents, operational aspects of the complimentary closure,
materials, methods of package manufacture and consumer use.
[0004] A particularly useful and widely accepted closure/seal
system for packages is to position external threads on the
container which mate with internal threads positioned on the
interior wall of a closure. As is well known, the closure is
removed and reapplied by rotary threading action.
[0005] One factor requiring attention with threaded closure systems
is the circumferential extent of mating thread engagement between
closure and container. One may desire to minimize circumferential
thread engagement to only that required for adequate closure
retention for a number of reasons. These include avoiding
requirements for excessive turning during closure manipulation by
the consumer. Moreover, equipment associated with rotary capping
operations is normally restricted in the number of "turns" of the
closure allowed during initial application. On the other hand,
there must be enough thread engagement for proper threading and
sealing on application. A common "rule-of-thumb" in classic
packaging technology is that at least a single turn of thread
engagement should be incorporated into the designed thread
engagement between the fully applied closure and container. This
"rule-of-thumb" is most often adequate for packaging using classic
materials and fabrication, such as combinations of rigid glass
containers and rigid polystyrene or polypropylene closures. In
these cases the complimentary threads have been designed to be
relatively massive (such as the familiar modified buttress design)
with substantial thread depth. In this way the required surface
contact between the topside of the closure thread and the underside
of the container thread is normally achieved with one turn (360
degrees) of complimentary thread engagement.
[0006] It is common to deviate from the "classical" packaging
designs, materials, and fabrication for a myriad of reasons, such
as, to provide lightweight packaging by thinning the wall sections
and structural improvements. However, when providing lightweight
packaging other concerns such as part flexibility and distortion
are increased. Another example is the choice of alternate materials
such as low density polyethylene (LDPE) for the closure, taking
advantage of the unique properties of LOPE. In these cases, if one
wishes to employ a threaded closure, the classic one turn
"rule-of-thumb" may not be adequate to ensure proper retention of
the applied closure. This is a result of the added flexibility of
thin walling or the inherent relative flexibility of the LDPE
materials. In some cases a minimal amount of internal container
pressure, such as that experienced when the container may be
dropped, is sufficient to cause the closure skirt to expand to the
point where the closure simply pops off. This flexibility can also
allow localized distortion of the closure to the point where the
closure threads "strip" relative to the mating container threads.
This stripping action normally initiates at the bottom end of the
closure thread where the hoop strength of the closure is at a
minimum. At that position, radial distortion of the closure skirt
allows disengagement of the mating threads. Continued torquing
causes the disengagement to proceed helically upward in a "tiring"
manner until finally the mating threads "jump" over each other.
This stripping mechanism is not only of concern on initial
application, where such stripping can result in an unseated
closure, but also in the hands of the consumer expecting reseal
integrity.
[0007] In order to adjust for the inherent flexibility of LDPE
materials, designers have often chosen to dramatically increase the
circumferential extent of mating thread engagement. However, when
maintaining a single lead thread, the amount of turning required to
apply and remove the closure can become excessive for rotary
capping and/or convenient consumer manipulation. These concerns can
be addressed by using multiple lead threads. In this case, the
total thread engagement approximates the sum of the circumferential
extent of each of the multiple leads. In addition, the multiple
leads are circumferentially distributed around the lower portion of
the closure skirt to thereby balance the distortional forces
involved in closure torquing. On the other hand, multiple lead
threads normally require an increased helical angle (vs.
horizontal) for the thread and/or an uniformly finer thread. An
increased helical angle can lead to closure back-off or
unintentional unthreading or even loosening of the thread. In
addition, an uniformly finer thread will decrease the amount of
radial thread overlap thereby reducing the ability of the system to
withstand closure distortions. Such threads will also promote cross
threading during application due to the decrease target presented
to the closure thread lead by the reduced container thread
pitch.
[0008] It is clear to those skilled in the art that substitution of
LDPE materials for more rigid materials, while accomplishing
benefits unique to LDPE, also involves performance tradeoffs which
cannot always be recovered by the alternate designs advanced to
date.
[0009] Additional problems have arisen recently when attempts have
been made to employ certain closure designs using certain capping
practice. These problems can be broadly categorized as associated
with the capping process as opposed to the material choices for the
package components.
[0010] A first method of capping, known in the industry, involves a
"pick and place" operation. This method includes positive
positioning of a closure within a gripping chuck which is then
moved directly over a container. The chuck is simultaneously turned
and moved axially toward the container to screw the closure onto
the container finish. This application method is similar to actual
manual application. Further details of this application method
appear in the "Detailed Description Of Preferred Embodiments" which
follows in the Specification.
[0011] An alternate, less expensive, approach to closure
application can be characterized as a "pickoff" operation. During
"pickoff" a closure is held in a chute and positioned at an angle
relative to the axis of a container finish that passes beneath the
closure. The container finish comes into contact with the closure
and picks it off the chute. Unfortunately, the "pickoff" approach
can lead to certain difficulties associated with structural design
and material selection as will be more fully explained herein in
association with prior art FIG. 4. These difficulties and the novel
solutions are more fully described in the "Detailed Description of
Preferred Embodiments" to follow.
SUMMARY OF THE INVENTION
[0012] In a first embodiment of the present invention, a unique
neck finish for a container is provided. The neck finish includes a
substantially cylindrical exterior wall surface surrounding an
orifice defined in the container and includes a thread structure
positioned about the exterior wall surface. The thread structure
has at least a first portion and a second portion. Each portion has
a corresponding effective maximum diameter, wherein the effective
maximum diameter of the first portion is less than the effective
maximum diameter of the second portion.
[0013] Further elements of the first embodiment may include
providing a neck finish wherein the first portion is positioned
axially above the second portion. Alternatively, the thread
structure may have a convex surface projecting radially outwardly
from the exterior wall surface. The thread structure may also have
an effective maximum diameter that continuously increases from the
first portion to the second portion, or that incrementally
increases from the first portion to the second portion, or that
selectively increases from the first portion to the second
portion.
[0014] In a second embodiment of the present invention a neck
finish for a container is provided and has a substantially
cylindrical exterior wall surface surrounding an orifice and has a
thread structure. The thread structure has multiple portions of
convex surface regions projecting radially outwardly from the
exterior wall surface. Each of the portions has a point of maximum
separation from the exterior wall surface. The point of maximum
separation also defines an effective maximum diameter associated
with the portion. A selected first portion has an effective maximum
diameter less than a selected second portion positioned axially
below the first portion.
[0015] Additional elements of the second embodiment may provide for
multiple portions being positioned to form a helical path extending
circumferentially around the exterior wall surface and being
characterized by having a maximum effective diameter of a portion
positioned at an upper segment of the helical path being less than
the maximum effective diameter of a portion positioned at a lower
segment of the helical path.
[0016] In a third embodiment of the present invention a neck finish
for a container is provided in combination with a container
closure. The neck finish is defined as having an upper orifice that
defines an opening, a downward extending neck wall below the
opening, a thread structure positioned on the exterior of the neck
wall, and a first bead-like structure surrounding the neck wall
positioned axially below the thread structure. The thread structure
has a first portion and a second portion positioned axially below
the first portion. The first and second portions have a
corresponding effective maximum diameter such that the effective
maximum diameter of the first portion is less than the effective
maximum diameter of the second portion. The container closure has a
top, a downwardly extending skirt portion depending from the top.
The skirt portion has an interior, and a radially inwardly
projecting member adapted for engagement with the first bead-like
structure, such as a second bead-like structure or a J-band
structure, positioned within the interior of the skirt portion.
[0017] The third embodiment may include other elements such as
providing a thread structure to include multiple portions
positioned to form a helical path extending circumferentially
around the exterior of the neck wall and characterized by having a
maximum effective diameter of a portion positioned at an upper
segment of the helical path being less than a maximum effective
diameter of a portion positioned at a lower segment of the helical
path. Alternatively, a clearance space may be provided when the
container closure is initially applied to the container neck for
closing. The clearance space would be disposed between an upper
edge of the exterior of the neck wall and a free edge of the
interior of the skirt portion. The clearance space may provide
decreased interference or increased clearance with said first
portion, and/or provide resistance to stripping under the action of
torque applied to said container closure.
[0018] The radially inwardly projecting member on the container
closure may include a tamper-evidencing band frangibly connected to
the downwardly extending skirt portion and having an inwardly and
upwardly turned retaining rim adapted for engagement with the first
bead-like structure.
[0019] In a fourth embodiment of the present invention, a method of
applying a threaded cap to a threaded neck of a container is
disclosed. The method includes providing a threaded neck of a
container that includes thread structure having a first portion and
a second portion positioned axially below said first portion. The
first and second portions have a corresponding effective maximum
diameter such that the effective maximum diameter of the first
portion is less than the effective maximum diameter of the second
portion. The threaded neck further includes a neck wall having an
exterior with a bead-like structure surrounding the neck positioned
axially below the thread structure. Next, a threaded cap is placed
at an angle offset from a vertical axis defined by the threaded
neck. Then, the container and/or the cap are moved towards each
other such that a neck edge defined by the exterior of the neck
wall comes into contact with a cap edge defined by an interior wall
of the cap, wherein upon contact a clearance space is defined
between an upper edge of the exterior defined by the neck wall and
a free edge of the interior wall of the cap. Next, the container
and/or cap are further moved towards each other with the cap in
contact therewith. Last, the cap is leveled onto the threaded neck
of the container such that the cap axis is urged towards a
substantially vertical position on the threaded neck. The fourth
embodiment may further include contacting the cap with a skid plate
or roller to level and align the cap and container to one another.
Additionally, it may include urging a tamper-evidencing band
defined on the cap vertically downward past the thread structure
and/or urging the tamper-evidencing band over the bead-like
structure surrounding the neck wall. In addition, a step may be
included to screw the cap on the container in complimentary
threaded engagement, or to snap the cap on the container in
complimentary threaded engagement by axial force,
[0020] The present invention has a number of embodiments any one of
which may or may not include a number advantages over the prior
art. One advantage is to teach an inventive container finish
contributing to the facile application of closures incorporating
depending tamper evidencing band structure. Another advantage is to
improve the integrity, seal, and reliability of threaded closure
systems while maintaining consumer ease of use. A further advantage
is to permit choice of low density materials for threaded closures
while eliminating some detrimental consequences previously
accompanying such a choice.
[0021] Numerous other advantages and features of the invention will
become readily apparent from the following detailed description of
the invention and the embodiments thereof, from the claims, and
from the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0022] A fuller understanding of the foregoing may be had by
reference to the accompanying drawings, wherein:
[0023] FIG. 1 is a side elevational view, partially in section, of
a typical prior art container finish.
[0024] FIG. 2 is a side elevational view, partially in section, of
a prior art threaded closure.
[0025] FIG. 3 is a side elevational view showing a condition that
exists during application of the closure of FIG. 2 to the container
finish of FIG. 1 when using one method of closure application.
[0026] FIG. 4 is a side elevational view showing a condition which
may result using a alternate method to apply the closure of FIG. 2
to the container finish of FIG. 1.
[0027] FIG. 5 is a side elevational view, partially in section, of
a novel container finish according to an embodiment of the present
invention wherein the thread structure has a variable outward
projection as it traverses its vertical helical path.
[0028] FIG. 5a is a side elevational view, partially in section, of
a novel container finish according to an embodiment of the present
invention wherein the variable outward projection of the thread
structure incrementally increases as it traverses its vertical
helical path.
[0029] FIG. 5b is a side elevational view, partially in section, of
a novel container finish according to an embodiment of the present
invention wherein the variable outward projection of the thread
structure selectively increases as it traverses its vertical
helical path.
[0030] FIG. 6 is a side elevational view showing application of the
closure of FIG. 2 to the container finish of FIG. 5 when using the
closure application method embodied in FIG. 4.
[0031] FIG. 7 is a side elevational view showing a combination of
the container finish of FIG. 5 combined with the closure of FIG. 1
at an intermediate point during application of the closure.
[0032] FIG. 8 is a side elevational view showing the combination of
the closure of FIG. 2 after complete application to the container
finish of FIG. 5.
[0033] FIG. 8a is a side elevational view showing the combination
of a closure having a bead-like engagement structure after complete
application to the container finish of FIG. 5.
[0034] FIG. 9 is a side elevational view embodying the structural
distortions occurring when a closure thread "strips" as a result of
its inability to accommodate applied torque.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0035] The embodiments of the invention will now be described in
detail in conjunction with the descriptive figures. While the
invention is susceptible to embodiments in many different forms,
there are shown in the drawings and will be described herein, in
detail, the preferred embodiments of the present invention. It
should be understood, however, that the present disclosure is to be
considered an exemplification of the principles of the invention
and is not intended to limit the spirit or scope of the invention
and/or the embodiments illustrated.
[0036] Referring now to FIG. 1, there is shown a side elevational
view partially in section of a portion of a typical container
finish according to the prior art. Finish 10 has a cylindrical base
structure 12 surrounding an orifice 14. The base structure 12 has
an exterior wall 16 that further defines an exterior diameter of
the wall 16, commonly referred to as the "E" diameter.
Correspondingly, the wall 16 is commonly referred to as the "E
wall" of the finish 10. In the prior art embodiment shown, the "E
wall" has a substantially constant diameter over the entire
vertical extent of the finish 10. This uniform diameter is not a
requirement for prior art finishes. Positioned on the "E wall" and
protruding radially outwardly therefrom is a thread structure
18.
[0037] The thread structure 18 can take many sectional forms as is
known in the art. In addition, the thread structure 18 can comprise
multiple leads and various pitches as is known in the art. The
diameter defined by the exterior projection of the thread structure
18 is commonly referred to as the "T diameter". The effective "T"
diameter is twice the radial distance from the finish axis to the
point of maximum projection at a particular position along a
helical thread path or horizontally directed bead. The upper
portion of the thread structure 18 has an upper thread start
indicated by numeral 20. The vertical distance between the
uppermost point of thread structure 18 and the uppermost point on
top surface 22 of base structure 12 is commonly referred to as the
"S dimension" of the finish 10, as shown.
[0038] Below the thread structure 18 there is often present a
retention bead-like structure 19 outwardly projecting from the "E
wall". As is known in the art, this retention bead-like structure
19 serves as a retention feature, cooperating with suitable
structure defined on a cap, as later discussed herein, such as a
closure tamper evidencing band to retain the band during initial
closure removal. The diameter defined by the maximum extent of this
retention bead-like structure is commonly referred to as the "A
diameter" as shown.
[0039] Referring now to FIG. 2, there is shown a side elevational
view, partially is section, of a portion of a typical prior art
closure 30. The closure 30 has a generally disk-like top 32.
Depending from the top 32 is a cylindrical skirt 34 that has an
inner wall 36. An internal thread structure 38 projects inwardly
from the inner wall 36. The internal thread structure 38 can take
many sectional forms as is known in the art. In addition, the
internal thread structure 38 can comprise multiple leads, various
pitches, etc. as is known in the art. Often, prior art closures
further comprise a tamper evidencing band depending from the lower
edge 40 of the cylindrical skirt 34 through a frangible attachment.
Such a tamper evidencing band is indicated in the simplified FIG. 2
embodiment by numeral 42. In the FIG. 2 embodiment, the tamper
evidencing band 42 is connected to the cylindrical skirt 34 through
a frangible line of weakness 43. The frangible line of weakness 43
comprises multiple bridges 44 separated by spaces 46 extending
around the circumference of the closure 30. The particular band
structure of the FIG. 2 closure is a "J-band" type. Further details
of the structure and operational aspects of the "J-band" type
tamper evidencing band can be found in the U.S. Pat. No. 6,484,896,
the disclosure of which is hereby incorporated herein in its
entirety by reference. The tamper evidencing band 42 includes an
inwardly-upwardly directed flange 48, which has an upper free edge
49. The flange 48 can pivot around a thin hinge-like connection 50
thereby allowing the effective diameter defined by free edge 49 to
expand or contract somewhat easily.
[0040] When combining a prior art closure, such as that of FIG. 2,
with a prior art finish, such as shown in FIG. 1, one will
recognize that the corresponding threads should have compatible
structural characterization such that they mesh or mate in the
complementary intended fashion.
[0041] Turning now to FIG. 3, there is embodied one method of
applying closure 30 to container finish 10. The FIG. 3 embodiment
shows that the closure 30 is firmly grasped within the concavity of
chuck 52. Various methods of achieving such secure and positive
closure placement within such a chuck 52 are known in the art. The
chuck and closure are moved to a position, such as depicted in FIG.
3, where the axes of the closure and container are effectively
co-linear. Subsequently, relative axial motion (closure moves down
or container moves up) accompanied by relative rotation causes the
closure to be positively screwed onto the container finish. After
application is complete, the chuck releases its grip on the
closure. This "pick and place" application of a closure to a
container is very effective and reliable, simulating actual manual
application. Unfortunately, factors such as equipment costs and
spatial requirements may prohibit this approach.
[0042] An alternate, less expensive, approach to this closure
application can be characterized as a "pickoff" application as
illustrated at prior art FIG. 4 discussed hereafter. The "pickoff"
approach envisions a cap chute functioning to position a closure at
a defined angle relative to the axis of a container finish passing
beneath the chute. This is commonly referred to as the "pickoff"
position. The vertical height of the closure retained by the chute
is adjusted such that the closure finish contacts the lowermost
edge of the closure skirt or tamper evidencing band while passing
beneath the chute, thereby "picking" the closure from the chute.
Following closure pickoff, the container normally passes under a
device such as a skid plate or roller functioning to level and
align the closure and container axes and to loosely affix the
aligned closure to the container using relatively light vertical
pressure. The container/closure combination is then transported to
a subsequent application station to fully seat the closure. In the
case of a snap-on closure, this application station can take the
form of a simple mechanism applying axial force to the closure.
Thus this method has enjoyed widespread favor for applying snap-on
closures.
[0043] In the case of a screw-on closure, the application station
following "pickoff" may consist of various mechanisms to impart
relative rotation between the closure and container. In many cases
rotation alone is expected to result in proper threading and
seating of the closure. Thus if the pickoff is not adequately
"square" cross-threading can be a problem. In other cases, if the
closure is insufficiently seated during pickoff, the closure and
container threads may have insufficient vertical overlap to
properly mesh as a result of simple rotation. In these cases more
complicated top loading may be required. Those skilled in the art
will recognize that while the "pickoff" method employs relatively
simple, inexpensive equipment compared to rotary chuck application,
many more closure/container design factors must be proper to
achieve satisfactory "pickoff" closure application.
[0044] Regarding the "pickoff" method of closure application, some
closure designs, particularly certain tamper evident closure
designs, present additional difficulties. Many of the tamper
evident closure concepts incorporate a tamper evidencing band
depending from the lower edge of the primary closure skirt through
a frangible connection.
[0045] One such design that is particularly effective in its tamper
evidencing performance is the "i-Band" design illustrated in the
simplified embodiment of FIG. 2. One form of this design concept is
taught and illustrated in much greater detail in U.S. Pat. No.
6,484,896 ("896"patent) to Ma, the entire contents of which are
herein incorporated by reference. The "i-Band" closures taught in
the "896" patent include a tamper evidencing band comprising an
upwardly-inwardly extending annular flange whose free edge
ultimately engages the lower surface 21 of a container bead (such
as retention bead-like structure 19 of FIG. 1) upon completion of
initial application of the closure to the container. The flange may
incorporate pleats which allow the flange free edge to easily
diametrically expand during downward movement over a container bead
restriction but to assume a substantially reduced effective
diameter as it relaxes to its unstressed state following passage
past the bead. The function of the tamper evidencing band is
enhanced by the large changes in effective diameters of the free
edge of the flange responding to minimal expansion forces. The
embodiments discussed herein can be applied when using many other
closures incorporating the basic "i-Band" concepts, including both
threaded closures and "snap-on" closures.
[0046] One skilled in the art will recognize that in general there
will exist an optimal value for the difference in effective
diameters for the flange free edge between the fully expanded and
relaxed conditions. However, as will be shown, the appropriate
diameter in the relaxed condition has considerable influence on the
ability of such a closure to be properly applied by the "pickoff"
method.
[0047] Turning now to FIG. 4, there is shown a "snap-shot" view of
a hypothetical condition existing during a prior art "pickoff"
application. The container finish 10 of FIG. 1 is about to "pick"
the closure 30 of FIG. 2 from a retaining device (not shown). The
finish 10 has its axis directed substantially vertically and is
proceeding to the right in the FIG. 4 (direction of arrow 54 in the
figure) while maintaining the vertical axial orientation. The
closure 30 is in a position such that its axis is inclined to the
vertical, and is held in this position by a closure "pickoff"
retainer (not shown). As the finish 10 moves to the right, it
contacts the inwardly-upwardly directed flange 48. The closure 30
thus is pulled away from the pickoff retainer and attempts to
assume a position covering the top end 22 of finish 10. This
positioning is often assisted by passing the assembly under a
leveling device such as that depicted in FIG. 4 by numeral 56 which
applies slight downward pressure urging the closure axis toward a
substantially vertical position.
[0048] However, as is seen in the prior art FIG. 4 "snapshot",
vertical positioning of the closure 10 axis is prevented by the
abutment of the trailing portion of tamper band 42 and the
uppermost portion 22 of finish 10 at the position indicated by
arrow 58 in the FIG. 4 embodiment. This abutment is a consequence
of the contact between the finish thread 18 and the flange 48 of
tamper band 42 at the point indicated by arrow 60. The contact at
position 60 urges the closure 30 to move ahead of the container
finish and thus discourages the closure axis from assuming a
co-linear positioning with the finish axis. The abutment at arrow
58 prevents the leveling device 56 from "squaring" the closure 30
into a resting position covering the top open end of finish 10. The
cocked closure may be crushed or the container tipped over by the
leveling device. Alternatively, for example, in the case of soft PE
gallons and half gallons, the bottle simply is too weak to
counteract the forces and merely deforms and is unable to recover
during the torque phase resulting in the same cross threading.
Still further, should a cocked closure arrive at a final rotary
application station, a badly skewed, cross threaded cap can
result.
[0049] One will understand that, while the "pickoff" problems
illustrated in the snapshot view of prior art FIG. 4 used a
threaded "J-Band" closure, similar problems can occur with other
inwardly projecting tamper evidencing structure when combined with
outwardly projecting container finish structure in a "pickoff"
operation. The embodiments discussed herein are not limited to
those features associated with "J-Band" structure. Rather, the
embodiments of FIGS. 5 through 9 contemplate a container closure
having a top and a downwardly extending skirt portion depending
from the top wherein the skirt portion has an interior having a
radiallly inwardly projecting member 43 (see FIGS. 6 and 7) which
may, for example, take the form of either a "J-Band" structure (as
in 42, 48, and 49 of FIGS. 5 through 8) or a second bead-like
structure (as in 45 of FIG. 8a) which can be adapted for engagement
with an outwardly projecting container finish such as retention
bead-like structure 19 surrounding the neck wall of the neck finish
that is positioned axially below the thread structure.
[0050] Turning now to FIG. 5, there is shown in partial section a
neck finish 62 in accordance to one embodiment of the present
invention. In FIG. 5, neck finish 62 comprises a substantially
cylindrical wall 64 defining and surrounding an orifice 66. The
wall 64 has an exterior surface 68 which defines a diameter, the
"E-Wall" diameter of the finish 62. The "E-Wall" diameter is as
indicated in FIG. 5. In the FIG. 5 embodiment, the "E-Wall"
diameter is essentially constant throughout the vertical extent of
finish. However, the "E-Wall" diameter may not necessarily be
constant in all embodiments. Projecting radially outwardly from the
"E-Wall" is thread structure 70. In contrast to the thread
structure of the prior art finish of FIG. 1, the thread structure
of the FIG. 5 embodiment has a variable outward projection as it
traverses its vertical helical path. In the FIG. 5 embodiment, the
radial extent of the thread projection is at a minimum at the upper
thread portion and at a maximum at the lower end of the thread.
Thus, the thread can be characterized as having a variable
effective "T" dimension.
[0051] In FIG. 5, the thread structure 70 is shown as having a
single lead and having a "modified buttress" type section. Other
types of thread form, for example multi-lead thread structure,
segmented threads and symmetric sections, may be incorporated in
the embodiments discussed herein. In addition, the embodiments
discussed herein contemplate other types of radially projecting
structure such as essentially horizontal segmented or continuous
retaining beads associated with snap-on closure systems. As
illustrated in FIG. 5 the retaining structure projecting from the
"E-Wall" defines a variable effective "T" dimension which is
smaller in an upper region of the structure compared to a lower
region. In the FIG. 5 embodiment, the effective "T" dimension is
depicted as continuously increasing as the thread traverses
vertically downward. However, the "T" dimension can increase during
the downward travel in increments (illustrated in FIG. 5a as an
incremental increase of a number N) or selectively (illustrated in
FIG. 5b as a first increase by a first number A, and a second
increase by a second number B) as compared to the continuous
increase of the FIG. 5 embodiment.
[0052] Referring now to FIG. 6, there is shown the effect of
substituting the novel neck finish embodied in FIG. 5 for the prior
art finish of FIG. 1. FIG. 6 is a "snapshot" of a condition
occurring during a "pickoff" operation relative at a position
similar to that of prior art FIG. 4. It is seen in FIG. 6 that at
"pickoff" the initial contact is made between flange 48 of closure
30 and thread structure 70 of novel finish 62 at the point
identified by arrow 72 in the figure. However, because of the
reduced effective "T" dimension of the thread structure 70 in this
upper portion, the trailing edge of tamper band 42 of closure 30 is
not urged forward to the extent associated with the abutment at
arrow 58 of the structural arrangement embodied in prior art FIG.
4. Thus there is considerable clearance between the trailing edge
of tamper band 42 and the trailing upper edge of the "E-Wall" of
finish 62 in the region generally indicated by arrow 74 in FIG. 6.
With the possible assistance of a leveling device, such as leveling
plate or roller 56, the closure 30 easily is maneuvered to a
resting position squarely covering the open end of novel container
finish 62. Another problem solved by one or more of the embodiments
is that without the space 74 the "J band" can interact with the
threads and the horizontal nature of the threads can override or
affect the normal helical engagement of the threads.
[0053] The latter resting position of the closure following pickoff
is illustrated in FIG. 7. Here it is shown that the closure 30 has
been urged vertically downward over the finish 62, such as by
contact of the cap with the leveling pate or roller 56 of FIG. 6,
to the point where flange 48 has been caused to traverse the entire
vertical extent of thread structure 70. Moreover, the upper free
edge 49 of flange 48 rests under a lower portion of thread
structure 70 helping to retain the closure in a square position
with it axis effectively vertical. This retention not only
maintains closure positioning but also prevents closure/container
separation due to jostling or product foaming etc. until a final
screw or snap application station is reached.
[0054] FIG. 8 illustrates the result achieved during a final
application of the closure. In the final application station,
vertical force per arrow VF is applied by a capping head (not
shown) to move the "J Band" down the ramp to the bead 19 and
simultaneously cause thread engagement between the closure and
bottle finish. This is all done with the closure in the proper
axial alignment conducive to proper thread engagement and prevent
cross threading. The closure is twisted per rotational force arrow
RF to impart relative rotation between the closure and the bottle
finish to complete the complimentary thread engagement. The
relative vertical movement associated with this increased threading
causes the flange 48 to expand over retention bead 19 to allow free
edge 49 to come to its final position in abutment with the lower
surface 21 of retention bead 19. As is understood in the art, this
abutment of the free edge 49 with the lower surface 21 resists
upward movement of tamper band 42, thereby causing separation of
the band from the upper closure skirt 34 when the closure is
initially removed. It is understood that the twisting action
associated with the final application shown in FIG. 8 may take
other forms depending on the closure system. For example, with
snap-on closures or "snap-on/twist off closures, the final
application may consist of a simple axial movement accomplished
with straight vertical force.
[0055] A further aspect of one or more of the embodiments is an
increase in the ability of threaded closures to resist stripping
under the action of applied torque. This feature is illustrated in
conjunction with the situational embodiment of FIG. 9. FIG. 9 shows
a condition which can develop when a closure is subjected to
substantial application torque, either during initial application
or reapplication. As is known, the upper surface 80 of a closure
thread is often sloped upwardly/outwardly as is shown in the
closure embodiments of this specification. This slope causes a
component of the forces associated with the applied torque depicted
by arrow AT to be directed radially outward, tending to expand the
closure skirt. In general, the portion of the cap skirt least
resistant to expansion is the vicinity of the lower thread start of
the closure. Here, a number of structural factors result in
minimizing the hoop strength of the closure. Thus, under excessive
application torque, the hoop strength at the lower thread start is
unable to adequately resist the expansion forces generated by the
torque. The closure skirt expands as shown in FIG. 9, the expansion
as shown is concentrated at the lower thread start. Eventually,
thread engagement is lost at the lower thread start and the thread
continues to lose engagement in a "tiring" mode upward along the
helical path of the thread. Alternatively, for example in the case
of a thin PE bottle such as 5 gallon and 1 gallon used in the dairy
industry, the thin bottle thread finish distorts or deforms in a
similar fashion.
[0056] Classical methods of plastic closure manufacture included
unscrewing threads from the mold and use of relatively rigid
materials such as polypropylene. In these classic cases the closure
could be made very resistant to stripping. However, if one wishes
to manufacture closures using a simpler molding process wherein
threads are simply stripped from the mold, thread design and
material selection must be considered. These considerations, in
general, reduce the ability of the closure to resist stripping when
applied to a container.
[0057] The novel container finishes of one or more of the
embodiments can be adopted to recover some of the ability of
certain closure systems to resist stripping. This is a result of
the variable effective "T" dimension of the novel finishes taught
here. These finishes incorporate a reduced effective "T" dimension
in the upper portions of the container finish while expanding the
effective "T" dimension as the thread descends vertically to its
lower thread start (see FIG. 5). A fully applied closure having
essentially constant thread root diameter will thus have reduced
thread overlap with the container finish thread in the upper
regions of thread overlap. This will result in decreased
interference or increased clearance in these upper regions.
However, from a stripping perspective, thread overlap in these
upper regions is less critical, as suggested by the view of FIG. 9.
In the lower regions of the container finish thread, the effective
"T" dimension increases. Here, thread overlap is increased and
specifically in the region sensitive to initiation of stripping, as
explained above in the discussion of FIG. 9. Indeed, thread
dimensions can be specified to give selective thread interference
for some length of thread in this sensitive area. This interference
can be specified to extend only through a chosen portion of the
thread's helical path thereby ensuring that the closure is not
difficult to manipulate in the hands of the consumer. The
interference at the lower region of the thread permits facile
release of the thread by the consumer, since the interference is
relieved with just a short turn of the closure. In addition, the
interference can act as a brake to resist closure back-off in those
instances of multi-lead, high angled thread design.
[0058] When using low density polyethylene closures, typically
about 0.020 inch diameter interference at the lower thread start,
changing to 0.007 inch clearance at the upper thread start has
given positive results. These dimensions are only typical and could
vary considerably depending on structural design and material
selection.
[0059] It is noted here that a classic "rule-of-thumb" for closure
design is to ensure there be at least 0.001 inch of clearance
between the finish "T" diameter and the closure thread root
diameter in all cases. The current specification teaches a novel
consideration of purposely designing in selective thread
interference in those contact regions sensitive to closure
stripping. Such selective interference may give particular
advantage to systems employing thin walled closures or closures
fabricated from relatively flexible materials such as low density
polyethylene.
[0060] From the foregoing and as mentioned above, it will be
observed that numerous variations and modifications may be effected
without departing from the spirit and scope of the novel concept of
the invention. It is to be understood that no limitation with
respect to the specific methods and apparatus illustrated herein is
intended or should be inferred.
* * * * *