Note: Descriptions are shown in the official language in which they were submitted.
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THREAD FORMATION FOR CLOSURE STRUCTURES
TECHNICAL FIELD
The invention relates to thread formations for closure structures, such
as thread formations for use between two components of a mufti-piece
closure, or between a container neck and a closure. Particularly, the
invention relates to thread formations adapted to effect a tight seal between
the closure components or between the closure and the container neck.
BACKGROUND OF THE INVENTION
AND
TECHNICAL PROBLEMS POSED BY THE PRIOR ART
A common type of container has a threaded neck that is adapted to be
engaged by a threaded closure. Typically, the threaded closure is provided
with a closure body having threads for engagement with the container neck
threads. The body includes a dispensing feature, such as an end wall that
defines a dispensing orifice. A lid can be provided to close the orifice when
placed in a closed position with respect to the body. Typically, such
closures are installed onto container necks by automated capping machinery.
In containers utilizing threaded closures wherein the container or the
closure or both are fabricated from a resilient plastic material, under some
circumstances it may be difficult to maintain the closure sealed to the
container neck. Closures can become loosened or slightly axially displaced
on the container neck. This is' known as "chucking." Resilient thermoplastic
materials can cold flow under pressure which can result in a gradual
loosening of the closure on the neck of the container. Low coefficients of
friction between the closure threads and neck threads may also increase the
tendency of such closures to gradually become loosened, i.e., become slightly
unscrewed. A conventional threaded closure may undergo some amount of
back-off or loosening from the threaded container neck during shipment
and/or when subjected to rough handling.
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Prior known closure retention arrangements include the arrangement
disclosed in U.S. Patent 3,682,345, wherein a container thread includes a
projection on each thread turn for frictionally engaging the closure thread to
the container neck thread, to hold the closure to the container neck in a
sealed condition.
While a container thread arrangement having lugs or projections on
every thread turn will increase the torque required to loosen the closure from
the container neck, for the same reason, the torque required for initially
screwing on the closure to the threaded neck by an automated capping
machine is also significantly increased. This increased torque is present
throughout the entire rotational engagement of the closure to the threaded
container neck and increases the energy consumption of the capping machine.
The present inventors have recognized that it would be beneficial to
provide a closure and container arrangement wherein the torque required to
screw on the closure can be minimized to the greatest extent, while still
maintaining a tightly sealed closure to the container neck. The present
inventors have recognized that it would be beneficial to provide a closure
and container arrangement which resists chucking or inadvertent, undesired
axial movement of the closure with respect to the container neck due to
excessive clearance between the closure and container neck threads or by a
partial unscrewing of the closure from the container neck.
Also known are closure structures having first and second closure
components which are threaded together, wherein a preselected threaded
engagement between the components causes a sealing element of the first
component to seal against a sealing surface of the second component. For
example, the first component could be a closure body and the second
component could be a closure dispensing cap, threaded on the closure body.
The closure body could be sealed to a container and have a dispensing
channel therethrough and an upstanding valve element. The closure cap
could have a dispensing orifice that is closed by the valve element in a
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sealed position when the closure cap is relatively rotated (threaded) on the
closure body. These closure structures can utilize a preselected relative
rotational position between the components as the sealed position. This
preselected relative rotational position can be defined, for example, by one
or
more rotational stops, arranged on one or both components. At the
preselected relative rotational position, the components must also be at the
preselected threaded engagement to ensure sufficient sealing at the
preselected relative rotational position. The implementation of this
relationship has been problematical.
The present inventors have recognized that an adequate sealing
between the two closure components is dependent on such things as thread
tolerance and thread axial clearances, and that it would be desirable to
provide a threading arrangement that more reliably ensured an effective
sealing at a preselected relative rotational position between the closure
components.
The present inventors have recognized that it would be advantageous
to provide an improved threading arrangement for a closure structure which
has decreased susceptibility to closure loosening during shipping, storing and
handling.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a threading arrangement for a closure
structure that is arranged between two closure components, which, once
completely engaged, effects an effective axial sealing force between the two
components, and resists subsequent loosening of the components caused by
external forces, internal pressure of the contained product, or material
relaxation and/or cold flow of the resilient plastic of one or both
components. The two closure "components" can be two coacting parts of a
mufti-piece closure assembly, the assembly being mounted onto a container;
or the two components can be a container neck and a closure component.
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According to one aspect of the invention, when two threadedly
engaged closure components are intended to be sealed together around an
opening at a preselected relative rotational position, a pad or pads are
provided on one turn of one of the component threads to be overrun by a
thread turn of the respective other component as the preselected relative
rotational position is reached. During a last few degrees of threaded
engagement of the components as the preselected relative rotational position
is reached, the pad or pads are overrun by the thread of the respective other
of the components to draw the closure components together by a distance
equal to the height of the pad or pads to effect an adequate axial sealing
force between the components. If a resilient sealing element is arranged
between the components, it is compressed by the axial sealing force to seal
one component to the other component.
Another aspect of the present invention provides coacting thread
formations for engaging a closure body to a threaded neck of a container.
The thread formations of the present invention includes a first helical thread
formed on an outside of the container neck, and a coacting second helical
thread formed on the inside of the closure body. The first and second
helical threads can either be continuous or intermittent. The first helical
thread includes one or more pads arranged on a single turn of the helical
thread. The second helical thread is arranged to relatively loosely engage the
external first helical thread of the container neck until the second helical
thread reaches the first pad. The pad or pads formed on the first helical
thread of the container neck have a downwardly extending thickness which is
selected to take up a substantial amount of axial play or clearance between
turns of the helical threads of the thread formations. The invention thus
reduces the vertical clearance or play between the closure thread and the
container thread while also minimizing the torque required to apply the
closure body to the bottle neck.
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The pad or pads draw the closure body downwardly on the container
neck to seal thereto. The pad or pads can be of a preselected height to
cause compression, by a preselected amount, of a resilient seal element held
within the closure body by contact with the container neck.
According to one embodiment of the invention, the pad or pads are
substantially rectangular with angled end faces. The pads are formed to be
unitary with the first helical thread of the container neck and extend below
the lowest turn of the first helical thread.
When the container neck is formed as a portion of a bottle or other
container, the invention can be implemented inexpensively by an adjustment
to bottle tooling. No added material is required to form extrusion-blow=
molded bottles with the pad or pads on threads thereof, and minimal added
material is required to form injection-blow-molded bottles with the pad or
pads on threads thereof.
Although the aforementioned embodiment includes the pad or pads
located on the container neck, it is also encompassed by the invention to
provide the pad or pads on the closure body instead. In such an
embodiment, the pad or pads would be located extending upwardly from a
top turn of the closure body thread such that the closure body could be
nearly completely threaded on the container neck with minimum torque until
the container thread reached the pad or pads.
Numerous other advantages and features of the present 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 DRAWINGS
The accompanying drawings form part of the specification, and like
numerals are employed to designate like parts throughout the same,
FIGURE 1 is an exploded, elevational, fragmentary view of a
container neck and closure body of the present invention; and
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FIGURE 2 is an enlarged, fragmentary, sectional view of the
container neck and closure body of the present invention in a relative
position wherein the closure body is only partially screwed onto the
container neck; and
FIGURE 3 is a sectional view similar to FIGURE 2, but FIGURE 3
shows the container neck and closure body of the present invention in a
relative position wherein the closure body is fully screwed onto the container
neck.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While this invention is susceptible of embodiment in many different
forms, there are shown in the drawings, and will be described herein in
detail, only some specific embodiments thereof with the understanding that
the present disclosure is to be considered as an exemplification of the
principles of the invention and is not intended to limit the invention to the
specific embodiments illustrated.
FIGURE 1 illustrates a closure structure 20 comprising two closure
components, a container neck 24 and a closure body 30. The container neck
24 can be composed of a suitable material such as glass or plastic. The
closure body 30 is advantageously composed of plastic. The container neck
24 includes a helical thread formation 34 having a plurality of thread turns
including a lower turn 36 and an upper turn 38, the turns being discernible
by observing the thread formation in profile. The helical thread formation
34 can be continuous or intermittent. The thread formation 34 includes one
or more pads 44 (one shown) extending downwardly from the turn 36. If
plural pads are used, the pads can be spaced around a circumference of the
thread formation. Each pad 44 includes an angled or inclined leading face
44a, an inclined bottom surface 44b, and an angled trailing face 44c.
The closure body 30 includes a deck 46 and a depending skirt 48.
The deck 46 includes a dispensing nozzle 50. The skirt 48 includes an
internal helical thread formation 58 which is rotationally engageable with the
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thread formation 34 of the container neck 24. The thread formation S8
includes a plurality of thread turns including an upper turn 60, an
intermediate turn 62, and a bottom turn 63, the thread turns being discernible
by observing the closure body in section. A "crab's claw" seal 64, or
S another known compressible seal, is provided on an inside surface of the
deck 46. The seal 64 is resiliently compressed by a top sealing surface 70
of the container neck 24 when the closure body 30 is screwed onto the
container neck 24, forming a seal.
FIGURE 2 illustrates the thread formations 34, S8 before a final few
degrees of tightening. The seal 64 is not yet fully deflected or compressed
by the surface 70. The bottom thread turn 63 of the closure body 30 has not
yet encountered the pad 44 (located out of the plane of FIGURE 2 and
therefore not visible in FIGURE 2). A vertical clearance or play a exists
between the intermediate thread turn 62 of the closure body and the lower
1S and upper thread turns 36, 38 of the container neck 24. A vertical
clearance
a also exists between the upper thread turn 38 of the container neck 24 and
the upper and intermediate thread turns 60, 62 of the closure body 30.
Until the closure body thread turn 63 reaches the pad 44 (FIGURE 3),
the clearances a (Figure 2) between the closure body thread turns 60, 62, 63
and the container neck thread turns 36, 38 are sufficient for the threading
engagement to be relatively loose to permit reduced torque, quick and trouble
free screwing on or off of the closure body 30 to the threaded neck 24.
FIGURE 3 shows the closure body 30 fully tightened onto the
container neck 24 so that the seal 64 is resiliently pressed to the top
surface
2S 70 of the container neck 24. In this position, lower thread turn 63 is
drawn
downwardly under the pad 44. The pad 44 has an axial length or height b.
When the bottom turn 63 is drawn downwardly by the distance b, the axial
play a (FIGURE 2) between the thread formations 34, S8 is also reduced by
the amount b. The reduction is significant and prevents chucking of the
closure body 24 from the container neck 30. In one presently preferred
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embodiment, the dimension b is about 0.020 inch. In any event, the
engagement between the pad 44 and the closure skirt thread preferably does
not occur until near the end of the screwing-on process. Thus, the increased
torque required to engage the pad and move the closure to the final screwed-
on position is not required during most of the screwing-on process.
The location of the pad 44 may also be employed to allow outgassing
or venting of a pressurized container. As the closure is initially unscrewed,
the closure thread will quickly disengage from the pad, and the resulting
loose fit along the threads will serve as a flow passage for venting
pressurized gas (e.g., carbon dioxide from a shaken-up carbonated beverage
bottle).
The pad 44 is illustrated having a generally rectangular shape,
however other shaped are possible including semi-cylindrical, triangular,
tapered, etc. Also, the number of thread turns on the container neck and
within the closure body can be more or less than as shown, without
departing from the invention.
From the foregoing, it will be observed that numerous variations and
modifications may be effected without departing from the spirit and scope of
the invention. It is to be understood that no limitation with respect to the
specific apparatus illustrated herein is intended or should be inferred. Tt
is,
of course, intended to cover by the appended claims all such modifications
as fall within the scope of the claims.
