THREAD FORMATION FOR CLOSURE STRUCTURES

Abstract: A closure structure which includes a container neck (24) having an external thread (34) to be engaged by an internal thread (58) of a closure body (30) for drawing the closure body (30) tightly down onto the container neck (24). The external thread (34) of the container neck (24) includes a pad (44) on a bottom thread turn (36). A sealing element (64) of the closure body (30) is drawn downwardly onto a sealing surface (70) of the container neck (24) to effect a seal. The pad (44) is sized to have a depth which causes the internal thread (58) of the closure body (30) to be drawn downwardly during the final portion of the screwing-on of the closure body (30) to the container neck (24). The presence of the pad (44) reduces axial clearance between the external thread (34) of the container neck (24) and the internal thread (58) of the closure body (30) to prevent axial displacement of the closure body (30) from the container neck (24) to prevent leakage due to the sealing element of the closure body (30) being axially displaced from the sealing surface (70) of the container neck (24).

Description: 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 multi-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. 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 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 multi-piece closure assembly, the assembly being mounted onto a container; or the two components can be a container neck and a closure component. 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. 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. BRTEF DESCRffTION 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 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 thread formation 34 of the container neck 24. The thread formation 58 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 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, 58 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 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 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, 58 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 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. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Claims: WHAT IS CLAIMED IS: 1. A threading arrangement for engaging a first closure component to a second closure component, comprising: a first closure component having a first sealing surface; a second closure component having a second sealing surface; a first thread formation on an outside of the first closure component and comprising a plurality of thread turns; a second thread formation on an inside of the second closure component and comprising a plurality of thread turns; and wherein one of said first thread formation and said second thread formation includes a pad which extends axially from one thread turn of said plurality of thread turns of said one thread formation, said one thread turn of said one thread formation being the last thread turn to be engaged by a respective other of said first and second thread formations in a screwing-on direction of said second closure component to said first closure component, said pad being overrun by said respective other of said first and second thread formations and being of a sufficient height to draw said second closure component in an axial direction on said first closure component to resiliently press said first sealing surface to said second sealing surface. 2. The threading arrangement of claim 1, wherein and said first thread formation comprises a first bottom turn and said second thread formation comprises a second bottom turn, and said pad is formed on said first bottom turn of said first thread formation, and said pad comprises an inclined leading face in a screwing-on, tangential direction to allow said second bottom turn of said second thread formation to overrun said pad to draw said second sealing surface down upon said first sealing surface. 3. The threading arrangement of claim 1, wherein said first closure component comprises a closure body and said second closure component comprises a container neck. 4. The threading arrangement of claim 3, wherein said second closure component includes a dispensing orifice. 5. The threading arrangement of claim 1, wherein said one thread turn comprises a first bottom turn of said plurality of turns of said first thread formation, and wherein said second thread formation comprises a second bottom turn of said plurality of turns, and wherein said first thread formation is arranged to be loosely engaged by said second thread formation until said second bottom turn of said second closure component overruns said pad. 6. The container closure arrangement according to claim 1, wherein said one thread formation comprises said first thread formation, and said second closure component comprises a resilient seal element, said second sealing surface carried on said resilient seal element and arranged to be contacted by said first sealing surface of said first closure component when said second closure component is drawn down onto said first closure component, and said pad comprises a sufficient height to resiliently compress said seal element when said pad is overrun by said second thread formation of said second closure component.

Inventors: HICKOCK ALAN P, HICKS MARGE M, KNUDSON DAVID J, LEUTHARD MITCH J, RANDALL JEFFREY T, HICKOCK, ALAN, P., HICKS, MARGE, M., KNUDSON, DAVID, J., LEUTHARD, MITCH, J., RANDALL, JEFFREY, T.
Applicants: SEAQUIST CLOSURES, SEAQUIST CLOSURES FOREIGN, INC.
Application year: 2001
Main classification: B65D
IPC codes: B65D41