Abstract:
Screw on caps for bottles that have an anti back off feature formed on a hinged tab of the cap engaging detent teeth below the threads on the bottle. The hinge has a unique configuration that enables the tab to snap into and hold a gripping position while avoiding temporary distortion or creep. The detent teeth are particularly suited for use with blow molded bottles and are capable of restraining a cap within a small angle of a fully tightened position to avoid any significant back off and potential leakage. In one embodiment, the anti back off feature is provided in a child resistant cap while in another embodiment this feature is provided in a simpler continuous thread cap.

Description:
This application is a continuation of application Ser. No. 09/314,372, filed May 19, 1999, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to cap and bottle packaging and, in particular, to screw on caps for bottles with externally threaded neck finishes. 
     PRIOR ART 
     Screw on bottle caps have a tendency to loosen from a tightened condition on a threaded bottle neck finish. This tendency has a number of causes which include temperature change, creep in the bottle and cap materials, relaxation of a liner or sealant material, and vibration during handling and shipping. This problem is more frequently encountered when the screw threads have a high pitch to enable the cap to be quickly removed and reinstalled with limited twisting action. Loose caps create problems for the manufacturer and retailer of packaged goods and even for the ultimate user. Loose caps can falsely indicate tampering and, of course, allow spillage or leakage of the contents as well as entrance of moisture into the container. A good moisture seal is especially important, for example, when pharmaceuticals and dietary supplements can be adversely affected by excess moisture content. While “anti back off” features are known in the industry, these features have not generally been available with caps that have child resistant features. 
     Certain child resistant screw on caps have sections that flex on hinges for movement between locked and unlocked conditions. It has been difficult to provide a hinge with desirable spring back and creep resistant properties while avoiding thick wall sections. 
     SUMMARY OF THE INVENTION 
     The invention provides a screw on cap and bottle construction that resists back off or loosening of the cap from a tightened, closed position. The cap includes a hinged portion that carries stop surface areas engageable with complementary stop surface areas on the bottle. The cap hinged portions have spring back characteristics that assure reliable operation of the anti back off surface areas. 
     In one disclosed embodiment, the bottle, ideally a blow molded product, has a stop surface area that provide a child resistant function and other surface areas for achieving the anti back off function. In the cap, the child resistant and anti back off features are produced on finger manipulatable hinged levers that include separate surface areas for these features. 
     The disclosed hinge construction achieves highly reliable spring characteristics that assure both child resistant and anti back off properties. The spring characteristics of the hinge allow relatively small closely spaced surface formations to be used on the bottle to obtain high angular resolution in the anti back off function. The spring hinge performance allows proper results to be achieved despite the difficulty in obtaining precise closely spaced surface formations in blow molded bottles. The anti back off stop surface elements have unique complementary configurations that are particularly suited for blow molded bottles and that enhance their performance. As disclosed, where desired the hinge construction can be used to obtain an anti back off function in threaded caps without child resistant properties. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a bottle and cap assembly embodying the invention; 
     FIG. 2 is a fragmentary perspective view of the bottle of FIG. 1; 
     FIG. 3 is an exploded perspective view of the cap of FIG. 1; 
     FIG. 3A is a fragmentary enlarged perspective view of a part of the cap of FIG. 1; 
     FIG. 4 is a cross sectional view, taken in the plane  4 — 4  indicated in FIG.  1  through the neck finish of the bottle; 
     FIG. 5 is a fragmentary view like FIG. 4 on an enlarged scale; 
     FIG. 6 is a perspective view of the bottom of the cap of FIG. 1; 
     FIG. 7 is a fragmentary cross sectional view of the cap taken in the plane  7 — 7  indicated in FIG. 1; 
     FIG. 8 is a fragmentary cross sectional view of the cap taken in the plane  8 — 8  indicated in FIG. 1; 
     FIG. 9 is an exploded perspective view of a cap and bottle in accordance with a second embodiment of the invention; 
     FIG. 10 is a perspective view of the underside of the cap of FIG. 9; 
     FIG. 11 is a fragmentary cross sectional view of the cap and bottle of FIG. 9 in assembled relation, taken in a plane transverse to the axis of the cap and bottle neck, and showing details of an anti back off feature; 
     FIG. 12 is a fragmentary cross sectional view of the cap taken in the plane indicated at  12 — 12  in FIG. 9; and 
     FIG. 13 is a fragmentary cross sectional view of the cap taken in the plane indicated at  13 — 13  in FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 through 8, there is shown a screw on cap and bottle combination embodying the invention. The cap  10  is of a type disclosed in U.S. patent application Ser. No. 08/835,826, filed Apr. 16, 1997. The cap  10  is an injection molded one piece unit of suitable thermoplastic material such as polypropylene. The cap  10  includes an end wall  11  and inner and outer generally concentric cylindrical skirts  12 ,  13  depending from the end wall  11 . The inner skirt  12  has a pair of double helix threads  14  projecting radially inward from an interior generally cylindrical surface  16 . The outer skirt  13  is somewhat longer in the axial direction than the inner skirt  12 . The outer skirt  13  is circumferentially discontinuous with small axially extending gaps  17  on opposite sides of finger operated levers  18 . The levers  18 , which are identical, are disposed at diametrally opposite sides of the outer skirt  13  and as discussed more fully below, permit the cap to be unscrewed for opening the bottle, designated  20 , when both are simultaneously squeezed inwardly at their tops. Other parts  21  of the outer skirt are fixed to the end wall and to the inner skirt. The gaps  17  are substantially closed at their lower ends by small formations  19  that project circumferentially towards the adjacent edge area of the outer skirt. The formations  19  serve to prevent nesting of identical caps when they are handled in bulk. Alternatively, the formations or projections  19  can be on the main parts of the outer skirt and can extend towards the levers  18 . 
     Each lever  18  is integrally joined to the inner skirt  12  by a hinge  26 . The lever  18  has an upper portion  27  and a lower portion or tab  28  above and below its hinge  26 , respectively. The levers  18  have an arcuate cylindrical cross section in planes transverse to the axis of the cap and are concave with reference to the interior of the cap. 
     As shown in FIG. 7, for example, the hinge  26  extends radially between the inner skirt  12  and the mid-section of the lever  18 . The hinge  26  has a limited wall thickness measured in the axial direction of the cap  10  preferably not greater than the nominal wall thickness of the cap. By way of example, the cap when constructed with a nominal thread size of 33 mm can have a nominal wall thickness of 0.050 in. 
     As shown in FIG. 3, the hinge  26  is configured such that it occupies planes transverse to the axis of the cap  10  that are spaced an axial distance greater than the thickness of the hinge measured in the axial direction. In the illustrated embodiment, this configuration is step-like in form having a lower level area  31 , a riser area  32  and an upper level area  33 . The lower level area and riser area are duplicated on opposite sides of each lever  18 . It is contemplated that other non-planar hinge configurations can be used to practice the invention and achieve the desired results. For example, the hinge can have a configuration when viewed in a plane like FIG. 3 in which the upper and lower areas are reversed so that there are two upper areas and one central lower area. Still further, a non-planar configuration of the hinge and the hinge axis can be achieved by substituting a V-shape for the step shape of FIG. 3 or a arcuate shape for the step shape. Such shapes can be concave upwardly or downwardly as viewed in a plane like that of FIG.  3 . In all these examples, the pivot axis of the hinge deviates from a single plane or, more specifically, from a zone bounded by two planes spaced apart by the minimum thickness of the hinge. 
     The lower lever portion  28  on an inner face  36  has a stop member  37  with a major stop surface  38  that projects radially inwardly and slightly angularly rearwardly from the sense that the cap is installed and tightened forwardly, conventionally in a clockwise direction. 
     The bottle  20  is particularly useful for packaging medicines, nutritional supplements, and the like and is preferably made as a blow molded product of suitable thermoplastic such as polyethylene. The bottle  20  has a circular neck finish  41  that includes a circular mouth  40  and external threads  42 . The threads  42  are a double helix with a high helix angle to which the threads  14  of the cap  10  are complimentary. Below the threads  42  on opposite sides the bottle  20  includes major and minor stop surface formations  43 ,  44 . 
     At each side of the bottle  20  a major one of the stop surface formations  43  extends along the wall with a generally flat configuration preferably oriented slightly from a true radial plane to provide a slight undercut. As seen in FIG. 5, this major stop surface or formation  43  is sufficiently large that it is clearly reflected in the geometry of the underlying inside surface of the bottle. The major stop surfaces  43  make the cap child resistant because the cap cannot be readily unscrewed without squeezing the upper lever portions  27  towards one another typically with two fingers while simultaneously turning the cap. This technique is difficult for children to learn and to perform. When the upper lever sections  27  are squeezed, the lower sections  28  move generally radially outwardly so that their stop members  37  are out of interfering relation with the bottle stop surfaces  43  when the cap  10  is turned on the bottle  20 . 
     The minor stop surfaces or detents  44  are each comprised of a convex curvilinear form when viewed in a plane transverse to the axis of the cap  20 . This curvilinear profile extends along the bottle wall in the axial direction. The stop surfaces  44  are relatively small in proportion to the wall thickness of the bottle and do not result in a significant irregular underlying surface on the interior of the bottle. A study of FIG. 5 illustrates how a stop surface  47  on the cap stop member  37  interacts with the minor stop surfaces  44  on the bottle. The cap  10  is proportioned so that when it is assembled in a closed position on the bottle  20 , the cap stop surfaces  47  engage the minor stop surfaces  44  on the bottle  20 . The hinge  26  of each lever  18  is effective to resiliently maintain this surface-to-surface contact with a desired force level. When approaching the closed position, each lower lever portion or tabs  28  is carried radially outward as the stop member  37  rides onto a conical shoulder portion  48  of the bottle until the stop member or finger  37  passes the major stop surface  43  and the lower lever portion  28  closes radially inwardly. 
     Dimensional variations in the cap  10  and bottle  20 , as well as characteristics of any liner used in the cap, make it difficult to control the final angular position at which the cap is properly tightened. Variations in the angular position of the cap relative to the bottle for proper tightness is accommodated by the series of circumferentially distributed minor bottle stop surfaces  44 . The minor stop surfaces  44  extend over a relatively large arcuate zone on each side of the bottle  20  so that in any expected variation in the fully tightened position of the cap the cap stop surface  47  will always be in registry with an area of these stop surfaces  44 . 
     The bottle stop surfaces or teeth  44 , in the preferred embodiment, are characterized by a curvilinear or wavelike form. The circumferential spacing between successive peaks or valleys of the minor stop surfaces  44  is relatively small to enable the cap stop surface  47  to engage a minor stop surface at or sufficiently close to a final tightened angular position to maintain a seal between the cap  10  and bottle  20 . In the illustrated case, the cap stop surface  47  engages the majority of a peak of a minor stop surface  44 , engaging areas on both sides of the peak, and at least a portion of an adjacent valley. 
     The curvilinear configuration of the disclosed stop or detent formations  44  on the bottle is advantageous for blow molded bottles since it enables these formations to be accurately molded even while being spaced closely together. FIG. 5 shows that the cap stop surface  47  is concave and complimentary to a minor stop surface  44 , thereby enabling it to securely grip onto the last minor stop surface that it passes when the cap is tightened on the bottle. The mutually engaged cap and bottle surfaces  47  and  44  provide an anti back off function by preventing the cap from any significant unintended loosening or backing off from a closed sealing position. The resistance to opening developed by these anti back off stop surfaces  44 ,  47  is a function of the force between the surfaces that is maintained by the hinge  26  of the respective levers  18 . The disclosed multi plane hinge has demonstrated a superior resilience and resistance to creep. The hinge performance is important both for the cap&#39;s child resistant feature and the anti back off feature. The multi plane hinge  26  disclosed herein snaps back essentially fully to its child resistant position and its anti back up position after a lever is pivoted either during initial installation of the cap on the bottle or after the levers have been operated to release the cap and are thereafter pivoted to enable the cap to be reinstalled. 
     The location of the stop surfaces  44  on a wall of the bottle that is generally cylindrical and concentric with the axis of the neck finish has advantages in the provision of a reliable product. When the portion of the bottle forming the stop surfaces or detents  44  is blow molded, these surfaces tend to be more accurately formed when the wall of the bottle need only be expanded radially into the mold. Moreover, with the resulting axial orientation of the curvilinear forms of the stop surfaces  44  there is no variation in the detenting or anti back off function owing to a different angular and therefore different vertical position of the cap depending on where it ends up in a tightened position. The anti back off function of the detent or stop surfaces  44 ,  47  is particularly useful where, as shown, the thread pitch of the cap and bottle is high and friction locking forces in the threads are somewhat reduced. 
     FIGS. 9 through 13 illustrate another embodiment of the invention where a screw on cap  50  and bottle  51  are provided with an anti back off feature. The bottle  51  is preferably a blow molded part having a neck finish with a circular mouth  52  and external threads  53 . Below the threads  53 , the bottle  51  is formed with external detent teeth or stop surfaces  54  which in the illustrated embodiment are situated around the full circumference of the bottle. The detent teeth  54  are relatively small and closely spaced relative to one another. In the illustrated bottle  51 , the distance between the apex of adjacent teeth is not substantially greater than twice the wall thickness of the bottle in this area and the radial height of the teeth is less than the minimum wall thickness in this area, this thickness being about 0.040 in. where the bottle is sized to accept a nominal 63 mm cap. The teeth  54  have a generally curvilinear profile when viewed in a plane transverse to the axis of the bottle mouth  52  and such profile projects axially with reference to this axis. The teeth or detents  54  are relatively small in comparison to the wall thickness of the bottle and are not substantially reflected in the underlying interior surface of the bottle. 
     An intermediate external area  56  between the threads  53  and the teeth  54  is conical and flares radially outwardly in the axial direction from the threads and the teeth. The bottle is preferably formed of a suitable thermoplastic material such as polyethylene. 
     The cap  50  is preferably an injection molded one piece part of suitable thermoplastic material such as polyethylene. The cap includes an end wall  61  and concentric inner and outer skirts  62 ,  63 , respectively. The inner skirt  62  depends from the end wall  61  and includes internal threads  64  complimentary to the threads  53  on the bottle  50 . The outer skirt  63  is cylindrical but circumferentially segmented by axial extending slots  66  that separate identical diametrically opposite major skirt portions  67  from somewhat smaller hinged skirt portions  68  also diametrally opposed from one another. The major portions  67  are fixed to the inner skirt  62  by radially extending webs along their top edges and the majority of their vertical edges. The outer skirt  63  extends axially below a lower edge  69  of the inner skirt  62 . The slots  66  at their lower ends are effectively closed by small projections  70  formed at the lower ends of the major skirt portions  67  to prevent nesting. 
     The hinged portions or tabs  68  are supported on the inner skirt  62  by integral hinges  71 . The hinges  71  like the hinges  26  of the embodiment of FIGS. 1 through 8 exist in multiple planes transverse to the axis of the cap so that the pivot axis of the hinge  71  diverts from a flat plane perpendicular to the cap axis. The hinge  71  is axially stepped so that it has a pair of circumferentially spaced lower sections  72 , riser sections  73  and a central upper section  74 . 
     A locking post or formation  76  projects radially inwardly from an inside surface of each outer skirt hinged portion  68 . The post  76  has a stop surface detent area  77  that is complimentary in shape to the profile of the projecting bottle teeth  54 . As shown in FIG. 11, the cap stop surface  77  is concave so that it can receive a tooth  54  in the manner of a socket or detent and engage portions on both sides of the apex of the tooth. A leading surface  78  of the locking post  76 , in the sense of motion relative to the teeth  54  when the cap is screwed clockwise onto the bottle, has a convex configuration to enable it to be cammed radially outwardly over successive teeth  54 . The cap locking posts  76  and bottle teeth  54  work in a manner like that of the stop surfaces  47  and  44  of the embodiment of FIGS. 1 through 8. When the cap  50  is being assembled on the bottle, the locking posts  76  engage the conical surface  56  and are cammed radially outwardly until they overlie the area of the bottle teeth  54 . The hinges  71  enable the skirt portions or tabs  68  to resiliently accommodate this radial motion including that required for passage of the locking posts circumferentially across successive teeth  54  until the cap  50  has been tightened to a desired torque level and the bottle mouth  52  is sealed by the cap with any desired liner in the cap. 
     The cap  50  is proportioned and the hinges  71  act to resist movement of the locking posts  76  radially outwardly when, after tightening, the cap  50  tends to come loose by creep, relaxation of material, temperature and pressure changes, vibration, and the like. On each side of the cap  50 , the locking posts  76  will engage the last tooth  54  that each passes when the desired level of tightening is reached. The actual engagement can be where the tightened condition corresponds exactly with the angular registration between each locking post stop surface  77  and the teeth or later when internal forces tend to cause the cap to untighten or back off slightly. The close positioning of adjacent teeth  54  assures that any loosening movement would be less than that required to unseal the cap from the bottle. Engagement of the locking posts  76  with the teeth  54  prevent further backing off of the cap under normal internal influences. 
     The hinges  71  will allow the locking posts  76  to release their grip on the teeth  54  when a deliberate manual effort is applied to untwist the cap. The rounded surfaces of the teeth  54  cam the locking posts  76  radially outwardly in this instance so that at some torque level in the opening direction (typically counter clockwise), the constraint of the locking posts developed by the hinges  71  will be overcome. This release torque level can be selected by final design of the hinges, for example. 
     While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.