Abstract:
A unitary, plastic, snap-on overcap for providing a tamper-evident capability to a closure assembly of a container includes a cap, a removable skirt, and a plurality of spaced-apart frangible elements which connect the removable skirt to the cap. The closure assembly includes an internally-threaded fitting which is anchored into the container and an externally-threaded closing plug which is installed into the fitting. The cap portion of the overcap includes a depending sidewall which terminates in a snap-on lip portion. The removable skirt includes a wall portion which is constructed and arranged to be positioned in close proximity to an upper surface of the container when the cap is snapped onto the closure assembly. The actual snap-on engagement of the cap to the closure assembly involves engagement by the lip portion with a cooperating edge of the closure assembly. In order to gain access to an edge of the cap in order to pry the cap off of the closure assembly, the skirt must be removed. In order to remove the skirt, the spaced-apart frangible elements must be severed. The tamper-evident capability is created by placement of the skirt in close proximity to a surface of the container such that the cap cannot be pried off without first breaking one or more of the frangible elements. Breakage of any of the frangible elements provides a visual indication of a tampering attempt.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an all-plastic, tamper-evident overcap for the closure portion or component of a shipping and storage container. This container which is typically a steel drum includes a drum end or head which typically includes a closure for dispensing the contents of the container and a closure for venting the container. More particularly the present invention relates to a tamper-evident overcap which is constructed and arranged to snap fit onto a portion, typically a radially extending lip or circumferential edge, of the corresponding steel drum closure. 
     In one embodiment of the present invention a frustoconical outer skirt is connected to the cap by a series of frangible elements. In a related embodiment the outer skirt, while still tapered to some degree, has a more cylindrical appearance and comprises the outer wall of the overcap, prior to separation from the snap-on cap. In both embodiments the overcap is unable to be removed without cutting or tearing away the snapped-on cap portion or without removal of the skirt so that the cap portion can be pried off. Either approach provides a visible indication of a tampering attempt. If the skirt is removed by breaking the series of frangible elements that connect the skirt to the cap, it is then possible to pry off the cap from its snap-fit onto the closure, without giving any further indication of a tampering attempt. However, the absence of the skirt, if unauthorized, would visually indicate a tampering attempt. 
     The present invention is directed to use with large shipping containers or drums where one drum end is arranged with a plug-type closure and an internally-threaded fitting, typically with a threaded interfit between the two. Due to the limited thickness of the drum end material and the desire to create an internally-threaded dispensing port, an internally-threaded fitting or flange is typically anchored into the drum end or head so as to provide a dispensing opening. The method of anchoring the flange fitting into the drum end involves the forming or drawing of the drum end material into a raised and shaped pocket. The next step is to place the flange fitting into the pocket and then form or crimp the metal of the drum end onto and around the flange fitting so as to anchor these two components together. The flange fitting is internally threaded and receives a closing plug and cooperating annular gasket in order to seal closed the internally threaded aperture defined by the flange fitting. Threaded removal of the closing plug enables the contents of the drum to be dispensed. 
     Without some type of tamper-evident feature, the closing plug could be removed at virtually any time, such as during shipping or storage, without being noticed. This would mean that someone could tamper with the drum contents without being discovered. This tampering could include partial removal of the drum contents and/or contamination of the drum contents by a foreign substance. Having a tamper-evident feature provides a desirable enhancement to the plug-flange fitting combination. It then becomes important to configure a tamper-evident feature which is reliable, easy to install or assemble, and relative inexpensive. The unitary, molded plastic design of the present invention satisfies the “inexpensive” criteria. The snap-on or snap-fit design of the present invention satisfies the “easy to install” criteria and cooperates in satisfying the “reliable” criteria. The use of a removable (i.e., frangible) skirt as disclosed by the present invention satisfies the “reliable” criteria and does so in a novel and unobvious manner. 
     One of the keys to the success of the present invention is the placement of the underside (i.e., lower) edge of the frangible skirt against the surface of the drum end or at least in extremely close proximity to the surface of the drum end. By not leaving any noticeable clearance space or at most a space with only a few thousandths of an inch gap, there is effectively no room for a blade or edge of any type of utensil, implement, or hand tool to slide beneath the frangible skirt in hopes of removing the cap without this attempt being revealed by the fracture of one or more of the connecting frangible elements. As will be clearly explained, any such inserting and prying attempt causes the fracture of at least one of the frangible elements and this is sufficient to reveal (visually) that a tampering attempt has been tried. This tamper-evidencing feature is further enhanced by the dimensioning of the skirt relative to the snap-on portion such that with the nominal dimensions present the skirt is actually preloaded against the upper surface of the drum in one embodiment of the present invention. In a related embodiment of the present invention, the axial and radial spacing between the lower edge of the skirt and the lower edge of the snap-on lip of the cap are such that direct contact between the lower edge of the skirt and the upper surface of the drum end is not needed. 
     SUMMARY OF THE INVENTION 
     A unitary, plastic, snap-on overcap for providing a tamper-evident capability to a closure assembly of a container according to one embodiment of the present invention comprises a cap, a removable skirt, and a plurality of spaced-apart frangible elements connecting together the removable skirt and the cap. The closure assembly which is anchored to the container includes an internally-threaded fitting and a closing plug which is threadedly installed into the fitting. The cap portion of the overcap includes a depending sidewall which terminates in a snap-on lip portion. The removable skirt includes a wall portion which is constructed and arranged to be positioned in close proximity to an upper surface of the container when the cap is snapped onto the closure assembly. The snap-on assembly involves the lip portion of the cap engaging a cooperating lip portion of the closure assembly. Access to the lip portion of the cap in order to pry the cap free from the closure assembly is not possible until the skirt is removed from the cap, a step which requires the severing of the plurality of spaced-apart frangible elements. 
     One object of the present invention is to provide an improved unitary, plastic, snap-on overcap for providing a tamper-evident capability. 
     Related objects and advantages of the present invention will be apparent from the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a molded, plastic, snap-on overcap according to a typical embodiment of the present invention. 
     FIG. 2 is a front elevational view in full section of the FIG. 1 overcap as viewed along line  2 — 2  in FIG.  1 . 
     FIG. 3 is a enlarged detail, side elevational view of one portion of the FIG. 2 illustration. 
     FIG. 4 is a front elevational view of a closing plug comprising one portion of a closure assembly which cooperates with the FIG. 1 overcap in order to provide a tamper-evident capability. 
     FIG. 5 is a top plan view of the FIG. 4 closing plug. 
     FIG. 6 is a front elevational view in full section of the initial assembly involving a container, a flange fitting installed in the container, the FIG. 4 closing plug, and the FIG. 1 overcap. 
     FIG. 7 is a top plan view of a unitary, plastic, snap-on overcap according to another embodiment of the present invention. 
     FIG. 8 is a front elevational view in full section of the FIG. 7 overcap as viewed along line  8 — 8  in FIG.  7 . 
     FIG. 9 is an enlarged detail view of one portion of the FIG. 7 illustration. 
     FIG. 10 is an enlarged detail view of one portion of the FIG. 8 illustration. 
     FIG. 11 is a front elevational view in full section of the initial assembly of a container, a flange fitting installed within the container, a closing plug installed within the flange fitting, and the FIG. 7 overcap. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring to FIGS. 1,  2 , and  3 , there is illustrated a unitary, molded plastic, snap-on overcap  20  which includes a cap  21 , removable tamper-evident skirt  22 , and a circumferential series of frangible elements  23 . The cap  21  is a circular form with a substantially flat upper surface  24 , an inclined outer wall  25 , a cylindrical lower wall  26 , and a continuous annular snap-on lip  27 . The skirt  22  includes an annular connecting lip  28 , an inclined outer surface  29 , and a substantially cylindrical inner wall  30 . The inner wall  30  extends from the vicinity of connecting lip  28  and is radially inside of the outer wall  29  so as to define an intermediate annular clearance space  31  located between the inner wall  30  and outer wall  29 . The frangible elements  23  connect the lower wall  26  with the connecting lip  28 . There are a total of  24  frangible elements which are equally spaced around the circumference of lower wall  26 . 
     In the preferred embodiment the cap has an outside diameter of approximately 3.25 inches (8.26 cm) and a height of approximately 0.36 inches (9.14 mm). The centerline-to-centerline spacing between adjacent frangible elements  23  is approximately 15 degrees. The angle of incline of outer wall  25  is approximately 45 degrees and the axial height of lower wall  26  is approximately 0.15 inches (3.81 mm). Lip  27  has a radial width of approximately 0.12 (3.05 mm) inches and a substantially horizontal lower surface  27 ( a ). Lip  27  provides the snap-on capability for overcap  20  by sizing lip  27  relative to a screw-in plug  39 , as will be described hereinafter, such that the lip  27  fits around and beneath a radially-extending flange  40  which comprises part of the screw-in plug  39  (see FIGS. 4,  5 , and  6 ). 
     While the connecting lip  28  and the lower wall  26  are joined together by the  24  frangible elements  23  as part of the unitary, molded plastic overcap  20 , there is a clearance space  35  located between the cap  21  and the skirt  22 . This clearance space  35 , while generally annular in form, is actually segmented by the  24  frangible elements  23  into  24  arcuate portions  35   a.    
     The axial position of the skirt  22  relative to cap  21  is defined by the axial position of the under surface  36  of outer wall  29  relative to the axial position of lip  27 . Functionally, as the lip  27  snaps onto the flange  40  of plug  39  it is intended for under surface  36  to engage the upper surface  41  of drum end  42  (see FIG.  6 ). It is preferred for these axial heights (i.e., dimensions) to be set so that there is actually a slight preload applied to the outer wall  29  of skirt  22  after the snap-on of cap  21  onto the flange  40  of plug  39  is completed. This preload causes a slight degree of flexing in the outer wall  29  as it pushes down on upper surface  41 . Since the plug  39  is threaded into the flange fitting  43  which is anchored into the drum end  42 , there is a further interfit relationship which must be taken into consideration. 
     Beginning with the drum end  42  and the flange fitting  43  installed therein, a threaded aperture  44  is defined for receipt of the externally-threaded plug  39 . The outwardly-radiating flange  40  of the plug  39  (the snap-on portion for the cap) is drawn closer to the upper surface of raised portion  41   a  of upper surface  41  as the plug  39  is threaded advanced into the aperture  44  of the flange fitting  43 . An annular gasket  47  is positioned around the threaded body of plug  39  and beneath flange  40 . This gasket  47  is captured by and compressed between the underside surface  45  of flange  40  and upper surface of raised portion  41   a  by the threaded advancement of the plug  39  into aperture  44 . The gasket  47  helps to ensure a sealed interface and provides spacing beneath surface  45  and above raised portion  41 ( a  )for lip  27  to fit into as it snaps onto the outer peripheral edge of flange  40 . Once the plug is “fully seated”, meaning that the gasket  47  is compressed to the desired extent, the axial height (i.e., separation) between the underside surface  45  of the flange  40  and the upper surface  41  is set at a nominal distance of approximately 0.205 inches (5.21 mm)(dimension A). In a cooperating manner, the upper side surface  46  of the inner tip of lip  27  is axially spaced from under surface  36  a nominal distance of approximately 0.215 inches (5.46 mm) (dimension B). The nominal difference of approximately 0.010 inches (0.25 mm) between dimensions A and B creates the slight preload on skirt  29  as it is pressed against upper surface  41 . 
     The nominal dimensions for overcap  20  mean that the under surface  36  of outer wall  29  axially extends 0.012 inches (0.30 mm) below the lower surface  30   a  of inner wall  30 . However, the tolerances on the corresponding axial dimensions mean that the lower surface of inner wall  30  could abut up against the upper surface  41  of the drum end before the under surface  36  engages this upper surface  41 . While the dimensional stack indicates a maximum possible 0.008 inches (0.2 mm) of separation between surface  36  and surface  41 , this is still small enough to prevent the use of a tool to try and pry off the cap without first breaking one or more of the frangible elements  23 . 
     Inner wall provides an additional degree of stiffness and rigidity to skirt  22 , and in particular to outer wall  29 . The axial height of inner wall  30  is set so as to be recessed relative to under surface  36  by approximately 0.012 inches (0.30 mm)(nominal). As the outer skirt  22  is preloaded against upper surface  41 , the inner wall  30  provides an axial abutment so that the preload is not excessive. If the axial dimensions and relationships are such that the outer wall  29  of skirt  22  could otherwise be pushed too far into preloaded engagement to the point of fracturing one or more frangible elements, the inner wall  30  prevents this from occurring. 
     With reference to FIGS. 4 and 5, the externally-threaded, molded closing plug  39  is illustrated. Plug  39  has a unitary construction which includes a closed, externally-threaded body  50  which is received by the threaded aperture  44  of flange fitting  43 . Included at the upper end of body  50  is flange  40  which has a substantially cylindrical form, though relatively shallow, and radiates in an outwardly direction beyond the periphery of body  50 . Flange  40  includes upper surface  51  and underside surface  45 . Upper surface  51  is contoured with a recessed center portion  52  and four equally-spaced wrench slot  53  which are used for the automatic assembly of plug  39  into aperture  44 . Since the threaded advancing of plug  39  into aperture  44  is countered and resisted by the compression of gasket  47 , a torque measurement can be used to set the position of the plug  39  relative to aperture  44  and to also set the degree of compression of gasket  47 . 
     In a free state, flange fitting  43  is configured with a serrated outer edge and a slightly inclined flange portion leading to and defining the internally-threaded aperture  44  (see FIG.  6 ). The manner in which this flange fitting  43  is captured and secured within the formed pocket of the drum end is well known in the art and results in the final form which is diagrammatically illustrated in FIG.  6 . 
     Since aperture  44  is a through aperture, the plug  39  would be able to be threaded into the aperture until the underside surface  45  of flange  40  comes in contact with the drum end portion (i.e., raised portion  41   a ) which extends over the upper surface of the flange fitting  43 . However, the presence of annular gasket  47  prevents the flange  40  from bottoming out on the raised surface  41   a . In the assembled configuration including the annular gasket  47 , the outer edge of flange  40  is spaced apart from the upper surface of raised portion  41   a  by approximately 0.146 inches (3.71 mm). The clearance space left beneath the outer edge  54  of flange  40  is important so that lip  27  is able to snap beneath flange  40  for the described snap-fit assembly of the overcap  20  to the plug  39 . What has been identified as lip  27  is functionally a hook bead with a curved inner surface  55 , rounded tip  56 , and a lower surface  27   a . Upper side surface  46  is adjacent the tip  56  and comprises one end of surface  55 . Surface  46  comprises that portion of lip  27  which principally engages flange  40  for the snap-fit assembly of overcap  20 . The inside diameter of lip  27  measures approximately 3.012 inches (7.65 cm). Since the flange  40  of plug  39  has an outside diameter that measures approximately 3.075 inches (7.81 cm), lip  27  must flex in order to snap onto the plug  39 . However, once the lip  27  is positioned beneath flange  40 , this diameter size difference ensures that the overcap will remain on the plug unless the cap is destroyed or pried off. As illustrated in FIG. 6, the cap  21  snaps onto the plug  39  and is free of any direct connection to the container, represented in part by drum end  42 . The skirt  22  is also free of any direct connection to the container. 
     When it is time to properly access the contents of the drum, the skirt is separated from the cap by a prying action or by a severing step so as to break enough of the frangible elements so as to have access to the lower edge of the cap. The cap is then able to be pried off and the plug  39  can then be unscrewed and removed from the internally threaded aperture. Manual removal by prying is likely the easiest and safest removal technique and requires only a simple prying implement, such as a screwdriver. Alternatively, the cap can be pulled off with pliers or cut or severed in some fashion to free it from the plug. Cutting or severing are felt to be less desirable approaches. 
     With reference to FIGS. 7,  8 ,  9 , and  10 , another embodiment of the present invention is illustrated. This second embodiment is directed to a unitary, molded plastic overcap  70  which includes a cap  71  and a removable skirt  72  which is connected to cap  71  by a plurality of frangible elements  73 . In the illustrated embodiment there are a total of eighteen frangible elements which are equally spaced apart with centerline-to-centerline intervals each measuring approximately 20 degrees. 
     Cap  71  has a closed, generally circular and substantially flat top  74  and a generally cylindrical sidewall  75 . The top  74  and sidewall  75  are joined (unitary construction) at circumferential edge  76 . The lower end  77  of sidewall  75  includes an inwardly directed continuous annular lip  78  which constitutes a hook bead for the snap-fit of overcap  70  onto a formed peripheral edge of a flange fitting  82  (see FIG.  11 ). The frangible elements  73  are generally positioned adjacent to circumferential edge  76  where the top  74  and sidewall  75  meet. The precise location is slightly below the uppermost surface of edge  76  and a little closer to the upper end of sidewall  75 . The frangible elements  73  connect this portion of cap  71  to the inside surface  72   a  of the uppermost portion of skirt  72 . 
     The flange fitting  82  has an octagonally-shaped flange  83  and a substantially cylindrical, sleeve-like sidewall  84  which defines an internally-threaded, annular aperture  85  which receives an annular metal closing plug  86 . The fitting  82  is designed to fit within a drawn pocket  87  in the drum end and this drawn pocket captures the octagonally-shaped flange  83  and permits the sidewall  84  to axially extend above a drawn pocket annular sidewall  88 . The upper lip  89  of the sidewall  84  is rolled over the top edge  90  of the drawn pocket sidewall  88  as a way of axially anchoring the flange fitting in position (see FIG.  11 ). Plug  86  has a closed base  86 (a )and an externally-threaded sidewall  86   b  for threaded engagement with aperture  85  so as to close the opening in the drum end which is defined by aperture  85 . The free end  91  of the upper lip  89  is used as the edge for snap-fit cooperation with annular lip  78  (i.e., the hook bead). An annular gasket  95  is positioned around the plug body (i.e., sidewall  86   b ) directly beneath outwardly-radiating annular lip  96 . As the plug  86  is threadedly advanced into aperture  85 , the lip  96  draws the gasket  95  into sealing engagement against the uppermost thread of aperture  85  of flange fitting  82 . As gasket compression occurs, the gasket  95  is pushed into engagement with the inner surface of sidewall  84  at a location adjacent upper lip  89  as is begins to bend in order to extend of the top edge  90 . 
     In the final assembly of flange fitting  82 , plug  86  and overcap  70 , as illustrated in FIG. 11, it will be seen that the lip  78  of cap sidewall  75  is snapped over and around the free end  91  of the upper lip  89 . At the same time, the underside surface  97  of the removable skirt  72  is positioned directly above the upper surface  98  of drawn pocket  87 . This pocket  87  which is formed by drawing the metal of the drum end into an octagonally-shaped pocket has a substantially flat upper surface  98  which extends completely around the sidewall  88  of pocket  87 . Since there is only a very slight clearance (0.010-0.020 inches)(0.25-0.51 mm) between surface  98  and surface  97 , there is not sufficient space for any type of tool, implement, or utensil to be inserted therein in order to pry off cap  71  without at least one of the frangible elements  73  being broken. If even one frangible element is broken, this would indicate that some type of tampering effort may have been attempted. The axial offset between the lower surfaces of the sidewall  75  and the skirt  72  as well as their radial separation make it virtually impossible to insert any type of tool, implement, or utensil into the slight clearance space and then lift up on the skirt in order to try and reach the lip  78  of the cap without at least one of the frangible elements  73  breaking. Consequently, the overcap  70  provides a unique and very effective tamper-evident structure for use with flange fittings and drum assemblies of the type and style illustrated herein. As illustrated in FIG. 11, the cap  71  snaps onto the upper lip  89  of fitting  82  and is free of any direct connection to the container, represented in part by drawn pocket  87 . The outer skirt  72  is also free of any direct connection to the container. 
     There is always some risk that through careless handling or other inadvertent activities, one or more of the frangible elements will be broken and thereby send a false signal of a tampering attempt. However, the minimal distance of separation between the cap and the skirt, in both of the illustrated embodiments, and the limited clearance space or line-to-line fit of the lower edge of the skirt against the upper surface of the drum end strongly suggests that breakage of any frangible elements through an inadvertent act is highly unlikely. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.