Abstract:
The plastic cover is easily removed from a metal container to allow the plastic cover and the metal container to be separately recycled. The lip that holds the plastic cover to the metal container has two or more circumferential ends which have a lower degree of engagement than the remaining portion of the lip. A press point on the cover which transforms the circular cover into an elliptical shape is positioned on the outside of the cover opposite the circumferential ends and a shoulder is mounted inside the cover opposite the press point. The shoulder bears against the container to assist in removal of the cover. Where the cover has both an inner cylinder and an outer cylinder, a rib is employed to connect the inner cylinder of the cover to the outer cylinder of the cover and to transfer pressure from the press point to the inner cylinder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a plastic cover for a metal container and, more particularly, to a plastic cover which is removable from the metal container to allow the plastic cover and the metal container to be separately recycled. The cover is especially suited for aerosol cans. 
     2. Prior Art 
     A typical aerosol can has a plastic cover which is attached at the upper face of a metal container. The container holds its contents under pressure and the cover has a nozzle which allows the user to release the contents from the container. The cover is usually firmly attached to the container by the interaction between a lip on the cover and a top lip or curl of the container. Because of the tight lock between the lip of the cover and the curl of the container, the two are recycled together, rather than separately. Because the container and cover are made of different materials, there is a need to separate the two for efficient recycling. 
     One suggestion for making the cover easily removable from the container is suggested in Japanese Patent Application No. 9-52584. The teachings of the &#39;584 application are illustrated in FIGS.  6 A- 6 C. As shown in FIGS. 6A-6C, cover  7  is attached to container  8 . Cover  7  has nozzle  71  and inner cylinder  72  with an opening or discontinuous portion  72 ′. Attached to inner cylinder  72  is lip  73 , which is shown as two sections. Each section has two circumferential ends  74  and a side portion  74 ′. Lip  73  is uniform in dimensions throughout, i.e. from circumferential end to circumferential end. Outer cylinder  75  has press point  76  which is used to deform cover  7  into an elliptical shape as shown in FIG.  6 C. When cover  7  is deformed into this elliptical shape, cover  7  can be removed from container  8 . Conventionally, cover  7  is molded from a plastic material into one piece and container  8  is made of metal. 
     Metal container  8  has a sloping wall section  81 , curl  82  and stem  83 . Stem  83  along with the other structure, not shown, allows for the contents of container  8  to be jetted out of container  8 . Curl  82  interacts with lip  73  to hold cover  7  onto container  8  in a conventional way. Stem  83  fits through nozzle  71  as shown in FIG.  6 A. 
     To assemble cover  7  on container  8 , cover  7  is pushed down onto container  8  and lip  73  forces inner cylinder  72  to flex outward while lip  73  rides over curl  82 . Lip  73  then locks into the concave portion under curl  82  and holds cover  7  onto container  8 . 
     To remove cover  7  from container  8 , the user pushes on press point  76  to force cover  7  into an elliptical shape as shown in FIG. 6C. A gap forms between curl  82  and side portion  74 ′ of lip  74  and cover  7  can be removed from container  8 . 
     Although the arrangement in FIGS. 6A-6C allows cover  7  to be removed from container  8 , there is a need to improve this arrangement and make it easier to separate the two components, cover  7  and container  8 . 
     SUMMARY OF THE INVENTION 
     A plastic cover which is easily removed from a metal container has now been discovered. The cover of the present invention is easily removed from the container because it employs a curl engaging member which has at least two circumferential ends, wherein the circumferential ends have a degree of engagement with the curl that is less than the degree of engagement between the curl and a side portion of the curl engaging member. 
     The curl engaging member can be a lip that holds the cover to the container by residing in the concave portion below the curl of the container, or a concave portion in which the curl of the container resides when the cover and the container are joined together. Preferably, the curl engaging member is a lip. 
     The cover of the present invention is either a cover having two concentric cylinders, an inner cylinder and an outer cylinder, or is a cover with a single outer cylinder. In either case, the curl engaging member is affixed inside the cover and engages the curl to hold the cover onto the container during normal operation. 
     In order to remove the cover from the container in accordance with the present invention, the cover has a press point that is pushed by the user to cause the cover to form an elliptical shape. The press point is positioned on the outside of the cover. 
     The curl engaging member is not a circle but is discontinuous, such that it has at least two circumferential ends. Preferably, the curl engaging member has two circumferential ends. These circumferential ends define one or more openings in the curl engaging member. At least one of the openings is positioned opposite the press point. 
     When the press point is pressed and the cover forms an elliptical shape, the side portion of the curl engaging member becomes disengaged from the curl and the circumferential ends are designed to slide easily over the curl because they have a low degree of engagement with the curl. The side portion of the curl engaging member is generally that portion of the curl engaging member that extends from one circumferential end to the other circumferential end. In the case where there are only two circumferential ends and the curl engaging member takes on the shape of the letter “C”, then the side portions of the curl engaging member correspond to the top and bottom of the “C”. The back portion of the curl engaging member is that portion which corresponds to the back of the “C” and directly opposite the opening of the “C”. In the case where there are four circumferential ends, the back of the curl engaging member is absent. As mentioned above, the front of the “C” faces the press point in the cover. 
     The side portion of the curl engaging member has a higher degree of engagement with the curl of the container than the circumferential ends and accounts for the majority of the curl engaging member. 
     There are a number of ways in which to make the circumferential ends of the curl engaging member have a degree of engagement with the curl that is less than the side portion degree of engagement with the curl. The ways to make the degree of engagement less include: (1) the circumferential ends of the curl engaging member have a radius of curvature that is greater than the radius of curvature of their side portion; or (2) the elasticity (stiffness) of the circumferential ends is lower than the side portion of the curl engaging member; or (3) the frictional coefficient between the circumferential ends and the curl is less than the coefficient of friction between the curl and the side portion of the curl engaging member. 
     Preferably, the radius of curvature of the circumferential ends of the curl engaging member is greater than the radius of curvature of the side portion. When the curl engaging member is a lip, the top of the circumferential end has a radius of curvature which is greater than the radius of curvature of the top of the side portion of the lip. When the curl engaging member is a concave portion in which the curl resides, the bottom of the circumferential ends have a radius of curvature that is more than the radius of curvature of the bottom of the side portion of the concave portion. 
     Preferably, a shoulder is formed on the inside of the cover at a point which is opposite the opening formed by the circumferential ends. Preferably, the shoulder is positioned directly opposite the press point. The shoulder contacts the sloping wall section of the container when the user pushes the press point. As the user presses the press point, the shoulder contacts the upwardly sloping wall of the metal container and causes the cover to rise upwardly in response to the pressing of the user. This guides the cover up and off of the container. 
     Usually there is a space between the end of the cylindrical portion that the shoulder is formed on and the container. This means that there is a short lag time between when the pressure is applied to the press point and the time that pressure is exerted by the shoulder on the sloping side wall of the container. 
     In the case where the cover is of the type having two concentric cylinders, an inner and an outer, the curl engaging member is formed on the inside of the inner cylinder and the inner cylinder has an opening which corresponds to the opening defined by the circumferential ends of the curl engaging member. In such an arrangement, it is preferred that a rib be employed which connects the outer cylinder with the inner cylinder in order to transfer the pressure from the press point directly to the inner cylinder. Preferably, the rib is connected to the inner cylinder at the point where the inner cylinder ends and the opening begins. This is also preferably the location of the circumferential ends. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects of the present invention may be more fully understood by reference to one or more of the following drawings wherein: 
     FIG. 1A illustrates a sectional view of the cover of the present invention with both inner and outer cylinders; 
     FIG. 1B illustrates a bottom view of the cover of FIG. 1A; 
     FIG. 1C illustrates the radius of curvature of the circumferential end of the lip; 
     FIG. 1D illustrates the radius of curvature of the middle portion of the lip; 
     FIGS. 2A and 2B illustrate the start of disengagement between the cover and the container; 
     FIGS. 3A and 3B illustrate a later stage of the disengagement between the cover and the container than that which is shown in FIGS. 2A and 2B; 
     FIGS. 4A and 4B illustrate another form of a cover made in accordance with the present invention and employing an inner and an outer cylinder; 
     FIGS. 5A,  5 B and  5 C illustrate a cover of the present invention having a single cylinder; 
     FIGS. 6A,  6 B and  6 C illustrate a prior art releasable cover and how that cover is removed from the container; 
     FIGS. 7A and 7B illustrate an alternate embodiment of the cover of FIGS. 1A and 1B; and 
     FIGS. 8A and 8B illustrate an alternate embodiment of the cover of FIGS.  5 A and  5 B. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1A, plastic cover  1  has outer cylinder  2  and inner cylinder  3 . Cover  1  can comprise a spout  4  (see FIG.  4 A). FIG. 5 illustrates plastic cover  5  made in accordance with the present invention but employing single cylinder wall  6 . Both covers  1  and  5  are mounted on metal container  8 . 
     Returning to FIG. 1A, opening  11  in cover  1  is used for a nozzle, stem and push button (not shown). Inside outer cylinder  2  is shoulder  21  and outside outer cylinder  2  is press point  22 . Inner cylinder  3  has lip  31  (curl engaging member) which has circumferential ends  32  and side portion  34 . Top portion  33  of circumferential ends  32  and top portion  35  of side portion  34  are the top edge of lip  31  at these two points and are used to define the radius of curvature in FIGS. 1C and 1D. Opening  36  illustrates the absence of lip  31  and the absence of inner cylinder  3 . Back portion  37  of lip  31  is opposite to opening  36 . Rib  38  connects inner cylinder  3  and circumferential ends  32  to outer cylinder  2 . Imaginary line  39  is a boundary portion between circumferential ends  32  and side portion  34 . As shown in FIGS. 1C and 1D, radius of curvature  33 R is for top portion  33  of circumferential ends  32  while radius of curvature  35 R is for top portion  35  of side portion  34 . Radius of curvature  33 R is greater than radius of curvature  35 R. Central angle  36 A defines opening  36 . 
     The degree of engagement of circumferential ends  33  is less than the degree of engagement of side portion  34  because radius of curvature  33 R is greater than radius of curvature  35 R. 
     As shown in FIG. 4A, passage  41  is used for removing the contents of container  8 . Push portion  42  is connected to cover  1  by connection portion  43 . 
     As shown in FIG. 5A, plastic cover  5  comprises a single cylinder wall  6  with opening  51  for operation. Cylinder wall  6  has lip  61  which comprises circumferential ends  62  and side portion  64 . Top portion  63  of the circumferential ends  62  and top portion  65  of the side portion  64  make up the top of lip  61 . Opening  66  has no lip  61  therein. Shoulder  67  is opposite press point  68  which is pressed when the plastic cover is removed from the metal container. Opening  69  is used for jetting contents from container  8 . Radius of curvature  63 R of top portion  63  and radius of curvature  65 R of top portion  65  are illustrated. Radius of curvature  63 R is greater than radius of curvature  65 R. Central angle  66 A measures opening  66 . 
     The degree of engagement of circumferential ends  63  is less than the degree of engagement of side portion  64  because radius of curvature  63 R is greater than radius of curvature  65 R. 
     Plastic cover  1  and  5  are made of plastics such as polypropylene, polyethylene and so on. Metal container  8  is conventionally made of aluminum or tin and so on. 
     The cross section of outer cylinder  2  and single cylinder  6  is a circle in shape. The cross section of inner cylinder  3  and lip  31  and  61  is a “C” in shape because of the opening  36  and  66 . Inner cylinder  3  may be formed without opening  36 , however, it is preferred to have opening  36 . 
     Opening  36  and  66  corresponds to the position of shoulder  21  and  67  and to the position of press point  22  and  68  of outer cylinder  2  and the single cylinder wall  6 , respectively. Central angle  36 A and  66 A of opening  36  and  66  are about 50° to about 100°. Radius of curvature  33 R and  63 R of top portion  33  and  63  of circumferential ends  32  and  62  are, for example, 1 mm. Radius of curvature  35 R and  65 R of top portion  35  and  65  of side portion  34  and  64  are, for example, 0.5 mm. 
     As illustrated in FIGS. 1 and 4, plastic cover  1  which is comprised of the double cylinders  2  and  3  and metal container  8  are combined by engaging lip  31  of inner cylinder  3  with curl  81  of metal container  8 . 
     Shoulder  21  is formed on the inner face of outer cylinder  2  and corresponds to opening  36  of lip  31  while shoulder  67  is formed on the inner face of single cylinder wall  6 . The lower end of shoulders  21  and  67  nearly contact sloping side wall  81  of metal container  8  when plastic cover  1  and  5  engage with metal container  8 . 
     When a user pushes a push button (not shown) which is employed in opening  11  in FIG. 1 or push portion  42  in FIG. 4, the contents of container  8  are jetted out from container  8 . Here, in the case of FIG. 4, spout  4  tilts clockwise on the connection portion  43  when a user pushes portion  42 . 
     After the contents are used up, plastic cover  1  is easily removed from metal container  8  by pressing press point  22  in the direction of the arrows shown in FIGS. 1A and 1B. 
     Plastic cover  1  is easily removed from container  8  because: (1) radius of curvature  33 R of top portion  33  of circumferential ends  32  is greater than radius of curvature  35 R of top portion  35  of side portion  34 ; (2) shoulder  21  contacts sloping side wall  81  of metal container  8  when press point  22  is pressed; and (3) circumferential ends  32  of inner cylinder  3  are connected to press point  22  of outer cylinder  2  by rib  38 . 
     When press point  22  of outer cylinder  2  is pressed, the following happens: the press force acts on circumferential ends  32  of lip  31  of inner cylinder  3  directly; outer cylinder  2 , inner cylinder  3  and lip  31  are transformed into elliptical shape, side portion  34  of lip  31  is extended outward, compared to the state before press operation; at least shoulder  21  on the reverse side of press point  22  is moved inward and receives an upward force from sloping side wall  81 . 
     Circumferential ends  32  of lip  31  are easy to lift up because they receive the force from sloping side wall  81  and because radius of curvature  33 R of top portion  33  is configured to be greater than radius of curvature  35 R. 
     As a result, the whole lip  31  slides over curl  82  in cooperation with the above mentioned elliptical transformation, and plastic cover  1  is removed from metal container  8 . 
     Even in the case that the degree of the elliptical transformation is low, lip  31  slides over curl  82  because the degree of engagement between the circumferential ends of the lip is less than the degree of engagement of the side portion of the lip. 
     The upward force that moves cover  1  off of container  8  is made up of: the force which is received by the press operation directly; and the force which is received from sloping side wall  81  through shoulders  21  and  67 . 
     FIG. 2 shows the early stage of press operation for removing cover  1  from container  8 . In this operation, circumferential ends  32  of lip  31  moves in the direction of arrow C, however, they are still engaged with curl  82  of metal container  8 ; side portion  34  of lip  31  extends outward from curl  82 ; and back portion  37  of lip  31  which is opposite to opening  36  is still engaged with curl  82 . 
     FIG. 3 shows the final stage of the pressing operation. Circumferential ends  32  of lip  31  slides over curl  82  of metal container  8 ; side portion  34  of lip  31  comes off curl  82 ; and back portion  37  of lip  31  which is opposite to opening  36  slips off curl  82 . 
     Plastic cover  5  which has single cylinder wall  6 , is combined with metal container  8  by engagement between lip  61  of single cylinder wall  6  and curl  82  of metal container  8 . 
     When a user pushes the push button associated with the nozzle (not shown) which is employed in the inner side of the single cylinder  6 , the contents of container  8  are jetted outside from metal container  8  through the nozzle in opening  69 . 
     After the contents are used up, plastic cover  5  is removed from metal container  8  by pressing press point  68  of single cylinder portion  6  in the direction of an arrow shown in FIG.  5 C. 
     When the transformation into an elliptical shape of plastic cover  5  is small, lip  61  receives the above-mentioned upward force, and is lifted from circumferential ends  62  which has a lower degree of engagement with metal container  8  than side portion  64 . 
     According to the present invention, the plastic cover is easily removed from the metal container because the circumferential ends of the lip, which is formed in the cylindrical portion of the plastic cover (the inner cylinder of the double cylinder or the single cylinder), have a lower degree of engagement with the curl of the metal container than the side portion of the lip. 
     Also, since a shoulder is formed in the part which corresponds to the opening in the lip and contacts the sloping wall section of the metal container at almost the same time when the corresponding portion is pressed inward, a direction of pushing up, the plastic cover is moved upward guided by the sloping wall section of the metal container. 
     Additionally, since the circumferential ends of the lip and the outer cylinder are connected by a rib so as to transfer pressing force from the outer cylinder to the inner cylinder, the degree to which the lip is transformed to an elliptical shape is high. This means that the side portion which follows the circumferential ends is easily released from the metal container. 
     It will be appreciated that modifications may be made in the present invention. For example, the width of the lip in the direction of diameter can be varied such that the width of the lip at the circumferential ends is less than the width of the lip at the side portions. The friction coefficient and the degree of elasticity (stiffness) of the circumferential ends can be lower than the side portion of the lip. 
     The plastic cover may be moved upward by the pushing up operation of the user without the upward action from the sloping wall section of the metal container. 
     Also, instead of the lip formed in the plastic cover, the curl engaging member can be a concave portion which is formed in the plastic cover such that the curl of the container resides in the concave portion of the cover when the cover is on the container. 
     Additionally, the nozzle and the like need not be employed in the plastic cover. 
     Furthermore, the shoulder may be formed in any place which can receive upward force from sloping sidewall of the metal container when the press point is pressed. 
     Further, the lip may be formed dividedly, provided it employ the circumferential ends, e.g. the present invention may be used in the arrangement shown in FIGS. 7A-7B and  8 A- 8 B, wherein there are four circumferential ends  32 ,  32 ′,  62 ,  62 ′, and two openings  36 ,  36 ′,  66 ,  66 ′. 
     It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention herein chosen for the purpose of illustration which do not constitute a departure from the spirit and scope of the invention.