Patent Publication Number: US-3967754-A

Title: Pull tab anti-rotation mounting

Description:
SUMMARY OF THE INVENTION 
     When easy-open containers employing integral off-center rivets are subjected to excessive internal pressure, as may occur when the closed container is heated, the end closure bulges outwardly and exerts an upward force on the tab, causing the tab to protrude from the end panel. This protruding tab may be jostled during handling of the can, resulting in either misalignment of the tab and concommitant malfunctioning during opening or unintentional opening of the container. 
     It is therefore the primary object of this invention to provide an improved easy-open end closure wherein the tab will consistently resist rotational displacement during handling. 
     It is a further object of this invention to provide an easy-open end closure wherein the tab will maintain close contact with the end panel despite excessive internal pressurization of the container. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of the end closure of the present invention. 
     FIG. 2 is a fragmentary sectional view of the present invention taken substantially along line 2--2 of FIG. 1. 
     FIG. 3 is an enlarged fragmentary view of the rivet panel shown in FIG. 2. 
     FIG. 4 is a fragmentary sectional view of a conventional end closure, wherein the end panel has bulged due to internal pressure. 
     FIG. 5 is a fragmentary sectional view similar to FIG. 2, wherein the end panel has bulged due to internal pressure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As best shown in FIG. 1, the easy-open end closure of this invention comprises an end panel 1 with integral off-center rivet 2, including a head 2a and a shank 2b. A pull tab 3 is rotatably attached to the end panel 1 by the rivet 2 and a score line 4 is formed in the end panel 1 and defines an opening flap 5 therein. 
     The tab 3 comprises a nose portion 3a, an intermediate portion 3b, and a finger ring portion 3c. The intermediate portion 3b includes a rivet panel 6 inclined substantially 5° relative to the principal plane of the tab 3. Two panelwardly-directed legs 11 are formed in the finger ring portion 3c of the tab 3. 
     A recess 8 having a sidewall 8a and a base 8b is formed in the end panel 1. The sidewall 8a forms obtuse angles with the end panel 1 and the base 8b which is parallel to the panel 1. 
     The finger ring portion 3c of the tab 3 rests partially within the recess 8 supported on the legs 11, with the outer periphery of said portion 3c abutting the recess sidewall 8a. 
     During the staking operation, wherein the tab 3 is attached to the end panel 1, the tab 3 is sprung slightly, as the rivet panel 6 is forced flat against the end panel 1, producing a panelward bias on the finger ring portion 3c which forces the legs 11 against the base 8b of the recess 8. 
     A protrusion 10, comprising a sloped sidewall 8a and flat horizontal top 8b, is formed in the base 8b of the recess structure 8 proximate to the end panel center and in line with the legs 11 on the tab 3. The protrusion sidewall 10a abuts the inner periphery of the finger ring portion 3c. The top 8b extends beyond the plane of the end panel 1. 
     When a conventional end closure is subjected to excessive internal pressure, as may occur if the container contents are heated after the container has been sealed, the end panel 1 bulges, causing protrusion of the tab 3 (FIG. 4). The protruding tab 3 may thereupon be subject to undesired rotational displacement resulting from accidental contact with container handling equipment. 
     In the improved end closure of the present invention, the recess sidewall 8a and the protrusion 10 serve an anti-rotation abuttments, restraining rotational displacement of the tab 3. The protrusion 10, being located proximately at the end panel 1 center, is at the point of greatest distortion during end panel 1 bulging. The protrusion 10 is displaced outwardly during bulging of the end panel 1, thereby preventing disengagement from the tab 3 resulting from upward rotation of the tab 3 about a point of contact 11 with the bulged end panel 1. The panelward bias of the tab 3 serves to reduce this rotation and aids preventing disengagement. Further, the panelwardly-extending legs 11 maintain engagement with the protrusion sidewall 10b despite minor vertical displacement of the finger ring portion 3c.