Method of making an easy opening container wall

Claim 1

A method of fabricating an easy-opening container of the character described wherein a sheet metal wall of the container is scored to form a tear strip and a tab is attached to the tear strip by a hollow rivet formed in the tear strip, said method being characterized by the steps of: squeezing the sheet metal wall around the base of the rivet to reduce the thickness of the wall and to form a zone in which the outer face of the wall is depressed to lower level and to form two ramps on the opposite sides of the zone leading to the lower level; placing one face of the sheet metal wall against a first die having a plateau conforming to said zone and having an extensive planar working face at the base of the plateau, the plateau having slopes conforming to the two ramps respectively of lesser inclination than the ramps, each slope leading from the top of the plateau to said working face; positioning a second die against the other face of the sheet metal wall, the second die having a protruding scoring element to score the wall of the container to form the tear strip, said scoring element having a leading face in a plane substantially parallel to said working face, said scoring element being of a configuration to loop around the hollow rivet in the region of said zone with two spaced portions of the scoring element positioned to extend from the region of the plateau across the regions of the two slopes respectively to the region of said working face; and causing relative movement of said dies to force said scoring element into the sheet metal of the can top with consequent resilient deflection of the sheet metal against the two slopes and the working face of the first die to cause the scoring element to form a relatively thin residual web in said zone with the residual web progressively increasing in thickness along the two ramps from said zone to the region outside of the zone.

Claim 2

A method of fabricating an easy-opening container of the character described wherein a sheet metal wall of the container is scored to form a tear strip and a tab is attached to the tear strip by a hollow rivet formed in the tear strip, said method being characterized by the steps of: squeezing the sheet metal wall around the base of the rivet to reduce the thickness of the wall and to form a zone in which the outer face of the wall is depressed to lower level and to form two ramps on the opposite sides of the zone leading to the lower level; placing one face of the sheet metal wall against a first die having a plateau conforming to said zone and having an extensive planar working face at the base of the plateau, the plateau having slopes conforming to the two ramps respectively of lesser inclination than the ramps, each slope leading from the top of the plateau to said working face; positioning a second die against the other face of the sheet metal wall, the second die having a protruding scoring element to score the wall of the container to form the tear strip, said scoring element having a leading face in a plane substantially parallel to said working face, said scoring element being of a configuration to loop around the hollow rivet in the region of said zone with two spaced portions of the scoring element positioned to extend from the region of the plateau across the regions of the two slopes respectively to the region of said working face; and causing relative movement of said dies to force said scoring element into the sheet metal of the can top with consequent resilient deflection of the sheet metal against the two slopes and the working face of the first die to cause the scoring element to form a relatively thin residual web in said zone with the residual web progressively increasing in thickness along the two ramps from said zone to the region outside of the zone.

Claim 3

A method of forming a hollow rivet in a container wall of sheet material comprising: forming a hollow rivet of sheet material integral with the container wall; said step of forming including squeezing a zone of sheet material surrounding the rivet to displace some of the material from said zone into the rivet and to displace other portions of the material from said zone radially outwardly; and offsetting the sheet material simultaneously with said step of squeezing at a region radially outwardly of said zone to take up at least some of said other portions of the material.

Claim 4

A method of forming a hollow rivet in a container wall of sheet material comprising: forming a hollow rivet of sheet material integral with the container wall; said step of forming including squeezing a zone of sheet material surrounding the rivet to displace some of the material from said zone into the rivet and to displace other portions of the material from said zone radially outwardly; and offsetting the sheet material simultaneously with said step of squeezing at a region radially outwardly of said zone to take up at least some of said other portions of the material.

Claim 5

A method of forming a tear portion in a container wall of sheet material comprising: offsetting regions of the container wall to form first and second ribs extending in the same general direction and having a section of the container wall therebetween with said step of offsetting placing said section in tension; substantially confining the sheet material of said section against relative movement in a direction generally transverse to the plane of said section and providing free space adjacent the ribs to allow enlargement of the dimensions therEof; and scoring said section along a predetermined line subsequent to the offsetting operation to form the tear portion with sheet material being displaced laterally of said predetermined line by the scoring operation to at least partially relieve said tension in said section, the free space adjacent the ribs allowing for enlargement of the dimensions of said ribs as a result of the displacement of sheet material during the scoring operation.

Claim 6

A method of forming a tear portion in a container wall of sheet material comprising: offsetting regions of the container wall to form first and second ribs extending in the same general direction and having a section of the container wall therebetween with said step of offsetting placing said section in tension; substantially confining the sheet material of said section against relative movement in a direction generally transverse to the plane of said section and providing free space adjacent the ribs to allow enlargement of the dimensions therEof; and scoring said section along a predetermined line subsequent to the offsetting operation to form the tear portion with sheet material being displaced laterally of said predetermined line by the scoring operation to at least partially relieve said tension in said section, the free space adjacent the ribs allowing for enlargement of the dimensions of said ribs as a result of the displacement of sheet material during the scoring operation.

Claim 7

A method of fabricating an easy-opening can top of sheet material comprising: forming a hollow rivet in the sheet material by an operation that spreads the sheet material; offsetting the sheet material simultaneously with the rivet-forming operation to form two ribs on opposite sides respectively of the rivet to take up the sheet material as the sheet material is displaced by the rivet-forming operation and to place a section of the sheet material between the ribs in tension; and scoring the sheet material including said section of sheet material to form a tear strip and at least partially relieve said tension in said section of sheet material, said step of scoring being carried out subsequent to the rivet-forming operation, the two ribs straddling the tear strip and extending longitudinally thereof.

Claim 8

A method of fabricating an easy-opening can top of sheet material comprising: forming a hollow rivet in the sheet material by an operation that spreads the sheet material; offsetting the sheet material simultaneously with the rivet-forming operation to form two ribs on opposite sides respectively of the rivet to take up the sheet material as the sheet material is displaced by the rivet-forming operation and to place a section of the sheet material between the ribs in tension; and scoring the sheet material including said section of sheet material to form a tear strip and at least partially relieve said tension in said section of sheet material, said step of scoring being carried out subsequent to the rivet-forming operation, the two ribs straddling the tear strip and extending longitudinally thereof.

Claim 9

A method of fabricating an easy-opening can top of sheet material comprising: providing a can top of sheet material having a peripheral flange defining a head space with the can top bowing outwardly into the head space and with the maximum outward bowing being at the center of the can top; forming a hollow rivet in the can top at a location spaced radially from the center of the can top to avoid locating the rivet in the region of maximum outward bowing of the can top, said rivet being adapted to attach a second class lever to the can top; offsetting the sheet material simultaneously with the rivet-forming operation to form two ribs on opposite sides respectively of the rivet to take up the sheet material as the sheet material is displaced by the rivet-forming operation and to place a section of the sheet material between said ribs in tension; and scoring the sheet material including said section of sheet material to form a tear strip and at least partially relieve said tension in said section of sheet material, said step of scoring being carried out subsequent to the rivet-forming operation, the two ribs straddling the tear strip and extending longitudinally thereof, the two ribs being at locations to receive the fulcrum force of the lever and to stiffen the can top against flexure by the fulcrum force.

Claim 10

A method of fabricating an easy-opening can top of sheet material comprising: providing a can top of sheet material having a peripheral flange defining a head space with the can top bowing outwardly into the head space and with the maximum outward bowing being at the center of the can top; forming a hollow rivet in the can top at a location spaced radially from the center of the can top to avoid locating the rivet in the region of maximum outward bowing of the can top, said rivet being adapted to attach a second class lever to the can top; offsetting the sheet material simultaneously with the rivet-forming operation to form two ribs on opposite sides respectively of the rivet to take up the sheet material as the sheet material is displaced by the rivet-forming operation and to place a section of the sheet material between said ribs in tension; and scoring the sheet material including said section of sheet material to form a tear strip and at least partially relieve said tension in said section of sheet material, said step of scoring being carried out subsequent to the rivet-forming operation, the two ribs straddling the tear strip and extending longitudinally thereof, the two ribs being at locations to receive the fulcrum force of the lever and to stiffen the can top against flexure by the fulcrum force.

Claim 11

A method of forming an easy-opening container wall of sheet material comprising: forming a hollow rivet in the sheet material by an operation that spreads some of the sheet material outwardly of the rivet; offsetting the sheet material simultaneously with the rivet-forming operation to form at least two ribs and to take up at least some of the material displaced in the rivet-forming operation, the formation of said ribs placing at least a section of the sheet material in tension; scoring the sheet material along a predetermined line to form a tear portion of the desired configuration with the scoring operation displacing material generally laterally outwardly from the predetermined line to thereby at least partially relieve said tension, at least portions of said predetermined line being adjacent said ribs; and further offsetting said ribs to enlarge said ribs simultaneously with the scoring operation.

Claim 12

A method of forming an easy-opening container wall of sheet material comprising: forming a hollow rivet in the sheet material by an operation that spreads some of the sheet material outwardly of the rivet; offsetting the sheet material simultaneously with the rivet-forming operation to form at least two ribs and to take up at least some of the material displaced in the rivet-forming operation, the formation of said ribs placing at least a section of the sheet material in tension; scoring the sheet material along a predetermined line to form a tear portion of the desired configuration with the scoring operation displacing material generally laterally outwardly from the predetermined line to thereby at least partially relieve said tension, at least portions of said predetermined line being adjacent said ribs; and further offsetting said ribs to enlarge said ribs simultaneously with the scoring operation.