Double action bottom former for high cyclic operation

An improved double action bottom former capable of high cyclic operation to form and shape metal can blanks, said double action bottom former comprising:

• an integral cylinder housing member having a first end portion and a second end portion separated apart by an integral chamber separator, said first end portion having sidewalls defining a first axial chamber having a cylindrical shape and of a known diameter, said second end portion having sidewalls defining a second axial chamber having a cylindrical shape and of a known diameter generally greater than the known diameter of said first axial chamber, said sidewalls of said first end portion comprising a plurality of axially oriented bores extending the length of said first end portion of said integral cylinder housing member and through said integral chamber separator into said second axial chamber;
• tool set means located within said first end portion of said integral cylinder housing member comprising a dome plug and a clamp ring located circumferentially about said dome plug to engage and form a metal can blank;
• pushrod means comprising a plurality of pushrods slidably positioned within a corresponding number of pushrod bushings fixedly fitted within said axially oriented bores of said first end portion of said integral cylinder housing member, each of said pushrods comprising a first end in abutting engagement with a bottom portion of said clamp ring and a second end located in proximity of said integral chamber separator;
• piston means for providing suspension for said pushrod means, said piston means comprising a piston member movably positioned within said second axial chamber, said piston member comprising a concave-shaped bottom having a concave receiving surface generally facing said integral chamber separator and an annular piston wall attached to the periphery of said concave-shaped bottom to form a centralized cavity, said annular piston wall comprising a contact surface geometrically configured to engage said second end of each pushrod extending into said second axial chamber, said concave receiving surface being substantially opposite of said contact surface for receiving a pressurized medium to resiliently position said pushrods and clamp ring as the metal can blank engages said clamp ring to produce a corresponding force against said pushrods and cause axial transfer thereof to said piston member;
• biasing means for resilient positioning of said dome plug, said biasing means comprising a donut spring having an interior cylindrical space defining a third axial chamber and being further defined in part by a cover plate, said cover plate having a large aperture extending therethrough and in axial alignment with said integral cylinder housing member to provide hydraulic communication between second and third axial chambers, said cover plate and donut spring cooperating with one another for effective biasing of said integral cylinder housing member in the direction of said first end portion of said integral cylinder housing member;
• and
• gas access means for conveying a pressurized medium from an external source to said second and third axial chambers to generate and provide a corresponding force to act on and against said concave receiving surface of piston member for resilient positioning of said pushrods and clamp ring.

A method of absorbing the mechanical impact resulting from a press arm having a metal can blank fitted thereto and substantially contacting and engaging components comprising an improved double action bottom former to shape and form a desired profile of a can bottom, said method comprising the steps of:

• providing an integral cylinder housing member having a first end portion and a second end portion separated apart by an integral chamber separator, said first end portion having sidewalls defining a first axial chamber having a cylindrical shape and of a known diameter, said second end portion having sidewalls defining a second axial chamber having a cylindrical shape and of a known diameter generally greater than the known diameter of said first axial chamber, said sidewalls of said first end portion comprising a plurality of axially oriented bores extending the length of said first end portion of said integral cylinder housing member and through said integral chamber separator into said second axial chamber;
• mounting tool set means at said first end portion of said integral cylinder housing member comprising a dome plug and a clamp ring located circumferentially about said dome plug to engage and form a metal can blank, said clamp ring being fastened to said integral cylinder housing member by a clamp ring retainer held in position by a lock nut threadly engaged with said sidewalls of said first end portion of said integral cylinder housing member;
• fitting a plurality of pushrods within a corresponding number of pushrod bushings fixedly fitted within said axially oriented bores of said first end portion of said integral cylinder housing member, each of said pushrods comprising a first end in abutting engagement with a bottom portion of said clamp ring and a second end located in proximity of said integral chamber separator;
• supplying piston means to provide suspension for said pushrod means, said piston means comprising a piston member movably positioned within said second axial chamber, said piston member comprising a concave-shaped bottom having a concave receiving surface generally facing said integral chamber separator and an annular piston wall attached to the periphery of said concave-shaped bottom to form a centralized cavity, said annular piston wall comprising a contact surface geometrically configured to engage said second end of each pushrod extending into said second axial chamber, said concave receiving surface being substantially opposite of said contact surface for receiving a pressurized medium to resiliently position said pushrods and clamp ring as the metal can blank engages said clamp ring to produce a corresponding force against said pushrods and cause axial transfer thereof to said piston member;
• configuring biasing means for resilient positioning of said dome plug, said biasing means comprising a donut spring having an interior cylindrical space defining a third axial chamber and being further defined in part by a cover plate, said cover plate having a large aperture extending therethrough and in axial alignment with said integral cylinder housing member to provide hydraulic communication between second and third axial chambers, said cover plate and donut spring cooperating with one another for effective biasing of said integral cylinder housing member in the direction of said first end portion of said integral cylinder housing member;
• and
• conveying a pressurized medium from an external source to said second and third axial chambers to generate and provide a corresponding force to act on and against said concave receiving surface of said piston member for resilient positioning of said pushrods and said clamp ring.

A method of absorbing the mechanical impact resulting from a press arm having a metal can blank fitted thereto and substantially contacting and engaging components comprising an improved double action bottom former to shape and form a desired profile of a can bottom, said method further comprising the step of supplementing biasing means with bias restoration means to restore the preload force of said donut spring upon failure of biasing means to resiliently position said dome plug after compression of said donut spring caused during sustained high cyclic operation, said bias restoration means comprising a spring end plate having a plurality of apertures circumferentially located thereabout and extending therethrough for passage of a corresponding number of tension bolts to secure and fasten said spring end plate to said double action bottom former and to set the pre-load force of said donut spring, said spring end plate further comprising an exterior side and an interior side, said exterior side comprising an exterior circular recess located at each of said apertures of said spring end plate and having a geometric configuration corresponding to a washer used to secure and fasten said spring end plate to said double action bottom former, said interior side comprising an interior circular recess located at each of said apertures of said spring end plate and having a geometric configuration capable of receiving an end of standoff tube used to secure and set the pre-load force of said donut spring, said interior circular recess generally comprising a depth approximately 25% deeper than the depth of said exterior circular recess, whereby restoration of the pre-load force is accomplished by reverse positioning of said spring end plate relative to said interior cylindrical space defined by said donut spring, with each of said interior circular recesses now being fitted with said washer and each of said exterior circular recesses now being fitted with the end of said standoff tube.