Metal deforming – By tool-couple embodying nonplanar tool-face
Reexamination Certificate
1999-12-30
2001-07-10
Crane, Daniel C. (Department: 3725)
Metal deforming
By tool-couple embodying nonplanar tool-face
C072S316000, C072S322000, C029S509000, C029S243580
Reexamination Certificate
active
06257043
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the hemming of sheet metal and more particularly, to a hemming apparatus and method for forming a generally flat hem.
BACKGROUND OF THE INVENTION
It is well known to construct motor vehicle body panels, doors, hoods, fenders, tailgates, trunks and deck lids by stamping an outer sheet metal panel and separately stamping an inner sheet metal reinforcing panel and then joining the two panels together by hemming a flange of the periphery of the outer panel over an adjacent edge of the inner panel to secure the panels together. Desirably, the outer panel is slightly larger than the inner panel to provide a border flange portion along the periphery of the outer panel which can be folded over the peripheral edge of the inner panel to define the hem flange which connects the two panels.
When the flange is folded over the peripheral edge of the inner panel with a traditional hemming apparatus and method, the resulting edge of the hemmed panels has a generally smooth, curved or arcuate shape with a diameter of the bend equal to twice the thickness of the outer panel plus the thickness of the inner panel. With inner and outer panels of the same thickness, the diameter of the bend for a standard hemming apparatus and method is equal to three times the thickness of a sheet metal panel. While many standard hemming methods and devices produce a smooth and fair hem or fold line, the relatively large bend diameter of the fold line is believed to reflect light in various directions along the curved fold line which is believed to give the visual appearance that the gap between adjacent hemmed panels of the vehicle body is larger than it actually is, is inconsistent or that the panels are not flush with one another.
In a conventional hemming process, the flange of the outer sheet metal panel is folded flat against the inner panel. In a different hemming process, which may be referred to as an “open hem” process, the flange of the outer sheet metal panel is folded back over the inner panel to secure them together, but the flange remains inclined to the inner panel resulting in a gap between the outer edge of the flange and the inner panel in which foreign material may collect. In use, this gap may also allow the inner panel to shift relative to the outer panel resulting in misalignment of the panels. Thus, this gap between the flange and inner sheet metal panel must be filled with a sealing material to prevent foreign material from collecting in the hem. This sealing operation increases the cost and time to assemble the panels of the vehicle body.
SUMMARY OF THE INVENTION
A hemming steel constructed to fold or hem a flange of an outer sheet metal panel onto an inner sheet metal panel has a forming face with a first, generally flat section and a second section inclined to the first section to provide a finished, hemmed flange having an outer portion closed or folded flat onto the inner sheet metal panel and an inner portion adjacent to the fold line which is inclined to the outer portion providing a significantly reduced radius or diameter of the fold line bend. The second section of the hemming steel is preferably generally planer such that the inner portion of the hemmed flange is generally flat and provides an outer bend diameter along the fold line of the outer sheet metal panel which is less than three times the thickness of the sheet metal panels and may be approximately equal to or less than the thickness of only the outer panel. The significantly reduced bend diameter is believed to provide a smooth and fair fold line which has a more consistent appearance when viewed from different angles to improve the appearance of the hemmed panels of the vehicle body in assembly. Visually, the gap between adjacent hemmed panels such as a fender panel and a door panel on a vehicle appears to be significantly narrower even though physically it is actually the same width as a prior conventionally hemmed adjacent panels. Further, with the outer portion of the hemmed flange folded flat against the inner sheet metal panel, no sealing operation is required to prevent foreign material from collecting between the flange and inner panel. The angle at which the second section of the forming face is inclined relative to the first section can be changed to allow the location of the peripheral edge of the inner panel to be varied relative to the fold line.
Objects, features and advantages of this invention include providing a hemming apparatus which produces a hemmed flange having a first portion inclined relative to a second portion from a relatively simple method and apparatus, provides a hemmed flange with a reduced bend diameter, provides a fold line which has a more consistent appearance when viewed from different angles, provides adjacent hemmed panels on a vehicle visually appearing to have a narrower or smaller gap between them, provides a closed hem thereby eliminating the need for a separate assembly operation to provide sealing material between the hemmed flange and inner panel, is readily adaptable for use with panels having a different configuration, is reliable, durable, of relatively simple design and economical manufacture and assembly and has a long, useful service life.
REFERENCES:
patent: 2455767 (1948-12-01), Henchert
patent: 4604786 (1986-08-01), Howie
patent: 4642871 (1987-02-01), Ookubo
patent: 4719689 (1988-01-01), Yamamoto
patent: 5195580 (1993-03-01), Hoeffken
patent: 5272903 (1993-12-01), Evans
patent: 5315855 (1994-05-01), Jackson
patent: 5457981 (1995-10-01), Brown
patent: 6000118 (1999-12-01), Biernat
patent: 6029334 (2000-02-01), Hartley
patent: 686651 (1930-07-01), None
Crane Daniel C.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Unova IP Corp.
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