Appeal No. 2003-2136 Page 3
Application No. 09/562,952
thus made features "a high bonding strength and a small thermal stress, and thereby
durability of the spark plug is improved." (Id. at 19.)
A further understanding of the invention can be achieved by reading the following
claim.
7. A method of manufacturing a spark plug for an internal
combustion engine, the spark plug including an insulator having a through-
hole formed therein, a center electrode made of a nickel-based alloy
disposed at one end of the through-hole, a metal housing holding the
insulator therein, and a ground electrode connected to the metal housing
and disposed to face the center electrode, forming a spark gap
therebetween, the manufacturing method comprising steps of:
attaching a noble metal chip directly on a flat end surface of the
center electrode, the noble metal chip being made of an iridium alloy
containing iridium and a noble metal having a melting point in a range
from 1,500 to 2,100 °C and a linear expansion coefficient in a range from
8 x 10-6 to 11 x 10-6/°C, the iridium alloy having a melting point equal to or
higher than 2,200 °C, a surface area of the flat end surface of the center
electrode, to which the noble metal chip is directly attached, being larger
than a surface area of the noble area [sic; metal] chip which is directly
attached to the flat end surface of the center electrode; and
radiating a laser beam on the noble metal chip in a direction
substantially perpendicular to an axial direction of the center electrode,
thereby forming a molten bond containing more than 1-weight-percent
noble metal having a melting point in a range from 1,500 to 2,100 °C and
a linear expansion coefficient in a range from 8 x 10-6 to 11 x 10-6/°C
between the center electrode and the noble metal chip.
Claims 7-15 and 17 stand rejected under 35 U.S.C. § 103(a) as obvious over
U.S. Patent No. 5,440,198 ("Oshima '198"); U.S. Patent No. 6,094,000 ("Osamura");
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