Ignition device having an electrode with a platinum firing tip and method of construction

#1. Technical Field

#This invention relates generally to spark plugs and other ignition devices, and more particularly to electrodes having platinum firing tips and to a method of construction thereof.

#2. Related Art

#These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description of the presently preferred embodiments and best mode, and appended drawings, wherein like features have been given like reference numerals, and wherein:

#FIG. 1 is a partial side view of a spark plug having a center electrode and ground electrode constructed in accordance with one presently preferred embodiment of the invention;

#FIG. 2 is an enlarged partial side view of an initial step in the construction of the ground electrode according to one presently preferred embodiment of the invention;

#Referring in more detail to the drawings, FIG. 1 shows a firing end of a spark plug 10 constructed according to one presently preferred method of construction of the invention. The sparkplug 10 includes a metal casing or housing 12, an insulator 14 secured within the housing 12, a center electrode 16, a ground electrode 18, and a pair of firing tips 20, 22 located opposite each other on the center and ground electrodes 16, 18, respectively. The housing 12 can be constructed in a conventional manner as a metallic shell and can include standard threads 24 and an annular lower end 26 from which the ground electrode 18 extends, such as by being welded or otherwise attached thereto. Similarly, all other components of the sparkplug 10 (including those not shown) can be constructed using known techniques and materials, with exception to the center and/or ground electrodes 16, 18 which have firing tips 20, 22 constructed in accordance with the present invention.

#As is known, the annular end 26 of housing 12 defines an opening 28 through which the insulator 14 preferably extends. The center electrode 16 is generally mounted within insulator 14 by a glass seal or using any other suitable technique. The center electrode 16 may have any suitable shape, but commonly is generally cylindrical in shape having an arcuate flare or taper to an increased diameter on the end opposite firing tip 20 to facilitate seating and sealing the end within insulator 14. The center electrode 16 generally extends out of insulator 14 through an exposed axial end 30. The center electrode 16 is constructed from any suitable conductor, as is well-known in the field of sparkplug manufacture, such as various Ni and Ni-based alloys, for example, and may also include such materials clad over a Cu or Cu-based alloy core.

#The ground electrode 18 is illustrated, by way of example and without limitations, in the form of a conventional arcuate ninety-degree elbow of generally rectangular cross-sectional shape. The ground electrode 18 is attached to the housing 12 at one end 32 for electrical and thermal communication therewith and preferably terminates at a free end 34 generally opposite the center electrode 16. A firing portion or end is defined adjacent the free end 34 of the ground electrode 18 that, along with the corresponding firing end of center electrode 16, defines a spark gap 36 therebetween. However, it will be readily understood by those skilled in the art that the ground electrode 18 may have a multitude of configurations, shapes and sizes.