US3300672A - Spark plug with anti-fouling means and fixed spark gap - Google Patents

Description

Jan. 24, 1967 B. c` FISHER SPARK PLUG WH ANTFOULNG MEANS AND FIXED SPARK GAP F11ed Ma 27, 1963 the passage around the threads during the intake stroke cls the entire device and supplies the region around the electrodes With fresh ail Which iS forced int0 the Space around the insulator and the Wer portion of the shell with the incoming fue1 mixture to provide a highly coInbustible mixture vvhich insures easy starting and very smooth idling I have found that exceuent results are produced vvhen the dinlensions of the parts adjacent the sparking electrodes are as follovvs:

Diameter of bore 11 --Inches 28S to .290 Iength of bore 11 including Shoulder 2 and pr0jections 35 Inches-- .432 t0 .437 Diameter of ij1sulator portion l8 d0 .235 t0 '240 Length of insulator portion 18 d0 .120 to 1ZS Diameter of insulator portion 18 d0 'Z3S t0 .240 Length of insulator portion 18 do .120 to 12S Diameter of insulator p01tion l -d0 .200 to .20 Iength of insulat0r ortion l ----d0 10 to 1S outside diameter of Split tube electrode 34 dO 12 Inside diameter of electrode 34 d0 07 l)istance betvveen end of projections 35 and insulator Inches .030 to .040 Taper of end Of She11 and projections 35 30 I have found that when the tllbe 34 iS made of nickel and the shell is made of non-0xidizing cold rolled Steel, such aS that knovvn as "C R.S. BIII3 the Surfaces of the electrodes do not 0Xidize and T10 high fesistance for the Spark iS built up at these Surfaces. Hence a Spark iS roduced at a v01tage n1uch lowel than that required fol' an ofdinary spark plug. Tests show that the spark OC curs at 4,000 V0lts, leaving a voltage reserve in the coil at all load requiren1ents There is thus almost n0 excess heat generated by high cufrent in the device or the aSSO- ciated ignition circuit, and an infa11ible spark is produced at aTly engine speed vvhile One en1b0dinent of the invention has been Shown and described, various m0difications may be nade in the arrangement of the parts and in the geometry there0f, and I do not therefofe Wish t0 liInit Tny invention to vvhat has been shown and described, except as Such limitations occur in the appended caim' vvhat I desire t0 claim and Secure by Letters Patent is:

An ignition device for an internal combustion engine comprising:

(a) a tubular Shell having a body p0rtion and a threaded portion of Smaller cross section than said body p0rtion for attaching said device to an engine block, said She11 having a first cylindrical bore through the threaded portion there0f and a Second cylindrical bore of larger diarneter than said TSt bore vvithin Said body portion and provid ng a tapered shoulder between the tw0 bores,

(b) an insulator extending through Said Shell With one end of said insulat0r tern1inating near the end of the threaded portion of said shell and the other end of said insulator extending out of said body portion, said insulat01 Within said second boIe of Said Shell having a dian1eter to iit easily Within said Second bore and the portion of said insulator vvithin Said first bore having three ortions of Successively decreaSing diameters providing Successively greater distances between the inner vvall of aid Shell and said insulator tovvards said one end of said insulator, said insulator having a tapered Shoulder between the largest of said laSt-mentioned portonS and the portion of said insulator vvithin sai(1`second bore, the taper of Said shoulder being substantially the sanle as that of said tapered shoulder in Said Shell, the portions of successively decreasing diameters having shoulders between them With Sharp edges,

(c) a. conductor extending through Said insulator,

(d) a cup-Shaped electrode set into said one end Of said insulator and in contact vvith said conductor, vvith the end of said electrode substantia11y uSh With the end of said insulator,

(e) means for providing a gastight connection between said Shell and said insulator,

(f) a Shoulder on the 0uter Sufface between Said body portion of said shell and said threaded ortion, Said shoulder lying in a plane perpendicular to the axis of Said shen,

(g) a groove in said Shoulder,

(h) at least one aperture betvveen the outer Surface Of said body portion and Said groove, said grove being located S0 as to provide a c0mmunication between said gr00ve and the helical passage around Said threads vvhen Said device is Secured in place in an engine b10ck, and

(i) at least one inwardly extending projection froln the end of said threaded ortion of said she11 and tefminating appr0ximately .03 inch from the end of said insulator containing said cup-Shaped elec trode, the edges 0f said invvardly extending projections Which are towards the adjacent end of Said Shell being uSh axiauy With the end of said insulator and the app[0xi!nate spacing of the three portions of s11ccessive1y decreasing diameters of Said insulator from said Shell being respectively .010 .00, and '080 inch References Cited by tle Exalniner UNITED STATES PATENTS l,z16,l39 z/1917 Kopl 313143 1,37,10 /192 vv00dr00f 313137 Z,S9l,718 4/1952 Paul 313 x 2,899 8 8/199 DOllnbeTg 313130 x 3 012 084 12/196l Fisher. 3,016,4ll l/l962 Fisher 313llj FOREIGN PATENTS 344,j7l 3/ 1931 (...Teat Bitain

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