US 1799225 A
Description (OCR text may contain errors)
April 7, 1931.
H. GERDIEN EIT AL SPARK PLUG Filed Dec. w8, 1928 s 4 o j MM mumm- Patented Apr. '7, 1931 `uNrrEn STATES HANS GERDIEN, F BERLIN-GRUNEWALD, AND REINHOLD REICHMANN, OF BERLIN,
GERMANY, ASSIGNORS T SIEMENS & HALSKE' AKTIENGESELLSCHAFT, 0F
SIEMENSSTADT, NEAR BERLIN, A CORPORATION 0F vGERMANY SPARK PLUG- appuemon med'necember s, 192s, sei-iai No.
Our invention relates to improvements in spark plugs.
It is already known to construct the insulators of spark plugs of quartz, if preferred in two parts. It has, for instance,- been proposed to construct the lower part only of the insulator, adjacent to the spark gapand subjected to the highest tempera-y tures, of quartz.
According to ourNinvention at least that part of a two-part insulator of a spark plug which is adjacent to the spark gap, or the end facing the combustion chamber of the engine is constructed of aluminum-oxide. The insu ator may be constructed of aluminumoxide, produced from sintered or fused alu- 4 minum-oxide, such as artificial sapphire or structed of aluminum-oxide.
ruby. Sintered and fused aluminum-oxide is indiier'ent to temperature fluctuations,
like quartz glass. It is, further, atthe high temperatures in question less subject to reactions, so that its surface facing the combustion chamber is not attacked in an way. It may be advisable to olish this sur ace, so that any particles of car n preci itated upon it are easily dislod d and thus t e plug oes not become chokecby carbon deposits.
In the drawings attached hereto and forming part of our specification two embodiments of our invention are illustrated by way of example.
In the drawings- Fig. 1, represents a longitudinal section throughA one construction of our improved spark plug, and
Fi 2, a longitudinal section through a m cation of the plug. v
Referring to Fig, 1 ofthe drawings, 1 is the lpart of the insulator directly exposed to the ot products of combustion in the engine, which part according to our invention is con- 2 is the main portion of the insulator, mound in' the i socket 4.by means of the-packings '3 in the customary manner. The central electrode-5 main rtion2 of-thensulator and the tipl 1` are joined between this collar 6 and a clampdevice, such as a nut, located atthe outer elili of the ignition electrode.
324,604, and in Germany December 23, 1927.
Fig. 2 illustrates at 7--a different design of the insulator portion, which according to our invention is constructed of aluminum-oxide.
The remaining parts of .the spark pl are assumed to be similar to those shown in ig. 1 and are indicated by the like numeralsv of reference. The end of the insulator portion 7 is .outwardly and inwardly tapered and is provided at. its thicker end with a flange, which abuts against the main portion 2 of the insulator. The surface of the tapering part 7 is preferably highly finished, so that no carbon or .the like can adhere to it.
On account of the' high costs caused by machining fused a1uminum-oxide, the insulator tip is preferably produced by sintering aluminum-oxide at temperatures of more than 1600 C.
The manufacture of sintered insulators for spark plugs is preferably carried out in. the following manner: A
The aluminum-oxide is, prior to the sintering process, moulded by one of the meth- "ods known in the art, dried and then sinhardly diiiers from those vmade of fused aluminum-oxide yregardin its refractory and insulatin quallties. ts production is', however, far ess expensive, because the high costs of machining are eliminated.
The manufacture of the insulator may be 'started from ordinary aluminum-oxide as well as from an loxide which has been subjected to a preliminary fusing. As it is comaratively easy to produce large-size insua'tors b sintering, not onl the portion of the insu ator subject to the ighest temperatures should be made ofaluminum-oxidesiny -tered at over 16,00 C., but the entire insulator. is provided with a collar or shoulder 6. The
, Careful tests have liroventhat aluminum oxide for' insulators produced as described hereinbefore is superiorto all other materials 105 electrodes, an
chemical attacks by combustion products in the cylinder, in particular also its resistivity to so-called anti-knocking metal'compounds now frequentl added to the fuel, because s aluminum oxi e does not form compounds with these combustion products. It should be n oted that for instance the glazing of porcelain insulators which consists of 'sili` well known to crack at quick variations in temperature.
5. On account of its hightelectric insu-- lating quality not impaired by chemical reactions with the combustion products. Also this r uirement is not fulilled b porcelain.
mounting said electrodes, said insulator consisting at the end facing the combustion chamber substantiallyentirely of aluminum-oxide.
3. A spark plug, comprising conducting electrodes and an insulator consisting'of sintered aluminum-oxide.
4. A spark plug, comprisinglconductin electrodes andan insulator for mounting sai electrodes, said insulator consisting at least l at the end facing the combustion chamber of the engine of sintei'ed aluminum-oxide. 5. A spark plug, comprising conducting electrodes and lan insulator consisting substantially entirely ofl aluminum oxide, sintered at suitable temperatures vto form a sub-A stantially crystalline body.
6. A spark plug, comprising conducting electrodes and an insulator for mounting said electrodes, said. insulator consisting at lthe end facing the combustion chamber substantiallyentirely of aluminum oxide sintered at suitable temperatures to form a sub'- stantially crystalline body.
In testimony whereofwe aix our signatures.
HANS GERDIEN. REINHOLD REICHMANN.
-6. uminum oxide has great ensity ren- 30 dering it impermeable to gases, and
7.' t iseasily molded into any desirable v form vin unsintered condition and, there? fore, -easily manufactured by sintering at -high temperatures.. With respect to points 'so 6 and 7 porcelain would fulfill these requirementslinasmuch as porcelain has great density, and: when glazed is impermeablev to n gases and can be molded before it is red.
In some of the annexed claims we have 4 characterized the insulator as consisting substantially entirely of aluminum oxide, by which we mean that the insulator thus produced consists of substantially pure aluminum oxide, excepting such impurities 4,5 as would not have any eiect upon the aforementioned properties.-l l
The use of our insulator of fused or sini tered aluminum-oxide is particularly advantageous, if the internal combustion engine v 50 is fed with fuel containing metalcom ounds,
and in which the precipitation of con ucting layers upon'the msulator is easily possible. The insulator'consist' of aluminum-oxide may be provided in we the creeping path. Various modifications and chan es may be made without 'departing from t e spirit .and the of the mventlon. VeAclalm ol'r invention: spar p -comprsin .con uctin electrodes and .aiiginsulator cosisting sub stantially'entirel ofaluminum-oxide. 2. A spark ,y com risingconducting an ator serving for lll known manner with 'l5 petticoatsin .order to increase the length of