Glow plug

June 18, 1940.

2,205,145

A. F. KLlNGNER GLOW PLUG Filed May 23, 1939

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INVENTOR

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Patented June 18, 1940

2,205,145

UNITED STATES PATENT OFFICE

2,205,145

GLOW PLUG

Adolph F. Klingner, Hellertown, Pa., assignor to Edison-Split d or f Corporation, West Orange, N. J., a corporation of New Jersey

Application May 23, 1939, Serial No. 275,171

Claims.

This invention relates to a glow plug especially adapted for use in the cylinder of an internal combustion engine, and particularly in the cyl(Cl. 123—145) by reason of an imperfect electrical joint, the expected result will not occur. Repeated secondary applications of heat may be needed. The user may be entirely unaware of the nature of the difficulty and be put to great annoyance and &amp; even to substantial expense occasioned by the obscure nature of the fault as much as by the existence of the fault itself.

It is therefore the principal object of my invention to provide a glow plug which will over- 10 come the objections which I have encountered in past experience in the .construction of such devices, certain of these objections being as above stated.

The construction of my improved type of glow 15 plug will be readily understood by reference to the annexed drawing, wherein:

Figure 1 is a full-size view of an element, partly in elevation and partly in section, of a two-pole type of glow plug unit per se, without the shell 20 used for mounting it in the engine.

Figure 2 is a view of Figure 1 turned ninety degrees.

Figure 3 is a view of the glow unit ready to be assembled to the electrodes supporting it. ₂₅

Figure 4 is a view of the sleeve mounting element shown in Figures 1 and 3.

Figure 5 is a view of the glow end of a singlepole unit.

Figure 6 is a view similar to Figure 5, but ₃₀showing the use of two of the sleeves of Figure 4.

In the drawing, Figure 1 shows a plug element generally referred to ELS of the series or two-pole type, in which a number of similar plugs in different cylinders may be connected in series _3JSwith a source of current. In this construction, I js a shell by means of which the plug element may be attached to a mounting member going to the engine cylinder. Within the shell I there is mounted a member 2 which is hollow at one end, having a stem 3 which is threaded to receive a nut 4.

The member 2 is insulated from the member ί by suitable insulating material 5, such as mica. Within the member 2 is a central electrode 6 _4gwhich extends through the stem 3 but is insulated therefrom and terminates in the threaded end 7 carrying a nut 8. Between the nuts 4 and 8 there is mounted an insulator 9 having metal collars IS and II. The metal collar II contacts _g0with a metal bushing 24 on the threaded end 7. The bushing 24 is insulated from the electrode 2 by an insulator 25. By this arrangement one terminal wire may be connected between the nut 4 and the metallic collar 10, while the other is inder of a Diesel engine. Such engines are hard 5 to start and in order to assist the compression in generating sufficient heat to ignite the mixture, glow plugs have been used.

In such a plug, a resistance wire heating element is mounted at the end so that when elec10 trie current is passed through it from a suitable source, frequently a storage battery, the heating element is raised in temperature, preferably to red heat or hotter. The heating element is disposed in the most practical location and this 15 local auxiliary heat which is thus generated by the heating element within the engine greatly aids in starting it.

In my many years of experience in building spark plugs for internal combustion engines and 20 also in building glow plugs, I have encountered many difficulties in constructing the latter type of plug. One of the great difficulties which I have encountered is that of mounting the resistance unit so that it will not become loose in the 25 electrode elements which support it. The end of the plug carrying the glow unit is subjected to high temperature and pressures and the deteriorating influences of the fuel, all of which tend to loosen all the joints and increase the :,!0 resistance at the union of the glow unit and its support members, so that the current from the electrical source is cut down to such a point as to seriously affect or actually eliminate the action of the plug. In other words, the heating is im..1.) paired or lost altogether so that the whole purpose of the plug is defeated.

There is another harmful aspect of insecure electrical joints in glow plugs. In multi-cylinder engines, the several glow plugs may be, and ο usually are, connected in series with each other. Thus an unreliable electrical joint in any one plug will increase the resistance of the circuit as a whole and diminish the heating current to all plugs. In such a case the desired and calculated I., amount of heat would not be available at any cylinder even though several of the glow plugs be not, at that time, impaired.

Furthermore, whatever the number of cylinders and number of glow plugs, uniformity of r,o behavior is essential and such uniformity is not attainable if the integrity of the electrical joints cannot be relied upon. For example, an engine user soon learns the approximate length of time to apply current to yield heat to give an easy 55 start. If the glow plug resistance be increased

2,205,145 connected between the nut 8 and metallic collar 11, thereby completing electrical connections to the electrodes 2 and 6. The end i2 of the electrode 2 is insulated from the end 13 of the electrode 6 by a satisfactory insulator 14 such as mica.

For at least a part of the distance between the ends !2 and 13, and the ends carrying the terminal contacts, as just described, an air space 15 may be provided.

The glow unit as shown in Figure 3, comprises a wire of resistance material bent into the desired form, such as a loop 16. One arm 17 of the unit is passed through a sleeve 18, the end of which is beveled at 19 so that when the sleeve 18 is in the position shown in Figure 3, the end 17 of the wire is welded or brazed thereto, forming a fusion joint at the point 20. With the unit assembled as in Figure 3, the sleeve 18, which has a slight taper, being of smaller diameter at the end i 9, is forced into a cooperative, slightly tapered hole 2i in the end of the electrode 6, while the other arm 22 of the glow member is forced into a hole in the electrode 12, after which it is spot-welded into position at 23.

From the foregoing description, it will be seen that the sleeve 18 may be assembled as described to the glow member and when the unit is assembled as shown in Figure 1, the fusion joint 20 is a considerable distance within the relatively massive end 13 of the electrode 6 so that the joint is protected from the direct action of gases and pressures within the engine cylinder. The sleeve 18 is preferably made of a material whereby it will have a coefficient of expansion substantially the same as its supporting electrode, so that the danger of looseness occurring at their junction point is reduced to a minimum. By way of example, but not of limitation, I have used stainless steel for both the sleeve 18 and the electrode 6, referring to Figure 1. It is obvious that only the inner or glow end of the electrode 6 need be made of a material like that of the sleeve 18. I prefer to make the glow wire from an alloy of chrome and aluminum as nickel is more susceptible to attack by the elements of combustion.

In the devices shown in Figures 1 and 5, the space for which these particular plugs were made is not sufficient to allow the use of a sleeve 18 on the arm 22, hence the spot-welding operation 23. I have found that most of the trouble with glow plugs has been in the union between the glow wire and the central electrode, but where space permits, the arm 22 may also be provided with a sleeve 18' as is shown in Figure 6.

The construction herein described is much cheaper than any other construction of which I am aware, and from the tests that I have made, I have found it to be more satisfactory than any other glow plug which I have ever constructed oi’ of which I have knowledge.