US2442015A - Dehydrator for ignition systems - Google Patents

Description

May 25, 1948. M. F. PETERS ET AL.

DEHYDRATOR FOR IGNITION SYSTEMS Filed May 22, 1944 INVENTO MELVILLE F. PETERS BY JOHN J.PHILL|PS AGENT Patented May 25, 1948 DEHYDRATOR FOR IGNITION SYSTEMS Melville F. Peters, Beltsville, Md., and John J. Phillips, Irvington, N. J., assignors, by mesne assignments, to Titeflex, Inc., Newark, N. J a

corporation of Delaware Application May 22, 1944, Serial No. 536,654

Claims. 1

This invention relates to improvements in ignition equipment for internal combustion engines and particularly to the devices used with a radio shielded spark plug of the style employed with aircraft power plants where it is required that complete metal jacketing be provided to cover the high tension current supply for the purpose of avoiding interference in the reception of radio communications.

Shielded spark plugs are well known in the aircraft industry. The types of electrical connection to the plugs from magnetos or from other current supply sources have been more or less standardized to meet operating and service conditions and usually comprise a spring-type connector of some description which is mechanically and electrically fastened to a shielded ignition cable. It is necessary to provide adequate insulation to preclude the possibility of flash-over from the open spring connection within the plug at magneto current potential to the metal barrel shielding the plug and to shielding fittings and devices at ground potential which are employed to jacket the cable conducting the current to the plug.

Even with the customary precautions of insulation, electrical flash-over is occasionally experienced between the open connection at the electrode in the plug and the shielding spark plug barrel. The tendency to flashover is aggravated by an accumulation of moisture within the barrel resulting either from plug leakage or from condensation. In the case of plug leakage, liquids from the products of combustion Within the engine cylinder may pass the insulation adjacent to central electrode and find their way into the shielding barrel. This condition may be eliminated by the use of sealed electrode plug design as in the patent to Rabezzana, Number 2,336,569.

On the other hand, the condensation within the spark plug barrel resulting from cooling off of the engine is troublesome despite the use of scaled spark plugs. Such conditions of moisture and water vapor and the compounds formed by the potential gradients in the spark plug cause difiiculties in starting aircraft engines.

Various expedients have been employed for overcoming difliculties of this sort due to moisturein the plug. Jelly-like compounds of petroleum and other oils have been inserted within the spark plug barrel so that air is excluded when the connection devices are assembled in the plug permitting no possible condensation. Also, for the same purpose, entire harnesses have been dehydrated using mechanical devices and controls.

It is a principal object of this invention to provide a means by which an accumulation of water vapor can be absorbed before condensation on the elements of the plugs or on the electrical connecting devices. A further object of the invention is to provide a means for this purpose which is replaceable, inexpensive, and which may be adapted to standard shielded aircraft spark plugs.

Other and ancillary objects will be noted as the description proceeds. The novelty resides in the construction, combination, and arrangement of parts substantially as shown in the specification following, and as defined in the appended claims.

The invention contemplates solutions designed in the form of accessories to the spark plug con nection and which are integral with the elements of the connection although such construction may not necessarily be considered the only solution for the purpose.

In the drawings,

Figure l is a side elevation partially sectioned, showing a flexible detachable style aircraft ignition lead assembled to a spark plug and employing our invention;

Figure 2 is an enlarged fragmentary section view of the connecting element employing the invention which is used within the spark plug Figure 4 is a cut-away side view of the spark plug showing a modified form of the invention; and

Figure 5 is a fragmentary section of the cutr away in Figure 4.

Referring now to the drawings, wherein like numerals are used to designate like parts throughout the several views, numeral ll refers to a shielded air-craft spark plug which in service is associated with a cylinder of an internal combustion engine, not shown, in a conventional manner.

A supply of current to the spark plug is provided through a flexible detachable shielded spark plug lead; parts of the lead include a flexible metal conduit Hi to shield and protect the ignition cable between relatively moveable parts and an elbow attached to the flexible conduit for directing the ignition cable at a pre-determined angle to the spark plug. An insulated cable I3 is disposed within the assembly of flexible conduit and elbow and terminates at one end in the flexible electrical conection element 29 for estabishing contact with suitable elements of an ignition shielding harness, not shown.

Projecting from the other end of the lead are certain parts to be described later forming an electrical connection to the spark plug electrode 28. Conventional threaded connecting devices l5, l5 and [5" provide mechanical connections between conduit I and elbow i2; elbow i2 and spark plug barrel i9; and conduit iii and a suitable connector; not shown, at the ignition manifold, re spectively.

Referring now to Figure 2, the electrical connection which is constructed to fit within the spark plug barrel to provide contact with the spark plug electrode 28 is shown separated from the spark plug l l. The conductor cable 52 forming a part of this connection includes a metallic conducting element i l suitably insulated which is directed from connection and which projects from within the shieldin elbow iii. A flexible rubber sheath i5 is disposed in gas tight association over the projecting end of cable 53 and serves to position the cable centrally within the elbow and within the spark plug barrel and also insulates cable l3. It will be noted here that this sheath is extends slightly beyond the end of the conducting cable, and that a circumferential ledge is disposed about the sheath at the location of the abutment of spark plug i l and elbow 42. The purpose of this ledge is to provic e a moisture seal at this joint where the spark plug nut forming a part of connection is drawn up on the male threads provided on spare plug barrel IS. A relatively rigid insulating member ii is disposed over the end of the flexible sheath 26 providing a terinina to the insulation which is less destructible physically and electrically than the flexible insulating material of sheath. iii. The material chosen for the rigid insulator ii may be ceramic or other insulation which is not lilrely to carbon track if a flash-over should occur at the open connection within the spark plug barrel at the spark plug electrode, In. an actual occurrence of electrical flashover, it would be necessary for a spark to jump the gap between the connection at the spark plug electrode 28 and the spark plug barrel at its junction With spark plug elbow l2. This is the case since the inner cylindrical surface or the spark plug barrel is insulated by a ceramic or mica sleeve 33 which has less tendency to break down than the air gap from electrode 28 to the barrel 9 at its junction with an elbow l 2 A threaded stud connection 2? is provided at the termination of the conductor i l of cable it. This stud may be fastened to conductor M mechanically and electrically by means of a crimped connection or by soldering. Stud 2? may be hollow if it is desirable to supercharge the spark plug barrel by directin a flow of air under pressure through the conductor l 'l. As shown in the drawings, a circular bore is provided in the end of flexible sheath IE5 and in the web of the relatively rigid insulating element ll permittin passage therethrough of stud 27 so that the threaded portion of stud 2i projects out beyond the assembly.

A cylindrical shell preferably constructed of beryllium copper or stainless steel is fastened to the stud 2! so that its base abuts the web of the insulator ll holding it in place over the flexible insulating sheath l6. Four spring lingers 2d are suitably-formed on the end of shell 22 to serve as a spring-type connector when associated with the spark plug electrode 28.

It will be noted here that the assembly of rigid insulator IT and flexible insulator l6 form a substantially cylindrical projection which projects from the spark plug elbow l2 and which has approximately the same outside measurement as ias the inside diameter of the insulating lining i8. This construction permits assembly with a minimum amount of precluded air within the spark plug barrel.

Within the shell is disposed a quantity of dehydrating materia 2.5 such as silica jell or activated alumina. A perforated disk 25 retained in place by four additional fingers E l formed integrally with the shell and bent at right angles to the walls of the shell, shown more clearly in Figure is used to provide mechanical support for the dehydrating material and still permit any gas surrounding the sh ll to penetrate the dehydrating material. The quantity of dehydrating used may be varied with the design of the connector assembly and should be sufiicient to meet average operati g conditions. Such an assembly of parts provides for an electrical conto the spark plug by the association of the mot l conducting elements comprising conductor stud and shell and also would p ovide for removing moisture or water vapor ,ich collects within the spark plug barrel.

0 the use of a shell of this er, as shown as n Figure l, may be enarged fragmentary debruction of Figure l. This container co rises a central conducting core 253' at the ds of which are rigidly fastened metal washers The dehydrating material is retained in p ace about core by a loosely woven metal wra; p which terminates at. and is attached t is ill as by sold ring. In the use of i an assembly it is necessary to increase the length the spark plug barrel beyond that whic.. is convention lly used in order to accociodate the increased 1 gth of the open connection extending upwardly toward the noninsulated portions of the sh .lding assembly.

The lower washer serves to contact the central spark plug electrode which in this modification is shown as a leakproof style electrode similar to that of United States Patent 2,336,569, and the upper washer provides a suitable element against which a conventional spring contactor for carrying high tension current may be resiliently attached. Intermediate of the two washers the metal core 23' and retaining screen 25' will conduct current to the electrode 28" during the interval of ignition current sup ply. As in the case of the previous description of l and 2, a seal may be provided at the abutment of the shielding barrel top and the shielding conduit 52 associated therewith to prevent moisture entering the barrel.

The quantity of material in the liquid state which condense: within the barrel of a shielded spark plug when aircraft engine has cooled depends upon the dew point of the vapor in a gaseous state within the plug during operation. An extrem ly fine film of this liquid is suflicient to cause misfiring, particularly inasmuch as the impurities in the condensed vapor are usually both. nitrogen-oxvgen compounds carbon dioxide, and perhaps some oxides of sulfur all of which impart relative conductivity to water.

In operation of the engine, the dehydrating material used either as in shell 22 of Figure 2 or cylindrical container of Figure l, serves to absorb vapors during engine cooling before they condense on the walls of the spark plug sleeve and tail of the connector assembly, and hence insures eificient starting. During operation, and as the engine temperature increases, the water vapor will be driven off from the dehydrating agent. However, this causes no harmful electrical effects since it is'theli in a gaseous state. If after a period of time the effectiveness of the dehydratin agent has been aiiected by gases, a replacement dehydrating container may be substituted for the defective unit.

While the invention has been illustrated in what is considered to be its best application, it may have other embodiments without departing from its spirit and is not therefore limited to the structure shown in the drawing.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A terminal assembly for connecting a flexible radio-shielded spark plug lead with a spark plug that has a shielding barrel and an electrode located in the lower portion of the barrel, said assembly including an insulated cable for conducting current, a flexible metallic shield surrounding the insulated cable, a shoulder on the sleeve, a nut that threads on the upper end of the barrel and that abuts against the shoulder on the shield for connecting the shield with the barrel, means to seal the shielding barrel from the atmosphere including a sheath that surrounds the insulated cable in the region of said shoulder and that has a portion which is clamped between the end of the metallic shield and the end of the barrel, a relatively rigid insulating element that surrounds the end of the insulated cable beyond the metallic shield, said element being of substantially the same diameter as the inside diameter of the barrel so as to fill a substantial volume of the interior of the barrel and thus reduce the amount of air or gas within the barrel, a metal dehydrant container at the lower end of said insulating element and detachably connected to the end of the cable, a perforated closure for the lower end of the container, and a plurality of axially-spaced fingers comprising integral extensions of sides of said container, some of said fingers being bent over to retain the closure in place and other of the fingers converging toward one another and comprising resilient contacts that bear against the electrode in the barrel to complete the ignition circuit.

2. A terminal essembly for connecting a flexible radio-shielded spark plug lead with a spark plug that has a shielding barrel and an electrode located in the lower portion of the barrel, said assembly including an insulated cable for conducting current, a flexible, metallic shield surrounding the insulated cable, means for connecting the shield to the upper end of the barrel, means to seal the shielding barrel from the atmosphere, structure on the end of the cable beyond the end of said shield and filling a substantial par-t 01- the volume within the barrel to reduce the volume of gas within the barrel, and a perforated container for dehydrating material within the barrel for absorbing moisture contained in any air or gas that leaks into the sealed interior of the barrel, said container including metal contact means that bear against the electrode and at least a portion of said container comprising a conductor for completing the ignition circuit between the end of the cable and said electrode.

3. In a radio-shielded ignition system having a spark plug with a shielding barrel, an electrode at the lower end of the barrel, an insulated ignition cable, a flexible metallic shield around the ignition cable, and means for sealing the barrel from the atmosphere, the combination with said cable of a perforated container for dehydrant material, detachable fastening means connecting the container to the end of the cable within the barrel and comprising the conductor for the ignition circuit between the end of the cable and the electrode, the container having resilient fingers at its lower end for contact with the electrode.

4. An ignition system including in combination a spark plug having a shielding barrel, an electrode having a surface exposed to the interior of said barrel, a lead having a shield connected with the barrel and an insulated cable that extends into the barrel for supplying current to the electrode, means sealing the barrel from the atmosphere, and a container positioned within the barrel and filled with dehydrating material.

5. The combination with a spark plug having an electrode and a shielding barrel extending for a substantial distance above the electrode, of a spark plug lead including an insulated cable that extends into the barrel and that is electrically connected with the electrode, and a shield connected with the upper end of the barrel and covering the insulated cable beyond the barrel, a container filled with dehydrating material, said container being perforated for communication of its interior with the air or gas within the barrel, and said container being located in the lower end of the barrel and in heat conducting relation with the lower portion of the plug so that the material in the container becomes hot enough for moisture to be driven off when the plug is in use and in preparation for absorbing moisture in the barrel as the plug cools after use and before the plug has cooled enough for water vapor to condense within the barrel.

MELVILLE F. PETERS. JOHN J. PHILLIPS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date vRe. 20,618 Douglas Jan. 11, 1938 1,992,852 Bader Feb. 26, 1935 2,112,322 Wyatt Mar. 29, 1938 2,115,011 Douglas Apr. 26, 1938 2,315,049 Cronstedt Mar. 30, 1943 2,316,504 Dayton Apr. 13, 1943 2,350,367 Peters June 6, 1944 2,352,158 Bishop June 27, 1944 2,365,219 Rose Dec. 19, 1944 2,385,191 Brunelle Sept. 18, 1945

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