595 Reporter's Statement of the Case magneto and its enclosure which would permit current to return to the magneto by means of the ignition cable shielding. 40. British patent to Guinness #166,680 (defendant's Exhibit 2) relates to shielding of spark plugs and leads in order to prevent disturbance of wireless receiving apparatus on aircraft. The specification states as follows: The present invention therefore provides for a sparking plug, a metallic screen constructed to extend between the body thereof and the source of supply therefor in such a manner as to afford an electrically continuous path of substantially tubular form surrounding the plug terminal and the supply conductor thereto between the said limits. It is desirable to obtain screening that shall be "electrically complete," that is to say, that shall effectually prevent disturbance by the ignition system for the engines, of wireless apparatus used for signalling purposes. This invention therefore further provides for a sparking plug, a metallic screen constructed to be of sufficently complete physical continuity in all directions to afford "electrically complete screening" for the portions which it encloses. *It is furthermore within this invention to provide at the generator end of the supply conductor a screening sheath similar in function and construction to that provided at the plug end of the conductor. Fig. 1 of the patent, which illustrates in detail the connection of the ignition cable and the concentric shielding therefor with a spark plug, is reproduced herewith. Reporter's Statement of the Case 113 C. Cls. This patent, which relates to details for connecting the shielded cable to the spark plug, suggests to those skilled in the art that a similar method of connection should be used at the generator end of the spark plug lead, that is to say, the connections between the output terminals of the ignition generator should be similar to those shown in connection with the spark plug and suggests that the shielding should be continuous. There is no disclosure of the ignition generator or the character of its shielding and no indication of any connection of the shielding to the return terminal of the ignition generator so that it could be utilized for the return circuit from the plug. 41. British patent to Bairsto, et al., No. 230,902 (defendant's Exhibit 3) relates to improvements in the shielding of electrical ignition systems on aircraft. More specifically, this patent relates to the details of the metallic connection between the braided metal shield of the spark plug cables, the metal shield of the magneto distributor and the outer shell of the spark plug. The details of this connection disclosed in the patent include securing the braid between an inner and outer metallic sleeve having rounded flanges or edges. It is stated that this avoids source of damage to the insulation. The specification refers to the "distributor screen" being made an integral part of the distributor by means of stops or insets molded into the distributor insulation. Such construction is shown in Fig. 6 of the patent, reproduced herewith. The distributor screen or shield 14 is shown as secured to the distributor in the manner just described. The screen as shown does not cover the lower portion of the insulating material of the distributor block and it is therefore incomplete. This patent does not disclose a complete shield entirely closing the ignition system and does not suggest to those skilled in the art the use of the braided shielding on the ignition leads as forming a path for the return flow of current from the spark plugs. 42. The articles entitled "Wireless Navigation for Aircraft" (defendant's Exhibit 4) and "The Elimination of 595 Reporter's Statement of the Case Magneto Disturbance in the Reception of Wireless Siguals on Aircraft" (defendant's Exhibit 4a) by Captain Robinson, both discuss problems relating to radio reception on aircraft and dealing with the interference produced by the magneto ignition systems. The only reference found in the first article is the statement that It is possible to use short wave stoppers to cut out these waves, but by far the most efficient method of eliminating this disturbance is to screen the whole magneto system. The second article discusses various experiments relating to this problem and also suggests a complete shielding of the magneto ignition system. With respect to this shielding the article continues as follows: * The magnetos themselves should be encased in metal shields. The high-tension leads from the mag Reporter's Statement of the Case 113 C. Cls. neto to the sparking plugs should be run in earthed tubes. The same applies to the low-tension leads. When this is done properly there is no trace of magneto disturbance in the most sensitive receiving system. It is not always necessary to put the magnetos in special metal cases. This applies in the cases where the engines are completely cowled. The earthing of the metal shields of the high-tension and low-tension systems is most important. It is not sufficient to bind earthing wires round the metal shield and the earth system if these metal parts are covered in grease. Good earths should be made to the common potential of the metal framework of the aeroplane, consisting of the engines, tanks, and bracing wires. The metal casing of the H. T. leads must be earthed every 18 inches or 24 inches by as short leads as possible. This applies also to the low-tension leads. This earthing at various places provides closed circuits which form oscillating circuits for very high frequencies, and thus help to absorb the short waves radiated from the magneto system. There is no disclosure in the article relative to the use of the shielding as a return path for the ignition current to the spark plugs. 43. "The Year-Book of Wireless Telegraphy & Telephony" (defendant's Exhibit 5) contains an article relating to the problems of the installation of a radio telephone on aircraft. In this article, after a discussion of the oscillatory discharge occurring in the gap of a spark plug and the high frequency waves thus generated and radiated therefrom, the following is stated with reference to shielding: 2. The second method is to screen completely, or enclose in metal, the whole of the component parts of the magneto system. This is a much more simple method when it is carried out while the engine is being built, and before it is installed in the aeroplane, but a very different matter when once the machine is completed without it, as those who have seen the amazing complication of an aero engine will realise. A complete specification for carrying out this work has recently been issued by the Marconi Company, which ensures that no magneto noise will exist on machines where their system is employed. The principle employed in this specification is, firstly, to wire the engine 595 Reporter's Statement of the Case with special copper braided ignition wire; secondly, to provide an effective screened aero plug, which has been designed in conjunction with the Robinhood Engineering Works, the well-known K. L. G. manufacturers, and thirdly, totally to enclose the magnetos with an iron cover on which a coating of copper has been deposited. This article does not disclose or suggest to those skilled in the art the use of the shielding as a return path for the spark plug currents. 44. United States patent to Gill #761,372 (defendant's Exhibit 7) discloses a portable electric gas lighter. This device, which is shown in Fig. 1 of the patent and is reproduced herewith, consists of three basic elements. The lower or bottom element, as shown in the drawing, consists of a tubular metallic battery case containing what is referred to in the specification as “a well-known form of dry battery cell." The customary voltage of a dry battery cell is 12 volts, and for the use involved in the Gill patent those skilled in the art would consider that a battery with a voltage between 12 and 10 volts would be sufficient. The second element extends upwardly from the top of the metal battery case and consists of a tubular metallic member of relatively small diameter as compared to the upper case. This member carries at its top the gas lighting device and its function is to provide an extension of sufficient length to enable the operator to readily reach a gas burner. This tubular member encloses a coaxially located insulated conductor. The third element consists of the lighting device which is a small coil of wire stated to be "made of platinum or other suitable material" and of such size as to be made incandescent when current from the battery is passed through the wire. Flow of current from the battery to the lighting coil is controlled by a switch button which projects outwardly from the combination handle and battery case. The lighting coil is mounted upon an insulating block attached to the upper end of the tubular extension. The lighting coil itself is protected by means of a perforated cap. The specification is silent as to the material from which this $3$936-49- 45 |