US2173766A

US2173766A - Electrical ignition apparatus for internal combustion engines

Info

Publication number: US2173766A
Application number: US184310A
Authority: US
Inventors: Ramsay Frank Raymond Faber
Original assignee: D Napier and Son Ltd
Current assignee: Napier Turbochargers Ltd
Priority date: 1937-01-20
Filing date: 1938-01-10
Publication date: 1939-09-19
Anticipated expiration: 1956-09-19

Description

Sept. 19, 1939. F. R. F. RAMSAY 2,173,766

ELECTRICAL IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed Jan. 10, 1938 Patented Sept. 19, 1939 ELECTRICAL IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Raymond Faber Ramsay, London, England, assignor to D. Napier & Son Limited, London, England, a company of Great Britain Application January 10, 1938, Serial No. 184,310 In Great Britain January 20, 1937 10 Claims.

This invention relates to electrical ignition ap-, paratus for internal combustion engines and of the kind in which means are provided tending to prevent the electrical ignition apparatus causing interference with wireless receiving apparatus used, for example, on'the aeroplane or other vehicle on which the internal combustion engine is installed.

It has been proposed for the purpose of preventing interference with wireless receiving apparatus to interpose a resistance of the orderol 10,000 ohms between the end of each high tension sparking plug lead and the sparking plug terminal. This proposal only partially prevents interference and in an alternative arrangement for preventing interference more completely, a completely screened high tension system is employed, that is to say the whole of the high tension circuit including the high tension sparking plug cables, the central electrodes of the sparking plugs and other parts through which the high tension current flows, are enclosed in a continuous metallic screen which is earthed, that is to say connected to the body of the engine.

This latter expedient, however, tends to cause rapid erosion of the sparking plug points due, it is believed, to theiact that the earthed screen and the high tension cables together form in effect a condenser which gives to the circuit the charac ter of an oscillating circuit, and the object of the present invention is to overcome this difiiculty and thus not only provide elimination of interference which radio signals but also prevent the rapid erosion of the sparking plug points.

To this end, according to the present invention, a resistance is provided between each high tension. cable and its associated sparking plug point in completely screened electrical ignition apparatus for an internal combustion engine.

The value of the resistance may vary but is preferably between 100 ohms and 4,000 ohms and in most cases should be of the order of 1,000 or 1,500 ohms.

In any case this resistance may either be disposed between the end of the cable and the sparking plug terminal or may be disposed within the sparking plug insulator between the sparking plug terminal and the appropriate sparking plug point.

'Anarrangement according to the invention is illustrated diagrammatically in Figure 1 of the accompanying drawing while Figure 2 shows partly in cross-section a constructional arrangement incorporating a resistance according to the in- In the circuit according to the invention shown in Figure 1, A is the secondary winding of the transformer of the magneto or coil type ignition apparatus of which A is the primary winding, one end of the secondary winding A being connected as usual to earth, that is to say to the body of the engine, which is represented by the conductor B. The other end of the secondary winding. is connected as usual to the arm C of a distributor 0 the various terminals of which are connected respectively to the central electrodes of the sparking plugs of the various cylinders. In Figure 1 the distributor is shown as having six such terminals for use with a six cylinder engine and for the sake of simplicity the high tension cable leading from only oneof such terminals to its associated sparking plug is illustrated. In practice each terminal of the distributor would be connected to its associated sparking plug in the manner shown for one terminal. Thus, each ter- 'minal of the distributor is connected to one end of a high tension cable D the other end of which is connected through a resistance D of, say, 1,000 ohms to the central electrode E of the sparking plug F the body F 01' which is, as shown, connected to earth by being screwed into its appropriate cylinder. The high tension circuit is completely screened in known manner, this screening representing a capacity indicated at G.

It will be appreciated that the screening is earthed and encloses also the insulator and the part of the central electrode of the sparking plug lying above the body F thereof and Figure 2 shows one way in which the resistance may be arranged.

In the arrangement shown in Figure 2, the high tension cable D with the usual rubber or like insulation D is screened also in known manner by a woven metallic sheath D The end of-this cable adjacent to the sparking plug passes into an L-sha'ped connector comprising an outer metallic casing G containing a filling of moulded insulating material G One arm of the metallic casing G is externally screwthreaded, as

to. The nipple, which is of ball-like'form, lies within a three-sided spring clip J the sides oi which press thereon so as to make close electrical contact therewith and the resistance D is disposed in a bore in the filling (3 at right angles to that into which the high tension cable D projects. The lower end or the resistance D is acted upon by a cap K against which bears one end of a spring K the other end of which bears on a cap K the caps K and K being capable of sliding longitudinally within a tubular surrounding sheath K and the arrangement being such that the spring K acts through the cap K to press the resistance D upwards so that its upper end makes close contact with the lower face of the spring clip J.

The device is intended for use with a sparking plug F 01' the known type shown in which a metallic screening member F lined with insulating material 13 extends upwards from the body F of the plug and is externally screwthreaded at its upper end to be engaged by a screwthreaded collar L serving to draw a flange G on'the metallic casing G downwards into close contact with the upper end of the screen F".

The filling G of insulating material extends downwards beyond the flange G, as shown, and the arrangement is such that when the device is applied to a sparking plug as shown, the central electrode E of the'plug engages the lower cap K and presses it upwards somewhat against the action of the spring K Thus the spring K not only maintains the resistance D in close contact with the spring clip J but also" serves to carry high tension current between the resistance D and the central electrode E of the sparking plug F With this construction it will be seen that complete metallic screening is provided for the high tension conductor, this screening extending downwards around the resistance D and the insulator and central electrode E of the sparking plug to the body F of the sparking plug which is connected to earth.

It is to be understood that the construction adopted to provide for the interposition of the resistance between the high tension lead and the central electrode of the sparking plug may vary within wide limits according to requirements. the type '0! sparking plug or screening employed, the space which is availableior the connection between the high tension lead and the central electrode of the sparking plug and other requirements. Further, if desired the resistance may be arranged in the length of the high tension lead within the screening, or may be arranged within the insulator oi the sparking plug or an extension or this insulator.

What I claim as my invention and desire to secure by Letters Patent is:

1. Electrical ignition apparatus for internal combustion engines, including at least one high tension cable, a sparking plug to which one end of the cable is connected, a source of high tension current to which the other end 01' the cable is connected, a continuous earthed metallic screen enclosing the high tension circuit, and a resistance of between and 4,000 ohms interposed between the high tension cable and the sparking plug point.

2. Electrical ignition apparatus for internal combustion engines, including at least one high tension cable, a sparking plug to which one end of the cable is connected, a source of high tension current to which the other end of the cable is connected, a continuous earthed metallic screen enclosing the high tension circuit, and a resistance of between 500 and 1,500 ohms interposed between the highv tension cable and the sparking plug point; r

3. Electrical ignition apparatus for internal combustion engines including at least one high tension cable, a source of high tension current to which one end of the cable is connected, a sparking plug, a continuous earthed metallic screen enclosing the high tension circuit, and means including a resistance of between 100 and 4,000 ohms for connecting the other end oi. the high tension lead to the outer end of the central electrode oi the sparking plug.

4. Electrical ignition apparatus for. internal combustion engines including at leastone high tension cable, a source of high tension current to which one end of the cable is connected, 9. sparking plug, a continuous earthed metallic screen enclosing the high tension circuit, and means including a resistance of between 1,000 and 1,500 ohms for connecting the other end of the high tension lead to the outer end of the central electrode of the sparking plug.

5. Electrical ignition apparatus for internal combustion engines including at least one high tension cable, a source of high tension current to which one end of the cable is connected, 8. sparking plug, a metallic screen for the high tension cable and means for connecting the other end of the cable to the sparking plug comprising a coupling member including a metallic casing, a filling of insulating material within the casing having a bore therethrough, means for clamping one end of the casing to the end of the cable screen, means for connecting the other end of the casing to a metallic body which screens the central electrode of the sparking plug, a resistance of between 100 and 4,000 ohms within the bore of the filling, means for connecting one end of the resistance electrically to the high tension cable, and means for connecting the other end of the resistance electrically to the central electrode of the sparking plug.

6. Electrical ignition apparatus for internal combustion engines including at least one high tension cable, a source of high tension current to which one end of the cable is connected, a sparking plug, a metallic screen for the high tension cable and means for connecting the other end of the cable to the sparking plug comprising a coupling member including a metallic casing, a filling of insulating material within the casing having a bore therethrough, means for clamping one end 01' the casing to the end of the cable screen, means for connecting the other end of the casing to a metallic body which screens the central electrode of the sparking plug, a resistance of between 500 and 1,500 ohms within the bore oTthe filling, means for connecting one end of the resistance electrically to the high tension cable, and means for connecting the other endoi the resistance electrically to the central electrode of the sparking plug.

'7. Electrical ignition apparatus for internal combustion engines including at least one high tension cable, a source of high tension current the casing to a metallic body which screens the 75 central electrode of the sparking plug, a metallic member within the bore in the filling to which the end of the high tension cable is electrically connected, a resistance of between 100 and 4,000 ohms aranged in this bore with one end engaging this metallic member, a spring within the bore one end of which acts on the other end of the resistance to press it into contact with the metallic member, and a contact member acted upon by the'other end of the spring and adapted the casing to the end of the cable screen, means for connecting the other end of the casing to a metallic screen surrounding the insulator o! the sparking plug, a resistance of between 100 and 4,000 ohms within the bore oi the filling, means for connecting one end of the resistance elec-' trically to the high tension cable, and means for connecting the other end or the resistance electrically to the central electrode of the sparking P us.

9. A connector for coupling a screened high tension cable in the ignition circuit of an internal combustion engine to a sparking plug comprising a metallic casing, a filling of insulating material within the casing having a bore therethrough, means for clamping one end of the casing to the end of the cable screen, means for connecting the other end of the casing to the metallic body of the sparking plug, a resistance of between 100 and 4,000 ohms within the bore in the -filling, means for connecting one end or .the resistance electrically to the high tension cable, and means for connecting the other end of the resistance electrically to the central electrode of the sparking plug.

10. A connector for coupling a screened high tension cable in the ignition circuit of an internal combustion engine to a sparking plug comprising a metallic casing, a filling of insulating material within the casing having a bore therethrough, means for clamping one end of the casing to the end of the cable screen, means for connecting the other end of the casing to the metallic body of a sparking plug, a resistance of between 500 and 1,500 ohmswithin the bore in the filling, means for connecting one end of the resistance electrically to the high tension cable, and means for connecting the other end of the resistance electrically to the central electrode of the sparking plug.

FRANK RAYMOND FABER RAMSAY.