US1957803A - Spark plug tester - Google Patents

Description

May 8, 1934. H. RABEZZANA ET AL SPARK PLUG TES TER Filed Oct. 428, 1935 50 shaft Patented May 8, 1934 PATENT OFI-ics UNTED STATES 1,957,803 SPARK PLUGTESTER Hector Raben-rana. and Ralph L. Phelps, Flint, Mich., assgnors to A C' Spark Plug Company,

Flint, Mich., a company of Michigan Application October 28, 1933, Serial No. 695,578

comms.

l with a shunt circuit to leak current from the spark plug circuit. With such device, the brightness of the flasher will not be materially aiected by current leakage through the shunt if the spark plug is ring properly. If, however, the ordinary operation of the plug is faulty the additional current leakage through the tester shunt will cause a weak spark or else complete failure, and the dasher to some extent will be correspondingly dimmed. Glowing of the neon tube results from high frequency oscillations produced upon current discharge across the spark gap of the plug, and its brightness varies in direct relation to the difierential in potential at its opposite ends. With the construction heretofore used, only one end of the tube is directly connected through a conductor with the secondary circuit of the ignition system, and consequently, variations in flash intensity, while discernible to an expert, are not pronounced to the untrained eye. It is now proposed to eliminate this uncertainty and to improve the reading and make more apparent the differences between a spark plug firing regularly under any load and one which misses only under sudden load. For this purpose the neon tube is placed in a wiring circuit so that both ends are connected through conductors of the same capacity and resistance with the spark plug terminal for the flow by induction oi the high frequency current.

For a better understanding of the invention, reference may be made to the accompanying drawing, wherein Figure l shows a portion of an internal combustion engine with the tester applied thereto. Figure 2 is a top plan view of the tester with parts in section, and Figure 3 is a sectional View taken on line 3--3 of Figure 2. Figure l is a side elevation partly in section, and Figure 5 is a diagrammatic view ci the wiring circuits involved..

Referring to the drawing, the box or casing 1 of bakelite or the like, has a depression in its top face to receive a pointer knob 2, carried on a 3 extending through the wall of the casing toward the removable bottom wallv fiA where it mounts a movable switch blade 5. The blade 5,is grounded. through a springl contact nger 6 in wiping contact with the'lower end of the shaft 3 and mounted on the wall of the-'casing by screws which also connect thereto a length of exible cable 7.

Arranged about an arc, whose center is the shaft 3, are a series of four hollow bosses 8--8, each of which receives a conductor element 9, preferably in the form of a carbon stick of a preselected resistance. One end of the carbon stick 9 seats within a thimble 10 having a rounded nose to rest on the bottom wall of the casing, but adapted to make contact with and seat between the split or forked ends oi the switch blade 5, when the blade is swung thereunder. V

The stick 9 -is pressed downwardly by a coiled compression spring 11 at its upper Aend within a cup 12 that bears against an arcuate conductor strip or bus bar 13, extending over the several hollow bosses 9 5.

The bus bar 13 has a connection at 14, with a lead-in cable 15, and at its end is joined to a downwardly extending strip 16 that terminates in an upstanding tab 17 in the compartment that receives a neon tube 18. An opening 19 with a, shad-4 ing shield 20 may be provided for the observation oi the neon tube. interposed between the tab 17 and one end of the tube 18 is a coiled compression spring 21 which holds the opposite end of. the tube in contact with the lead-in wire 22. The two lead-in wires l5 and 22 are of the same resistance and capacity, and their outer ends are joined to a common clip for connection with a spark plug terminal connector. Spacers 23 hold the two wires apart to prevent induction therebetween.

In the construction described, the switch blade 5 may be moved into any one oi iive positions by the movement of the pointer knob 2 into aline- ,ment with projections 24.0, 25, 26, 27 and 28 on the top face of the casing. At any of the stations 25 to 28, inclusive, the switch blade grounds the bus bar 13 through the conductance element 9 associated with the particular station selected, while at station 24 the ground connection is broken. Thus, when the device is in use, a shunt circuit which includes the cable 15, may be closed for current leakage iromthe ignition system in amount depending upon the pointer setting, since the several conductance elements 9 are of different resistances. it is proposed, for example, that the difference in resistors should be approximately 100,000 ohms, starting at about 270,000 ohms and ending'at about 630,000 ,ohms resistance. This enables the one instrument to be used for testing practically all or the various types of engines used in automobiles.

In the use of the device, the cables l5 and 22 are connected to the spark plug and the calici? is grounded at any convenient point on the `en gine, as is illustrated in Figurel. With this ar. rangement of parts, the cable 15, in addition tof I forming a part of the shunt circuit, also provides and with minimum resistance, the strength of the glow conforms to the character of the spark discharge. A

To determine probable plug life, a test is made with the pointer knob set at a given station for the particular type of engine and spark plug, with a conductance element of selected resistance in the shunt circuit. This allows leakage' of current from the ignition circuit and consequently a drop in voltage at the spark gap. If the gap is of proper size and the leakage through fouling not great, then the leakage through the instrument will not be sflicient to'cause the plug to missA even under sudden load. Any irregular ring under test and which is radily discernible through a dimmingofthe neon tube indicates that the plug needs cleaning and regapping or else complete replacement.

It should be noted that the plug is tested in the engine under actual running conditions and when the engine is normally hot. For an accurate readinguthe flashes should be observed through-l out the entire range of quick acceleration, and if it dimsv or disappears at any time, then the observer is informed that the plug is missing and has reached its linut of economical performance. Should the tester indicate irregular firing with a new plug, then trouble lies in other portions of the ignition system which should be carefully checked.

We claim:

1. In a device for testing spark plugs while the engine is operating, a pair of lead wires of substantially1 the, same capacity and resistance adapted for connection with the spark plug circuit, a flasher actuated by high frequency discharge connected at opposite ends with said lead wires to form therewith a closed circuit, and means to shunt current from the spark plug including a conductance element having resistance of a given value.

2. In a device for testing spark `plugs while the .engine is operating, a flasher operated by high frequency oscillations produced by the discharge of current at the spark gap, a cable connecting one end of the flasher with the spark plug, a second cable substantially corresponding in resistance and capacity with the first cable and connecting the opposite end of the flasher with the spark plug, said cables and flasher together constituting a closed circuit, and means including a conductance element of a'given resistance for shunting current from the spark gap.

3. A spark plug tester, including a support, a resistor element of a given resistance value mounted in the support, means to ground said element, a neon tube carried by the support, a conductor element common to said resistor element and one end of said neon tube and adapted for connection with the spark plug circuit, and a second conductor of substantially the same resistance and capacity as the first mentioned conductor, associated with the opposite end of the neon tube for connection with thev spark plug circuit. I

4. A spark plug tester including a casing for a neon tube, a pair of exible cables of substantially the .same resistance and capacity, extending from said casing, with their inner ends connected to the opposite ends of the neon tube, means for connecting the outer ends of the cable with the ignition circuit, and means spacing said cables `in termediate the ends thereof to eliminate induction of one over the other.

5. Means for testing the operating condition of a spark plug, including a casing, a neon tube within the casing, a pair of cables extending from 'the casing for connection at the outer ends with a spark plug and .having their inner ends connected to opposite ends of the neon tube to provide a closed circuit for high frequency current ow,a conductance element within the casing, having a resistance of a predetermined value, a switch for grounding said element and means connecting said element to one of said cables and providing therewith a shunt circuit for by-passing current from the spark plug.

6. A device for testing spark plugs while the engine is operating, including a closed circuit containing a ilasher operated by high frequency oscillations result' -g from current discharge at the spark plug, and a shunt circuit for leaking current from the ignition system.

HECTOR RABEZZANA. RALPH L. PHELPS.

los

Images