US3438362A - Ignition system - Google Patents

Description

April 15, 1969 W. D. CLYBORNE ETAL IGNITION SYSTEM Original Filed Jan 4, 1966 INVENTOR. (J/Lu: D. Grace/w! BY Ham 5. C2 YJOEN! Maw Arron/ K United States Patent US. Cl. 123-1465 8 Claims ABSTRACT OF THE DISCLOSURE Electro-optical circuit interrupter mechanism for use with the distributor of an internal combustion engine to replace the customary distributor points as the means for converting the steady-state D.C. battery current into a pulsating D.C. current enabling the primary winding of the ignition transformer to be energized thereby. The interrupter mechanism includes a light source located exteriorly of the distributor casing, a ph-otoresponsive sensor located within the casing, a light pipe through which light is conducted from the source to the sensor, an apertureequipped interrupter disc rotatably driven by the distributor shaft and located between the sensor and light pipe to cyclically interrupt the transmission of light therebetween and a switching circuit responsive to the sensor for cyclically interrupting the primary circuit of the ignition transformer in correspondence with changes in the condition of the sensor.

This application is a continuation of Ser. No. 518,576, filed Jan. 4, 1966.

This invention relates to an ignition system adapted for use with internal combustion engines and the like; and it relates more particularly to that portion of such ignition system through which the customarily provided, steadystate D.C. battery current is converted into a pulsating D.C. current to enable a high voltage to be developed from the low battery voltage in a step-up transformer.

Conversion of the low value, direct current voltage usually provided by a six or twelve volt storage battery, to the much higher value voltage necessary to create an arc across the spaced terminals of each spark plug or sparking device used in an internal combustion engine has long been accomplished by means of mechanical breaker points interposed in the primary circuit of a step-up transformer to repetitively complete and interrupt such circuit and thereby effectively change the steady-state battery current supplied thereto into a pulsating current effective to energize the secondary winding of the transformer. conventionally, the breaker points are located within the distributor casing of such engine which enables a single engine-driven shaft to angularly displace the rotor member of the distributor (which rotor member successively connects in turn each of the various sparking devices to the secondary winding of the transformer) and to open and close the breaker points in timed relation therewith.

It is well known that such breaker points which mechanically open and close the circuit therethrough are subject to considerable wear and fatigue and, therefore, require frequent cleaning, adjusting and replacement. Moreover, since at least one of the breaker points is a movable component, the mechanical inertia inherent in the reciprocatory displacement thereof causes considerable inaccuracy in the timing of the ignition system, especially at higher engine speeds. Additionally, there is a bounce or rebound factor involved in the movable point contact closing against the stationary contact which also interferes adversely with high quality engine performance especially at higher speeds.

As a consequence of these characteristic difliculties and limitations inherent in mechanical breaker points, efforts have been made to eliminate the same, and an exemplary instance thereof is Berdine et a1. Patent No. 2,984,695 wherein the mechanical breaker points can be selectively replaced by an electro-optical system in which a beam of light is directed toward a photoelectric cell and the light beam repetitively interrupted to cyclically and alternately energize and de-energize the photoelectric cell, which alternate conditions thereof are used to complete and interrupt the circuit through the primary winding of a step-up transformer just as in the case of the mechanical breaker points.

It has been found that the electro-optical system disclosed in such patent has not been wholly satisfactory for commercial use because of a somewhat limited period of dependable accuracy and general reliability. The present invention constitutes an improved ignition system of the general type described in such Patent No. 2,984,695; and in this respect, has a significantly greater life expectancy throughout which reliable and accurate performance is attained. Further, the system of the present invention affords rapid and accurate triggering of the ignition system; it has an exceedingly fast response time-in the nanosecond range (i.e., 10- second); it permits the spark gap of each engine spark plug or sparking device to be much greater than in the past with the result that a longer, flatter and hotter spark is provided which enables engine fuel to be burned more efficiently and thereby results in the development of greater engine horsepower; and it affords greater accuracy of control over the duration of each sparking period throughout the: entire operating range of the engine.

An ignition system comprising the present invention includes a distributor which may be substantially conventional except that the usual mechanical breaker points are completely omitted and an electro-optical circuit interrupter mechanism substituted therefor. Such electro-optical system includes a source of radiant energy which may be in the form of a light or electric lamp located exteriorly of the distributor casing, a sensor located within the casing and responsive to the receipt of energy from such source, and an energy conductor extending through the casing and terminating at one end adjacent the energy source and terminating adjacent its other end in spaced relation with the sensor. Also mounted within the distributor casing intermediate the sensor and adjacent end of the energy conductor is an interrupter rotated by the enginedriven distributor shaft and operative alternately and repetitively to permit and obstruct the transmission of radiant energy from the conductor thereof to the sensor. Responsive to the sensor and controlled thereby is a switching circuit coordinately operative to complete and interrupt cyclically the primary circuit of the ignition transformer in accordance with the alternate conditions of the sensor.

An embodiment of the invention is illustrated in the accompanying drawing in which:

FIGURE 1 is a schematic view of an engine ignition system embodying the present invention; and

FIGURE 2 is a vertical sectional view of a distributor forming a part of such system and made in accordance with the present invention.

The ignition system shown in the drawing is suitable for use with an internal combustion engine as, for example, the usual gasoline engine employed as the power plant in automobiles and other land vehicles, in marine and airborne vehicles, etc. The system to a great extent is conventional and includes the customary source of direct current power such as the storage battery 10 shown in FIGURE 1. As is well known, such battery ordinarily defines a six or twelve volt D.C. source, but as respects the present invention, any voltage value can be provided.

The system further includes a distributor, generally shown in FIGURE 2 and denoted in its entirety with the numeral 11. The distributor itself is in many respects conventional and includes a casing 12 having a removable cap 13. The cap is provided with a high voltage terminal 14 connected by a conductor 15 to one side of the secondary winding 16 of a transformer 17. As in the usual case, the transformer 17 shown is an auto-transformer and, accordingly, the other end of the secondary winding 16 is grounded in common with one end of the primary Winding 18.

The distributor 11 is also provided with a plurality of angularly spaced contacts 19, as shown in FIGURE 2, adapted to be connected by a plurality of respectively associated conductors 20 (only one of which is shown) to conventional sparking devices or spark plugs 21. In FIGURE 1, only one such contact 19, conductor 20 and sparking device 21 are shownit being understood that there will be a separate contact, conductor and sparking device for each cylinder of the engine, usually numbering 4, 6 or 8 in the automotive environment. Since the contacts are identical, each is identified in FIGURE 2 with the numeral 19, and as shown in FIGURE 1, one side of each sparking device 21 is grounded, usually through the engine and vehicle chassis.

The casing 12 is provided centrally along the bottom closure wall thereof with a hub or collar 22 that provides a mounting for a sleeve bearing 23. Extending upwardly through the bearing 23 is a hollow tubular shaft 24 co axially and rotatably passing therethrough a distributor shaft 25 adapted to be driven by the engine through a suitable gear train (not shown). Adjacent its upper end, the distributor shaft 25 has a rotor 26 mounted thereon which rotates therewith, and relative angular displacements between the shaft and rotor are prevented in any suitable manner, as by means of flattened contiguous surface areas respectively provided by the shaft and rotor and which also serve as a polarizing means to cause the rotor to be mounted upon the shaft in a predetermined angular position with respect thereto. This latter feature is necessary since the rotor is removable and the timing of the engine would be destroyed if the precise angular relationship between the shaft and rotor were not maintained. As in the usual manner, the rotor 26 is formed of an insulated material but is equipped with a conductor or conductive strip 27, one end of which is in continuous engagement with the high voltage terminal 14 and the other end of which is adapted to selectively engage the successive contacts 19 as the rotor is angularly displaced by the shaft 25.

Located within the casing 12 is a timing plate 28 equipped with a hub or depending collar 29 circumjacent the hollow shaft 24 and pinned or otherwise secured thereto. The timing plate 28 is adapted to be angularly adjusted with respect to the axis of rotation of the distributor shaft 25 for the purpose of advancing the spark or time of spark occurrence as engine speed increases. Usually, such adjustment is accomplished automatically, as by connection of the plate 28 to an arm or lever 30 that extends through the casing 12 and into operative association with a conventional vacuum motor 31 adapted to be connected to the intake manifold of the associated engine.

Secured to the plate 28 is a mounting block 32 formed of a good heat conducting material such as aluminum, and the mounting block may be fixedly secured to the plate in any suitable manner, such as by means of the cap screws shown. The mounting block 32 is provided with a recess 33 therein into which depends the terminals of a sensor 34 removably secured to the mounting block by cap screws or other appropriate fastener structure. The sensor 34 is characterized by being responsive to the receipt thereby of radiant energy; and in the particular form shown, the sensor is responsive to radiant energy in the visible spectrum, such as that provided by a conventional incandescent lamp.

Also, fixedly secured to the plate 28 by cap screws or other suitable means is a support 35 that may be formed of aluminum for heat dissipating purposes, and the support 35 extends upwardly from the plate 28 and is provided adjacent its upper end with a laterally extending collar 36 that projects through an opening provided therefor in the side Wall of the casing 12. At its outer end exteriorly of the casing, the collar 36 is equipped with threads adapted to receive thereon a socket 37 for an incandescent lamp 38. The lamp 38 may be a conventional light bulb having, for example, a rating of 6 to 12 volts; and, in the usual manner, one terminal of the lamp 38 is grounded through the casing thereof and socket 37, and its other terminal is connected to a conductor 39.

The collar 36 of the support 35 is hollow, and mounted within the collar is a radiant energy conductor 40 in the form of an elongated rod terminating at one end adjacent the bulb 38 and terminating at its other end a spaced distance from the sensor 34. The rod 40 is adapted to trans- Init radiant energy from the source thereof defined by the lamp 38, and in the form shown, the conductor transmits light therealong and may be a bar of transparent plastic sold under the trademark Lucite having all of the longitudinal surfaces thereof rounded since light energy has a tendency to escape at any sharp edge thereof. The conductor 40 is fixedly secured to the support 35 by a releasable clamp 41 which permits adjustment of the axial position of the rod for alignment of the inner end thereof with the aperture or photosensitive surface of the sensor 34. The conductor 40 has a concave outer end portion 42 conforming generally to the configuration of the bulb 38 so as to partially nest the same therein, and the spring component of the socket 37 tends to resiliently bias the bulb against such arcuate end of the conductor. At its inner end, the conductor 40 is turned downwardly and traverses an arc of approximately to effect alignment of the inner end thereof with the sensor 34.

Interposed between the sensor 34 and the adjacent and switch 48. The resistance 47 simply reduces the batalong alternate areas respectively adapted to pass or transmit energy therethrough and to obstruct or prevent the transmission of energy from the conductor to the sensor. In the form shown, the interrupter 43 is a circular disc formed of an opaque material such as aluminum, and provided at angularly spaced distances therealong with a plurality of apertures 44. Thus, each aperture 44 defines such energy-transmitting area and the interposed portions of the opaque disc 43 define the energy-obstructing areas. The disc 43 is equipped with a collar 45 circumjacent the distributor shaft 25 and it is secured thereto by a key and keyway composition 46 which causes the interrupter to rotate in enforced synchronism with the shaft. Evidently, there will be an aperture 44 for each contact 19 and, therefore, for each sparking device 21 of the associated engine.

Referring to FIGURE 1, the lamp 38 is connected to the battery 10 through a voltage dropping resistance 47 and switch 48. The resistance 47 simply reduces the battery potential to that suitable for operation of the lamp 38, and the switch 48 may comprise a part of the ignition switch for the associated engine. Not only is the switch operative to interrupt the circuit to the light source 38, but it also interrupts the circuit to the entire ignition system illustrated. The point of connection of the resistance 47 with the switch 48 is denoted for identification with the numeral 49, and connected thereto is one side of a resistance 52 serving as a current limiter for the sensor 34.

The sensor 34 is a solid state device, and in the form shown, is a photosensitive NPN transistor having its emitter and collector electrodes connected externally in the circuit. In this respect, the emitter electrode is connected to a circuit 53 and supplies input signals thereto, and the collector electrode is connected to the resistance 52 and, therethrough, to the power source 10. The photosensitive transistor shown functions as a light sensitive switch for the circuit 53, and it may be any one of a number of commercially available devices, as, for example, an FPM-100 phototransistor supplied by Fairchild Semiconductor of San Rafael, Calif.

The signal developed by the transistor 34 is delivered to the circuit 53 which is a switching or chopping type circuit operative in effect to make and break the energizing circuit of the transformer 17 in accordance with the condition of the transistor 34. That is to say, whether such energizing circuit is actually completed or interrupted will depend upon the specific circuit 53 employed, but in any event the circuit 53 is operative to effect energization and de-energization of the transformer in accordance with the state of the sensor as it is switched between the energized or current conductive and de-energized or nonconductive conditions thereof. Any one of a number of circuits may be employed and a typical example is an amplifier circuit known as a Transistorized Capacitor Discharge Ignition System which is described under such title in the June 1965 edition of Popular Electronics, page 43. Such circuit is also illustrated in detail along with component values in FIGURE 3 of this article, and a commercial embodiment of the circuit can be obtained from various sources such as the Sydmur Company of Brooklyn, N.Y.

Operation of an engine with which the ignition system is associated is conventional in all respects as concerns the general function of the engine and, accordingly, when the engine is energized the distributor shaft 25 will be rotated and the rotor 26 and interrupter 43 will be rotated therewith. As the rotor is driven by the shaft 25, the successive angularly spaced contact 19 will be connected in turn one-by-one with the high voltage terminal 14, whereupon the voltage cyclically present thereat will be applied to the associated sparking device 21 to cause the usual arcto occur across the spaced apart terminals thereof. Consequently, the compressed fuel within the associated cylinder will be ignited by such spark or arc in the usual manner.

There is an aperture or opening 44 in the interrupter 43 for each of the engine cylinders and such openings may have various configurations and, for example, can be circular, a rectangular slot, fan-shaped, etc. Irrespective of the particular shape of such openings, in the usual case the edges thereof will be relatively sharp so as to effect a rapid transition between the light-transmitting and light-obstructing conditions as the interrupter 43 rotates. In any event the apertures 44 are relatively small, and in the illustration of FIGURE 2, it will be noted that the apertures are slightly smaller in radial extent than the diameter of the light conductor 40 which, in a typical installation, has a diameter of about 7 of an inch. In the embodiment of the invention illustrated, the terminal surface of the light conductor 40 is substantially normal to a vertical axis through the light receiving surface of the sensor 34. Deviation from this condition of normalcy is tolerable, but depending upon the amount of light developed by the lamp 38, an angle of incidence of about or less is most desirable.

The sensor or photosensitive transistor 34 is essentially reversely biased with substantially no light incident on the photosensitive element thereof and, accordingly, there will be substantially no flow of current through the sensor during such dark or no-light condition. This condition of the sensor will obtain Whenever a space between adjacent apertures 44 is in substantial alignment with the sensor and adjacent end of the light conductor 40. Accordingly, substantially no input signal will be delivered to the circuit 53 during such period and, as a result, the primary circuit of the transformer 17 will be interrupted at this time. This condition is equivalent to that present in a conventional engine distributor and ignition system when the mechanical points thereof are separated.

On the other hand, each time an aperture 44 is displaced into alignment with the sensor 34, the sensor will be energized by the light then incidentthereon and current will flow through the load resistance 52 whereupon an input signal will be transmitted to the circuit 53 causing the same to close the primary circuit through the transformer 17. This condition is equivalent to that present in a conventional engine distributor and ignition system when the mechanical points thereof are closed. With the transformer energized, a secondary voltage will be induced therein effective to cause one of the sparking devices 21 to be energized.

As the distributor shaft 25 drivingly rotates the interrupter 43, the angularly spaced apertures 44 provided thereby are moved successively into alignment with the light receiving surface of the sensor 34 and the adjacent end of the light conductor 40. Since the lamp 38 is energized continuously, the light developed thereat is transmitted to and will be continuously present at the inner end of the conductor 40, which inner end is in alignment with the sensor 34. As explained heretofore, the rotor 26 and interrupter 43 are both fixedly mounted upon the distributor shaft 25 so as to rotate simultaneously therewith. Further, the various apertures 44 of the interrupter 43 are located and positioned with respect to the conductor 27 and the rotor 26, and also with respect to the location of the various terminals 19, so that an aperture 44 is substantially in alignment with the sensor 34- whenever the conductive strip 27 is in substantial engagement with a contact 19. As a consequence of such interrelationship of the sensor 34, light conductor 40 and apertures 44 with the terminals 19 and conductive strip 27, a secondary voltage is developed by the transformer 17 for transmission to a sparking device 21 each time the conductive strip 27 is in electrical engagement with a contact 19.

The precise time relationship, however, between the engagement of the conductive strip 27 with a terminal 19 and the location of the sensor 34 with respect to an aperture 44 will depend upon the engine speed and whether the engine is accelerating or decelerating. In this respect, the timing plate 28 will be advanced or retarded automatically by the rod 30 and vacuum motor 31 in a completely conventional manner in accordance with the operating condition of the engine and, more particularly, the timing will be advanced slightly as the engine speed is increased. Thus, whenever the timing plate 28 is angularly displaced with respect to the axis of the shaft 25, the sensor 34 will be displaced therewith and the light conductor 40 will be similarly displaced therewith since both the sensor and light conductor are fixedly carried by the plate 28 through the mounting block 32 and support 35. Consequently, each arcing of a sparking device 21 can be made to occur more quickly if the plate 28 is displaced in a direction opposite to the direction of rotation of the interrupter 43, and it can be made to occur later if the plate is angularly displaced in the same direction as the direction of rotation of the interrupter 43.

The switch 48 interrupts the circuit to the light source 38, the sensor 34 and amplifier 53, and it may comprise a component of the main ignition switch, as described hereinbefore. Since the light source 38 is located exteriorly of the distributor casing 12, the heat developed by such source whenever it is energized is readily dissipated and does not, therefore, influence the operating characteristics of the sensor 34. Accordingly, the source 38 in association with the light conductor 40 may be described as providing a cold light, and not only does it remove the heat source from proximity to the sensor, but it results in the light having a very good reliability over a long life and also results in sharper transitions between the on-off conditions of the transistor because peak or maximum light is always available. As respects the dissipation of heat, the mounting block 32 and support 35 may both be formed of aluminum, as indicated, for rapid dissipation of heat 'from the area of the sensor. Although indicated hereinbefore that the interrupter 43 also may be formed of aluminum, it is contemplated that the rotor 26 and interrupter can be made integral; and in such case an opaque insulating material would be used for fabrication thereof.

The extreme accuracy in voltage development resulting from the electro-optical interrupter system of this invention permits the gap defined by each of the sparking devices 21 to be greater than in conventional systems which results in more efiicient burning of the engine fuel and the development of greater engine horsepower. Further, such accuracy permits the use of a transformer 17 that develops a higher secondary voltage than transformers otherwise employed which results in a hotter spark, and use of such a higher voltage transformer is enabled because the on-ofI control of the ignition spark is consistently maintained over the entire operating range of the engine.

While in the foregoing specification an embodiment of the invention has been described in considerable detail for purposes of making a complete disclosure thereof, it will be apparent to those skilled in the art that numerous changes may be made in such details without departing from the spirit and principles of the invention.

What is claimed is:

1. In an ignition system for internal combustion engines and the like and which ignition system includes a distributor having a casing and a shaft extending thereinto which is adapted to be rotatably driven by such engine, an interrupter system for developing a pulsating current effective to energize the ignition system and comprising a sensor mounted within said casing and being responsive to the receipt of radiant energy, a source of radiant energy located remotely from said sensor, a ngitudinally extending energy conductor for transmitting such radiant energy from one end to the other and at one such end terminating adjacent said source of energy and at its other end terminating a spaced distance from said sensor, a rotatable interrupter located within said casing and being interposed between said sensor and adjacent end of said conductor and being provided with a group of angularly spaced energy-transmitting areas and a group of angularly spaced energy-obstructing areas alternately related with said energy-transmitting areas, said group of energy-transmitting areas being effective to permit the transmission of radiant energy from said conductor to said sensor and said group of energy-obstructing areas being effective to prevent such transmission of radiant energy, said interrupter being rotatably driven by said shaft to successively advance in turn each of said energytransmitting areas into alignment with said sensor and adjacent end of said conductor in timed relation with the rotational movement of said shaft, a timing plate located within said casing and being displaceable to alter the timing of the distributor and ignition system, said sensor and said conductor being supported by said plate so as to move therewith during any such displacements thereof, and a switching circuit responsive to said sensor and being operative to selectively energize and de-energize the ignition system in accordance with the condition of said sensor, said source of radiant energy being a light source comprising an electrical lamp, said sensor being a photosensitive device, and said energy conductor being a light conductor having a contoured end portion adjacent said lamp and generally conformed thereto and being in substantially contiguous relation therewith.

2. In an ignition system for internal combustion engines and the like and which ignition system includes a distributor having a casing and a shaft extending thereinto which is adapted to be rotatably driven by such engine, an interrupter system for developing a pulsating current effective to energize the ignition system and comprising a sensor mounted within said casing and being responsive to the receipt of radiant energy, a source of radiant energy located remotely from said sensor, a lon gitudinally extending energy conductor for transmitting such radiant energy from one end to the other and at one such end terminating adjacent said source of energy and at its other end terminating a spaced distance from said sensor, a rotatable interrupter located within said casing and being interposed between said sensor and adjacent end of said conductor and being provided with a group of angularly spaced energy-transmitting areas and a group of angularly spaced energy-obstructing areas alternately related with said energy-transmitting areas, said group of energy-transmitting areas being effective to permit the transmission of radiant energy from said condoctor to said sensor and said group of energy-obstructing areas being effective to prevent such transmission of radiant energy, said interrupter being rotatably driven by said shaft to successively advance in turn each of said energy-transmitting areas into alignment with said sensor and adjacent end of said conductor in timed relation with the rotational movement of said shaft, a timing plate located within said casing and being displaceable to alter the timing of the distributor and ignition system, said sensor and said conductor being supported by said plate so as to move therewith during any such displacements thereof, and a switching circuit responsive to said sensor and being operative to selectively energize and de-energize the ignition system in accordance with the condition of said sensor, said source of radiant energy being located exteriorly of said casing, and said energy conductor extending through said casing so as to terminate at one end adjacent said source of energy and at its other end a spaced distance from said sensor.

3. The ignition system according to claim 2 in which said source of radiant energy is a light source, in which said sensor is a photosensitive device, in which said energy conductor is a light conductor, and in which said rotatable interrupter comprises a substantially opaque disc having a plurality of apertures therein defining the aforesaid energy-transrnitting areas.

4. The ignition system according to claim 3 in which said light source comprises an electric lamp, and in which said energy conductor has a contoured end portion adjacent said lamp and generally conforming thereto and being in substantially contiguous relation therewith.

5. The ignition system according to claim 3 and further including a heat-conductive mounting block secured to said plate and providing a support for said sensor, said mounting block being effective to transmit heat between said sensor and plate so as to dissipate heat representing temperature excesses tending to appear at said sensor.

6. The ignition system according to claim 5 and further including a support block secured to said plate and providing a mounting for said conductor, said support block having a portion thereof extending outwardly through said casing to dissipate heat to the ambient environment thereabo-ut.

7. In an ignition system for internal combustion engines and the like including a distributor having a casing and a shaft extending thereinto adapted to be rotatably driven by such engine and an interrupter system operative to develop a pulsating current effective to energize the ignition system and comprising a photosensitive sensor mounted within said casing and being responsive to the receipt of radiant energy, a light source providing a source of radiant energy, a rotatable interrupter located within said casing intermediate said sensor and light source and being provided with a group of angularly spaced energytr ansmitting areas effective to permit transmission of radlant energy from said light source to said sensor and further being provided with a group of angularly spaced energy-obstructing areas alternately related with said energy-transmitting areas and being effective to prevent such transmission of radiant energy, said interrupter being rotatably driven by said shaft to successively advance in turn each of said energy-transmitting areas into alignment with said sensor and light source in timed relation with the rotational movement of said shaft, a timing plate located within said casing and being displaceable to alter the timing of the distributor and ignition system and said sensor and light source being supported by said plate so as to move therewith during any such displacements thereof, and a switching circuit responsive to said sensor and being operative to selectively energize and de-energize the ignition system in accordance with the condition of said sensor, the improvement in which said light source is located remotely from said sensor and comprising a longitudinally extending light conductor interposed between said sensor and light source for transmitting radiant energy from one to the other and being substantially continuous from end to end thereof, and support structure secured to said plate and providing a mounting for said light source and energy conductor the latter of which terminates at one end in light-receiving proximity with said light source and at its other end a spaced distance from said sensor to accommodate the interposition of said interrupter therebetween.

8. The ignition system of claim 7 in which said rotat- UNITED STATES PATENTS 2,169,818 8/1939 Scott.

2,337,535 12/1943 Acs 31712 2,725,487 11/1955 Butler et a1. 250227 2,984,695 5/1961 Berdine et. a1.

3,163,700 12/1964 Williamson 350-9t 3,235,742 2/ 1966 Peters 250-233 LAURENCE M. GOODRIDGE, Primary Elraminer.

US. Cl. X.R. 123-448

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