US2258665A - Magneto - Google Patents

Description

Oct. 14, 1941. VQGEL 2,258,665

MAGNETO Filed June 14, 1939 INVENTOR EDWAR 0 A.VOGEL ATTORNE Patented Oct. 14,

MAGNETO.

Edward A. Vogel, Beloit, Wis., assignor to Fairbanks, Morse & 00., Chicago, 111,, a corporation of Illinois Application June 14, 1939, Serial; Np. 279,009

3 Claims.

This invention relates to magnetos for supplying ignition current to internal combustion engines, and more particularly to improvements in high tension magnetos embodying distributors of the so-called jump-spark variety wherein ignition current produced by the magneto is caused to span an air gap between a rotating distributor member and its associated terminals.

An object of the invention is attained in the provision of a compartment or chamber for the distributor mechanism which is separated and sealed from the magneto and breaker parts, and in the provision of improved means for ventilating and producing a positive flow of air through the distributor chamber. The purpose of these provisions is to prevent ozone formed by the spark discharge from coming into contact with the breaker points and other operating parts. As is well known, ozone has a tendency to combine with other elements present and to form compounds that have a corrosive effect on the magneto parts.

Another object is to provide an improved housing which enables the distributor mechanism to be removed as a unit without disturbing other parts of the magneto assembly, a removable end portion of the housing providing the aforesaid distributor chamber which, in assembly, is sealed from other portions of the housing interior. In a structure of this character the provision of a high tension conductor or lead connection between the magneto and distributor, and the avoidance of short circuit and ground paths present a problem, particularly where, as in the present magneto unit, a section of the high tension lead is carried by a removable cover plate. An object of the invention is attained in the provision of a compact assembly having electrical interconnections arranged and insulated in an improved manner so as to preclude short circuits and ground paths.

Other objects and advantages will appear in the following description of a presently preferred embodiment of the invention illustrated in the accompanying drawing in which:

Fig. 1 is a partly sectioned side elevation of the magneto assembly;

Fig. 2 is an end view of the distributor chamber, with the cover plate thereof removed, and

Fig. 3 is a sectional view taken at line 3-3 of Fig. 2.

Referring now by characters of reference to the drawing, the magneto housing comprises a die-cast aluminum body 8, closed at one end by a removable plate 9- formed of Bakelite or other suitable insulating material, the plate 9 serving to carry and enclose the distributor mechanism as will hereinafter appear. The. magneto coil in is mounted. in the. upper portion of the housing I body 8. and the spaced arms of its core structure II project downwardly to the rotor l2 underlying coil In. The rotor shaft I3. is journalled at one end in. an anti-friction bearing assembly [4 mounted. in the. end wall I5 of the housing body 8; Shaft l3 projects through. an opening in the said end wall of the housingv and. carries a suitable. coupling device indicated at I 6. A cork sealing ring I!- held in place by a metal retainer ring l8 serves to exclude dirt and moisture from the housing at the coupling end of; the shaft.

The. opposite. or inner end of the rotor shaft is journalled in an anti-friction bearing assembly [-9, mounted in a removable plate 20 which is rigidly. secured. by screws 2| to, the housing 8. Plate 20 has a boss 22 formed thereon below. the rotor shaft, boss. 22 having a bearing sleeve 23 in which is journalled. the distributor shaft 24. The inner end of the rotorshaft l3 projects through plate 29 and has, a cam 25formed thereon. The cam 25 constitutes an operating memberof the breaker mechanism which, as is well known, serves to interrupt the primary or low- .tension circuit of the magneto coil. The breaker mechanism is not shown since it forms no part of the present invention, but the location of the breaker with respect to the magneto proper and the distributor is of importance, and its general location will be understood from the drawing showing the position of the breaker cam. The distributor shaft 24 is driven by the rotor shaft 13- through gears 26 and 21, keyed to their respective shafts and located at the rotor side of plate 20.

As best appears from Fig. 1, the closure plate 9, formed of insulating material, has an interior wall portion 28 that defines a compartment or chamber 29 which is closed-01f from the remaining space within the housing. Access to the chamber 29 is had through an opening in the face of the plate 9, such opening being normally closed by a removable cover plate 30 of insulating material. The cover plate 39' is detachably secured to the plate 9, and the plate 9 is detachably secured to the housing 8 by means of screws (not shown).

The distributor shaft 24 extends through an opening in wall portion 28 which is formed with a pocket for the reception of a cork or other suitable washer 3i that surrounds, and provides a seal about the shaft, the washer 3| serving to prevent dust and gas or vapor formed in chamber 29 from entering the magneto and breaker compartment of the housing.

Mounted on the end of shaft 24 for rotation therewith is a distributor disc or rotor 32 of Bakelite, the shaft terminating in a stepped end surface which fits a correspondingly shaped recess in the center of the rotor whereby the latter is held in definite angular relationship to the shaft, although removable therefrom. Projecting radially from the periphery of the disc 32 is a terminal finger 39 to which is aflixed a resilient conduotor 34 that leads radially to the axis of the disc. The removable cover 39 carries a springpressed contact element 35 which engages the end of conductor 34, and an embedded conductor 36 leading from contact 35 to an exposed contact terminal 37! projecting inwardly near the upper end of the cover 39. Contact terminal 31 engages the downwardly projecting end of a conductor 38 which is embedded in a thickened wall portion of plate 9. The upper end of conductor 38 provides a contact located within a socket 39 that is adapted to receive the bare end of a heavily insulated conductor 40 leading from the high tension circuit of the magneto coil Ill. The absence of a permanent connection between conductors 38 and 40 permits removal of cover plate 9, and likewise the contacts associated with the closure plate 39 permits that member to be detached from plate 9.

In order to preclude the formation of a shortcircuit or leakage path from the high tension lead 38 to certain ground terminals hereinafter described, the distributor chamber 29 is formed with a partition 4| that isolates the exposed connection between terminal and conductor 38 from other parts of the distributor assembly. The leakage path sought to be avoided is such as may b produced by a film of moisture on the inner surfaces of the distributor chamber, and the provision of a separate or auxiliary chamber 42 for the exposed contact 31 precludes the formation of such leakage path.

The high tension ignition current generated in coil [9 and conducted therefrom to distributor terminal 33 as previously described is transmitted in due order in the form of a spark discharge, to

the distributor terminals 43 and 44 which are adapted to be selectively connected by insulated lead wires 45 and 45 to the spark plugs of an engine. selected herein to illustrate the invention is adapted to serve a two-cylinder, four-cycle engine having crank spacings of 180 degrees, and wherein firings occur at intervals of 180 degrees separated by non-firing intervals of 540 degrees,

the last two measures relating to the angles through which the crank shaft turns during an operating cycle. As is well known, the distributor rotor operates at one-half engine speed and accordingly the terminals 43 and 44 are physically spaced 90 degrees apart. It should be understood that the arrangement herein shown for exemplary purposes is susceptible of modification to adapt the magneto assembly for engines of other types without departing from the spirit and scope of the invention.

By referring to Fig. 2 it will be seen that the spark plug leads 45 and G5 enter the distributor chamber 29 through bosses l! formed on a side wall of the said chamber, and the terminals 43 and 4.4 have arcuate faces 43 which are suitably spaced from the path of rotation of the arcuate end face 49 of distributor terminal 33. When terminal 33 confronts either of the terminals 43 and 44 the high tension current jumps across the space between th terminal faces 49 and 48. The spark created between the aforesaid terminals results in the production of ozone in the distributor chamber and it is highly important to provide effective means for discharging the ozone from the magneto housing and to prevent the ozone from entering the magneto chamber where it can contact the bearings, breaker terminals and other parts of the assembly. It has long been known that ozone has the faculty of combining with nitrogen and other elements present about electrical machines to form corrosive substances that tend to attack and corrode the insulation and metal parts. The improved means of the present invention for ventilating the distributor chamber and providing for the positive expulsion of ozone into the outside atmosphere will be subsequently described.

The distributor is provided with an additional pair of terminals 50 and 5! that extend through wall 28 of the distributor chamber and are respectively spaced diametrically opposite to the terminals 53 and 44. The end faces 52 of the terminals 59 and 5| are spaced from the path of the inner end face 53 of terminal 33 forming spark gaps, Terminals 59 and 5! are connected by a resilient conductor 54, as best appears from Fig. 3, having a continuation 55 arranged to bear upon the inner surface of the metal housing 8. Accordingly, the conductor 54 serves to ground the terminals 59 and 5|. The grounding terminals 59 and 5| serve to dissipate the energy generated in the magneto coil as the distributor rotor terminal 33 travels in its counterclockwise direction from terminal 4 5 to terminal 5|. In the absence of the said grounding terminals the spark plug connected to terminal 45 would produce an undesirably potent ignition spark, and a relatively weaker, although normal spark would be produced by the spark plug connected to terminal 44. Thus, the grounding terminals 50 and 5! serve indirectly to equalize and render uniform the intensity of the ignition sparks, which improves engine operation. It will be noted however that increasing the number of sparks produced within the distributor chamber increases The magneto and distributor assembly the production of ozone and accordingly special provisions are necessary to relieve the house of this deleterious gas.

For the above mentioned purpose the chamber 29 is provided with an air inlet passage 56 that extends longitudinally in the partition wall 28 and opens into chamber 29 at 51, adjacent the center or hub portion of the distributor rotor 32. Chamber 29 is provided with one or more discharge passages 58 located in an outer wall of the chamber, preferably in the plane of the distributor rotor. As a means for effectively ventilating chamber 29 by positively inducting air through passage 56 and expelling air through passage 58, distributor rotor 32 has a plurality of radially extending vanes or blades 59 formed thereon. The vaned rotor 32 operates in the manner of the impeller of a centrifugal blower, creating a forced circulation of air throughthe distributor chamber by drawing outside air into the chamber near the center of the impeller and driving the air centrifugally outwardly through the exit passages 58. It will be noted that ventilating air is admitted into the chamber adjacent the cork sealing Washer 38, and that the air cur rents created by the impeller blade 5B are directed away from the shaft seal. Accordingly, there is.

absolutely no opportunity or tendency for ozone in chamber 29 to filter through the shaft seal int the magneto chamber.

From the foregoing description it will be seen that the high tension lead from coil 10 to the distributor is completely insulated, in part by being embedded in the insulating walls of the cover plates 9 and 30, and that junctions in said lead conductor which enable the facile detachment and replacement of the cover plates are effectively isolated to preclude leakage or ground paths. Thus, the barrier 4| prevents the formation of a leakage path from the exposed junction indicated at 31 along moist or dust-coated inner wall surfaces of the distributor chamber to the ground terminal 50.

Having described my invention with reference to a presently preferred embodiment thereof, it will be understood that various changes and modifications may be made in the magneto unit herein shown Without departing from the spirit and scope of the invention which is defined by the appended claims.

I claim:

1. In combination in a magneto, a metal casing providing a magneto chamber, a distributor housing of insulating material detachably mounted on said casing and including a dividing wall between the magneto and distributor chambers, a discharge terminal mounted for rotation in the distributor chamber, a pair of fixed, relatively spaced terminals mounted on the distributor housing at one side of the axis of rotation of said discharge terminal and adapted for sequential communication therewith, a pair of fixed, relatively spaced grounding terminals mounted on and extending through said dividing wall and arranged for sequential communication with said discharge terminal, and a ground conductor mounted on said dividing wall and located within th magneto chamber, said ground conductor interconnecting said ground terminals and having a yieldable end portion bearing upon an inner surface of said metal casing.

2. In a magneto, an open-ended casing providing a housing for current generating apparatus, an insulating cover removably secured to the open end of said casing, an integral wall structure formed on the inner side of said cover, providing a sealed distributor chamber within the casing, said cover having an external opening for access to the distributor chamber, a removable closure plate for said opening, a sectionalized conductor extending from the current generating apparatus into said distributor chamber 'and comprising a conductor section embedded in said cover and a contiguous section embedded in said closure plate, and means forming an isolated chamber for the joining ends of said conductor sections.

3. In a magneto, an open-ended housing, current generating apparatus in said housing, an insulating cover removably secured to the end of said housing, an integral wall structure on said cover forming a sealed distributor chamber, distributor apparatus in said chamber, an opening in said cover for access to the distributor apparatus, a removable closure plate for said opening, a sectionalized conductor for transmitting current from the generating apparatus into the dis tributor apparatus and comprising a conductor section embedded in the cover and a conductor section embedded in said closure plate, said sections having contiguous end portions projecting into the distributor chamber, and a partition in the distributor chamber for isolating the projecting ends of said conductor sections from the distributor apparatus.

EDWARD A. VOGEL.

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