US2479005A - Ignition apparatus - Google Patents

Description

Aug. 16,1949. I R. FRE 2,479,005

IGNITION APPARATUS Filed May 17, 1943 2 Shee'ts-Sheet 1 /Z If F G, 2

INVENTORS (11MB l1. Md,

BY Km 7%. l

ATTORNEY J. R. FREI ETAL IGNITION APPARATUS Aug. 16, 1949.

2 Sheets- -Sheet 2 Filed May 17, 1943 FIG. 3

' 5 50a b 0c FIG.- 6

INVENTORS A M IF. 17%)? Ma,

FIG. 5

Patented Aug. 16, 1949 2,479,005 IGNITION APPARATUS Jakob R. Frei, Sidney, and Rolland M. may, Bainbridge, N. Y., assignors to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application May 17, 1943; Serial No. 487,372 '14 Claims. (01. 171-209) This invention relates to ignition means 'for internal combustion engines and more particularly to apparatus adapted for generating and distributing electrical current.

One of the objects of the present invention is to provide a novel magneto-distributor unit adapted for use in the ignition system of an internal combustion engine wherein the current is generated and distributed at a relatively low volt age.

Another object of the invention is to provide apparatus of the above character wherein the current generating and distributing portions are operatively associated with each other in a novel manner to facilitate construction, assembly, inspection and repair.

Still another object is to provide a novel magneto-distributor for an ignition system embodying a novel source of booster current for facilitating the starting of an engine. I

A further object is to provide novel distributor means for low tension electrical current in the ignition system of an internal combustionengine.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a dinnition of the limits of the invention, reference for this latter purpose being primarily had to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a side elevation, partly in section and with parts broken away, showing One form of magneto-distributor unit embodying the features of the present invention;

Fig. 2 is a top view, with parts broken away and partly in section, of said magneto-distributor Unit;

Fig. 3 is an end view of said unit, with parts thereof in section, the section being taken substantially on line 3-3 of Fig 1;

Fig. 4 is a detail view, partly in section and with parts broken away, the view being taken substantially on line 4-4 of Fig. 1;

Fig. 5 is a diagrammatic view of an ignition system wherein a unit of the character illustrated in Figs. 1 to 4 may be employed; and,

Fig. 6 is a detail diagrammatic view showing a modified form of distributor contact which may be used.

A single embodiment of the invention is illustrated in the drawings, by way of example, in the form of a combined magneto-generator and distributor for use in the ignition system of a 9-cylinder engine whereby current is generated and distributed at a relatively low voltage to transformer coils located near and operatively connected to the spark plugs of the engine. In the form shown, the novel magneto-distributor unit is housed in a casing comprising a main casing member In of U shaped section and a cover H therefor secured in position by screws l2 or other suitable means. The open ends of casing member H! are closed by suitable end plates [3 and '14 secured in position by any suitable means, such as set screws Na and Ma, respectively. End plate l3 has a plurality of slotted ears (Fig. 3) formed integrally therewith whereby the entire unit may be operatively secured to an engine for angular adjustment in a manner well understood in" the art.

The current generating means embodied in the apparatus of the present invention may be constitute'd by any of several suitable designs and, in the form shown, comprises a 4-pole magnetic rotor 16 which includes a permanent magnet l1 and pole shoes l9, is carried by a shaft 20. The latter is journalled in a suitable bearing mounted in end plate I3 and a roller bearing 2| mounted in a partition 22 formed integrally with casing member ID. The Outer end of rotor shaft has 'a pinion 2'3 thereon adapted to mesh with a member of the engine for driving the rotor. The other or inner end of shaft 20 has a gear 24 mounted thereon for rotation therewith, the purpose of which will hereinafter appear.

Rotor l6 cooperates during its rotation with a pair of laminated-stator poles 25 in a manner well understood in the art to generate electrical current in the winding of a coil 26 wound on a laminated metal core 21. y The endsof core 21 are secured to' the upper ends of stator poles '25, which are preferably cast into the walls of casing member H! and are thus firmly held in position. A keeper 28 of laminated metal may also be cast into the lower wall of easing member I U for magnetically joining the two inactive poles of the rotor while the other poles are cooperating with stator poles 25, 2'5.

Novel current distributing and circuit breaker means are provided by the present invention and said means are associated with the current generatingmeam above described in a novel manner whereby the parts" may be readily and easily constructed and assembled 'in'su'ch a manner as to which are formed integrally with or are otherwise suitably secured to said cover. These supports are provided with suitable low friction bearings.

24 when cover II is secured in position. Gear l eafiied thereon which is adapted tomeshwith gear 4 the above-mentioned passages in block 43 for receivin wire conductors 41 that are suitably attached and electrically connected to brushes 44 and 45. The attachment of wires 41 to the brushes may be effected by molding the ends of the wires in the brushes during manufacture of the latter. Flexible wire conductors H are secured, such as by means of solder, to strip 46, thereby electrically connecting the two brushes 44 and 45 to each other. For a purpose to appear hereafter, said brushes are yieldably pressed outwardly by coil springs 48 interposed between 34 is preferably drivably connected to 'shaft:33; p

by adjustable coupling means 35 for timing purposes, i. e., for efiecting small angular adjust- Y ments of shaft 33 relative to rotor shaft 20. Said coupling means, as illustrated in the drawings, comprises a set of ratchet teeth on the hub of gear 34, an oppositely facing set of ratchet teeth onan'annular shoulder formed on shaft 33,-one off said sletshaving one less teeth than'the-other setfand an intermediate ring loosely mounted on theshaft with ratchet teeth on both faces thereof for meshing with the first-named sets of teeth. The two sets-of ratchet teeth are so formed that one set provides a positive drive in one direction whil'e'the other set provides a positive drive in the other direction. Since the above-described coupling means is old per se, the same being shown in Spengler U. S. Patent No. 2,266,283, it is believed to be unnecessary to illustrate and describe the same in more detail. The ratchet teeth of the coupling 35 are normall held inmesh for drivably connecting shaft 33 and gear 34 bymeans of a bolt 36 which extends through hollow='shaft33'and has ahead 31- adapted to engage the outer face of gear 34. Shaft 33 and head 31' of'the bolt haveinterlocking portions, to hold the sameagainst" relative angular movement. The other end of bolt 36 is externally threaded for receivin a nut 38 which serves to hold the shaft and gear assembly in-assembled relation. When nut 38. is loosened sufiiciently, the ratchetteeth of coupling 35 are yieldably held in engagement'by a coil'spring 39 so that an angular adjustment of, shaft 33 relative to gear 34 and, hence, rotor shaft 20, may be made in a manner well understood in the art and fully described in Spengler U. S. Patent No.. 2,266,283. Since the adjustable coupling means per se do not constitute'a part of the-present invention, it is not believed that a further detail description of the structure and operation thereof is necessary. Novel means 'areprovided in association with shaft 33 for distributing low voltage current generated in coil'26, said means being mounted between brackets 29 and 30 and comprising a rotating finger;49 keyed on the centralportion'of shaft 33 and a stationary contact carrying block 4| fixed to bracket 30 by any suitable means, such as screws 42. Finger 40, as shown, comprises a molded block 43 of insulating material havinga current pick-up brush 44 and a distributing brush 45 mounted thereon in a novel manner. Block 43 has two axially-extending, radially-spaced passages for slidably receiving said brushes, which may be made of carbon or other suitable conducting material. Molded into block 43' and extending across said passages near one face of finger! is a metallic conducting strip 46. The latter has openings which coincide with the ends of the brushes and insert 46. The out-- ward movement of the brushes is limited by the extended length of'wires 41. The parts of the distributor means are accessible for inspection and repair through openings in the sides of easing member 10, said openings being covered by removable plates l0.

Brushes 44 and 45 of rotatable finger 40 engage a contact ring 49 and a plurality of circularly arranged arcute contacts 50, respectively, which constitute parts of the stationary distributor member 4|. Said ring andcontacts are preferably molded in the face of a block 5| of insulating material and are connected to terminals 52 and 53, respectively, which extend through block 5| to the opposite face thereof. A single supply terminal 52 is connected to ring 49 for the attachment of a lead from one or more sources of electrical current, whereas each of the contacts has a terminal 53 for connection with an outgoing cable 54. Current thuspasses from the source, such as coil 25, throughring 49 to brush 44' and thence through conductors 41, 46, 41 and brush 45 to one of the contacts 56 which is operatively connected with. a transformer to supply energy to a spark plug of the engine in a manner to be hereinafter described.

In the construction of distributor block 4|, two concentric rings are embedded in the face of the molded insulator 5L One of these rings is thereafter cut, such as by means of a circular saw, along radial lines, as shown in Fig. 4, to divide the same into a plurality of segmental contacts 50, onefor each cylinder of the engine. These contacts are preferably connected through terminals 53 and leads 54 to the terminals in the socket portion 55 of a detachable connector, such as a.Cannon plug. The connecting leads 56 from the plug portion 5611 (Fig. 5) of the detachable connector may extend through a suitable radio-shielding harness to the spark plugs 5101' the engine, that is, to the primary windings 58 of individual transformers 59 which have the secondary windings 60 thereof connected to the sparkplugs in the case of a low tension distribution system.

. 0n the end of shaft 33 adjacent end plate l4, there is provided a circuit breaker cam 6| which is of the so-called compensated type when the apparatus is used on radial engines wherein properly timed sparks do not occur at equal intervals, in which event the distributor contacts 5|] are preferably of unequal lengths for purposes of compensation also. The cam, as shown, has a lobe for each cylinder of the engine and is adapted to operatea main circuit breaker 62 (Fig. 3) which is adjustably mounted on the face of bracket 30 opposite distributor block 4|, whereby :the same may be readily inspected or adjusted by removing end plate l4. This circuit breaker may be of any suitable known construction, the one illustrated being of the type shown in Shoemaker et al. Patent No. 1,866,492 and hence adetailed description thereof is believed to be unnecessary.

Circuit breaker 62 has one terminal or contact thereof grounded through the casing and the other terminal or contact connected to terminal 52 of distributor ring 49 by lead 63,, and to one terminal of a condenser 64 by means of a lead 65. Condenser 64., which has the other terminal thereof grounded and thus connected across the contacts of circuit breaker 62, is preferably supported in the hollow :of cover H by means of a bracket 6-! that is in turn removably secured to said cover by screws 68. Terminal 52 is also connected b a lead 65 to the output side of coil 26, thereby connecting said coil to the ungrounded side of circuit breaker 62.

For the purpose of rendering the apparatus inoperative, i. e., incapable of furnishing electrical energy to the spark plugs, the normally ungrounded end of coil 25 may be connected to ground through a suitable ignition switch 69 :(Fig. 5). In the embodiment shown, a ground connection is made through a lead 1-0 connected to terminal 52, a detachable plug-in connector H (Fig. 2) and a lead 12 to ignition switch .69.. The socket portion of said plug in connector is preferably removably mounted in cover I I andthe plug portion of the connector is removably secured. to said socket portion, as illustrated in Fig. 2.

In the operation of the apparatus thus far .described, rotor I6 is driven by the engine through splined member 23 toinduce alternating currents in coil 26. When the contacts of circuit breaker 52 are in closed position, this current flows along the path of least resistance, 1. e., across said contacts to :ground. Each time the current in coil 26 approaches its peak value, the contacts of circuit breaker 62 are opened by cam 6|, whereupon a surge of current flows through terminal 52 to distributor ring '49 and thence through brushes 4-4 and 45, a distributor contact 50, a lead 54, 55 and the primary winding .58 of an ignition coil 59,. This sudden rise or surge of current in said primary winding causes a high tension current to be induced in the secondary winding 6'0 of the ignition coil and hence creates a spark across the gap of a spark plug 51. The apparatus is so designed that this operation is repeated each time brush 45 moves from one contact 50 to another, thereby causing the spark plugs of all the engine cylinders to fire in a predetermined sequence, the timing of the sparks being determined by the periodic opening of circuit breaker 62 as effected by cam 61.

Means are also provided for supplying a suflic'iently strong current to the spark plugs for firing the same when the magneto rotor is rotated too slowly for this purpose, as when the engine is being started. The starting or booster current is supplied from an outside source, such as a battery 13 (Fig. 5) and is distributed to the ignition coils and the spark plugs through the same distributor'parts as the main operating current from coil 26. The proper timing of the deliver of the booster energy to the spark plugs is preferably effected by a second circuit breaker 14, which is similar in construction to circuit breaker 62 and is operated by cam '5 I The booster circuit breaker is mounted on but insulated from bracket 30 and, hence, from ground, one terminal or contact thereof being connected with the source of booster current through a lead 15 and a plug-in con.- nect'or 15 mounted in cover H and similar to or identical in construction with connector H. The

other terminal or contact of insulated circuit I 6 breaker 74 is connected by a suitable lead 1-! to ring 49 of the distributor mechanism.

In the embodiment illustrated in Fig. 5, the booster or starting current is supplied by battery 73 through a buzzer type interrupter 18 which comprises a solenoid coil 19 and a buzzer or circuit breaker 86. The latter is normally held in closed position by resilient means 8| and is adapted to be 'electromagnetically opened by solenoid 79 when the latter is energized. One end of the coil of solenoid 19 is connected to a terminal of circuit breaker 39 and the other end thereof is adapted o be connected to ground through ignition switch 69 when the latter is in on position, as illustrated. The end of coil 19, which is .connected to circuit breaker Si is also connected through a resistance 82 to circuit breaker "II through plug-in connector l6 and lead 1.5, A suitable Condenser 83 connected across the contacts of circuit breaker 85 to eliminate arcing and a current limiting fuse 84 is preferably provided for limiting the current in the event the contacts of circuit breaker 8i} should stick in closed position. A starter operated switch .85, which may be adapted to open. automatically ting of the engine,- is also provided in between battery 13 and interrupter 18 When it is desired to start the engine, switch is closed and ignition switch 69 is moved to the illustrated on position. Current from battery 1 3 then flows through circuit breaker and solenoid coil it to ground at switch 69. Upon energization or excitation .of solenoid .19, circuit breaker fit electromagnetically opened, thereby cutting off the flow of current from battery 73. This results in the deenergization of solenoid 19 so that spring 8| is eiiective to again close the circuit at circuit breaker 8!) This cycle is repeated in rapid succession as long as switches '59 and B5 are in the positions mentioned above.

Each time circuit breaker 8D is opened, the magnetic field built up around coil 19 by the current flowing therethrough from battery [3 collapses and induces a relatively high voltage across the coil, thereby causing a sudden rise of current which will flow through a circuit including reis-tance'82 and circuit breaker 14, provided the contacts of the latter are in closed position. If the contacts of circuit breaker T4 are in closed position and circuit breaker 62 is open, the energy stored in the magnetic field of booster coil or inductance 19 is thus released in a surge to the magneto primary circuit each time contacts =80 open and is distributed to transformer coils '59 in the same manner as the main operating current heretofore described. The surges of energy delivered to primary windings 58 in this manner induces. current in the secondary windings which are capable of causing the desired sparks at gaps 51. The timing of the initial booster spark at each spark plug is thus determined by the closing of booster breaker M during the operation of interrupter TB while circuit breaker 82 is in open position. The booster circuit and the operation thereof are more fully described and claimed in an application of Marc C. Sawyer for Ignition means, filed on or about May 12. 1943.

Resistance 82 is provided in the circuit for the dual purpose of preventing a dead short circuit when both circuit breakers $2 and 74 are in closed position and to limit the maximum current which might flow through generator coil 2.5 from the booster circuit if the points of vibrator 80 should stick in closed position. This current through coil '26 must be sufiiciently small to avoid undue in the same manner as contacts 50.

demagnetization of rotor magnet II. In one satisfactory embodiment of the invention, resistance 82 has a value of approximately 3 ohms, the resistance of coil 19 is approximately one ohm, and the resistance of each primary winding 58 isapproximately 16 ohms. The relatively high resistance of windings 58 is desirable for the purpose of quickly dissipating the residual energy therein after the firing of each spark plug. The quick dissipation of the residual energy in the primary circuit after the firing of each spark plug is desirable for the purpose of avoiding arcing in the distributor as brush 45 passes from one contact 5!! to another and to avoid the production of secondary sparks at the plugs at the same time.

In Fig. 6, there is illustrated a modified form of contact for use in the distributor shown in Figs. 1 to 4 in lieu of contacts 53. Each of the distributor contacts 50 may be divided into a plurality of separate sections or segments, three such sections 50a, Ellb and 560 being shown. Contact segment 50a, which is the first of the three to be contacted by brush 45 during rotation of the distributor finger, is connected to outgoing lead 54 Segments 59b and 500 are connected to said lead through resistance 90 and resistances 90, 9|, respectively, said resistances being provided in lieu of incorporating a resistance in the coil windings 58, as mentioned above. Thus, when the current is permitted to flow from the source to coil 59 upon the opening of circuit breaker 62, there is but little resistance in the primary circuit. However, after the desired spark has occurred as a result of the first surge of current, brush 45 moves on tributor unit adapted for use in the ignition system of an internal combustion engine wherein distribution of current from a single source to a plurality of spark plugs is accomplished at a relatively low voltage. Additionally, there is provided a unit of the above character which is so constructed as to facilitate assembly thereof and to also facilitate inspection, adjustment and repair of the vital parts thereof. The construction of the unit provided is such that the wiring thereof is simplified and afiorded maximum protection when the unit is partially disassembled for inspection or the like.

Although only a single embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the same is not limited thereto. For example, many variations might be made in the current generating means, that is, the rotor may have a different number of poles than the rotor illustrated, or a generator of the stationary magnet tylpe might be employed. Also, many different types of plugin connectors may be employed in lieu of those illustrated. Various other changes in the design and arrangement of parts illustrated may also 'be made, as will now be apparent to those skilled in the art, without departing from the spirit and scope of the invention. For a definition of the 8 limits of the invention, reference is primarily had to the appended claims.

What is claimed is:

1. In apparatus of the class described, a magneto-generator comprising a rotor, a casing comprising a main casing member and a cover removably secured thereto, means for rotatably mounting said rotor in said main casing member, ignition distributor means and circuit breaker means mounted on and removable with said cover, and means for automatically drivably connecting said rotor and the rotatable parts of said distributor and circuit breaker means whenever said cover is in assembled position on said main casing member.

2. In apparatus of the class described, a magneto-generator comprising'a rotor, a casing comprising a main casing member and a cover removably secured thereto, means for rotatably mounting said rotor in said main casing member, ignition'distributor means and circuit breaker means mounted on and removable with said cover, a shaft rotatably mounted on said cover for driving the rotatable parts of said distributor and circuit breaker means, and gears on said shaft and rotor adapted to mesh for drivably connecting said shaft and rotor whenever said cover is operatively secured to said main casing member.

3. In apparatus of the class described, a magneto-generator comprising a rotor, a casing comprising a main casing member and a cover removably secured thereto, means for rotatably mounting said rotor in said main casing member, ignition distributor means and circuit breaker means mounted on' and removable with said cover, means for automatically drivably connecting said rotor and the rotatable parts of said distributor and circuit breaker means whenever said cover is in assembled position on said main casing member, and sockets of plug-in connectors mounted insaid cover and connected to all electrical leads from said distributor and circuit breaker means to be connected to leads externally of said casing. I

4. In apparatus of the class described, a magneto-generator comprising a rotor, a casing comprising a main casing member and a cover removably secured thereto, means for rotatably mounting said rotor in said main casing member, ignition distributor means and a pair of circuit breakers mounted on and removable with said cover, means for operatively connecting one of said circuit breakers to the coil of said magnetogenerator, means extending through said cover for operatively connecting the other of said circuit breakers to a source of electrical energy outside said casing, means extending through said cover for connecting the output terminals of said distributor means to circuits outside said casing, and means for automatically drivably connecting said rotor and the rctatableparts of said distributor means and said circuit breakers whenever said cover is in assembled position.

5. In apparatus of the class described, a casing comprising a main body member and a cover therefor, electrical current-generating means including a coil and a rotor mounted in said member, an ignition distributor comprising a rotatable member, circuit breaker means including a rotatable cam, said distributor and circuit breaker means being wholly supported by said cover within said casing, and means for drivably connecting said rotatable member and cam to said rotor when said cover and body member are secured together in operative relation.

Minded 6. In apparatusof the class described", a casing comprising a main body member and a cover therefor, electrical current-generating meam including a coil and a rotor mounted in said member, a shaft rotatably supported by said cover, an ignition distributor supported by said cover and including a rotatable part on said shaft, circuit breaker. means supported by said cover and including a cam on said shaft, and means on said shaft and rotor for drivably connecting the same when said cover is in operative position onsaid body member.

7. In apparatus of the class described, a casing comprising a main body member and a cover therefor, electrical current-generating means including a coil and a rotor mounted in said member, an ignition distributor and circuit breaker means wholly supported by said cover and extending for the most part into said body member, said current-generating nreans being operatively electrically connected with said distributor and circuit breaker means, and means for drivably connecting said rotor and the rotatable parts of said distributor and circuit breaker means whenever said cover is secured in operative position on said main body member.

8. In apparatus of the class described, a casing comprising a main casing member and a cover removably secured thereto, a magneto-generator including a rotor and coil mounted in said casing member, a shaft rotatably mounted on said cover, ignition distributor means mounted on said cover between the bearings for said shaft and having a rotatable part thereof mounted on said shaft for rotation therewith, circuit breaker means mounted on said cover and including a cam mounted on said shaft adjacent one end thereof, means on the other end of said shaft for drivably connecting the latter to said rotor whenever said cover is secured in position on said casing member, and means for operatively electrically connecting said coil, distributor means and circuit breaker means.

9. In apparatus of the class described, a casing comprising a main casing member and a cover removably secured thereto, a magneto-generator including a rotor and coil mounted in said casing member, a shaft rotatably supported by said cover, ignition distributor means supported by said cover between spaced bearings for said shaft and having a rotatable part thereof mounted on said shaft for rotation therewith, circuit breaker means supported by said cover and including a cam mounted on said shaft adjacent one end thereof, means on the other end of said shaft for drivably connecting the latter to said rotor whenever said cover is secured in position on "said casing member, means for operatively electrically connecting said coil, distributor means and circuit breaker means, a removable cover on the side of said casing member for permitting access to said distributor means, and a removable cover on the end of said casing member for permitting access to said circuit breaker means.

10. In apparatus of the class described, a casing comprising a main casing member and a cover removably secured thereto, a magneto-generator including a rotor and coil mounted in said casing member, a hollow shaft rotatably mounted on said cover and removable therewith from said member, ignition distributor means supported by said cover and having a rotatable part mounted on said shaft for rotation therewith, circuit breaker means supported by said cover and comprising a cam mounted on said shaft for rota- 1'6 nontherewith, means for operatively electrically connecting saidcoil, distributor means and ci-rcuit breaker means, means fordrivably connect ing said rotor and shaft whenever said cover is secured in position on said member, said last-named means including a gear on said shaft and means for coupling said gear and shaft for angular adjustments relative to each, other, and means including a bolt extending through said hollow Shaft for normally holdingsaid coupling means in driving engagement.

11. In apparatus of the class described, a casing having two detachably connected sections, a magneto-generator comprising a rotor and coil mounted in one of said sections, a rotatable shaft mounted in two spaced bearings supported in the other of said sections, an ignition distributor supported by said other section between said bearings and including a rotatable part on said shaft, circuit breaker means supported by said other section and including a cam mounted on said shaft for rotation therewith, means for operatively electrically connecting said coil, distributor and circuit breaker means, and means for drivably connecting said rotor and shaft.

12. In apparatus of the class described, a casing comprising a main body member and a removable cover therefor, electrical current-generating means including a coil and a rotor mounted in said member, circuit breaker means including a rotatable cam wholly supported by said cover within said casing, means for electrically connecting said coil and circuit breaker means, and means drivably connecting said cam to said rotor whenever said cover and body member are secured together in operative relation.

13. In apparatus of the class described, a casing comprising a main body member and a removable cover therefor, electrical current-generating means including a coil and a rotor mounted in said member, an ignition distributor comprising rotatable means and a stationary contact carrying block wholly supported by said cover within said casing, means for electrically connecting said coil and distributor, and means drivably connecting said rotatable means to said rotor whenever said cover and body member are secured together in operative relation.

14. In apparatus of the class described, 2. casing comprising a main body member and a cover therefor, electrical current-generating means including a coil and a rotor mounted in said member, an ignition distributor comprising rotatable means and a stationary insulating block with contact means thereon wholly supported by said cover within said casing, said contact means comprising an annular contact concentric with the axis of rotation of said rotatable means and a plurality of circularly arranged contacts disposed on a circle concentric with said annular contact and said rotatable means comprising an insulating member having a pair of radially-spaced, axially-extending openings therein, an electrical conductor secured to said insulating member and extending across adjacent ends of said openings, a conducting brush slidably mounted in each of said openings and adapted to project therefrom for rubbing contact with said contact means, resilient means normally under compression in said openings tending to move said brushes away from said conductor and flexible means for electrically connecting said conductor to said brushes and for limiting the movement of the latter by said resilient means, means for electrically connecting said coil to said annular contact,

1 12 and meansdrivably ebnnecting said rotatable V UNITED STATES PATENTS means to said rotor whenever said cover and body 1 7 member aresecured t gether in operative 1'egg z g fff fi3 latmn- 1 5 1,128,914 Stone Feb. 16, 1915 1,422,584 Pontois July 11, 1922' ggm fi'i 1,703,420 I Gibson -1 Feb. 26, 1929 ,709,996 Neighbour Apr. 23, 1929 7 REFERENCES CITED 2,023,26 BIIllckBI D80. 3, 1935 2,264,998 Mmer Dec. 2, 1941 The followmg references are of record 1n the 2272625 Spengler 10 1942 file 1111s P 2,295,338 Ely Sept. 8, 1942 2,399,165 Car'son Apr. 30, 1946

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