US2187070A

US2187070A - Ignition distributor

Info

Publication number: US2187070A
Authority: US
Publication date: 1940-01-16
Anticipated expiration: 1957-01-16

Description

Jan. 16, 1940. ARTHUR 2,187,070

IGNITION DISTRIBUTOR Filed April 4, 1938 4 Sheets-Sheet 1 Jan 16,. 19400 J. L, ARTHUR I 2,187,070

IGNITION DISTRIBUTOR Filed April 4, 1938 4 Sheets-Sheet 2 INVENTOR (/AMAS L Aer/we BY hi4 ,1 ATTORNEYp' Jan. 16, 1940. ARTHUR 2,137,070

IGNITION DISTRIBUTOR Filed April 4, 1938 4 Sheets-Sheet 3 INVENTOR JAMES L x4e ff/Me ATTORNEj J. L. ARTHUR IGNITION DISTRIBUTOR Jan. 16, 1940.

Filed April 4, 1938 4 Sheets-Sheet 4 HNVENTOR uhmfs L Aer-Hue BY Mm MZJV A, ATTORNEY Patented Jan. l6, 1 940 PATENT OFFICE IGNITION DISTRIBUTOR James L. Arthur, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application April 4, 1938, Serial No. 199,882

12 Claims.

terrupter that concentricity between the breaker plate and cam will be maintained for all positions of adjustment of the breaker plate. In order to accomplish this object I providean antifriction bearing for the cam shaft near the end of the shaft to which the cam is attached. The

, outer race of the bearing has a running fit with- 'in a centrally located recess in the distributor housing so that the outer race is journaled for rotation within a wall of the distributor housing. To the outer race of the antifriction bearing, I secure the adjustable circuit breaker plate. Therefore, the circuit breaker plate is maintained by the antifriction bearing in a concentric relation with respect to the ignition timer cam. Another object of the present invention is to provide a water proof connection between the distributor posts or the distributor center contact and the high tension cables to which the posts and the center contact are respectively connected. In order to accomplish this object, the distributor cap is provided with metallic. inserts which provide the distributor post's. past which the rotor segment rotates and the center contact to which the rotor segment is connected. Each of these inserts carries a sharp pointed pin projecting outwardly from the upper surface of the cap. Each insert extends flush with a plane boss at right angles to the pointed pin. A sleeve or thimble of soft rubber is placed over each high tension cable, and the cable end with the thimble assembled thereon is forced sideways down over the pointed pin which pierces the thimble. the insulation of the cable and the cable itself which is made of twisted or stranded small wires. The thimble is provided with a plane surface which fits snugly against the plane boss with which the insert is flush. On the side of the thimble remote from the boss on the dis tributor cap, the thimble is provided with a boss which is substantially parallel with the boss of the thimble which bears against the boss of the distributor cap. This other boss of the thimble is adapted to be engaged by a surface of a dis.- tributor cap cover which can be attached to the cap by screws, the tightening of which causes the rubber thimble to be squeezed between the distributor cap and distributor cap cover thereby causing the thimble to be clamped tightly against the boss of the distributor cap, thereby preventing moisture from entering into the insert. i

A still further object of the invention is to provide a quick detachable means for connecting the ,5 distributor rotor with the timer cam, said means having provisions for preventing accidental displacement of the rotor from the camin a direction axially of the cam.

A stillfurther object ofthe present invention is .10 to providefor insulatingly supporting the end of .the conducting leaf spring of the circuit breaker lever upon a metallicbracket upon which thestationary contact is mounted.

Another object of the present invention is to -15 provide a pivotal connection between the adjustable, contact bracket and an actuating member, said pivotal connection being adjustable to various positions within a limited range. A feature of this connection is that it includes a single ,20 screw by which the connection is assembled'and by which it is secured to the breaker plate in adjusted position. In this connection it is still a further objectt'o provide a construction in which the screw referred to is used to secure in posi 25 tion a metal clip on the end of a wire which provides a part of the ground connection of the primary circuit of the ignition distributor.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings: i 1 r Fig. l is a vertical, longitudinal sectional view .35 of an ignition distributor embodying the present invention. This sectional view being taken on the line l--l of Fig. 4.

Fig. 2 is a fragmentary sectional view taken on the line 2-2 of Fig. 4.

Fig. 3 is a sectional view on the line 3-3 of Fig. 1. 1 1

Fig. 4 is a plan view partly in horizontal longitudinal section of the ignition distributor with the cap and rotor removed. I

Fig. 5 is a fragmentary plan view of the timer cam on a larger scale than shown in Fig. 4.

Fig. 6 shows a plan view of a ball bearing received within a recess of a plate with which the bearing is to be assembled.

Fig. 7 is a view similar to Fig. 6, but showing the sub-plate and bearing in assembled relation.

Fig. 8 is a plan view of the cam circuit breaker plate assembled with the bearing and sub-plate of Fig. 7.

Fig. 9 is a planview of the assembly of main circuit breaker plate and auxiliary circuit breaker plate.

Fig. 10 is a fragmentary sectional view on the line I0-l0 of Fig. 4 showing a circuit breaker lever assembled on an auxiliary circuit breaker plate which ismounted upon the main circuit breaker plate. which. is secured to the outer race of the ,ball bearingby the sub-plate.

Fig. llis a fragmentary sectional view on the line ll|l of Figs.

Fig. 12 is an exploded view in perspective of various parts shown in Fig. 11.

Fig. 13 is a side elevationfof. the rotor. I g

Fig. 14 is a bottom plan view of the rotor. F

Fig. 15 is a sectional view on the line l5-l5 of Fig. 14. v 1 I Fig. 16 is a perspective view of a resilient clip for securing the rotor to the cam.

17 is azzperspective View on an enlarged scale on one of the stationary contact brackets of the circuit breaker mechanism.

Fig. 18 is a plan view'thereof; and

Fig. 19 is a sectionalviewon. line l9-l9 of Fig.18. F

Referring to Fig- 1, *the ignition distributor comprises a cup shapedhousing 20 having a tubular shank 2| adapted to be received within a recess of the frame of-the engine with which the distributor isassociat'edr The shank 2| carries a ball'bearing'lZZ within which a tubular shaft 23 is journaled. vShaft 23 carries, a coupling 24 by which a connection with anengine driven shaft may'be made. 'The bearing 22 is protected from'dirt and the escape of lubricant therefrom is prevented by seals 26 which are a part'of the bearing assembly. The threaded recess 25 in the lower end of shank 2| receives a nut. 25a which secures the bearing 22 within the recess.

The housing cup 23 supports the bottom wall 3| of a. dish-shaped housing member 30. Wall 3i is provided centrally with a recess 32- which receives the outer race 33 of'an anti-friction ball bearing 34, the inner race 35 of which fits over a shaft 36. The bearing race 35 is located between a shoulder 31 'of the shaft 36' and a I spacing sleeve 38 retained in position .by a. C

washer 39 which fits into a groove win the shaft 3E5; washer 39 is maintained in position by reason of the fact that said washer is received within'a recess 46 provided in the shouldered surface of the timer cam 42 which fits over the upper end of the shaft 36, said upper end being divided by slots into resilient prongs 43 which ing fit within the cylindrical bore 5| of the shaft 23. The housing portions 2-0 and3ll are concentric; "Hence; the bearings 22' and Mare-in alignment and the shafts 23and- 33' are substantially in alignment. The shaft 23 drives the shaft 36 through a'device responsive to engine speed for varying the angular relation between the shafts for the purpose of varying the ignition timing in accordancewith engine' speed; This speedres sponsive device comprises a weight supporting distributor theportion 12a.

plate 52 attached to the shouldered upper end of the shaft 23. Plate 52 provides pivot posts 53 each pivotally supporting a weight 54 having an arm 55 hearing against a lever or cam 56. There are two levers or cams 56 integrally connected by a hub 53 which isdrivingly fitted over a knurled portion 51 of the shaft 35. A slot 58 is milled in shaft36 -opening into b'ore5l of shaft 23 to permit-access of lubrication of shaft 36 in bore 5!. Motion of the weights outwardly to cause counterclockwise rotation of the cams 56 is restrained by springs 60 attached. at one end of the pivot posts 53 and at the other end to studs The outer race 33 of the ball bearing, 34 has a running fit. withinthe recess 32 of housingmember 33. The bearing race 34 therefore provides a journaled bearing for the adjustable circuit breaker plate 13 which is secured to the race 33 in a novel'manner now to be described. A part of this securing means is a sub-plate H (see Figs. 5 and 7) having. an opening 12 which is defined by'arcuate portions l2wand 12b and straight portions We and 12d. The arcuate portion 12a is greateriin diameter than the outside diameter of the race33 so that race 33may be entered within Race 33 is provided with a groove 'l'3having a diameter only slightlyless than the distance between the portion.l2c. and

12d of member". The portion 72b is an arc, the

"#211, 12c and 12d. When the parts are assembled asshownin Fig. '7, the annular flange M of subplate 11- will be substantially. concentric with respect to the bearing. '34; The plate H is notched at Ma to provide clearance. i Fig. 8 showsthe main. breaker plate 10 assembled with sub platel .H by means of screws 15. extending. through holes in the plate 70. andscrewed into holes 16 tapped in the plate: 1]. When plates ill-and H are thus assembled, tangs 11 struck out of the plate H1 ezntend closelyalongv the outer cylinder wall of the bearing race 33 and thus prevent the sub-plate H from. shifting out".

of itsposition'relative. to the bearing 34 shown in Fig.7.

Plate 13 is provided centrally with a hole which is: concentric with. the bearing 34 and I which provides a journal for a flange 8| of an auxiliary plate 82. Plate 83 is therefore pivotally mounted upon theplateflw, the axis of the pivot being coaxial withthe bearing 34. The adjustment of plate 32 upon plate leis effected by the turning of a disc 83 having an eccentricshank 84 journaled in the plate Til. The disc B3-is provided with aslot 35' adaptedto receive the blade of. a. screw driver by? which the disc 33 may be turned bylturning' the screw driver. The plate 82 is secured-to the plate 10 in the desired position of adjustment by screws 85' which pass through arcuate slot 8? provided in plate 82 anduwhich screw int'o' tappe'd'holes BB provided by p'late'lfls The

plates

10 and 82 support similar circuit breaker mechanisms which Will new bedescribed.

.to the bracket.

Plate supports a pivot stud 90 which receives the nonconducting journal bushing 9I of a circuit breaker lever 92 which is thus insulatingly mounted upon the plate 10. Lever 92 carries an L-shaped rubbing block 93 bearing against the cam 42. The rubbing block 93 is urged toward the cam 42 by a leaf spring 94 which serves as an electrical conductor in a manner to be described. Lever 92 carries a contact 95 engageable with a stationary contact 96 carried by a bracket 91 which is adjustable upon the plate 10, said bracket 91 being pivoted upon the breaker lever pivot stud 90. Bracket 91 is adjusted about the pivot 90 by the turning of a disc 98 having an eccentric shank 99 pivotally connected with the hole I03 in the plate 10, see Fig. 9.

The operation of the circuitbreaker is most obvious. The lobes of the cam 42 engage the rubbing block 93 in order to move the lever 92 to separate the contact v95 from the contact 96. When a cam' lobe leaves the rubbing block 93 and spring 94 urges the contact 95 into engagement with the contact 96. A similar circuit breaker mechanism is mounted upon the auxiliary plate 82 and the parts of this similar circuit breaker are labeled with the same reference characters as those applied to the circuit breaker which has just been described, but with the afiix a. Therefore. the circuit breaker mounted on auxiliary plate 82 will need no further description.

There is a feature of the contact bracket 91 which can best be understood by reference to Figs. .17, 18 and -19 which show one of the stationary contact brackets on an enlarged scale The bracket 91 has a hole I03 which receives a portion of the pivot post 90 around which the bracket 91 is pivoted. Bracket 91 is provided with an ear I05 to which a rivet I06 secures a nonconducting plate I01 having a notch I08 receiving a portion I09 of the bracket 91 and having a portion IIO which extends into an opening III provided by the bracket. In this way a single rivet I06 is all thatis needed to secure the plate I01 Plate I01 is provided with an elongated hole II2 which receives a screw II3 which cooperates with a nut II4 to secure to the plate I01 an end of the circuit breaker lever spring 94. The screw I13 and the nut II4 also secure tothe plate I01 the terminal clips on the end of conducting wires by which electrical connections are to be made with the circuit breaker lever springs 94 as shown in Fig. 4. One of these wires is the wire I which makes a connection between lever spring 94 and lever spring 94a. Another of these wires is the wire I 2I which makes an electrical connection between the lever spring 94 and a terminal I22 which is insulatingly supported by the housing member 30. Terminal I22 is the insulated terminal of the primary circuit. The two circuit breaker levers 92 and 92a are electrically connected with terminal I22. The stationary contacts 96 and 96a are grounded through the supporting

plates

10 and 82 which together are grounded by means of a flexible wire I25 attached by screw I26 to housing 30 andattached by screw I30 to the plate 10 in a novel manner which will now be described with reference to Figs. '11 and 12.

Referring now to Figs. 11 and 12, there is shown a fragment of the plate 10, which is provided with an arcuate slot I3I. Slot I3I receives a shouldered portion I32 of a washer I33having a shouldered portion I34 which is received by a hole I36 in an operating member I36. The screw I30 passes through a loclc washer 'I31- then through a terminal clip I38 attached to wire I25 and then through a washer I39. Screw I30 passes through a plane hole in the washer I33 and then through a hole I40 tapped in a clip I4I which'is reinforced by a plate I42 welded or' otherwise secured to the clip I4I. clip MI is provided with tangs I43 which extend around the edge of the plate 10 so as to prevent turningthe clip I4I- when the screw I30 is turned. By loosening the screw I30 the assembly of parts can be shifted relative to the plate 10, the shouldered part I32 of thecollar I33 sliding along the arcuate slot I3I of the plate 10. In this way the relation between the plate 10'and the operative member I36 can be adjusted. When the desired adjustment has been made, the screw I30 is tightened to secure the parts in assembled relation and in fixed relation with respect to the plate 10, yet to provide a pivotal connection between the plate'10 and the operating member I36 and, at the same time, to provide an electrical connection between the plate '10 and the wire clip I38 to which the wire I25 is attached.

Referring to Fig. 4 the operatingmember I36 is actuated by means which functions in response to variations in suction pressure in the engine intake pipe passage. The member I36 is attached to aiiexible diaphragm I50, the periphery of which is clamped between the flanges of cup shaped members I 5I and I52. Member I52 carries a tubular part I53 into which a pipe connector I 54, threaded for making connections leading into the engine intake manifold, the part I53 housing a spring I55 which exerts pressure tending to maintain the diaphragms I50 in the position shown in Fig. 4. Movementof the member I36 is limited by a stop I56 extending into an opening I51 provided by member I36. Stop I56 is integral with a bracket I58 to which the cup shaped part I5I is attached. Bracket I58 is attached by screws I59 to the housing 30. It is apparent that variations in enginesuction will effect movement of the diaphragm I50 thereby effecting movements of the

breaker plates

10 and 82 which will locate the circuit breaker lever in correct position relative to the cam to effect proper timing of the engine ignition sparking into conformity to engine operating conditions.

During the movements of the

circuit breaker plates

10 and 82 effected in accordance with variations in, engine intake suction, the circuit breakers will remain always with the same distance from the axis of the cam. This is important, otherwise the spark timing might vary in accordance with the position of the

breaker plate

10 and 82. While the variation would not be so very material in engines having relatively small number of cylinders, any slight variation in distance between the cam and circuit breaker levers due to slight eccentricity of movement of the circuit breaker plates relative to the cam might seriously effect ignition timing of engines embodying relatively large number of cylinders.

The'disclosed embodiment of the present invention. is anlignition' distributor having 12 cylinder enginesp Hence, the cam 42 has 12 lobes 42m. As shown in Fig. 5 on an enlarged scale, acam of this type has been very carefully dimensioned in order that the lobes will all be exactly alike and will be correctly spaced apart. While it is important: that the cam conform to themescribed dimensions with great accuracy, it is equally important that concentricity between the breaker plates and the axis of the cam be maintained; otherwise ignitionftiming will not be properly synchronized-with the engine. The desired concentricity is-provided in accordance with the presentinvention by securing the circuit breaker plates to the outer race of that ball bearing supporting thetimer cam shaftand located nearest to, thetimerg-cam. r

.The cam shown in- Fig. 5 provides for 'a closing period I of circuit, breaker contacts of 16 and; an open period, of 14 cam shaft rotation. To secure a greater closing period would meana sharper rise on the cam lobes and greater wear or' the cam and rubbing block of. the breaker lever. In order to obtain a longer total closing period of the ignition primary circuit to allow the ignition coil to build up. sufficiently for adequate ignition, two' circuit breakers are so locatedthatone closes and opens 5 respectively ahead of the closing and opening period of the other circuit breaker. -This increases the total time of. primary closing to 16+5 or 21.

To reduce sparking atthe. contacts of the cir- .cuit breaker, a condenser Ifiii is connected in parallel with the circuit breaker, The condenser has one, foil connected with an insulated terminal wire IBI connected \Vithfthe terminal I22. The other condenser foil is grounded. on the metal container of the condenser which is attached by metal clip I62tand a screw I63 to the housing 39.

A distributor cap I19 fits upon the rim of the housing as shown in Fig. 1 and is secured thereto by spring clips l'lI .hingedly connected at I12 with brackets I13 attached to the housing 38. The freeendsof the clips I1I bear against lugs I 14 provided by the cap I151. Cap Hill is provided with inserts I15 located in acircular row. The lower end of each insert provides a distributor post 16 past which swings a distributor segment I11 embedded in a nonconducting distributor rotor I18. The hub ofthe rotor I18 is provided with a recess I19 lined with a metallic liner insert I88 having flats which fit around the flats 42 a and 42b provided by the cam 42 as shown in Figs. 1, 4. and .15. -As shown in Fig. 14, the flats of the insert ifilil are marked WM and 182b, since these conform respectively with fiats42aand 42b of cam 42. In order-to prevent accidental displacement. of the rotor lillaway from the I cam 42, there is provided a. spring. clip I83shown in Fig. 16 which comprises an arcuate portion I84 received Within a groove I85.-provided by a rotor I i8 and having- .tangs i355 which extend through notches 118,1,in the: flange I38- of the The distributor segment ill a bare por tion- Illa at the center of the distributor rotor I13 engaged by a. conducting button I99 mounted on the end of a-sleeveiQl guided by an insert IBZI-and-urged downwardly by spring hi3. ';l.he

. center insert I92 and each. of,;the-distributor contact with the stranded wires 12!".

agrsao'io posts inserts I15 terminatefiush with a planeis'urface of a boss. The central boss isnumbered I 9211, and the bosses that are in the circular row are number. I15a. The bossesllfia are all in the same plane which plane is parallel to the Plane I9t extends upwardly from a plane'surface I91 which is spaced at a distance from the central part ofthe surface IBEa which is substantially equal to the-distance between the plane of the. central boss 192a and the plane of bosses I15a, for a purpose to be described. The plane surface I91 merges into a flange 198. To each of the inserts I15 and I92 is secured a sharp pointed pin I99 for making an electrical connection with a high tension cable 269 comprising a flexible stranded conductor 21H encased in insulation 202.

Each conductor 200 is squared off at the end and is inserted into a soft rubber sleeve or thimble 203 having on diametrically opposite sides thereof bosses 2M and 295 each provided with a shallow conical recess 2%. Before the cover I94 is attached to the distributor cap I10, the thimbles and assembled ends of the cables 209 will each be pushed down over a pin I99, the conical recess 2536 serving to guide or start the pin in the right direction so that it will pierce diametrically through the" cable 2M and its point will make Then the cover I945 is secured in position; and the tightening of the screwsI95 will cause each one of. the thimbles 203 to be clamped between a plane boss provided byjthe distributor cap I10 and a surface provided by the cover 194. As the bosss 204 and 2115 vof the thimbles 203 are alike, it matters little which one of the bosses is pushed down over the surface and the-various bosses I150. bessub- .stantially equal and. be equal to thedistance between the central part of the cover surface .lQBa and the boss I92a.. In this way all of. the

thimbles 293 will be clamped securely in position by tightening the screws I95 which. secure the cover I94 to the. clip I10. Thus each thimble 203 is tightly squeezed. around a cableiwil andeach thimble also tightly forced against an insert of the distributor cap. Thus, a water tight connection-betweeneach of the cables and each of the inserts of the distributor cap is provided.

While the embodiment of the present invention as herein disclosed. constitutes: a preferred.

form, it is-to be understood that other forms might be adopted, all coming within: the scope of the claims which. follow.

What is claimed is as follows:

1. An ignition distributor for internal combustion engines comprising .a housing. an antifriction bearing having its outer race rotatablyjournaledin the housing, a shaft carrying a timer cam and fixed within the inner race, a circuit breaker plate fixed to the outer race, a circuit breaker supported upon the plate andincluding a breaker arm: operated. upon. by; the cam. and means for adjusting the breaker plate, said. plate rotating ccaxiallywith-. respcct=- t the by u.

reason of the attachment of the plate to the bearing outer race.

2. An ignition distributor according to claim 1 in which the breaker plate is provided with means centering it with respect to the bearing outer race, and in which the breaker plate is attached to the race in its centered position by a subplate attached the breaker plate and fitting into a groove provided by the race.

3. An ignition distributor according to claim 1 in which breaker plate is provided with a central opening through which the cam shaft extends and is provided with spaced tangs located in a circular row concentric with the opening in the plate said tangs embracing the bearing outer race to center the plate with respect to it, and in which the breaker plate is attached to the race in its centered position by a sub-plate attached to the breaker plate and fitting into a groove provided by the race.

4. An ignition distributor according to claim 1 in which the breaker plate is provided with a central opening through which the cam shaft extends and is provided with spaced tangs located in a circular row concentric with the opening in the plate said tangs embracing the bearing outer race to center the plate with respect to it, and in which the breaker plate is attached to the race in its centered position by a sub-plate having a central opening defined by surfaces which fit into a groove provided by the race and having an off-center opening large enough to receive the race, said off-center opening merging with the central opening whereby the sub-plate can be located around the race and then be moved so that said surfaces of the sub-piate are received by the groove in the race, and means for securing together the breaker plate and sub-plate in their centered positions relative to the race.

5. An ignition distributor according to claim 1 in which a main drive shaft, journal-ed in the housing at a point remote from said antifriction bearing, has a tubular portion which receives a portion of the timer cam shaft, and in which the two shafts are connected by means responsive to speed of rotation for varying the angular rela tion between them.

6. An ignition distributor according to claim 1 in which the means which adjusts the circuit breaker plate includes an arm adjustably secured to the plate by a plate clamping device which provides a pivotal connection between the plate and arm said device fitting into an arcuate slot concentric with the antifriction bearing, said device including two washers engaging opposite surfaces of the breaker plate and a screw for securing the washers in clamping position.

7. In an ignition distributor the combination of a distributor rotor, atimer cam supporting the rotor in a fixed angular position relative thereto,

and a quick detachable means for preventing axial displacement of the rotor relative to the cam and comprising a resilient member having a part received by a groove in the rotor and a part received by a groove in the cam.

8. in an ignition distributor, the combinatio of a distributor cap and a distributor cap cover having substantially parallel, spaced surfaces, the surface or" the cap being flush with an end surface a metallic distributor insert embedded in the cap, a pointed pin projecting from the insert and into the space between the cap and cap cover, an insulated stranded wire conductor for making an electrical connection with the pin, a soft rubber bio on an end of the Wire, the pin piercing s1 ewise through the thimble and conductor including the stranded wire thereof, the thimble having diametrically opposite plane bosses one of whi h is pressed against the surface of the cap and overlying the insert end surface, and the other of which is pressed against the cap cover and means for securing the cap cover to the cap and for causing the thimble to be clamped between the cap and cap cover to squeeze the thimble against the insulated wire.

9. The combination defined by claim 8 in which diametrically opposite conical recesses are provided, respectively, in the bosses of the thimble, I

either one of the recesses being used to start the thimble properly over the pin, the point of the pin being applied to the apex of the conical recess.

10. The combination defined by claim 8 in which the capcover has an annular flange surrounding a thimble engaging surface thereof, said flange extending downwardly against the insulated conductor and outside of the outer end of the thimble.

11. An ignition distributor comprising a housing, an antifriction bearing having its outer race journaled in the housing, a timer cam on a shaft, said shaft being carried by the inner race of the bearing, a circuit breaker operated by the cam, anda plate supporting the circuit breaker, said outer race providing a support for the cam shaft and also a concentric bearing for movement of the circuit breaker plate.

12. An ignition distributor comprising a housing, a double ball bearing supported by the housing, a timer cam on a shaft supported by the inner race of the bearing, a circuit breaker operated by the cam and a plate supporting the circuit breaker and attached to the bearing, said bearing serving as means for maintaining the circuit breaker plate in a definite relation to the cam in order to accurately maintain a definite amount of separation of the contacts of the circuit breaker.

JAMES L. ARTHUR.