US2696534A

US2696534A - Mallory

Info

Publication number: US2696534A
Authority: US
Publication date: 1954-12-07
Anticipated expiration: 1971-12-07

Description

Dec. 7, 1954 v M. MALLORY CIRCUIT BREAKER 5 Sheets-Sheet 1 Filed Oct. 8, 1951 H 6.4. INVENTOR.

MAE/ON MALLORY ATTORNEYS.

M. MALLORY CIRCUIT BREAKER Dec. 7, 1954 3 Sheets-Sheet 2 Filed Oct. 8. 1951 INVENTOR.

MAR/ON MALLORY BY ATTORNEYS.

Dec. 7, 1954 M. MALLORY 2,696,534

CIRCUIT BREAKER Filed on. s. 1951 s Sheets-Sheet 3 [7 /Z V y g /7;

INVENTOR.

MAE/0N MALLORV A TTORNE Y5.

United States Patent Ofiice 2,696,534 Patented Dec. 7, 1954 CIRCUIT BREAKER Marion Mallory, Detroit, Mich.

Application October 8, 1951, Serial No. 250,311

11 Claims. (Cl. 20030) This invention relates to a circuit breaker and more particularly to a circuit breaker for the ignition system of an interial combustion engine.

One of the main difficulties with circuit breakers is that they are short-lived owing to the burning of the breaker points. It should be borne in mind that in an eight-cylinder engine the circuit breaker opens and closes four times for each revolution of the crankshaft. This means that, if the crankshaft turns 4,000 R. P. M., the breakers must close and open the circuit 16,000 times per minute. Some of the engines today turn up to as high as 7,000 R. P. M., which means that the breaker must open and close the circuit 28,000 times per minute.

The circuit breaker arm must be very light and of low inertia to prevent bouncing and chattering at the high speeds. Difficulties have arisen when making this arm light to reduce rebound and chattering because, if the armis weakened by making it light, it will flex on closing and opening and cause creeping of the contact points which upsets the circuit and, in turn, causes excessive flashing.

It is an object of this invention to produce a circuit breaker which is of light construction to thereby prevent rebound and chatter of the contact points when they close.

Contact points should close and break clean without any rubbing or creeping and the movable contact point should close against the fixed contact point at identically the same point or place every time, otherwise flashing or arcing will occur and the life of the points shortened. Creeping of the contact points will occur if there is any looseness due to wear, or for any other reason, between the circuit breaker arm and the post upon which it is pivoted.

It is an object of this invention to produce a circuit breaker which will maintain a constant accurate bearing between the breaker arm and the post upon which it is pivoted regardless of wear.

It is another object of this invention to prevent rebound of the circuit breaker upon closing. This object is achieved by utilizing a heavy spring which not only biases or urges the circuit breaker arm in a closing direction but at all times presses the bearing portion of the circuit breaker arm tightly against its post.

In its normal use, even if there is no flashing between the contact points of the circuit breaker, considerable heat is created at the points due to the flow of the electric current.

It is an object of this invention to produce a circuit breaker which is of exceptionally light weight, of rela tively great strength, and wherein the member which strengthens the circuit breaker also acts as a heat dissipating or radiating fin for cooling the circuit breaker points.

Fig. 1 is a top plan view showing the principal form of my ignition circuit breaker.

Fig. 2 is a perspective view showing the unitary bearing and rubbing block.

Fig. 3 is a perspective showing the arm which carries the movable contact point.

Fig. 4 is a top plan view showing a modified form of my invention.

Fig. 5 is a top plan view of the circuit breaker and its supporting bracket but with the pivot post removed.

Fig. 6 is a section along the line 66 of Fig. 1.

Fig. 7 is an elevation of the circuit breaker showing how the arm is floated upon the circuit breaker spring which is the sole support for the arm.

Fig. 8 is a section along the line 8--8 of Fig. 1.

'thermosetting or thermoplastic material.

Fig. 9 is a perspective of another form of circuit breaker arm.

Fig. 10 is a top plan view showing a modified form of circuit breaker.

Fig. 11 is a top plan view of the modified form of circuit breaker and its supporting bracket shown in Fig. 10 but with the pivot post removed.

Fig. 12 is a detail view of the spring support arm and the breaker arm pivot post showing their parallel relationship.

For purposes of description, I have shown my circuit breaker as a part of an automotive ignition system. The parts shown in the drawings are referenced as follows: plate 1, cam 2 fixed on rotary shaft 3 (cam 2 rotates relative to plate 1, as indicated by the arrow, in a conventional manner), support 4 integral with bracket 7 and carrying fixed contact 5, electrical lead 6 in circuit with support 4 and contact 5, support bracket 7 adjustably mounted on plate 1 and having an arm 7a to which one end 8 of spring 9 is anchored or fixed by means of bolt 10 and nut 11, insulating washers 12 and 13 electrically insulate spring 9 from support arm 7a and plate 1, elec trical lead 14 in circuit with spring 9, breaker arm 15 which comprises an integral bearing 16 and rubbing block 17 secured to metal arm 18 by rivets 19. The end of spring 9 is bifurcated or slotted as at 911. The slotted end 9a of the spring straddles bolt 10. Rivets 19 also secure the flat end 20 of spring 9 to

member

16, 17 and serve as electrical conductors between spring 9, arm 15 and circuit breaker point 21.

Spring 9 is made from a flat metal strip of spring steel, preferably copper plated, which is coiled into a half loop 22 and is thereby tensioned so that it holds the bearing 16 against pivot pin or post 23 which is fixed to plate 1. The tension or force of spring 22 causes bearing 16 to exert a pressure or force against pin 23 in the same direction as the cam 2, e. g., spring 9 in Fig. 5 applies a pressure generally toward the left or in the same direction as the force applied to the breaker arm by a left had cam whereas in Fig. 11 the spring 9 applies a pressure generally toward the right or in the same direction as the force applied to the breaker arm by a right hand cam. Hence, regardless of the wear that takes place between bearing 16 and pin 23, there will always be a snug fit between pin 23 and bearing 16.

The bearing member and rubbing block 17 are made of electrically insulating material, such as hard fiber or a Bearing 16 presents a half round or semi-cylindrical socket 25 for engagement with cylindrical post 23. The socket 25 should extend for at least including groove 26, around post 23 so as to take care of right and left hand running cams. The inside radius of socket 25 is preferably the same radius as that of post 23 so that socket bearing 16 contacts or bears against post 23 along a semi-cylindrical surface. This produces axial stability of bearing 16 on post 23 so that the arm and contact point 5 will not shift or rock vertically, that is, in the plane of the axis of rotation. Spring 9 is positioned edgewise with respect to support plate 1 so that its widest surface is in a vertical plane which gives the spring vertical stiffness to prevent shifting or sliding of bearing 16 up and down on post 23. In other words, the vertical stitfness of spring 9 holds bearing 16 in the same vertical position on post 23 as the high points of the cam 2 contact rubbing block 17 to pivot arm 15 about post 23 to open

contacts

5 and 21. As the rubbing block slides off the high point of the cam, spring 9 pivots arm 15 to close

points

5 and 21.

Bearing 16 is provided with a groove 26 in the face of socket 25. This groove extends parallel to post 23. Hence, bearing socket 25 has two spaced surfaces in bearing or sliding contact with post 23 and these surfaces are located on opposite sides of groove 26. As bearing 16 wears during usage due to the above arrangement, the bearing 16 will tend to maintain accurate contact with post 23 thus giving stability to breaker arm 15 and causing

contact points

5 and 21 to always close at substantially the same point.

It will be noted that rivets 19 pass through openings 26 1n rubbing block 17 and openings 27 in arm 18. These openings are otfset lengthwise of arm 18 to distribute the stress and thus prevent the rivers" from b'e'ffifiiiig" loose and prevent breakage of the spring arm where it connects to the rubbing block. This is important when one bears in mind that arm 18 ismade of very thin metal so as to reduce its weight to a minimum.

The metal breaker arm 18 is made of very light sheet metal, such as steel, and is provided with a peripheral stifienihg' flange 28 which extends around two sides and the end of the arm which carries the contact point- 21. A channel rib 29 is also formedupwardly in the bottom 30 of the arm 18.- This stiffening rib 29' extends from one end 31 of the arm to a point 32 adjacent the other end 33 of the arm 18. Point 32 is spaced substantially a distance equal to the diameterof the contact point 21 from the end 33 of breaker arm 18. This provides" a flat area- 34 adjacent end 33' of the arm so that the contact point 21 can be spot welded to arm 1-8. If desired, contact point 21 can be secured to arm 18 by ether known means, such as soldering or brazing. The contact points can be made from any of the well-known materials such as platinum or tungsten The flange 28 around the edge of the arm acts as a stiffener and a heat radiating fin. Further; since the flange 28 extends away freni contact point 21, the feeler gauge for adjusting the contact points can be inserted between these points. The above described construction of the breaker arm 18 is very important because it reduces weight of the breaker arm to a minimum and thus cuts down the inertia of the breaker arm which is very important, particularly at higher engine speeds. The metal breaker arm 1811, Fig. 9, is the same as that shown in Fig. 3 except that the contact point end of the arm is not turned out of the plane of the arm and thus the bottom 30, including the flat area 34 are co-planar.

The form of breaker arm shown in Fig. 4 is identical with that shown in Fig. 1 except that the bearing portion 35 is in the form of a V to provide a V socket 36 which contacts post 23 along spaced lines or areas 37, thus providing the clearance 38 between the bight portion of the V socket 36 and post 23.

In the above forms of my circuit breaker arm spring 9 is under tension, pressing the bearing portion of the arm against the post generally in the same direction that the cam presses the am. As the bearing wears,

this wear is immediately and automatically taken up due to the tension of spring 9 and thus any slack or play between the post and bearing is obviated and the break between

contact points

5 and 21 is always even, smooth, and without chatter and the points always come together at the same point. The tension of spring 9 is such that it is always pressingbearing 16' against post 23 and contact point 21 in a direction against contact point 5 so that, in effect, the spring '9 is applying torsion to the arm 15 tending at all times to rotate the breaker arm clockwise, Fig. 1. Thus, depending upon the spring pressure, bearing 16 has a sliding frictional pivotal engagement with post 23. The friction between post 23 and bearing 16 causes the rubbing block 17 to hug the cam 2 as it rotates and also, due to the lightness of my breaker arm, aids in preventing rebound of the breaker arm as contact point 21 strikes contact 5.

The end 40 of the rubbing block 17 which contacts the cam 2 is curved or molded with two radii. As shown in Fig. 8, the end 40 is curved as at 41 so that the face of the rubbing block which contacts the cam 2 is convex with respect to the planar face 42 of the cam 2. Thus, curvature 41 is about a radius having its center preferably on a line 43 to the left of face 41, Fig. 8. The face of the rubbing block which contacts cam 2 is also curved or formed about a radius as indicated at 44, Fig. 5, so that in effect the end 40 of the rubbing block has substantially only a point contact with the face 42 of the cam.

The molding of the face of the rubbing block which contacts the cam about the two radii 41, 44' is important because it reduces to a minimum the friction between the rubbing block and the cam and curvature 41 is particularly important because if perchance post 23 is not parallel with the axis of rotation of cam 2, the arcuate face 41 of the rubbing block will nevertheless readily adjust itself with respect to the faces 42 of the cam against which it rubs and at the same time the socket 25 will fully contact post 23. If face 41 were straight, then, under the circumstances just enumerated, the socket 25 would cock with respect to post 23 and thus cause slippage" and undue" arcing" between the contacts 5" and 21 as the circuit breaker opened and closed.

The combined rubbing block 17 and bearing 16 are integrally molded in their finished form. Preferably the integral bearing and rubbing

block

16, 17 is molded by impregnating under heat and pressure a fabric with a plastic, preferably of the thermosetting type such as a phenol-formaldehyde condensation product, while holding the fabric in 'a die cavity having the finished dimensions of the combined bearing and rubbing block. By thus molding the combined bearing and rubbing block, a highly "g'l'aze'd surface is obtained so that no burnishing or machining of the member is required. Further, by thus molding the said member, the location of the bearing socket 25 with respect to the rubbing surface 41 can be accurately obtained.

In assembling the breaker arm upon the bracket 7 the end 9a of spring 9 is adjusted with respect to bolt 10 until the

contacts

5 and 21 are accurately aligned whereupon nut 11 is drawn down tight to securely clamp or fix ar'm 7a and end 9a of the spring together. A rivet may be substituted for bolt 10 and nut 11. S ring 9 thereafter accurately holds the contact points in their accurately adjusted face to face coincident relationship and thebe'aring 16 seeks its position on post 21. The spring 9 thereafter maintains the bearing 16 in this position so that the breaker arm is floated on the spring 9. It should be noted that post 23 is of uniform cylin drical shape above the base of the bracket 7 so that spring 9 is the sole support for hearing 16 upon post 23. It should also be noted that the breaker arm 7a, to which spring end 9a is clamped, is parallel with the post 23, Fig. 12. Also, post 4, which supports the fixed contact 5, is positioned perpendicular with respect to the base of bracket 7. Further, the face of contact 5 is formed substantially perpendicular to the base of the bracket 7 and the face of contact 21 is substantially parallel to a plane passing through the axis of pivoting of bearing 16. Hence, when the circuit breaker arm is located with the bearing socket 25' pivotally supported on post 23 by spring 9, face to face contact of contacts 5' and 21 is assured. Thus, spring 9 serves the dual function of not only supporting the breaker arm but also tends to turn the breaker arm about post 23 and thereby supply contact pressure.

One of the important features of my circuit breaker arm is its lightness due to the channel and rib formation of the metal portion 18 and the lightness of the integral half round bearing 16 and rubbing block portion 17. Due to the lightness of my circuit breaker arm, the inertia of the arm is reduced to a minimum and similarly chattering due to rebound of the arm when the contacts come" together is reduced to a minimum and substantially eliminated.

In the form shown in Figs. 10 and 11, the position of the bearing 16a is reversed in comparison with the principal form of circuit breaker shown in Fig. 1. The bearing portion 16a is positioned between the post 23 and support arm 7a whereas in the principal form of the invention the bearing portion 16 is positioned on the side of the post 23 remote from support arm 7a. The position of the arm when the post is removed is shown in Fig. 11.

I claim:

1. In a circuit breaker, an arm having an open socket, a post, said socket pivotally engaging said post at at least two circumferentially spaced points and extending at least around said post, resilient means, an anchor for said resilient means, said resilient means pressing said socket against said post and tending at all times to swing said arm about said post, said socket being provided with a groove extending parallel to the axis of said post substantially midway between the said circumferentially spaced pointsof engagement between the socket and the post.

2. The circuit breaker defined in claim 1 wherein said resilient means comprises a flat torsion spring having one end fix'ed to the anchor, said spring being looped around said socket in spaced relation therewith and secured to the face of the arm between the socket and rubbing end of said arm. 7

3. In a circuit breaker arm comprising a socket adapted to pivotally support the arm on a post and a rubbing block adapted to engage a darn, a metal member secured to said rubbing block and socket in the form of a channel and a contact point secured to the outer end of said member, the side Walls of said channel extending generally perpendicularly away from the plane of said rubbing block and contact point and serving both as a stiffener for said metal member and as a heat radiating fin for dissipating the heat from said contact point, said metal memher having a bottom wall spanning said side Walls and having a generally flat area at said outer end, said contact point being secured to said flat area of said bottom wall, said metal member being provided with a longitudinally extending channel rib in said bottom wall, said channel rib extending from one end of said metal member to a point adjacent the contact point thereby providing said flat area on said bottom wall between the end of said rib and thg end of said member to which the contact point is secure 4. The combination defined in claim 3 wherein said channel rib in cross section takes the form of an inverted U and extends upwardly from the bottom wall of said channel member between its two upstanding side walls.

5. The combination defined in claim 4 wherein said rubbing block and socket are integral, and a plurality of rivets staggered lengthwise of said breaker arm for securing said metal contact supporting member and integral rubbing block and socket together.

6. In a circuit breaker arm, an integrally molded open socket bearing portion and rubbing block, said bearing portion being of substantially U form, the lower curved portion of which has a circumferential extent of at least 180, the upper ends of said U being defined by leg portions extending upwardly from the ends of said curved portion.

7. The article defined in claim 6 wherein said bearing socket is provided with an axial groove at substantially its mid-section.

8. In a circuit breaker arm, an integrally molded plastic bearing and rubbing block, said bearing having a circumferential extent of at least 180 and being of substantially U form with an L shaped rubbing block portion extending therefrom.

9. A circuit breaker arm comprising a molded integral plastic open socket bearing portion and rubbing block portion, a relatively thin, lightweight metal member secured to said rubbing block portion with one end of said metal member positioned adjacent said bearing portion, said metal member being in the form of a channel and a contact point secured to the outer end of said member, said channel-shaped member having a bottom wall and side walls, the side Walls of said channel extending generally perpendicularly away from the plane of said rubbing block and contact point and serving both as a stiff ener for said metal member and as a heat radiating fin for dissipating the heat from said contact point.

10. The combination defined in claim 9 wherein said metal member is provided with a longitudinally extending channel rib in said bottom wall, said channel rib extending from one end of said metal member to a point adjacent the contact point thereby providing a fiat area on said bottom wall between the end of said rib and the end of said member to which the contact point is secured.

11. The combination defined in claim 10 wherein said channel rib in cross section takes the form of an inverted U and extends upwardly from the bottom wall of said channel member between its two upstanding sides.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 19,083 Davis Feb. 13, 1934 1,171,577 Abtmeyer Feb. 16, 1916 1,831,184 Mallory Nov. 10, 1931 2,024,630 Davis Dec. 17, 1935