US2805292A - Electrical contact point assembly - Google Patents

Description

Sept- 3, 1957 N. w. cARMAN 2,805,292

ELECTRICAL CONTACT POINT ASSEMBLY Filed June 29, 1953 INVENTOR /ChoZdS l/l/ndel] rman ABY f i ATTORNEY United States Patent ELECTRICAL CONTACT POINT ASSEMBLY Nicholas Wendell Carman, Brattleboro, Vt. Application June 29, 1953, Serial No. 364,766

Claims. (Cl. 20D-30) This invention relates to an electrical contact point assembly, and more particularly, to an ignition timing mechanism for a distributor of the type comm-only used on automobiles,

In the usual automobile ignition system, the spark voltage is induced in the secondary winding of the ignition coil upon interruption of the current to the primary winding of the ignition coil by a timing switch in the distributor. This switch includes a fixed contact point and a movable contact point controlled by a cam which rotates in timed relation to the crankshaft of the engine.

In the past, the movable contact point was mounted on a pivoted member having a lateral projection, and a spring urged the mem-ber in a direction such as to cause the projection to Contact the surface of the cam. In this arrangement, the wear on the projection was severe, and since a small dimensional change in the timing switch mechanism retarded the ignition spark sufficiently to impair engine performance, it was necessary to adjust the mechanism at frequent intervals in order to get the proper timing for the ignition spark. Also, the contact points tended to burn and pit to an objectionable extent due, in part, to the pivotal mounting for the member carrying the movable contact point. As the contact points opened, the portions thereof farthest from the axis of pivot opened faster than the portions closer to the axis, and the potential on the surfaces of the points tended to concentrate on the portions which were closest together. Furthermore, the small contact area of the points gave the circuit a high resistance and allowed only a small current flow to the primary winding of the ignition coil.

It is an object of this invention to provide a contact point assembly which will allow a greater current ow, which will maintain the proper ignition spark timing for long periods, and which will be economical in the use of points.

It is a more specific object of this invention to provide a contact point assembly with a plurality of tixed contacts points and a plurality of movable contact points so that the current carried may be increased.

It is a further object of this invention to provide a Contact point assembly in which wear is reduced by cause ing a ball to bear against the timing cam and transmit motion to the movable contact points.

Still another object of this invention is the provision of a contact point assembly in which the movable contact points are caused to move in straight line paths which are at right angles to the planes of juncture between the contact points.

The above objects are attained by the contact point assembly according to this invention, one embodiment of which comprises a anged support plate adjustably positioned in the distributor adjacent to the timing cam and carrying two fixed contact points, a plunger mounted for reciprocating motion with respect to the iiange of the support plate and carrying two movable contact points, a spring urging the plunger toward the cam, and a ball transmitting motion to the plunger from the cam.

Other objects and advantages. of thisvinvention will appear as the detailed description of an embodiment there- Patented Sept. 3, 1957 of proceeds in connection with the accompanying drawings, in which:

Fig. 1 is a plan view of a distributor with the cap removed and showing a Contact point assembly according to this invention with the contact points closed.

Fig. 2 is a vertical sectional view of the contact point assembly taken along the line 2-2 on Fig. l, but showing the parts in the positions they occupy when the contact points are open;

Fig. 3 is a detail perspective view of a cylinder forming a part of the assembly shown in Figs. l and 2;

Fig. 4 is a detail perspective view of a bracket member forming a part of the assembly shown in Figs. l and 2; and

Fig. 5 is a detail perspective View of a plunger forming a part of the assembly shown in Figs. l and 2.

In Fig. l, the numeral 1 designates generally a conventional distributor including a base plate 2 upon which is mountedk a conventional condenser 6. A driven distributor shaft (not shown) passes through the base plate 2 and carries a timing cam 3. The contact point assembly of this invention is designated generally by the numeral 7.

This assembly includes a steel support plate 10 having a hole 11 which tits over a brass stud 12 projecting upwardly from the base plate 2. The position of the support plate 10 relative to the timing cam 3 is adjusted by turning the adjustment screw 13 which passes through an elongated adjustment slot 14 in the support plate 1t) down into a hole in the base plate 2. A hold screw 15 passing through a slot 16 in the support plate 10 serves to lock the support plate in its adjusted position.

Extending upwardly from the support plate 10 in the vicinity of the timing cam 3 is a flange 17 having a centrally located aperture. A tubular cylinder or sleeve 19 (Fig. 3) of brass fits snugly through the aperture in the flange 17 and through a similar aperture 22 in the steel bracket member 23 (Fig. 4). The front face of the bracket member 23 abuts the rear face 24 of the flange 17.

The sleeve 19 has a bore 20, one end of which is enlarged as indicated by the numeral 21. The body portion 25 of a non-conducting, laminated fiber piston or plunger 26 (Fig. 5) is slidably positioned inside the bore 2t) and bears against a steel ball 27, the forward end face 28 of the plunger 26 being curved as shown to correspond to the curvature of the ball 27. The forward end portion of the sleeve 19 is rolled over slightly to form a flange, as indicated by the numeral 3i?, after the ball 27 is inserted in the enlarged portion 21 of the bore 20 to retain the ball in the sleeve. In its forwardmost position, the ball 27 will normally be spaced slightly from the low points on the cam 3. The shoulder 29 at the rear of the enlarged portion 21 of the bore 2t) limits rearward motion of the ball 27.

The plunger 26 has an enlarged, rectangular head portion 31 at its rear end, which slides back and forth in the slots 32 and 33 in the top and bottom faces 34 and 35 of the bracket member 23. A stud 36 projects rearwardly from the head 31 through an aperture in a sheet steel spring 38 to position the same. The ends of the spring 38 are restrained by the bracket member 23, and the normal curvature of the spring 38 is much greater than that permitted by the parts as assembled. Consequently, the spring 3&5 urges the plunger 26 and the associated parts forwardly at all times.

A pair of fixed contact points 43 and 41 is carried by the flange 17, and a pair of movable Contact points 42 and 43V is carried by the head portion 31 of the plunger 26. Each of the contact points is made of a silver alloy and has a cylindrical body portion 44 and a securing stud 45 of smaller diameter. The securing studs of the xed contact points 40 and 41 pass respectively through the apertures 46 and 47 in the bracket member 23 and into the openings 48 and 49 in the rear face 24 of the flange 17. The securing studs of the movable Contact points 4:2 and 43 pass into openings 5@ and 51 in the forward face of the head portion 31 of the fiber plunger 26. The ht between the openings 43, 49, Si) and 51 and the studs 45' is snug, and no other securing means is necessary. iowever, additional securing means could be provided if desired.

Not shown on the drawings are wires leading from the movable contact points 42 and 43 through the head portion '51 of the fiber plunger 26 to the upper surface thereof. These wires are preferably incorporated in the fiber plunger during its formation, but they may be positioned whenever it seems most convenient. A pigtail7 wire 53 is connected to the wires in the plunger' 26 and to another lead so that in service the contact points will be in series with the primary winding of the ignition coil. The iixed contact points itl and 41 are, of course, grounded through the flange 17 and the support plate 10.

ln operation, a portion of each face 4 of the timing cam 3 bears against the ball 27 as the cam 3 rotates to force the bail 27 and the fiber plunger 26 rearwardly against the spring 3S to open the contact points 4f), 41, 42 and 43. The ball 27 is freely rotatable so that there is very little wear on either the ball 27 or the cam 3. The substantial bearing area between the end face 28 of the plunger 26 and the ball 27 reduces wear between the ball and the plunger to an insignificant amount. As the high points of the cam 3 pass the ball 27, the spring 33 forces the plunger 26 and ball 27 forwardly kto close the contacts 4t), 41, 4Z and 43.

It has been found that the new contact point assembly gives twice the current flow of the ordinary point assembly previously used in distributors, and that as a result of this excess flow, the engine becomes more efficient, using the full amount of gasoline and developing more power. Also, the contact points have less chance of pitting.

Various modifications of the embodiment of this invention, described herein as an example, will be apparent to persons skilled in the art and may be made without departing from the invention, the scope of which is defined in the following claims.

I claim:

l. A timing mechanism comprising a driven cam, a support bracket having a hole therethrough, a tubular sleeve positioned in said hole and extending toward said cam, a ball in said sleeve protruding from an end thereof toward said cam for actuation by said cam, a plunger in said sleeve having a surface at one end of a curvature corresponding to that of said bail for engagement with said ball and having an enlarged portion adjacent its other end, a spring adjacent said other end of said plunger for urging said plunger and said ball toward said cam, a first plurality of electrical contact points carried by said enlarged portion of said plunger and a second plurality of electrical contact points carried by said support bracket in position to be engaged by said first contact points when said cam is in a position which allows said spring to close said contact points.

2. ln a distributor having a base plate, a distributor shaft projecting through said base plate, and a timing cam on the upper portion of said distributor shaft, an assembly comprising a support plate, a substantially vertical flange fixed to said support plate and having'a hole therein, means positioning said support plate on said base plate for adjustment toward or away from said timing cam, a bracket carried by said flange on the side thereof' opposite that which faces said "timing cam and having a hole corresponding in size and position to said hole in said flange, a tubular sleeve positioned in said holes and extending toward said cam, a spherical ball in said sleeve protruding from an end thereof toward said timing cam for actuation by said cam, a plunger having a body portion slidably mounted in said sleeve and an enlarged head portion, said body portion having an end face of a curvature corresponding to that of said ball for engaging said ball and said head portion having a centrally located stud projecting from the side thereof opposite said body portion, a sheet metal spring having a hole penetrated by said stud and being restrained at its ends by said bracket so as to' urge said plunger and saidV ball toward said cam, two contact points secured to said head portion, one below and one above said body portion, and two contact points secured to said bracket in position to be engaged by the first mentioned contact points when said cam allows said spring to close said contact points.

3. ln an ignition timing mechanism for an internal combustion engine, a support member, a rst Contact point fixed with respect to said support member, a sleeve fixed with respect to said support member, a ball rotatably mounted in said sleeve and protruding from an end thereof, a non-conducting, laminated fiber plunger slidably mounted in said sleeve and having a concave end surface of a curvature corresponding to that of the surface of said ball for engagement with said ball, a second contact point fixed with respect to said plunger in position to engage said first contact point when said plunger is at one end of its line of travel, and biasing means urging said plunger in one direction.

4. A timing mechanism comprising a driven cam, a support bracket having a hole therethrough, a tubular sleeve positioned in said hole and extending toward said cam, a ball in said sleeve protruding from an end thereof toward said cam for actuation by said cam, a plunger in said sleeve having a surface at one end of a curvature corresponding to that of said ball for engagement with said ball, a spring adjacent the other end of said plunger for urging said plunger and said ball toward said cam, a first electrical contact point carried by said plunger and a second electrical Contact point carried by said support bracket in position to be engaged by said first contact point when said cam is in a position which allows said spring to close said Contact points.

5. In a distributor having a base plate, a distributor shaft projecting through said base plate, and a timing cam on the upper portion of said distributor shaft, an assembly comprising a support plate, a substantially vertical flange xed to said support plate and having a hole therein, means positioning said support plate on said base plate for adjustment toward or away from said timing cam, a tubular sleeve fixed to said flange in alignment with said hole and extending toward said cam, spherical ball in said sleeve protruding from the end thereof adjacent said cam, said end of said sleeve being provided with an inwardly extending radial frange of an Vinternal diameter smaller than the external diameter of said ball to hold said ball in said sleeve, a plunger in said sleeve bearing at one end against said ball, a spring adjacent said plunger for urging said plunger and said ball toward said canna first electrical contact point carried by said plunger, and a second electrical contact point carried by said flange in position to be engaged by said first mentioned contact point when said cam is in a position which allows said spring to close said contact points.

References Cited in the file of this patent Germany Feb. 24, 1934

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