US2635150A

US2635150A - Ignition timer assembly

Info

Publication number: US2635150A
Application number: US179470A
Authority: US
Inventors: William H Spang
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-08-15
Filing date: 1950-08-15
Publication date: 1953-04-14
Anticipated expiration: 1970-04-14

Description

April-4, 1953 w, SPANG 2,635,150

IGNITION TIMER ASSEMBLY Filed Aug. 15, 1950 2 SHEETSSHEET l JNVENTOR. W/LL/AM h. SPA/V6 11, 3 93%,, idzc (2;

April 14, 1953 w SPANG v 2,635,150

Filed Aug. 15, 1950 IGNITION TIMER ASSEMBLY 2 SHEETS-SHEET 2 I N V EN TOR. W/[Ll/M/ H. SPA/V6 Patented Apr. 14, 1953 UNITED STATES PATENT OFFICE 6 Claims.

The present invention relates to improvements in ignition timers, particularly for distributors such as those used in automobile ignition systems.

In the ignition systems commonly used for automobiles, the current to the primary of the induction coils used to produce the high tension ignition spark is controlled and timed by the timer switch or points in the distributor. The contact points for the primary circuit control switch are generally carried by a point assembly including a supporting or bracket plate adjustably mounted in the distributor casing, one of the points being fixed to the support plate and the other carried by a contact arm pivoted to a post which is fixed either to the bracket plate or to some part of the distributor underlying the bracket plate. The contact arm unit has an insulating bushing which forms an insulating bearing between the arm and the pivot post, a fiber cam follower piece projecting laterally from the arm and a strip spring flexed around the pivot end of the arm with one end bearing against the contact arm and the other end disposed against the nut of a binding post which is mounted on but insulated from the support plate. This spring urges the contact arm in a direction tend-' ing to close the contact points, while a rotary timing cam, having the general shape of a regular polygon with rounded corners, moves the arm to open the points as the cam follower rides up the successive corners thereon. The timing cam itself is mounted on the distributor shaft driven by the timing shaft of the engine so that one turn of the rotary cam corresponds to two turns of the flywheel according to general practice. In the case of a six-cylinder engine the cam is of a hexagonal shape; for eight cylinder engines, octagonal.

For proper engine ignition, it is necessary that the break, when the spark voltage is induced in the coil secondary, occur at the proper time. Also, to prevent excessive duration of current in the coil primary circuit with resulting heating and burning of the contact points, it is necessary that the dwell angle which determines the duration of primary current, be not excessive. In the case of the usual distributor contact arms of the prior art, the cam contacting end of the follower wears, causing a shortening of the effective length of the follower, and hence retarding of the spark, due to a delay in the occurrence of the break. Moreover, this wear is accentuated by the rounding of the corners at the end of the cam follower due to the changing angular disposition of the cam faces with respect to the fol-'- lower as the cam rotates. Thus, in addition to retarding the spark, there occurs an increase in the angle due to the fact that the points close earlier and break later than normal. Hence the primary current generally tends to flow longer than it should, with the ultimate result of arcing and heating at the points with attendant burning. In addition to the ordinary Wear, which would occur due to the spring pressure forcing the cam follower against the cam, further wearing is often caused by a binding effect between the insulating bushing and the pivot about which the contact arm moves. This binding may tend to develop due to swelling of the fiber under certain conditions or by the presence of dirt or other foreign matter between the pivot and the fiber bushing. This binding effect, in addition to causing further wear on the cam follower, also tends to make the action of the contact arm sluggish.

In the common automotive practice, the rotating distributor cam clears the cam follower during a part of the time that each cam face is passing the follower, so that the points are held closed under the bias of the spring. As the cam rotates the disposition of the cam face changes and the cam comes to bear on the follower, thereby moving the contact arm away from the cam against the spring bias to open the points, and break the primary circuit. This causes a high voltage, suitable for ignition spark purposes, to be induced in the secondary winding of the spark coil. The contact arm continues to move away from the cam until the cam corner or lobe passes the follower, whereupon the follower rides a new cam face, allowing the contact arm to move toward the cam under the closing bias of the spring until contact is again made between the points to close the primary circuit. As the arm contacts the fixed point, further movement under spring bias is prevented, and the period of clearance between cam and follower is begun. This cycle is repeated between the corresponding points on two successive cam faces. The portion of this cycle between the make and break times is generally described in terms of the degrees of corresponding rotation of the flywheel, commonly, in automotive practice, twice the amount of distributor cam rotation, and is called the dwell angle.

For a six-cylinder engine with a dwell of about 35 on the flywheel, the points are set to have a clearance when open of about .020 to .022 of an inch; an eight-cylinder engine, with a 3 dwell angle of about 30 in the flywheel, with a point setting of about .015 of an inch.

Generally the loss of a thousandth of an inch in the point of setting due to wear of the cam follower represents about 1 on the flywheel for the retarding of the firing. This point setting usually may change between .003 and .004 of an inch before the lateness of firing results in objectionable engine performance, necessitating resetting of the points. However, it has been found that the point setting may change within a mater of a few days after an adjustment to an extent where late firing or late spark does become objectionable. Also, it has been found that cne of the major causes of point burning is the increase in the dwell angle due to the wear in the cam follower. It has been found that by the use of the invention herein described, the point setting may be maintained substantially constant for the life of the points with no need of further servicing for resetting due to wear. It has also been found that in consequence of the elimination of the excessive wear of the cam follower, and hence of minimizing the change in the dwell angle, the life of the points it substantially increased. Further, it has also been found that the device of the present invention retains a freer action substantially throughout the life of the points.

One of the main objects of the present invention is the provision of an ignition point assembly which will maintain the contact point setting for a period of time increased substantially over that of present assemblies. Another object is the provision of an ignition point assembly having a contact arm with a freer action than that of prior devices, which maintains a free action substantially throughout the life of the device. Another object is the provision of a contact arm in which the tendency of the arm to bind on its pivot is substantially eliminated. Another object is the provision of an ignition point assembly in which the tendency of points to burn, due to increased dwell angle, is substantially decreased.

With the above and other objects in view, which will be apparent from the detailed description which follows, the invention consists in certain novel features of constructicn and combina tion of parts which will be readily understood by those schooled in the art t which the invention appertains.

In the drawings, which illustrate an embodiment of the invention- Fig. l is a plan view of my ignition point assembly, with the points closed;

Fig. 2 is a horizontal sectional view of the ignition point assembly taken along the line 2-2 of Fig. 3, showing the points open;

Fig. 3 is an elevational view corresponding to Fig. 1, partly in section taken along the line 3-3 of Fig. 1;

Fig. 4 is a plan view corresponding to Fig. 1, showing a form of my invention provided with oiling means which was omitted in Figs. 1 to 3 for the sake of clarity;

Fig. 5 is a plan view showing another form of my invention; and

Fig. 6 is a fragmentary elevaticnal view taken along the line 6 of Fig. 5.

In the form of my invention shown in Figs. 1 to 3, inclusive, a support or bracket plate I!) carries a bracket arm H for the fixed contact point 12, a bracket arm is for the binding screw l4 insulated by the fibre spacer l5 and a pivot post is for the support of a contact arm unit, indicated by the general reference numeral ii. The support plate It is adjustably held in the distributor by screws [8 extending through adjustment slots i9 into a base plate (not shown), which is usually the automatic spark advance plate. A pin-like projection 28 of the pivot post I6 extends through the support plate H3 into a correspondingly placed aperture of the base plate and in setting the point the entire support plate H3 may be swung about pin 28 as a pivot within limits dictated by the length of slots id. The structure thus far recited is one commonly used in ignition point assemblies. I'he contact arm unit it is of the general form of arms used in the prior art, comprising a metal arm piece 21 with flanged longitudinal edges which carries a contact point 22 at one end and has at the other end a sleeve 23 extending through and beaded over the flanged part of the arm, a spacer sleeve 23a between the flanges and around sleeve 23, and an insulating bushing 2t pressed into the sleeve 23.

Between th contact point 22 and the pivot portion the contact arm carries a fibre cam follower 25 of the general L-shape hitherto used, having a fiat base 25 secured to the arm piece 2| and a lateral projection 2? disposed toward the rotary distributor cam 28, shown b dashed lines in outline form. In my contact arm unit, however, the fibre cam follower 25 is provided with a spring metal cam bearing piece 30 held in place from vertical displacement on the base 25 by an insulating saddle piece 35 with edges overhanging the sides of the base. Bronze has also been found to serve quite well for the strip Bil, but other metals may be used. A rivet 32 extending through the saddle piece, a clearance hole in the bearing strip, the cam follower base 26 and through the arm 91 holds these components on the arm. The bearing strip 38 is maintained from lateral displacement by its flanged end 33 which overhangs the cam follower base and also by the formation 3 somewhat U- shaped to protect the cam follower end surface and corners, and having a flat portion disposed between the cam and follower. As shown in Fig. 1, when the middle part of one of the sides of the cam 28 is disposed toward the cam follower the points are closed by the action of spring 35, the bearing face of formation 3t being held against the cam by the elasticity of the bearing strip itself and there is a small clearance distance between the end of the cam follower and the bearing strip. Thus, the cam bearing strip St is in constant contact with the rotating cam 28, and the bearing strip formation 3d is pushed back against the cam follower displacing the contact arm in the usual fashion to open the points, as shown in Fig. 2.

My arm differs also in having the insulating bushing 24 provided with a pivot pin 36 held in the closed end 3? of the bushing and extending downward into an axial bore 38 provided in the pivot post it. Clearance is provided between the pivot post and cylindrical wall of the insulating bushing, the main bearing surfaces being those of the pivot pin 36 and the bore 38. For use with distributors in which the contact arm pivot post is carried by the automatic spark advance plate rather than by the bracket plate, my invention may be used, of course, by providing a pivot post having an axial bore and dimensions adapted to receive a contact arm such as that above described.

By this pivot arrangement the bearing surface, and hence pivot friction, is greatlyreduced from that of the prior art wherein the large outer cylindrical periphery of the pivot post bears on the inside of the inner bore of the fibre insulat ing bushing. Also, lubricant in the axial bore 38 comes in contact only with the metal of pivot post H3 and pivot pin 35. Thus, there is no fibre pivot bearing surface to swell and cause binding. Moreover, as the pivot post bore does not extend entirely through the post, the oil originally placed therein remains throughout the life-of the points. Hence a freer pivoting action is obtained and maintained in my timer. In Fig. 3 the bottom of the bushing Ed is shown bearing on the collarlike flange of pivot post it. The vertical position of arm unit I? may be determined in this fashion or by other bearing relationsthe end of pivot pin 36 on the bottom of bore 38, the inner surface of bushing end 31, or the bottom of bushing 2 bearing on some structure of the automatic spark advance plate when the latter carries the pivot post. The spring 35 also may be adapted to maintain the vertical position of the contact arm unit.

In Fig. 4, in addition to the structure of Figs. 1 to 3 inclusive, there is shown a cam face oiling device comprising an oiling wick 40 of any suitable material such as felt, for example, which will absorb and retain a lubricating oil, and which is carried and held in contact with cam 28 by means of a spring metal clip M fixed at the end 42 to the arm 2| and crimped around the wick at 43. If desired, the clip 41 may be made an integral extension of the bearing strip 39. This lubrication means serves to lessen further the wear in the arm camming system.

In the form of my invention shown in Figs. 5 and 6, a point assembly of the ordinary type, as used in the prior art, is shown provided with an adapter arm which furnishes the cam lubricating and bearing strip elements of my invention. In general the structure is that described in Figs. 1 to 4 inclusive, but here the contact arm unit i! is shown with the ordinary insulating bushing 56 of the prior art which is pressed into the sleeve 23 and which has a bearing surface bearing on the flange portion of the pivot post and the surface of the bore bearing on the cylindrical surface of the pivot post. In this case the upper end of the pivot post has a bore 52 axially located to receive the pivot end 53 of the adapter arm 54 carrying at its other end a cam follower bearing piece 55, shaped similarly to the formation 35 of the bearing strip Sit in Figs. 1-4, to protect the end of the cam follower 2a. A wick 56 similar to the wick to above described is held on the arm 54 by a metal clip 5? crirnped about the wick and arm. The shape of the adapter arm 54 must be such that the adapter arm clears the metal arm piece 21 of the contact arm unit [1. The new contact arm pivoting system of Figs. 1-4 above described may be combined with the bearing strip and cam lubricating features by the use of a structure such as the arm 54 carrying the bearing strip 55 and lubricating wick 56, by extending the end 53 downward through the closed end 3'! of the bushing 25 to take the place of the pivot pin to fixed in the bushing. By means of these structures in which the bearing strip and lubricating wick are carried by an arm, such as arm 54, old type contact arm units of the prior art may be used in an ignition timing point assembly to maintain a point setting substantially constant for the life of the points.

An-old type assembly is prepared to receive an adapter arm by drilling an axially concentric bore 52 in the existing pivot post to receive the pivot end 53 of the adapter arm 54. This provides the important bearing strip 'means for preventing objectionable change in the camming system dimensions, with the further assurance against undue wear available in the cam lubricating Wick. The old type timer point assembly may be provided further with the new pivot means by removing the old insulating bushing (designated 58 in Figs. 5 and 6) and substituting the new type pivot bushing (of Figs. 1-4) carrying the adapter arm structure 53-51 with the pivot end 53 of the adapter arm 54 serving as the pivot pin, designated 36 in Figs. 1-4, and having the pivot post to receive the pivot pin. Similarly, the pivot post of old type timer assemblies may be provided with a bore 38, and a contact arm unit H, such as that shown in Figs. 1-4:, may be substituted for the old arm unit.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

I claim:

1. A rotary cam actuated ignition timing device including an axially bored pivot post and a contact arm unit compirsing a rigid metal arm carrying a contact point, an insulating cam follower on the arm, an insulating sleeve carried ,by the arm and disposed about said pivot post with circumferential clearance, said sleeve being closed at one end, a spring metal cam bearing strip overlying the cam-ward surface of said cam follower, and a cam bearing strip support arm carrying said bearing strip, one end of said support arm being fixed in the closed end of said sleeve and extending coaxially therethrough into the bore of said post as a pivot pin.

2. A rotary cam actuated ignition timing device including an axially bored pivot post and a contact arm unit comprising a rigid metal arm carrying a contact point and a cam follower, an insulating sleeve closed at one end carried by said metal arm, said sleeve being disposed about said pivot post with circumferential clearance, and a pivot pin axially aligned in said sleeve and having an end fixed in the closed end of the said sleeve, the other end of said pin pivoting in the bore in said pivot post.

3. In a cam actuated ignition timing device having a stationary contact point, a pivot post and a contact arm unit pivotally mounted on the post, a contact arm unit including a rigid metal arm; means carried by the metal arm for pivotally mounting said arm to said pivot post, said means being adapted to insulate said arm from said post; a contact point on said arm disposed to contact said stationary point; a cam follower of insulating material having a base fixed on said metal arm and a projection on the base extending outward from said metal arm; a metal cam bearing strip having one end formed to overlay the cam-ward surface of said cam follower projection, and insulating means mounting the other end of said bearing strip to said metal arm.

4. In a rotary cam actuated ignition timing device including a stationary contact point, an axially bored pivot post and a rigid contact arm unit carrying a second contact point, an insulating cam follower, and an insulating sleeve supporting said contact arm unit and pivoting on said post; a cam bearing support having one end pivoting in the axial bore of said pivot post and a metal cam bearing strip carried by the other end of said cam bearing support and overlying the cam-ward surface of said follower.

5. For a rotary cam actuated igintion timing device having a pivot post and a rigid contact arm pivotally mounted on the post and provided with a cam follower, a device for maintaining the timing setting comprising a support arm with one end adapted for insertion in an axial bore of the pivot post, and a metal cam bearing strip carried by the said support arm, said strip having a portion adapted to overlie and conform to the shape of the cam-ward end of said cam follower. 2Q

6. For a rotary cam actuated ignition timing device including a pivot post and a contact arm unit pivotally mounted on the post, a contact arm unit comprising an insulating bushing adapted to be positioned about the pivot post, a rigid metal arm piece carried by said bushing, a cam follower extending from the arm piece, a contact point on the arm piece, and a metal cam bearing strip insulated from and carried on said arm piece, said bearing strip having a por-- tion adapted to overlie and conform to the shape of the cam-ward end of said cam follower.

WILLIAM H. SPANG.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,793,37'5 Schafer Feb. 17, 1931 2,191,087 Spengler Feb. 20, 1940