US2049637A

US2049637A - Spark timer for internal combus

Info

Publication number: US2049637A
Authority: US
Publication date: 1936-08-04
Anticipated expiration: 1953-08-04

Description

Aug. 4, 1936. G. E. BAKER SPARK TIMER FOR INTERNAL COMBUSTION ENGINES Filed July 5' 1935 uw l 1N ENTOR' ATTORNEYS' n Patented Aug. 4, 1936 UNITED STATES PATENT OFFICE SPARK TIMER FOR INTERNAL COMBUS- TION ENGINES 10 Claims.

This invention relates to ignition spark timers for internal combustion engines, which timers include a breaker switch having contact points which control the sparking at the spark plug terminals of the engine, when the points separate, and has for its object a particularly simple means by which the gap between the contact points of the breaker switch remains yuniform under all conditions of the contact points, regardless of how much they are worn or burned away, or means for automatically compensating for wear of the contacts.

It further has for its object a timer in which the contact points of the Ibreaker switch remain engaged, when the breaker switch is being moved outwardly by the cam and separate during the inward movement of the breaker switch in following or moving into the low points of the cam, together with the time-lag device connected to the arm carrying one of the contact points for retarding its quick return under the action of the returning spring, while the follower of the switch is moving into the low point of the cam.

Other objects appear throughout the specification.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth 'and claimed.

In describing this invention, reference is had to the accompanying drawing, in which like Acharacters designate corresponding parts in all the views.

Figure 1 is a plan view, partly in section, of the breaker switch and its support and the cam for operating the breaker switch and -also showing the time-lag which maintains a uniform gap between the contact points, regardless of the condition of the points, as to wear and burning.

Figures 2 and 3 are diagrammatic operation views showing the operation of the breaker switch by the cam, when the follower of the breaker switch is engaged with the high point of the cam, and Figure 3 showing the position of the contacts when the follower of the switch which is on one of the contact-carrying arms moves into the low point of the cam, and the other contact-carrying arm is retarded by the time-lag means, a conventional wiring diagram for an ignition system being also shown.

This invention comprises a shaft formed with a cam and a breaker switch `support having relative rotary movement, a breaker switch carried by the support in juxtaposition to the shaft having a follower or wiper on one of the contactcarrying arms to engage a cam on the shaft, whereby the contact-carrying arms are moved, as a unit, with the contact points engaged, when the wiper or follower is coacting with the high 5 point of the cam and a time-lag or snubber device is holding the other contact-carrying arm from return movement, when the follower or wiper engages the low point of the cam, and thereby effecting separation of the contacts.

In the illustrated embodiment of my invention, the breaker arm support is stationary and the shaft rotatable and constituting the timer shaft.

I designates the shaft, which is connected in any suitable manner to the crankshaft of the engine equipped with the timer.

2 designates the breaker switch support, which is here shown as a stationary cylindrical housing mounted concentric with the shaft I.

3 designates the breaker switch which in- 20 cludes two contact-carrying arms 4 and 5 carrying respectively the contact points 6 and l. These arms are shown as pivotally mounted on a common pivot le. The arms are suitably insulated from each other and from the support 2. The contact arm 5 is here shown as carried by a base or strip 8 having a washer-like head 9 mounted concentric with the pivot. The arm 4 is mounted on the pivot la above the washer-like head 9 and is insulated from the pivot 'la by a 30 suitable bushing I0 of insulation.

The arm 5 grounds on the body or support 2 through the strip 8 or any part connected thereto.

The shaft is formed with a peripheral cam surface having high points or lobes I l and low points or valleys l2. The timer here shown is for a six cylinder engine, and hence, there are six lobes and six valleys. The lobes Il are of Very short radii or low height compared with the lobes used in conventional timers of the type in which the contacts are separated by the lift of the cam. The tops of the lobes are comparatvely wide. Also, the face of the wiper is wide. The low height lobes and valleys are practically or resemble lthe rounded corners and sides of a hexagonal shaft. This results ina comparatively longer dwell period or time the contacts are engaged and a shorter period that the contacts are separated, than in timers where the contacts are separated by the lobes or lifts of the cam, because when the wiper clears entirely one lobe and drops on the bottom of the Valley, it is kimmediately picked up by the next lobe. The reasons or advantages of the longer dwell period or shorter spark period are well known. Also, the distance in a radial direction between the high and low points determine and fix the width of the gap between the points. This, when accurately determined, is always fixed or the manufacturer can grind oi the points to the proper height for the particular type of engine in which the timer is to be used.

The breaker switch is arranged so that it or the arm 4 thereof extends crosswise at one side of the shaft I or the cam surface, and is provided with a follower or wiper I3 of insulation, which coacts with the cam. The breaker switch is held with the follower against the cam and with the contacts engaged by suitable spring means here shown as a spring I4, acting on the contact arm 4 to hold its follower against the cam, and a spring I5 acting on the contact arm 5 to hold the contact point 1 against the contact point 6 or tending to close the gap after the contacts have been separated. The spring I4 shown is a fiat strip suitably anchored at I6 to the arm 4, extended around the pivot 1a and anchored or pressed at its other end against a conductor strip I1 which in turn is connected to a wire binding device I8. As the spring I4 is of steel, it is enclosed in a copper wrapper I9 in order to increase the conductivity thereof. The spring I5 is here shown as a coil spring.

The contact 1 is carried by a resilient strip 2li lying flatwise on a backing strip 2I, the strip being anchored at one end at 22 to the backing strip and its other end, which carries the contact 1, being capable of a slight yielding or cushioning movement. This construction compensates for slight variation in the cam points.

In the operation thus far described, during the rotation of the shaft, a high point or lobe II of the cam engages the follower I3, and the arm 4 moving outwardly about the pivot 1a, and because the contact points 5, 1 are engaged, the arm 5 is also moved outward, as a unit, with the arm 4, and in the event the backing strip 2I is limited in its movement by the stifening of the spring or by engaging a stop on the support 2, the strip 29 carrying the contact 1 can have a slight yielding or compensating movement. This outward movement of both arms 4, 5, is against the action of the springs I4, I5. When during rotation of the cam, a low point or valley I2 moves under the follower I3, both springs I4, I5 tend to react. However, the movement of the arm carrying the contact 1 is retarded, as hereinafter described, permitting the contact 6 to separate from the contact 1 to form the jump gap. During the use of the timer, the points burn off and hence the distance or gap between them will gradually increase, if means were not provided for maintaining a uniform gap. This means, as here shown, is what for convenience may be called a momentary retarder connected to the arm 5 to restrain its movement under the inuence of the spring I5.

The time-lag, as here shown, is a snubber or dash-pot, the movable member of which is connected to the strip supporting the breaker switch member 5. The dash-pot includes a cylinder carried by the breaker switch or body 2, a plunger 26 movable in the cylinder and having a rod 21 connected through a suitable coupling 28 to an arm 29 on the strip 8. As the cylinder 25 is arranged in horizontal position and contains a fluid, it is formed with a verical upright part 3i] and the rod 21 is formed with an angular portion extending upward through the vertical part 30 of the dash-pot cylinder. The fluid is filled into the dash-pot through the upright part 30 and hence owing to the upright part 30, there is a reserve supply at all times to completely ll the cylinder 25. Also, this construction avoids the use of packed joints or glands. The upright part 30 is provided with a suitable cover 30. The plunger is provided with suitable passages or rits the cylinder with suiiicient looseness to provide a restricted passage for the iluid to pass from one side of the plunger to the other, and in so doing, retards the movement of the plunger, and hence the movement of the breaker switch arm 5 connected to the plunger. The full amount of this movement is the distance between the full line and the dotted line positions of the plunger 26 (Figure l). The conventional wiring diagram is shown in connection with Figure 3 in which 4I) is a distributor; 4I a distributor arm movable successively into engagement with terminals 42 connected by wires to the spark plugs of the engine. This distributor, as will be understood, is a head mounted above the breaker switch support 2 with the shaft of the distributor arm 4I coupled to the end of the shaft I in the usual manner. 43 designates the primary circuit wire leading from the battery 44; 45 and 46 the primary and secondary coils of the transformer or spark coil, the secondary coil being connected by a wire 48 to the distributor arm III. The wire 43 of the primary circuit is connected to the circuit breaker arm 4 and is completed through the contact points 6 and 1 and a ground through the spring I5. Obviously, when the breaker switch is moved into the position shown in Figure 2, when the follower I3 is engaged with a lobe or high point II of the cam, both breaker arms 4, 5 will move outwardly, as a unit, and the contact points S, 1 will separate when the follower I3 moves into a low point or valley I2 of the cam, as shown in Figure 3. During the outward movement of the breaker arm 4, the contact arms engage, the plunger 2G of the dash-pot will be moved into the dotted line position (Figure l) and when the contacts 6, 1 separate, as shown in Figure 3,the return of the arm 5 carrying the contact 1 under the reaction of the spring I5 is delayed by the movement of the plunger in the cylinder, so that the contact points 6, 1 are separated and the circuit broken, causing a spark to occur in one of the spark plugs. Under actual working conditions, the spring I5 does not have time to react against the retarding or snubbing eifect of the dash-pot but the arm 4 carries the point 6 up to the point 1. If the points 6, 1 wear or burn off, then the spring I5 does have time to react, as the movement of the arm 4 is fixed by the cam lobes II, and in reacting resets the arm 5 against the resistance of the dash-pot in a position where the points 6, 1 are in contact, when the wiper rides out of the valleys of the cam. Also, the wear of the wiper is likewise compensated for as both arms 4, 5 will change their position, as a unit, as the wiper wears, the plunger changing its initial position under the reaction of the spring I5.

In other timers, the separation of the contacts is effected by the use of high points of cams and the contact points are again brought together by the follower or wiper entering the low point or valley of the cam. Hence, the operation, in so far as the separation of the contacts is concerned, in this timer is directly opposite that of the conventional timer, and furthermore, owing to this operation, and the time-lag, the gap between the points 6, 1 is always the same, as initially adjusted.

What I claim isz- 1. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch carried by the support eccentric to the shaft and comprising two contact-carrying members mounted to have a bodily movement, as a unit, and relative movement toward and from each other, the shaft having a cam having high and low points, a wiper on one of the contact members coacting with the cam, the high point of the cam serving to move the members, as a unit, with the contacts engaged, spring means acting on the breaker switch to cause the wiper to follow the cam and for yieldingly resisting relative movement of said member` to separate the contacts, and means for resisting one of said members from return movement by said spring means when the wiper enters the low point of the cam, thereby effecting a momentary separation of the contacts.

2. In a spark timer for internal combustion engines, a shaft, a breaker switch support having relative rotary movement, a breaker switch carried by the support including two contact-carrying members, one member being separable from the other to form a gap and means for effecting relative movement of the contact members for engaging and separating the contact members including coacting cam parts on the shaft and the breaker switch and further including a device for compensating for wear of the contacts and automatically maintaining the amount of separation uniform and thus maintaining a uniform gap regardless of the wear and condition of the contacts.

3. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch pivotally mounted on the support and extending across and at one side of the shaft and including two members mounted to have relative pivotal movement, said members carrying contacts, the shaft having a cam formed with high and low points and one of the members a follower engaging said cam, spring means for resisting such relative movement of the members and holding one member with the follower against the cam, all whereby the two members are movable, as a unit, when the contacts are engaged by the high points of the cam, and ref tarding means for retarding the return movement of the other contact member when the follower of one contact member is moved by the spring means into the low point of the cam.

4. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch pivotally mounted on the support and extending across and at one side of the shaft and including two members mounted to have relative pivotal movement, said members carrying contacts, the shaft having a cam formed with high and low points and one of the members a follower engaging said cam, spring means for resisting such relative movement of the members and holding one member with the follower against the cam, all whereby the two members are movable, as a unit, when the contacts are engaged by the high points of the cam, and means for retarding the return movement of the other contact member when the follower of one contact member is moved by the spring means into the low point of the cam, said means including a dash-pot.

5. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch carried by the support eccentric to the shaft and comprising two contact-carrying members mounted to havev a bodily movement, as a unit, and relative movement toward and from each other, the shaft having a cam having high and low points, a wiper on one of the contact members coacting with the cam, the high point of the cam serving to move the members, as a unit, with the contacts engaged, spring means acting on the breaker switch to cause the wiper to follow the cam and for yieldingly resisting relative movement of said member to separate the contacts, and means for retarding the return movement of the other member by said spring means when the wiper enters the low point of the cam.

6. In a spark timer for internal combustion engines, a shaft, a breaker switch support having relative rotary movement, a breaker switch carried by the support including two contactcarrying members, one member being separable from the other to form a gap and means for effecting relative movement of the contact members for engaging and separating the contact members including coacting cam parts on the shaft and the breaker switch and further including a device including a dash-pot, for compensating for wear of the contacts and automatically maintaining the amount of separation uniform and thus maintaining a uniform gap regardless of the wear and condition of the contacts.

7. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch carried by the support and comprising contactcarrying members having relative movement for separating and bringing together contacts, the shaft being formed with a cam having a series of high and low points, one of the contact members having a follower movable along the cam, spring means tending to hold the members with their contacts engaged and to press the follower against the cam, and means for momentarily delaying, during each separation of the contacts, the return of the other movable member under the influence of the spring means, when the follower of the one member is moving into the low point of the cam, and thereby forming the gap between the contacts.

8. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, the shaft being formed with a cam having a series of high and low points, a breaker switch carried by the support and having a follower coacting with the cam, the high points of the cam operating to hold the contact points of the breaker switch together and the low points in the cam permitting said contacts to separate to form the gap between the contacts.

9. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch carried by the support and including separable contact members, the breaker switch and the shaft having coacting cam means for moving the contact members of the breaker switch in one direction, as a unit, and holding the contacts thereof engaged and permitting relative movement of the contact members and hence separation of the contacts during movement in the opposite direction of the breaker switch.

10. In a spark timer for internal combustion engines, a shaft, and a breaker switch support having relative rotary movement, a breaker switch carried by the support and including separable contact members, the breaker switch and 10 the shaft having coacting cam means for moving the Contact members of the breaker switch in one direction, as a unit, and holding the contacts thereof engaged and permitting relative movement of the contact members and hence separation of the contacts during movement in 5 the opposite direction of the breaker switch, spring means for resisting relative movement ot the contact members to separate the contacts, and snubber means opposing said spring means.

GEORGE E. BAKER.