US2863011A - Dual point circuit breaker having simplified spark advance mechanism - Google Patents

Description

M. MALLORY 2,863,011 DUAL POINT CIRCUIT BREAKER HAVING SIMPLIFIED SPARK ADVANCE MECHANISM Filed Aug. 28, 1957 United States Patent O DUAL POINT cnzcorr BREAKER HAVINGSIM- PLIFIED SPAR-K ADVANCE MECHANISM Marion Mallory, Detroit, Mich., assignor to The Mallory Research Company, Detroit, Mich., a corporation of Michigan Application August 28, 1957, Serial N 0. 680,847

Claims. (Cl. 200-27) This invention relates to engine ignition systems, and particularly to dual point circuit breaker mechanisms employing tWo sets of circuit breaker contacts, having overlapping closure periods. The invention is an improvement on the system and apparatus disclosed in U. S. Patent No. 1,663,207, issued March 20, 1928.

In the ordinary circuit breaker a single electrical switch both closes and opens the circuit. In the dual point ignition system there are two electrical switches, one closing the circuit and the other opening it. There is never any flashing in the contacts that close the circuit because they never open the circuit. Naturally there isnever-any corrosion, scale or pitting in the contacts. that close the circuit and the current always flows freely through the primary winding of the coil, saturating or magnetizing the coil core to its maximum. During the time both circuit breakers are closed there is, bound to be a free flow of primary current through the coil because the surface resistance of two sets of contacts is only one-half the surface resistance of one. Therefore, a good electrical circuit is always established.

With todays high compression eight cylinder engines it is very necessary to have a hot, high voltage spark. To obtain this with a single circuit breaker, the circuit breaker must be gapped closely, andwith present day 12- volt electrical systems this causes excessive flashing of the circuit breaker and short life. With dual circuit breakers, a wide spacing can be used, still obtaining a long duration of coil saturation time or dwell with no excessive flash- Objects of the present invention are to provide an overlapping dual point ignition system wherein:

(1) Rotary timing advance plates and vacuum-piston type advance mechanisms are eliminated while still attaining desired spark advance for better fuel economy at light engine loads.

(2) Spark advance is attained electrically rather than mechanically so as to reduce the time lag between change in engine load and corresponding change in spark ad- Vance, the arrangement being such as to obtain increased fuel economy and freedom from advance plate sticking and failure of mechanical vacuum advance structures.

(3) At idle or low manifold vacuum when the engine is under heavy load the overlapping dual point principle is in operation, with the circuit breaker which opens last doing the timing of the engine. When manifold vacuum becomes high and the engine is under light load the circuit breaker which opens last is disconnected through a vacuum-operated electric switch. This automatically causes the breaker which opens first (approximately eight degrees ahead of the breaker which opens last) to control the timing of the engine, therefore automatically advancing the ignition timing for light engine load and decreasing contact dwell or coil saturation time; because only one breaker is in operation at light engine loads the average breaker point temperature is decreased so as to increase contact point life.

(4) The circuit breaker components may be constructed as relatively low cost items by elimination of the relatively costly movable advance plate and vacuum piston type advance mechanism therefor.

Other objects of this invention will appear in the following description and appended claims, referencetbeing had to the accompanying drawings forming apart ofthis specification wherein like reference characters designate corresponding parts inthe several views.

In the drawings, the single figure is a plan view of a distributor constructed accordingto the present invention with its cap removed for illustration purposes, said distributor being shown in position of use relative to the spark coil, condenser, and vacuum-operated switch unit for controlling the distributor action.

Before explaining the present invention in detail, it. is to, be understood that the invention is not limited, in its application to the details of construction and arrangement of parts illustrated in the accompany drawings, since the invention is capable of other embodiments and of. being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein isfor the purpose of description and not of limitation.

In the drawings there is shown an internal combustion engine ignition system including a line 10 leading from the conventional ignition switch (not shown) to terminal 12 for the primary winding of a single induction spark coil 14. The other primary winding terminal 16 is connected through lines 18 and 19 to condenser 20 and circuit breaker terminal 22.

Terminal 22 is exteriorly insulated and projects through metallic distributor housing 24 into electrical connection with a line 26. Housing 24 is provided with the conventional Bakelite cap (not shown) and rotor-segment structure for distributing secondary current from coil 14 to the engine spark plugs. Secondary current is carried from the coil secondary to the distributor cap via line 25.

Line 26 engages an insulating washer 27 located on ear 28 of a metallic mounting bracket 29. Bracket 29 is fixedly secured to a subjacent supporting plate 30.by means of screws 31, said plate 30 being fixedly carried by metallic casing 24.

A second insulating washer 32 is positioned against the other face of ear 28 so as to receive one end of a metallic leaf spring 33, the assembly of elements 33, 32,. 27 and 26 being supported on car 28 by means of a rivet 35. The other end of spring 33 is secured to a metallic circuit breaker arm 36, which is mounted for pivotal movement on a pin 37 carried by plate 30. Arm 36 includes a fibrous dielectric member 39 and a metallic member 34. A pair of rivets 7 (only one of which is visible) secure spring 33 onto the breaker arm and establish a current path between the spring and arm member 34.

Arm member 34 carries a contact point 40. Bracket 29 is provided with an upstanding car 41 which carries a registering point 42.

Opening and closing of points 40 and 42 is accomplished by means of the conventional distributor shaft 43 having a cam surface or lobe for each of the engine cylinders, the illustrated shaft having eight lobes 44 through 51 so as to be used with an eight cylinder engine. It will be appreciated that the number of lobes could be varied in accordance with the number of engine cylinders since the invention is capable of use with engines having any number of cylinders. During rotation of shaft 43 cam surfaces 44 through 51 ride on extension 52 of arm 36, with spring 33 biasing said arm toward the axis of shaft 43 so as to maintain extension 52 against the adjacent cam surface, the arrangement being such that points 40 and 42 are opened and closed in accordance with the rotated position of shaft 43.

A second set of contact points 40, 42' receives current from an insulated terminal 54, which is connected with terminal 22 by means of conductor 55. The mounting mechanism for points 40', 42 is similar to that employed in conjunction with points 40, 42 and similar reference numerals are therefore used.

Housing 24 carries a brackeet 57, which fixedly mounts a metal casing 58. Casing 58 includes two cup-shaped sections 59 and 60, between which is clamped a movable rubber diaphragm wall 61. A cylindrical forcetransmitting arm 62 is fixedly secured to diaphragm wall 61 and slidably extends through an opening in section 59 into a position overlying the breaker arm 36. The right end of arm 62 is turned downwardly at 63 to freely engage the right face of arm 36. V

The end wall of section 60 is provided with an opening which mounts one end of a vacuum line 64, the other end of said line being connected to a fitting 85 screwed into the wall of a carburetor 66. Fitting 85 communicates through opening 67 with the space just upstream from throttle valve 68, the arrangement being such that as the throttle valve is opened line 64 is put in communication with the engine inlet manifold. The vacuum within the manifold is thereby effective through line 64 to move wall 61 to the left (to its illustrated position) against the action of spring 33. Spring 33 is so calibrated that nine to eleven inches of mercury manifold vacuum is required to move wall 61 to the left (as illustrated) for moving contact 40 away from contact 42. Spring 33 may be replaced with a differently calibrated spring to obtain different switchoperating vacuums.

Operation of the apparatus is such that when the manifold vacuum is low switch contacts 40 and 42 are closed so as to close the circuit through conductor 26. Some of the spark coil primary current into terminal 22 therefore flows through conductor 55 to terminal 54; the remaining spark coil primary current flows from terminal 22 through line 26, and eventually through points 40, 42 to plate 30 and out to ground. The current at terminal 54 flows through line 26, and eventually through points 40', 42' to plate 30 and out to ground.

The mounting mechanisms for points 40, 42, 40' and 42' are so positioned that points 40 and 42' close before points 40 and 42, as for example by about eight shaft degrees. For approximately the next fifteen degrees both sets of points are closed, for approximately the next eight degrees only points 40, 42 are closed, and for the last fourteen degrees both sets of points are open. This arrangement causes the primary coil circuit to be closed by points 40', 42' and to be opened by points 40, 42 with an overlapping period when both sets of points are closed. The arrangement is advantageous by reason of minimum flashing, minimum corrosion, minimum scale or pitting, and low point surface resistance, while increasing dwell time or coil saturation time to increase coil efficiency.

At cruising speeds under low load conditions fuel economy is enhanced by advancing the spark from its position at high load conditions. The manifold vacuum is increased at low load conditions so as to act through diaphragm 61 and arm 62 to open the circuit through contacts 40 and 42. As a result all of the current at terminal 22 must flow through points 40', 42. Since these points open approximately eight degrees before points 40, 42 the spark is automatically advanced by eight distributor shaft degrees or sixteen engine degrees, which is the most favorable advance for enhanced fuel economy.

It will be noted that the change in spark advance is accomplished by a direct connection device between diaphragm 61 and breaker arm 39 rather than through a linkage system operating between a vacuum unit and rotary advance plate or other mechanical means. As a result the change in spark advance occurs almost instantaneously after change in manifold vacuum with no time lag due to mechanical play of parts. Additionally all rotary support structure for the advance plate is eliminated so as to provide a relatively simple low cost construction. A piston or other type of pressure responsive movable wall structure can be employed in place of diaphragm 61 if desired. With either the diaphragm construction or the piston construction the mechanism can be constructed as a relatively low cost structure which gives trouble free performance over a long service life. It can be utilized both with distributors having the conventional centrifugal advance and with distributors not so equipped.

I claim:

1. In an ignition timing system for an internal combustion engine mechanism for interrupting spark coil primary current comprising a fixed support structure; first and second fixed contacts carried by said support structure; first and second breaker arms movably carried on said support structure; third and fourth contacts carried by the breaker arms in registry with respective ones of the first and second contacts; spring means urging the breaker arms to positions wherein the two sets of contacts are closed; a distributor shaft having cam surfaces engaged with the breaker arms for sequentially opening the contacts; a fixed casing having a movable wall; conduit means putting the interior of said casing in communication with engine intake vacuum to as to put the movable wall under control of the vacuum force; and an arm extending from the movable wall to a releasable pressure connection with one of the breaker arms, whereby at high intake vacuum said one breaker arm is open and at low intake vacuum said one breaker arm is positioned in accordance with the rotated position of the distributor shaft, so as to decrease coil saturation time and increase timing at light engine load.

2. In an engine ignition system, mechanism for interrupting spark coil primary current comprising a support structure; first and second contacts fixedly carried by said support structure; first and second breaker arms movably carried on said support structure; third and fourth contacts carried by the breaker arms in registry wtih respective ones of the first and second contacts; spring means urging the breaker arms to positions wherein the two sets of contacts are closed; a distributor shaft having cam surfaces engaged with the breaker arms for sequentially opening the contacts; and means responsive to engine intake vacuum for holding one of the breaker arms away from the cam surfaces at high intake vacuum and allowing said one breaker arm to ride on the cam surfaces at low intake vacuum so as to decrease coil saturation time and increase ignition timing at light engine load; said vacuum responsive means including a reciprocating arm engaging one of the breaker arms and subject to the force of the vacuum.

3. In an ignition timing system for an internal combustion engine, an ignition circuit including two circuit breakers in parallel and having overlapping closure periods, with one breaking later than the other but before the other again closes; said one circuit breaker including a switch arm; wall means exposed to engine intake vacuum and movable thereby; and mechanically acting force-transmitting means between the wall means and switch arm for opening said one circuit breaker when the engine intake vacuum is above a predetermined value.

4. In an engine ignition timing system, mechanism for interrupting spark coil primary current comprising a fixed support structure; first and second contacts fixedly carried by said support structure; first and second breaker arms movably carried on said support structure; third and fourth contacts carried by the breaker arms in registry with respective ones of the first and second contacts; spring means urging breaker arms to positions wherein the two sets of contacts are closed; a distributor shaft having cam surfaces engaged with the breaker arms for sequentially opening the contacts; a terminal for each set of contacts; conductor means interconnecting said terminals; and means responsive to engine intake vacuum U for controlling the position of one of the breaker arms; said vacuum responsive means comprising a housing mounted on the fixed support structure and having a movable wall exposed to engine intake vacuum, and an arm extending from the movable wall and having an end portion hooked over said one breaker arm without interfering with movement of said one breaker arm in a direction away from the distributor shaft axis; whereby high engine intake vacuum draws the movable wall away from the distributor shaft axis so as to cause the wall-carried arm to pull said one breaker arm in a direction opposing the action of its spring means for breaking the circuit through said one breaker arm, while at low intake vacuum the spring means for said one breaker arm is efiective to put said one breaker arm in continuous engagement with the cam surfaces.

5. In an ignition timing system for an internal combustion engine, an ignition circuit including first and second circuit breakers in parallel and having overlapping closure periods, with the second breaking later than the first, but before the first again closes; one of said circuit breakers including a switch arm; wall means exposed to engine intake vacuum and movable thereby; and mechanically acting force-transmitting means between the wall means and switch arm for opening said one circuit breaker when the engine intake vacuum is above a predetermined value.

References Cited in he file of this patent UNITED STATES PATENTS

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