US2033565A - Backfire stop - Google Patents

Description

M. P. WHITNEY BACKFIRE STOP March 10, 1936.

Filed Nov. 20, 1931 2 Sheets-Sheet 1 l/VVENTOR March 10, 1936. M WHITNEY 2,033,565

' BACKFIRE STOP Filed Nov. 20, 1931 2 Sheets-Sheet 2 V I 5 JZ\ o 2 32 .9 HIIIHMW 43 w //v VENTOR B Y M01209 1? A TTURNE Y Patented Mar. 10, 1936 UNITED STATES PATENT OFFICE BACKFIRE STOP Application November 20, 1931, Serial No. 576,395

4 Claims.

This invention relates to a back-fire stop for internal combustion engines and more particularly to a device for preventing an internal combustion engine from firing while it is rotating backwards.

Back-firing of internal combustion engines due to pre-ignition occurs in some installations due to failure of the operator to retard the ignition during starting, or due to the advanced setting of the ignition when some forms of automatic spark advance are employed. It is, of course, in general desirable to restrict such back-firing, and particularly in connection with the use of automatic starting mechanism since if a series of back-fires occur, as sometimes happens, the automatic starting mechanism may re-engage while the engine is rotating backwards, thus setting up heavy and possibly destructive stresses.

It is an object of the present invention to provide anovel device for stopping back-fire of internal combustion engines.

It is another object of the invention to provide such a device which is effective to restrict back-firing to an initial explosion only.

A further object isto pro-vide such a device which is actuated by an initial explosion to prevent the recurrence thereof.

Furtherobjects and advantages will be apparem to those skilled in this art from the following description taken in connection with the accompanying drawings in which:-

Fig. 1 is a semi-diagrammatic showing of a conventional type of internal combustion engine with its ignition system illustrated in connection with one preferred embodiment of the invention;

Fig. 2 is an enlarged side elevation partly in section of an automatic switch adapted. to operate in accordance with the present invention;

Fig. 3 is a similar view of the insulating cap of said switch;

Fig. 4 is a similar view of a modified form of said switch;

Fig. 5 is a similar View of the insulating cap thereof;

Fig. 6 is a similar view of the switch illustrated in Fig. 4 with the parts thereof moved to closed position;

Fig. 7 is a detail partly in section of an insulating guide thimble in said switch;

Fig. 8 is an end view of the same; and

Fig. 9 is a semi-diagrammatic showing of an ignition system of an internal combustion engine illustrated in connection with a second embodiment of the invention.

Referring first to Fig. 1 of the drawings, there is illustrated an internal combustion engine having a conventional form of ignition system comprising a battery I, grounded at 2 and arranged to be connected by an ignition switch 3 with an ignition coil comprising a primary 4 and a secondary 5. The primary circuit is completed through a lead 6 to the breaker mechanism 1 which is grounded at 8 and which is shunted by the usual condenser 9. Secondary 5 of the ignition coil is connected by a lead I I to a distributor ll], mounted on the engine.

According to the present invention means are provided for rendering the ignition system inoperative in response to backward rotation of the engine. As here illustrated, this device is in the form of a grounding switch. l2 for the ignition system mounted on some portion of the fuel intake system of the engine such as the intake manifold l3, and arranged to be operated by pressure generated within said intake manifold.

Referring now to Fig. 2 of the drawings, it will be seen that the grounding device l2 comprises a metallic body portion l4 in the form of a cylindrical casing provided with a threaded extension l5 adapted to be mounted in the intake manifold as shown in Fig. 1. A metallic piston member l6 forming one electrode of the switch is formed with a cylindrical head I! adapted to slide in the cylindrical body I and having a substantially gas-tight fit therein. The stem N3 of the piston member is arranged to slide freely in an insulating guide member 19 mounted within an insulating cap 2| and clamped thereby to the body portion I4 as by means of cooperating threads 22. The cap 2| carries a stationary electrode 23 which is sealed in said cap in juxtaposition to the end of the movable electrode l6 and protrudes therefrom to form a binding post as indicated at 24. Suitable yielding means such as a spring 25 is provided for normally maintaining the electrode l6 in the open position as shown in Fig. 2, and vents 26 and 21 are provided in the body portion l4 and cap 2! for permitting the escape of gas trapped back of the piston electrode whereby said electrode is permitted to move freely to its closed position under the influence of pressure applied through the passage 28 in the extension I5.

Means are preferably provided for delaying the return of the electrode IE to its open position, and is here illustrated in the form of a ball check valve 29 arranged to seat against a shoulder 3| conformed thereto in the extension 15. It will be understood that the seat 3! is arranged not to make a perfect gas-tight fit with said ball so that when the pressure is removed from the passage 28, gas will leak back past the ball 29 and the piston 11 and gradually allow the electrode l6 to return to its open circuit position.

In Figs. 4 to 6 inclusive there is illustrated a modified form of switch in which an insulating guide member 39 is provided which is perforated as indicated at 4| to provide vents for the piston 42 leading to the vents 43 in the cap 44. It is thus unnecessary to vent the body portion 45 of the switch. In this embodiment of the invention, no extraneous means are provided for returning the piston 42 to its open position, but reliance for this purpose is placed on the vacuum generated in the intake system during rotation of the engine by the starting motor and during normal operation of the engine to move and return the piston electrode in its open position. In this embodiment of the invention, a check valve 46 is illustrated which is similar to the ball check 29 of Fig. 2, but it will be understood that the employment of such delaying device is optional and it may be omitted if desired in order to provide a more positive releasing operation for electrode 42.

Referring now again to Fig. 1 of the drawings, in the operation of the device, the grounding switch I2 is connected to ground the ignition lead II as by means of a lead 41. When the ignition switch 3 is closed and the engine is rotated by the starting motor, the piston electrode E6 or 42 is maintained in open position and the ignition functions in the usual manner. If, however, a back-fire should occur, a pressure is immediately built up in the intake manifold I3 which causes the movable electrode to slide to its closed position, as illustrated in Fig. 6. Connection is thereby established from the high tension lead ll through the lead 4?, fixed electrode 23, the movable electrode 16 or 42 and the body of the switch Hi to the ground. The ignition is thus rendered inoperative and further back-fires are thereby prevented until the backward rotation of the engine ceases and pressure in the intake manifold I3 is dissipated.

An optional modification of the connection of the grounding switch to the ignition system is illustrated in Fig. 9 which shows the grounding switch l2 connected by a lead 48 to the primary lead 5 of the ignition circuit instead of to the secondary lead II as illustrated in Fig. 1. lhe remaining elements of this embodiment are similar to the parts illustrated in Fig. 1 and are similarly numbered. When this arrangement is used, closure of the switch l2 causes the primary circuit of the ignition system to be grounded whereby said ignition is effectively rendered inoperative. Inasmuch as this period of inoperativeness is only of short duration, namely during the backward rotation of the engine, no harm will result to the ignition coil by reason of this temporary ground connection.

Although certain forms and arrangements of the invention have been shown and described in detail, it will be understood that other embodiments are possible and that various changes might be made in the details and forms of connection of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In combination with an internal combustion engine and an ignition system therefor, means responsive to backward rotation of the engine for rendering said ignition system inoperative, said means being operative to restore the ignition system to operative condition when backward rotation of the engine ceases, and means for delaying such restoration to allow the engine to first come completely to rest.

2. In combination with an internal combustion engine having a fuel intake system and an ignition system therefor, means responsive to positive pressure in the intake system of the engine for grounding said ignition system for rendering the same inoperative until such intake pressure is dissipated, and means for thereupon returning said ignition system to operative condition.

3. In combination with an internal combustion engine having a fuel intake system and an ignition system therefor, means responsive to positive pressure in the intake system of the engine for rendering said ignition system inoperative and means for retarding the release of such pressure from said pressure responsive means.

4. In combination with an internal combustion engine having a fuelintake system and an ignition system therefor, grounding means for said ignition system including a fixed contact, a movable contact, means responsive to positive pressure in the intake system of the engine for closing said contacts, and means for retardingv the release of the pressure from said pressure responsive means.

MAURICE P. WHITNEY.

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