US2560787A - Switch device - Google Patents

Description

July 17, 1951 L. D. laoYcEr SWITCH DEVICE Original Filed Oct. 27, 1944 INVEN TOR.

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E C VI m D. a m D 5 R n 2 A Y G B F 2 1 O D lz 7 4 5 s 4 e 4 4 2 31. 2 u 3 ..m W in wf .7 5 4 l G F 3 Patented July 17, 1951 SWITCH DEVICE Leonard D. Boyce, Kirkwood, Mo., assigner to Carter Carburetor Corporation, St. Louis, Mo.,

. a corporation Original application October ,27, 1944, Serial No.

560,656. Divided and this application December 17, 1948, Serial No. 65,900

1 Claim.

This invention relates to transmission control mechanisms for automotive engines and consists particularly in novel means for preventing operation of the so-called over-drive throw-out when the vehicle is travelling at such a rate of speed that the consequent increased speed of the engine would endanger the parts thereof.

This application is a division of my copending application, Serial No. 560,656, filed October 27, 1944, now abandoned, which is a continuation in part of an application Serial No. 340,819, filed June 15, 1940, now abandoned.

Wherefthe transmission gearing for an automobile is provided with a, so-called over-drive, which is engaged automatically when the vehicle is travelling at higher than a predetermined speed, it is desirable to provide for greater power and faster acceleration particularly in case of an emergency as lwhen the vehicle, though travelling in over-drive, must suddenly be speeded to pass another car. When the operator moves the throttle to fully open position in order to accelerate the vehicle, the automatic transmission is likely to shift to a more powerful gear ratio, as from fourth or direct drive to third gear. It has been found that with such arrangement, where the vehicle is travelling at 45 miles an hour or faster, the transmission cannot be safely returned to third gear, as above described, due to the consequent excessive engine speed. Considerable power and some time is required to bring the engine up to the necessary speed and, in fact, this may be impossible when the car is already travelling at high speeds.

It has been suggested that this problem may be solved by providing for kick-down of the gearing ratio when the throttle Valve is substantially wide open while preventing such kickdown in case the engine is travelling above a certain predetermined speed.

It is the main object of the present invention to provide a novel throttle and suction operated switch device for use with such a gearing arrangement.

A more detailed object is to provide such a switch device having a reciprocating suction piston provided with stabilizing means.

Fig. l is a diagrammatic view showing portions of an automobile engine including the carburetor and transmission with the invention applied thereto.

Fig. 2 is an enlarged View of a portion of the carburetor shown in Fig. 1 but taken at 90 thereto, the over-drive throw-out switch being sectioned on line 2-2 of Fig. 1 for clearer illustration.

2 A Fig. 3 is a sectional view of the switch as in Fig. 2 but showing the switch contacts engaged. Fig. 4 is a view similar to Fig. 3 but showing the switch contacts rendered ineffective to` complete the overdrive throw-out circuit.

Fig. 1 shows at I0 a portion of an internal combustion engine ofthe automotive type includ.- ing an intake manifold I I mounting a carburetor generally indicated at I2. A clutch and change speed transmission gearing of any suitable form are mounted, respectively, in housings I3 and I4 secured to the rear portion of the engine. The transmission is provided with over-drive :mechanism located within a housing I5 forming a rearward extension on housing I4 and directly connected to the usual propeller shaft I6 for driving the rear axle. A solenoid device II is mounted on the side of the over-drive housing I5 and, when energized, functions in a known manner to throw out the over-drive or, in other Words, return the transmission gearing from over-drive position to third or the next higher and more powerful gear ratio. l

Solenoid I'I is controlled by an electrical circuit including storage battery I8 having one terminal grounded, as at I9, and a switch device generally indicated at 20 mounted upon the carburetor IZ. The storage battery and switch are connected to solenoid I'I, respectively, by leads 2| and 22, the latter being connected to an insulated terminal 23 forming one of the contacts of switch 20 (Figs. 2, 3 and 4). The detailed construction of the solenoid as well as the over-drive and other parts of the transmission do not in themselves, constitute the present invention and are not illustrated. For convenience, I have shown a manual shift lever 24 for shifting the transmission gearing through the usual reverse, and first, second, and third forward gears, but this shifting may be effected by other suitable means. As is lwell known, the over-drive portion of the transmission is automatically engaged responsive to predetermined output speed of the transmission mechanism or, in other words, wheel speed.

Heretofore, the control circuit for the overdrive throw-out solenoid I'I has been controlled solely by a throttle actuated switch so that whenever the throttle pedal 25 is fully depressed, this solenoid is energized for automatically reshifting from over-drive to third gear. In the present invention, I incorporate an additional suction control for the solenoid switch Which renders the switch ineffective to energize the solenoid under predetermined suction conditions. This switch includes an angular body portion 30, the legs thereof being hollowed as at 3l and 32. Hollow leg 3| forms a cylinder for slidably receiving a cup-shaped piston 33 normally urged downwardly by a coiled spring 34 seated against an inner surface of the piston and a shoulder 35 formed in the upper portion of the cylinder. A passage 3E connects the cylinder above piston 33 to the interior of the carburetor barrel or mixture conduit preferably at the throat of venturi 31 (Fig. 2). A port 39 connects the cylinder below the piston to atmosphere and this port may lead to the air inlet horn of the carburetor so that the air will be drawn through the usual air cleaner (not shown). Secured to the undersurface of piston 33 is an angular spring clip 31', the projecting leg of which carries a metallic ball or enlargement 38 adjacent, but normally slightly spaced from the inner extremity of switch contact 23 (Fig. 2). The body 30 of the switch device is grounded through the carburetor, intake manifold, and engine block, but piston 33 is formed of insulating material to prevent shorting of switch contact 23. The piston has a pair of legs, one being shown at 33', depending on opposite sides of terminal bushing 23 and cooperating with the inwardly Aprojecting portion thereof to prevent rotation of `the piston and extension 31 from the operative position shown. Legs 33' also fix the lower or normal position of thepiston and extension.

The other hollowed arm of the switch body slidably receives a hollowed switch actuating plunger 40 and a collar 4| formed on a pin 42 slidably received within plunger 40 and extending longitudinally through a screw cap 43 secured to the end of this leg of the switch body. I

Collar 4| is normally urged outwardly against cap 43 by a coiled spring 44 and plunger 40 is similarly urged outwardly by a coiled spring 45 whereby a yielding one-way connection is formed between the switch plunger and pin to three pounds greater than the compressive strength of the spring 45. This results in a one to three pound limitation on the pressure which may be applied to the contact point 38. These contact points are frequently made of silver and would be deformed by the excessive pressure which might be exerted by the pressure of the drivers foot on the accelerator. The spring arrangement is such as to resist inward movement of the control member 40 after the throttle has been opened far enough to contact the switch points and move together the coils of spring 45. Thereafter, a conscious effort of the operator will be required to compress spring 44 and telescope rod 42 into member 40.

Pivotally mounted in the carburetor mixture conduit posterior to venturi 31 is a butterfly throttle valve which may be manually operated in the usual manner by means of a suitable arm 52 (shown in part) rigidly attached to throttle shaft 5I. Also formed on throttle arm 52 is an extension 53 positioned to engage stop 54 to fix the wide open position of the throttle valve, and a second arm 55 carrying an adjustable screw 56, the end 56 of which engages the stop 54 to x the closed position of the throttle valve. A third arm 51 formed rigidly with throttle crank 52 is positioned to engage switch contact pin 42 when the throttle valve is substantially fully opened (Figs. 3 and 4l)y to 4 urge this pin and switch contacting plunger 4P) inwardly against enlargement 38 carried by piston 33 and to urge this enlargement in the direction of switch contact 23. Spring 34 is adjusted so as to maintain piston 33 in its lowermost position, as in Fig. 3, whenever the suction at the throat of venturi 31 is less than approximately 1.8 inches of mercury, which corresponds with a vehicle speed of approximately 45 miles an hour. When this degree of suction is exceeded at the throat of the carburetor venturi, that is, when the vehicle is travelling in excess cf 45 miles an hour, piston 33 will be lifted against spring 34 into engagement with shoulder 58 formed in a wall of cylinder 3| so as to raise enlargement or ball 38 and prevent contact of switch terminal 23 thereby (Fig. 4). Thus, when the predetermined venturi suction is exceeded, the switch is automatically rendered inefective to energize the over-drive throw-out solenoid I1. Whenever the suction in venturi 31 is less than approximately 1.8 inches of mercury, ball 33 will be positioned so that when plunger 40 is forced inwardly due to the throttle valve being Vfully opened, switch contact 23 will be grounded through this enlargement, plunger 40 and the switch body so as to complete the solenoid control circuit and cause reshifting of the transmission mechanism from over-drive to third gear. v

By means of the illustrated structure, the overdrive, which is automatically engaged at a wheel speed of, say 35 miles an hour, may be thrown out whenever the driver demands maximum power and fully opens the throttle valve, but at vehicle speeds in excess of 45 miles an hour, when it would be unsafe to reshift the gearing from over-drive to a higher ratio of engine to wheel speed, such reshifting is automatically prevented. Thus, it is possible to use a higher third gear ratio than heretofore so as to attain better power and acceleration at the lower speeds.

In the operation of the device shown in Figures 1 to 4, the suction maintained in the venturi 31 acts on the piston 33 to hold it in upward position against the pressure of the spring 34 whenever the gear speed and throttle position exceed predetermined values. When the piston 33 is in the position shown in Figure 4, the opening of the throttle will not result in closing of the circuit through the contact member 38, as the friction created by the pressure exerted on. contact member 38 and the insulation surrounding the terminal 23 by the end of the member 40 is so great that the spring 34 cannot shift the piston 33 downwardly.

When the throttle is opened with the piston 33 in the position shown in Figure 3, contact is made through the member 33, and the gear shift mechanism is operated. As long as the operator holds his foot on the throttle, the friction due to the pressure on the member 38 will prevent any suction build-up in the venturi from withdrawing member 38 from between members 23 and 40 to break the circuit and cause reshifting of the transmission. This is a desirable feature, because the shock of reshifting the transmission from a lower gear to a higher gear would be too great when the gear speed is in excess of the predetermined permissible limit, for instance, 45 miles per hour.

For the reasons outlined above, the transmission control prevents automatic shifting of gears to a lower gear ratio when the venturi suction exceeds a predetermined amount and prevents Backs? automatic shifting to a higher ratoas long as the throttle is held in substantially open position. In accelerating the car to its maximum speed, the operator must release the accelerator pedal sufficiently to withdraw the end of plunger 40 from contact with the member 38 in order to cause a step-up in the gear ratio.

The invention may be modied in various respects as will occur to those skilled in the art and the exclusive use of all suoli modifications as come within the scope of the appended claim is contemplated.

I claim:

A device of the class described including a cylinder, a pressure responsive piston therein, a switch terminal element projecting into said cylinder, and an electrical conductor carried medially by said piston for cooperation with said element, portions of said piston straddling and extending beyond said conductor and said terminal element and cooperating with said element to prevent rotation of said piston and also cooperatm ing with an end Wall of said chamber so as to x the operative relationship of said conductor and terminal element in the extreme position of said piston.

LEONARD D. BOYCE.

REFERENCES CITED The following references are of record in the lle of this patent:

UNITED STATES PATENTS

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