US 2715420 A
Description (OCR text may contain errors)
Aug. 16, 1955 H. C. STEARNS FLOW REGULATORS Filed Oct. 7, 1949 United States Patent O FLOW REGULATOR Harry C. Stearns, Glen Ellyn, Ill.
Application October 7, 1949, Serial No. 120,011
3 Claims. (Cl. 138-45) This invention relates to flow regulating devices. It is intended mainly to afford improved control of flow of liquid fuel to jets of carburetors of internal combustion engines used in automotive vehicles and tractors.
In the down-draught carburetors, generally of the plain tube types, used almost entirely in recent years for the carburetion of the internal combustion engines used for vehicle or tractor propulsion, it has become customary to use a fixed orifice in or near the bottom of the bowl of the carburetor to govern the rate of flow of liquid fuel to the main jet or jets of the carburetor, which are located usually at the throat of the main venturi. Except for idling conditions, nearly all fuel supplied to the engine passes through these jets and is controlled in fiow by the said fixed orifice, for any given pressure drop across the said orifice. This orifice is generally located in a small brass screw fitting, and is only alterable in its restriction by substituting another fitting of different size of orifice, often entailing the removal of the float mechanism to gain access to the said orifice fitting. Usually the space is small between the orifice and the levelling float in the said carburetor bowl. Due to this lack of accessibility to these said orifice fittings, and lack of familiarity of most service men with the carburetor functions, and also to reduce initial cost of carburetors, which are purchased on a close price basis by automotive manufacturers, it has become quite standard practice to provide these fixed orifice carburetors with orifice openings sufiiciently large to handle any commercial grade of fuel, and at the highest viscosity condition of this fuel occurring at the lowest temperature that the fuel may be used. The following conditions are detrimentally encountered, as a result of this large fixed orifice condition.
When fuels of low specific gravity with accompanying low kinematic viscosity characteristics are utilized, more fuel is supplied to the jets and the fuel-air mixture than is required, and often more than will afford the best engine performance. A wise operator will, however, seek a grade of fuel which will obviate this condition if he is cognizant of it. However, another condition arises as a result of this control arrangement which has not been met satisfactorily in these commercial carburetors. This is caused by the change of viscosities, or flow characteristics, during temperature changes, of both the liquid fuel and the small supply of air which is controlled by another orifice and fed into the fuel supply at a point between the said fuel metering orifice and the jet, to airbleed the jet. If the relationship of the flow of this air to the jet, with respect to the fuel feed to the jet, is appreciably altered, these mixture proportions are considerably disturbed, and it is for this reason that mixture proportions must under all circumstances tend toward the rich side, so that engines do not backfire, or stumble. Changes of these flow characteristics may be as follows.
During summer months it is customary for the petroleum industry to supply grades of gasoline to the motoring public, which are of higher viscosity for a given temperature, than is supplied during the fall months,
and it is customary to supply grades in the fall which are of higher viscosity for a given temperature than is supplied during the winter months, and in colder climates or Warmer climates modifications in viscosities, must also be made, with introductions of increased proportions of more volatile ingredients in the colder climates to permit engine starting under very cold conditions, but these gradations are mainly caused by the fixed orifice control in these commercial carburetors. Choking has been necessary in starting with these carburetors under cold starting conditions, but should not be resorted to any longer than necessary, as excessive amounts of raw fuel are often drawn into the engine under the use of this device, causing crank case dilution of lubricating oil with resultant increased engine wear, waste of fuel, and fire hazard increase. In nearly all climates, and during all seasons, gasoline in carburetors will be subjected to temperature changes of 70 deg. F. to deg. F., without change of grade of gasoline. Consider now how this effects metering through the fixed orifice for this purpose.
Viscosities of fuels differ in the following manner: The kinematic viscosity of gasoline specific gravity .70 is given by authorities as .50 centipoises at 32 deg. F., and as .25 centipoises at deg. F., and that of gasoline specific gravity .75 as .95 centipoises at 32 deg. F., and as .40 centipoises at 150 deg. F., and thus the viscosity of one is halved with a temperature increase of only 118 deg. F., while the viscosity of the other is halved within the temperature change which may take place in a carburetor within a few hours or under extreme circumstances in a fraction of an hour.
The air which supplies the aforementioned air-bleed will change its fiow characteristics through a fixed orifice according to the following formula or a close approximation:
In this formula,
W=Weight of air discharged d=Diameter of orifice i=Difierence of pressure P=Mean absolute pressure T=Absolute temperature, or deg. F.+461
From this it is seen that with an increase in temperature the passage of air through the air bleed will decrease, which is the converse of the condition which occurs in the fixed fuel orifice. This tends to undesirably alter the balance between these two.
One of the objects of my invention is to provide a practical means for appreciably lessening the objectionable features I have just described.
Another object of my invention is to provide a device which is inexpensive to produce.
Another object of my invention is to provide a device compact enough to be insertable in the present standard carburetor either in the original assembly or in the field.
Another object of my invention is to provide a device compact enough in its mounting and in its clearance shape to avoid interference with movement of the carburetor float, when the device is used in the float chamber.
Another object of my invention is to provide a device which will lessen the tendency for orifice plugging from accumulations of tetraethyl lead and sediment in carburetor bowls.
Another object is to facilitate external adjustment of flow restriction at any temperature, or for any grade of fuel, together with means for maintaining constant flow, or improved regulation of flow with temperature change.
Other objects will appear hereinafter, from the following description, reference being had to the accompanying drawing in which:
Fig. l is a view, shown in perspective, of one embodiment of my invention.
Fig. 2 is a view, also shown in perspective, of another .fimbodiment of my invention.
Referring to Fig, l of the drawing, 1 is a U-shaped bimetal element. A tapered pin 2 is shown riveted or fastened to the bimctal near one end of, and within the U. The orifice fitting generally used in modern carburetors is shown as 3. The screw shank of the orifice fitting 3, is inserted through the hole in the opposite side of the U from that inwhich the pin 2 is riveted, and this hole is just a clearance hole for this shank, being central with the centerline of the tapered pin 2. A fiber washer is generally inserted between the head of the orifice screw and the bimetal, which shapes the resilient bimetal to the metallic seat upon which it is generally mounted, but this washer is not shown here, as on a fiat metallic surface it is not needed, and the fitting 3 may be anchored from turning, by a slight prickpunch mark at the juncture of the head and the bimetal l. A ceramic or suitable insulating block for the resistance wire coil surrounding the lower portion of the bimetal is shown as 4, and the wire as 5. The shape of one turn within the insulator 4 is shown as 11. ()ne end of the resistance wire coil is connected to ground of the engine, and this may be done within the carburetor. The other end of the coil is connected to a variable or adjustable rheostat shown as 7, and the leadout wire as S. The rheostat resistance element is connected to a battery or electric current supply 9 at the opposite side to that which has been grounded at 10. In the case of an automobile, truck or tractor, the rheostat 7 would generally be located on the dash or instrument panel 18.
Referring to Fig. 2 of the drawing, 1 is a bimetal element, which is riveted, or fastened, to a U-shaped spring steel member 14 near its center. A tapered pin 2 is fastened to the bimetal element 1 at the opposite end to that which is fastened to 14, with its point toward the spring-steel strip 14. A standard orifice fitting is shown as 3 with its screw shank inserted in a hole in the spring steel strip 14, the center of which hole is in line with the centerline of the tapered pin 2. A section of the cover of a carburetor bowl 17 is shown as 15. A set-screw is shown as 16 threaded through the cover 15 with the centerline of 16 in line with a small hole in the springsteel strip 14, in a position near its end which is opposite to that in which the orifice fitting 3 has been inserted. Locking means, such as a standard nut or half-nut may be used for the set-screw 16, but the pressure of the spring steel strip 14 is generally sufiicient. A standard bar-rel float is shown as 12 with its approximate location with respect to my invention.
When either of the devices shown is used to control liquid fuel flow in a carburetor, the metal of higher elongation with temperature increase, is on the outside of the bend of the bimetal. if the bimetal is used to control air-bleed or air flow, this higher expansivity metal is at the inside of the bend or if used with a straight bimetal, the higher expansivity metal is on the side away from the tapered pins shown as 2. The thickness of the bimetal may be varied in either device and also the taper of the pin shown as 2, or the diameter of the orifice opening shown as 3 in both devices. The apparatuses shown in Figs. 1 and 2 are so constructed as to permit them to be secured in place in a conventional carburetor bowl or float chamber by using for that purpose the orifice fitting 3 as normally supplied with the carburetor. it is to be understood that in conventional carburetor construction, the passage from the bowl to the jet is threaded to receive a metering orifice fitting such as is shown at 3, this fitting being screwed into place from within the carburetor bowl. The anchorage end of the bimetal 1 shown in Fig. 1 is provided with a hole through which the shank of a conventional orifice fitting 3 may be inserted as shown. The orifice fitting 3 is then screwed into place in the threaded opening in the carburetor bowl above referred to and tightened to hold the bimetal 1 securely. The spring strip or leaf E4 of the apparatus shown in Fig. 2 is similarly provided with a hole in its lower end through which a conventional orifice fitting 3 may be inserted for attachment as described above. The unit shown in Fig. l can be constructed and used either with or without the heating elements, but considerably greater utility is afforded, in general, by the use of the heating element, which will save its additional cost many imes over, afford better performance and fuel economy, with great convenience in motor starting during the winter months, and often afi'ord the difference between starting and not starting of motor vehicles in the colder climates, such as the northern section of the United States, Canada, Alaska and similar locations throughout the world, during their cold months. its operation will be described more clearly, subsequently. The device shown in Fig. i when used without the heating element. will give excellent results in improved engine fuel econ only and performance in the moderate climates, and can be built and installed at a lower cost, particularly when the right specifications in its elements have been worked out for a particular type of engine. With or without the heating element arrangement shown in Fig. l, the lower half, or mounting half of the device can be made from plain sheet metal, which does not deflect with temperature change, and the upper half of bimetal, and I will describe the advantages and disadvantages of this construction later. When any of these devices are provided for insertion in the field, there will be times when the removed orifice may be used without redrilling in conjunction with my device, as oversize holes have been in quite common use for reasons previously described.
In the construction of the device shown in Fig. 2, since the hole 13 in 14 is disposed in predetermined relation to the mounting end of spring 14, which is secured in place by the fitting 3, the set screw 16 finds the hole 13 readily when the cover 15 is put in place. Now the screw 16 may be used for adjusting the location of the pin 2 in the orifice in 3 at any given temperature by screwing the screw 16 down against the spring-steel 14, because in the unsprung position of the strip M the tapered pin 2 has not entered the orifice hole in 3, or has not sufiiciently entered to have an appreciable restrictive effect. When the screw 16 is screwed against the strip 14, the lower part of the U is forced down, and a slight bend is thrown into this member at about the point of anchorage of the bimetal 1 to the strip 14, which causes the pin 2 to move downward in such a manner that its centerline remains central with the orifice hole in 3. By this means a setting, for any grade of fuel may be made at the existing temperature.
The bimetal control in devices shown in both Fig. l and Fig. 2 function the same, which is as follows: At the lowest temperature to which the fuel will be subjected in the carburetor, taper pin 2 may just leave the orifice hole, or the orifice hole may be large enough so that regulation may be accomplished without taper pin 2 ever leaving the hole. However, it is found, as previously stated, that with the excess flow tolerated in most standard carburetors, to assure an adequate supply of gasoline, or other liquid fuel, because no control of this type has been available, that the standard orifice may often be used with a setting at which the needle or tapered pin 2 just leaves the hole at approximately 20 the fuel alone. The experimental method is also more accurate, as it is difficult to obtain accurate figures on kinematic viscosity for the particular fuel being used, and with some synthetics, gums also form which make the figures uncertain, but the experimental method has given excellent results. A unit as shown in Fig. 1, without the heating element, has been worked out for a 1939 Plymouth automobile and switched to a 1941 Plymouth without specification change and with nearly identical results and greatly improved economy.
In the device shown in Fig. 1, the heating element is preferably molded into a ceramic element or other suitable insulating material, having a central rectangular opening, the cross section of which is such that the heating element 5 closely surrounds the bimetal 1 with a suflicient clearance to permit the bimetal to flex through its operating range, which calls for a practical alowance, in most cases of about $5 inch. In normal operation, the operator, such as a car, truck, or tractor driver, adjusts the slight amount of current required to affect the bimetal position, because of the close proximity of the heating element, to cause the greatest insertion of the tapered pin 2 in the orifice in 3, that is possible without sacrificing desired driving performance. The small amounts of heat used for this do not affect the fuel temperature noticeably and do affect the adjustment adequately, and since the major part of the element is exposed to the fuel and will be affected mainly by this, the element 5, under these conditions, has mainly an adjusting effect. Under extremely cold starting conditions, by cutting the resistance of the rheostat 7 down or completely out, sufiicient heat may be developed to raise the temperature of the fuel to appreciably increase its volatility, and thus greatly improve starting. The taper pin 2, under these conditions will move down to increase restriction to flow, but this is of little importance, as there is always a high suction on the jets during starting choking, and there is always adequate opening, under these conditions, between the tapered pin 2 and the orifice 3. With these low temperature conditions prevailing, under no circumstance could the element supply enough heat in the carburetor bowl to elevate the temperature of the gasoline or fuel to that which would be reached under normal running conditions from other sources of heat affecting the carburetor, but under these low temperature conditions, an increase of the temperature of the gas being fed into the jets of forty or fifty degrees, makes a marvelous difference in starting ease. In automobiles, trucks, plows for snow removal, tractors and the like, the engine starting switch should be connected in series with the rheostat circuit controlling the heating element. As shown in Fig. 1, in some other applications this is not necessary. In starting an engine in cold weather, with this device, the rheostat should be set at a point of lowest electrical resistance for a minute or two, to permit enough current to flow through the heating element 5 in the bowl to warm enough gasoline adjacent to the orifice for starting the engine when the choke has been pulled to the full closed position and the starter contacted, the starting switch having been turned on at the first setting of the rheostat, providing current is supplied to the rheostat through the starting switch. As soon as the engine fires, the choke should be opened slightly, with the heating element 5 remaining in use for five or ten minutes, thereafter, depending upon the temperature of the air intake to the carburetor, after which it is completely cut out until normal running conditions obtain, the choke being gradually opened during this period. Then with the choke completely opened, the heating element may again be cut in under low current control, for adjusting the fuel flow for maximum economy, best performance, or modifications suitable to the driver or operator.
Where more importance is attached to improved cold weather starting, than to close mixture adjustment controlled remotely, the heating element 5 of Fig. 1 may be incorporated about the spring strip shown in Fig. 2 as 14, the heating element being placed close to the orifice opening, or it may be mounted on an independent strip of metal in proximity to the orifice in 3 with a temperature responsive flow controller attached for common mounting, to permit emphasis on heat development for starting, with thermal regulation of flow based on fuel temperature alone, or approximately so.
Devices for heating gasoline in carburetor bowls were invented and patented many years ago, but they were in the nature of pencil-like attachments which were difficult to insert in carburetor bowls, as the fioats generally fit the bowls quite closely where it was necessary to insert these pencils, and when these were insertable, could not generally be located where fuel close to the outlet orifice could be heated first and mainly. The previous attachments necessitated the heating of the full bowl of gasoline, before any warm gasoline could be drawn through the orifice in the bottom. This increased the drain on the battery before starting was attempted, and in some cases the excessive drain was sufiicient to increase the internal resistance of the battery to the point that it would not afford enough energy to the starting motor to turn the engine. With my arrangement, all heating is done adjacent to the orifice, which materially lessens the amount of fuel necessarily heated for starting, affording quicker starting with less battery drain, and as shown in Fig. 1 affords a remote control for mixture proportions to a device which thereafter affords a close automatic control of air-fuel mixture proportions for best engine performance, and maximum economy of fuel.
As an object of my invention I have stated that my invention would afford an improved means of preventing plugging of the metering orifice for fuel in the carburetor, and from my disclosure of my invention, it will be seen that the movement in and out of the orifice, with temperature change, of the tapered pin 2, tends to force the soft accumulations of tetraethyl lead, so commonly used in standard motor fuels, down through the orifice in 3 when the pin moves in, or to pull them back until they mix with fuel or settle in the bowl, and that the annular shaped metering opening afforded between the orifice and the tapered pin 2, can not be plugged by any single solid particle, such as scale, as a plain orifice hole can. Since scale can form in the bowl of a carburetor, and tetraethyl lead can settle out of motor fuel anywhere, and as well after it has passed a strainer, as before, this feature is of material importance.
Referring again to the tests which I have made of these devices in two Plymouth cars which I use for these developments and drive daily, I have with as good, or improved performance than is normally obtained with these cars, afforded some outstanding fuel economy records. As one of the former carburetion engineers representing the leading carburetor company of the United States at our most prominent automobile factories I have never been able to accomplish as much improvement in economy and performance with any single device as I have with any of the devices which I have invented and herein disclosed.
Although this invention has been described in considerable detail, it is understood that such description is intended as illustrative rather than limitng, as the invention may be variously embodied and is to be interpreted as claimed.
1. In an apparatus for controlling flow of liquid fuel from a carburetor float chamber to an internally threaded exit therefrom adapted to be inserted in said float chamber in said exit the combination comprising an orifice fitting including a threaded screw having a head and a concentric axial orifice extending therethrough the threads of said screw being engageable with the internal threads of said exit to secure said orifice fitting therein to provide a predetermined orifice opening in said exit; a bimetal member having a flat terminal portion with an aperture therein of a size to admit and closely surround the threaded portion of said orifice fitting to provide an anchorage end secured to said orifice member and a defiectable portion extending transversely with respect to the orifice in said orifice fitting said defiectable portion terminating in a free end overhanging the orifice in said orifice fitting; a movable taper pin secured to the free end of said bimetal member to be moved thereby having a flow controlling end portion extending toward and disposed within the orifice of said orifice fitting for movement therein to alter the effective discharge area thereof; adjusting means including an external manually adjustable member adapted to be disposed on the exterior of said float chamber; connecting means adapted to extend therefrom into said float chamber; and position altering means operable by said manually adjustable means through said connecting means cooperatively related to said bimetal to adjustably alter the position of the same 1 from that determined by the temperature of liquid entering said float chamber.
2. An apparatus in accordance with claim 1 wherein the external adjustable member consists of an electrical power supply and a rheostat, the connecting means consist of electric lead wires extending therefrom adapted to enter said float chamber, and the position altering References Cited in the file of this patent UNITED STATES PATENTS 1,413,212 Anderson Apr. 18, 1922 1,529,906 Morris Mar. 17, 1925 1,813,122 Moore July 7, 1931 1,871,287 Whittaker Aug. 9, 1932 1,872,708 Ericson Aug. 23, 1932 1,964,638 Kreidel June 26, 1934 2,124,580 Lavine July 26, 1938 2,213,663 Berard Sept. 3, 1940 2,247,679 Forke July 1, 1941 2,303,640 Hogg Dec. 1, 1942 2,317,556 Russel Apr. 27, 1943 2,341,694 Cofiey Feb. 15, 1944 2,456,170 Bennett Dec. 15, 1948