US2194527A - Apparatus for determining the lubricating values of oils - Google Patents

Description

F. RAY

March 26,A 1940.

APPARATUS FOR DETERMINIG THE LUBRICATING VALUES OF OILS Filed July 5, 1929 3 Sheets-Sheet l March 26, 1940. v F, RAY 2,194,527 v APPARATUS FOR DETERMINING THE LUBRICATING VALUES OF OILS Filed July 5, 1929 3 Sheets-Sheet 2 ATTORNEYS F. RAY

vMarch 26, 1940.

APPARATUS FOR DETERMINING THE LUBRICATING VALUES-"OF OILS Filed July 5, 1929 5 Sheets-Sheet 3 INVENTOR Patented Mar. 26, 1940 UNITEDl STATES APPARATUS Fon DETERMINING 'rnE LUmoA'rme vALUEs or ons Frederick Ray, short mns, N. J.,

Automatic Appliance assignor to The Company, St. Louis, Mo.,

, a corporationof Missouri Application July s, 192e, 'serial No. 376,041

3 Claims.

This invention is' directed to a novel apparatus for determining the lubricating values of oils as they are used, for example, in automotive engines and the like.

As is well known, the bearings and cylinders of automotive engines are lubricated by a combined pressure and splash system which circulates the lubricant round and round for use over and over again until it loses its lubricating value. The most commonly employed lubricant is mineral oil, Awhich is readily miscible with the lighter hydrocarbon fuels,- such as gasolinel and kerosene. These lighter fuels are not always completely consumed in the operation of the engines, but instead, some of the fuel collects on the relatively cold cylinder walls and subsequently nnds its wayy past the pistons into the crank case, where it becomes mixed with the lubricating oil. As a result, the lubricant gradually becomes diluted, with a consequent reduction in viscosity for lubricating value. f V

Of course, the absolute effect of dilution-upon viscosity is dependent upon the original viscosity, percentage of dilution, and operating temperatures, and varies widely under different conditions. In some instances, for example, such as occur in ordinary practice, a`dilution ofvfrom 10% to 20% will reduce the viscosity of the mixture to about one third of the viscosity of the pure oil. The various lubricating oils'used in automotive engines differ widely in viscosity at any given temperature, and the viscosities of all the different oils vary widely with the temperature. These oils are subjected to mean temperatures, in the crank case, of from below 0 F. in Winter to 150 F. or more in summer, and such variations in operating temperatures, with resultant variations in the vaporization and .condensation of thefuel, produce substantial varia. tions in the rate of dilution. Furthermore, the setttingof the carburetor, the improper use of the choke, and the mechanical 4condition of the engineparticularly the t of the 'piston rings in the cylindersT-as well as' the manner of use of the en gine, each contribute in varying degrees to the diluting tendency.

In order to maintain bricant above a certain critical value, it has been customary lto use an oil having a greater viscosity than is actually necessary, and then to drainthe crank case and replenish with fresh oil at the4 end of every ve hundred or onethousand miles of travel. But from a consideration of the abovementioned variable factors that affect the vis.- cosity of the oil, it is evident that the'rate of various devices for heating thelubricating oil` todrive 01T, by distillation,vthe more volatile gasoline or kerosene as soon as it is mixed with the oil. Such devices, aside from being complicated andA cumbersome, are disadvantageous in -that the additional heating of the oil tends to break it down by increasing the rate of carbonization. Furthermore, there is no way for the operator to know whether the device is functioning or not, and in the event that it should cease to function over a distance of two thousand miles, serious damage might result to the engine.v Other manufacturers have provided their engine crank cases with Ventilating means to carry oif any vapors 'of the diluting gasoline or kerosene, but devices of this sort are far from being elcient, and the operator is left totally in the dark.

'I'he foregoing and other objectionable features of the prior art are overcome by thepresent invention, which has for its object the provision of a novel apparatus for determining andindicating at all times variations in the lubricating properties of the oil in an automotive engine or motor while in operation.

In its broader aspects, the invention contemplates the determination of the lubricating prop- "erties of the oil by the translation of some other property. 'or condition into terms of viscosity.

More specifically, the method involved consists in passing a relatively small amount of the oil through a circulating system and creating therein a pressure which is a function of the viscosity of the oil. Variations in said pressure are measured by a suitable gauge or the like which may be calibrated to give an exact indication ofthe viscosity. 'I'hecirculatng system is preferably auxiliary to the regular lubricating system of the motor (being in the nature of'a by-pass in circuit therewith) and is provided at one point with. a pressure regulator which maintains a constant the viscosityof the lu pressurel onl the oil'at that point in the system and receives the oil from the usual pump thereof. From this point of constant' pressure, the oil is caused to flow successively-through a small bore capillary tube and a capillary orifice, one leading to and the other from a common pressure chamber. Since the oil `in flowingl through the tube and the orifice is obedient to diierent laws of flow, there will be created in the common chamcosity of the oil. It is this pressure which is utilized in operating the indicator, and consequently' any change of pressure due to' a changel of viscosity will be immediately registered by the indicator. In this way, the operator is advised at all times as to the viscosity of the oil and will know exactly when it has lost its lubricating value and needs replenishing. So long as the indicator shows the oil to possess the requisite viscosity under proper operating conditions, it

may be safely used as a lubricant without regardv to actual mileage or period of use of the engine.

The foregoing and other objects, features, and advantages of the invention will more readily appear from the following description in connection with the accompaning drawings, wherein the invention has been shown by way of illustration, and wherein:

Fig. 1 is a perspective view, partly broken away, showing one form of theinvention as applied to an automobile;

Fig. 2 is a vertical longitudinal sectional view through one form of the improved viscometer, and showing the indicating gauge associated therewith;

Fig. 3 is a side elevation of the viscometer; and

Fig. 4 is a top plan view thereof, partly broken away.

In Fig. 1, one form of apparatus has been shown as applied to an automobile, but it is to be understood that the invention is not restricted to such use, but may be employed with equal advantage in other automotive engines, such as for aviation and marine use, and in fact in lubricating systems of machines other than gas engines.

The apparatus comprises a viscometer I connected in a closed circulating system at one side of the engine 2, said system including an oil pump 3 of any ordinary or preferred type. The pump 3 draws oil from -a sump at the bottom of the engine crank case through a suction pipe 4, and forces said oil through a supply pipe 5 leading to the engine bearings. The pump 3 and pipes 4 and 5 are parts of the usual pressure lubricating system employed in automobiles, and this system is so well known as to require no further description.

The viscometer- I is connected to the supply pipe 5 by mean of a branch of a T 6, so that a small portion of the oil from the pump 3 is bypassed through the viscometer I and subsequently returned to the oil sump through discharge pipe 1. The oil passing through the viscometer I is caused to iiow in such manner as to create a pressure which varies (inversely) with the viscosity of the oil, and variations in s'uch pressure are adapted to be' registered by an indicator or gauge 8 on the dashboard of the vehicle, said gauge being connected with the viscometer by means of a pipe or tube 9.

Referring particularly to Figs. 2, 3, and 4, it will be seen that the viscometer unit I comprises a relatively shallow circular body portion I0 and a oil receiving chamber within which a constant pressure is'maintained on theoil by a Pressure regulator I3.

'I'his pressurey regulator comprises a flexible corrugated diaphragm I4, which formsthe upper wall of the pressure chamber I2, having a ceutral reinforcement I5 against which the lower end of a compression spring I6 bears. The spring I6 is confined withi a chamber I1 of a housing I8, which is secured, as by screw threads I9, to the body portion I0. The diaphragm I4 may preferably be soldered to an annular shoulder 20 on the body portion I0, or it may be clamped "in position between said body portion and the housing I8. The upper en'd of the spring I6 `bears against the shouldered inner end 2l .of an adjustable screw plug 22 in the upper end of the housing I8, and by turning said screw plug. the pressure ofthe spring against the diaphragm may be varied as desired.- The screw plug 22 is formed with a central bore 23 fora purpose to be explained hereinafter, and is locked in adjusted position by a screw cap 24.

In the center of the bottom wall of the chamber I 2, there is a flared opening 26 through which oil is adapted to ow into said chamber from a longitudinal bore 21 or passage in a downwardly extending boss 28 of the body portion I0. Disposed within the bore 21, below the opening 26, is

an oil strainer 29 of any desired construction, this strainer being clamped in the end of the bore 21 by means of a bushing 30, which in turn is held in place by a coupling nut 3l. The bushing 30 is secured to a nipple 32-.which branches out from seat tightly against the annular valve seat 38 surrounding the lower end of the opening 28. Normally, the pressure of the spring I 6, in acting upon the diaphragm I4, maintains the valve 35 in its open position, but ii the pressure of the oil 'within the chamber I2 should rise beyond a predetermined amount, the diaphragm will yield upwardly, drawing the valve stem 31 with it and causing the valve disc to approach the valve seat 38 and reduce the flow of the 'oil through the opening 28, therebyl maintaining a given constant pressure within the chamber I2.

In order to adjust thevalve with reference tol the valve seat, and thereby to4 vary the extent of its movement, the lower end of the valve stem` 31 is provided with a head portion having a screwdriver slot 39. Thus, when the body portion ofthe viscometer is disconnected from the circulating system, a screw-driver may be inserted in the bore 21 to turn the stem 31 in the reinforcing member I5. The stem is so proportioned that its threaded end extends beyond the upper side of the reinforcing member I5 for the reception of a lock nut 40, which may be loosened or tightened as desired by means of a socket wrench inserted through the bore 23 of the plug 22.

To providean outlet for the oil from the chamber I2, a coiled small bore or capillary tube 43 is embedded in the body portion I0, as best shown in Figs. 2 and 4. This tube 43'has its inlet end 44 extending upwardly into the chamber I2 and its outlet end 45 extending into a longitudinal bore or chamber 46' formed in the cylindrical exu of the cylindrical portion II, and in communication with the bore or chamber 46 therein, is a nozzle member 41 having at its lower end an annular wall 48 formed with a capillary orifice 49 which preferably is slightly larger than the mesh of the strainer 29 and which causes a turbulent ow. The wall 48 is tapered or flared both above and below the orifice to produce a sharp edge orifice, which is a type of orifice best suited for the present instrument. The orifice 49 discharges into the upper end of the return pipe 1,which may be secured to the lower end of the rcylindrical portion II by any ordinary or preferred form of coupling or union 50. A vent tube I, which is open at its upper end, is connected with the pipe 1 to maintain atmospheric pressure below the` orifice 49, altho a small vent cut through the pipe 1 would answer the purpose equally well.

In the prior art liquids have been passed through relatively large orifices to determine their viscosity, the use of such orifices in all instances being based upon the fact that the pressure drop causing the flow was substantially independent of the viscosity and consequently varies as the square of the velocity through the orifice. To

obey this law of flow with liquids of relativelyl high viscosity such as lubricating oils used in automobiles the size of the orifice and pressure -drop must besuch that a large amount of oil passes through the orifice, in fact many times that available in the lubricating system of an automobile.

I have discovered that when such liquids flow through a small orifice the flow is not independent of viscosity and consequently the pressure drop causing the flow does not very as the square of the velocity.. In the case of such an orifice the f law of flow (which I believe to be an entirely new discovery) is that the pressure multiplied by a factor (which is a function of viscosity but a constant for a given viscosity) is equal to the velocity to the nth power, n` being a continuous function of the viscosity. I have found that n varies continuously from about 2 in the case of water or liquids of substantially zero viscosity to about 1 in the case of liquids of high viscosity.

As is well known, the pressure drop to cause the flow ofthe liquid through a small bore or capillary tube is directly proportional to the velocity of the liquid. Likewise the pressure 'drop to cause flow is directly proportional to the ,viscosity. When n has a value of 2 the flow is substantially free from the effect of viscosity, the

pressure head being entirely transformed into velocity head. When n has a value of 1 the-ow is entirely viscous, the pressure head being utilized entirely in overcoming the shearingrhtl ance to flow. For intermediate values of n part of the pressure head is utilized to overcome shear and part is transformed into velocity head. As a consequence for all values of n greater than 1 the variation in the pressure drop to 'cause flow" have ascertained that such flow characteristics hold for small orifices of minute or pinhole order of magnitude. How large the capillary orifice may be made and still produce a flow which is dependent on the viscosity is still problematical and I am not now prepared to give any definite size limitsfor the orifice covering the range over which the lawset forth holds true.

,From the foregoing, it will be clear that any variation in the viscosity of the oil circulated through the instrument will result in a change of pressure within the chamber 46, and hence by a suitable calibration of the gauge 8, a direct reading in terms of viscosity can be had. Accordingly, .one end of the tube 9 is connected by a coupling or union 55 with the'upperv end of the cylindrical portion Il, the other end of said tube 9 extending to the gauge 8, which is located on the instrument board as previously explained. The gauge 8 may be .of ordinary commercial form having pressure-responsive means, such as a Bourdon tube, bellows, or diaphragm, to cause rotation of a pointer 56. The gauge 8 has a graduated dial reading from zero to 2 in a counterclockwise direction, the magnitude of the divisions gradually decreasing as they approach the value 2. The pointer 56 is shown pointing to the zero mark which corresponds to the maximum pressure within the chamber 46, which condition would result from the passage through the viscometer of a fluid having zero viscosity. This is an ideal condition which does not exist in reality, but which is closely approximated with Water.

, Under conditions of atmospheric pressure in the strument from the chamber I2 to the pipe 1 is constant, and since the same quantity of liquid flows through the capillary tube 43 and capillary orifice 49, it follows that the proportional distribution of this drop in the tube and orifice will vary as the viscosity varies. In consequence, the pressure. in the -chamber 46 relative to the atmosphere will vary, and this variation will be indicated by the gauge 8 connected thereto.

The proportions of the tube 43 and orifice 49 may be varied within reasonable limits and in accordance with requirements of design for particular instruments. By way of illustration, satisfactory results have been lobtainedwith the device shown in the drawings, wherein the orifice 49 is about .035 inch in diameter, and the tube 43 is about sa; inch in inside diameter and aboutk 5 inches in total length. The pressure main-9 tained within .the chamber I2 by the regulator I3 may be about three pounds to the squareinch, the spring I6 being adjustable merely to suit the calibrations of the gauge 8.

The relative arrangement of thesmall bore tube 43 and capillary orifice 49 can be reversed if desired but I prefer the first-disclosed ar. rangement wherein the oil rst flows through the tube and then through the orifice. As has previously been stated, with this preferred arrangement the pressure in the chamber 48 will varyl inversely with the viscosity, and this is desirable because it prevents any possible damage to the gauge when the viscosity is high due to low temperatures, as when starting the engine in cold weather. In yother words,as the viscosity decreases the pressure in the common chamber^46 increases, and the gauge can be so selected and calibrated, as to be capable of withstanding the maximum pressure caused by the flow of the change.

least viscous iuids. If the pressure were to vary directly-with the viscosity, it is conceivable that in startingl in cold Weather, the oil might be so thick as to create a pressure beyond the rangeof the gauge, causing injury to the instrument which would render it inaccurate and undependable in future use.

It will now be apparent that an apparatus has been provided for continuously testing, determining, and indicating the viscosity of the oil in an automotive engine while itis in operation, so that the operator will be advised at all times asto the actual lubricating value of the oil. When the indication given by the gauge 8 reaches a predetermined minimum -value for that Vparticular engine, he will know that the oil requires to be changed irrespective of the distance he might have travelled sincethe last But until such `indication is given, he will know that the oil is satisfactory for use and need not be Wasted. Thus the instrument is 'of great utility in that it saves tht engine when the oil is bad, and it saves the oil when the oil is good. y

Obviously. the invention is susceptible of numerous modifications in the construction of the apparatus, and the right vis herein reserved to 1. A viscometer for determining the viscosity of oil which is subjected to destructive iniiuences aiectingits viscosity, comprising an oil receiving chamber, a yieldable diaphragm forming one wall of said chamber, a spring acting on said diaphragm to maintain a constant pressureA within said receiving chamber, a pressure-regulating valve associated with the diaphragm to control the ilow of oil into the receiving chamber, a variable pressure chamber adapted to be supplied with 'oil from the receiving chamber and provided with a capillary orifice as an outlet for the oil, means for regulating the outlet pres'- 'sure at the orifice so that a constant pressure drop is maintained between the oil receiving itial and final pressures on the `fluid passing chamber and the outlet of the orice, a small bore capillary tube of substantial length for conducting the oil from the receiving chamber to said variable pressure chamber, said tube and orice being so proportioned as to cause viscous I ow through the tube and partially non-viscous ilow through the oriflce so asto create within the pressure chamber a pressure which is dependent upon the viscosity oi.' the oil, and means for indicating variations in said pressure in l0 terms of viscosity. y

2. A viscometerl of `the class described, comprising a casing having a shallow oil receiving chamber, a diaphragm forming a yieldable wall for said chamber, a self-alining valve associated lwith the 'diaphragm to control the ilow of oil f into saidreceiving chamber, -a compression spring acting against the diaphragm to maintaina substantially constant pressure in the receiving chamber, a line-mesh strainer through which oil isA caused to flow before entering said chamber, a'variable pressure chamber at one side of the receiving chamber, a. nozzle in the bottom of said variable pressure chamber and provided with an outlet orice slightly larger than the mesh of said strainer, -said orice leading into a conduit having an atmospheric vent, a'small bore tube for conducting the. oil from the receiving chamber to said variable pressure chamber, said tubeintermediate its ends being coiled beneath l the receiving chamber, and said tube and orifice being sotproportioned as to create within the pressure chamber, a pressure which is a, function of the lviscosity of the oil, andan indicator responsive to the variationsin pressure'in the 35 pressure chamber to indicate variations in viscosity. l

3. Apparatus for continuously indicating 'the viscosity oi a iiuid, which comprisesa variablepressure chamber, a capillary tube providing an inlet to said chamber,- a capillary orifice providing an outlet from' said' chamber, said capillary tube causing stream line ilow and the orifice causing turbulent iiow of the uid passing therethrough, means for maintaining substantially constant inthrough the apparatus irrespective of any change which may occui' in the fluid, and means for measuring pressure in said chamber to give an indication of the viscosity of the fluid at any time..4

' FREDERICK RAY.

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