US2457874A - Fluid level indicator - Google Patents

Description

Jan. 4, 1949.

A. H. DAVIS, JR

FLUID LEVEL INDICATOR Filed Dec. 20, 1943 FIG.

IN V EN TOR.

AROHIBALD H. DAVIS JR.

Mo ,4 TTO/F/VEY Patented Jan. 4, 1949 UNITED STATES PATENT OFFICE FLUID LEVEL INDICATOR Archibald H. Davis, IL, Cleveland, Ohio, assignor to. American Machine and Metals, Inc., East Moline, 111., a. corporation of Delaware Application December 20, 1943, Serial No. 515,011

.This invention consists of means adapted to respond to the arrival of a frothy fluid, such as preset level in ,8, 1'8- Variable factors that cannot readily be evaluated in advance may require using a quantity of the suds-forming ingredient that is not constant for each charge even though a given head of suds is to be attained and the amount of the other ingredient is always the same.

Such a problem is encountered'in the operation of an automatically controlled machine for washing fabrics. To secure satisfactory cleansing action such an amount of detergent must be added to the water as will build up a suds blanket of a given depth in any particular machine. However, not all the detergents added are available for forming suds. Many complex reactions take place between the soil contained in the fabrics that are being cleansed, the minerals or other materials in the water generally referred to as hardness of the water, and the detergents. As a result of these reactions a part of the detergent is used to form compounds with the soil and the hardness creating substances in the water. The quantity of detergents used in this manner varies in proportion to the amount of soil and the hardness of the water. Therefore, the total amount of detergent to be added to the bath to achieve the desired washing results will vary in propor- 2 Claim. (Cl. 171-411) -A further object of the invention is to provide a device permitting a suds-forming ingredient to be added without measurement to a bath and yet secure a predetermined proportion. The device comprises a pressure responsive cell which shuts oil the further flow of the suds-forming ingredient when there is a sudden change in the pressure acting on the sellers a result of the suds having risen to a desired height.

tion .to the larger or smaller losses of detergent I in the reactions just mentioned. Usually several successive suds treatments are applied to the fabrics and the amount of detergent used for other than suds-forming purposes varies in successive treatments.

It is an object of this invention to provide a method and apparatus which will permit detection from without a container when the frothy liquid reaches a preset level therein.

It is a further object of this invention to use the difference in frictional resistance to fluid flow offered by the air and a frothy fluid to operate an indicating -or operation-controlling device when the frothy fluid reaches a preset level.

A further object is to provide a device which responds when the top of the suds blanket extends a fixed distance above the previously fixed level of water, the response resulting from a change in suction exerted by a vacuum-creatingdevice that is operated by a means other than the fluid whose level is to be controlled.

A further object of the invention is to provide pressure responsive means which will detect when a fluid, which is composed at least in part of a liquid, reaches a preset level in a container wherein the operation of the pressure responsive means does not depend upon the particular specific gravity of the fluid whose level is being detected.

Another object of the invention is to provide means adapted to successively detect the arrival of one or more fluids in a container at successive levels.

Other objects of the invention will become apparent as the description proceeds, reference being made to the accompanying drawings in which:

Fig. 1 is an end elevation, partly in section, of a receptacle equipped with the invention and Fig. 2 is an elevation, partly in section, of a control box shown in Fig. 1 together with the mechanism controlled by circuits coming from the box.

l0 denotes a stationary receptacle adapted to be filled to a level-a with a liquid, such as water. A cylindrical container H for the material to be treated is rotatably supported on a shaft l2 supported by receptacle III. This shaft may be driven by any suitable mechanism, not shown, to agitate the contents of the cylinder in the liquid con tained inthe receptacle.

A pipe l3, provided with a contraction l5, connects a point in the receptacle ata level b which is above level a, to a vacuum-creating device I 4, such as a centrifugal exhaust pump. A pipe [6 branches off from pipe I 3 at a point intermediate the receptacle and the contraction i5 to a control box I! shown in detail in Fig. 2. Pipe l6 connects to a casting is that contains a suction chamber l8 and supports the rest of the mechanism. The suction chamber I8 is closed by a flexible diaphragm 2| whose edges are held firmly between a flange 20 of the casting l9 and a ring 22. A spring 23 tends to push the diaphragm outwardly. Ring 22 carries lu s 23 that pivotally support a lever generally indicated at 24. An arm 21 of the lever 24 has a projection 23 on one side and a light spring 29 is attached to its free end. This spring is anchored to a finger 30 carried by flange 20 of casting i9. Spring 23 tends to keep the projection 28 of the arm 21 in contact with the diaphragm 2i. A projection 32 on another arm 3| of lever 24 is adapted to limit the outward movement of the diaphragm pressing against projection 28 when projection 32 bears against a stop 33 on ring 22. A third arm 34 of lever 24 is adapted to close an electric circuit through contacts 35, 36 when the diaphragm 2| forces the lever 24 to rotate about its axis 25, bringing the stops 32 and 33 in contact, and to open the circuit when the suction in chamber it, together with the pull of spring 23, overcomes spring 23.

Contacts 35, 36 form part of an electric circuit of any type that is adapted to give a signal or to control an operation. Fig. 2 shows such a circuit 4 I, 42 coming from a controller not shown. When contacts 35 and 35 are in contact and the circuit 4 i, 42 is energized by the controller, that is not shown, current will flow from 4| thru solenoid 31, lead 40, contact 35 contact 35 to lead 42. This will open the valve 38 controlled by the solenoid and permit liquid to flow thru pipe line 38 into the washer as long as contacts 35 and 36 engage each other.

The invention will now be further described in its application to a washing machine in which fabrics are cleansed by agitating them in a bath of water to which suds-forming detergent is added. Assuming that ill and II are respectively, the outer shell and the rotatable cylinder of such a washing machine, that the pipe line 33 is the line through which suds-forming detergent is supplied by the washer, that the shell i is filled with water up to the level a in Fig. l, and that the rotatable cylinder Ii has been loaded with a certain weight of soiled fabrics, the operation of the device as has been described so far is as follows: while the cylinder II and its contents are agitated, detergent is slowly added through the pipe line 39 to the water in the receptacle ill, the circuit containing the solenoid 31 having been established by some agency such as a controller, in a manner well known in the art. As the detergent mixes with the water, part of the detergent combines with the soil of the garments and with solids contained in the water. It will depend upon the nature and the quantity of the soilpresent in the fabrics and of the minerals and other solid substances contained in the water, whether a smaller or a larger total amount of detergent will be necessary for the given volume of water to prepare a mixture in which there is neither too much nor too little detergent present. Where more of the detergent is combining with the soil and the solids in the water, a larger total quantity of detergent will have to be supplied in order to leave suificient iree'detergent for the process of forming suds.

On account of the variables Just mentioned it is not possible to determine the amount of detergent required to achieve the optimum'washing effect by way of adding such detergent in a constant proportion to the water. It has been found that a reliable indication as to when the addition of suds-forming detergent to the bath ought to be terminated resides in the arrival of the suds at a predetermined level situated a certain distance above the fixed water level. This discovery is described in detail in the application Serial No. 438,984, now Patent No. 2,430,668, of John W. Charnberlin, filed April 15, 1942, and assigned to the assignee of the present application. The level I; of Fig. 1 at which the conduit i3 opens into the receptacle i0 is the predetermined suds level just mentioned.

As long as the suds are forming on top of the water level a but have not reached the level b, the pump I4 is drawing air through the conduit i3. There will be a uniform drop in pressure along the conduit i3 due to friction, and a large drop will take place at the contraction l5 beyond the point where the suction chamber 13 is connected to the conduit l3. While under these conditions a slight suction is exerted'through the pipes i3 and it upon the suction chamber II, this suction is quite insufficient to overcome the force of the spring 23. The spring 23, therefore, keeps the diaphragm 2| pressed against the projection 23 of the lever 24, the latter maintaining by means of its arm 34 the contacts 35 and 35 in their closed position. Thus the circuit containing the solenoid 31 remains energized, keeping open the valve 38 in the pipe line 33 so that detergent is continuing to be supplied through the pipe line 39 into the receptacle ill.

When the suds blanket forming on top of the water rises to the level 12, the pump i4 which thus far has been drawing air into the conduit 13 draws a new fluid, suds, into the mouth of pipe i3. I have found that such suds offer a frictional resistance so much greater than the friction of the air to the passage through pipe l3 that a sharp increase in the suction in conduit l3 and particularly in chamber l3 will take place. This suddenly increased suction is strong enough to draw the diaphragm 2i inwardly against the action of the spring 23 permitting the spring 29 to turn lever 24 in a clockwise direction to release the contact 35 thereby interrupting the circuit of the solenoid 31. The detergent valve 33. no longer held in open position by the solenoid 31, closes the flow through the pipe line 33, thereby preventing the further supply of detergent to the bath in the receptacle ill.

The agitation that continues after the supply of detergent is shut off draws in air that tends to increase the height. of the suds blanket. At the same time, the soil still in the fabrics com blues with some of the detergent in the suds. thus tending to lower the suds level. Where several successive treatments are applied, in the first suds the latter tendency has the upper hand, so the suds level falls below level b. As the fabrics become cleaner in subsequent treatments the tendency of the suds to fall because the detergent combines with the soil decreases, and in later suds there is a tendency for the suds level to rise above 1). Experience has shown that if agitation is continued after the detergent supply is shut off for a fixed time the suds level rises to a, certain level and the fabrics may be considered. clean, except that the detergent must still be rinsed out. This upper suds level is indicated in Fig. 1 at c. For detecting the arrival of the suds at this level 0 a control device 43 similar to the control box I! just described in connection with the detection of the suds blanket at the lower suds level b is used. The inner construction of the box is the same as that shown for the box II in Fig. 2 and the suction chamber in the box 43 acumen is connected by means oi a branch pipe 44 to a conduit 48 entering the receptacle ID at the level 0. Beyond the pipe 44 the conduit 45 could be connected to the same pump l4 as is the conduit l3, but I have illustrated the conduit 4! as being connected to a separate vacuum creating device in the form of an ejector having a nozzle 41. The elector is operated by a stream of water passing through a pipe 4! controlled by a valve 48. Since the quantity of water passing through the pipe 48 is negligibly small compared with the body of water contained in the receptacle it, the water coming through the pipe 4! can be discharged into the receptacle ill, rather than into a sewer, without affecting the washing operation one way or the other. The ejector 46 draws air into and throughthe conduit 45 as long as the suds have not reached the level 0. When they do reach this level there is a sudden increase in suction acting upon the diaphragm in the control box 43 and the contacts in that control box are opened. These contacts form a part of a control circuit of the general type shown in Fig. 2. A solenoid similar to 31 may in this case operate arr-indicator that will indicate to the operator that the washing operation is complete and that the next stage, which might be rinsing, can commence. Or the solenoid 31 might cause the automatic control mechanism of the washing machine to shift from washing to rinsing upon completion of the suds treatment in progress, after the dump valve has finished discharging the spent bath.

The vacuum-creating device, whether l4 or 46. is operated by means other than the fluid whose level is to be detected. In the case of the ejector 46, for instance, a separate water supply line 48 operating the ejector is provided in addition to the detergent supply pipe 39. This makes the operation of the devices in the control boxes independent of the characteristics of the particular fluid upon whose arrival at a certain level some indication or controlling operation has to take place. Italso permits use of a common vacuumcreating device in connection with the control of the levels of a plurality of fluids, even though these fluids may be of different kinds, such as, e. g., suds and water. An arrangement or this kind is shown in Fig. 1 where the conduit it leading to the lower suds level I) as well as a conduit in communicating with the receptacle It at the level a which is the level to whlchthe receptacle is to be filled with water is connected to the exhaust pump l4. A control box 52 of a construction similar to that shown in Fig. 2 for the control box I1 is connected by means of a pipe II to the conduit 50 intermediate the two ends of the latter, and a contraction i3 is provided in the conduit 50 at a point between the pump l4 and the branch pipe M. The electric contacts in the control box 52 may operatea solenoid 54 controlling the water inlet valve 55 of the washing machine. i

, The device 52 operates in substantialhr the same manner as the device l1. -As long as the water which may be supplied to the receptacle It by a pipe 56 has not reached the predetermined water level a, the pump i4 draws air through the conduit 50 and the suction active through the scribed in connection with the control box ll,

the air and a' suction of greater strength develops v =in the suction chamber or the device 52. As a result of this suddenly increased suction the diaphragm of the device I2 is drawn inwardly against the forceor its coordinated spring 23, the contacts 35, 88 are broken in the manner dethe solenoid I4 is deenergized and the valve 85 in the water pipe 58 closes.

ll. This is, however, inconsequential since the device in the control box 52 will operate to open the contacts all, 36 in that box as soon as the first drops of water are drawn into. the pipe. This takes place long before the pipe actually becomes branch pipe 5! upon the diaphragm in the box I! is too small to permit an inward flexure of that diaphragm. When the water reaches the level a at which the conduit 80 is connected to the receptacle ll, water, instead of air, enters the conduit ill. The water oflersa very much higher resistance to the action of the pump l4 thandid tilled with liquid.

As has been mentioned before, the conduit 45 could also be connected with the pump l4 from which, according to Fig. l, the conduits i; and 50 are branched oil, so that the arrival of the water at the level a as well as the successive rise of the suds first to the level b and then to the level e would all be detected and made use or under the action of suction brought about in all three cases by one and the same vacuum-creating device H.

Where several level-detecting devices are connected to the same vacuum creating device, it will be useful in certain cases to provide some or all of the conduits leading from the receptacle Hi to the common pump or the like with valves for cutting off the particular conduit when the detesting device to which that conduit is coordinated operates its diaphragm. I have indicated such a valve at 5'! behind the contraction 53 in the conduit 50. This valve may be controlled by a solenoid 58 arranged in parallel to the solenoid 84 so that the watersupply valve 55 and the valve 51 in the conduit 50 will open and close in unison. In this manner little or no liquid is drawn over into the pump because the flow is cut oi! as soon as the level has been detected.

It will be apparent from the foregoing description that the application of my invention is not limited by such considerations as whether or-not the frothy fluid whose level is to be detected differs much from air in specific gravity. The operation of a detecting device built according to the invention repends upon the property or such fluid to offer, when sucked into a tube or the like, a larger flow resistance than does air, and if this property is present in a fluid, it does not matter if its specific gravity is different from the specific gravity of air to an extent only which cannot be detected readily as is the case, for instance, with the suds referred to repeatedly in this specification.

While I have described my invention in its application to a washer, I desire it to be understood that the invention is not restricted to such appllcation. It is applicable wherever a process involves the formation of a frothy fluid, e. g, foam or suds, by mechanical or chemical action, and the arrival of this frothy fluid at one or more prescribed levels has some bearing upon the progress or the termination of the process. It is further to be understood that while I have shown in the drawing a certain embodiment of the invention, this embodiment has been given by way of example only and that various changes, rear-- rangements and modifications may be made withthe scope of the appended claims.

acumen What I claim is:

1. Apparatus including an aspirator drawing fluid continuously through a tube ,connected to the side of the tank which responds to the arrival or the surface of liquid being poured into the tank to the level of the entrance of the tube into the tank by indicating the increased suction required to draw liquid fluid rather than gaseous fluid through the tube Comprising, in combination, a tank, a tube entering the tank at a given height above its bottom, a contraction in the tube, an aspirator beyond the contraction continuously drawing fiuid from the tank through the conduit and the contraction, means responding to the pressure differential between the entrance of the tube into the tank and a given point in thetube between the tank and the contraction, means preventing the pressure-responsive means for responding to pressures up to the suction pressure developed by the aspirator when drawing a gaseous fluid through the tube.

2. Apparatus including an aspirator drawing fluid continuously through a tube connected to the side of the tank which responds to the arrival of a layer of foam rising in a tank to the level of the entrance of the tube intolthe tank by indicating the increased suction required to draw a foamy mixture of liquid and gas rather than gas alone through the tube comprising, in combination, a tank, a tube entering the tank at a given REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 1,548,186 Claude -1 Aug. 4, 1925, 1,560,111 Riedel Nov. 3, 1925 1,745,859 McElroy Feb. 4, 1930 1,905,172 Howse Apr. 25, 1933 2,027,417 Clurman Jan. 14, 1936 2,121,324 Manley June 21, 1938 2,218,698 Clark Oct. 22, 1940 2,278,769 Chayie Apr. 7, 1942 2,305,154 Gilbert Dec, 15, 1942 2,379,338 Bingman June 26, 1945 2,379,396 Ziliotto June 26, 1945

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