US2300642A

US2300642A - Gas drawing apparatus

Info

Publication number: US2300642A
Application number: US254223A
Authority: US
Inventors: George M Booth
Original assignee: Wallace & Tiernan Co Inc
Current assignee: Wallace & Tiernan Co Inc; Wallace & Tiernan Company Inc
Priority date: 1939-02-02
Filing date: 1939-02-02
Publication date: 1942-11-03
Anticipated expiration: 1959-11-03

Description

Nov. 3, 1942. G, Boom 2,300,642

GAS DRAWING APPARATUS v Filed Feb. 2, 19:59 4 Sheets-Sheet; 1

f INVENTOR A; ATTORNEY 1942- 4' G. M. BOOTH ,300,642

' GAS DRAWINGQPFARATUS Filed Feb. 2, 1939 4 Sheets-Sheet 2 A; ATTORNEY Nov. 3, 1942. G. M. BOOTH 2,300,642

GAS DRAWING APPARATUS Filed Feb. 2, 1939 A 4 Shets-Sheet 3 1 Q ZZNVENTIOR A; ATToiQNEY Nov. 3,1942. BOOTH 2,300,642

GAS DRAWING APPARATUS Filed Feb. 2, 1939 4 SheetS -Sheet 4 V ullvNvENTOR 2mm 1,; ATfoRNEY Patented Nov. 3, 1942 GAS DRAWING APPARATUS George M. Booth, Westfleid, N. J., assignor to Wallace & Tiernan Company,- Inc., Bellevilie, N. 3., a corporation of New York Application February 2, 1939, Serial No. 254,223

' 17 Claims. (01. 210-28) -This invention relates to apparatus for drawing gas at a controlled rate into flowing liquid. The invention comprises an improved Venturi aspirator having means adjustable for varying its pulling capacity, and comprises, also, automatically acting control means for adjusting the adjustable means of the aspirator to maintain constant under varying conditions a desired negative pressure between the suction inlet of the aspirator and a flow-controlling orifice or other flow-resisting passage through which the gas is drawn.

An object of the invention is to provide an aspirator having means for adiustably controlling its pulling capacity such that as the pulling capacity is varied the flow rate ofwater through the aspirator will be varied more nearly. in proportion to the variation in pulling capacity than has been possible with the means heretofore employed for varying the pulling capacity of aspirators, and thus to provide an aspirator which will operate with good emciency through a comparatively wide range of gas flow rates or with varying liquid supply pressure. Another object is to provide an aspirator whereby when there is a negative pressure on the discharge line from the aspirator the suction, or pulling capacity, of

the aspirator may be reduced. without reducing the liquid flow rate below a certain minimum. A further object is to provide means for automatically controlling the adjustment of the aspirator so as to control accurately the pulling capacity of the aspirator to maintain a desired negative pressure in the gas passage leading to the suction inlet of the aspirator under varying rates of gas flow, varying pressures in the discharge line whether superatmospheric or subatmospheric, and varying liquid supply pressures.

The invention has been made especially with the idea of providing an improvedapparatus for introducing gaseous chlorine at a. controlled rate into a minor stream of water to produce a solutionto be used for the treatment of water or sewage or for other purpose. In such apparatus in which chlorine gas supplied at a constant substantially atmospheric pressure is drawn through a flow-controlling orifice bya water aspira'tbr, it

has been the practice to have the pulling capacity of the aspirator somewhat greater than sufllcient to draw gas at the maximum desired rate through the control orifice and to have the excess capacity of the aspirator satisfied by makeup water supplied tothe suction inlet of the aspirato'r under a negative head which deter- 55 the water pressure to the aspirator is reduced to mines the partial vacuum, or negative pressure, available for sucking the gas. In some cases the negative head under which the make-up water is supplied to the aspirator is constant and the suction transmitted to the control orifice is deter- I mined by an adjustable, restriction between the orifice and the aspirator, and inother cases the flow rate of the gas is varied by varying the negative head against which the make-up water is supplied to the aspirator. Also, instead of supplying make-up water to satisfy" the excess capacity oi the aspirator in order to maintain the desired negative pressure at the suction inlet, the pulling capacity of the aspirator has been controlled to maintain a desired negative pressure at the suction inlet by regulating the operating pressure oi the water supplied to the aspimtor by means of a valve in the supply line.

Adjusting the pulling capacity of the aspirator by regulating the operating pressure oi the water has the advantage over supplying make-up water under a negative head to satisfy excess capacity of the aspirator that the aspirator maybe operated by the minimum amount of water required to maintain the desired negative pressure at the suction inlet, thus effecting economy in the use of water, and that the solution of gas produeed is of greater strength.

This method of controlling the pulling ca-- pacity of the aspirator is, however, open to two objections. First, since the emcien'cy ofva Venturi aspirator decreases greatly as the pressure of the operating fluid decreases. the eiilciency of the aspirator is greatly reduced when the flow rate of the gas is low, that is, the proportion of water to gas is increased largely as the flow rate oi the gas is reduced. The other defect of this method of controlling the pulling capacity of the aspirator is manifested when the discharge line from the aspirator extends considerably downward and the syphon effect in the discharge line tends to'produce a suction through the aspirator which at times may be suificient to produce the desired negative pressure at the suction inlet without any water at all passing through the asplrat'or. In the use oi an aspirator provided with such means for controlling its pulling capacity and discharging an amount below that required to dissolve-the sucked-in gas. As the proportion of undissolved' gas increases in the discharge line, the syphon effect is decreased and the negative pressure at the suction inlet decreases below that desired and the water supply pressure-is thereby increased until the discharge line again becomes filled with water. This cyclic operation continues, making it dimcult to regulate the aggregate gas fiow with any good degree of accuracy, and in many cases the varying strength of the solution produced and the presence of some undissolved gas is objectionable.

The new invention makes it possible to have the variation in proportion of water flow rate to gas flow rate over a comparatively wide range of gas flow-much less than when varying the pulling capacity of an aspirator by varying the operative pressure of the water, and to have the amount of water passing through the aspirator always sufiicient to dissolve the gas regardless of any degree oi suction in the discharge line.

An aspirator according to the invention comtive pressure maintained in the suction passage by the aspirator.

In the operation of the automatic control mechanism, any increase in the vacuum or negative pressure at the suction inlet of the aspirator beyond that desired causes a forward movementof the aspirator plug to reduce the pulling capacity of the aspirator, and if the negative pressure at the suction inlet is less than that desired, the plug will be moved backward to increase the pulling capacity of the aspirator. For varying gas flow rates, the water supply pressure to prises 'aF'Venturi tube having a gas suction inlet at its throat and means for adjustably varying the cross-sectional area of the throat to vary both its pulling capacity and the liquid fiow rate through a range extending down to a minimum throat cross-section, and for further reducing the pulling capacity without, further reducing .the throat cross-section and liquid flow rate. As new found most desirable, the suction inlet orifice is in the form of an annular slot opening through the throat wall, and the liquid flow, until a point of minimum cross-area is reached, and then by further forward movement of the plug the critical cross-section of the throat is advanced withrelation to the suction inlet without substantially changing the cross-area of the critical cross-section, of the throat, thereby further reducing the pulling capacitybut not reducing, or substantially reducing, the liquid flow rate. y

In a complete apparatus according to the invention for drawing gas at a controlled rate into flowing liquid embodying the automatic control feature 01' the invention, the gas: is drawn into the Venturi aspirator through a passage leading from a flow-controlling orifice or passage to the aspirator and the discharge pressure remaining constant, the plug will be moved backward to increase the pulling capacity for an increased gas flow rate, and will be moved forward to decrease the pulling capacity for a decreased gas flow rate; and with the Venturi tube and the plug properly shaped, although the liquid flow may not vary just proportionately with the gas flow, the aspirator will operate with good efficiency and the variation of the ratio of water flow to gas flow will be much less than with the apparatus hereinbefore referred to in which the pulling capacity of the aspirator is controlled by varying the operating pressure of the liquid. If, for a given gas flow rate and back pressure on the discharge, the liquid supply pressure varies, the aspirator plug will be adjusted in response to the resulting variations in the negative pressure at the suction inlet in order to adjust the pulling capacity to maintain such negative pressure constant. So, also, the plug will be automatically adjusted to adjust the pulling capacity of the aspirator to maintain the suction inlet negative pressure constant under pressure variations in the discharge line from the aspirator; and if the discharge line back pressure becomes subatmospheric to such a degree that the resulting suction from the discharge line in addition to that created by the aspirator increases the vacuum, or negative pressure, at the suction inlet above that required, the plug will be moved for ward into that range of its movement in which forward movement reduces the pulling capacity without further reduction in the flow rate of the water: and the aspirator should be so designed that this minimum water -fiow rate is always suflicient to dissolve the gas drawn into the which the gas is supplied at a controlled pressure,

and means responsive to variations in the negative pressure in the passage leading to the suction inlet of the aspirator controls the position of the tapered plug in the throat of the aspirator to vary the pulling capacity 01' the aspirator to maintain said negative pressure constant. The

apparatus will usually, also. include means for trolling orifice and the aspirator suction inlet,

or means may be provided for varying. the nega- .75

water.

A full understanding of the invention can best be given by a detailed description of an apparatus for supplying chlorine at a controlled rate in solution in water embodying the various features of the invention in the form now considered best, and of two modified forms of such apparatus, and such a description will now be given in connection with the accompanying drawings. In said drawings:

Fig. 1 is a diagrammatic sectional view 01' the apparatus of the fonn now preferred;

Figs. 2, 3 and 4 are sectional views of the Venturi aspirator on a larger scale showing respectively the adjustable plug in three diflerent positions;

Fig. 5 is a cross-sectional view taken on line 5-5 of Fig. 3; and

Figs. 6 and 7 are views similar to Fig. 1 but illustrating modified forms of apparatus.

Referrin to the drawings, and first to Figs. 1 to 5, chlorine gas from a suitable source under pressure, suchas a tank of compressed liquid chlorine, is supplied through a tube III to a pressure reducing valve I I of suitable construction by which the gas is supplied at a constant substantially atmospheric pressure to a flow-controlling a tube 3|.

orifice I2. The gas is drawn through the flowcontrolling orifice by the suction of a water aspirator I5. A float chamber I6 is connected between the orifice l2 and the aspirator by passage I1 from the orifice to the float chamber and passage l8 from the float chamber to the aspirator, and the outlet I9 from the float chamber to the passage I8 is restricted by a float-controlled valve 20. In operation the aspirator maintains a partial vacuum, or negative pressure, in the pas- 1 sage 18 which exceeds the negative pressure deand, therefore, the desired pressure drop across the orifice l2, and the operation of the valve controlling means is adjustable for changing the negative pressure transmitted to the orifice to change the drop in pressure across the orifice and thereby the rate of flow of the gas; and the operation of the aspirator is automatically controlled to adjust its pulling capacity to maintain the desired negative pressure in the passage 18.

Water is raised in the float chamber l6 against a negative head by the negative pressure, or partial vacuum, in the chamber, and the valve 20. the position of which determines the negative pressure maintained in the chamber and transmitted to the orifice, is controlled by a float 2| in the chamber to which as shown in Fig. 1 the valve'is directly connected. If the negativ pressure in the chamber 6 exceeds the negative head against which the water is raised in the chamber, the water level in the chamber rises and the float is raised and the valve is given a closing movement to increase the resistance to outflow of gas from the chamber and thereby reduce the vacuum within the chamber and passage l1, and if the degree of vacuum is less than said negative head the water level falls and the float moves downward and the valve is given an opening movement to reduce the fiow resistance through the outlet, thereby increasing the vacuum in the chamber and passage IT. The negative head against which the water is raised by the negative pressure in the chamber thus determines the degree of vacuum, or negative pressure, maintained in the chamber, and, therefore, the drop in pressure across the orifice and the flow rate of the gas.

The float chamber is supplied with a constant small flow of water through a tube 23 from a suitable source of supply, the flow to the chamber being controlled. most desirably, by a constant flow rate valve 24, and the water flows from the chamber through a downwardly extending tube 25 which connects to an upwardly extending tube 26 to form a U-tube. From the overflow outlet 21 at the top of tube 26 the water falls into a chamber 30 from which it flows to waste through The negative head against which the water is raised in the float chamber by th negative pressure in the chamber will thus depend on i th overflow outl t 21 and the the eleva'non o e e 1939. granted on my co-pending application *Serial No. 96,242. Means such as shown in said To 'co-pending application for power-operating the air pressure at the outlet. Instead of varying this negative head by varying the elevation of the overflow outlet, the overflow outlet 21 is, in the construction shown, fixed and the chamber 30 is a closed chamber, and the desired negative head is obtained by establishing a suitable negative pressure in this chamber, and desired change in the negative head and resulting change in gas flow rate is efiected by adjustably changing the negative pressure in this-chamber. As shown, the overflow outlet 21 is positioned at approximately the normal operating level of the water in the float chamber. With the overflow outlet so positioned, the same degree of vacuum will be maintained in the float chamber and passage ll as is established in the chamber 30.

Any suitable means may be provided for pro- 2 ducing the desired degree of vacuum in the chamber 30 and for varying the degree of vacu- .um either automatically or at will. As shown,

the water discharge tube 3| is a vertical tube large enough sothat the amount of water overflowing from the outlet 21 will not cause the tube to run entirely full and yet small enough so that the tube will be sealed and that air will be carried down with the water. A partial vacuum is thus produced in the chamber 30; and the degree of vacuum so produced is determined by the depth of submergence in the water in chamber 30 of the discharge end of an air inlet tube 32. Air from the tube 32 bubbles up through the water when the degree of vacuum in the chamber 25 is greater than that corresponding to the depth of submergence of the discharge end of the tube, and such air is carried out through the vacuumcreating discharge tube 3|. The depth of submergence of the discharge end of tube 32 will 30 thus be the measure of the degree of vacuum maintained in chamber 30, and this vacuum may be varied by varying the depth of submergence of the discharge end of the tube. To provide forv such adjustment, the tube 32 is a vertical tube slidablyadjustable through a stuifing box 33 in the top wall of the chamber 30. The drop of the tube 3! should be sufilcient to produce a degree of vacuum in chamber 30 in excess of any required in the operation of the apparatus.

If the gas is supplied to the control orifice l2 at just atmospheric pressure and the overflow outlet 21 is positioned atthe operating level of the water in the float chamber, the drop in pressure across the orifice I2 will be equal to the deree of vacuum maintained in chamber 38, and the depth of submergence of the end of the air tube 32 in inches will be the measure of the drop in pressure across the orifice as expressedin inches of water. If the gas is supplied to the orifice at a pressure slightly below atmospheric pressure, then in order to obtain a given pressure drop across the orifice, the degree of vacuum maintained in chamber 30 should be increased by an amount equal to the negative pressure under which the gas is supplied to the orifice or the overflow outlet should be lowered a corresponding number of inches; and if the gas is supplied to the orifice at a pressure slightly above atmosphere, then for obtaining the,given pressure drop across the orifice the degree of vacuum main-; tained in chamber 30 should be reduced or the overflow outlet 21 raised accordingly.

The means shown and above described for producing a desired negative head against which the water is raised in the float chamber and for varying such negative head is disclosed and claimed in Patent No. 2,158,976, dated May 16,

valve 20 under control of the float instead of having it operated directly by the float maybe used to obtain greater accuracy and steadiness in maintenance of the desired negative pressure in the float chamber and passage ll.

Water is supplied under suitable pressure to the aspirator l through an inlet pipe 40 and discharged with the induced gas through a delivery pipe 4| which may extend upward or downward from the aspirator and deliver into water or other liquid under pressure or not, so that the discharge from the aspirator maybe against a negative head or may be against a positive head provided the operating pressure under which the water is supplied to the aspirator is sufllciently greater than theback pressure on the aspirator.

The aspirator l5 consists essentially of means providing a passage for the water having an entrance portion which tapers from large to small in the direction of flow of the water and an annular gas inlet at or just beyond the small end of such tapering portion, and a tapered adjusting member mounted concentrically within the passage, the greatest diameter of which member is slightly less than the smallest diameter of the passage, and which is adjustable axially for varying the minimum cross-area of the annular space between the plug andthe passage wall until by forward movement itsportion of greatest diameter is at the small end of said tapered entrance portion of the passage, and may be adjustably moved further forward to move its portion of greatest diameter past the annular gas inlet so that the minimum cross-area of the annular flow-way is not substantially changed but the critical cross-section of the throat is advanced with respect to the gas inlet. The aspirator is end of the tapered entrance portion the .passage is, in the particular form 'of aspirator shown, cylindrical. The block 45 is connected at its intake side 'to the inlet pipe 40 and at its 50 which is tapered both forwardly and rearwardly froma zone or part of greatest diameter which is slightly less than the diameter of the cylindrical portion of the passage in the block 45. The plug is carried by a rod 5i which extends through an opening in a boss at an elbow of the inlet pipe 40 and through a stufiing box 52, so that it is movable endwise for adjusting the plug 50 axially in the throat of the Venturi tube. For holding the plug in coaxial position within the tube, it is provided with three guide fins 53 which extend with an easy fit to the walls of the cylindrical portion of the tube. The tapered inner portion of the plug 50 co-acts with the tapered entrance portion 01' the bore of the block 45 to form the entrance portion of the Venturi passage for converting pressure energy of the water into velocity energy, and the tapered which forms the main wall of the passage, or a conduit, which part or parts will hereinafter be referred to as a Venturi tube, being so formed as to provide the essentials of a Venturi tube,

that is, a flow passage comprising an entrance portion, or cone, which tapers from large to small in'the direction of fiow and a delivery or discharge portion with tapers from small to large and which is joined to the entrance portion by a throat or portion of minimum cross-section, the two tapering portions being of limited angle between the walls. As in the conventional Venturi tube, some of the pressure energy of the water in passing through the entrance cone is changed into velocity energy with reduction of trance portion and the throat of the bore or passage -o1- the Venturi tube are formed in a block of suitable material, which in the particular apparatus illustrated will be a material resistant to wet chlorine. The annular gas inlet orifice 46 is a narrow slot opening from an annular passage 41 to which the gas tube I8 connects, and is located just beyond the small end of the tapered entrance portion of the passage; and for a short distance beyond the small outer end portion of the plug co-acts with the cylindrical portion of the bore through the block 45 to form the inner end portion of the diverging pressure-building part or the Venturi passage which is continued by the outwardly expanding tube 48.

In Fig. 2 the adjusting plug 50 is shown in a withdrawn position for maximum water flow and maximum pulling capacity of the aspirator. Fig. 3 shows the position of the plug when it has been moved forward just far enough to reduce the waterflow to the minimum. By adjustment of the plug between these two positions, the cross-area of the critical cross-section of the Venturi throat is varied, thereby varying the pulling capacity of the aspirator and, with a tube of the form shown, water flow, with change in the efllciency of the aspirator which is small as compared to the change in efilciency of an aspiratorof which the pulling capacity is varied by adjusting the water supply pressure. By moving the plug further forward from the position of Fig. 3, as to the position shown in Fig. 4, the critical cross-section is advanced with relation to the gas inlet slot without further reducing its cross-area, whereby the pulling capacity of the aspirator is further reduced without reducing the water flow rate.

The shape of the walls of the Venturi passage may, of course. be varied somewhat, but it has been found best to make them approximately as shown, that is, with the passage in the block 45 cylindrical for a short distance beyond the gas inlet slot for guiding the fins 53, and with'the tapered entrance portion of the. outer wall and the forwardly tapered portion of the plug concavely tapered so that, except when the plug has been moved forward beyond the inlet slot, the high velocity liquid as it passes from the critical cross-section will flow inward away from the inlet slot to leave space for the induced gas,

The important advantage which the new invention has over the old method of adjusting the pulling capacity of the aspirator by varying the pressure of the operating water applied thereto,

of maintaining a high efiiciency of the aspirator for varying gas flow rates, is shown by the result pressure, the ratio of water flow to gas flow in creased from 40 gallons per pound of chlorine when the gas flow was at the rate of 6000 pounds of chlorine per day to 90 gallons per pound of chlorine (125% increase) when the gas flow was at the rate of 2000 pounds per day, and to 120 gallons per pound of chlorine (200% increase) when the gas flow was at the rate of 1000 pounds per day; while with the new aspirator, the variation in gallons of water per pound of chlorine was only between 30 and 40 (33%,% increase) when the rate of gas fiow per day varied between 6000 pounds and 2000 pounds, and between 30 and 60 (100% increase) when the gas flow varied between 6000 and 1000 pounds per day.

In the apparatus shown, the plug 50 is adjusted automatically in response to variations in the negative pressure in gas flow tube (8 to maintain a desired negative pressure in said tube. The end of the plug rod is connected to a diaphragm 55 mounted in a diaphragm housing 56 rigidly connectedto the inlet pipe 40. The housing chamber or space above the diaphragm is open to atmosphere, and a spring 51 biases the diaphragm downward. The chamber beneath the diaphragm is a closed pressure chamber to which a small flow of water is sup- Water will thus be supplied constantly to the container mat a low rate and will be withdrawn from-'the container through the tube 13 when there is a suflicient degree of vacuum in the gas suction tube 18 to overcome the negative head in the tube 13, the water entering the tube Hi from tube 13 passing into the throat of the aspirato'r together with gas from chamber iii.

In the operation of the apparatus, if by the negative pressure in the gas suctionpassage l8 water is withdrawn from the container 10" through the tube 13 faster than it flows into the container from tube H, the weight of water in the container will decrease and the container end of the normally balanced lever 65 will rise under pressure of spring 61 on the other end of the lever and the valve 63 will be given a closing movement. By such throttling of valve 63, resistanceto outflow of water from chamber 58 will be increased, thereby raising the pressure on diaphragm 55 by which the diaphragm and plug rod 5| are moved upward against the pressure of spring 51, moving plug 50 upward, or forward, in the Venturi throat, thereby reducing the minimum cross-section of the aspirator throat and reducing the pulling capacity and'water conf sumption oi the aspirator. This upward movement of the plug rod 5! will also by'upward plied under suitable pressure through a supply tube 60 and through a suitable flow-limiting means, most desirably a constant flow rate valve 6| which permits only a very small flow of water. The pressure within the chamber 58 is relieved by flow through a tube 62 and past valve 63 to waste through waste outlet 6h The pressure relief tube 62 as shown leads from the chamber 58 but might equally well lead from the tube 60 between the flow-limiting valve 6| and chamber 58 as in.the apparatus of Figs. 6 and "I. If the water is permitted to escape freely through tube 62 no pressure will build up in the chamber 58, but if the outflow of water is restricted pressure will build up in the chamber to a degree dependent on the resistance to flow through the. valve 63.

Valve 63 is controlled according to the suction exerted by the aspirator by means responsive to variations in the amount of water in a container to which water is supplied at a constant very low rate and from which a tube extends upward to the gas suction passage I 8. As shown in Fig. 1,

movement of collar 68 relieve somewhat the downward load of spring 61 on the left hand end of the lever, thus tending to balance the decreased weight of water in the container. The decrease in weight of water in the container due to excessive suction through the tube 13 and the resulting increase in pressure'on diaphragm 55 will continue until the pulling capacity of the aspirator has been decreased to that required to maintain a degree of vacuum or negative pressure in the passage l8 sufiicient to withdraw water through tube I3 at the same rate as water enters the container through valve 8|. This negativepressure will be that desired to be maintained'in passage l8 as determined by the negative head in tube 13.

If, on the other hand, the aspirator is operating with a pulling capacity insuflicient to withdraw water from the container H! as fast as it enters the container, the weight of water in the container will increase and the container end oi the lever 65 will fall, thereby opening valve 63 and reducing the resistance to outflow of valve 63 is connected to a lever 65 pivoted at 66 on a support extending from the diaphragm housing 56. The inner or short end of the lever is biased downward by means of a spring 57 the upper end of which bears against a collar 88 fixedly attached to the plug rod 5|. The other,

long, end of the lever beyond the point of connection of the valve 63 carries a container 70 to which water is supplied at a low constant rate from tube 60 through a tube H and constant flow rate valve or other suitable flow-limiting device 12. A tube 13 extends downward from gas suction passage "3 to near the bottom of the container 10, the ends of both tubes II and 13 having no physical connection with the container.

rod 5| will then be moved downward by spring 51 to move the plug backward in the Venturi throat, increasing the minimum cross-section of the throat and thereby increasing the pulling capacity of the aspirator. At the same time downward movement of the rod 5! increases the pres sure of spring 61 on the left hand end of the lever, and the lever will again become balanced when the pulling capacity or'the aspirator has been increased to that required to maintain a negative pressure in passage it Just sufiicient to withdraw water from the container at the same rate that water enters the container, that is, when the negative pressure in thepassage I8 has been restored to that desired as determined by the negative head in tube 13.

The pulling capacity or the aspirator will thus be automatically adjusted to maintain the de-- sired negative pressure in the passage I8 for drawing the gas at a rate determined by the ad- Ju tment of valve 26, and this automatic adjustment of the pulling capacityjoi the aspirator by movement of its adjusting plug 58 will follow either a change in adjustment of the valve 28 for changing the gas flow rate, or a change in the pressure under which water is supplied through pipe III, or a change in the back pressure against the discharge from the aspirator whether such' back pressure is positive or negative, all, of course within the operating range oi. the apparatus.

If the arrangement of the delivery pipe is such that the aspirator discharges against a negative head, this negative head, or partial vacuum, increases the suction of the s irator on the gas passage I 8, and to compensate for this increased suction the plug will be automatically adjusted as above stated; The negative head on the discharge may be so great that, because of the suctiontransmitted therefrom to the gas inlet orifice of the aspirator, the; pulling capacity of.

the aspirator will for the then gas flow rate be excessive even with the plug advanced to the minimum critical cross-section position shown in Fig. 3. Then in response to such excessive degree of vacuum in the, passage l8, the plug will be further advanced to reduce the pulling capacity or the aspirator without further reducing the water flow until the suction on the gas inlet orifice is reduced to that which will maintain the desired negative pressure in the passage i8.

to variations in the negative pressure in the gas 5 suction passage l8, and that it has no means for automatically controlling the restriction between the how -controlling orifice and the aspirator.

The adjustable restriction between the gas flowcontrolling orifice l 2 and the aspirator is a handadjustable valve 28a by adjustment of which the negative pressure transmitted to the flow-controlling oriflce may be varied to vary the drop in pressure across the orifice and thereby the rate oi. gas flow, the negative pressure in the gas flow passage 18 leading to the gas inlet of the aspirator being maintained constant. Instead of having the valve which controls the outlet to waste of water passing the flow-limiting valve 8|, and thereby the pressure on the diaphragm for determining the position of the aspirator plug 50, controlled as in Fig. l by means responsive to variations in the amount of water in a container the amount of water in which varies according to variations in the nega- 55 tive pressure in the gas suction passage I8, this valve 63a is controlled by a diaphragm 80 mount ed in a housing 8| which provides a closed chamber above the diaphragm to which the tube 13 leading downward from the gas flow passage I8 connects. The valve 63a is connected to the diaphragm 88 by a rod 82, the valve casing extending downward from the lower wall of the diaphragm housing. The chamber beneath the diaphragm is vented to atmosphere through an 5 opening 83, and a spring 84 bearing on a collar 85 on the valve rod tends to move the diaphragm and valve downward to hold the valve in open position.

In operation, if the aspirator is operating with too great a pulling capacity, so that the negative pressurein the gas suction passage i8 is greater than the desired negative pressure for which the apparatus is adjusted, the diaphragm .88 will be liited against the downward pressure of 7 1 spring 8|,thereby throttling valve 53a and causing an increase of pressure in chamber 58 whereby diaphragm 55 and rod 5| are moved upward and the aspirator plug 50 is adjusted upward to decrease the pulling capacity and water consumption of the aspirator.

aspirator has been reduced to that required to maintain the desired negative pressure in pas-- sage l8, while drawing in the gas at the rate for which the flow-adjusting restriction formed by valve 20a is set, the upward pull of the diaphragm then balancing the downward force of spring 84.

If the aspirator is operating with a pulling capacity not suflicient to maintain the desired negative pressure in passage l8, the suction on diaphragm will be insuflicient to resist the downward force of spring 84, and valves 63a will be opened with a resulting decrease in pressure on diaphragm 55, and diaphragm 55 and rod 5| will move downward under pressure of spring 51, withdrawing plug 58 and thereby increasing the ilowof water through the aspirator and its pulling capacity. This increasing of the pulling capacity of the aspirator will continue until the desired negative pressure is being maintained in passage l8, the upward pull of the diaphragm 80 then balancing the downward pressure of spring 84.

The pulling capacity of the aspirator of this Fig. 6 apparatus will thus be automatically adjusted and maintained at that required to maintain a desirednegative pressure in the passage I8 while withdrawing the gas at a rate determined by the adjustment of valve 20a, and, as in the case of the apparatus of Fig. 1, this automatic adjustment of the pulling capacity of the aspirator will follow either a change in adjustment of valve 28a for changing the gas flow rate, or a change in water supply pressure, or change in the back pressure against the discharge from the aspirator. And if the discharge is against a suflicierit negative head, the aspirator plug 58 will be advanced beyond its first position of minimum throat cross-area to further the throat, and, therefore, without changing the water iiow rate.

In this Fig. 6 apparatus, the negative pressuremaintained in passage 18 is not determined, as

- it is inthe apparatus of Fig. 1, by a negative head in tube 13, and therefore does not depend on the vertical length oi. tube 13, but is determined by the force or spring 84 tending to open valve 53a and working against the upward pull of the diaphragm resulting from the negative pressure in passage iii. The negative pressure in passage i8 will thus depend on the strength of spring 84 which is adjusted to that required to balance a desired degree of vacuum on the upper side of diaphragm 80. For making such adjustment, the collar 85 is, most desirably, made adjustable by being supported by a nut threaded on the valve stem 82. This adjustment of the force of spring 84 by changing the position of collar 85 on rod 82 may also be made to serve the purpose of adjusting the apparatus to maintain different desired negative pressures in the passage l8. By so varying the negative pressure maintained in the passage l8, the gas flow rate 4 may be varied without change in adjustment of the valve 288:, and this might be relied on for varying the gas flow rate instead of providing The parts will come to balance when the pulling capacity of the supply tube 60 and flow-limiting valve 6|.

an adjustable valve or restriction between the flow-controlling orifice and the aspirator.

The automatic aspirator adjusting means of Fig. 6 does not give quite such close adjustment of the pulling capacity of the aspirator and such steady maintenance of a constant negative pressure in passage It as that of Fig. 1, since it does not have any reacting means such as the spring 61 of Fig. l, the loading of which is varied by movement of the plug adjusting rod to dampen such movement through its action through the lever on the valve.

Fig. 7 shows an apparatus in which the adjustment of the aspirator plug is controlled by a member the position of which is determined by the level of a body of water which is raised by the suction of the negative pressure in the gas suction passage working against a negative head which determines the negative pressure maintained in the gas suction passage, that is, between the flow-controlling orifice and the aspirator, by varying which negative head the negative pressure maintained constant in the gas suction passage may be varied as, desired to vary the gas flow rate by varying the drop in pressure across the flow-controlling orifice.

As shown ,in Fig. 7, the control member of this apparatus is a float 90 in a float chamber 9| connected between passage leading from the flow-controlling orifice l2, to which the gas is supplied at a constant substantially atmospheric pressure by pressure reducing valve II, and a gas suction passage leading to the aspirator. The position of the aspirator plug 50 is controlled, as in Figs. 1 and 6, directly by diaphragm 55 through rod 5|, pressure water being supplied to the diaphragm chamber 58 through The pressure relief tube 621) through which the pressure in chamber 58is relieved discharges into float chamber 9| past a valve 63b under control of the float 90. The relief tube 6% has at its end within the float chamber a downwardly opening valve seat to cooperate'with valve 63b carried directly by the float.

As in Fig. 1, the water constantly supplied to chamber 9| through tube 621) flows from the.

chamber through a U-tube'25, 26, the upflow leg 26 of which discharges through an overflow outlet 21 into a negative pressure chamber 30 from which the water flows to waste through a tube 3|, the negative pressure in chamber 30 being adjustable by varying the depth of submergence of the end of air inlet tube 32, as more fully explained in the description of the apparatus of Fig. l. y

If the negative pressure in the float chamber exceeds the negative head against which the water is raised in the chamber, the water level in the chamber rises and the float rises and valve 63b is given a closing movement. Such throttling of the valve 83b causes an increase of pressure in diaphragm chamber 58 whereby diaphragm 55 and rod 5| are moved upward and the aspirator plug is adjusted upward to decrease the pulling capacity of the aspirator, thereby decreasing the degree of vacuum in passage l8 and in float chamber 8|. If, on the other hand, the aspirator is operating with insufiicient pulling capacity so that the negative pressure in passage i8 and chamber 9| is less than said negative head, the water level falls and the float moves downward and valve 63b is given an opening movement, whereby the flow resistance from tube 62b is reduced with a resulting decrease in pressure on 76 diaphragm 55, permitting he diaphragm and rod 5| to be moved downward under pressure of spring 51 to withdraw plug 50, thereby increasing the pulling capacity of the aspirator.

If by adjustment of air inlet tube 32 the negaa tive head on the float chamber is increased, the water level in chamber 9| and float will fall untilby the resulting adjustment of the aspirator plug the pulling capacity of the aspirator has been increased to increase the negative pressure in suction passage l8 and float chamber 9| to equality-with the negative head; and if the negative head is decreased, the float will rise, causing an opposite adjustment of the aspirator plugto decrease the pulling capacity of the aspirator until equality between the negative pressure and the negative head is again attained. Such variation of the negative pressure maintainedin the assage It by varying the negative head on the water in the float chamber serves for variably adjusting the gas flow rate. With this apparatus, also, as with the apparatus of Figs. 1 and 6, the aspirator plug is automatically adjusted to maintain the desired negative pressure in passage it under variation in water supply pressure and under variation in the back pressure against which the aspirator discharges.

What is claimed is: 1

1. A Venturi aspirator for drawing gas into a stream of operating liquid, comprising a Venturi tube having a suction inlet for the gas at the throat thereof, and means adjustable for varying the pulling capacity of the aspirator and the liquid flow rate by varying the cross-area of the critical cross-section of the throat down to a certain minimum and for further reducing th pulling capacity of the aspirator without substantially reducing the cross-area of the critical cross-section of its throat below said minimum, said means comprising an adjustable member within the Venturi tube.

2. A Venturi aspirator for drawing gas into a stream of operating liquid, comprising a Venturi tube having a suction inlet for the gas at the throat thereof, and an adjusting member mounted within the tube and movable airially therein. by forward movement of which member to a certain point the cross-area of the critical crosssection of the throat is reduced to reduce the liquid flow rate and the pulling capacity of the aspirator, and by forward movement of which beyond said point the critical cross-section of the throat is advanced with relation to the suction inlet to reduce the pulling capacity without substantially .reducing the liquid flow rate.

3. A Venturi aspirator for drawing gas into a stream of operating liquid, comprising a Venturi tube having a circumferential gas inlet at the throat thereof, and an adjusting plug tapered in both directions from a zoneof maximum diameter mounted co-axially within the tube and adjustable axially therein, by forward movement of which plug to a certain point the cross-area of the critical cross-section of the throat is reduced to reduce the liquid flow rate and the pulling capacity of the aspirator, and by forward movement of which beyond said point the critical cross-section of the throat is advanced with relation to the gas inlet to reduce the pulling capacity of the aspirator without substantially reducing the liquidflow rate.

4. A Venturi aspirator for drawing gas into a stream of operating liquid, comprising a Ven-' turi tube having a circumferential gas inlet at the throat thereof, and an adjusting plug tapered in both directions from a zone of maximum diameter mounted coaxially within the tube and adjustable axially for varying the pulling capacity of the aspirator, the entranc portion of the Venturi tube being taperedadjacent the throat and the portion just beyond the gas inlet being cylindrical, the plug having guide fins to engage said cylindrical portion of the tube, and the forwardly tapered portion of the plug being concavely tapered adjacent its part of greatest diameter, and the plug being adjustable between a position in which its zone of maximum diameter is in the entrance part of the throat and a position in the cylindrical portion of the throat beyond the gas inlet.

5. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, or a Venturi aspirator having a gas inlet at the throat thereof for drawing th gas through said flow-controlling means comprising a Venturi tube having a circumferential ga inlet at the throat thereof, and an adjusting plug tapered in both directions from a zone of maximum diameter mounted coaxially in the tube and adjustable axially therein, by forward movement of which plug to a certain point the cross-area of the critical cross-section of the throat is reduced to reduce the liquid fiow rate and the pulling capacity ofthe aspirator, and by forward movement of which beyond said point the critical cross-section of the throat is advanced with relation to the gas inlet to reduce the pulling capacity of the aspiretor without substantially reducing the liquid flow rate; and means responsive to variations in the negative pressure in the gas passage between the flow-controlling means and the gas inlet of the aspirator for adjusting said plug to vary th pulling capacity of the aspirator to maintain said negative pressure substantially constant.

6. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, and means responsive to variations in the negative pressure in the gas passage'between the flowcontrolling means and the gas inlet of the aspirator, for adjusting said adjustable means to vary the pulling capacity of the aspirator by reducing the minimum cross-area of the Venturi throat when said negative pressure increases and by increasing the minimum cross-area of the Venturi throat when said negative pressure decreases, thereby to maintain said negative pressure substantially constant.

7. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, a pressure chamber, means responsive to variations in the pressure in said chamber for adjusting said adjustable means, means for supplying water at a limited flow rate to said pressure chamber, an outlet passage for said water, a valve for controlling said outlet passage, and means responsive to variations in the negative pressure in the passage between the flow-controlling means and the gas inlet of the aspirator for adjusting said valve to cause through variation in the pressure in said pressure chamber adjustment of said adjustable means to increase the pulling capacity of the aspirator by increasing the minimum cross-area of the Venturi throat when said negative pressure is less than the desired pressure and to decrease the pulling capacity of the aspirator by decreasing the minimum cross-area of the Venturi throat when said negative pressure is greater than desired, whereby said negative pressure is maintained substantially constant.

'8. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, a container, means for supplying a small continuous flow of water to the container, means providing a passage from the container upward to the passage between the flow-controlling means and the gas intake of the aspirator, a lever by which said container is carried, means for applying to the lever in opposition to the. weight of the water in the container a force which is varied by movement of said adjusting means, andmeans responsive to movements of said lever for adjusting said adjusting means to increase the pulling capacity of the aspirator when the container moves downward and to decrease the pulling capacity of the aspirator when the container moves upward.

9. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, a container, means for supplying a small continuous flow of water to the container, means providing a passage from the container upward to the passage between the flow-controlling means and the gas intake of the aspirator, a lever by which said container is carried, means for applying to the lever in opposition to the weight of the water in the container a force which is varied by movement of said adjusting means, a pressure chamber, means responsive to variations in the pressure in said chamber for adjusting said adjusting means, means for supplying water at a limited flow rate to said pressure chamber, an outlet passage for said water, and a valve for controlling said outlet passage controlled by said lever.

10. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturiaspirator having a, gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity'by varying the minimum cross-area of its throat, a pressure chamber, means responsive to variations in the pressure in said chamber for adjusting said adjustable means, a valve for controlling the pressure in said pressure chamber, a pressure chamber connected to the gas intake of the aspirator, and means responsive to variaascents tions in the pressure in said last mentioned pressure chamber for controlling said valve.

11. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum'cross-area of its throat, a pressure chamber, means responsive to variations in the pressure in said chamber for adjusting said adjustable means, means for supplying water at a limited flow rate to said pressure chamber, an outlet passage for said water, a valve for controlling said outlet passage, a pressure chamber connected between the flow-controlling means and the aspirator, a float in said chamber, means for maintaining water in said chamber under a negative head, and means controlled by said float for adjusting said adjustable means to increase the pulling capacity of the aspirator when the float moves downward and to decrease the pulling capacity of the aspirator when the float moves upward.

13. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means,

a pressure chamber, means responsive to varia-' tions in the pressure in said pressure chamber for adjusting said adjustable means, means for supplying water at a limited flow rate to said pressure chamber, an outlet passage for said water leading to said float chamber, a water out let from said float chamber, means for maintaining a negative head on said outlet, and a valve controlling said outlet passage and controlled by said float to be opened by downward movement of the float and closed by upward movement of the float.

15. The combination with flow-controlling means and means for'supplying gas at a controlled pressure' to said flow-controlling means,

of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, a float chamber connected between the flowcontrolling means and the aspirator, a float in said chamber, a pressure chamber, means responsive to variations in the pressure in said pressure chamber for adjusting said adjustable means, means for supplyingwater at a limited flow rate to said pressure chamber, an outlet passage for said water leading to said float chamber, a water outlet from said float chamber, means for maintaining a negative head on said outlet, a valve controlling said outlet passage and controlled by said float to be opened by from the float chamber for varying the nega tive pressure maintained in the gas flow passage. 16. The combination with a Venturi aspirator for drawing gas into a stream of operating liquid of a Venturi aspirator having a gas inlet at the supplied to it under pressure, comprising a Venturi tube having a suction inlet for the gas at throat thereof for drawing the gas through said I flow-controlling means and having means adjustable for varying its pulling capacity by varying the minimum cross-area of its throat, a float chamber connected between the flow-controlling means and the 'aspirator, a float in said chamber, means for maintaining water in said chamber under a negative head, means controlled by said float for adjusting s'aid adjustable means to increase the pulling capacity of the aspirator when the float moves downward and to decrease the pulling capacity of the aspirator when the float moves upward, and means for varying the negative head on the water outlet from the float chamber for varying the negative pressure main: tained in the gas flow passage and thereby the flow rate of the gas.

14. The combination with flow-controlling means and means for supplying gas at a controlled pressure to said flow-controlling means, of a Venturi aspirator having a gas inlet at the throat thereof for drawing the gas through said flow-controlling means and having means ad'- justable for varying its pulling capacity by varying the minimum cross-area of its throat, a float chamber connected between the flow-controlling means and the aspirator, a float in said chamber,

the-throat thereof, of a gas passage leading to the suction inlet, and means responsive to the negative pressure in said gas passage for varying the cross-area of the critical cross-section of the Venturi throat to reduce the pulling capacity of the aspirator by reducing said cross-area when said negative pressure increases and to increase the pulling capacity of the aspiratorby cross-area of the critical cross-section of the throat, and means responsive to the negative pressure in said gas passage for adjusting-said member to reduce the pulling capacity of the aspirator by reducing said cross-area when said negative pressure increases and to increase the pulling capacity of the aspirator by increasing said cross-area when said negative pressure decreases.

Gnomes: M. BOOTH.