US2583986A

US2583986A - Atomizer system

Info

Publication number: US2583986A
Application number: US521549A
Authority: US
Inventors: Jr Agnew H Bahnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-02-08
Filing date: 1944-02-08
Publication date: 1952-01-29
Anticipated expiration: 1969-01-29

Description

Jan- 29, 1952 A. H. BAHNsoN, JR

ATOMIZER SYSTEM 2 Sl'IEETS-SHEET 2 Filed Feb. 8, 1944 Wi au l y 5 Patented Jan. 29, 1952 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to atomizer systems of the type in which a liquid is projected from an atomizer head or nozzle, by a pressure gas, and particularly to an atomizer system including de vices for automatically controlling the operation o1' the system and for interrupting the ilow of both fluids in the event of an inadvertent failure or substantial decrease in the supply of either one of the fluids.

For simplicity of terminology, the invention will be described as embodied in humidiiier systems but it is to be understood that the control elements may be incorporated in systemsfor atomizing other liquids with air or other gaseous mediums, and that the control elements may be of the illustrated air-operated type or of an electrically-operated type.

The initial cost of the atomizer head or spray nozzle type of humidifier is relatively low but the operating costs of the conventional type atomizers used in such humidifier systems have been relatively high. By using an atomizing principle that requires both air and water under pressure the operating costs of such systems may be substantially lowered. Ordinarily no provision has been made for maintaining automatically a constant operating differential between the air and water pressures supplied to the humidifier system.

Objects of the present invention are to provide novel and eicient atomizer systems of the type in which a gas and a liquid are supplied under pressure to one or more atomizer heads. An object is to provide atomzer systems of the type. stated which include control devices for regulating the rate of fioW of one or both of the iluids by adjustment of the pressure on one or on both of the fiuids. An object is to provide an atomizer system in which a predetermined differential is maintained between the pressures at which the fluids are delivered to the atomizing heads. Another object is to provide atomizer systems of the type stated that include control devices for automatically interrupting operation in the event of' a complete or a substantial failure in the supply of either of the pressure fluids. Other objects are to provide novel control elements for use in atomizer systems of the type stated.

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Fig. 1 is a fragmentary, and somewhat schematic view, of a humidifier system embodying the invention;

Fig. 2 is a substantially central section through 2 the modulating dead-end valve in the water supply line of the humidifier system;

Fig. 3 is a central section through a modulating air control cartridge;

Fig. 4 is a fragmentary central section through the modulating pressure-control valve in the air Supply line of the humidifier system;

Fig. 5 is Ia fragmentary, and somewhat sche-` matic, view of another embodiment of the invention;

Fig. 6 is a fragmentary elevation, with parts in section, of an air cartridge and associated control elements on the water supply line; and

Figs. 7 and 8 are substantially central sections through an atomizer of the Fig. 5 humidifier system, the atomizer being shown in closed and in open position, respectively, in Figs. 7 and 8. i

.In the atomizer system of Fig. 1, the air line I and the water line 2 deliver their respective uids to a plurality of atomizers 3 under the control of, and at pressures determined by, air cartridge 4 actuated by a regulating element 5 that, inthe humidifier system, is a humidostat located inthe room or space within which the relative humidity is to be maintained substantially constant. For simplicity of illustration, various unions or pipe couplings that are present in a system of piping have been omitted from the drawings. Manually operable gate valves 6 are preferably provided at the opposite ends of the sections of the fluid supply lines I, 2 on which the control and indicating elements are located, thereby permitting an isolation of the control section for inspection or repair. 'lhe atomizers 3 may be of the type, as

Vdisclosed in my prior application Serial ..No'.

446,506 on which Patent No. 2,382,124 has issued, in which the liquid is under greater pressure than the gas.

The power medium for actuating the control and regulating elements is air under pressure that may be delivered from some independent source or, las illustrated in Fig. 1, may be tapped :from the air line I through a reducing valve 9 that.

maintains a substantially constant pressure at the inlet line IU of the air cartridge 4. Pressure gages II, I2 are preferably arranged on the airline IIJ to the Iair cartridge and on the outlet line I3, respectively. The control air line I3 extends to the air motor of the modulating air valve I4 to regulate the air pressure at the atomizers 3 in accordance with the load demand as determined by the air cartridge 4 and humidostat 5.

A reducing valve I5 and pressure gage I6 are preferably arranged on the air line I between the strainer 'I and air valve I4 to establish a definite Y end milling tool.

normal pressure, and a measure of the pressure, of the air supply to the valve I3. Another gage I'I is preferably located in the air line I beyond the valve I4 to register the pressure at which air is supplied to the atomizers 3.

On the water supply line .Z, a reducing valve I8 and a gage i9V are arranged between the strainer 8 and a modulating water supply valve and control unit that is identified in Fig. l by the reference numeral 26. The detailed construction and method of operation of this assembly will be described later and, for present purposes of description, it is stated that the pressure on the water line 2 beyond the control unit is determined by the displacement of the movable element of an air cartridge 2i in accordance with the air pressure at the atomizers 3, the air pressure at the controlled section of the air line I being transmitted to the air cartridge 2| through a pipe connection 22. A pressure gage 23 is located on the water line 2 beyond the con-V trol unit 26 to register the pressure at whichY Water is supplied to the atomizer 3. A bleeder Yline 24 extends from the outlet side of the Vcontrol unit20 to the control air line I3 of the modulating air Valve Id and, as will be explained later, the bleeder line 24 is opened when the water pressure drops below a` preselected value, thereby venting the control line to close the modulating air valve I4. A pipe 2 5 extends from the outlet side of the control lunit silto drain some or all of the Water from the end section of the water line 2 when the Vatomizer'system is shut ofi by an upward closing movement of the three-way valve The control unit 26 on the water supply line 2, as illustrated in Fig. 2, comprises a dead end reducing or pressure modulating valve and associated control elements within a casing '26 that has an interior wall Z'I providing inlet and outlet chambers" 28, 29 respectively to which the supply and delivery sections of the water line 2 are conpressure modulating valve -46 is open, and is opened to the outlet chamber 23 when the modulating valve is closed. An adjustable check valve 47 controls the ow of water from the waste chamber 46 to the waste pipe 25, thereby trapping water under a desired pressure, according to the setting of the check valve All, in the pipe line 2 between the control unit 26 and the atomizers 3. The check valve 4l prevents a drainage of water fromthe pipe line 2 but reduces the water pressure to a value belowY that at which water may leak from the atomizers 3 when the atomizer systemis not in operation. When other operating conditions remain constant, variations in water supply pressure at the valve at act upon the diaphragm 32'to move the water modulating Y valve -36 to compensate for the change in supply nected. The stem 3| of the pressure'modulating valve is urged towardsV closed position by water pressure on a diaphragm 32 in the inlet chamber and by an adjustable spring 33, and is moved towards valve-opening position by an air motor 34 that receives pressure air from the cartridge 2| through a connecting pipe 35. The modulating valvecomprises an inverted hollow body 36 threaded on the stem 3| and having longitudinally extending arcuate grooves 3! milled in its exterior surface. When the grooves are cut with a thin, disk-shaped cutter, the lower or shallow ends of the grooves are fllled'wth solder 3,3 to insurean abrupt opening of the valve after an initial idleV displacement of the valve body 36. Alternatively, the grooves may be stopped short of the end of the valve body when cut by an A cap 39 is threaded on the valve body 36 and carries a'gasket 46 for sealing the modulating valve against leakage when in valve-closed position. The cap 39 is ofannularv` form and the flanged upper section 4I of the stern of a waste valve 42 rests upon and is pressed into engagement with the inner surface of the cap 39 by a spring 43 within the hollow valve body 36. The Vdownward movement ofV valve stem 3| brings the valve 42 into engagement with a Vvalve seat 44 onv the bottom cap 45 of the valve casing 26V just before the grooves 3T of valve body 36 establish communication between the inlet chamber 28 and the outlet chamber 29. The waste or drainage chamber 46 in the cap 45 is therefore closed to outlet chamber 23 when the,

pressure and thereby maintain a constant water pressure at the atomizers 3.

.The bleeder valve @Momentos the bleder line 24 and `control air line i3 to atmosphere througha Vent port (not shown) in the wall of the valve chamber is biased towards open position by a spring 43 but is normally closed by the Water pressure exerted on a diaphragm 5t though a channel 5I that opens into the inlet chamber Z8 of the control unit 2li. A drop in the pressure of the water supply below a preselected value required for eincient operation results in an opening of the bleeder valve 33; thereby venting the control air line I3 and closing the air modulating valve 'III'J and, as explained'hereinaftenthis ine terruption of pressure air in the forward section of air line AI leaves'the control air line 2Q 'without pressure and results in a closure 'of the water modulating valve 36 by spring 33 and the water rapid reduction in the ratev of water supplyto the atomizers 3 in the event of a decrease in the air pressure at .the atomizers. This mechanism andthe cartridge 2! constitute 'a safety system for avoiding a short period supply of water to the atomizers at a high rate that precludes eilicient atomization. An increasing load demand results in an increasing air pressure at the atomizere 3 as the modulating air valve It opens. and inV a corresponding increase in the water pressure since the water modulating valve unit 26, as will be explained, responds to the increasedairpressureat the forward section of air line I .Z'QWhe'n the load demand decreases, however,4 the'air pressure drops more rapidly than the water pressure and'. to avoid wetting the water pressure must be relieved momentarily by a discharge of water through the waste pipe 25. An appropriate construction for the air cartridge will be described in detail hereinafter and, -for'purpose Voi the present explanation, it is stated that upward movement of the stem' effects a progressive increase in the pressure at which control air from pipe 22 is supplied tov the air motorv 34 through the cartridge outlet connection 35, i. e. in a progressivemovernentof the water modulating valveV 36 towards fully open position. The stern .E2 of the air cartridge is biased towards valve-open position byV a .spring 53 that is arranged between the top of the cartridge 2l and a iloating seat 5ft. that is urged downwardly, to oppose the spring 53, by a spring 55 between the seat 513 and a lever t pivot'ed asaaeee Water valve. yThe springs 53, 55 are so related, with respect to the compression of spring 55 as the `valve stem 3| is moved downwardly by an increasing demand for water to maintain the desired humidity condition, that the water pressure at the atomizers 3 exceeds the air pressure at the atomizers by a substantially constant pressure difference. A lever 59 is pivoted on a bracket 60 mounted on the casing 26 of the modulating water valve, one end of the lever extending through an opening intheiioating spring seat 54 and the other end carrying a spring finger 6| that engages a. ratchet bar 62 on the valve stem 3|. The spring finger 6| functions as a pawl that permits free downward movement of the valve stem without an accompanying counter-clockwise movementV of the lever 59, but the pawl and ratchet turnr the lever 59 clockwise, upon `upward movement of the valve stem 3|, in response to adecrease in the control air pressure applied to the air motor 34 from the forward section of the air supplyl line and the air cartridge 20. The stem 52 is thereby moved downwardly by the lever 59 to force the air cartridge to closed position to interrupt the supply of control air to the air motor 34 and to bleed the air motor to atmosphere. The water modulating valve 36 is closed by the spring 33 and the water pressure on the diaphragm 32, and the valve stem 3| lifts to carry the ratchet bar 62 above the spring finger or pawl 6| of the lever 59. The air cartridge 2| again controls the air pressure at the motor 34 as soon as the water modulating valve reaches closed position to free the lever 59 from the ratchet bar 6|, but the momentary closing of valve 36 and the opening of valve 42 permits water `to waste through check valve 41 to pipe 25 and thereby lower the pressure of the water supply to the atomizers 3, thus positively precluding an excess discharge of water upon a decreasing load demand and a drop in the air pressure at the atomizers 3.

i The air cartridge 2|, which preferably is substantially identical with the air cartridge 4 that is controlled by the humidostat 5, comprises a casing or shell 63 that may be mounted on any convenient bracket or support by bolts 64. The pressure air pipe, which is the connecting pipe 22 to the air supply line I for the air cartridge 2|, opens into the pressure chamber 65 through a filter 6B and port 61. The upper wall of the pressure chamber is a diaphragm 68 that carries the main valve 69 that has a stem 52, see Fig. 2, extending above the diaphragm for cooperation with control devices that may be the springs 53, 55 and associated mechanism for the air cartridge 2| of Fig. v2 or may be the humidostat for the air cartridge 4 of Fig. 1. The main valve 59 is of generally cylindrical forinwith a series of ne grooves l of differenti lengths broached into its peripheral surface, an intermediate reduced diameter section including an annular bead 1| for engagement with a gasket or valve seat 12 to seal the main valve when in closed position, and a stem 13 that extends be low the outlet passage 14 to engage the upper end of the leak port valve 15. The cylindrical surface of the valve 15 is provided with grooves 16 of different lengths -to lbleed air from outlet passage 14 and control line I35 in accordance with the adjustment of the valve 15. The vent chamber 11 below valve 15 is open `to atmosphere through a groove 11' in the stem 13 of the vent port valve. Valve 15 is urged .towards bil (Sil

closed position -byvaispringf19 that is seated between an adjustable plugwl andar-adial flange 82 on the valve stem that-carries a gasket '33 for cooperation with anannular bead 34' on the body of the air cartridge to form a secondary valve that seals the leak port valvewhen in fully elevated or closed position.

The described air cartridge provides a modulation of the air pressure at the outlet passage 14 oi the cartridge by the progressive opening of the grooves 16 of the main valve 69 as it is moved upwardly under the force of spring 19 and the air pressure within the chamber 65, upon a decrease in the force exerted upon the stem 52 by a control device. The leak port valve 15 is also of the modulating type and is urged towards closed position by the spring 19.

The three-way air valve |4 in the supply air line is similar in general construction to the modulating water valve unit 20 but of simpler design since, as illustrated in Fig. 4, thel air valve does not include the check valve assembly 41 in the lower cap or the bleeder valve 48 of the water modulating valve. Those elements of the air valve |4 that may be or are substantially identical with corresponding parts of the water valve unit 2|) are identified by the same reference numerals but will not be described in detail. The lower cap 45 is a shallow plate threaded into the lower end of the valve body 26 and having a central opening in' which the guide cylinder and vent 46 is xed. The pressure air within the forward section of the supply air line llmay be vented directly to atmosphere at the lower end of the vent 46' but, preferably, a vent pipe extends fromthe vent 46 to some remote point at which theescape of air, and incident noise, will not result in disturbance or annoyance.

The atomizer control system illustrated in Fig 5 has the same general operating characteristics, and the major elements, i. e. reducing valves, gages, air and water control valves, as the previously described system, and such elements as are or maybe substantially identical with corl responding elements of the Fig. 1 apparatus are identified by the same reference characters. The differences between the two systems are found in the arrangement and correlation of the control air lines that regulate the operation of the control valve elements in the air supply line and water supply line 2 on which a series of atomizers 3' are arranged. The atomizers 3 are of such construction, Aas will be described later, that they become operative at a preselected water g pressure, and the control air linesare so regulated by the air cartridgev 4 and humidostat 5 that pressure -airis supplied to air line and pressure water is then supplied to the water line 2. Specific values will be recited to facilitate an understandingof the operationl of the atomizer system Vbut it is-to be understood that the invention is not limited to the recited values.

The primary control of V thel modulating air valve |4 by a humidostat 5 Vis effected byu an air cartridge 4 in a control air 1ineidentied generally as control line A, that is substantially identical with the previously described control line that is tapped from-the main supply air line and includes a pressure reducing valve 9. a gage the air cartridge 4, a gage I2 and a control air line I3 Vto the modulating air valve |4. A control air line. B connects control air line A to the air motor 34 of the modulating water valve 20 ythat maybe identical with the valve assembly i1lustratedin Fig. 2 except for the elimination f tne'bieeder'vaive 4s audits associated e1emen'ts.- The air'fpressure at the supply end of air line I maybe about 35 pounds per square inch, and the reducing valve Si drops the control air pressure at the air cartridge 4 to about 20 pounds. The air motor of the modu lating air valve vI4 is adjusted to open at this control air pressure as soon as the air' cartridge 4 is actuated by the humidostat 5 upon a drop of the relativeV humidity below a preselected value. The water modulating valve 20' and its air motor 34 are adjusted,`however, to prevent opening of the water valve 20 until the control air pressure at the air motor 34 rises'to aboutk 30 pounds per square inch. This' increase in control air pressure is developed through the control line C that extends between a point on air supply line I, beyond Athe modulating valve I4, and the control air line A in advance of the air cartridge 4. A check valve 90 on control line C opens for control air flow in only the direction indicated by the arrow tc'prevent a bleeding of control air into vthe forward section of the supply air line l' when the modulating air valve I4 is closed.

The reducing valve I5 on air supply line i may be adjusted to deliver air at about 30 pounds per square inch at the inlet of the modulating air valve I4, and the pressure in the forward section of the air line I 'may vary between about 25 to 30 pounds in accordance with the control. air pressure at the air motor o'i the modulating air valve I4. The initial opening of the valve le therefore results in an increased control an' pressure in control line A, due to air flow through control line C, and this increased control air pressure is transmitted through lines A and B to elect a somewhat greater opening of air valve I4 and the opening of the water valve 20. The opening 'of the air valve I4 a few seconds before water reaches the atomizers 3' results in some waste of pressure air and tends to drop the pressure in the supply air line I, but this loss is only momentary and may be held to a minimum by providing a metering orifice 9| on supply air line I to limit air flow beyond or, as illustrated, to the reducing valve l5, and by appropriate design of the atomizers 3', as will be described later.

AV predetermined differential is established between the air pressure and the water pressure at the atomizers 3 by thev described control system, and this differential is maintained in spite of slow changes in the pressure at which air is delivered to the supply airline I by a compressor. The supply water pressure is approximately constant under all normal operating conditions as the water supply line 2 is usually connected to the'local water system. Sudden changes in the available supply air pressure. including a complete failure of supply air, result in control operations similar tothe normal shutting :down of the humidier system by the humidostat 5. The modulating water valve 20' must be closed quicklyto prevent a discharge of Water drops from the atomizers 3' upon a sharp decrease in air pressure at the atomizers.

Assuming normal operation, decreased air pressure results from the reduction in control air pressure at line I3 as the air cartridge 4 is closed by the humidostat 5. TheV airv cartridge 4 acts quickly to lower the air pressure at line I3 which delivers control air to the control line B of water valve' 20' and air valve I4. The water valve 20 thus closes quickly, but the closing of the air Vvalve I4 is ydelayedby a control air line Dthat extends -from the supply air line I, at a point beyond thereducing valve I5, to the air cartridge 92 that is actuated by water pressure at the forward section of theV supply water line 2, 'and then through a check valve 93 to the air motor of the modulating air valve I4. Control line D delivers control air at about the full 30 pounds pressure to the air motor in parallel with the control air delivered from the line I3. A check valve 94 is arranged in the line I3, beyond the line B connection, to prevent a bleeding of control air from line D into lines A and B when the air cartridge 4 is in closed condition. As shown in Fig. 6, the air cartridge 92 is biased towards closed position by a lever 95 and adjustable spring 96, and is actuated to open position by a diaphragm 9'! when the water pressure in a tting on the Water line 2 rises above about 17 pounds per square inch, i. e. a pressure somewhat above that at which the check valve 4'! in the water waste line of the modulating water valve 20 (see Fig. 2) closes to trap water in the supply line to the atomizers. 'I'he air cartridge 92 therefore remains open to deliver control air to the modulating air valve I4 to maintain air flow to the atomizers 3' until the water pressure at the atomizers 3' drops to a, preselected value.

The atomizers 3' include mechanism for sealing oit the water delivery" passage when the water inlet pressure drops below a preselected value, for example 20 pounds per square inch, Ywhich isscmewhat greater than the critical operating pressures of the waste check valve 4'! and of the diaphragm 9'! of the air cartridge 92. An appropriate construction for the atomizers 3' of a humidier system is illustrated in Figs. 7 and 8.

The body I 00 of the atomizer has inlets |0I, |132 for connection to the air line I and water line 2, respectively. A passage I03 'extends through the body |00 to connect the air inlet IEJI to a mixing chamber I 04 between the end of the body |00 and a cap |05 that is threaded upon the atomizer body and has a centrally arranged outlet |06 for the discharge of air and atomized water. A water passage I0'I extends from the water inlet |02 to a water chamber having a rear wall formed by a diaphragm |08 that is clamped to the atomizer body by a rear cap kIll!) and carries va iluted or hexagonally shapedplunger H0 that terminates, at its forward end, in a cleaning pin III thatY extends through the water outlet and into'the discharge opening 05 when the diaphragm |08 and plunger H0 are moved forwardly by a spring H2. A gasket II3 on the forward face of the plunger IIO cooperates with an annular rib YI I4 on the body |00 to form a valve that prevents the now of water from the atomizer when the plunger is forced into forward position by the spring I I2 when the inlet water pressure falls below about 20 pounds per square inch. Y

- As described above, air is admitted to the forwardsection of the supply air line I by air valve the humidostatV 5 closes the air cartridge II` and the water valve 20 closes at once -but the pres- 9 sure water in line 2 continues to be atomized by the atomizers 3 until the pressure drops to pounds per square inch. The valve II3, lill then closes and water Wastes from the line 2 through check valve 41 until the pressure drops to or somewhat below 17 pounds per square inch. The air supply to the atomizers is cut oi by valve I4 when the water pressure drops to about 17 pounds and permits closure of air cartridge 92 in line D by the spring 96.

It is to be noted that the air valve I4 and Water valve 20' of the Fig. 5 system are preferably of the modulating type, as described With reference to the Fig. 1 embodiment of the invention, to maintain a desired pressure differential at the atomizers 3 in the event o! variation in the supply air pressure. Either, or both, of the iluid supply valves I4, 20' may be of the on-off type however when maximum eiliciency in operation is not an essential requirement.

It is to be understood that the invention is not limited to the particular embodiments herein illustrated and described, and that many variations that may occur to those familiar with the design and construction of atomizer systems fall within the spirit of my invention as set forth in the following claims.

I claim:

l. A fluid supply system comprising a gas sup ply line and a liquid supply line, a control valve in said gas supply line, means associated with said control valve for operating the same and regulating the flow of gas through said gas sup ply line independently of variations in pressure in the liquid supply line above a preselected value, valve means in the liquid supply line responsive to variations in the pressure of gas in the supply line to regulate the flow of liquid through the liquid supply line, and means responsive to pressure in said liquid supplyr line for closing said control valve on the gas supply line when said liquid pressure drops below said preselected value, said last named means comprising a motor for operating said control valve, and means responsive to the pressure of the liquid at the inletl side of said valve means for eil'ecting a valve closing operation of Said motor.

2. A fluid supply system comprising a gas supply line and a liquid supply line, a control valve in said gas supply line, means associated with said control valve for operating the same and regulating the flow of gas through said gas supply line independently of variations in pressure in the liquid supply line above a preselected value, valve means in the liquid supply line responsive to variations in the pressure of gas in the gas supply line to regulate the ilow of liquid through the liquid supply line, and means responsive to n pressure in said liquid supply line for closing said between the gas pressure and the liquid pressure 'at the delivery ends of their respective lines, in

combination with means for momentarily clos- Ving said modulating valve upon a reduction in gas pressure at the delivery end of the gas supply line and effecting a wasting of the liquid to reduce the liquid pressure at the delivery endof the liquid supply line.

3. A iluid supply system comprising a gas supply line and a liquid supply line, a control valve in said gas supply line, means associated with said control valve for operating the same and regulating the flow of gas through said gas supply line independently of variations in pressure in the liquid supply line above a preselected value, valve means in the liquid supply line responsive to variations in the pressure of gas in the gas supply line to regulate the ilow of liquid through the liquid supply line, said valve means being a modulating valve having a gas-pressure motor communicating with said gas supply line beyond the control valve thereof, and means responsive to pressure in said liquid supply line for closing said control valve on the gas supply line when said liquid pressure drops below said preselected value.

4. A fluid supply system comprising a gas supply line and a liquid supply line, a control valve in said gas supply line, means associated With said control valve for operating the same and regulating the ow of gas through said gas supply line independently kof variations in pressure in the liquid supply line above a preselected value, valve means in the liquid supply line responsive to variations in the pressure of gas in the gas supply line to regulate the ow of liquid through the liquid supply line, said valve means in the liquid supply line including a modulating valve, a gas-pressure motor for opening said modulating valve, a control pressure line connecting said motor to the gas supply line beyond the control valve thereof, and means including a diaphragm subjected to the pressure in the liquid supply line to said valve means for opposing the opening of said modulating valve, whereby variations in the pressure on the liquid supply line are automatically compensated at the delivery end thereof by movement of said modulating valve in response to varying pressure on said diaphragm, and means responsive to pressure in said liquid supply line for closing said control valve on the gas supply line when said liquid pressure drops below said preselected value.

AGNEW H. BAHNSON, Jn.

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

UNITED STATES PATENTS Number Name Date 591,576 Thompson et al. Oct. 12,1897 991,641 Plantinga May 9, 1911 1,292,898 Slater Jan. 28, 1919 1,294,373 Andrew Feb. 18, 1919 1,553,370 DArcy Sept. 1,5, 1925 1,879,940 Mangiameli Sept. 27, 1932 2,001,318 Spence May 14, 1935 2,990,469 Chorley et al. 1..-- Aug. 17, 1937 2,119,084 McQuiston May 31, 1938 2,244,686 Garrison et al. June 10, 1941 2,266,354 Christenson et al. Dec. 16, 1941 2,379,633 Garretson July 3, 1945 FOREIGN PATENTS Number Country Date 191,775 Great Britain Jan. 23, 1923