US3699990A - Fluid mixer - Google Patents

Abstract

Mixing of two or more gases is accomplished by controlling the switching frequency of fluid amplifiers metering the different gases by fluid timing devices. The percentage of gases may be changed by adjusting a single variable restrictor which changes the area and hence the flow into the fluid timing device.

Description

I United States Patent 1151 Ziermann 1 Oct. 24, 1972 FLUID MIXER 3,429,324 2/1969 Brown et al. ..l37/8 l .5 3,348,562 10/1967 Ogren ..137/s1.5 [721 lnvenm" "F cheshlre 3,357,233 12/1967 Roof ..l37/8l.5 x Conn- 3,598,116 8/1971 Peters et a1. ..l37/81.5 X

[7 3] As'signee: General Medical'Corporation [221 Filed: April 1, 1971 Primary Examiner-William R. c1166 [21] Appl No 130 Attorney-Munson H. Lane Related US. Application Data i [63] Continuation-impart of Ser; N0. 8,569,.Feb. 4, [57] ABSTRACT 1970, Pat. No. 3,626,963. Mixing of two or more gases is accomplished by controlling the switching frequency of fluid amplifiers me- 52 us. 01 .1 ..137/81.5 wring the different gases y fluid timing devices- The 51] 1111. C1. ..F15c'l/12 Percentage of gases may b Changed by adjusting a [58] Field of Search 137/81 5 single variable restrictor which changes the area and hence the fl gtg g igflm device.

[56] References Cited UNITED STATES PATENTS 5 Cl i 4 Drawing Figures 3,327,726 6/1967 Hatch, Jr. ..l37/8l.5 z ffli QXXZJf/l/ PATENTEDHBI 24 I972 SHEET 1 OF 4 mx Q PATENTED 0m 24 m2 SHEET 2 0F 4 PATENTEU B I972 3.699990 SHEET u 0F 4 MSQ l FLUID MIXER CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application Ser. No. 8,569 filed Feb. 4, 1970 now U.S. Pat. No. 3,626,963, granted Dec. 14, 1971 and assigned to the same assignee.

BACKGROUND OF THE INVENTION Typically the method of obtaining a mixture of two or more gases is by the utilization of flow meters which measure each gas and are regulated to give the ratio desired. The flow meter when used in its customary fashion serves to measure the quantity of flow and the valve is either manually or automatically regulated to give the desired amount necessary to fulfill the percentage desired of the mixture-Of the types that are known, the valve, actuator and sensing mechanisms employ movable parts and are characterized as being complicated particularly where exact amounts are required as, for example, in clinical uses where respiration therapy, anesthetize therapy and the like are required.

I have found that I can obviate the problems of complexity and high costs and provide an accurate and reliable gas mixing device which minimizes the number of movable parts, eliminates any electrical parts or spark creating components which are important in certain hospital applications. This invention employs a fluidic logic circuitry which is capable of high speed operation and can switch from one gas to another in frequencies of 30 milliseconds which provide good homogenous gas mixtures. Additionally, the mechanism of the invention lends itself to being added on to in a building block fashion so as to accommodate the mixing of more than two gases while also affording the advantage of adjusting each gas independently to obtain the desired percentage. Additionally, I have found that by modifying the pneumatic circuit, the percentage of gases may be varied by adjusting a single variable restriction.

SUMMARY OF INVENTION A primary object of the invention is to provide a high speed gas mixer which employs a minimum number of movable parts.

In accordance with this invention, fluidic logic driving timing mechanism for effectuating a predetermined pulse frequency serves to mix two or more gases which mechanism is characterized as being simple to construct, relatively economical to manufacture, and highly reliable and accurate.

An additional feature of this invention is the provision of a tuning circuit upstream of one of the fluidic valves that permits adjusting of the percentage of gases by the use of a single valve adjustment.

Other features and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration, partly in section, of the invention;

FIG. 2 is a schematic illustration showing another embodiment of this invention,

FIG. 3 is a schematic illustration showing still another embodiment of this invention, and

FIG. 4 is a schematic illustration showing a modified version of the device illustrated in FIG. 3 which permits adjustment of the percentage of gases by a single adjustment.

DESCRIPTION OF THE PREFERRED EMBODIMENT As applied herein it is to be understood that the term fluidic logicrefers to fluidic devices that are utilized to respond to various signals and give commands to an output device. Fluidic devices are well known in the art and their operations and functions have been written about in great detail. It is, therefore, unnecessary for the purpose of this application to explain in detail its operation. Sufiice it to say that the fluidic device consists of a power stream which is directed to flow through either one or two output channels; Control ports located near the splitter section of the fluidic device serve to switch the power stream from one channel to the other. Obviously, no moving parts are necessary to cause the stream to switch from one to the other channel.

Now referring to FIG. 1, which shows the gas mixing apparatus as comprising the fluidic logic circuitry, generally illustrated by numeral 10, which includes a pair of fluidic valves 12 and 14. A suitable fluidic amplifier valve may be obtained from Northeast Fluidics, Inc., Bethany, Connecticut, Model 2010 modified with the exhaust port closed. Compressed air taken from a supply source 16 is admitted to the power nozzle 18 via line 20 of the fluid amplifier valve 14.

Normally the power stream in fluid amplifier 14 is directed to channel 22 until the switching mechanism, to be described hereinbelow, switches the power stream to output channel 24 where it is directed to the mixing chamber 26 via line 28. Similarly, oxygen from the oxygen supply 30 is admitted to the power nozzle 32 via line 34 and is normally directed to the output channel 36 until a signal for switching it into output channel 38 causes it to enter the mixing chamber 26 via line 40, it being noted that flow through channels 22 and 36 are in the order of 0.05 cfm (cubic feet per minute) which is substantially negligible. The purpose of the fluidic logic mechanism 10 is to time the particular pulsation between the oxygen and the air in order to achieve the desired mixture of oxygen and air. This is accomplished by controlling the flip-flop type of fluid amplifier 44 to switch by the cooperating timing mechanisms 46 and 48. As can be seen in FIG. 1, compressed air is admitted to the power nozzle 48 of the flip-flop fluid amplifier 44 via the branch line 50. It may be desirable to include an air filter 52 disposed in line 50 for filtering out any of the foreign matter contained in the air and a pressure regulator 54 also disposed in line 50 may be utilized to keep the pressure admitted to the power jet 48 at a constant value. The particular pressure levels are design considerations and not considered to be a part of the invention. Fluid amplifier 44 is switched in accordance with the timing mechanisms 46 and 48. Both timing mechanisms are similarly constructed and for the sake of convenience and simplicity like numerals will be used for like parts. Referring to timing mechanism 46 comprised of container 56 having a dividing wall 58 separates it into two separate compartments 60 and 62. Each compartment includes a diaphragm 64 and 66 separating the compartments into separate subcompartments 70 and'72 and 80 and 82. As can be seen from FIG. 1, flow from the output channel 86 of fluid amplifier 44 is admitted into chamber 70 via line 88 and branch line 90 and subcompartment 80 communicates with branch line 90 via branch line 92. The flow admitted to subcompartment 80 is restricted by the variable restrictor 94. Thus concomitantly while chamber 70 is being filled, chamber 62 is being filled at a slower rate. Obviously, once chamber 70 is filled, diaphragm 66 will be urged against the opening 98 formed in wall 58. Once this chamber is completely filled, subchamber 80 will then completely fill urging diaphragm 64 against the orifice 100. This signals the fluid amplifier by line 102 and control port 104 to switch to output channel 106. Output channel 106 communicating with control port 108 via line 110 causes the fluid amplifier 12 to switch to output channel 38 and causing oxygen to flow into mixture chamber 26. Simultaneously, timer mechanism 48 is actuated by bleeding air from line 1 into subchamber 70 via line 112 which causes timing mechanism 48 to signal fluid amplifier 44 when a predetermined time has been reached. The time is selected by adjusting either orifice 94 or 94'. -The rate at which the timers can cause the fluidic flip-flop amplifier 44 to switch will determine the ratio of gases fed into the mixing chamber 26. In laboratory tests the high speed gas mixer has been utilized at mixing speeds up to 30 millisecond intervals which speed has been found to provide a good homogenous mixture.

FIG. 2 is another representation of a gas mixing system but is a simplified version by utilizing an accumulator or the mechanical equivalent of an electrical capacitor. In this instance the accumulator is a container 220 having a fixed volume that receives a predescribed amount of fluid before it is discharged therefrom. In this embodiment air is controlled by normally closed fluid amplifier valve 200 and oxygen is controlled by normally closed amplifier valve 202. The switching of these amplifiers is controlled by the flipflop amplifier generally indicated at 204. The timing mechanism in this embodiment includes a first timing device generally indicated by 206 and second timing mechanism generally indicated by 208 each of which controls the switching of fluid amplifier 210. The operation of this high speed gas mixer is such that high pressure air is admitted to the power nozzle 212 where it either flows into output channel 214 or 216 where it is then admitted into the container 220 by way of a variable restriction 222 disposed in line 224. When container 220 is filled and the rate of its filling is controlled by adjusting the variable restrictor 222, it will admit a signal to control port 226 for causing the fluid amplifier 210 to switch from output channel 214 to output channel 216. This immediately deactivates timer 206 and activates timer 208 which respond in identical fashion. When timer 208 is actuated, the signal is admitted to control port 228 via branch line 230 for causing the fluid from power stream 232 to switch from channel 234 into channel 236 where it is admitted to control port 238 of fluid amplifier 200 causing it to open or divert the flow from the power stream 240 into channel 242 where it is admitted to the mixing chamber 244 via line 246. Similarly, when timer 206 is actuated, the fluid amplifier 204 is caused to switch such that chamber 234 is now in communication with the power stream 232, it being noted that fluid am plifier 204 is switched when flow in line 224 is evidenced via line 248 which is in communication with control port 250. Switching of fluid amplifier 202 causes oxygen to switch into output channel 252 and is admitted into mixing chamber 244 via line 254. The mixed gases can then be utilized in any manner that is desired as, for example, it may be used to fulfill the requirements of the respirator 256 shown in blank which respirator may be of the type disclosed and claimed in patent application SerQNo. 834,004 filed by Joseph C. Peters and Hermann Ziermann on June 17, 1969, and assigned to the same assignee.

In the embodiment shown in FIG. 3, the mixing system is substantially identical to the one shown in FIG. 1 except the flip-flop fluid amplifier responds to back pressure switches which are in the nature of fluid amplifiers and are shown as back pressure switches 300 and 302. Thus, fluidic amplifier valves 304 and 306 are turned on and off by actuating channels 308 and 310 of flip-flop fluid amplifier 312 respectively. These channels are actuated by turning on the control ports 314 and 316 by the timing mechanism generally illustrated by numerals 318 and 320. Thus, back pressure switch 300 responds to the timer 322 sensing the flow through output channel 308 which is being conducted through line 324. This pressure is sensed similarly to the pressure sensed by the container 56 shown in FIG. 1. When diaphragm 330 closes off the orifice 332, flow passing through restrictor 334 in passage 336 serves to switch the fluid from the power nozzle 338 from channel 340 into channel 342 which is, in turn, connected to control port 314 via line 344 for switching the power stream 346 from channel 308 to channel 310 for actuating fluid amplifier 306. This serves to switch the air to the channel communicating with the mixing chamber 350. Similarly, oxygen switch 304 will respond to the switching timing mechanism 320 and the back pressure switch 302. The rate at which the timing mechanisms perform the switching is controlled by varying the size of the orifice of variable restrictor 352 or 354.

Referring now to FIG. 4, the mixing system is substantially identical to the one shown in FIG. 3 except that the line inter-connectingthe control port of fluid valve 306 has been modified to include a tuning circuit including fixed restriction 400 in parallel leg 402 and variable restriction 404 disposed in line 406. All like component parts have like reference numerals but the components in FIG. 4 are identified with a prime designation. Thus, fluidic amplifier valves 304' and 306 are turned on and off by actuating channels 308' and 310' of flip-flop fluid amplifier 312' respectively. These channels are actuated by turning on the control ports 314 and 316 by the timing mechanism generally illustrated by numerals 318 and 320'. Thus, back pressure switch 300' responds to the timer 322' sensing the flow through output channel 308 which is being conducted through line 324'. This pressure is sensed similarly to the pressure sensed by the container 56' shown in FIG. 1. When diaphragm 330' closes off the orifice 332', flow passing through restrictor 334 in passage 336' serves to switch the fluid from the power nozzle 338' from channel 340' into channel 342' which is, in turn, connected to control port 314' via line 344' for switching the power stream 346' from channel 308' to channel 310' for actuating fluid amplifier 306. This serves to switch the air to the channel communicating with the mixing chamber 350'. Similarly, oxygen fluid valve 304 will respond to the switching timing mechanism 320' and the back pressure switch 302'. The rate at which the timing mechanisms perform the switching is controlled by varying the size of the orifice of variable restrictor 352' or 354'.

According to this invention, the rate at which the timing mechanism performs the switching may be accomplished by varying a single orifice. This is accomplished by variable flow restriction 404 and fixed restriction 400 in bleed line 402. Preferably, I have found that the bleed orifice should be so restricted as to limit bleed flow and a suitable size is 0.046 inch diameter. The bleed line may be so sized or a larger line with a fixed restriction may be utilized.

In this embodiment the restrictor 352 of FIG. 3 is eliminated and adjustment is made solely by adjustment 354' remotely accessible. Thus in operation when it is desired to obtain 100 percent oxygen (0 restrictor 354 is closed rendering back pressure switch 302' from switching'and output channel 310' of flip-flop fluid amplifier 312 will be locked-in, thus holding fluid amplifier valve 306' in the opened position. Hence, fluid amplifier valve 304 is rendered inoperative.

When it is desired to close off the fluid amplifier valve 306, thus supplying 100 percent air (79 percent air constituents less 0 plus 21 percent 0 the restrictor 354 is in the full open position. The frequency of fluid amplifier 312' (that is the frequency of switching between 308 and 310') is at a predetermined high rate such that the time delay across restrictor 404 and bleed 400 is such that fluid amplifier valve 306 will never see a signal to turn it on. In this condition fluid amplifier valve 304' will remain on the on position since the frequency will never produce a sustained signal to cause fluid amplifier valve 304' to close. It being noted that restrictor 404 is adjustable to tune it in with the switching frequency of fluid amplifier 312.

As will be obvious to one skilled in the art, the combined variable restrictor 404 and bleed 400 may be used on the other circuit, i.e., in line 324' upstream of fluid amplifier valve 304' so that the control is on the air line which I have found gives a greater degree of accuracy on the low end (i.e., 21% 0 of the scale rather than on the high end (100% 0 as is the case shown in FIG. 4.

Thus, according to this invention, switching of two or more gases may be effectuated by utilizing fluid amplifiers for switching the gases at a predetermined time interval. The timer being adjustable to determine the time intervals of each of the gases in order to obtain a predetermined gas mixture. Obviously, a minimum numberof moving parts are required since the fluid amplifiers are switchable without the need of moving parts. Except for the means for adjusting the restrictions, and the fluid, the only moving parts required obviously are the diaphragms in the switching containers of FIGS. 1, 3 and 4 and the mechanism in the fluid valves. Thus, what has been shown by this invention is a simple device for mixing two or more gases by controllin the frequency of switching from one gas to the other y preset timing mechanisms. The percentage of gases may be controlled by a single adjustment. Such a device is characterized as being simple to construct and relatively inexpensive to fabricate.

It should be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the spirit or scope of this novel concept as defined by the following claims.

I claim:

1. Apparatus for mixing at least two gases comprising in combination,

a mixing chamber,

separate sources for each of said gase connecting means interconnecting said separate sources and said mixing chamber,

first and second fluidic valves disposed in said connection means for connecting and disconnecting each of said sources with said mixing chamber,

a fluidic logic circuit including a fluid amplifier and fluidic timers for controlling said first and second fluidic valves,

said fluid amplifier responding to said fluidic timers and having one of its output channels connected to said first fluidic valve and the other of its output channels connected to said second fluidic valve,

means including a tuning circuit and a single manual adjustment operatively connected to one of said fluid timers for adjusting the percentage of each of said gases relative to each other, and

said tuning circuit including restriction means disposed between the output channel of said fluid amplifier and said first fluidic valve and a bleed between said restriction means and said first fluidic valve,

said bleed being dimensioned so that the diameter of the opening is substantially 0.046 inches.

2. Apparatus as claimed in claim 1 wherein said fluid 3. Apparatus as claimed in claim 1 including a fluidic back pressure switch having an output channel connected to said fluid amplifier and a control port connected to said fluid timer.

4. Apparatus as claimed in claim 1 wherein said single manual adjustment is a variable area orifice for varying the flow into one of said fluidic timers.

5. Apparatus as claimed in claim 1 including a corresponding number of fluidic timers for the number of gases being mixed wherein each of said fluidic timers includes a canister divided into a pair of subchambers, diaphragms in said subchambers each of which are actuated to close off a cooperating opening when the appropriate subchamber is filled with gas, an unrestricted connection leading gas into one of said subchambers, at least one of said fluidic timers has a variable restricted connection leading gas into the other of said subchambers, and said manual adjustment adjusting said variable restriction.

Claims (5)

1. Apparatus for mixing at least two gases comprising in combination, a mixing chamber, separate sources for each of said gases, connecting means interconnecting said separate sources and said mixing chamber, first and second fluidic valves disposed in said connection means for connecting and disconnecting each of said sources with said mixing chamber, a fluidic logic circuit including a fluid amplifier and fluidic timers for controlling said first and second fluidic valves, said fluid amplifier responding to said fluidic timers and having one of its output channels connected to said first fluidic valve and the other of its output channels connected to said second fluidic valve, means including a tuning circuit and a single manual adjustment operatively connected to one of said fluid timers for adjusting the percentage of each of said gases relative to each other, and said tuning circuit including restriction means disposed between the output channel of said fluid amplifier and said first fluidic valve and a bleed between said restriction means and said first fluidic valve, said bleed being dimensioned so that the diameter of the opening is substantially 0.046 inches.

2. Apparatus as claimed in claim 1 wherein said fluid amplifier is of the flip-flop type.

3. Apparatus as claimed in claim 1 including a fluidic back pressure switch having an output channel connected to said fluid amplifier and a control port connected to said fluid timer.

4. Apparatus as claimEd in claim 1 wherein said single manual adjustment is a variable area orifice for varying the flow into one of said fluidic timers.

5. Apparatus as claimed in claim 1 including a corresponding number of fluidic timers for the number of gases being mixed wherein each of said fluidic timers includes a canister divided into a pair of subchambers, diaphragms in said subchambers each of which are actuated to close off a cooperating opening when the appropriate subchamber is filled with gas, an unrestricted connection leading gas into one of said subchambers, at least one of said fluidic timers has a variable restricted connection leading gas into the other of said subchambers, and said manual adjustment adjusting said variable restriction.

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