Fluid metering and mixing device having inlet and outlet valves

A metering device for delivering a fluid at a predetermined rate and a mixing device for delivering first and second fluids at a predetermined rate mixed in a predetermined ratio. The devices include a flexible fluid bladder having flexible inlet and outlet conduits, a flexible inlet conduit clamp tube overlying the inlet conduit, and a flexible outlet conduit clamp tube overlying the outlet conduit, all of which are positioned between a pair of abutting rigid plates having matching voids. As each of the clamp tubes are pressurized, the inlet or outlet conduits over which they lie are collapsed to prevent fluid flow therethrough. A valve system is provided for alternating between a fill cycle wherein the outlet conduit clamp tube is pressurized and the inlet conduit clamp tube is depressurized to allow fluid to flow into the fluid bladder, and a discharge cycle wherein the inlet conduit clamp tube is pressurized and the outlet conduit clamp tube is depressurized to allow fluid to flow from the fluid bladder. The rate at which the metering device delivers fluid is thus proportional to the product of the fluid bladder volume and the operating frequency of the valve system. A mixing device may be implemented by providing a second fluid bladder which is alternately filled and discharged into the outlet conduit of the first fluid bladder so that the fluids are mixed at a ratio corresponding to the volume of the first bladder to the volume of the second bladder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to fluid handling devices and, more particularly, to 
devices for delivering fluid at a controlled rate and for mixing fluids in 
a controlled ratio. 
2. Description of the Prior Art 
In many fields it is necessary to deliver a single fluid at a precisely 
controlled rate or to deliver a predetermined mixture of fluid at a 
controlled rate. Pumps presently in use for these purposes are relatively 
expensive and somewhat complex. A more important disadvantage of 
conventional pumps when used in certain fields, such as the medical field, 
is the difficulty of sterilizing or cleaning such pumps. For example, in 
the field of dialysis treatment for kidney disease, a concentrated 
dialysate solution is mixed with water and dextrose before being directed 
to other dialysis equipment. It is extremely important that such equipment 
be sterile since the mixed dialysate can carry germs and infections to the 
patient, particularly during a peritoneal dialysis treatment. The medical 
field has generally solved the sterilization problem to a large extent by 
utilizing disposable, presterilized devices. However, it has not been 
possible to solve the sterilization problem of conventional dialysis pumps 
in this manner because their relatively high expense makes disposal after 
each use financially impractical. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a relatively simple and 
inexpensive metering device capable of delivering a fluid at an accurately 
controlled rate. 
It is another object of the invention to provide a relatively simple and 
inexpensive mixing device capable of delivering different fluids at a 
precisely controlled rate and mixing ratio. 
It is still another object of the invention to provide a disposable 
metering and mixing device in which all fluid contacting portions are 
easily and inexpensively replaced. 
It is a still further object of the invention to provide a mixing device 
which is easily adapted to mix a large number of fluids in any proportion. 
These and other objects of the invention are provided by alternately 
filling and emptying a fluid chamber having a precisely controlled volume 
at a preset rate. The metering device utilizes a single fluid chamber so 
that the rate at which the fluid is delivered is proportional to the 
product of the volume of the chamber and the rate at which the chamber is 
filled and emptied. The metering device utilizes a plurality of fluid 
chambers emptying into a common discharge conduit so that the mixing ratio 
of the fluids correspond to the volume ratio of the respective fluid 
chambers receiving the fluids, and the mixed fluid is delivered at a rate 
proportional to the product of the sum of the volumes of the fluid 
chambers and the rate at which the chambers are filled and emptied. The 
flow of fluid into the chambers may be controlled by a unique valve system 
in which the inlet conduits and outlet conduits leading to and from the 
fluid chambers are flexible. Flexible clamp tubes overlay the inlet and 
outlet conduits between a pair of rigid plates so that pressurization of 
the clamp lines pinches off the adjacent inlet or outlet conduits. By 
alternately pressurizing and depressurizing the inlet conduit clamp tube 
and the outlet conduit clamp tube, the fluid chambers are alternately 
filled and emptied. The fluid chambers, inlet and outlet conduits, and 
clamp tubes may all be formed by flexible sheets bonded together. The 
sheets may be positioned between a pair of abutting plates having voids 
which mate with the fluid chambers and conduits formed in the sheets so 
that the fluid contacting portions of the metering and mixing device may 
be easily and inexpensively replaced by separating the plates and 
discarding the flexible sheets. A mixing device for precisely mixing any 
number of fluids in any proportion may be easily implemented by simply 
providing additional fluid chambers having a controlled volume.

DETAILED DESCRIPTION OF THE INVENTION 
A mixing device for mixing three different fluids at a controlled rate and 
in a predetermined ratio is illustrated in FIGS. 1 and 2. The device 
includes a fluid bag 10, a control bag 12 and a pair of plates 14, 16. The 
fluid bag 10 is preferably formed by bonding together two sheets of 
inexpensive flexible material, such as vinyl, at appropriate places to 
produce conduits and chambers so that the bag 10 may be inexpensively 
disposed of after each use. Where three different fluids are to be mixed, 
the fluid bag 10 will include a first fluid chamber 18, a second fluid 
chamber 20 and a third fluid chamber 22. The volume of each chamber 18-22 
is proportional to the desired mixing ratio of the fluid received by the 
chamber. Inlet conduits 24, 26, 28 are connected to the tops of the fluid 
chambers 18, 20, 22, respectively, each of which have their upper ends 
connected to their respective fluid supplies. Similarly, the bottom 
portions of each fluid chamber 18, 20, 22 empty into outlet conduits 30, 
32, 34, respectively. The outlet conduits 30-34 eventually empty into a 
common discharge conduit 36, but in certain fields it may be desirable to 
mix the fluids from two of the chambers 18, 20 before being mixed with the 
fluid from the third chamber 22. For example, in the field of dialysis a 
dialysate concentrate is diluted with water before being mixed with 
dextrose to form the final dialysate mixture. For the fluid bag 10 of FIG. 
1 the dialysate concentrate is received in chamber 18 and water is 
received in chamber 20. The water and concentrate flow through outlet 
conduits 32, 30 and are combined in a mixing chamber 38 before being mixed 
with the dextrose flowing from chamber 22 through outlet conduit 34. The 
final dialysate mixture then flows from the discharge conduit 36. The 
mixing chamber 38 is provided with a pair of spaced apart electrodes 40 
for measuring the resistivity of the diluted dialysate in order to insure 
the correct mixing concentration. 
In order to accurately mix the fluids, the outlet conduits 30-34 are 
clamped and the inlet conduits 24-28 are unclamped as explained 
hereinafter thereby allowing the respective fluids to fill the fluid 
chambers 18-22. During the discharge cycle, the inlet conduits 24-28 are 
clamped and the outlet conduits 30-34 are unclamped thereby allowing fluid 
to drain from the chambers 18-22 where the fluids are mixed in the mixing 
chamber 38 and discharge conduit 36 in the proportions determined by the 
volume of each fluid chamber 18-22. 
Although other devices may be used for blocking the inlet conduits 24-28 
and outlet conduits 30-34 including electromechanical devices, a control 
bag 12 may be advantageously used for this purpose. The control bag 12, 
like the fluid bag 10, is preferably formed by bonding together a pair of 
flexible sheets at appropriate places in order to form chambers and 
conduits. The control bag 12 includes an inlet conduit clamp tube 42, an 
outlet conduit clamp 44 and three interconnected discharge chambers 46, 
48, 50. As best seen in FIG. 2, the inlet conduit clamp tube 42 overlies 
all of the inlet conduits 24-28 directly above their respective fluid 
chambers 18, 20, 22. Similarly, the outlet conduit clamp tube 44 overlies 
all of the outlet conduits 30-34 directly beneath their respective fluid 
chambers 18, 20, 22. The discharge chambers 46, 48, 50 are similarly 
shaped and overlie the fluid chambers 18, 20, 22, respectively. The fluid 
bag 10 and control bag 12 are sandwiched between the rigid plates 14, 16, 
each of which have voids on their opposed surfaces which match the 
conduits and chambers in the fluid bag 10 and control bag 12. The plates 
14, 16 abut each other with the bags 10, 12 therebetween and the chambers 
and conduits in the bags 10, 12 received by the voids in the plates 14, 
16. The clamp tubes 42, 44 are alternately supplied with fluid at a higher 
pressure than the fluid in any of the conduits 24-28, 30-34. Since the 
fluids in the clamp tubes 42, 44 are at a substantially higher pressure 
than the pressure in the inlet conduits 24-28 or outlet conduits 30-34 and 
the spacing between the rigid plates 14, 16 within the voids is no more 
than the width of the clamp tubes 42, 44, the inlet conduits 24-28 are 
pinched off by the inlet conduit clamp tube 42 when the inlet conduit 
clamp tube is pressurized during the discharge cycle, and the outlet 
conduits 30-34 are pinched off by the outlet conduit clamp tube 44 when 
the outlet conduit clamp tube is pressurized during the fill cycle. During 
the discharge cycle the discharge chambers 46-50 are also pressurized 
thereby forcibly ejecting the respective fluids from the fluid chambers 
18-22. 
Although a mixing device having flexible fluid chambers and flexible 
conduits are illustrated in FIGS. 1 and 2, it is to be understood that 
rigid fluid chambers having inlet and outlet conduits which are 
alternately opened and closed may also be used. Similarly, rigid fluid 
chambers having flexible inlet and outlet conduits may be used, with the 
conduits being pinched off by either clamp tubes or by another means such 
as an electromechanical device. 
The operation of the fluid mixing device can best be explained with 
reference to the schematic of FIG. 3. The clamp tubes 42, 44 and discharge 
chambers 46-50 are connected to a high pressure fluid source 52 through 
selectively actuated valves 54, 56, 58, respectively, and they are 
connected to a fluid return through bleeder valves 60, 62, 64, 
respectively. During the fill cycle valve 56 is opened thereby allowing 
the high pressure fluid in the outlet conduit clamp tube 44 to pinch off 
the outlet conduits 30-34. At the same time, the valves 54, 58 are closed 
allowing a pressure reduction in the inlet conduit clamp tube 42 through 
valve 60 and the discharge chamber tube 47 through valve 64. The 
respective fluids then flow into the fluid chambers 18, 20, 22 through 
inlet conduits 24, 26, 28, respectively, until all of the chambers are 
filled at the conclusion of the fill cycle. During the discharge cycle 
valve 54 is opened thereby allowing the high pressure fluid at 52 to flow 
into the inlet conduit clamp tube 42 and pinch off the inlet conduits 
24-28. At the same time valve 56 is closed allowing a pressure reduction 
in the outlet conduit clamp tube 44 through valve 62 to open the outlet 
conduits 30-34 and allow fluid to drain from the fluid chambers 18-22. In 
order to maximize the speed at which the mixing device may operate, 
discharge chambers 46-50 may be used to forcible eject the fluid from the 
chambers 18-22. The discharge chambers 46-50 are also pressurized during 
the discharge cycle by opening valve 58 to connect the discharge chamber 
tube 47 to the high pressure source 52. Fluid flows from chambers 18, 20 
through outlet conduits 30, 32, respectively, where they are combined 
combined in mixing chamber 38. The resistivity electrodes 40 monitor the 
resistivity, and hence concentration, of conductive fluids to insure 
correct mixing proportions. The fluid in the mixing chamber 38 is then 
combined with the fluid from chamber 22 flowing through outlet conduit 34, 
and the final mixture then flows from the discharge conduit 36. It is thus 
apparent that for each fill and discharge cycle, fluids occupying the 
volume of the respective fluid chambers 18-22 are combined at the 
discharge outlet 36. Thus, the mixing proportions of the fluids in the 
chambers 18-22 are equal to the proportion of the volume of the respective 
chambers to the sum of the volumes of the chambers 18-22. Similarly, the 
rate at which fluid is discharged from the discharge outlet 36 is equal to 
the product of the sum of the volumes of the chambers 18-22 and the 
frequency at which the fill and discharge cycles occur. 
The volume of each fluid chamber 18-22 is generally determined by the 
volume of the matching voids in the plates 14, 16. Thus the volume of the 
chamber, and hence the mixing proportion of the fluid received by the 
chamber, may be adjusted by adjusting the size of the void which receives 
the fluid chamber. One embodiment of a device for performing this function 
is illustrated in FIG. 4. The plate 14 contains an aperture 60 which 
receives a cup-shaped member 62 having an outwardly dished surface for 
contacting the fluid chamber 18. The cup-shaped member 62 is threaded onto 
the end of a shaft 64 which is rotatably mounted on a bracket 66 secured 
to the outer face of the plate 14 by screws 68. A knob 70 is secured to 
the outer end of the shaft 64. The cup-shaped member 62 is moved toward 
and away from the fluid chamber 18 thereby decreasing and increasing its 
volume by rotating the knob 70. 
As mentioned previously, the rate at which the fluid is discharged from the 
mixing device is proportional to the product of the sum of the volumes of 
the mixing chambers and the rate at which the fluids in the chambers are 
discharged. Thus a mixing device having two or more fluid chambers also 
serves as a metering device for discharging fluid at a predetermined rate. 
Where it is desired to merely discharge a single fluid at a predetermined 
rate, a single fluid chamber may be used. A metering device using this 
principle is illustrated in FIG. 5. The device includes a single fluid 
chamber 80 receiving fluid at its upper end through an inlet conduit 82 
and discharging fluid at its lower end through outlet conduit 84. A 
control bag placed adjacent the fluid bag includes an inlet conduit clamp 
tube 86, an outlet conduit clamp tube 88 and a discharge member 90 
selectively receiving pressurized fluid through a discharge chamber tube 
2. During the fill cycle the outlet conduit clamp tube 88 is pressurized 
and the inlet conduit clamp tube 86 and discharge chamber 90 are 
depressurized to allow fluid to flow into the fluid chamber 80 through 
inlet conduit 82. When the chamber 80 has been filled, fluid is discharged 
therefrom in a discharge cycle in which the inlet conduit clamp tube 86 is 
pressurized to prevent fluid flow into the fluid chamber 80, the outer 
conduit clamp tube 88 is depressurized to allow fluid to flow from the 
fluid chamber 80 through the outlet conduit 84, and the discharge chamber 
90 is pressurized through the discharge chamber tube 92 to forcibly eject 
fluid from the fluid chamber 80. The rate at which fluid is discharged 
through the outlet conduit 84 is proportional to the product of the volume 
of the fluid chamber 80 and the rate at which the fluid chamber 80 is 
filled and emptied. 
The flow of fluid from the mixing device illustrated in FIGS. 1-3 and the 
metering device illustrated in FIG. 5 is pulsating since fluid flows 
therefrom only during the discharge cycle. In order to achieve a smoother 
flow, a number of fluid chambers may be provided, and the operational 
sequence of each fluid chamber may be offset in phase so that as one fluid 
chamber is discharging fluid another fluid chamber is receiving fluid. One 
embodiment for performing this function is illustrated in FIG. 6. The 
device includes two fluid chambers 100, 102 each receiving fluid through 
respective inlet conduits 104, 106 and discharging fluid through outlet 
conduits 108, 110. The inlet conduits 104, 106 receive fluid from a common 
inlet tube 112, and the outlet conduits 108, 110 discharge fluid into a 
common outlet tube 114. During the fill cycle of fluid chamber 100 and the 
discharge of fluid from fluid chamber 102 clamp tube 116 is pressurized 
and clamp tube 118 is depressurized. Clamp tube 116 pinches off outlet 
conduit 108 and pressurizes a discharge chamber 120 thereby forcibly 
ejecting fluid from fluid chamber 102 through outlet conduit 110. At the 
same time, the inlet conduit 106 is pinched off by inlet clamp tube 122, 
and since tube 118 is depressurized, the discharge chamber 124 and the 
clamp tube 126 are depressurized thereby allowing fluid to flow into the 
fluid chamber 100 to inlet conduit 104. After fluid chamber 100 has been 
filled and fluid chamber 102 has been emptied, tube 118 is pressurized and 
tube 116 is depressurized thereby discharging fluid from fluid 100 and 
allowing fluid to flow into fluid chamber 102 in the same manner as 
previously stated. The resulting flow through the discharge conduit 114 is 
substantially more uniform than the single chamber variety of metering 
device.