LIQUID FLOW RATE CONTROL DEVICE

Abstract: A fluid flow rate control device comprises a first vented fluid chamber (60) having an upper fluid inlet end with a hollow spike (46). A free floating float valve (70) in the first chamber blocks the flow of fluid into the first chamber from a fluid container (12) providing a constant pressure head. A lower end of the chamber is connected, through a flow regulator (66), to an upper inlet end of a second, vented, drip chamber (62), the lower end of which is adapted for connection to a discharge tube. A second, free floating float valve (140) in the second chamber blocks the flow of fluid from the second chamber into the discharge tube when the fluid level in the second chamber is at or below a preestablished minimum level and blocks flow of fluid into the second chamber when the level in the second chamber reaches a preestablished level.

Description: LIQUID FLOW RATE CONTROL DEVICE BACKGROUND OF THE I ENTION. This application is a contιnuatιon-ιn-Dart applica¬ tion of U.S seri≤. No. 08/67^,552, filed July 1, 1996, which claims the nenefit of U.S provisional application serial No. 60/00463^, filed September 29, 1995 Field of the Invention: The present invention relates generally to apparatus for controlling rates of liαuiαs and, more particu¬ larly, to apparatus for maintaining accurate, precise and stable liquid flow rates in medical liquid αelivery sys- terns, such as intravenous (IV) fluid delivery systems. Background Discussion: Many applications exist in whicn the precisely- controlled flow of small quantities of liquid materials is essential. One particularly critical example of such applications is tne required "precise delivery of con¬ trolled amounts of intravenous (IV) liquids to patients in hospitals, clinics, or in the field. Gravity-driven IV liquid delivery systems or devices known to the present inventor utilize variable orifice flow control valves to control the flow rate of fluids to a patient undergoing treatment. Such known valves require a constant pressure drop, ΔP, across the orifice to maintain a stable, accurate and precise flow rate of fluid into patients to which the systems or devices are connected. Some of these known flow control systems or devices utilize one or more fixed orifices and adjust the pres¬ sure drop, ΔP, across the orifice (s) to set the fluid flow rate. This pressure drop (the absolute sum of the positive ana negative pressure) across tne orιfιce(s) calibrated for a liquid of known viscosity and density determines the instantaneous fluid flow rate througn the orifice (s) . Many known variable and fixeα orifice fluid flow control systems attempt to circumvent or accommodate the normal decrease in positive fluid nead pressure as the supply liquid level drops as, for example, liquid is drained from an IV bottle, and also variations in nega- tive or suction pressure in the patient delivery line, as may, for example, be caused by patient movement or changes in the patient's venous pressure. Variable orifice flow control valves of some known IV flow control devices are marked with flow rates that appear to assume an average pressure drop, ΔP, across the orifice, with no control of supply head pressure or pa¬ tient line suction. For example, the fluid flow control valves disclosed in U.S. Patent numbers 4,789,000; 4,802,506 and Λ, 807, 660 are considered representative of this type device. Instructions provided with commercial versions of the just-mentioned type or IV flow control devices caution users initially to count the number of liquid drops falling through an associated drip chamber in a prescribed period of time to establish an accurate flow rate, and thereafter to adjust the valve frequently to maintain a relatively constant liquid delivery rate as the supply liquid head and/or the patient line pressures changes . Other known IV flow rate control systems, such as those disclosed in U.S. patent numbers 3,929,157; 4,340,050 and 4,588,396, disclose or suggest controlling fluid head pressure by transferring liquid from a primary liquid supply source into a secondary vessel in which the level is held constant and independent of the decreasing head pressure of the primary liquid source as it empties. Other examples of known IV devices are disclosed in U.S. patent number 3,929,157. These particular patents disclose IV devices in which a tuoe connects a rigid sup¬ ply source to a secondary chamber for head pressure con- trol. Liquid flows under gravity from the supply source into the secondary chamber until the bottom of the tube is covered. At that point air can no longer pass up the tube to displace the in-flowing liquid and flow stops. The region above the liquid m the secondary chamber is connected to the atmosphere (that is, the region is at atmospheric pressure), so there is no coupling through the air between the supply head pressure and the head pressure in the chamber. The head pressure on a fixed outlet orifice located in the bottom of the secondary chamber determines the rate of flow, whicn may be adjusted by sliding the secon¬ dary chamber up or down on the tube from the supply source, thereoy adjusting the head pressure of the liquid in the secondary chamber. A liquid collection chamber be- low the orifice collects the liquid and a flexible tube conducts the liquid from the collection chamber to a pa¬ tient. This collection chamber is also vented to atmos¬ phere so that changes in the liquid height in the patient line or changes in venous back pressure are uncoupled from the orifice and will have no effect on the flow rate through the orifice. U.S. patent number 4,340,050 discloses the use of a collapsible bag for the supply source. The bag dis¬ charges liquid into a liquid-receiving chamber which is vented to the atmosphere. A float-type valve is piv¬ otally mounted in the liquid-receiving chamber for main¬ taining a constant liquid level. As disclosed, a second chamber, having fixed orifices at various heights and which is fluidly connected to the liquid-receiving cham- ber, can be moved up and down relative to the liquid- receiving chamber to vary the head pressure on the ori¬ fices. Liquid passing through the orifices collects in the bottom of the second chamber and is conducted to a patient through a flexible IV tube. This second chamber is vented to the atmosphere above the liquid on both sides of the orifices, thereby uncoupling the orifices from any pressure changes in the IV line connected to the patient . In another example of the known IV flow control art, U.S. patent number 4,588,396 discloses the use of a tube which connects a rigid supply source to a liquid- receiving chamber in which a constant liquid level is maintained in the manner disclosed in above-mentioned U.S. patent nu oer 3,929,157. The air above the liquid in the receiving chamber, which is the source of displace¬ ment air in the supply vessel, is vented to atmosphere through a metering valve which is used for flow rate con¬ trol, instead of an orifice being used in the IV liquid path. Liquid is disclosed as flowing out of this collec- tion chamber through a sealed drip chamber which is con¬ nected to a patient delivery line. It appears, however, that changes in the height of the liquid in the patient line will couple through the air in the sealed drip cham¬ ber to the liquid in the collection chamber and affect the flow rate through the system. Other known IV flow rate control systems, such as are disclosed in U.S. patent numbers 4,142,523; 4,186,740; 4,515,588 and 4,863,437, use a diaphragm or collapsible chamber which adjusts a flow control orifice or passage to minimize flow rate changes caused by supply head pressure and patient delivery line pressure varia¬ tions. As far as the present inventor is aware, however, none of such disclosed IV devices isolate the flow con¬ trol element from both the supply head and patient line pressure variations. By way of a still further example, U.S. patent num¬ ber 4,613,325 discloses an IV flow rate control system that amplifies and uses a velocity dependent pressure drop across a restriction in the flow path to modulate the size of an upstream variable orifice flow control. There does not, however, appear to be disclosed any means for isolating the flow restriction from supply head or patient line pressure variations. Further examples of known IV flow control devices are disclosed in U.S. patent numbers 5,014,750 and 5,033,714. These patents disclose a pressurized constant pressure liquid supply that is fed througn an adjustable flow restricter into a patient delivery line, the entire IV system being worn by the patient. However, since the system is tied to the patient, little variation would be expected in patient line pressure except tnat caused by venous blood pressure. Many of the known IV flow rate control devices that attempt to compensate for changes in supply head pressure and patient line pressure are expensive and complex, and the rar:ι_,e of pressure compensation oefore a nurse must reset the flow rate is considered oy the present inventor to be limited, particularly, since in a "worst case" situation a patient' s line suction on the flow control orifice can, depending, for example, on the patient's po¬ sition (e.g., standing, sitting or lying) increase by 30 to 40 cm of water, possibly doubling the pressure drop across the orifice. An important need, therefore, still exists in the meoical field for an improved, simple, reliable and rela¬ tively low-cost, gravity-driven IV system that delivers an accurate, precise and stable flow rate of medicinal liquid to patients, in bed or ambulatory, in hospital, home, field or transport settings. It is, therefore, a principle objective of the present invention to provide sucn an improved IV system. SUMMARY OF THE INVENTION: In accordance with the present invention, there is provided a gravity flow fluid flow regulating device with constant fluid head provision that is particularly for regulating the flow of fluids, such as IV fluids, from a fluid source into a patient's body. The flow regulating device comprises a first, constant fluid head chamber having an upper fluid inlet end region and a lower, fluid outlet region. Included is a second, drip, chamber hav¬ ing an upper fluic mlet end region and a lower, fluid outlet end region, the lower fluid outlet eno region be- ing configured for having attached thereto a fluid deliv¬ ery tube, such as a conventional IV fluid delivery tube for providing IV fluid into a patient's body. Further comprising the present invention are fluid flow regulating means connected in fluid flow relation- ship between the fluid outlet end region of the first chamber and the fluid inlet end region of the second chamber, the regulating means being configured for regu¬ lating the gravity flow of fluid from the first chamber into the second chamber. Further included are means enabling a fluid-flow connection between the fluid inlet end region of the first chamber and a lower, discharge region of a fluid source, such as a source of IV fluid that may be either open or closed to ambient pressure. Still further included in the present flow control device are first, upper, fluid level control means dis¬ posed in the first chamber for causing, when the connect¬ ing means connect the first chamber to a preexisting source of fluid for receiving a flow of fluid therefrom, a preestablished fluid level to be substantially main- tained in the first cna ber as tne fluid level in the source decreases . In accordance witn a preferred embodiment of the in¬ vention, the first, upper, fluid level control means m- elude an inlet orifice at the fluid inlet end region of the first chamber and a first, upper, float valve dis¬ posed in a free-floating relationship insiαe the first chamϋer. The first, upper, free-floating valve is configured for clocking the inlet orifice to stop the gravity flow of fluid through the orifice from a con¬ nected source of fluid when the fluid level in the first cnamber is at the preestablished level and for unblocking the inlet orifice to permit a gravity flow of fluid througn the orifice from the fluid source when the fluid level in tne first chamber falls below the preestablished level . Also included m the present flow control device are first venting means located at an upper region of the first chamber above the preestablished fluid level therein for venting the first chamber to ambient sur¬ rounding pressure and second venting means located at an upper region of the second chamber for venting the second chamber to ambient surrounding pressure. At least a side wall region of the second chamber is constructed of a transparent material so that a rate of fluid dripping through the second chamber can be observed by a user of the device. Further, according to a preferred embodiment, the fluid flow regulating means comprise a valve body having a rotatably-mounted valve stem for incremental rotational movement between a first, fully-closed position which blocks the gravity flow of fluid from the first chamber into the second chamber and a second, fully-open position in which the gravity flow of fluid from the first chamber into the second chamber is at a maximum flow. The valve stem is disposed in the valve body for being manually set at any selected rotational position between the first and second positions so as to thereby enable a user of the device to selectively control the gravity flow of fluid from the first chamber into the second chamber. An indicator dial calibrated with respect to rotational po¬ sitions of the valve stem may be provided for enabling a user to read fluid flow rates from the first chamber into the second chamber associated with different rotational positions of the valve stem. A second, lower, flow control means comprises a sec¬ ond, lower valve that is disposed in free-floating rela¬ tionship inside the second chamber for closing the lower, fluid outlet end region when fluid in the second chamber falls to a preestablished lower level to prevent the in¬ clusion of air from the outlet region of the second cham¬ ber, for example, into the fluid conduit to a patient's body and for alternatively closing the fluid inlet to the second chamber when the fluid in the second chamber rises to a preestablished upper level. In a first variation of the fluid flow control de¬ vice, the fluid flow regulating means of the flow con¬ trol device comprise a flexible fluid conduit connected in fluid flow relationship between the outlet end region of the first chamber and the fluid inlet end region of the second chamber. In such configuration, means are in¬ cluded for selectively controlling the vertical distance between the preestablished fluid level in the first cham¬ ber and the fluid inlet region of the second chamber. In a second variation gravity flow fluid flow device with constant fluid head provision, which functions in the same manner as the first variation device, a first, constant fluid head chamber having an upper fluid inlet end region and a lower, fluid outlet region; and a sec- ond, drip chamber having an upper fluid inlet end region and a lower, fluid outlet end region, the lower fluid outlet end region being configured for having attached thereto a conventional discharge tube, the second chamber being aligned with the first chamber along a common lon- gitudinal axis. Included are fluid flow regulating means for regu¬ lating the gravity flow of fluid from the first chamber into tne second cnamber, the fluid flow regulating means comprising means for selectively moving the first and second chambers along the longitudinal axis. Further in¬ cluded are means for enabling a fluid-flow connection be¬ tween the fluid inlet end region of the first cnamoer and a lower, discharge region of a preexisting source of fluid that is open to ambient surrounding pressure through a collapsible container or a filtered vent. Still further included is a fluid level control for causing, when the connecting means connects the first chamber to the preexisting source of fluid for receiving a flow of fluid therefrom, a preestablished fluid level to be substantially maintained in said first chamber as the fluid level in the connected source decreases, the fluid level control means including an orifice at the fluid inlet end region of the first chamber and a free- floating float valve disposed in the first chamber con- figured for blocking the orifice to stop a gravity flow of fluid through tne orifice from the source wnen the fluid level in the first chamber is at a preestablished level and for floating downwardly and unblocking the ori¬ fice to permit a gravity flow of fluid through the ori- fice from the source when the fluid level in the first chamber falls below the preestablished level and until the fluid level returns to the preestablished level, whereby the valve floats upwardly and again blocks off the flow of fluid through the orifice. Preferably, the fluid flow includes an indicator calibrated with respect to vertical positioning of the second chamber relative to the first chamber for enabling a user to read fluid flow rates from the first chamber into the second chamber associated with different rela¬ tive vertical positions of the first and second chambers. It is preferred that closing means in the second chamber includes a float valve having a closure region which closes a fluid discharge opening in the lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestablished lower level and closes a fluid mlet opening into the second chamber when the fluid level in the second chamber reaches a preestablished upper level. Also preferably, there is included a scale calibrated with respect to relative ax¬ ial movement between the first and second chambers for enabling a user to set a selected fluid flow rate from the first chamber mto the second chamber. Means are provided for frictionally locking the first and second chambers in any selected relative posi¬ tion therebetween. There is accordingly provided a fluid flow control device and first and second variations thereof, particu¬ larly for use in an IV supply system, which, as an illus- tration, provides a constant fluid head as the fluid level in a source of IV fluid to which the device is con¬ nected decreases as the fluid is introduced into and through the device into a patient's body. BRIEF DESCRIPTION OF THE DRAWINGS: The present invention can be more readily understood by a consideration of the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a pictorial drawing which illustrates a typical manner in which the flow rate control device of the present invention may be used to advantage, there be¬ mg shown the device connected to an exemplary IV solu- tion or fluid container and showing the output of the de¬ vice being connected, through an IV tube, into the arm of a reclining patient; FIG. 2 is a partial perspective drawing of the flow rate control device of the present invention, showing the external configuration thereof and showing the upper, in¬ let end of the device connected to a lower region of an exemplary IV fluid container and snowing the lower, out¬ put end of the device connected to an upper end region of a patient fluid delivery tube and showing a transparent drip chamber portion of the device; FIG. 3 is a longitudinal cross sectional view taken along line 3-3 of FIG. 2 showing the internal construc- tion of the flow rate control device and showing a first, upper, free-Iloat ng float valve, a flow regulating valve and a second, lower, free-floating float valve for con¬ trolling and regulating fluid flow through the device; FIG. 4 is a partially cutaway perspective drawing of a representative one of the first and second free- floating float valves, showing the external configuration thereof with upper and lower end caps configured for hav¬ ing only minimal edge contact with their respective de- vice chambers; FIG. 5 is a perspective drawing of a variation flow rate control device having first and second chambers which are vertically movable relative to one another for regulating tne flow cf fluid from a first chamber into a second, drip, chamber; FIG. 6 is a longitudinal cross sectional view taken along line 6-6 of FIG 5, showing the internal construc¬ tion of the first variation device, including a first, upper, free-floating float valve and a second, lower, free-floating float valve for fluid flow through the de¬ vice; FIG. 7 is a partial cross sectional view similar to FIG. 6, showing the second chamber of the variation de¬ vice elevated to a maximum-enabled position relative to first chamber; FIG. 8 is a perspective drawing of a second variation fluid rate control device, which is similar to the first variation fluid flow rate control de¬ vice, showing m-lme first, upper and second, lower chambers and showing index markings corresponding to fluid flow rats end further showing, by way of illustra¬ tion, the device set for delivering 200 Ml/Hr. of salme to a patient; FIG. 9 is a longitudinal cross section drawing taken along line 9-9 of FIG. 8, showing internal construction of the second variation fluid flow rate control device, including first, upper and second, lower float valves; FIG. 10 is a transverse cross sectional draw¬ ing taken along line 10-10 of FIG. 8, showing further in¬ ternal features of the second variation fluid flow control device; FIG. 11 is a partially cut-away perspective drawing of the upper float valve of the second variation fluid flow control device showing its annular construction; FIG. 12 is a longitudinal cross sectional drawing, similar to FIG. 9 showing internal construction of the second variation flow rate control device of FIG. S when set for maximum flow rate; and FIG. 13 is a longitudinal cross sectional drawing similar to FIG. 9 showing internal construction of the second variation flow rate control αevice of FIG. 8 when set for zero flow rate. In the various FIGS., identical elements and fea¬ tures are given the same reference numbers; for the first variation, elements and features similar to those of the preferred embodiment are given the same ref¬ erence numbers followed by an "a" and for the second variation, elements and features similar to those of the preferred embodiment and the first variation are given the same reference numbers followed by a "b" as will be clear from the following description. DETAILED DESCRIPTION OF THE INVENTION: In FIG. 1 there is depicted a flow rate control de¬ vice or system 10, in accordance with the present inven¬ tion. Device or system 10 is shown, by way of illustra¬ tive example, and as more particularly described below, connected, at an upper inlet end region, in fluid receiv¬ ing relationship to a conventional IV supply source of container 12, which is depicted as being supported at an elevated level by a conventional IV stand 14. A lower end region of device 10 is shown connected in a fluid discharging relationship to the upper end of a conven¬ tional IV fluid supply conduit or tube 16 which nas a lower end connected to a canula (not shown) mserted mto an arm 18 of a patient 20 shown reclining on a hospital bed 22. As shown in FIGS. 2 and 3, and as mors particularly described below, flow rate control device or system 10 is externally constructed of a generally tubular upper shell segment 30, naving joined to an upper end thereof a lower region 32 of a hollow inlet member 34, and a tubular lower shell segment 36, having joined to a lower end thereof an upper end region 38 of a discharge member 40. A lower end region 42 of upper shell segment 30 is joined to the upper end of lower shell segment 36 so as to form a slender, vertically-elongated and substantially closed device body *J . As best seen from FIG. 3, an upwardly-projecting end region 46 of inlet member 34 (which is preferably con¬ structed from a medical-grade plastic) is formed in the shape of a slender, tapered, hollow spike having a rela¬ tively sharp, beveled upper end 48 which enables fluid- flow penetration of the inlet member througn a seal or plug 50 at a lower, discharge end region 52 of fluid con¬ tainer 12 to thereby enable the gravity flow of fluid from the container into upper segment 30. A downwardly-extending end region 54 of discharge member ^0 is formed in slender tubular shape for receiv¬ ing an upper end of tube or conduit 16 to enable fluid flow from device 10 into patient 20. As furtner shown in FIG. 3, internal surfaces of up¬ per shell segment 30 and inlet member 3-- largely form or define a first, upper chamber 60, and internal surfaces of lower shell segment 36 and discharge member 40 largely form or define a second, lower chamber 62. At least regions, and preferably all, of lower shell segment 36 are formed of a transparent material, (for ex- ample, medical grade plastic such as polystyrene) , so that fluid flowing through lower chamber 62 in the form of droplets 64 can be viewed and counted by a user of de- vice 10 to obtain and/or monitor the fluid flow rate (for example, in milliliters per hour) through the device. Shown formed integrally in lower regions of upper shell segment 30 (and more particularly described below) are fluid flow regulating means 66 whicn regulate the gravity flow of fluid from first, upper chamber 60 into second, iower cnamoer 62, and consequently through device 10. Also as more particularly descrioed below, first, upper, fluid flow controlling means 70 are disposed in first, upper chamber 60 for maintaining a predetermined, uniform fluid level 72 in such cnamber as level 74 of fluid 76 (FIG. 2j container 12 cnanges as fluid flows from tne contamer into and tnrough device 10. That is, upper fluid flov; controlling means 70 provide a constant fluid pressure heao in device 10 regardless of the chang¬ ing pressure head in fluid contamer 12 as fluid is drawn therefrom. Second, lower, fluid flow controlling means 80 are disposed in second, lower chamber 62 for stopping the flow of fluid from such cnamber mto tube 16 when the fluid level in such chamber falls below a predetermined minimum level 82 so as to prevent tne introduction of air into fluid being discharged from device 10. Second, lower, fluid flow containing means 80 are also config¬ ured, relative to the height of second chamber 62 for shutting off the flow of fluid mto the lower chamber from upper chamber 60 when the fluid level in the lower chamber reaches a preestablished maximum level 84 (shown in phantom lines, FIG. 3) . An upper vent tube 90 is connected through a side wall of upper member 34 to vent upper chamber 60 to at¬ mosphere. A conventional micropore filter element 92 is installed in filter tube 90 to maintain sterility of the upper chamber. Similarly, a lower vent tube 94, having a micropore filter element 96 is connected through a lower, side wall region of upper shell segment 30 to vent lower chamber 62 to atmosphere while maintaining sterility of the chamber. Flow regulating means 66, as depicted in FIG. 3, comprises a generally conventional, screw-type, fluid flow regulating valve which includes flow respective up¬ per and lower vertical fluid channels 100 and 102 formed in a lower region 104 of upper shell section 30. Fluid channels 100 and 102, which enable the flow of fluid from upper chamber 60 into upper regions of lower chamber 62 are interrupted by a valve shaft 106 having a tapered flow control section 108. An external control knob 110 connected to a proximal end of shaft 106 enables a user to rotate the shaft so that tapered section 108 is drawn to the right. This ac- tion opens, in varying degrees, the flow path between channels 100 and 102 so as to provide a variable cross section conduit enabling the regulation of fluid flow from upper chamber 60 into lower chamber 62, to the de¬ sired or required flow rate. A fluid flow indicating scale 112 may be provided beneath knob 110 to indicate, according to the rotational position of the knob, the precise fluid flow rate through regulating means 66. However, the flow rate may be veri¬ fied by a user by counting the rate at which fluid drop- lets 64 fall through second chamber 62. A conventional O-ring seal 114 is installed around valve stem 106 to prevent fluid leakage past the shaft and from device 10. First, upper flow control means 70 comprises a buoy¬ ant first float valve 120 which is sized and configured for freely floating in a vertical direction mside of up¬ per chamber 60. As best seen in FIG. 4, first float valve 120 comprises a light-weight, cylindrical plastic tubular body 122 having generally square, upper and lower end caps 124 and 126, respectively. The outer diameter, Di, of body 122 is smaller than inner diameter, D 2 , of upper chamber 60 (FIG. 3) . As shown for representative bottom end cap 126, all corners 128 thereof extend radially outwardly from body 122, in a symmetrical manner about a vertical axis 129 of valve 120, and terminate in short arcuate eno or corner surfaces 130 wnich define a circle having a diameter, D , which is slightly smaller that the inside diameter, D 2/ of upper chamber 60. Edge surfaces 130 function as guide surfaces making minimal contact with tne inside of upper chamoer 60 as valve 120 floats freely up and down, ac¬ cording to the fluid level in the cnamber. As shown in FIG. 4 for upper end cap 124, an upper surface 132 thereof is slightly convex and has a small flat circular central surface region 134 whicn functions as a flow-blocking surface when valve 120 floats upwardly in upper chamoer 60 until such surface bears agamst, and blocks the gravity flow of fluid from a mating fluid on- fice 136 at the lower end of a tubular downward extension 138 of spike 46 (FIG. 3) . Preferably, upper and lower valve end caps 124 and 126 are identical to one another and are joined to re¬ spective upper ano lower ends of body 122 in a manner sealing first float valve 120 against fluid leaks which would affect buoyancy of the valve. It is also preferable that second, lower flow con¬ trolling means 80 comprise a second, lower valve 140 which is identical in function, and also preferably in construction, to above-described first, upper valve 120. Lower valve 140 is free to float up and down in second chamber 62 between lower and upper preestablished fluid levels 82 and 84, respectively, according tc the fluid level in the second chamber, and thereby opening and closing an outlet orifice or opening 150 at the bottom of the second chamber and an inlet orifice or opening 152 through which fluid s dropped into the second chamber. By way of illustrative example (referring to FIG. 2), the overall length, L, of device 10 may be about 18 centimeters and the outside diameter, OD, of sections 30 and 36 may be about 2.5 centimeters. It can be appreci¬ ated that the constant fluid column height across flow control 66 is essential to the precision cf fluid flow control provided Dy device 10. OPERATION OF DEVICE 10 The operation of fluid flow controlling device 10 is readily apparent from the above description thereof n conjunction witn associated FIGS 1-4 a brief summary of the operation of device 10 follows. When constructed and assembled in the above- described manner, device 10 is ready for being operation¬ ally installed between fluid container 12 and fluid tube 16 into a patient 20 by inserting device spι e 46 through container seal 50 and installing fluid tube 16 onto de¬ vice bottom projection 5^ (FIGS. 1-3) . Upon such installation (assuming that fluid is con¬ tained in contamer 12, that device 10 is hanging in a substantially vertical orientation as depicted in FIGS. 2 and 3, and that flow regulator valve 66 is closed) first float valve 120 will initially be resting at the bottom of first chamber 60 and second float valve 140 will be resting at the bottom of second chamber 62. As fluid flows into first chamber 60 from fluid container 12, the fluid level in the first chamber will rise, causing first float valve to float upwardly toward fluid inlet opening 136. When the preestablished fluid level 72 is reached in first chamber 60, first float valve 120 will have floated to an elevation where upper surface region 134 of valve upper cap 124 blocks off further fluid flow into the first chamber. Flow regulator valve 66 is then opened slowly to establish the desired or required fluid flow rate from first chamber 60 into second chamber 62 (for example, by counting the number of droplets 64 falling through the second chamber over a given time interval) . This flow of fluid from first chamber 60 into second chamber 62 causes the fluid level in the first chamber to fall, thereby causing first float valve 120 to float downwardly and open mlet opening 136 so that additional fluid can flow from container 12 nto the first cnamber until the preestablished fluid level is again reached and the first float valve again seals off fluid flow to the first chamber. In this manner, an equilibrium situation is reached wherein as each crop of fluid flows from first cnamber 60, through regulator valve 66, first float valve 120 floats down ust a sufficient distance to permit a simi¬ lar drop of fluid to be flowed from fluid container 12 into the first chamber before the first float valve floats back up and again shuts off the inflow of fluid from the fluid contamer. Second float valve 140 in second chamber 62 func¬ tions in a reverse manner to meter fluid from the second chamber into tube 16 and on to patient 20. After ini¬ tially being lifted upwardly by fluid received from first chamber 60 accumulating in lower regions of second cham¬ ber 62 to the preestablished minimum level, second float valve unblocks outlet opening 150 sufficiently to permit a drop equivalent of fluid to be discharged into tube 16. This causes a decrease in the fluid level in second cham¬ ber sufficient for second float valve to float down and reclose discharge opening 150 until the valve is relifted by a next drop of fluid dropping into the second chamber, such that each drop of fluid entering second chamber 62, a like volume is discharged therefrom into tube 16 and thence to patient 20. If the flow of fluid from second chamber 62 into tube 16 is blocked in the tube or patient (the latter, for example, by a collapsed vein), fluid backs up in the second chamber until second valve 140 floats to the top of the chamber and cuts off the inflow of fluid until the blockage in the tube or patient is cleared. With respect to the foregoing operation, it will be appreciated that the various preestablished fluid levels 72, 82 and 84 are selected in combination with the char¬ acteristics of the first and second float valves to cause the described operation. FIRST VARIATION OF FIGS. 5-7: A first variation fluid flow control device 10a is depicted in FIGS 5-7. In these FIGS. 5-7, elements and features of device 10a that are identical to those de¬ scribed above for device 10 are given the same reference numbers. Those elements and features of device 10a which are similar or equivalent to those elements and features described above for device 10 are given the same refer- ence numbers followed by an "a." Entirely different ele¬ ments and features of device 10a are given new reference numbers . It is to be understood that although device 10a dif¬ fers in external appearance from above-described device 10, its function and operation are similar except for the construction (described below) of flow regulating means 66a. As shown in FIGS. 5-7, device 10a comprises a first, tubular upper shell segment 30a and a second, lower tubu- lar shell segment 36a. Upper segment 30a is constructed to form an internal first chamber 60 having a first float valve 120 disposed therein. First chamber 60 is vented to atmosphere by a vent 90. Lower segment 36a is con¬ structed to form a second chamber 62 having a second float valve 140 disposed therein. Second chamber 62 is vented to atmosphere through a vent 94. A tapered, tubular spike 46a at the top of upper segment 30a is provided for penetrating through a seal 50 at a lower end 52 of a fluid source 12 (FIG. 6) to permit the gravity flow of fluid through an orifice 136 at the lower end of extension 138 into first chamber 60. Respective upper and lower segments 30a and 36a of device 10a are constructed in substantially the same man¬ ner, and function in the same way, described above, as corresponding upper and lower segments 30 and 36 of de¬ vice 10. The principal difference between device 10a and de¬ vice 10 is that the gravity flow of fluid from first chamber 60 of upper segment 30a into second cnamber 62 of lower segment 3ba is reαuiated by the relative vertical position between the upper and lower segments. To this eno, a flexible f_uιd conouit 200 _s connected between a lower region of upper segment 30a and an upper region of lower segment 36a (FIGS. 5 and 6) . Flow regulating means 66a comprises a vertical sup¬ port member 202 wnich extends downwardly from tuoular re¬ gion 204 at the bottom of upper segment 30a. Vertically slidingly mounted over memoer 202 is a slide 206 which is connected to lower segment 36a so as to extend sidewardly therefrom (FIGS. 5-7) The relative neignt, n, between upper segment 30a and lower segment 36a can be easily adjusted, to regulate the flow of fluid from first cnamoer 60 into second cham¬ ber 62, by slidmq slide 206 (and consequently the lower segment) up or down on support memoer 202. The effect of sliding lower segment 36a upwardly or downwardly on sup¬ port member 202 actually varies tne height, h, between fluid level 72 in first chamber 60 and fluid discharge opening 152 into second cnamber 60. A fixed orifice 207 installed anywhere m conduit 200 in the fluid path between the lower portion of upper segment 30a and the upper portion of lower segment 36a provides an accurate, calibratec relationship between fluid height, h, and fluid discnarge rate nto second chamber 60. A scale 208 may be engraved or other wise formed on support member 202 wnich is calibrated, for example, in milliliters per hour, to correspond to the precise fluid flow provided for various positions of slide 206 along the support member. As mentioned above, however, fluid flow rates can be verified by observing the drip rate of fluid through second chamber 62 (that is, by counting droplets 64 as they fall through the second chamber) . Locking means 210, for example a clamp, are preferably provided for clamping slide 206 at any selected point along support member 202. Operation of device 10a s otnerwise the same as de- scribed above for device 10. SECOND VARIATION OF FIGS. 8-13: A second variation fluid flow control device 10b, which is an "in-line" version of above described first variation device 10a, is depicted in FIGS 8-13. In these FIGS. 8-13, elements and features of device 10b that are identical to those described above for device 10 are given the same reference numbers. Those elements and features of device 10b which are similar or equivalent to those elements and features described above for device 10 or first variation 10a are given the same reference num¬ bers followed by a "b." Entirely different elements and features of device 10b are given new reference numbers starting at reference number 300. It is to be understood that although device 10b dif¬ fers in external appearance from above-described αevice 10a, its function and operation are similar, except for the construction (described below) of flow regulating means 66b, to first variation flow rate control device 10b. As shown in FIGS. 8-13, device 10b comprises a first, tubular upper shell segment 30b and a second, lower tubular shell segment assembly 36b. Upper segment 30b is constructed to form an internal first chamber 60b having a first, annular-shaped float valve 120b disposed therein. First chamber 60b is vented to atmosphere by a vent 90. Lower segment or segment assembly 36b is constructed of an upper, inner tubular portion 300 and a lower tubu- lar segment 302 to form a second chamber 62b having a second float valve 140b disposed in the lower tubular segment thereof. Further comprising lower segment 36b is an outer, tubular shell portion 304 which is disposed around upper, inner tubular portion 300 and is spaced ra¬ dially outwardly tnerefrom( IGS . 9, 10, 12 and 13) . As shown in such FIGS., second chamoer 62b is vented to at- mosphere through a vent 94. Upper segment 30b and lower segment assembly 36b of device 10b function in the same general way, described above, as corresponding upper and lower segments 30a and 36a of device 10a. The principal difference between de- vice 10b and 10a is that the upper segment 30b and lower segment assembly 36b are "in line" with one another; that is, they are vertically aligned relative to one another along a common vertical axis 129b. This is in contrast to upper and lower segments 30a and 36a of device 10a, wnich are positioned in a general side-oy side, offset relationship. In device 10a, as described aoove, flow rate control from fluid source 12 through the device is controlled by relative vertical movement between upper and lower seg- ments 30a and 36a. In a like manner, fluid flow rate from fluid source 12 through device 10b is controlled by relative vertical movement between upper segment 30b and lower segment assembly 36b. This vertical, in line alignment of upper segment 30b and lower segment assembly 36b requires a different internal construction of device 10b than that of device 10a, as will be further described below. A tapered, tubular spike 46b at the top of upper segment 30b is provided for penetrating through a seal 50 at a lower end 52 of a fluid source 12 (FIGS. 8 and 9) to permit the gravity flow of fluid through an orifice 13βb at the lower end of an extension 138b into first chamber 60b (FIG. 9) . A fitting 306, such as a female luer fit¬ ting, at the lower end of lower segment 302 enables a pa- tient feed tube 16b to be connected to device 10b. Upper float valve 120b is constructed in an annular configuration as snown in FIGS. 9-13, and as is best shown in FIG. 11. Comprising upper float valve 120b are a tubular outer wall 122b of circular cross section and a tubular inner wall 310 also of circular cross section, which is concentric with the outer wall Both inner and outer walls 310 and 122b are of eαual lenqths An upper end cap 132b, whicn is attached to upper ends of inner and outer walls 310 and 122b to seal off such upper ends, is formed having a small diameter, cen¬ trally located flat (or cone) 134D wnicn functions as a stop to shut off flow of fluid into upper chamber 60b through orifice 136b when upper float valve 120b is at its uppermost position, as depicted in FIG. 13 A washer-shaped lower end cap 126b, which has a cen¬ tral opening 312 (FIG. 11) the size of inner wall 310, is attached to lower ends of the inner and outer walls 310 and 122b to seal off such lower ends . End caps 132b and 126b and inner and outer walls 310 and 122b define an an¬ nular air space 314 between the inner and outer walls which provides buoyancy to float valve 120b. A plurality of apertures 315 are formed axially through upper end cap 132b to enable the flow of liquid into a cylindrical space or region 316 side of inner wall 310 Region 316 has a diameter, D4 , wnich is some¬ what larger than the outside diameter, D5, of lower seg¬ ment portion 300 (FIG. 10) to enable clearance and the flow of fluid therebetween. Lower float valve 140b, which is substantially iden¬ tical in all respects, except possibly in overall size, with above-described lower float valve 140 is installed in lower segment portion 302 and is freely floating therein. When fluid flow from device 10b is occluded, the fluid level in chamber 62b rises, thereby causing lower float valve 140b to float upwardly until the valve blocks openαng 322 into the lower segment portion and the flow of fluid thereinto is stopped in the manner de- scribed above with respect to the operation of lower float valve 140 of device 10. To further assemble device 10b, upper portion 300 of lower segment assembly 36b is installed upwardly through a central aperture 324 in a case portion 326 of upper segment 30b (for example, FIG. 9) . An O-rmg seal 328 installed in base portion 326 around opening 324 provides a fluid seal between upper segment 30b ana lower segment 36b. As best shown FIG. 8 (and also shown in FIG. 10), shell portion 304 of lower segment assembly 36b s formed having a slot 330 wnich extends downwardly from an upper edge 332 of the shell portion to a short distance above a bottom edge 334 of the shell portion. Associated with slot 330, when device 10b is assembled as shown m the various FIGS. 8-10 and 12-13, is an elongate, ridge or boss 336 wnicn is formed downwardly along upper segment 30b so as to project mto the slot (FIGS. 8 and 10) . There is preferably marked in or on boss 336, m a generally central position, an index mark or arrow 338. Associated with index arrow 338, there is shown marked, by way of example, on shell portion 304 adjacent one side of slot 330 a calibrated flow rate scale 340 in Ml/Hr. for glucose and a calibrated flow rate scale 342, adja¬ cent the other side of the slot for saline(FIG. 8) . As more particularly described below, when lower segment 36b is moved upwardly on upper segment 30b, the fluid flow rate through device 10b is decreased, DF, and when lower segment 36b is moved downwardly on upper seg¬ ment 30b, the fluid flow rate through device 10b is in¬ creased, IF, index arrow 338 pointing an scales 340 and 342 to the corresponding flow rate through device 10b. As depicted in FIG. 8 by way of illustration, with no limi- tation being thereby intended or implied, lower segment assembly 36b is slidingly positioned relative to upper segment 30b for a saline flow rate of 200 Ml/Hr. As shown in FIG. 9, upper portion 304 of lower seg¬ ment 36b is formed having an axially spaced apart pair of small, inwardly-directed circumferential beads or ridges 350 at an upper end of the upper portion. A similar but outwardly projecting circumferential bead 352 is formed around the lower end region of upper segment 30b. When assembled as shown in FIG. 9, beads 350 bear lightly agamst an outer surface 354 of upper segment 30b and bead 352 bears ligntly against an inner surface 356 of lower segment portion 30*- so as to reduce the amount of force required to slide the lower segment up and down the upper segment for adjusting the flow rate of liquid through device 10b the manner described below. Beads 350 perform the additional function of ena¬ bling the frictional locking of lower segment 36b to up- per segment 30b when a flow rate has been selected by moving the lower segment up or down the upper segment. Such frictional locking is acco plisned by the partial rotation of lower segment 36b relative to upper segment 30b in the direction of Arrow B (FIG. 8) by an amount sufficient for eno regions of beads 350 to ride up onto boss 336. For this and other purposes, upper portion 304 is constructed of a slightly flexible material, such as a tough plastic (for example, PVC, urethane or LEXAN), to enable such releasable, flexible locking of upper and lower segments 30b and 36b together. Referring to FIG. 9, it is obvious from the previous descriptions of related devices 10 and 10a, that in use (that is, when conduit 16b is connected to deliver liquid to a patient) liquid normally flows from source 12 through inlet orifice 136b and around the top of upper float valve 120b mto upper chamber 60b. In such in¬ stance, the liquid level in upper chamber 60b is at an equilibrium level 72b. As liquid in upper cnamber 60b falls below equilibrium level 72b, upper float valve 120b floats downward, thereby permitting more liquid to flow from source into upper chamber 60b until equilibrium liq¬ uid level 72b is reestablished. When, on the other hand, liquid ceases flowing through conduit 16b to the patient and fluid flow is stopped from entering lower chamber 62b by lower float valve 140b (as described above), the liquid level in first chamber 60b starts to increase above equilibrium level 72b, thereby causing first float valve to be lifted. This m-flow of liquid continues unti.. upper float valve 120b is lifted by the rising liquid level and completely closes fluid let opening 136b. It will, of course, be appreciated that the distance of above-descriDed downward and upward floating movement of upper float valve 120b is ordιnar_ly so s m all as to be virtually unobservable. As shown in FIGS. 9 and 12-13, cylindrical region 316 defined by inner wall 310 of upper float valve 120b is filled with liquid to liquid level 72b. Liquid from such region 316 is discharged into lower chamber 62b through an upper orifice 360 formed at the top of upper portion 300. From orifice 360 liquid drips in droplets 64 into lower regions of lower chamoer 62b ano onto lower float vaive 140b. Liquid accumulates (after startup) in lower chamber 62b until it reaches an equilibrium level 82 at whicn lower float valve 140b just floats up from discharge orifice 150b at the bottom of the lower cham¬ ber. Thereafter a drop of liquid is discharged from lower chamber 62b into patient conduit 16b for each drop 64b falling mto the lower chamber from upper orifice 360. When there is no liquid in lower chamber 62b, lower float valve 140b closes off orifice 150b to prevent con- tamination of the lower chamber from the outside. On the other hand, if conduit 16b to the patient is blocked and liquid continues to be flowed into lower chamber 62b, the liquid level rises in lower chamber 62b causing lower float valve 140b to float upwardly until it blocks off inlet opening 322, thereby blocking the flow of liquid into the lower chamber. The rate of liquid flowing into lower chamber 62b from upper chamber 60b depends on the liquid head, Hd, over upper orifice 360 (FIG. 9) . It is evident that when lower segment 36b is moved downwardly as far as permitted by beaαs 350 and 352 (FIG. 12), the liquid head, Hd, over orifice 360 (from liquid level 72b) is a maximum and the flow rate into patient conduit 16b is maximized. Note that FIG. 9 depicts an intermediate flow rate condition wherein lower segment 36b is at an intermediate position relative to upper segment 30b and liquid flow into pa- tient conduit 16b is less than the maximum. FIG. 13 depicts a "no liquid flow" condition in which lower segment 36b is pushed upwardly as far as per¬ mitted relative to upper segment 30b. As can be seen, m this condition, an upper end surface 364 of upper portion 300 pushes upwardly on an under surface 366 of upper end cap 132b of the upper float valve, thereby pushing the end cap against mlet orifice 136b to positively stop liquid flow from source 12 into upper chamber 60b. After the desired flow rate has been set in the above-described manner, lower segment 36b is partially rotated relative to upper segment 30b in the direction of Arrow B (FIG. 8) to lock device 10b at the selected flow rate. Once the desired flow rate has been selected, a constant liquid head, Hd, is maintained in device 10b and assures that the selected flow rate is maintained. A user may confirm the selected flow rate Dy counting drops 64 falling through lower portion 302 of lower segment 36b. To enable the counting of drops 64, at least a por¬ tion of aside wall of lower portion 302 is constructed of a transparent material, such as a transparent plastic. Although there has been described and illustrated a flow rate control device (especially adapted for control¬ ling the flow of IV fluid) and variations thereof, having a constant fluid head and variable flow control orifice or variable fluid head and a fixed size flow control ori¬ fice provision in accordance with the present invention for purposes of illustrating the manner in which the in¬ vention may be used to advantage, it is to be appreciated that the invention is not limited thereto. Therefore, any and all variations and modifications that may occur to those skilled in the applicable art are to oe considered as being withm tne scope ano spirit of tne claims as ap¬ pended hereto.

Claims: THE CLAIMS What is claimed is. Claim 1. A gravity flow fluid flow device with con- stant fluid nead provision, said device comprising: a. a first, constant fluid head chamber hav¬ ing an upper fluid mlet eno region and a _ower, fluid outlet region; b. a second, drip chamoer having an upper fluid mlet eno region and a lower, fluid outlet end re¬ gion, said lower fluid outlet end region being configured for having attacneo thereto a conventional discharge tube; c fluid flow regulating means connected in fluid flow relationsnip between the fluid outlet end re¬ gion of said first chamber and the fluid let end region of said second chamber for regulating the gravity flow of fluid from the first chamber into the second chamber; and d. means for enabling a fluid-flow connection between the fluid inlet end region of the first chamber and a lower, dj3c arge region of a preexisting source of fluid that is open to ambient surrounding pressure through a collapsible container or a filtered vent; and e. fluid level control means disposed in said first chamber for causing, when said connecting means connects said first chamber to said preexisting source of fluid for receiving a flow of fluid therefrom, a prees¬ tablished fluid level to be substantially maintained in said first chamber as the fluid level in said connected source decreases, said fluid level control means includ¬ ing an orifice at the fluid let end region of said first chamber and a free-floating float valve disposed in said first chamber configured for blocking said orifice to stop a gravity flow of fluid through said orifice from said connected source when the fluid level n said first chamber is at said preestablished level and for floating downwardly and unblocking said orifice to permit a grav¬ ity flow of fluid through said orifice from said con¬ nected source wnen the fluid level in said first chamber falls below said preestablished level and until the fluid level returns to said preestablished level whereby said valve floats upwardly and again blocks off the flow of fluid throuαh saiα orifice. Claim 2. The gravity flow fluid flow device as claimed in Claim 1, wherein said source of fluid is IV fluid. Claim 3 The gravity flow fluid flow device as claimeα in Claim 1, wherein at least a side wall region of said second cnamber is constructed of a transparent material so that a rate of fluid dripping through said second chamber can be observed. Claim -- . The gravity flow fluid flow device as cla ed ^ " Claim 1, including first venting means located at an upper region of said first chamber above said preestablished fluid level for venting the first chamber to ambient surrounding pressure. Claim 5. Tne gravity flow fluid flow device as claimed in Claim 1, including second venting means lo¬ cated at an upper region of said second chamber for vent¬ ing the second chamber to ambient surrounding pressure. Claim 6. The gravity flow fluid flow device as claimed in Claim 1, wherein said fluid flow regulating means comprise a valve body naving a rotatably-mounted valve stem for incremental rotational movement between a first, fully-closed position which blocks the gravity /11729 flow of fluid from the first chamber into the second chamber and a second, fully-open position in which the gravity flow of fluid from the first chamber into the second chamber is at a maximum flow. Claim 7. The gravity flow fluid flow device as claimed in Claim 6, wherein said valve stem is disposed in said valve body for being manually set at any selected rotational position between said first and second posi- tions so as to thereby enable a user to selectively con¬ trol the gravity flow of fluid from said first chamber into said second chamber. Claim 8. The gravity flow IV fluid flow device as claimed in Claim 7, including an indicator calibrated with respect to rotational positions of said valve stem for enabling a user to read fluid flow rates from the first chamber into the second chamber associated with different rotational positions of said valve stem. Claim 9. The gravity flow IV fluid flow device as claimed in Claim 1, wherein said fluid flow regulating means comprise a flexible fluid conduit connected in fluid flow relationship between the outlet end region of the first chamber and the fluid inlet end region of the second chamber. Claim 10. The gravity flow fluid flow device as claimed in Claim 9, wherein said fluid flow regulating means further comprise means for selectively controlling the vertical distance between said first chamber and said second chamber. Claim 11. The gravity flow fluid flow device as claimed in Claim 1, including means disposed in said sec- onα chamber for closing said lower, fluid outlet enα re¬ gion when no fluid is gravity flowing through ^.o out thereof. Claim 12. The gravity flow fluid flow device as claimed in Claim 11, wherein said closing means mclude a float valve having a closure region wnich closes a fluid discnarge opening m said lower, fluid discnarge cutlet end region when the fluid level in the second chamoer is below a preestablished lower level and closes a fluid in¬ let opening into the second chamber when the fluid level in tne second chamoer reacnes a preestablished upper level . Claim 13. A gravity flow IV fluid flow device with constant fluid head provision, said device comprising: a. a first chamoer having an upper fluid in¬ let end region having a fluid flow orifice and a lower, fluid outlet region; b. means for enabling a fluid flow connection between the fluid let end region of the first ciiamDer and a lower, discnarge region of a preexisting, closed source of IV fluid so as to enable the gravity flow of fluid from said source through said fluid flow orifice into said first chamber; c. float valve means disposed in said first chamber for blocking said fluid flow orifice to stop the gravity flow of fluid from a connected source of IV fluid into the first chamber through said fluid flow orifice when the fluid level in said first chamber is at a prees¬ tablished fluid level and for unblocking said orifice to permit the gravity flow of fluid from said connected source of IV fluid through said fluid flow orifice wnen- ever the fluid level in said first chamber is lower than said preestablished fluid level, said float valve means 3 d including a float valve constructed for freely floating up and down m said first chamber m response to changing fluid levels in said first chamber; α. a second, drip cnamber having an upper fluid inlet end region and a lower, fluid outlet end re¬ gion, saiα lower fluid outlet enα region being configured for having attacneα thereto a conventional IV tube for providing fluid mto a patient's oooy; and e. fluid flow regulating means connected in fluid flow relationship between tne fluid outlet end re¬ gion of said first chamber and the fluid mlet end region of said second chamber for regulating tne gravity flow of fluid from tne first chamber into the second chamber. Claim 14. The gravity flow IV fluid flow device as claimed in Claim 13, wherein at least a side wall region of said second cnamoer is constructed of a transparent material so that a rate of fluid dripping through said second chamber can be observed. Claim 15. Tne gravity flow IV fj.uια flow device as claimed in Claim 13, including first venting means lo¬ cated at an upper region of said first chamber above said preestablished fluid level for venting the first chamber to ambient surrounding pressure and second venting means located at an upper region of said second chamber for venting the second chamber to ambient surrounding pres¬ sure. Claim 16. The gravity flow IV fluid flow device as claimed in Claim 13, wherein said fluid flow regulating means comprise a valve body having a rotatably-mounted valve stem for incremental rotational movement between a first, fully-closed position which blocks the gravity flow of fluid from the first chamber into the second cnamoer and a second, fully-open position in whicn the gravity flow of fluid from the first cnamoer mto the second chamber is at a maximum flow, said valve stem be¬ ing disposed m said valve oooy for oemg manually set at any selected rotational position σetween said first and second positions so as to tnereoy enaDle a user to selec¬ tively control the gravity flow ot fluid from said first chamber into said second cnamber. Claim 17. The gravity flow IV fluid flow device as claimed in Claim 16, including an indicator calibrated with respect to rotational positions of said valve stem for enabling a user to read fluid flow rates from the first chamber into the second cnamoer associated with different rotational positions of saiα valve stem. Claim 18. The gravity flow IV fluid flow device as claimed in Claim 13, wherein said fluid flow regulating means comprise a flexible fluid conduit connected in fluid flow relationship betv/een the outlet end region of the first chamber and the fluid mlet end region of the second chamber and means for selectively controlling the vertical distance between said preestablished fluid level said first chamoer and the fluid mlet region of the second chamber. Claim 19. The gravity flow IV fluid flow device as claimed in Claim 13, including means disposed in said second chamber for closing a fluid discharge opening in said lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestab¬ lished lower level and closing a fluid inlet opening into the second chamber when the fluid level in the second chamber reaches a preestablished upper level. Claim 20. A gravity flow IV fluid flow device with constant fluid heao provision, said device comprismg: a. a first chamber havmg an upper fluid in¬ let end region having a fluid flow orifice and a lower, fluid outlet region; b. means for enabling a fluid flow connection between tne fluid mlet end region of the first chamber and a lower, discharge region of a preexisting, closed source of IV fluid so as to enaole the gravity flow of fluid from said source through said fluid flow orifice into said first chamber; c. a free-floating float valve disposed in said first chamber for blocking said fluid flow orifice to stop the gravity flow of fluid from a connected source of IV fluid into the first chamber through said fluid flow orifice when the fluid level in said first chamber is at a preestablished fluid level and for unblocking said orifice to permit the gravity flow of fluid from said connected source of IV fluid through said fluid flow orifice whenever the fluid level in said first chamber is lower than said preestablished fluid level; d. a second, drip chamber having an upper fluid inlet end region and a lower, fluid outlet end re¬ gion, said lower fluid outlet end region being configured for having attached thereto a conventional IV tube for providing fluid into a patient's body; and e. fluid flow regulating means connected in fluid flow relationship between the fluid outlet end re¬ gion of said first chamber and the fluid inlet end region of said second chamber for regulating the gravity flow of fluid from the first chamber into the second chamber, said flow regulating means comprising a valve body having a rotatably-mounted valve stem for incremental rotational movement between a first, fully-closed position which blocks the gravity flow of fluid from the first chamber into the second chamoer ano a second, fully-open position in whicn tne gravity flow of fluid from the first cnamber mto tne second chamber is at a maximum flow, said valve stem being disposed in said valve Dooy for being manually set at any selected rotational position Detween said first and second positions so as to thereDy enable a user to selectively control tne gravity flow of fluid from said first chamber mto said second cnamber. Claim 21. The gravity flow IV fluid flow device as claimed in Claim 20, wherein at least a side wall region of said second chamber is constructed of a transparent material so that a rate of fluid dripping through said second chamber can be observed. Claim 22. The gravity flow IV fluid flow device as claimed in Claim 20, including first venting means lo¬ cated at an upper region of said first chamber above said preestablished fluid level for venting the first chamber to ambient surrounding pressure and second venting means located at a., upper region of said second chamber for venting the second chamber to ambient surrounding pres¬ sure. Claim 23. The gravity flow IV fluid flow device as claimed in Claim 20, including an indicator calibrated with respect to rotational positions of said valve stem for enabling a user to read fluid flow rates from the first chamber into the second cnamoer associated with different rotational positions of said valve stem. Claim 24. The gravity flow IV fluid flow device as claimed in Claim 20, including a second, free-floating float valve disposed in said second chamber for closing a fluid discharge opening m said lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestablished lower level ano closing a fluid mlet opening into the second chamoer when the fluid level m the second chamber reaches a preestab- lished upper level. Claim 25. A gravity flow IV fluid flow device with variable fluid head provision, said device comprising: a. a first chamber having an upper fluid in- let end region having a fluid flow orifice and a lower, fluid outlet region; b. means for enaoling a fluid flow connection between the fluid inlet end region of the first cnamber and a lower, discharge region of a preexisting, closed source of IV fluid so as to enable the gravity flow of fluid from said source through said fluid flow orifice into said first chamber; c. a free-floating float valve disposed in said first chamber for blocking said fluid flow orifice to stop the gravity flow of fluid from a connected source of IV fluid -mto the first chamber througn said fluid flow orifice when the fluid level m said first chamber is at a preestablished fluid level and for unblocking said orifice to permit the gravity flow of fluid from said connected source of IV fluid through said fluid flow orifice whenever the fluid level in said first chamber is lower than said preestablished fluid level; d. a second, drip chamber having an upper fluid inlet end region and a lower, fluid outlet end re- gion, said lower fluid outlet end region being configured for having attached thereto a conventional IV tube for providing fluid into a patient's body; and e. fluid flow regulating means connected in fluid flow relationship between the fluid outlet end re- gion of said first chamber and the fluid inlet end region of said second cnamoer for regulating the gravity flow of fluid from tne f_rst cnamber mto tne second chamber, said fluid flov; regulating means comprising a flexible fluid conou t connected in fluid flow relationship be- tween the outlet end region of the first cnamber and the fluid let end region of tne second chamber with a fixed orifice tnerem ano means for selectively controlling the vertical distance oetween said preestablished fluid level in said first chamoer and the fluid mlet region of the second chamoer. Claim 26. Tre gravity flow IV fluid flow device as claimed in Claim 25, wherein at least a side wall region of said second cnamber is constructed of a transparent material so that a rate of fluid dripping through said second chamber can oe observed. Claim 27. The gravity flow IV fluid flow device as claimed Claim 25, including first venting means lo- cated at an upper region of said first chamoer above said preestablisned fluid level for venting the first chamber to ambient surrounding pressure and second venting means located at an upper region of said second cnamber for venting the second chamber to ambient surrounding pres- sure. Claim 28. The gravity flow IV fluid flow device as claimed in Claim 25, including a second free-floating float valve disposed in said second chamber for closing a fluid discharge opening in said lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestablished lower level and closing a fluid mlet opening into the second chamber when the fluid level m tne second chamber reaches a preestab- lished upper level. Claim 29. A gravity flow fluid flow device with con¬ stant fluid head provision, said device comprising- a. a first, constant fluid head cnamber hav - mg an upper fluid let end region and a lower, fluid outlet region; b a second, drip chamoer havmg an upper fluid inlet end region and a lower, fluid outlet end re¬ gion, said lower fluid outlet end region being configured for having attached thereto a conventional discharge tube, said second chamber being aligned with said first chamber along a common longitudinal axis; c. fluid flow regulating means for regulating the gravity flow of fluid from the first chamber mto the second chamber, said fluid flow regulating means compris¬ ing means for selectively adjusting the relative axial position between said first and said second chambers; and d. means for enabling a fluid-flow connection between the fluid mlet end region of the first chamber and a lower, discharge region of a preexisting source of fluid that is open to ambient surrounding pressure through a collapsible container or a filtered vent; and e. fluid level control for causing, when said connecting means connects said first chamber to said pre- existing source of fluid for receiving a flow of fluid therefrom, a preestablished fluid level to be substan¬ tially maintained in said first chamber as the fluid level said connected source decreases, said fluid level control means including an orifice at the fluid m- let end region of said first chamber and a free-floating float valve disposed in said first chamber configured for blocking said orifice to stop a gravity flow of fluid through said orifice from said connected source when the fluid level in said first chamber is at said preestablished level and for floating downwardly and un- blocking said orifice to permit a gravity flow of fluid through said orifice from said connected source wnen the fluid level in said first chamber falls below said prees¬ tablished level ana until the fluid level returns to said preestablisned level whereby said valve floats upwardly ana again blocks off the flow of fluid through said ori¬ fice. Claim 30. The gravity flow fluid flow device as claimed in Claim 29, wherein said source of fluid is IV fluid. Claim 31. Tne gravity flow fluid flow device as claimed in Claim 29, wherein at least a side wall region of said second chamber is constructed of a transparent material so that a rate of fluid dripping through said second chamber can oe observed. Claim 32. The gravity flov; fluid flow device as claimed in Claim 29, including first venting means lo¬ cated at an upper region of said first chamber above said preestablished fluid level for venting the first cnamber to ambient surrounding pressure. Claim 33. The gravity flow fluid flow device as claimed in Claim 29, including second venting means lo¬ cated at an upper region of said second chamber for vent¬ ing the second chamber to ambient surrounding pressure. Claim 34. The gravity flow IV fluid flow device as claimed in Claim 29, including an indicator calibrated with respect to vertical positioning of said second cham¬ ber relative to said first chamber for enabling a user to read fluid flow rates from the first chamber into the second chamber associated with different relative verti¬ cal positions of said first and second cha oers. Claim 35. The gravity flow fluid flow device as claimed in Claim 29, mcludmg means disposed in said second chamber for closing said lower, fluid outlet end region when no fluid is gravity flowing through and out thereof. Claim 36. The gravity flow fluid flow device as claimed in Claim 35, wherein said closing means include a float valve having a closure region which closes a fluid discharge opening in said lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestablished lower level and closes a fluid in¬ let opening into the second chamber when the fluid level in the second chamber reaches a preestablished upper level . Claim 37. The gravity flow IV fluid flow device as claimed in Claim 29, including a scale caliϋrated with respect to relative axial movement between the first and second chambers for enabling a user to set a selected fluid flow rate from the first chamber into the second chamber. Claim 38. The gravity flow IV fluid flow device as claimed in Claim 29, including means disposed in said second chamber for closing a fluid discharge opening in said lower, fluid discharge outlet end region when the fluid level in the second chamber is below a preestab¬ lished lower level and closing a fluid inlet opening into the second chamber when the fluid level in the second chamber reaches a preestablished upper level. Claim 39. A constant fluid head gravity flow device with variable fluid head provision, said device compris ¬ ing : a a first cnamber having an upper fluid m- let end region having a fluid flow orifice and a lower, fluid outlet region; b means for enabling a fluiα flow connection between the fluid inlet end region of the first chamber and a lower, discharge region of a preexisting source of fluid so as to enable the gravity flow of fluid from said source through said fluid flow orifice into said first chamber, c. a free-floating float valve disposed in said first chamoer for blocking said fluid flow orifice to stop the gravity flow of fluid from a connected source of fluid into the first chamber through said fluid flow orifice v/hen the fluid level in said first chamber is at a preestablished fluid level and for unblocking said ori¬ fice to permit the gravity flow of fluid from said con- nected source of fluid through said fluid flow orifice whenever tne fluid level in said first cnamber is lower than said preestablished fluid level; d. a second, drip chamber having an upper fluid inlet end region and a lower, fluid outlet end re- gion, said lower fluid outlet end region being configured for having attached thereto a conventional tube for pro¬ viding fluid into a patient's body, said second chamber being axially aligned with said first chamber; and e. means enabling the relative axial movement between the first and second chambers so as to selec¬ tively vary the fluid flow rate through the device. Claim 40. The constant head fluid flow device as claimed m Claim 39, including means for frictionally locking the first and second chambers in any selected relative position therebetween.

Inventors: DARLING PHILLIP H JR, DARLING, PHILLIP, H., JR.
Applicants: DARLING PHILLIP H JR, DARLING, PHILLIP, H., JR.
Application year: 1996
Main classification: A61M5
IPC codes: A61M5