BACKGROUND OF THE INVENTION It is known in the art to provide intravenous delivery of fluids and medicaments to a subject. Intravenous therapy is generally carried out by feeding medicament together with or in the absence of saline solution from a bag or other supply source. The rate of delivery is generally controlled using a valve associated with a flow-monitoring device. The flow rate is commonly monitored in accordance with an observed droplet rate passing through a droplet-monitoring device.

Known droplet-monitoring devices have several drawbacks, including the following: the fluid flow rate is not readily observable at a glance; counting the droplet rate is both time consuming and not easily discernible; the device is required to be in a substantially stationary, vertical position, having the supply bags of medicament and saline suspended thereabove; and controlling an intravenous flow to a subject under emergency conditions outside of a hospital environment may prove problematic if not impossible using a droplet counter device.

In alternate health care environments, such as the home, the droplet- monitoring device requires more than minimal monitoring by a healthcare professional. In addition, in order to function properly, the droplet-monitoring device must be largely air-filled. This incurs an element of risk to the patient in so far as there is a risk that air will pass into the vein of the patient.

Furthermore, the accuracy and consistency of the droplet counting device is somewhat limited. There is a need in the art for a readily perceivable measuring device, which also facilitates accurate control of the feed rate of medicaments, most especially at very low rates. Low feed rates in this context are taken to be rates below about 40 milliliters per hour. There is a growing need for low feed rate

measurements, due to an increase in the use of high concentration medications having an elevated potency, having the effect of rendering the required feed rates generally at or below the accuracy limit of a droplet-counting device. In addition, with specific medicaments, therapeutic effectiveness is achieved only within a narrow dosage range, thus requiring an accurate control of the feed rate within a narrow range of tolerances. Below the requisite rate, the medicament may be ineffectual and above a specified upper limit may become toxic, thus rendering essential an accurate control of the feed rate.

An understanding of the state of the art may be obtained with reference to the following publications: Referring now to US 5,005, 604 to Aslanian on April 9, 1991 entitled"Flow control device for administration of intravenous fluids"there is disclosed a metering apparatus and system for controlling administration of fluids.

The apparatus includes a valve housing with a valve chamber. There is a rotatable valve body member positioned in the chamber and a variable cross-sectional area valve passageway either at the chamber or the valve. The effective valve passageway area and length between the inlet and outlet to the valve is adjustable to regulate flow by moving the valve body relative to the valve. Accessories can be selectively attached to the valve including a back-plate to facilitate single-handed operation. An optional cover plate may be secured to the back-plate to prevent patient tampering. The valve housing and internal valve members are fabricated from dissimilar hardness plastic materials to improve the sealing between these.

Referring now to US 5,267, 957 to Kriesel, et al. on December 7,1993, entitled"Closed drug delivery system"there is disclosed apparatus for controllably mixing components in a sterile, closed environment to produce a flowable substance and further for expelling the substance at a precisely controlled rate. This is particularly useful for medical applications and includes a dispenser with a stored energy element in the form of an elastic membrane. A coupling mechanism connects a drug vial to the dispenser for controlled sterile mixing of medicament within the drug vial with a diluent in the dispenser of the apparatus.

Referring now to US 5,499, 968 to Milijasevic, et al. on March 19,1996, entitled"Flow controllers for fluid infusion sets"there is disclosed an in-line flow controller for infusion of fluid into a patient. The set includes a reservoir of fluid

connected to a supply line having a discharge orifice. The fluid flow controller has a housing with a chamber therein, an inlet to and an outlet from the chamber, the housing adapted to receive flow restrictors having an orifice or orifices to control the rate of flow therethrough. The fluid is infused into a patient at a constant flow or within predetermined limits via the discharge orifice.

Referring now to US 5,840, 071 and US 6,176, 845 both to Kriesel, et al. on November 24,1998 and January 23,2001, respectively, entitled"Fluid delivery apparatus with flow indicator and vial fill"there is disclosed apparatus for accurately treating an ambulatory patient at specific rates over extended periods of time. The apparatus is of a compact, low profile, laminate construction and includes an elastic distendable membrane, and a chamber having a fluid outlet. Within the fluid chamber is a thin fluid permeable member, which controls the rate of fluid flow through the fluid outlet. The apparatus also includes a novel fluid flow indicator that provides a readily discernible visible indication of fluid flow through the apparatus. Also, the apparatus includes a fill assembly comprising a pre-filled vial that can be used to fill the fluid reservoir of the device with a selected medicinal fluid.

SUMMARY OF THE INVENTION The present invention aims to provide an accurate and consistent fluid flow monitoring apparatus for intravenous therapy under circumstances and in environments that include hospitals, places of alternate healthcare, emergency events in the field and in circumstances where stability and consistency are generally problematic or nonexistent. Furthermore, the present invention seeks to provide monitoring of intravenous therapy with minimal participation by healthcare professionals, providing a readily observed indication of the flow status.

According to a preferred embodiment of the present invention, there is provided apparatus for monitoring fluid flow including a housing having an at least partially optically transparent side-wall, integrally formed with and disposed between first and second housing end walls; and a fluid inlet and outlet formed respectively in the first and second housing end walls. There is further included an elastic displacement member having a preselected flow orifice therethrough, and

fixably disposed within the housing in fluid flow communication with the fluid inlet and outlet, operative to be displaced in accordance with a fluid flow rate therethrough. Also included is a flow rate indicator member, formed integrally with the elastic displacement member, for providing a visual indication of the fluid flow therethrough and a calibrated scale axially disposed on the side-wall in visual proximity to the indicator member, for providing a visual indication of the rate of a fluid flow through the outlet.

Also in accordance with a preferred embodiment of the present invention, the intravenous apparatus includes one or more supply members of intravenous fluid; a supply tube apparatus arranged in fluid flow communication with the one or more supply members including one or more flow regulating valves; an intravenous insertion member connected in flow communication with the supply tube apparatus; and one or more fluid flow monitoring apparatus disposed in the supply tube apparatus and in flow communication therewith for monitoring the fluid flow rate therethrough. The monitoring apparatus includes a housing having an at least partially optically transparent side-wall, integrally formed with and disposed between first and second housing end walls and a fluid inlet and outlet formed respectively in the first and second housing end walls. There is further included in the monitoring apparatus an elastic displacement member having a preselected flow orifice therethrough, and fixably disposed within the housing in fluid flow communication with the fluid inlet and outlet, operative to be displaced in accordance with a fluid flow rate therethrough. Also included is a flow rate indicator member, formed integrally with the elastic displacement member, for providing a visual indication of the fluid flow therethrough and a calibrated scale axially disposed on the side-wall in visual proximity to the indicator member, for providing a visual indication of the rate of a fluid flow through the outlet.

According to a first embodiment of the present invention, apparatus for monitoring fluid flow includes the side-wall having a generally cylindrical configuration.

According to a second embodiment of the present invention, the elastic displacement member is a generally cylindrical member having integral first and second end walls, at least a portion of the cylindrical member having an integral

elastic bellows configuration, the first end wall having an inlet therethrough and the second end wall having a preselected flow orifice therethrough, such that the elastic bellows expands in a predetermined manner in response to a rate of fluid flow therethrough causing the flow rate indicator member to be displaced in accordance with the fluid flow rate therethrough.

According to a variation of the second embodiment of the present invention, the generally cylindrical side-wall has an elastic membrane configuration.

According to a third embodiment of the present invention, the fluid flow monitoring apparatus includes an elastic displacement member fixably disposed within the housing, which is a flexible tube having a helical configuration formed with at least one coil therein such that a variation in flow therethrough causes elastic displacement of the at least one coil; an inlet in flow communication with the housing inlet; and an outlet having a preselected flow orifice formed therein with an indicator member fixably attached externally thereto for providing a visual determination of the displacement of the flexible tube and thereby providing a visual indication of the fluid flow rate on the calibrated scale.

According to a fourth embodiment of the present invention, the side-wall is formed of elastically distortable material for providing a fluid flow to bypass the elastic displacement member and thereby to purge air from the housing.

According to a fifth embodiment of the present invention, the side-wall is elastically deformable and there is formed in the elastic displacement member, a selectably openable bypass aperture, operative to permit a variable fluid flow therethrough when open, so as to purge air from the housing.

According to a sixth embodiment of the present invention, the inlet includes a bypass inlet in operative association with a valve member for providing a fluid flow to bypass the elastic displacement member and thereby to purge air from the housing.

According to a seventh embodiment of the present invention, the outlet includes purging apparatus for drawing fluid into the housing, thereby to purge air from the housing. According to a variation of the seventh embodiment of the present invention, the purging apparatus includes a piston element disposed within

the housing fixably attached to an outlet, which is slidably disposed in the second end wall.

According to a ninth embodiment of the present invention, the elastic displacement member includes apparatus for providing a remote signal indicative of the displacement of the flow rate indicator member and thereby of the fluid flow therethrough.

According to a tenth embodiment of the present invention, the housing includes a side-wall having a generally quadrant configuration, integrally formed with and disposed between at least partially optically transparent first and second housing end walls; a fluid inlet and outlet formed in the side-wall; a displacement member hingably and elastically disposed within the housing in fluid flow communication with the fluid inlet and outlet, operative to be rotationally displaced in accordance with the fluid flow rate therethrough; a flow rate indicator member, formed integrally with the displacement member, for providing a visual indication of the fluid flow therethrough; and a calibrated scale axially disposed on at least one of the end walls in visual proximity to the displacement member, for providing a visual determination of the rotational displacement of the displacement member and thereby providing a visual indication of a fluid flow rate fluid therethrough.

According to an eleventh embodiment of the present invention, the monitoring apparatus is pre-filled with a preselected fluid for eliminating the need to purge air from the apparatus prior to use.

Furthermore, there is provided a method for operating an intravenous therapy apparatus including one or more fluid flow monitoring apparatus disposed in the intravenous therapy apparatus and in flow communication therewith for monitoring fluid flow rate therethrough. The monitoring apparatus includes a housing having an at least partially optically transparent side-wall, integrally formed with and disposed between first and second housing end walls, and a fluid inlet and outlet formed respectively in the first and second housing end walls. The monitoring apparatus further includes an elastic displacement member having a preselected flow orifice therethrough, and fixably disposed within the housing in flow communication with the fluid inlet and outlet, operative to be displaced in accordance with the fluid flow rate therethrough. Also included is a flow rate

indicator member, formed integrally with the elastic displacement member, for providing a visual indication of the fluid flow therethrough ; and a calibrated scale axially disposed on the side-wall in visual proximity to the indicator member, for providing a visual indication of the rate of a fluid flow through the outlet.

The method includes the steps of: purging air from a supply tube apparatus, the at least one fluid flow monitoring apparatus and an intravenous insertion member by causing intravenous fluid to flow from an at least one supply member therethrough; inserting the intravenous insertion member into a vein of a subject; and adjusting an at least one flow regulating valve for providing a preselected flow of fluid as indicated by the at least one fluid flow monitoring apparatus into the vein.

In accordance with a twelfth embodiment of the present invention, the method steps include an additional step of purging air from the one or more flow monitoring apparatus following the first purging step.

In accordance with a thirteenth embodiment of the present invention, the housing includes a generally cylindrical centralizing shaft fixably formed in the first housing end wall and disposed co-axially within the housing such that the centralizing shaft projects through the preselected flow orifice thereby to maintain the elastic displacement member substantially co-axial with the housing.

In accordance with a fourteenth embodiment of the present invention, the centralizing shaft includes a first proximal portion formed adjacent to the first housing end wall, the first proximal portion having a first preselected external diameter greater than diameter of the preselected flow orifice. A second distal portion has a second preselected external diameter smaller than the preselected flow orifice, forming thereby a step between the first and second portions, such that the preselected flow orifice of the elastic displacement member is caused to retract against the step when intravenous fluid ceases to flow through the apparatus, thereby to prevent back-flow of fluid through the apparatus.

In accordance with a fifteenth embodiment of the present invention, the second portion of the centralizing shaft has a distally conical formed taper thereby to form a variable cross-sectional area flow annulus disposed between the preselected flow orifice and the distally conical formed taper.

In accordance with a sixteenth embodiment of the present invention, the second portion of the centralizing shaft has a distally step-formed taper thereby to provide a flow annulus of variable cross-sectional area disposed between the preselected flow orifice and the distally conical step-formed taper.

In accordance with a seventeenth embodiment of the present invention, a distal end portion of the second portion of the centering shaft is formed having an external diameter substantially smaller than the preselected flow orifice of the elastic displacement member, so as to provide a substantially increased flow area annulus disposed between the preselected flow orifice and the distal end portion, thereby to facilitate a substantially higher rate of flow of liquid therethrough.

In accordance with a seventeenth embodiment of the present invention, the elastic displacement member includes one or more preselected flow orifices therethrough. The elastic displacement member is movably disposed within the housing in fluid flow communication with the fluid inlet and outlet, operative to be axially displaced in accordance with a fluid flow rate therethrough. A generally cylindrical centralizing shaft is fixably formed in the first housing end wall and disposed co-axially within the housing such that the centralizing shaft projects through a centering orifice formed co-axially in the displacement member, thereby to maintain the elastic displacement member co-axially within the housing.

In accordance with a seventeenth embodiment of the present invention, the elastic displacement member is formed as a generally cylindrical shaped piston including a double-acting piston seal to provide a fluid flow seal between the piston and the side-wall. The co-axial centering orifice formed therein, provides uniform axial travel of the piston within the housing and an elastic helix which provides compressible resistance to movement of the piston to flow of liquid through the housing.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and its features and advantages will become apparent to those skilled in the art by reference to the ensuing description, taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates a schematic view of a fluid flow rate monitoring apparatus with no fluid flowing therethrough; Figure 2 illustrates a schematic view of a fluid flow rate monitoring apparatus with fluid flowing at a preselected rate therethrough; Figure 3 illustrates a schematic view of an intravenous apparatus including a fluid flow monitoring apparatus in accordance with a preferred embodiment of the present invention; Figure 4 illustrates a schematic view of a helical-type fluid flow rate monitoring apparatus without fluid flow therethrough; Figure 5 illustrates a schematic view of a helical-type fluid flow rate monitoring apparatus with fluid flowing therethrough; Figure 6 illustrates a schematic view of a Bourdon-type fluid flow rate monitoring apparatus without fluid flow therethrough; Figure 7 illustrates a schematic view of a Bourdon-type fluid flow rate monitoring apparatus with fluid flowing therethrough; Figure 8 illustrates a schematic view of a closed bellows-type fluid flow rate monitoring apparatus; Figure 9 illustrates a schematic view of a bellows-type fluid flow rate monitoring apparatus without fluid flow therethrough; Figure 10 illustrates a schematic view of a bellows-type fluid flow rate monitoring apparatus with fluid flow therethrough; Figure 11 illustrates a schematic view of a quadrant-type fluid flow rate monitoring apparatus without fluid flow therethrough; Figure 12 illustrates a schematic view of a quadrant-type fluid flow rate monitoring apparatus with partial fluid flow therethrough; Figure 13 illustrates a schematic view of a quadrant-type fluid flow rate monitoring apparatus with full fluid flow therethrough; Figure 14 illustrates a schematic view of a fluid flow rate monitoring apparatus having an elastically distortable cylindrical side-wall, prior to filling with fluid;

Figure 15 illustrates a schematic view of a fluid flow rate monitoring apparatus having an elastically distortable cylindrical side-wall distorted to facilitate filling with fluid; Figure 16 illustrates a schematic view of a fluid flow rate monitoring apparatus having a bypass inlet to facilitate filling with fluid; Figure 17 illustrates a schematic view of a fluid flow rate monitoring apparatus having a bypass inlet with fluid flowing therethrough; Figure 18 illustrates a schematic view of a fluid flow rate monitoring apparatus having a moveable purging piston, before purging; Figure 19 illustrates a schematic view of a fluid flow rate monitoring apparatus having a moveable purging piston, after purging; Figure 20 illustrates a schematic view of a fluid flow rate monitoring apparatus having a moveable purging piston, in operation with fluid flowing; Figures 21A, 21B, 21C, 22A and 22B illustrate a monitoring apparatus having an elastically distortable cylindrical side-wall and an elastic displacement member having a selectably openable bypass aperture in accordance with an alternative embodiment of the present invention; Figures 23 and 24, illustrate schematic views of a monitoring apparatus, without and with, respectively, fluid flowing therethrough, the apparatus including a sensing element formed or attached to an elastic displacement member; Figure 25 illustrates a schematic view of a monitoring apparatus, without fluid flowing therethrough, the apparatus including a centralizing co-axial shaft; Figures 26 and 27, illustrate schematic views of a monitoring apparatus, with fluid flowing therethrough, the apparatus including a centralizing co-axial shaft; and Figure 28 illustrates a cross-sectional schematic view of a monitoring apparatus including a co-axial piston flow indicator.

DETAILED DESCRIPTION OF THE INVENTION Whilst the details that follow hereinbelow generally relate to monitoring the flow rate of fluids in intravenous therapy, it will be apparent to persons skilled in the art, that embodiments of the present invention are applicable to many fields and applications. Such applications include those requiring sensitive and accurate fluid flow monitoring, especially at low flow rates. Applications include laboratory work, chemical processing and manufacturing, and biochemical manufacturing, to mention a few. Fluids to be monitored include liquids, gases and corrosive or toxic fluids.

There is a need in the art for apparatus, which accurately monitors intravenous therapy. This is particularly applicable with patients in an emergency situation, including outside of a hospital environment. Further, it is advantageous to monitor intravenous therapy with a minimal of professional participation or supervision. The presently generally utilized droplet monitoring flow device cannot effectively function without the presence of air in the tubing, which can prove problematic in treatment under non-ideal circumstances.

According to embodiments of the present invention, as shown and described below in conjunction with Figures 1-24, the flow monitoring apparatus of the present invention is compact, inexpensive and can operate in any desired orientation. Furthermore, visual indication of the flow rate is readily discernible and operates without the necessity of air in the system. In addition, the flow monitoring apparatus can be used with minimal professional assistance, which is particularly beneficial in an alternate health care environment, such as the home or under virtually any emergency situation.

With reference to Figures 1 and 2, there is seen, according to a preferred embodiment of the present invention, a fluid flow rate monitoring apparatus generally referenced 10. Monitoring apparatus 10 includes a housing generally referenced 12 having an at least partially optically transparent generally cylindrical side-wall referenced 14 integrally formed with and disposed between first and second housing end walls referenced 16 and 18, respectively. A fluid inlet

referenced 20, and a fluid outlet referenced 22, are formed respectively in first and second housing end walls 16 and 18.

In accordance with a preferred embodiment of the present invention, an elastic displacement member referenced generally 24 has a generally cylindrical side-wall referenced 26 formed in an elastic bellows configuration, integrally formed with and disposed between first and second displacement member end walls referenced 28 and 30. First displacement member end wall 28 has a fluid inlet referenced 32 formed therein and is fixably attached to first cylindrical housing end wall 16. Second displacement member end wall 30 has a flow orifice referenced 34, of preselected size, formed therein to permit fluid flow therethrough. With no fluid passing through monitoring apparatus 10, displacement member 24 assumes a no- flow position as indicated in Figure 1. End wall 30 functions as a flow rate indicator member, as will be appreciated from the description hereinbelow.

When fluid enters through inlet 20 of flow monitoring apparatus 10 from a fluid supply (not shown), a fluid flow force is applied to end wall 30, causing elastic bellows side-wall 26 to extend substantially linearly in the direction of flow, as seen in Figure 2. The extent of the extension of end wall 30 which, as mentioned above, functions also as a flow rate indicator, is substantially in proportion to the rate of fluid flow through orifice 34, the fluid flow eventually exiting through outlet 22. The actual flow rate may be observed with reference to the position of end wall 30, relative to a calibrated scale referenced 36, disposed axially along side-wall 14 in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic bellows side-wall 26 contracts, causing a corresponding retraction of end member 30.

In accordance with embodiments of the present invention, the range over which the rate of flow is to be monitored is determined by preselecting the size of orifice 34. Specifically, the operable flow range is a function of the orifice size and the elasticity of side-wall 26.

Monitoring apparatus 10 can be used for continuous infusion of antibiotics, hormones, steroids, blood-clotting agents, analgesics, saline solution and other medicinal agents. Similarly, monitoring apparatus 10 can be used for intravenous chemotherapy. Accurate delivery of fluids, at flow rates as low as 40 ml/hour. or

less, at precise discernable rates and over extended periods of time, with minimal professional participation is feasible in accordance with embodiments of the present invention. Also, monitoring apparatus 10 need not be kept in an upright position and, therefore, is operable at any angle and in any position relative to the subject. It is ideal for emergency use even outside of a hospital environment, operable with or without air being completely purged, that is, filled or partly filled with liquid.

In accordance with a further embodiment of the present invention and referring now to Figure 3, there is seen a schematic view of an intravenous apparatus referenced generally 50. Apparatus 50 includes flexible tubing referenced 52 interconnecting one or more bags referenced 54 of medicament, saline solution or nutrients, supported in a position generally higher than the patient to facilitate flow by gravity from the bag to the patient. Operatively connected to each bag 54 requiring a controlled flow rate therefrom is a fluid flow monitoring apparatus referenced 56 in operative association with a valve referenced 58, and connected to an intravenous needle/cannula unit referenced 60 for introducing medicament, saline solution or nutrients into a vein (not shown) of a patient. By way of example, flow monitoring apparatus 56 can be comfortably and conveniently removably affixed to the clothing or taped to the body of the patient.

Further, when using the auto-infusion bag, which is the subject of Israel Patent Application Number 138766, application date 28/9/2000, entitled "CONSTANT PRESSURE APPARATUS FOR THE ADMINISTRATION OF FLUIDS INTRAVENOUSLY, "there is no need for any part of an intravenous apparatus to be suspended above the subject.

In accordance with alternative embodiments of the present invention which utilize an elastic displacement member disposed in a housing, fluid flowing through or past the displacement member, there are alternative flow monitors disclosed herein below.

Referring now to Figures 4 and 5, there is seen a helical-type fluid flow rate monitoring apparatus generally referenced 70. Fluid entering inlet, referenced 72, passes through a helical-formed elastic tube referenced 74 and exits tube 74 through an orifice, of preselected size, referenced 78 formed in end member

referenced 79 of tube 74. Tube 74 is disposed within a generally cylindrical housing referenced 76. Fluid emanating from orifice 78 exits housing 76 through an outlet referenced 80. The extent of the extension of tube end member 79, which, like end wall 30 of Figures 1 and 2, functions also as a flow rate indicator, is substantially in proportion to the rate of fluid flow through orifice 78, the fluid flow eventually exiting through outlet 80. The actual flow rate may be observed with reference to the position of end member 79, relative to a calibrated scale referenced 82, disposed axially along side-wall referenced 84 in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic tube 74 contracts, causing a corresponding retraction of end member 79.

In accordance with a further embodiment of the present invention, there is disclosed an elastic displacement member, similar to a Bourdon pressure gauge but formed to indicate flow rate therethrough. Referring now to Figures 6 and 7, there is seen a schematic view of a Bourdon-type fluid flow rate monitoring apparatus generally referenced 100. Apparatus 100 includes one or more coils of elastic tubing referenced 102 disposed in a generally cylindrical housing generally referenced 104, having a front face referenced 106 that is optically transparent and a rear face (not shown). Fluid entering inlet, referenced 108 passes through elastic tube displacement member 102 and exits through an orifice referenced 110, of preselected size, and subsequently exits housing 104 through an outlet referenced 112. In Figure 6 elastic tube 102 is seen in a rest position without fluid flowing therethrough. When fluid flows into inlet 108 through elastic tube displacement member 102 and exits through orifice 110, elastic tube 102 is caused to expand.

The extent of the resultant displacement of tube indicator pointer referenced 114, disposed at the end of tube 102, the pointer also functioning as a flow rate indicator, is substantially in proportion to the rate of fluid flow through orifice 110, the fluid flow eventually exiting through outlet 112. The actual flow rate may be observed with reference to the position of indicator pointer 114, relative to a calibrated scale referenced 116, disposed on either front face 106 or the rear face (not shown) in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic tube 102 contracts, causing a corresponding retraction of indicator pointer 114.

In accordance with an alternative embodiment of the present invention, an elastic displacement member in a configuration of a bellows-type fluid flow rate monitoring apparatus is disclosed. Referring now to Figures 8,9 and 10, there is seen a bellows-type fluid flow rate monitoring apparatus referenced generally 130.

This alternative embodiment includes an important feature, substantially facilitating the avoidance of the presence of air within a bellows housing generally referenced 132. Housing 132 includes a first and a second hinged end member referenced 134 and 136, respectively, having a hinge apparatus referenced 138 therebetween. Disposed between end members 134 and 136 there is an optically transparent bellows side-wall referenced 140 which is seen in a closed configuration in Figure 8 and in an open configuration in Figures 9 and 10.

Disposed in side-wall 140 is a calibrated flow indicator scale referenced 142.

Formed in first hinged member 134 is a fluid inlet referenced 150 and formed in second hinged member 136 is an outlet referenced 152. Disposed within housing 132 is an elastic displacement member referenced 148 having a closed bellows configuration fixably attached to first end member 134 and in flow communication with inlet referenced 150 and outlet 152. Elastic displacement member 148 has an orifice referenced 154, of preselected size, formed in an end surface referenced 156 thereof. When second hinged member 136 is opened relative to first hinged member 134, as seen in Figure 9, a suction is caused within housing 132 thereby drawing fluid through inlet 150 into housing 132 and hence avoiding the need to purge air from housing 132 prior to use. As seen in Figure 10, fluid flowing into inlet 150 and exiting through orifice 154 and outlet 152, causes elastic displacement member 148 to expand. The extent of the resultant displacement of end surface 156, which functions also as a flow rate indicator, is substantially in proportion to the rate of fluid flow through orifice 154, the fluid flow eventually exiting through outlet 152.

The actual flow rate may be observed with reference to the position of end surface 156, relative to calibrated scale 142 in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic displacement bellows member 148 contracts, causing a corresponding retraction of end surface 156.

It will be appreciated by persons skilled in the art that the bellows-type apparatus 130 disclosed hereinabove provides a means for eliminating the need to purge air from housing 132 prior to use. Further embodiments of the present

invention disclosed hereinbelow indicate additional features for elimination of air from the flow monitoring apparatus in relation to Figures 14-22B.

In accordance with another embodiment of the present invention, the concept of an elastic displacement member is further disclosed as a quadrant-type fluid flow rate monitoring apparatus. Referring now to Figure 11,12 and 13, there is seen a quadrant-type fluid flow rate monitoring apparatus generally referenced 170.

Apparatus 170 includes a housing referenced 172 having a generally quadrant- shaped cross-section referenced 174 bounded by first and second walls referenced 176 and 178 respectively meeting at a junction referenced 180 and having an optically transparent first end wall referenced 182 and a second end wall (not shown). There is a calibrated scale referenced 184 disposed on first end wall 182 or on second end wall. Elastic displacement member referenced 186 is hingably and elastically attached by means of a hinge, referenced 188 disposed at junction 180, to enable displacement member 186 to elastically rotate about hinge 188. Elastic displacement member 186 is in fluid flow communication with inlet referenced 190 and outlet 192 such that displacement member is caused to rotate from a no-flow position, as seen in Figure 11, by fluid entering inlet 190 flowing between displacement member 186 and housing 172 and exiting apparatus 170 through outlet 192. As seen in Figure 12, displacement member 186 is elastically rotationally displaced. The extent of the resultant displacement of displacement member 186, which functions also as a flow rate indicator, is substantially in proportion to the rate of fluid flowing between displacement member 186 and housing 172 and exiting apparatus 170 through outlet 192. The actual flow rate may be observed with reference to the position of displacement member 186, relative to a calibrated scale referenced 184, disposed on either front face 182 or rear face (not shown) in visual proximity thereto. In response to a reduction or cessation of the fluid flow, displacement member 186 retracts.

In order to expel all the air from an intravenous apparatus including a flow monitoring apparatus, in accordance with the embodiments of the present invention, it is necessary to cause fluid to purge through the entire apparatus. Because orifice 34 (for example, as indicated in Figure 1-2) is relatively small, such a purging process may be relatively slow. In accordance with an additional embodiment of the present invention, flow-monitoring apparatus is supplied in a pre-filled condition,

utilizing a suitable, innocuous liquid such as, for example, normal saline solution.

This eliminates the necessity of purging the flow monitoring apparatus.

Alternatively, purging of the air, in accordance with alternative embodiments of the present invention, can be accelerated. Referring now to Figures 14 and 15, there is seen a fluid flow rate monitoring apparatus generally referenced 200, having an elastically distortable cylindrical side-wall referenced 202 and a displacement member referenced 208 selectively supported by side-wall 202. To increase the flow through apparatus 200, as seen in Figure 15, side-wall 202 is squeezed to cause a distortion thereto as indicated by arrows referenced 204. This causes fluid, entering monitoring apparatus 200, to bypass orifice 206, formed in elastic displacement member 208, instead of passing solely therethrough.

According to one other embodiment of the present invention, there is seen, in Figures 16-17, a fluid flow rate monitoring apparatus generally referenced 220, generally constructed as monitoring apparatus 10 (as shown in Figures 1 and 2).

Apparatus 220, however, has a valve referenced 222 disposed in a bypass inlet referenced 224 to facilitate filling housing referenced 226 with fluid as seen in Figure 16. There is seen in Figure 17, apparatus 220 having fluid flowing therethrough with elastic displacement member referenced 228 indicating the rate of flow on calibrated scale referenced 230.

Referring now to Figures 18-20, there is seen, a fluid flow rate monitoring apparatus referenced 250 having a moveable purging piston referenced 252 fixably attached to an outlet referenced 254, which is slidably disposed in an orifice referenced 258 formed in an end wall referenced 256 of a housing referenced 260.

There is seen in Figure 18, piston 252 in an initial depressed position. In order to draw liquid into inlet referenced 262, as seen in Figure 19, piston 252 is withdrawn by pulling outlet 254 in the direction indicated by arrow 264, thereby filling housing 260 with fluid. There is further seen in Figure 20, apparatus 250 in operation with fluid flow therethrough with elastic displacement member referenced 266 indicating the rate of flow on calibrated scale referenced 268.

In accordance with an alternative embodiment of the present invention, there is an additional means for facilitating the purging of air from a monitoring apparatus. Referring now to Figure 21A, there is seen a fluid flow rate monitoring

apparatus referenced generally 270 having an elastically distortable cylindrical side-wall referenced 272 and, disposed therein an elastic displacement member referenced 274 having a bypass aperture referenced 276 formed in inlet end wall referenced 277. In Figures 21B and 21C there is seen an enlarged view of inlet end wall 277 of elastic displacement member 274, indicating bypass aperture 276. By selectively squeezing to distort side-wall 272, there is caused a distortion of elastic displacement member 274, which causes bypass aperture 276 to elastically open as seen in Figure 21C. This facilitates rapid fluid flow therethrough thereby to purge air from monitoring apparatus 270.

Referring now to Figures 22A and 22B there is seen an alternative bypass aperture referenced 278 formed circumferentially in end wall 277 of elastic displacement member 274. When side-wall 272 is selectively squeezed, bypass aperture 278 opens as elastic displacement member 274 is distorted, as seen in Figure 22B. It will be appreciated by persons skilled in the art that there are alternative positions and shapes for a bypass aperture, not limited to the alternatives indicated in Figures 21A-22B.

According to an alternative embodiment of the present invention, a fluid flow rate monitoring apparatus produces a remote signal in accordance with the flow therethrough. Referring now to Figures 23 and 24, there is seen a monitoring apparatus referenced generally 280, which is substantially similar to monitoring apparatus 10 shown in Figures 1 and 2. Apparatus 280, however, includes a sensing element referenced 282 formed or attached to elastic displacement member referenced 284. A suitable monitoring apparatus (not shown) senses the displacement or position of sensing element 282 and elastic displacement member 284. Displacement of elastic displacement member 284 and of sensing element 282 caused by fluid flow through apparatus 280 provides a remote signal indicating the position of sensing element 282 and thereby indicating the rate of flow through monitoring apparatus 280. There is seen in Figure 23 the position of displacement member 284 and sensing element 282 in the absence of flow and, in Figure 24, when fluid is passing through monitoring apparatus 280.

Referring now to Figures 25,26 and 27, there is seen, according to another preferred embodiment of the present invention, a fluid flow rate monitoring

apparatus, generally referenced 300, which includes a centralizing co-axial shaft, referenced generally 302. Figure 25 illustrates monitoring apparatus 300 without fluid flowing therethrough. Figure 26 illustrates monitoring apparatus 300, with fluid flowing therethrough at a rate of flow consistent with normal infusion rates.

Monitoring apparatus seen in Figure 27 indicates a substantially high rate of infusion.

Monitoring apparatus 300 includes a housing generally referenced 312 having an at least partially optically transparent generally cylindrical side-wall referenced 314 integrally formed with and disposed between first and second housing end walls referenced 316 and 318, respectively. A fluid inlet referenced 320, and a fluid outlet referenced 322, are formed respectively in first and second housing end walls 316 and 318.

In accordance with this embodiment of the present invention, an elastic displacement member referenced generally 324 has a generally cylindrical side-wall referenced 326 formed in an elastic bellows configuration, integrally formed with an end wall referenced 330.

Integrally formed within proximal first housing end wall 316 and with fluid inlet 320, centering shaft 302 includes a fluid inlet orifice referenced 332 formed proximally therein in fluid flow communication with fluid inlet 320. Centering shaft 302 is fixably attached to first cylindrical housing end wall 316. Second displacement member end wall 330 has a flow orifice referenced 334, of preselected size, formed therein to permit fluid flow through an annulus formed between flow orifice 334 and centering shaft 302. With no fluid passing through monitoring apparatus 300, displacement member 324 assumes a no-flow proximal position as indicated in Figure 25. End wall 330 functions as a flow rate indicator member, as will be appreciated from the description hereinbelow.

When fluid enters through proximal inlet 320 of flow monitoring apparatus 300 from a fluid supply (not shown), a fluid flow force is applied to end wall 330, causing elastic bellows side-wall 326 to extend substantially linearly in the direction of flow, as seen in Figures 26 and 27. The extent of the extension of end wall 330 which, as mentioned above, functions also as a flow rate indicator, is substantially in proportion to the rate of fluid flow through flow orifice 334, the

fluid flow eventually exiting through outlet 322 at the distal end of monitoring apparatus 300. The actual flow rate may be observed with reference to the position of end wall 330, relative to a calibrated scale referenced 336, disposed axially along side-wall 314 in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic bellows side-wall 326 contracts proximally, causing a corresponding retraction of end member 330, as seen in Figure 25.

In accordance with embodiments of the present invention, the range over which the rate of flow is to be monitored is determined by preselecting the size of orifice 334 relative to the diameter of centering shaft 302. Specifically, the operable flow range is a function of the orifice size and the elasticity of side-wall 326.

In accordance with a further embodiment of the present invention, centering shaft 302 is formed as a simple cylindrical shaft (not shown) or formed having various features in accordance with additional embodiments of the present invention.

Such an additional embodiment provides for centering shaft 302 formed having a proximal cylindrical first portion, referenced 337 with a first portion external diameter and having a second portion referenced 338 formed having an external diameter smaller than the diameter of first proximal portion 337. The differential between the first portion diameter and second portion diameter forms an intervening step referenced 340 between first and second portions 337 and 338 respectively. When fluid ceases to flow through monitoring apparatus 300, flow orifice 334 of elastic displacement member 324 retracts proximally and is caused to be pushed against step 340, thereby to prevent back-flow of venous fluid through monitoring apparatus 300.

In accordance with an added embodiment of the present invention, centering shaft 302 includes second portion 338 formed having a cylindrical or distally tapering cone-shape, thereby to provide a flow annulus of variable cross-sectional area disposed between flow orifice 334 and distally conical formed taper of second portion 338. An alternative embodiment of the present invention provides second portion 338 formed as a tapering series of reducing steps (not shown). The tapering

conical or stepped shape of second portion 338 facilitates specific control of the flow of fluid through monitoring apparatus 300.

In accordance with one other embodiment of the present invention, centering shaft 302 distal end portion referenced 342 of second portion 338 is formed having an external diameter substantially smaller than flow orifice 334. This provides a substantially increased flow annulus disposed between flow orifice 334 and distal end portion 342, thereby to facilitate a substantially higher rate of flow of liquid therethrough.

Referring now to Figure 28, there is seen, according to a preferred embodiment of the present invention, a cross-sectional schematic view of a monitoring apparatus referenced generally 400, including a co-axial piston flow indicator generally referenced 404. Monitoring apparatus 400 includes a housing generally referenced 412 having an at least partially optically transparent generally cylindrical side-wall referenced 414 integrally formed with and disposed between first and second housing end walls referenced 416 and 418, respectively. A fluid inlet referenced 420, and a fluid outlet referenced 422, are formed respectively in first and second housing end walls 416 and 418.

In accordance with a preferred embodiment of the present invention, an elastic displacement member referenced generally 424 has one or more flow orifices referenced 434, of preselected size, formed therein to permit fluid flow therethrough, axially movably disposed within housing 412 in fluid flow communication with fluid inlet 420 and outlet 422, operative to be displaced in accordance with a fluid flow rate therethrough. Elastic displacement member 424 is formed as a generally cylindrical shaped piston referenced 426 including a double- acting piston seal 428, sealing against cylindrical side-wall 414.

Piston 426 has a co-axial centering orifice referenced 430 formed therein, so as to provide uniform axial travel within housing 412 and a generally cylindrical centralizing shaft referenced 432 fixably formed in first housing end wall 416 and disposed co-axially within housing 412 such that centralizing shaft 432 projects through co-axial orifice 430, thereby to maintain elastic displacement member 424 co-axial with housing 412. An elastic helix referenced 436 to provide compressible resistance to movement of piston 426 to flow of liquid through housing 412, is

disposed distally to piston 426. With no fluid passing through monitoring apparatus 400, displacement member 424 assumes a no-flow position (not shown) within the proximal end of housing 412. Piston 426 functions as a flow rate indicator member, as will be appreciated from the description hereinbelow.

When fluid enters through inlet 420 of flow monitoring apparatus 400 from a fluid supply (not shown), a fluid flow force is applied to piston 426, causing piston 426 to displace linearly in the direction of flow against the compressive resistance of a helical spring 436 disposed between distal face of piston 426 and spring support member referenced 438. The extent of the displacement of piston 426, as mentioned above, functions as a flow rate indicator, substantially in proportion to the rate of fluid flow through one or more orifices 434, the fluid flow eventually exiting through outlet 422. The actual flow rate may be observed with reference to the position of piston 426, relative to a calibrated scale (not shown), disposed axially along side-wall 414 in visual proximity thereto. In response to a reduction or cessation of the fluid flow, elastic helical spring 436 expands, causing a corresponding retraction of piston 426.

In accordance with embodiments of the present invention, the range over which the rate of flow is to be monitored is determined by preselecting the size and number of orifices 434. Specifically, the operable flow range is a function of the orifice size and the elasticity of helical spring 436.

It will be appreciated by persons skilled in the art that the present invention is not limited by the drawings and description hereinabove presented. Rather, the invention is defined solely by the claims that follow.