Method and apparatus for controlling the dispensing of fluid

We claim:

1. A disposable metering unit for use in controlling the intravenous administration of a fluid to a patient, comprising:

inlet conduit means for delivering fluid at a hydrostatic pressure from a source of fluid; metering means for receiving a predetermined increment of fluid from the conduit means and for emptying the predetermined increment of fluid by the suction of gravity flow without adding substantial pressure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means being capable of being moved at the hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm means, and a second position in which the diaphragm is in contact with the other of said opposed inner walls of the metering chamber with substantially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering means may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means; and

outlet conduit means communicating with the metering means for receiving said increments wherein gravity suction flow takes place to empty the metering means when the outlet means is opened, both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communicating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in contact in its second position, to facilitate free flow of air into and out of said metering chamber as said diaphragm means moves between its first and second positions;

and means for permitting the alternative and sequential valving of fluid through said inlet conduit means and outlet conduit means.

2. The disposable metering unit of claim 1 in which a projection is positioned on the inner wall of each inlet and outlet conduit means in opposed relation to apertures in said walls to serve as part of said valve means.

3. The metering unit of claim 1 in which the unit includes a rigid body portion and a cover portion with a cavity formed in the unit to provide the metering chamber, the size of the cavity determining the capacity for the predetermined increments of fluid.

4. The metering unit of claim 1 in which the movable diaphragm means is resilient to conform to the shape of the cavity.

5. The metering unit of claim 1 in which the unit includes a rigid body portion and a cover portion with an arcuate-shaped cavity formed in the body portion and a communicating arcuate-shaped cavity formed in the cover portion to provide the metering chamber.

6. The metering unit of claim 5 in which said diaphragm has an arcuate-shaped portion which conforms to the arcuate-shaped cavity of one of the body and cover portions.

7. The metering unit of claim 1 in which the metering chamber has a volumetric capacity of less than one cubic centimeter.

8. The metering unit of claim 7 in which the valve means is actuated to provide the predetermined rate of administration of fluid in the range of two tenths milliliter per minute to ten milliliters per minute.

9. The metering unit of claim 1 further including hydraulic means with a fluid chamber receiving fluid from the metering chamber for having fluid in the fluid chamber moved into the metering chamber to cause air in the metering chamber to be expelled through the inlet conduit means when the metering unit is in operative relationship.

10. The metering unit of claim 1 further including a reservoir chamber adapted to receive a portion of the increments of fluid from the source at a first hydrostatic pressure and to hold the fluid at a second hydrostatic pressure, the metering chamber receiving the predetermined increment of fluid from the reservoir chamber and emptying the predetermined increment of fluid without adding substantial pressure to the second hydrostatic pressure.

11. The metering unit of claim 10 in which means is provided for supporting the reservoir chamber with respect to the metering chamber so that when the source of fluid has been drained below a predetermined level, the second hydrostatic pressure of the fluid in the reservoir chamber is only sufficient to have the metering chamber receive a portion of a predetermined increment of fluid from the reservoir chamber to be emptied from the metering chamber.

12. A disposable metering unit for use in controlling the intravenous administration of a fluid to a patient, comprising:

inlet conduit means for delivering fluid at a hydrostatic pressure from a source of fluid;

metering means for receiving a predetermined increment of fluid from the conduit means and for emptying the predetermined increment of fluid by the suction of gravity flow without adding substantial pressure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means being capable of being moved at said hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm means, and a second position in which the diaphragm is in contact with the other of said opposed inner walls of the metering chamber with substantially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering means may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means;

outlet conduit means communicating with the metering means for receiving said increments wherein gravity suction flow takes place to empty the metering means when the outlet means is opened, the transverse dimensions of said inlet and outlet conduit means being substantially less than the transverse dimension of said metering means, said diaphragm means defining extensions residing in said inlet and outlet conduit means; both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communicating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in contact in its second position, to facilitate free flow of air into and out of said metering chamber as said diaphragm means moves between its first and second positions; and

apertures positioned in said inlet conduit means and outlet conduit means adapted to permit passage of plunger means respectively into said inlet and outlet conduit means to respectively press said diaphgram extensions into sealing relationship with walls of the inlet and outlet conduit means, to selectively block liquid flow through said inlet and outlet conduit means.

13. The disposable metering unit of claim 12 in which a projection is positioned on the inner wall of each inlet and outlet conduit means in opposed relation to said apertures, to define a valve face against which said diaphragm extensions are pressed by said plunger means.

14. A disposable metering unit for use in controlling the intravenous administration of fluid to a patient, comprising:

(a) a reservoir chamber adapted to receive a portion of the increments of fluid from a source of fluid at a first hydrostatic pressure, and to hold the fluid at a second hydrostatic pressure;

(b) a metering chamber for receiving a predetermined increment of fluid from said reservoir chamber and for emptying the predetermined increment of fluid without adding substantial pressure to the second hydrostatic pressure, said metering chamber having a movable diaphragm means therein to meter a predetermined quantity of fluid therethrough;

(c) conduit means for delivering fluid at the source of fluid having a supply of predetermined increments of fluid to the metering chamber; and

(d) valve means actuatable for regulating the receiving and emptying of each of the predetermined increments of fluid by the metering chamber to be administered to the patient at a predetermined rate of administration.

15. The metering unit of claim 14 in which means is provided for supporting the reservoir chamber with respect to the metering chamber so that when the source of fluid has been drained below a predetermined level, the second hydrostatic pressure of the fluid in the reservoir chamber is only sufficient to have the metering chamber receive a portion of a predetermined increment of fluid from the reservoir chamber to be emptied from the metering chamber.

16. Apparatus for controlling the intravenous administration of fluid to a patient which comprises:

inlet conduit means for delivering fluid at a hydrostatic pressure from a source of fluid;

metering means for receiving a predetermined increment of fluid from the conduit means and for emptying the predetermined increment of fluid by the suction of gravity flow without adding substantial pressure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means capable of being moved at the hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm and a second position in which the diaphragm is in contact with the other of said opposed inner walls of the metering chamber with substantially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering chamber may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means, both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communicating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in contact in its second position, to facilitate free flow of air into and out of said metering chamber as said diaphragm means moves between its first and second positions; and

outlet conduit means communicating with the metering means for receiving said increments and conveying them to a patient wherein gravity suction flow takes place to empty the metering means when the outlet means is opened, and valve means in said inlet and outlet conduit means for the alternative and sequential valving of fluid through said inlet conduit means and outlet conduit means.

17. The apparatus of claim 16 in which the transverse dimensions of said inlet and outlet conduit means are substantially less than the transverse dimension of said metering means, said diaphragm means defining extensions residing in said inlet and outlet conduit means, apertures positioned in said inlet conduit means and outlet conduit means, and plunger means adapted to pass respectively into said inlet and outlet conduit means through said apertures to respectively press said diaphragm extensions into sealing relationship with walls of the inlet and outlet conduit means, to selectively block liquid flow through said inlet and outlet conduit means.

18. The apparatus of claim 17 in which a projection is positioned on the inner wall of each inlet and outlet conduit means in opposed relationship to said apertures, to define a valve face against which said diaphragm extensions are pressed by said plunger means.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for controlling the dispensing of fluid, and more particularly, to a means for controlling the intravenous administration of a desired dose of fluid into a body.

The present invention is concerned with controlling the dispensing of fluid and is primarily concerned with the intravenous administration of a desired dose of fluid into the body of a patient. In the prior art, apparatus used for the intravenous administration of fluid have been generally of two basic varieties. The most common intravenous administration device is of the gravity flow type in which the rate of delivery of fluid is adjusted by means of a variable restriction. In such gravity flow systems, the variable restriction is usually provided by a clamping device that deforms a resilient fluid delivery tube connected to the hypodermic needle through which the fluid is introduced into the vascular system of the patient. The gravity flow types of devices may vary widely in cost and in the manner and complexity for controlling the flow rate of the fluid delivered to the patient.

It has been found that such gravity flow devices employing a variable restriction are incapable of reliable and uniform operation due to a number of factors, such as, the tendency of the plastic delivery tube to be subject to delayed plastic flow under stress, the variations in the hydrostatic pressure from the volume of fluid to be administered, variations in fluid viscosity, and changes in physical position and vascular pressure of the patient that may occur during administration of a quantity of fluid. In the gravity flow types of devices, the adjustment of the variable restriction governing the flow rate may be required to be performed manually, which is time consuming and subject to erroneous adjustment. Also, it is desirable for a doctor or nurse to frequently check the flow rate in administration of fluid in such devices to make sure that it is properly regulated. Moreover, a possible serious problem may occur in use of these types of devices when a complete stoppage of flow of fluid takes place, if the device is unattended at the time of exhaustion of the fluid. The unattended stoppage of flow of fluid at the needle in the patient may result in a blood clot which may cause a dangerous condition for the patient.

The other common variety of intravenous administration device is of the pump type which was designed to overcome various disadvantages of the gravity flow types of intravenous administration devices. Many different and complicated arrangements have been developed for regulating the pumping action and the quantity of fluid discharged. In the prior art, much design effort has been exerted to overcome the inherent capacity of the pump to force air into the patient with possible fatal consequences. The pump type of intravenous administration device has tended to be expensive, cumbersome, and complicated in structure. Further, these devices have been dependent upon a source of power greater than can be reliably and economically supplied by a battery. Various clinical reasons exist for avoiding the use of alternating current sources of power with intravenous administration devices, such as, electro-magnetic interference created by the power supply interfering with sensitive clinical devices and electrical impulses from the electrical systems for the pump devices being transmitted through intravenous fluid, which may be electrically conductive, to patients having sensitive heart conditions.

Accordingly, it is an objective of the present invention to provide an intravenous administration apparatus which is inexpensive and simple to operate while administering a desired dose of fluid in an accurately controlled manner. In order to accomplish this objective, it is desirable to provide a method and associated apparatus for intravenous administration of fluid at an accurately controlled rate irrespective of variables, such as, the level of fluid in the source, the venous pressure of the patient, and the viscosity of the fluid. Furthermore, it is desirable to provide an intravenous administration apparatus which enables automatic and progressive reduction of the rate of administration of the fluid at or near the time the desired dose has been administered and before complete exhaustion of the fluid in the administration apparatus so that air is not injected into the patient and blood clotting at the point of administration is prevented.

It is desirable to provide an intravenous administration apparatus which is small in size, light in weight, easily portable, and rugged in design. It is also desirable to provide such apparatus which includes a reusable timer capable of a long expectancy of use and a small, portable, replaceable power supply capable of supplying power to the apparatus. It is further highly desirable to provide an intravenous administration apparatus in which the parts of the apparatus through which the fluid passes is provided by a disposable unit, which is replaced after each use for easily maintaining the apparatus in a sterile condition. Moreover, it is desirable to provide an intravenous administration apparatus in which the parts of the apparatus are adapted to cooperate together in operative relationship only when the apparatus is properly assembled and conditioned for safe administration of fluid and provide such an apparatus which minimizes the likelihood of error by the person responsible for performing the intravenous administration of fluid to the patient.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new and improved method and apparatus has been provided with novel features which cooperate to enable an economical, accurately controlled and reliable arrangement for intravenous administration of a volume of fluid. Accordingly, these and other objects are achieved by providing a novel method for controlling the dispensing of a fluid from a source at a hydrostatic pressure, which comprises the procedure of measuring the fluid from the source into predetermined volumetric increments for dispensing the fluid, providing time intervals for measuring and dispensing of the predetermined volumetric increments of fluid, and then sequentially metering each of the predetermined volumetric increments of fluid during different ones of the time intervals. In accordance with the preferred process of dispensing the fluid, the predetermined volumetric increments are released from the source of fluid by providing a receptacle having a size of the predetermined volumetric increment and the receptacle is filled with fluid by gravity flow from the source of fluid and then the fluid is emptied from the receptacle for administration during each of the time intervals.

The preferred apparatus employed in accordance with the present invention for controlling the dispensing of fluid at a hydrostatic pressure includes metering means for receiving a predetermined increment of fluid and for emptying the predetermined increment of fluid. In addition, the apparatus has conduit means for delivering fluid to the metering means from a source of fluid having a supply of predetermined increments of fluid, and control means for actuating the metering means between a condition for receiving a predetermined increment of fluid and a condition for emptying the predetermined increment of fluid.

The fluid from the source is dispensed through the metering means by the metering means sequentially receiving and emptying each of the predetermined increments of fluid. For this purpose, the metering means has a metering chamber and the apparatus further includes valve means for regulating the receiving and emptying of fluid by the metering chamber. The valve means is preferably provided by an inlet valve connected with one part of the metering chamber and an outlet valve connected with another part of the metering chamber, the inlet and outlet valves being operable in response to actuation from the control means to permit the metering chamber to receive and empty the predetermined increments of fluid. The control means includes timer means for sequentially providing a time interval in which the inlet valve permits passage of fluid into the metering chamber and the outlet valve prevents passage of fluid, and the timer means provides another time interval in which the inlet valve prevents passage of fluid into the metering chamber and the outlet valve permits passage of the predetermined increment of fluid from the metering chamber.

In one form of the invention, the control means or unit includes releasable fastening means, which may be provided by retaining and positioning means, cooperating with the metering means or unit to hold the metering unit in fixed operative relationship with the control unit for having the valve means responsive to the control unit. Also, preferably, the metering unit includes hydraulic means with a fluid chamber receiving fluid from the metering chamber for having fluid in the fluid chamber move into the metering chamber to cause air in the metering chamber to be expelled through the conduit means, when the retaining and positioning means moves the metering unit into the fixed operative relationship. In this arrangement, the control unit includes actuating means cooperable with the hydraulic means to actuate the hydraulic means to move fluid in the fluid chamber into the metering chamber when the retaining means couples the components together in operative relationship. In order to assure that air has been expelled from the metering chamber when the apparatus is to be operated, the control unit further includes interlock sensor means for sensing fluid in the fluid chamber and preventing the retaining and positioning means from moving the metering unit into the fixed operative relationship with the control unit, when a predetermined volume of fluid is not present in the fluid chamber for being moved into the metering chamber to purge air from the metering chamber.

In still a further arrangement of the present invention, the apparatus includes a reservoir chamber adapted to receive a portion of the increments of fluid from the source of fluid and to hold the fluid at a second hydrostatic pressure, and inlet means connects the reservoir chamber with the metering chamber. When the source of fluid has been emptied in this arrangement, the second hydrostatic pressure of the fluid in the reservoir chamber is only sufficient to have the metering chamber receive a portion of a predetermined increment of fluid from the reservoir chamber in the time interval provided, so that continued metering of fluid to the patient is provided at a reduced rate to prevent blood clotting at the hypodermic needle in the patient. In this manner, a longer time is allowed for the person responsible for administering the intravenous dose to return to the patient and remove the apparatus at or after the time that the desired dose has been administered to the patient.

The arrangement of the metering unit and control unit in accordance with the present invention is such that, in dispensing the fluid, the fluid passes through the metering unit without contacting the control unit. Hence, the control unit does not have to be maintained in a sterile or uncontaminated condition. The control unit will be reused and only the metering unit, which is made as a disposable item, will be discarded after having been used once. Thereafter, upon the next desired use of the apparatus, a new metering unit is used in cooperation with the control unit. It should be appreciated that the intravenous administration apparatus of the present invention can be used for many intravenous administrations of fluid and only requires replacement of the inexpensive metering unit between uses. Further, the features of the present invention minimize the likelihood or error in administration of fluid by the person responsible for using the apparatus and has many safety features to prevent the occurrence of dangerous conditions to the patient during the intravenous administration of the fluid.

For a better understanding of these and other features and advantages of the present invention, reference is made to the following drawings, in which:

FIG. 1 is an elevational view showing an apparatus for controlling the dispensing of fluid embodying the present invention connected with a container of fluid;

FIG. 2 is a perspective view of the control unit and metering unit of FIG. 1 and showing the units prior to being fastened together;

FIG. 3 is a perspective view of the control unit and metering unit of FIG. 2 but showing the units fastened together in operative relationship;

FIG. 4 is an enlarged fragmentary sectional view taken along line 4--4 of FIG. 2;

FIG. 5 is a fragmentary side elevational view of the metering unit of FIG. 4 but showing the cover panel of the metering unit and the metering unit diaphragm removed;

FIG. 6 is a fragmentary perspective view of the metering unit diaphragm of FIG. 4;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 5;

FIG. 8 is a sectional view taken along line 8--8 of FIG. 1;

FIG. 9 is a fragmentary sectional view taken along line 9--9 of FIG. 8;

FIG. 10 is a sectional view taken along line 10--10 of FIG. 9;

FIG. 11 is a fragmentary sectional view taken along line 11--11 of FIG. 9;

FIG. 12 is a fragmentary sectional view taken along line 12--12 of FIG. 9;

FIG. 13 is a reduced-dimension perspective view of one of the valve actuator pins of FIG. 9;

FIG. 14 is a sectional view taken along line 14--14 of FIG. 8 and showing the control unit in the condition in which the metering unit (shown in dot-and-dashed lines) is coupled to the control unit;

FIG. 15 is a sectional view similar to FIG. 14 but showing the retaining and positioning means of the control unit in a condition in which the metering unit (shown in dot-and-dashed lines) is released from, or received by, the control unit;

FIG. 16 is a fragmentary sectional view of a portion of the metering unit and a portion of the control unit and showing the interlock sensor mechanism of the control unit in a condition for preventing the retaining and positioning means from moving the metering unit into fixed operative relationship with the control unit;

FIG. 17 is a fragmentary sectional view of a portion of the metering unit and a portion of the control unit of FIG. 16 but showing the interlock sensor mechanism of the control unit in a condition for permitting the retaining and positioning means to move the metering unit into fixed operative relationship with the control unit;

FIG. 18 is a fragmentary sectional view of an alternative embodiment of a metering unit which may be employed in accordance with the present invention;

FIG. 19 is a plan view of the metering unit of FIG. 18; and

FIG. 20 is an electrical schematic diagram, partly in block form, illustrating the timer control circuit for providing time intervals during which the control unit actuates the metering unit to receive and empty fluid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus of the present invention may be used in many different applications for controlling the rate of flow of fluid from a source of fluid. The use of the present apparatus is not limited to administration of fluid from a fixed volume or quantity of fluid. The apparatus can be used, for example, in proportioning the mixture of two or more ingredients in a mixing or processing operation where one or more apparatus in accordance with the present invention is employed. While the apparatus for controlling the dispensing of fluid at a hydrostatic pressure in accordance with the present invention may be used for dispensing fluid in a wide variety of applications, the apparatus will be described in use in intravenous administration of a volume of fluid as a dose injected in a host, which may be an animal or human and will be referred to hereinafter as a patient. The apparatus of the present invention is particularly useful in this latter application where an accurately controlled rate of administration of a fluid is required and safety in operation of the apparatus is important.

Referring now to the embodiment of the invention illustrated in FIG. 1, the invention is shown in use for intravenous administration of fluid to a patient (not shown). The intravenous administration apparatus generally designated 10 for controlling the dispensing of fluid at a hydrostatic pressure to a patient is connected to a source of fluid 12, which is shown as a fluid storage bottle or container adapted to be supported above the apparatus 10, which in turn is preferably positioned a distance above the point of application of the fluid into the patient. The fluid may be administered into the patient by a hypodermic needle (not shown) inserted into the vascular system of the patient and connected to the output of the apparatus 10 by suitable, flexible tubing 14. It is preferred for the apparatus 10 to be suspended at a height of at least thirty inches above the point of application to the patient to cause fluid to flow from the container through the apparatus to the patient by gravity flow. The hydrostatic pressure of the fluid as referred to herein indicates the force or pressure that the fluid exerts as it flows into the apparatus 10, and in the application of the apparatus in FIG. 1, the hydrostatic pressure corresponds to the force or pressure of gravity. Of course, in intravenous administration, the term fluid is used to indicate a liquid.

There is shown in FIGS. 1-3 the apparatus 10 comprising a metering means or unit generally designated 16 and a control means or unit generally designated 18. The metering unit 16 and control unit 18, which are shown separated in FIG. 2, are adapted to interfit together, as indicated in FIGS. 1 and 3, with the control unit having releasable fastening means cooperating with the metering unit for holding the metering unit in fixed operative relationship to the control unit 18. The metering unit and control unit are adapted to cooperate together in operative relationship such that in dispensing the fluid by the apparatus, fluid passes through the metering unit 16 without contacting the control unit 18. More particularly, the metering unit 16 is provided for receiving predetermined increments of fluid from fluid supply bottle or container 12 through inlet tube or conduit means 20 and for emptying the predetermined increments of fluid through outlet tube or conduit means 14 to the patient. Control unit 18 is provided for actuating the metering unit between a condition for receiving a predetermined increment of fluid and a condition for emptying the predetermined increment of fluid in a sequential manner.

According to the preferred process of use of the invention, the fluid from the supply container is measured into predetermined volumetric increments in the metering unit and time intervals are set for measuring and dispensing of the predetermined volumetric increments of fluid through the metering unit. In this procedure, the invention provides sequential measuring and dispensing of each of the predetermined volumetric increments of fluid during different ones of the time intervals. The measuring and dispensing of the volumetric increments of fluid is referred to herein as metering of fluid. In this arrangement, the metering unit 16 is provided with a receptacle or metering chamber having a size of the predetermined volumetric increment and the receptacle is filled with fluid by gravity flow from the fluid supply container and then the receptacle is emptied of fluid for intravenous administration into the body during each of the time intervals, as will be explained more fully hereinafter.

The metering unit 16 for receiving the fluid from the container 12 and emptying the fluid in predetermined volumetric increments to the patient is shown most clearly in FIGS. 4, 5, and 9. Metering unit 16 includes a reservoir or drip chamber 22, metering chamber 24, inlet means or conduit 26 connected between drip chamber 22 and metering chamber 24, and outlet means or conduit 28 extending from the metering chamber to an enlarged fluid chamber 30. The fluid from fluid chamber 30 passes through outlet passage 32 into tube 14, which is received in an increased diameter recessed encircling passage 32. The outlet conduit 28 also communicates directly with outlet passage 32 by means of a channel or groove 32a formed in body portion 34 and extending through fluid chamber 30, as shown in FIGS. 4, 5, and 9. Metering unit 16 is preferably made of a rigid plastic material, such as polystyrene, and includes a main body member or portion 34 and a cover portion or panel 36, which divides the metering unit into two parts in forming a portion of inlet conduit 26, metering chamber 24, outlet conduit 28, and fluid chamber 30, as shown most clearly in FIGS. 4 and 9. Further, a resilient metering diaphragm 38 of resilient plastic material, such as polyurethane, is captured between the metering unit body portion 34 and the metering unit cover panel 36. The metering unit body portion 34 and metering unit cover panel 36 with diaphragm 38 captured therebetween are preferably joined together by ultrasonic or high-frequency induction bonding, or may be joined together by any suitable epoxy or bonding compound or by screws.

As shown most clearly in FIGS. 4, 5, and 9, the inlet conduit 26 has inlet valve means generally designated 40 therein and is a serpentine-shaped passage around raised portion or projection 42, which closes inlet conduit 26 in body portion 34 and forms a valve face. Cavity 44 formed as a recess in cover panel 36 provides a valve cavity and facilitates flow of fluid around projection 42 in inlet conduit 26. Similarly, outlet conduit 28 has outlet valve means generally designated 46 therein and is a serpentine-shaped passage around raised portion or projection 48, which closes outlet conduit 28 in body portion 34 and forms a valve face. Cavity 50 formed as a recess in cover panel 36 provides a valve cavity and facilitates flow of fluid around projection 48 in outlet conduit 28. In this arrangement, the diaphragm 38, as shown in FIG. 6, has a protrusion 52, which provides a resilient valve element received in valve cavity 44 and a second protrusion 54, which provides a resilient valve element received in valve cavity 50. The resilient valve elements 52 and 54 are normally in the position shown in FIG. 4 which have the inlet conduit 26 and outlet conduit 28, respectively, in a condition to permit fluid to flow therethrough. The resilient valve elements 52 and 54 are actuated from positions in which the inlet and outlet conduits are open and to positions in which the inlet and outlet conduits are alternately closed by valve actuator means of the control unit, as will be explained more fully hereinafter.

The metering chamber 24 of the metering unit 16 is formed by two opposed arcuate-shaped domes or cavities 24a and 24b in body portion 34 and cover panel 36, respectively. There is provided in arcuate-shaped dome 24a of metering chamber 24 a series of arcuate-shaped recesses 56 communicating with drain passage 58, which in turn communicates with outlet conduit 28. The recesses 56 and passage 58 are provided to facilitate complete emptying of fluid from the metering chamber when it is desired to empty the fluid from the metering chamber. In this arrangement, the diaphragm 38 extends through the metering chamber 24 and is provided with an arcuate-shaped dome 60, which generally conforms to the shape of arcuate-shaped dome 24a of the metering chamber in its normal condition, as shown in FIGS. 4 and 6. The arcuate-shaped dome 60 of the diaphragm provides a movable wall and also conforms to the shape of arcuate-shaped dome 24b of the metering chamber. The diaphragm wall 60 is moved by the force of fluid flowing into the metering chamber to be adjacent dome surface 24b, when the metering chamber is filled with fluid as shown in FIG. 9. A cylindrical air passage 62 is provided through cover panel 36 communicating with dome portion 24b of the metering chamber to permit the movement of air from and into the metering chamber behind movable diaphragm wall 60 as the diaphragm wall 60 moves between a position in which the metering chamber is emptied, as shown in FIG. 4, and a position in which the metering chamber is filled with fluid as shown in FIG. 9.

It will be appreciated that, as the diaphragm wall 60 moves back and forth for fluid to be received and emptied from the metering chamber 24, fluid only contacts one side of the diaphragm wall 60 and the area between metering chamber dome 24a and diaphragm wall 60 defines the active fluid receiving and dispensing portion, generally designated 24c in FIG. 4, of the metering chamber. Although the size of the active fluid portion 24c of the metering chamber 24 varies in size as fluid fills and is emptied from the metering chamber, for convenience in describing the apparatus and its operation, the active fluid portion 24c of the metering chamber 24 will merely be referred to as the metering chamber 24 for receiving and emptying fluid. In this arrangement, the diaphragm wall 60 provides movable means in the metering chamber for varying the size of the metering chamber so that the metering unit is operable in receiving and draining the increments of fluid without air passing through the metering chamber.

In the embodiment of the diaphragm 38 illustrated in the drawings, the pressure to move the diaphragm wall 60 from the position shown in FIG. 4 to the position shown in FIG. 9 is as little as one half inch or less of water head. Therefore, there is always more than adequate hydrostatic pressure to cause movement of the diaphragm wall 60 until the fluid supply above inlet valve 42 is nearly completely exhausted. It is also noted that preferably the diaphragm wall 60 moves between its position in which the metering chamber is empty and its position in which the metering chamber is filled with fluid without substantial resistance or without adding substantial pressure to the hydrostatic pressure of the fluid filling the metering chamber. Accordingly, the diaphragm is preferably made of a thin resilient material.

Although the volumetric capacity of metering chamber 24 may be made to vary widely depending on the quantity of fluid desired to be delivered by the apparatus in each volumetric increment and the particular application of the apparatus involved, in intravenous administration of fluid it is preferable that the metering chamber be less than one cubic centimeter. Particularly, in intravenous administration of fluids to humans, it is preferable that the volumetric capacity of the metering chamber for fluid be on the order of two tenths of a milliliter, which is received and emptied from the metering chamber as the resilient diaphragm wall 60 moves back and forth. Hence, the predetermined volumetric increment of fluid received and emptied by the metering unit during each time interval will be two tenths of a milliliter of fluid for this capacity of the apparatus. In this arrangement of the metering chamber, it is preferable to have inlet conduit 26 and outlet conduit 28 of sufficient internal cross-sectional area to permit a flow of two tenths of a milliliter of water through the conduits in five tenths of a second at a four inch hydrostatic pressure of the water flowing into the metering unit.

The metering unit diaphragm 38 is also provided with a resilient cup-shaped portion 64 arranged to normally extend into fluid chamber 30, as shown in FIG. 4. The cup-shaped portion 64 of diaphragm 38 is movable from its normal position to a position where the cup-shaped portion extends into cylindrical opening 66 through cover panel 36 in response to fluid filling fluid chamber 30, as when fluid is prevented from flowing through tube 14 (by a closure, not shown, at the lower end of tube 14) as shown in FIG. 17. For example, fluid is prevented from flowing through tube 14 when the apparatus is assembled and readied for operation. The cup-shaped portion 64 of the diaphragm 38 is employed with the fluid chamber 30 to provide hydraulic means cooperable with actuating means in the control unit to move fluid from the fluid chamber into the metering chamber to cause air in the metering chamber to be expelled through the inlet conduit 26. The fluid is forced from the fluid chamber when the metering unit is fastened to the control unit, as will be explained hereinafter in connection with assembling the metering unit with the control unit. A rigid plastic disc 68 is preferably bonded to the bottom surface of the cup-shaped portion 64 of diaphragm 38, as shown in FIG. 4, in order to strengthen the bottom surface of the cup-shaped portion 64.

The outlet conduit 28, which communicates between the metering chamber 24 and the fluid chamber 30, has an increased dimension portion 28a adjacent the opening to the fluid chamber. The increased dimension portion 28a, as shown clearly in FIG. 5, provides an air trap to assure that air in the fluid chamber 30 passes into the outlet conduit and hence through the metering chamber to the drip chamber 22, as fluid is forced from the fluid chamber 30 through the metering chamber, when the metering unit is being coupled into operative relationship with the control unit.

Referring to control unit 18 of FIGS. 1-3, the control unit 18 has an outer case 80 which has removable side panels 82 and 84 secured to the case as by screws 86. Case 80 of control unit 18 includes a battery compartment 88, which may contain battery 90 to provide a source of power for electrical circuitry in the control unit. Access to the battery compartment is provided through removable side panel 82. The opposite side of case 80 houses control compartment 92, which receives electro-magnetic valve actuating means or mechanism generally designated 94, shown in dot-and-dashed lines in FIG. 1, and the electronic timer means generally designated 96, which is also shown in dot-and-dashed lines in FIG. 1 as including components on a circuit board fixed