Fluid Flow Control Apparatus

Abstract

An electromechanical device for parenteral administration of medical fluids, wherein a normally clamped-off intravenous feeding tube is repetitively opened at a frequency which establishes a desired fluid flow rate through the feeding tube. A plurality of ribbon springs define a combination suspension and toggle mechanism for an electromechanical actuator shaft which is reciprocated to drive an IV tube pincher via flexing of one of the ribbon springs to which the tube pincher is attached.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to improvements in fluid flow control apparatus and, more particularly, to a new and improved drop flow controller device for repetitively opening and closing an IV tube in the parenteral administration of medical liquids.

The usual medical procedure for the gradual parenteral administration of fluid into the human body, such as liquid nutrients, blood or plasma, makes use of apparatus which is commonly referred to in the medical arts as an intravenous set. The intravenous set usually comprises a bottle of liquid, normally supported in an inverted position, an intravenous feeding tube, typically of plastic, and a suitable valve mechanism, such as a roll clamp, which allows the liquid to drip out of the bottle at a controlled rate into a drip chamber below the bottle. The drip chamber serves a dual function of allowing a nurse or other attendant to observe the rate at which the liquid drips out of the bottle and also creates a reservoir for the liquid at the lower end of the chamber to ensure that no air enters the main feeding tube leading to the patient.

While observation of the rate of drop flow via the drip chamber is a simple way of controlling the amount of liquid fed to a patient over a period of time, its ultimate effectiveness requires that a relatively constant vigil be maintained on the drop flow, lest it cease entirely due to exhaustion of the liquid supply or become a continuous stream and perhaps increase the rate of liquid introduction to the patient to a dangerous level.

By way of example, it has been a general practice in hospitals to have nurses periodically monitor drop flow rate at each intravenous feeding or parenteral infusion station. Such monitoring of drop flow rate is a tedious and time-consuming process, prone to error and associated, possibly serious consequences, and resulting in a substantial reduction of the available time of qualified medical personnel for other important duties.

In addition to the aforedescribed difficulties, the parenteral administration of medical liquids by gravity induced hydrostatic pressure infusion of a liquid by a bottle or other container suspended above a patient is very susceptible to fluid flow rate variation due to changes in the liquid level in the bottle, changes in temperature, changes in the venous or arterial pressure of the patient, patient movement, and drift in the effective setting of the roll clamp or valve mechanism pinching the feeding tube.

It will be apparent, therefore, that some of the most critical problems confronting hospital personnel faced with an overwhelming duty schedule and limited man-hour availability are the problems of quickly, easily, reliably and accurately controlling drop flow rate in the parenteral administration of medical liquids. In recent years, relatively sophisticated electrical monitoring systems and drop flow controllers have been developed to accomplish the various tasks of sensing and regulating drop flow rates. However, while such monitoring and drop flow controllers have generally served their purpose, they have not always proven entirely satisfactory from the standpoint of reliability and accuracy over a wide range of selected flow rates. For example, some drop flow controllers of the prior art have been unable to prevent passage of two drops instead of one when the feeding tube is opened momentarily, and such controllers have also been troubled by inconsistent drop size. Some additional problems encountered with drop flow controllers have been high noise levels, mechanical fatigue over long periods of operation, and inadequate tube clamp-off forces.

One very successful solution to the problems of reliability and accuracy in drop flow controllers is disclosed in co-pending application Ser. No. 102,665, filed Dec. 30, 1970, now abandoned, inventor Heinz W. Georgi, entitled METHOD AND APPARATUS FOR FLUID FLOW CONTROL, and specifically incorporated herein by reference. In the latter application, a closed loop electronic system controls an IV tube pincher which vibrates at a frequency which is a relatively high multiple of the desired drop flow rate to cyclically open and close the IV tube. In this regard, it will be appreciated that such a system requires an extremely reliable means for rapidly vibrating the tube pincher over extended periods of time. Hence, those concerned with the development and use of parenteral fluid administration systems which utilize such vibrating tube pinchers have long recognized the need for relatively simple, economical, reliable, and quiet apparatus for cyclically squeezing and unsqueezing an IV tube at a controlled rate. The present invention clearly fulfills this need.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention provides a new and improved apparatus for controlling drop flow in the parenteral administration of medical liquids, wherein a flexible toggle mechanism vibrates a tube pincher to repetitively open and clamp off an IV tube.

Basically, the apparatus for vibrating the IV tube pincher includes a ribbon spring system defining a combined suspension and toggle mechanism for reciprocating actuator shaft which drives the tube pincher by repetitively flexing a ribbon spring to which the tube pincher is attached. If desired, the actuator shaft may be supported at both of its extremities by ribbon springs so that the shaft is essentially floating, although guided, and thereby encounters no friction.

In a presently preferred embodiment, by way of example, a feeding tube pincher is cyclically moved to the tube-open position by a mechanism which includes a substantially rectangular support system defining a floating suspension comprising a plurality of flexible ribbon springs, the springs being interconnected only at their corners by means of corner blocks which are common to adjacent springs. One pair of opposing sides of the support system are formed of single springs, while each of the remaining two sides is formed by two parallel springs connected to opposite faces of the corner blocks. Two of the diagonally opposed corner blocks are rigidly fastened to a fixed secondary structure, such as a mounting plate, while the remaining two corners are allowed to float free.

An electromechanical actuator, in the form of a voice coil actuator or solenoid, has its stator fixed to the secondary structure, with the remote ends of the actuator shaft connected to and suspended between the centers of the single ribbon springs. When unexcited, the actuator allows the springs to remain in a parallel, unflexed relationship. When the actuator is excited, the actuator shaft flexes the ribbon springs to which it is attached, causing the free floating corner blocks to move inwardly with the flexing movement. The ribbon springs flex, but do not stretch. The IV tube pincher is connected to one of the free corner blocks and is positioned so as to normally clamp off an IV tube when the actuator is unexcited, thereby preventing flows of fluids through the tube. When the actuator is excited, its reciprocating shaft flexes the springs which, in turn, vibrate the tube pincher to allow a controlled rate of fluid to pass through the IV tube. The actuator shaft and ribbon spring to which the tube pincher is attached define a flexible toggle mechanism.

The flexible toggle mechanism for driving the tube pincher requires only a low deflection force for retracting the tube pincher to open the IV tube to flow yet provides an extremely high tube clamping force for shutting off flow when the ribbon spring is in its relaxed, substantially straight condition. The vibrating apparatus is extremely quiet, since the actuator shaft is essentially floating and encounters no friction. The system is also extremely reliable and experiences substantially no fatigue even when maintained in operation for extended periods of time.

The above and other objects and advantages of this invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings of illustrative embodiments.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a fluid flow control apparatus constructed in accordance with the present invention and illustrating the basic principles thereof;

FIG. 2 is an enlarged, sectional view, taken along the line 2--2 in FIG. 1;

FIG. 3 is a perspective view of a presently preferred embodiment of a fluid flow control apparatus embodying the features of the present invention;

FIG. 4 is a front elevational view of the apparatus shown in FIG. 3;

FIG. 5 is a left end elevational view of the apparatus shown in FIG. 4;

FIG. 6 is a right end elevational view of the apparatus shown in FIG. 4;

FIG. 7 is a top plan view of the apparatus shown in FIG. 4; and

FIG. 8 is a front elevational view of an alternative embodiment of a fluid flow control apparatus constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and particularly to FIG. 1 thereof, there is shown a simplified form of a drop flow controller 10 which illustrates some of the basic principles of the present invention. The controller 10 includes a tube pincher 11 for cyclically clamping off and opening an IV tube 12 to permit fluid flow at a controlled rate through the tube. The tube pincher 11 clamps the tube 12 against any suitable member 13 providing a hard clamping surface 13a. The pincher 11 is normally spring-biased to the tube clamp-off state by the relaxed condition of a substantially flat ribbon spring 14, of a strong, resilient material such as steel or the like. The ribbon spring 14 has a free end affixed to the tube pincher 11, as by screws 15, and has its opposite end secured to an anchor block 16, as by screws 17. The anchor block 16 is rigidly fastened in any appropriate manner to a suitable fixed secondary structure (not shown).

As shown in both FIGS. 1 and 2, the tube pincher 11 is mounted for sliding movement along a guide block 18, so that the pincher can vibrate back and forth, in a substantially linear path, to open and close the IV tube 12. By confining the pincher movement to a substantially linear path, gradual creeping of the tube 12 along a path normal to the clamping forces is avoided.

The center of the spring 14 is rigidly connected by a coupling 19 to a shaft 21 of an electromechanical actuator 22, such as a voice coil actuator or solenoid. As in the case of the anchor block 16, the stator magnet 22a of the actuator 22 is rigidly secured in any appropriate manner to a fixed secondary structure (not shown).

In actual practice, a voice coil actuator is preferred over a solenoid since force is directly proportional to electrical current for the voice coil actuator, and the force is substantially constant over the linear range of movement of the actuator shaft, whereas force is a complex square law function of both current and distance for a solenoid. In addition, there is less noise generation with a voice coil actuator than with a solenoid, the latter having some tendency to bang the limit stops in view of the typical force-velocity characteristic for solenoids.

Deflection of the ribbon spring 14 by movement of the shaft 21 is substantially normal to the longitudinal axis of the spring. In this regard, the deflected position of the spring 14 is shown in phantom in FIG. 1.

Deflection of the spring 14 causes foreshortening of the free end of the spring along the relaxation axis of the spring so that the tube pincher 11 is retracted along the guide block 18 to open the IV tube 12 to fluid flow. The deflection force necessary to flex the spring 14 is quite small compared to the force actually applied by the spring to the tube pincher 11. In this connection, release of the spring 14 permits the spring to return to its relaxed, unflexed state and provide an extremely high clamp-off force along its relaxation axis via the tube pincher 11 to the IV tube 12. The latter, in turn, provides positive shutoff of fluid flow. In essence, therefore, the actuator shaft 21 and ribbon 14 cooperate to provide a flexible toggle mechanism for vibrating the tube pincher 11 in an extremely reliable, essentially noiseless manner with low power requirements, high leverage advantage and extremely positive shutoff characteristics.

Referring now to FIGS. 3 through 7 of the drawings, there is shown a presently preferred embodiment of a drop flow controller 110 constructed in accordance with the present invention. In the embodiment of the invention shown in FIGS. 3-7, the reference numerals 110 through 122 indicate like or corresponding parts indicated by the reference numerals 10 through 22, respectively, in the embodiment of FIGS. 1 and 2.

The anchor block 116 is secured to a mounting plate 123 by any suitable fastening means, such as the screws 124. Similarly, the stator 122a of the actuator 122 is secured to the mounting plate 123 by a pair of screws 125 which extend through a mounting flange 126 affixed to and projecting from the plate 123.

The end of the actuator shaft 121 remote from the spring 114 is connected by a coupling 128 to the center of a second single ribbon spring 129. One end of the spring 129 is secured, as by screws 132, to an anchor block 131 affixed to the mounting plate 123 by a pair of screws 133. The opposite end of the spring 129 is secured by a pair of screws 134 to a free floating corner block 136. In this connection, the ribbon spring 114 has its free end, remote from the anchor block 116, connected by a pair of screws 138 to a floating corner block 139 to which the tube pincher 111 is rigidly secured, as by a plurality of screws 141.

A pair of parallel ribbon springs 143 extend between the fixed anchor block 116 and the floating corner block 136, the springs being connected to opposite faces of both blocks by a plurality of screws 144. Similarly, a pair of parallel ribbon springs 146 extend between the fixed anchor block 131 and the floating corner block 139, the springs being secured to opposite faces of both blocks by a plurality of screws 147. The resulting configuration is a substantially rectangular ribbon spring support system defining a floating suspension for the actuator shaft 121 and the tube pincher 111, as well as defining a flexible toggle mechanism for vibrating the tube pincher 111 to repetitively open and close the IV tube 112.

Since both ends of the actuator shaft 121 are supported by the ribbon springs 114 and 129, the shaft is essentially mounted between a pair of floating guides and, therefore, reciprocates back and forth along its axis without any bearing friction. This results in an extremely low wear characteristic and is essentially noiseless. Similarly, since the tube pincher 111 is secured to the floating corner block 139, there is no need for the guide block 18 of FIGS. 1 and 2 and, therefore, the pincher 111 vibrates quietly and without bearing friction.

The use of the pairs of double ribbon springs 143, 146 extending between the fixed anchor blocks 116, 131 and the floating corner blocks 136, 139, respectively, confines the inward movement of the floating corner blocks to substantially linear motion and thereby minimizes twisting moments on the actuator shaft 121 and the tube pincher 111.

In operation of the controller 110, the system starts out with all of the ribbon springs 114, 129, 143, 146 in the relaxed state shown by the solid lines in FIG. 4, and with the tube pincher 111 clamping off the IV tube 112. When the actuator 122 is electrically energized over the line 149, the shaft 121 simultaneously flexes both of the individual ribbon springs 114, 129 to which it is attached, causing the free floating corner blocks 136, 139 to move inwardly with the flexing movement. All of the ribbon springs flex, but they do not stretch. The tube pincher 111 moves to its phantom position shown in FIG. 4 over the linear distance x, to open the IV tube 112 to fluid flow each time the floating corner block 139 moves inwardly. The tube pincher 111 is operated cyclically in this fashion to control the rate of fluid flow through the IV tube 112. A pair of noise damping pads 151, of rubber or the like, are secured to opposite faces of the flat ribbon spring 114, and a similar pair of pads 152 are secured to opposite faces of the ribbon spring 129, to minimize vibration of the flexible springs at harmonic frequencies.

Referring now to FIG. 8 of the drawings, there is shown an alternate embodiment of a drop flow controller 210 constructed in accordance with the present invention. In the embodiment of the invention shown in FIG. 8, the reference numerals 210 through 247 indicate like or corresponding parts indicated by the reference numerals 110 through 147, respectively, in the embodiment of FIGS. 3-7.

The primary difference between the embodiment of the invention shown in FIG. 8 and the embodiment of FIGS. 3-7 resides in the elimination of the pair of ribbon springs 143 and floating corner block 136. Instead, the end of the actuator shaft 221 remote from the ribbon spring 214 is secured to one end of a shorter ribbon spring 253 extending from the fixed anchor block 231. This provides a floating suspension and guide for the actuator shaft 221 in a more economical structural arrangement, but with greater susceptibility to twisting of the actuator shaft than with the more sophisticated apparatus of FIGS. 3-7.

The drop flow controller 210 may be further simplified by elimination of one of the ribbon springs 246, but here again, while the apparatus will function in the prescribed manner, the simpler configuration will be subject to greater twisting, not only of the actuator shaft 221, but of the IV tube pincher 211 as well. However, the drop flow controller 210 possesses all of the other advantages of the combined floating suspension and toggle mechanism drive of the embodiments previously described.

Again, the flexible toggle mechanism requires only a very low deflection force for retraction of the tube pincher to open the IV tube to fluid flow, yet provides an extremely high tube clamping force for shutting off flow whenever the ribbon spring 214 is in its relaxed state. The vibrating apparatus is extremely quiet, since both the actuator shaft 221 and the tube pincher 211 are essentially floating and encounter virtually no friction. The overall system is extremely reliable and experiences substantially no mechanical fatigue, even over extended periods of operation.

It will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited except as by the appended claims.

Claims

I claim:

1. In a fluid flow control apparatus, the combination comprising:

a flexible member and a rigid member connected intermediate the ends of said flexible member to define a toggle mechanism; and

a valve member connected to one end of said flexible member and driven by said toggle mechanism, whereby motion of said rigid member actuates said valve member.

2. A combination as set forth in claim 1, wherein said flexible member is a ribbon spring.

3. A combination as set forth in claim 1, wherein said rigid member is the output shaft of a voice coil actuator.

4. A combination as set forth in claim 1, wherein said valve member is a tube pincher for squeezing an IV tube.

5. In a fluid flow control apparatus, the combination comprising:

an elongate, resilient member having one end fixed and its opposite end free to move at least linearly along the relaxation axis of said member when said member is flexed;

a valve member carried at the free end of said resilient member; and

a driver member connected intermediate the fixed and free ends of said resilient member to define, together with said resilient member, a toggle mechanism, whereby motion of said driver member drives said valve member.

6. A combination as set forth in claim 5, wherein said elongate, resilient member is a flat ribbon spring.

7. A combination as set forth in claim 5, wherein said drive member is the output shaft of a voice coil actuator.

8. A combination as set forth in claim 5, wherein said valve member is a tube pincher for squeezing an IV tube.

9. In a fluid flow control apparatus, the combination comprising:

an elongate, resilient member having one end fixed and its opposite end free to move at least linearly along the relaxation axis of said member when said member is flexed;

a valve member carried at the free end of said resilient member; and

an actuator means located intermediate the fixed and free ends of said resilient member and moveable in a direction generally perpendicular to said relaxation axis for flexing said resilient member to impart movement to said valve member.

10. A combination as set forth in claim 9, wherein said resilient member is a ribbon spring.

11. A combination as set forth in claim 9, wherein said actuator means is a voice coil actuator.

12. A combination as set forth in claim 9, wherein said actuator means is a solenoid.

13. A combination as set forth in claim 9, wherein said valve member is a tube pincher for squeezing an IV tube.

14. A combination as set forth in claim 9, wherein said actuator means includes a rigid shaft having its opposite ends connected to said elongate resilient member and a second resilient member, respectively, whereby said shaft is supported in a floating suspension defined by both resilient members.

15. In a fluid flow control apparatus, the combination comprising:

a first elongate, resilient member having a fixed end and a free end;

a valve member carried at the free end of said resilient member;

a second elongate, resilient member having a fixed end and a free end; and

actuator means having a driver shaft with one end connected to said first resilient member intermediate said fixed end and said free end of said first member, said shaft also having its opposite end connected to said second resilient member, whereby movement of said shaft causes said first and said second resilient members to flex and impart movement to said valve member.

16. A combination as set forth in claim 15, wherein said opposite end of said shaft is connected to said second resilient member intermediate said fixed end and said free end of said second member.

17. A combination as set forth in claim 15, wherein said opposite end of said shaft is connected to said second resilient member at said free end of said second member.

18. A combination as set forth in claim 15, and further including:

anchor means; and

a pair of substantially parallel, elongate, spaced apart resilient elements having one pair of ends secured to said anchor means and having its opposite pair of ends coupled to said free end of said first resilient member.

19. A combination as set forth in claim 18, wherein said fixed end of said second resilient member is also secured to said anchor means.

20. A combination as set forth in claim 18, and further including:

a pair of substantially parallel, elongate, spaced apart resilient elements having one pair of ends coupled to said fixed end of said first resilient member and having its opposite pair of ends coupled to said free end of said second resilient member.

21. A combination as set forth in claim 15, wherein said first and said second resilient members are both ribbon springs.

22. A combination as set forth in claim 15, wherein said actuator means is a voice coil actuator.

23. A combination as set forth in claim 15, wherein said actuator means is a solenoid.

24. A combination as set forth in claim 15, wherein said valve member is a tube pincher for squeezing an IV tube.

25. In a fluid flow control apparatus, the combination comprising:

first anchor means;

second anchor means;

junction means;

a first elongate, substantially flat ribbon spring having one end secured to said first anchor means and having its opposite free end attached to said junction means;

a second elongate, substantially flat ribbon spring having one end secured to said second anchor means and having its opposite free end attached to said junction means;

a valve member coupled to said junction means; and

actuator means having a driver shaft with one end connected to said first spring intermediate said one end and said free end of said first spring, whereby flexing of said first spring by said shaft imparts movement to said junction means and said valve member.

26. A combination as set forth in claim 25, and further including:

a third elongate, substantially flat ribbon spring having one end secured to said second anchor means, said third spring also being coupled to the end of said driver shaft opposite said one end connected to said first spring, whereby said driver shaft is supported in a floating suspension.

27. A combination as set forth in claim 25, wherein said actuator means is a voice coil actuator and said valve member is an IV tube pincher.

28. A combination as set forth in claim 26, wherein said driver shaft is connected to the free end of said third spring.

29. A combination as set forth in claim 26, and further including:

a second junction means, the free end of said third spring being attached to said junction means; and

a fourth elongate, substantially flat ribbon spring having one end secured to said first anchor means and having its opposite free end attached to said second junction means.

30. A combination as set forth in claim 29, wherein said actuator means is a voice coil actuator.

31. A combination as set forth in claim 30, wherein said valve member is an IV tube pincher.

32. In a fluid flow control apparatus, the combination comprising:

a first anchor block;

a second anchor block;

a first, floating corner block;

a second, floating corner block;

a first elongate, substantially flat ribbon spring having one end secured to said first anchor block and having its opposite free end attached to said first corner block;

a second elongate, substantially flat ribbon spring having one end secured to said second anchor block and having its opposite free end attached to said first corner block;

a third elongate, substantially flat ribbon spring having one end secured to said second anchor block and having its opposite free end attached to said second corner block;

a fourth elongate, substantially flat ribbon spring having one end secured to said first anchor block and having its opposite free end attached to said second corner block;

a tube pincher carried at said first corner block and adapted to move therewith; and

an actuator means having a driver shaft substantially normal to said first spring and said third spring, said shaft having one end connected to the center of said first spring and having its opposite end connected to the center of said third spring, whereby said shaft is supported in a floating suspension.

33. A combination as set forth in claim 32, and further including:

a fifth elongate, substantially flat ribbon spring parallel to and spaced apart from said second sring, said fifth spring having one end secured to said second anchor block and having its opposite end attached to said first corner block; and

a sixth elongate, substantially flat ribbon spring, parallel to and spaced apart from said fourth spring, said sixth spring having one end secured to said first anchor block and having its opposite end attached to said second corner block.

34. A combination as set forth in claim 33, wherein said actuator means is a voice coil actuator.

35. A combination as set forth in claim 33, wherein said actuator means is a solenoid.