Abstract:
A fluid delivery device having a self-contained, precision mechanical spring-type stored energy source for expelling fluids at a precisely controlled rate. The device can be used by lay persons in a non-hospital environment for the precise infusion of pharmaceutical fluids, such as insulin and the like, into an ambulatory patient at controlled rates over extended periods of time. In one form of the apparatus of the invention, there is provided a unique, micro-channel-type rate control assembly that is disposed intermediate the fluid reservoir outlet and the outlet port of the device and a fluid consumption indicator system for accurately determining the amount of fluid remaining within the device reservoir.

Description:
[0001]     This is a Continuation-in-Part Application of co-pending U.S. application Ser. No. 10/855,478 filed May 26, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time.  
         [0004]     2. Discussion of the Invention  
         [0005]     Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.  
         [0006]     In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.  
         [0007]     A variety of fluid delivery devices from which fluids are controllably expelled by stored energy means provided in the form of elastomeric film materials have been devised by the present inventor. The elastomeric film materials used in these devices as well as various alternate constructions of such devices are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. A low-profile fluid delivery apparatus invented by the present inventor is described in U.S. Pat. No. 5,716,343.  
         [0008]     Devices from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder have also been suggested in the past. Such bladder, or “balloon”-type, devices are described in U.S. Pat. No. 3,469,578 issued to Bierman and in U.S. Pat. No. 4,318,400 issued to Perry. The devices of the aforementioned patents also disclose the use of fluid flow restrictor&#39;s external of the bladder for regulating the rate of fluid flow from the bladder.  
         [0009]     The prior art bladder-type infusion devices are not without drawbacks. Generally, because of the very nature of bladder or “balloon” configuration, the devices are unwieldy and are difficult and expensive to manufacture and use. Further, the devices are somewhat unreliable and their fluid discharge rates are frequently imprecise.  
         [0010]     The apparatus of the present invention overcomes many of the drawbacks of the prior art by eliminating the bladder and also eliminating the elastomeric film energy source and making use of recently developed, high precision mechanical springs which function in cooperation with an expandable bellows assembly as an internal stored energy source for controllably forcing fluid from the apparatus reservoir.  
         [0011]     The apparatus of the present invention can be used with minimal professional assistance in an alternate health care environment such as the home. By way of example, devices of the invention can be comfortably and conveniently removably affixed to the patient&#39;s body or to the patient&#39;s clothing and can be used for the continuous infusion of antibiotics, hormones, steroids, blood clotting agents, analgesics, and like medicinal agents. Similarly, the devices can be used for I-V chemotherapy and can accurately deliver fluids to the patient in precisely the correct quantities and at extended micro-fusion rates over time.  
         [0012]     As will be better understood from the description which follows, the inventions described herein are directed toward providing novel fluid delivery devices which are low-profile and are eminently capable of meeting the most stringent of fluid delivery tolerance requirements. In this regard, medical and pharmacological research continues to reveal the importance of the manner in which a medicinal agent is administered. The delivery device, while not an active pharmacological agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. For example, certain classes of pharmacological agents possess a very narrow dosage range of therapeutic effectiveness, in which case too small a dose will have no effect, while too great a dose can result in toxic reaction. In other instances, some forms of medication require an extended delivery time to achieve the utmost effectiveness of a medicinal therapeutic regimen.  
         [0013]     By way of example, the therapeutic regimens used by insulin-dependent diabetics provide a good example of the benefits of carefully selected delivery means. The therapeutic object for diabetics is to consistently maintain blood glucose levels within a normal range. Conventional therapy involves injecting insulin by syringe several times a day, often coinciding with meals. The dose must be calculated based on glucose levels present in the blood. If the dosage is off, the bolus administered may lead to acute levels of either glucose or insulin resulting in complications, including unconsciousness or coma. Over time, high concentrations of glucose in the blood can also lead to a variety of chronic health problems, such as vision loss, kidney failure, heart disease, nerve damage, and amputations.  
         [0014]     A recently completed study sponsored by the National Institutes of Health (NIH) investigated the effects of different therapeutic regimens on the health outcomes of insulin dependent diabetics. This study revealed some distinct advantages in the adoption of certain therapeutic regimens. Intensive therapy that involved intensive blood glucose monitoring and more frequent administration of insulin by conventional means, i.e., syringes, throughout the day saw dramatic decreases in the incidence of debilitating complications.  
         [0015]     In those embodiments of the invention described in U.S. Pat. No. 5,205,820 issued to the present inventor, the fluid delivery apparatus components generally includes: a base assembly; an elastomeric membrane serving as a stored energy means; fluid flow channels for filling and delivery; flow control means; a cover; and an ullage, which comprises a part of the base assembly. The ullage in these devices typically comprises a semi-rigid structure having flow channels leading from the top of the structure through the base to inlet or outlet ports of the device.  
         [0016]     In the rigid ullage configuration, the stored energy means of the device must be superimposed over the ullage to form the fluid-containing reservoir from which fluids are expelled at a controlled rate by the elastomeric membrane of the stored energy means tending to return to a less distended configuration in a direction toward the ullage.  
         [0017]     Elastomeric membrane materials suitable for use as the stored energy means must possess certain physical characteristics in order to meet the performance requirements for a fluid delivery apparatus. More particularly, for good performance, the elastomeric membrane material must have good memory characteristics under conditions of high extension; good resistance to chemical and radiological degradation; and appropriate gas permeation characteristics depending upon the end application to be made of the device.  
         [0018]     Once an elastomeric membrane material is chosen that will optimally meet the desired performance requirements, there still remain certain limitations to the level of refinement of the delivery tolerances that can be achieved using the rigid ullage configuration. These result primarily from the inability of the rigid ullage to conform to the shape of the elastomeric membrane near the end of the delivery period. This nonconformity can lead to extended delivery rate tail-off and higher residual problems when extremely accurate delivery is required. For example, when larger volumes of fluid are to be delivered, the tail-off volume represents a smaller portion of the fluid amount delivered and therefore exhibits much less effect on the total fluid delivery profile, but in very small dosages, the tail-off volume becomes a larger portion of the total volume. This sometimes places severe physical limits on the range of delivery profiles that may easily be accommodated using the rigid ullage configuration.  
         [0019]     As will be better appreciated from the discussion which follows, the apparatus of the present invention by using precision mechanical springs overcomes many of the drawbacks found in elastomeric membrane-type devices and provides a unique and novel improvement for a disposable dispenser of simple but highly reliable construction that may be adapted to many applications of use.  
       SUMMARY OF THE INVENTION  
       [0020]     It is an object of the present invention to provide a fluid delivery device having a self-contained, precision mechanical spring stored energy source for expelling fluids at a precisely controlled rate which is of a compact, low-profile construction. More particularly, it is an object of the invention to provide such a device which can which can conveniently be used for the precise infusion of pharmaceutical fluids, such as insulin and the like, into an ambulatory patient at controlled rates over extended periods of time.  
         [0021]     It is another object of the invention to provide an apparatus of the aforementioned character which is small, compact, highly reliable and easy-to-use by lay persons in a non-hospital environment.  
         [0022]     It is another object of the invention to provide an apparatus as described in the preceding paragraphs which can conveniently be used for intravenous infusion of fluids into an ambulatory patient.  
         [0023]     A further object of the invention is to provide a low-profile, fluid delivery device which can meet even the most stringent fluid delivery tolerance requirements. In this regard, in one form of the apparatus of the invention, there is provided a unique, micro-channel-type rate control assembly that is disposed intermediate the fluid reservoir outlet and the outlet port of the device.  
         [0024]     Another object of the invention to provide an apparatus of the class described, which includes novel fluid consumption indicator means for accurately determining at any time the amount of fluid remaining within the reservoir of the device.  
         [0025]     Another object of the invention is to provide an apparatus of the class described which includes a fill assembly that can be conveniently used to controllably fill the fluid reservoir of the device.  
         [0026]     Another object of the invention is to provide an apparatus of the character described which, due to its unique construction, can be manufactured inexpensively in large volume by automated machinery.  
         [0027]     Other objects of the invention will become more apparent from the discussion which follows.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a generally perspective, rear view of one form of the fluid delivery device of the invention.  
         [0029]      FIG. 2  is a generally perspective, front view of the fluid delivery device shown in  FIG. 1 .  
         [0030]      FIG. 3  is a top plan view of the base component of the fluid delivery device of the invention.  
         [0031]      FIG. 4  is a cross-sectional view taken along lines  4 - 4  of  FIG. 3 .  
         [0032]      FIG. 5  is a bottom plan view of the base component.  
         [0033]      FIG. 6  is an enlarged, cross-sectional view of the fluid delivery device shown in  FIG. 2  of the drawings.  
         [0034]      FIG. 7  is a cross-sectional view, similar to  FIG. 6 , but showing the fluid reservoir of the device in a filled condition  
         [0035]      FIG. 8  is a cross-sectional, exploded view of the base assembly of the device shown in  FIGS. 1 and 2 .  
         [0036]      FIG. 9  is a side-elevational view of the rate control sub-assembly of the apparatus of the invention.  
         [0037]      FIG. 10  is a view taken along lines  10 - 10  of  FIG. 9 .  
         [0038]      FIG. 11  is a view taken along lines  11 - 11  of  FIG. 9 .  
         [0039]      FIG. 12  is a view taken along lines  12 - 12  of  FIG. 6 .  
         [0040]      FIG. 13  is a top plan view of an alternate form of finger-spring assembly of the apparatus of the invention.  
         [0041]      FIG. 14  is a side-elevational view of the finger-spring assembly shown in  FIG. 13 .  
         [0042]      FIG. 15  is a top plan view of still another form of finger-spring assembly of the apparatus of the invention.  
         [0043]      FIG. 16  is a side-elevational view of the finger-spring assembly shown in  FIG. 15 .  
         [0044]      FIGS. 17A, 17B ,  17 C,  17 D and  17 E, when considered together, comprise a generally diagramatical view of a number of alternate forms of springs and spring assemblies of the apparatus of the invention.  
         [0045]      FIG. 18  is a generally perspective, side view of an alternate form of the fluid delivery device of the invention.  
         [0046]      FIG. 19  is a generally perspective, front view of the fluid delivery device shown in  FIG. 18 .  
         [0047]      FIG. 20  is an enlarged, cross-sectional view of the fluid delivery device shown in  FIGS. 18 and 19  of the drawings.  
         [0048]      FIG. 21  is a cross-sectional view, similar to  FIG. 20 , but showing the fluid reservoir of the device in a filled condition  
         [0049]      FIG. 22  is a cross-sectional, exploded view of the base assembly of the device shown in  FIGS. 18 and 19 .  
         [0050]      FIG. 23  is a top plan view of the indicator plate of the apparatus of the invention.  
         [0051]      FIG. 24  is a view taken along lines  24 - 24  of  FIG. 23 .  
         [0052]      FIG. 25  is a view taken along lines  25 - 25  of  FIG. 23 .  
         [0053]      FIG. 26  is a greatly enlarged, fragmentary view of one form of the indicator window of the apparatus of this latest form of the invention for viewing the amount of fluid remaining within the fluid reservoir of the apparatus.  
         [0054]      FIG. 27  is a fragmentary, cross-sectional view taken along lines  27 - 27  of  FIG. 26 .  
         [0055]      FIG. 28  is a view similar to  FIG. 26  but showing the indicator window as it appears when the reservoir of the device is empty.  
         [0056]      FIG. 29  is a fragmentary, cross-sectional view taken along lines  29 - 29  of  FIG. 28 .  
         [0057]      FIG. 30  is a greatly enlarged, fragmentary view of still another form of the indicator window of the apparatus of this latest form of the invention for viewing the amount of fluid remaining within the fluid reservoir of the apparatus.  
         [0058]      FIG. 31  is a fragmentary, cross-sectional view taken along lines  31 - 31  of  FIG. 30 .  
         [0059]      FIG. 32  is a view similar to  FIG. 30  but showing the indicator window as it appears when the reservoir of the device is empty.  
         [0060]      FIG. 33  is a fragmentary, cross-sectional view taken along lines  33 - 33  of  FIG. 32 .  
         [0061]      FIG. 34  is a greatly enlarged, fragmentary view of yet another form of the indicator window of the apparatus of this latest form of the invention for viewing the amount of fluid remaining within the fluid reservoir of the apparatus.  
         [0062]      FIG. 35  is a fragmentary, cross-sectional view taken along lines  35 - 35  of  FIG. 34 .  
         [0063]      FIG. 36  is a view similar to  FIG. 34  but showing the indicator window as it appears when the reservoir of the device is empty.  
         [0064]      FIG. 37  is a fragmentary, cross-sectional view taken along lines  37 - 37  of  FIG. 36 . 
     
    
     DESCRIPTION OF THE INVENTION  
       [0065]     Referring to the drawings and particularly to  FIGS. 1 through 7 , one form of the device of the invention for use in intravenous infusion of medicinal fluid into a patient is there shown and generally designated by the numeral  28 . As best seen by referring to  FIGS. 6 and 7 , the device here comprises a base assembly  30  which includes a base  32  having an upper surface  34 , including a central portion  34   a  and peripheral portion  34   b  circumscribing central portion  34   a  ( FIG. 4 ). As illustrated in  FIGS. 3 and 8 , central portion  34   a  is provided with a central counterbore  34   c , which houses a filter  35  and is also provided with circuitous, precisely formed fluid flow micro-channels  37 , the purpose of which will presently be described. Base  32  is provided with a lower surface  36  which is engageable with the patient when the device is taped or otherwise removably affixed to the patient. Formed within base  32  is a channel  38  and a pair of central counterbores  40  and  42  ( FIGS. 4 and 7 ) the purpose of which will presently be described.  
         [0066]     Forming an important aspect of the apparatus of the present invention is stored energy means for forming in conjunction with the central portion  34   a  of base  34  a reservoir  44  having an outlet  46  ( FIG. 7 ). The stored energy means is here comprises an expandable bellows  50  which is superimposed over base  32  and is held and position by a capture ring  5   1 . As illustrated in  FIG. 7 , the expandable bellows can be expanded from a first position shown and  FIG. 6  to a second position shown in  FIG. 7  as a result of pressure imparted by fluids “F” introduced into reservoir  44  via the fill means of the invention the character of which will presently be described. In the present form of the invention, the stored energy means further comprises a plurality of circumferentially spaced-apart, yieldably deformable finger-spring members  52  which are operably associated with bellows  50  ( FIGS. 7 and 12 ). Each of the finger-spring members  52  is yieldably deformed in the manner shown in  FIG. 7  by movement of the expandable bellows toward the second position shown in  FIG. 7 . As the bellows  50  expands into the second position internal stresses are formed within the spring members which forces tend to controllably return the expandable bellows to its first position. As the bellows moves toward its first position, fluid contained within reservoir  44  will be urged to flow outwardly of the reservoir through outlet  46  and toward the flow rate control means of the invention the character of which will next be described.  
         [0067]     The important flow rate control means of the invention is here provided in the form of a rate control assembly  64  which includes a pair of generally circular-shaped rate control plates  66  and  68  which are receivable within counterbore  40  formed in base  32 . Rate control assembly  64  also includes a stem portion  70  which is connected to rate control plate  68  and which is provided with a fluid passageway  72  that has an inlet  72   a  and an outlet  72   b . Stem portion  70  is partially received within a channel  38  formed in base  32  and, along with rate control plates  66  and  68 , is held and position within base  32  by a base segment  74  which is provided with a groove  74   a . Groove  74   a  partially receives stem portion  70  when the segment  74  is interconnected with base  32  in the manner shown in  FIG. 6  of the drawings.  
         [0068]     Turning particularly to  FIGS. 9, 10  and  11 , it is to be noted that the upper surface  68   a  of plate  68  is substantially planar and the lower surface  66   a  of plate  66 , which is in mating engagement with upper surface  68   a , is provided with a spiral shaped, laser-etched capillary or micro-channel  78 . Capillary  78  has an inlet port  78   a  that is in communication with reservoir  44  via a passageway  66   b  formed in plate  66  and an outlet port  78   b  that is in communication with inlet  72   a  of the passageway  72  formed an stem portion  70  via a passageway  68   b  formed in plate  68 . Plates  66  and  68 , which may be adhesively bonded together, are indexedly aligned by circumferentially spaced-apart tabs  80  formed on plate  68  and circumferentially spaced-apart slots  82  formed in plate  66  which closely receive tabs  80 .  
         [0069]     With the construction shown in the drawings, planar surface  68   a  of plate  68  cooperates with capillary  78  to form a fluid flow passageway through which fluid can controllably flow from reservoir  44  into the passageway  72  formed and stem  70 . By controlling the length and depth of capillary  78 , the rate of fluid flow flowing outwardly of outlet  78   b  can be precisely controlled. In this regard, it is to be understood that the capillary  78  of the flow rate control means can take several forms and be of various sizes depending upon the end use of the fluid delivery device.  
         [0070]     The bonding material or adhesive used to bond together plates  66  and  68  may be of the thermo-melting variety or of the liquid or light-curable variety. When thermo-melting adhesives are used, the adhesive material is melted into the two opposed surfaces, thereby inter-penetrating these surfaces and creating a sealed channel structure. When liquid-curable bonding materials, or adhesives, and light-curable bonding materials are used, the adhesives may be applied to one of the surfaces of one of the plates. Subsequently, the other surface is brought into contact with the coated surface and the adhesive is cured by air exposure or via irradiation with a light source. Liquid-curable bonding materials or adhesives may be elastomeric (e.g., thermo-plastic elastomers, natural or synthetic rubbers, polyurethanes and silicones). Elastomeric bonding materials may or may not require pressure to seal the channel system. They may also provide closure and sealing to small irregularities in the opposed surface of the channel system.  
         [0071]     It should also be understood that alternate bonding techniques such as sonic welding and laser thermal bonding techniques can also be used to bond together plates  66  and  68 .  
         [0072]     Connected to stem portion  70  of the rate control assembly  64  is the fluid delivery means of the invention. This latter mean comprises an elongated delivery line  82  having an inlet end  82   a  and an outlet end  82   b . A conventional luer assembly  84  is affixed proximate outlet  82   b . A line clamp  86  and a gas vent assembly  88 , both of conventional construction, are disposed between the inlet and outlet ends of delivery line  82  ( FIG. 1 ). As best seen in  FIG. 6 , the inlet end of the delivery line is telescopically received within an enlarged diameter portion  70   a  of stem portion  70  and is affixed thereto as by adhesive bonding.  
         [0073]     Filling of reservoir  44  with a selected beneficial agent, or medicinal fluid, is accomplished by filling means which here comprises a septum assembly  92  which is connected to base  32  in the manner shown in  FIGS. 6 and 7 . Septum assembly  92  includes a pierceable septum  94  which is pierceable by the cannula of a conventional syringe (not shown). Communicating with the cavity  93 , which holds septum  94 , is a fluid flow passageway  96 , which, in turn, communicates with one of the earlier described micro-channels  37  that terminates in an outlet port  98  that communicates with inlet  46  of reservoir  44 . With this construction, medicinal fluid can be introduced into reservoir  44  using a conventional syringe. Alternatively, the fill means can comprise a luer fitting or any other suitable fluid interconnection of a character well known to those skilled in the art by which fluid can be controllably introduced into reservoir  44  to cause expandable bellows  50  to move into its expanded configuration as shown in  FIG. 7 .  
         [0074]     As best seen in  FIGS. 6, 7  and  8 , a cover  100  is superimposed over base assembly  30  and functions to enclose spring  52  and bellows  50 . Cover  100  includes venting means comprising a vent port  102  formed in the upper wall of the cover for venting gases contained within cover  100  to atmosphere during the expansion of bellows  50 .  
         [0075]     During filling of reservoir  44 , which is accomplished in the manner previously described, the fluid being introduced into the reservoir under pressure via septum  92  will cause bellows  50  to move into the expanded configuration shown in  FIG. 7 . As the bellows is thus distended, a cover  50   a , which covers bellows  50  ( FIG. 8 ), will engage the yieldably deformable finger-spring members  52  causing the fingers to move from the at rest configuration shown in  FIG. 6  toward the deformed configuration shown in  FIG. 7 . As the fingers are thusly deformed, internal stresses will be formed in the fingers tending to return them to the less distended starting configuration shown in  FIG. 6 . As this occurs, fingers  52  will exert forces on the bellows  50  which will controllably move it toward its starting configuration shown in  FIG. 6 . As bellows  50  moves toward its starting configuration it will exert a fluid-expelling pressure on the fluid contained within the reservoir causing the fluid to be controllably forced into the rate control means of the invention via reservoir outlet  46 .  
         [0076]     During the fluid delivery step described in the preceding paragraph, fluid will flow from reservoir  44 , through outlet  46 , through capillary  78  of the flow control means, into fluid passageway  72  of stem  70  and finally into the delivery line  82  of the infusion means of the invention.  
         [0077]     Referring to  FIGS. 13, 17A ,  17 B,  17 C  17 D and  17 E it is to be noted that various types of alternate spring configurations these shown are suitable for use as the stored energy source of the invention. More particularly,  FIGS. 13 through 16  illustrate alternate forms of finger-springs that can be used, while  FIGS. 17A, 17B ,  17 C  17 D and  17 E depict a number of different types of springs that are suitable for use as the stored energy source of the invention.  
         [0078]     In considering the various spring configurations shown in the drawings, it is to understood that, springs are unlike other machine/structure components in that they undergo significant deformation when loaded and their compliance enables them to store readily recoverable mechanical energy.  
         [0079]     With respect to the specific spring configurations shown in  FIG. 17A through 17E  of the drawings, the following discussion amplifies the descriptive notations in this drawing.  
         [0000]     Compression Springs:  
         [0080]     Compression springs are open-wound helical springs that exert a load or force when compressed. They may be conical or taper springs, barrel or convex, concave or standard cylindrical in shape. Further, they may be wound in constant or variable pitch. The ends can be closed and ground, closed but unground, open and unground and supplied in alternate lengths. They also can include a configuration where a second compression spring of similar or different performance characteristics which can be installed inside the inside diameter of their first compression spring, i.e., a spring-in-a-spring.  
         [0081]     Many types of materials can be used in the manufacture with compression springs including: Commercial Wire (BS5216 HS3), Music Stainless Steel, Phosphur Bronze, Chrome Vanadium, Monel 400, Inconel 600, Inconel X750, Nimonic 90: Round wire, Square and Rectangular sections are also available. Exotic metals and their alloys with special properties can also be used for special and applications; they include such materials as beryllium copper, beryllium nickel, niobium, tantalum and titanium.  
         [0082]     Compression springs can also be made from plastic including all thermo-plastic materials used by custom spring winding service providers. Plastic springs may be used in light-to-medium duty applications for quiet and corrosion-resistant qualities.  
         [0000]     Wave Spring:  
         [0083]     Multi-wave compression springs, an example of which is shown as “F” in  FIG. 17  are readily commercially available from sources, such as the Smalley Company of Lake Zurich, Ill. As previously discussed, such springs operate as load-bearing devices. They can take up play and compensate for dimensional variations within assemblies. A virtually unlimited range of forces can be produced whereby loads built either gradually or abruptly to reach a predetermined working height. This establishes a precise spring rate in which load is proportional to deflection, and can be turned to a particular load requirement.  
         [0084]     Typically, a wave spring will occupy an extremely small area for the amount of work it performs. The use of this product is demanded, but not limited to, tight axial and radial space restraints.  
         [0000]     Disc Springs:  
         [0085]     Disc springs I, J, K, and L of  FIG. 17  compare conically shaped annular discs (some with slotted or fingered configuration) which when loaded in the axial direction, change shape. In comparison to other types of springs, disc springs product small spring deflections under high loads.  
         [0086]     Some examples of the disc-shaped compression springs include a single or multiple stacked Belleville washer configuration as shown in G and H of  FIG. 17 , and depending on the requirements of the design (flow rate over time including bolus opportunity) one or more disc springs can be used and also of alternate individual thicknesses. Alternate embodiments of the basic disc spring design in a stacked assembly can be also utilized including specialty disc springs similar to the Belleville configuration called K disc springs manufactured by Adolf Schnorr GMBH of Singelfingen, Germany, as well as others manufactured by Christian Bauer GMBH of Welzheim, Germany.  
         [0087]     Disc springs combine high energy storage capacity with low space requirement and uniform annular loading. They can provide linear or non-linear spring loadings with their unique ability to combine high or low forces with either high or low deflection rates. They can be pre-loaded and under partial compression in the design application.  
         [0088]     All these attributes, and more, come from single-component assemblies whose non-tangle features (when compared to wire-wound, compression springs) make them ideal for automatic assembly procedures.  
         [0089]     With respect to the various springs discussed in the preceding paragraphs, it is to be understood that many alternate materials can be used in the design and application of disc springs and include carbon steel, chrome vanadium steel, stainless steel, heat resistant steels, and other special alloys such as nimonic, inconel, and beryllium copper. In some special applications, plastic disc springs designs can be used.  
         [0090]     It should be further observed that, in comparison to other types of springs, disc springs produce small spring deflections under high loads. The ability to assemble disc springs into disc spring stacks overcomes this particular limitation. When disc springs are arranged in parallel (or nested), the load increases proportionate to the number of springs in parallel, while when disc springs are arranges in series (alternately) the travel will increase in proportion to the number of springs serially arranged. These assembly methods may be combined in use.  
         [0091]     One special feature of the disc spring is, undoubtedly, the fact that the load/deflection characteristic curve can be designed to produce a wide variety of possibilities. In addition to practically linear load/deflection characteristic curves, regressive characteristics can be achieved and even disc springs which exhibit increasing spring deflection while the corresponding disc spring load is decreasing are readily available.  
         [0092]     Slotted disc springs present a completely different case. Slotting changes the load/deflection characteristic of the single disc spring, providing larger spring deflections for greatly reduced loads. The slotted part is actually functioning as a series of miniature cantilever arms. In some cases the stacked, slotted disc spring, as shown in the clover dome design, will also produce a non-linear, stress strain curve with a noticed flat region (force/deflection). Application and use of this type of spring operating in this region will provide a near constant force between 15% and 75% of compression.  
         [0093]     Turning next to  FIGS. 18 through 29 , an alternate form of the device of the invention for use in intravenous infusion of medicinal fluid into a patient is there shown and generally designated by the numeral  108 . This alternate form of the invention is similar in many respects to that shown in  FIGS. 1 through 16  and like numerals are used in  FIGS. 18 through 29  to identify like components. The main difference between this latest embodiment of the invention and that previously described resides in the provision of novel fluid consumption indicator means for accurately determining the amount of fluid remaining within the reservoir of the device. The details of the construction and operation of this novel fluid consumption indicator means will be described in greater detail in the paragraphs that follow.  
         [0094]     As best seen by referring to  FIGS. 18, 19  and  20 , the device of this latest form of the invention comprises a base assembly  30  that is substantially identical in construction to the base assembly of the previously described apparatus of the invention. More particularly, the base assembly  30  here includes a base  32  having an upper surface  34 , including a central portion  34   a  and peripheral portion  34   b  circumscribing central portion  34   a  ( FIG. 20 ). As illustrated in  FIGS. 20 and 21 , central portion  34   a  is provided with a central counterbore  34   c , which houses a filter  35  and is also provided with circuitous, precisely formed fluid flow micro-channels  37  (See  FIG. 10 ) of the character described in connection with the embodiment of  FIGS. 1 through 16 . Base  32  is provided with a lower surface  36  which is engageable with the patient when the device is foam-taped or otherwise removably affixed to the patient. Formed within base  32  is a channel  38  and a pair of central counter-bores  40  and  42  ( FIGS. 21 and 22 ), the purpose of which will presently be described.  
         [0095]     Forming an important aspect of the apparatus of the present invention is a bellows  50  for forming in conjunction with the central portion of  34   a  of base  32 , a reservoir  44  having an outlet  46  ( FIG. 21 ). Bellows  50  is superimposed over base  32  and is held and position by a capture ring  51 . As illustrated in  FIG. 21 , the expandable bellows can be expanded from a first position shown in  FIG. 20  to a second position shown in  FIG. 21  as a result of pressure imparted by fluids “F” introduced into reservoir  44  via the fill means of the invention which is identical in construction and operation to that previously described. In this latest embodiment of the invention, the stored energy means further comprises a plurality of circumferentially spaced-apart, yieldably deformable finger-spring members  52  which are operably associated with bellows  50  ( FIGS. 21 and 22 ). Each of the finger-spring members  52  is yieldably deformed in the manner shown in  FIG. 21  by movement of the expandable bellows toward the second position shown in  FIG. 21 . As the bellows  50  expands into the second position ( FIG. 21 ) internal stresses are formed within the spring members, which forces tend to controllably return the expandable bellows to its first position ( FIG. 20 ). As the bellows moves toward its first position, fluid contained within reservoir  44  will be urged to flow outwardly of the reservoir through outlet  46  and toward the flow rate control means of the invention that is identical in construction and operation to that previously described herein.  
         [0096]     Connected to stem portion  70  of the rate control assembly  64  is the fluid delivery means of the invention which is substantially identical in construction and operation to that described in connection with the embodiment of the invention illustrated in  FIGS. 1 through 16 . As illustrated in  FIG. 20 , the inlet end of the delivery line is telescopically received within an enlarged diameter counter-bore portion  70   a  of stem portion  70  and is affixed thereto as by adhesive bonding.  
         [0097]     Filling of reservoir  44  with a selected beneficial agent, or medicinal fluid, is accomplished in the manner described in connection with the embodiment of the invention illustrated in  FIGS. 1 through 16  by filling means of the character previously described.  
         [0098]     As best seen in  FIGS. 20 and 21 , a cover  110  is superimposed over base assembly  30  and functions to enclose spring  52  and bellows  50 . Cover  110  includes a generally dome-shaped upper portion  110   a  having venting means comprising a vent port  112  for venting gases contained within cover  110  to atmosphere during the expansion of bellows  50 . Cover  110  also includes a peripheral portion  110   b  having a viewing window assembly  114  formed thereon. Viewing window assembly  114 , which comprises a part of the fluid consumption indicator means of the invention, comprises a housing  114   a  within which a substantially transparent viewing window  116  is mounted. Also forming a part of the fluid consumption indicator means is an indicator member  118  that is superimposed over expandable bellows  50  in the manner shown in  FIGS. 20 and 21  and is movable between a first and second position. As best seen by referring also to  FIG. 22  of the drawings, indicator member  118  comprises a generally circular-shaped top wall  118   a  and a downwardly extending peripheral portion  118   b . Extending outwardly from top wall  118   a  is an indicator segment  120  having a downwardly extending indicator flange  122 . For a purpose presently to be described, in certain forms of the invention indicator flange  122  is provided with indicating indicia  124  ( FIG. 25 ). Indicating indicia  124  can take several forms, including a plurality of vertically spaced-apart indicator bars  126  of the character illustrated in  FIGS. 34 and 36  of the drawings. The indicating indicia  124  can also take the form of a generally circular-shaped pattern  128  having vertically spaced-apart crossbars  130  (see  FIGS. 30 and 32 ). Preferably, the indicating indicia  124  are brightly colored in easily distinguishable colors, such as red or blue. In the manner illustrated in  FIGS. 26 and 28  of the drawings, indicating indicia  136  may also be provided on viewing window  116 . Indicia  136  can also be of several forms including the plurality of vertically spaced-apart horizontal indicator bars  136  illustrated in  FIGS. 26 and 28  of the drawings. When the indicating indicia  136  are formed on the viewing window, the indicator flange  122  is preferably of a solid, easily distinguishable color, such as red or blue.  
         [0099]     During filling of reservoir  44 , which is accomplished in the manner previously described, the fluid being introduced into the reservoir under pressure via septum  92  will cause bellows  50  to move into the expanded configuration shown in  FIG. 21 . As the bellows is thus distended, indicator member  118 , which covers bellows  50 , will engage the yieldably deformable finger-spring members  52  causing the fingers to move from the at rest configuration shown in  FIG. 20  toward the deformed configuration shown in  FIG. 21 . As the fingers are thusly deformed, internal stresses will be formed in the fingers tending to return them to the less distended starting configuration shown in  FIG. 20 . As this occurs fingers  52  will exert forces on the bellows  50  which will controllably move it toward its starting configuration shown in  FIG. 20 . As bellows  50  moves toward its starting configuration it will exert a fluid-expelling pressure on the fluid F contained within the reservoir causing the fluid to be controllably forced into the rate control means of the invention via reservoir outlet  46 . During the fluid delivery step, fluid will flow from reservoir  44 , through outlet  46  via filter  35 , through the capillary of the flow control means, into fluid passageway  72  of stem  70  and finally into the delivery line  82  of the infusion means of the invention. It is to be appreciated that, as before, various types of alternate spring configurations, such as those shown in  FIGS. 17A through 17E  are suitable for use as the stored energy source of the invention.  
         [0100]     As the fluid is expelled from the fluid reservoir  44 , indicator member  118  will move from the position shown in  FIG. 20  toward the position shown in  FIG. 21 . When the indicator member is in the reservoir-filled position shown in  FIG. 21 , flange  122  of the indicator member resides immediately behind window  116  and, as indicated in  FIGS. 26 and 27 , each of the bars  136  formed on window  116  will appear in the color provided on the outer surface of flange  122 . For example, if the flange is colored red, all four of the bars  136  will appear to be red indicating that the reservoir is full. However, as the fluid is expelled from the reservoir, flange  122  will move gradually downward within the housing into the position shown in  FIGS. 28 and 29  of the drawings. As the flange moves downwardly, initially the upper bar  136  will become clear because the flange  122  will no longer be behind the upper bar. Similarly, as the flange continues to move downwardly, each of the bars  136  will sequentially become clear until the flange reaches the position shown in  FIG. 29  at which point the reservoir  44  is empty. As each bar sequentially becomes clear, the extent of the consumption of the fluid within the reservoir becomes readily apparent to the caregiver.  
         [0101]     In the form of the invention shown in  FIGS. 30 through 33 , wherein the indicia is imprinted or otherwise affixed to the flange  122 , when the reservoir  44  of the device is full, the caregiver will see all three brightly colored bars  130  of the indicia. However, as the fluid is expelled from the reservoir, flange  122  will move gradually downward within the housing into the position shown in  FIGS. 32 and 33  of the drawings. As the flange moves downwardly, initially the lower bar  130  of the indicia imprinted on the flange will disappear because lower bar on the flange  122  will no longer be visible through the viewing window. Similarly, as the flange continues to move downwardly each of the bars  130  will sequentially disappear until the flange reaches the position shown in  FIG. 32  at which point the reservoir  44  is empty. As each bar sequentially disappears and the viewing window becomes progressively more clear, consumption of the fluid within the reservoir becomes readily apparent to the caregiver.  
         [0102]     In the form of the invention shown in  FIGS. 34 through 37 , an angled-mask  116   a  partially obscures the window  116  so that only the right-hand portion of the indicia imprinted or otherwise affixed to the flange  122  is visible to the caregiver. With this construction, when the reservoir  44  of the device is full, the caregiver will see the right-hand portion of all four of the brightly colored bars  126  of the indicia. However, as the fluid is expelled from the reservoir, flange  122  will move gradually downward within the housing into the position shown in  FIGS. 36 and 37  of the drawings. As the flange moves downwardly, initially the lower bar  126  of the indicia imprinted on the flange will disappear because lower bar on the flange  122  will no longer be visible through the viewing window. Similarly, as the flange continues to move downwardly each of the right-hand portions of the bars  126  will sequentially disappear until the flange reaches the position shown in  FIGS. 36 and 37  at which point the reservoir  44  is empty. As each bar sequentially disappears and the viewing window becomes progressively more clear, consumption of the fluid within the reservoir becomes readily apparent to the caregiver.  
         [0103]     Having now described the invention in detail in accordance with the requirements of the patent statues, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.