This invention relates generally to pressurized fluid dispensers and more specifically to pressurized fluid dispensers using an elastic bladder to pressurize the fluid contents of the bladder.

One application for a bladder-type dispenser is for infusing liquid medications and other fluids into the human body. When infusing fluids into the human body, generally a certain flow rate is prescribed by a physician. Presently a drop counter is used to accomplish this task. Drop counters typically comprise a bottle containing a medication in fluid form, which is hung at a height above the patient. The flow rate is adjusted by adjusting a flow control valve until the appropriate number of drops pass out of the valve over a period of time.

The drop counter apparatus for dispensing fluids has several shortcomings. The most prominent shortcoming is inaccuracy in the flow rate of the fluid into the body. The bottle can be hung at various heights in relation to the body and, as the bottle empties, the level of the fluid in the bottle changes. Both of these factors change the total head of the system, which, in turn, changes the flow rate of the system. In addition, a different surface tension and viscosity are associated with each fluid. The surface tension and viscosity determine the size of the drops formed by the fluid. The variation in total head and the different sizes of drops can result in inaccuracies of 15 to 20% above or below the prescribed flow rate at any given time.Drop counters also have other disadvantages in both field and hospital applications. Whenever a patient has to be moved the drop counter must also be moved. Often, an additional person must ^* carry the bottle of fluid or medication during the patient's transport.

Because of the inaccuracies associated with the drop counters, other means have been used in an attempt to infuse liquid medications into the body. Pumps increase the accuracy of the flow rate of fluid into the body; however, the motion of the fluid as it is pumped interferes with the systolic motion of the blood stream. In other words, a pump injects fluid at an uneven flow rate.

Pressurizing the fluid has been looked to as a solution. However, prior art attempts at pressurization have met with problems as well. Gas cannot be used with the fluid, since the gas and fluid may react with each other, and it is vitally important that the medication not react with other substances. Furthermore, gas pressurization also runs the risk of inadvertently injecting gas into a person's body, which can be fatal.

Pressurization by use of an expandable bladder has been attempted in the past but has encountered problems. A prominent problem of the previous attempts to use a bladder has been a variation in flow rates as the bladder nears the empty condition. The pressure drops drastically as the bladder empties and, as a result, the flow rate also drops. Several of the prior art devices have attempted to address this problem; however, they have had limited success.

The device disclosed in U.S. Patent No. 3,506,005, and an improvement on that device disclosed in U.S. Patent No. 3,698,595, use a bladder mounted axially on a mandrel. These devices not only require a specially manufactured bladder but also are difficult to assemble since mounting the bladder on a mandrel requires tedious alignment of the bladder with the mandrel. The valve mechanism necessary to control the flow rate out of the bladder in those devices is also very complex. The valve requires a number of specially manufactured parts and also uses a metal spring to maintain the valve in a closed

position. The metal spring is not isolated from the fluid and thus a chemical reaction, such as oxidation, may alter the fluid flowing past the spring. Furthermore, the valve allows variation in the flow rates as the pressure drops. The device disclosed in U.S. Patent No. 3,907,169, uses a bladder mounted on the outside surface of a pivoting curved spatulate member. This device eliminates the difficulties of aligning the bladder upon a mandrel during manufacture; however, the pivoting of the spatulate member causes other problems. Since the spatulate member can move as the bladder is filled or emptied, the bladder must be attached to the spatulate member. The bladder has to be specially formed to accommodate specially formed clips for attaching the bladder to the spatulate member. The device uses a complex valve similar to that disclosed in the previous patents. The problems associated with the valve in the prior patents are also associated with the device described in this patent.

In modern medicine, and indeed in other fields, there is a demand for inexpensive, accurate and disposable fluid dispensers. In medicine, in particular, it will be appreciated that, for reasons of contamination from one fluid to another and for the cost involved in trained personnel spending time manipulating dispensers, it is very desirable to have a relatively simple, disposable dispenser, or at least one whose fluid contacting parts are easily separable for disposal.

Thus, there has been a need for a bladder-type dispenser that can pressurize a fluid and maintain a substantially constant flow rate as the bladder empties, is easily manufactured and assembled, and is easy to use. In addition, there is a need for a valve system on a bladder-type dispenser having simple, reliable operation and having no metal components in contact with the fluid inside the dispenser. Further, there is a need for a dispenser which is relatively inexpensive and disposable

at least in respect of those parts which contact the fluid.

Summary of the Invention

The bladder-type dispenser of the present invention cures the shortcomings discussed above. The bladder-type dispenser comprises a bladder made of an elastomeric material and having an open end and a closed end. The dispenser also includes a bladder mounting structure including a fixed structural member having a convex curved surface and mounting elements for fixing the two ends of the bladder in relation to the curved surface, so that the bladder is stretched and prestressed along that curved surface. Whereas the prior art devices typically achieve a flow accuracy of about _+ 20%, the dispenser of this invention achieves about _+ 10%.

According to the invention there is provided a bladder for a fluid dispenser, in which the bladder is to be stretched over a surface to pressurize the bladder for dispensing said fluid, said bladder comprising: an elongate, elastic body, said body being closed at one end and having an outlet at the other end; first and second means for readily and disengageably attaching said closed end and said outlet end, respectively, in said dispenser for stretching said bladder over said surface; and valve means, at said outlet end, normally sealing said outlet end.

Preferably, the first and second attachment means each comprises a first portion for engagement in slots or openings in a dispenser housing and a second portion which is enlarged so as not to pass through the slots to thereby retain each end of the bladder in the relevant slots for

^' stretching over the prestressing surface. In this embodiment, the means for attaching the outlet end of the bladder preferably comprises a mounting element which includes a flange for engagement with an opening in a free edge of the housing in the dispenser. The flange may be formed by a groove around the mounting "element so that

that element snugly slides into the opening and provides a convenient method of removably attaching the outlet end of the bladder in the dispenser. The bladder of this invention is designed for disposability and great convenience in use so that it can be easily stretched over the convex surface and easily removed therefrom for disposal. In summary, this is achieved by providing each end of the bladder with fittings which will engage slots at either end of the curved surface. The outlet valve in the bladder of this invention is preferably a one-way valve which is preferably openable by a probe, such as a duckbill valve. Preferably, the outlet end mounting element in the bladder of this invention is provided with both an outlet opening and an inlet opening, each having such valves so that the bladder may be filled without disturbing the outlet opening which may be sealed, ^' for example, at the outlet surface on the mounting element. The bladder is preferably a tubular ' length of elastomeric material, which may be extruded or molded.

In another embodiment of this invention, there is provided a bladder assembly comprising the bladder of this invention in combination with a structural member including the convex surface over which the bladder is stretched. The structural member may be attached to the internal surface of a main housing in a dispenser of this invention or that member may form part of an auxiliary housing which fits within the main housing to form the dispenser. The advantage of the bladder and auxiliary housing combination is that it forms an assembly which may be disposed of without the necessity of detaching the bladder if so desired.

Preferably, the bladder of this invention includes means for indicating the amount of fluid in the bladder. This preferably comprises an elongate member ^" hingeably attached to the outlet mounting element and biased towards

the bladder so that as the amount of liquid in the bladder varies the indicator will move with the bladder. Typically, the housing has a window marked with volume graduations and the movement of the indicator inside the housing can be observed and the volumes read off by alignment with the relevant graduation.

In a further embodiment of this invention, the dispenser further comprises a flow controller which is detachable from the bladder and which includes a probe for opening the outlet valve in the bladder. Preferably, the probe in the flow controller is the inlet passage to the controller which is in fluid communication via a flow control chamber to an outlet from the flow controller. The flow control chamber preferably has a frusto-conical shape and accepts a correspondingly shaped shut-off element which can be driven in either direction along the axis of that chamber by means of a control dial on the outside of the flow controller so as to regulate the flow of liquid by varying the cross-sectional flow- area of che fluid passage through the flow control chamber. The control for the movement of the shut-off element is outside the fluid flow passage so that the fluid being dispensed does not contact the control mechanism. Brief Description of the Drawings Some preferred embodiments of the invention are illustrated in and by the accompanying drawings, in which like reference numerals indicate like parts, where convenient.

Figure 1 is a perspective view of an assembled bladder-type dispenser of the invention;

Figure 2 is an exploded perspective view of one bladder-type dispenser of the invention, with the dispenser opened to show the bladder inside in its prestressed, empty state; Figure 3 is a cross-sectional view of one embodimenc of the flow controller of the dispenser of the invention;

Figure 4 is a cross-sectional view of a mounting element for the outlet end of the bladder of this invention and the outlet valve for the bladder;

Figure 5 is a view, partially in cross-section, showing the attachment of the bladder in one embodiment of this invention onto the prestressing surface;

Figure 6 is a perspective view of a dual flow dispenser constructed according to the invention;

Figure 7 is a perspective view of an alternative, gear-actuated plate flow controller for use in the fluid dispenser of the invention;

Figure 8 is a plan view of the alternative flow controller for the dispenser of this invention;

Figure 9 is a view of the closed end of the bladder in an alternative embodiment of the invention;

Figure 10 is a perspective view of a removable mounting for the bladder-type dispenser.

Figure 11 is an exploded, perspective view of an alternative dispenser of this invention; Figure 12 is an exploded, perspective view of a preferred inlet/outlet assembly of the bladder of this invention;

Figure 13 is a side view of a bladder and bladder support assembly according to this invention, with the bladder stretched over the prestressing surface;

Figure 14 is a partial, cross-sectional view of the flow controller housing and flow control knob shown in Figure 11, and taken in the direction of arrows 14 in that Figure; Figure 15 is a cross-sectional view of the flow shut- off element in place on the flow controller shown in Figure 11 ;

Figure 16 is an exploded, perspective view of another bladder assembly and dispenser of this invention; and Figure 17 is an exploded, perspective view of a further bladder assembly and dispenser of this invention.

Detailed Description

Referring to Figure 1 , a bladder-type dispenser 1 of the invention is shown as it would be typically used. A line of microbore tubing 2 connects an outlet of the bladder-type dispenser 1 and an injection needle 3. The needle 3 may be inserted in a patient's body. Liquid medication passes through the tubing 2 and the needle 3 into the patient. Nevertheless, dispensing medications into the human body is just one possible use of the bladder-type dispensers of the invention. The dispensers of the invention may also be used to dispense a variety of other liquid substances, including industrial chemicals, foodstuffs, or cosmetics in industrial and consumer applications. Referring to Figures 1 and 2, the bladder-type dispenser 1 comprises a bladder cassette or housing 4 and a mating flow controller 5. The bladder cassette 4 comprises a main housing -6, a cover 7, and a bladder assembly 8. In the preferred embodiment of the bladder cassette 4, shown in Figure 2, the main housing 6 is a substantially rectangular box. Main housing 6 comprises a substantially rectangular back 9 with four rectangular sidewalls 10, 11, 12, and 13, attached at right angles along the four edges of the back 6. Attached to the free edge of one sidewall

13 is a hinged cover 7. The substantially rectangular cover 7 is sized to fit the main housing 6 to form a closed container. A thin, flexible plastic hinge 14 preferably connects the cover 7 to the sidewall 13. The cover 7 is held closed by a latch 15 on the long free edge of the cover 7. A lip 16 on the outer edge of the opposite sidewall 11, and at right angles to that sidewall 11, engages a flexible locking tooth 17 on latch 15. The locking tooth 17 is positioned on the- cover 7 so that a notch 18 in the locking tooth 17 engages the lip 16 on the main housing 6.

It is apparent to one skilled in the art that a number of other arrangements for attaching the cover 7 to the housing 6 can be used. For example, a sliding cover could replace the hinged cover 7. The hinge 14 and lock 15 of the preferred embodiment just described would be replaced with a set of grooves in the sidewalls 10, 11, 12, 13 to receive a sliding cover. For example, the bottom wall 12 can be provided with a slot spaced a small distance from its free edge and extending across the width of the housing. On each adjoining sidewall 11, 13 would be a groove aligning with that slot. A similar groove in the top wall 10 would align with the grooves in the sidewalls 11 and 13. The cover of this other embodiment would be substantially rectangular and sized to fit snugly within the grooves in the sidewalls 10, 11, 13 and the slit in the bottom sidewall 12. When the cover is fully inserted a box-like container or cassette 4 is formed.

The top wall 10 of the main housing 6 shown in Figure 2 has a mounting portion 19 for firmly holding the top portion of the bladder assembly 8. The preferred mounting

19 is a U-shaped opening 19 extending from the free edge

20 of the top wall 10 toward the back 9. Preferably, the U-shaped opening 19 passes through about three-fourths of the front-to-back width of the top wall 10. The opening 19 is located near one corner of the box-like container. Around the perimeter of the opening 19 on the interior face of the top wall 10 is preferably an undercut 21.

Located on the exterior surface of the top wall 10 are preferably a pair of vertical aligning pins 22. The aligning pins 22 are preferably located about half-way between the U-shaped opening 19 and the most distant short edge of top wall 10. The pins 22 are preferably cylindrical in shape. To provide for solid placement of the alignment pins 22, a reinforcing block (not shown) is preferably attached to the interior surface of the top wall 10 below the pins 22.

Extending into the interior of the main housing 6 and along the interior surface of the sidewall 13 is a fixed structural element, 23, one side of which forms a convex curved prestressing surface 24. The prestressing structural element 23 has a first end 25 and a second end 26. The prestressing surface 24 is approximately the length of the sidewall 13 and is convex to the sidewall 13. The first upper end 25 of the prestressing element 23 is firmly attached to the interior surface of the sidewall 13 near the top of the housing 6. The second end 26 of the prestressing element 23 may be attached to the interior of the sidewall 13. Preferably the prestressing surface 24 is integrally formed with the housing 6. For added structural integrity a support member 27 may be connected between the sidewall 13 and the prestressing surface 24 a short distance from the second end 26 to brace structural element 23. The prestressing element 23 may be connected along its length to the back 9 of the housing 6. The prestressing structural element 23 preferably extends relatively near the sidewall 13 so as to take up a minimum of space in the interior of the housing 6. The convex curved prestressing surface 24 has its top end substantially in vertical alignment with the opening 19 in top wall 10.

A second, lower bladder mounting 28 is located near the second end 26 of the curved prestressing surface 24, the end remote from the opening 19 in top wall 10. The second bladder mounting 28 receives the closed end of the bladder 29. A lower bladder mounting 28, preferably comprises a slot 28, as shown in Figure 2, preferably formed in the prestressing element 23 hear its second end 26. This slot 28 may extend across the full width of the prestressing element 23. The edges of the prestressing element 23 at the slot 28 are rounded to prevent damage to the bladder. Alternatively, the lower end 26 of the

prestressing element 23 may terminate a short distance from the sidewall 13, leaving a space forming the slot 28 between the lower end 26 of the prestressing element 23 and the sidewall 13. The bladder assembly 8 is positioned within the main housing 6 in the embodiment shown in Figure 2. The bladder assembly 8 comprises a generally tubular, elastomeric bladder 29 having an outlet end 30 and a closed end 31. Bladder 29 may be molded or extruded. The upper, outlet end 30 has a mounting element 32 and the closed, lower end 31 has a mounting element 33.

Referring now to Figure 4, a preferred form of upper mounting element 32 is shown. Mounting element 32 preferably comprises a locking element 34 and a valve 35. The mounting element 32 holds the bladder 29 securely, by being gripped by locki g element 34 and provides the valve 35 for controlling the flow of fluid into and out of the bladder 29. The mounting element 32 also' holds the top end of the bladder assembly 8 firmly to the top wall 10 of the main housing 6 by interaction with the opening 19. The mounting element 32 is shaped to fit snugly into the U-shaped opening 19 in the top wall 10 of the housing 6, as shown in Figure 2.

In Figure 4, the mounting element 32 is generally tubular in shape, with a wide flange 36 on one end. The opening 37 passing through the mounting element 34 may have two different inside diameters. A ledge 38 is formed where the diameter of the opening changes. An annular groove 39 is formed below flange 36 and is centered on flange 36. The depth of the groove 39 is preferably uniform. The outer diameter of the groove 39 is just slightly less than the width of the U-shaped opening 19 in the housing 6, while the outer diameter of the flange 36 is greater than the width of the opening 19. The axial width of the groove 39 is also slightly greater than the thickness of the top wall 10 of the housing 6 less the

undercut 21 , so the lower rail of the flange 36 fits into the undercut 21. The dimension differences between flange 36 and its groove 39 of the mounting element 32, and the U-shaped opening 19 are small so the flange 36 snugly engages the opening 19 to hold the top of the bladder assembly 8 firmly in place.

Valve 35 is a one-way valve, such as a duckbill valve, which is known in the art. The two flaps of the duckbill valve 35 point away from the flange 36 of the mounting element 32. The flaps can be separated when an elongate probe member, such as a tube, is inserted through the valve in the direction of the flaps. When the valve 35 is so opened, fluid can pass into or out of the bladder 29. Until such an elongate member opens the duckbill valve 35 the pressure of the fluid in a full bladder 29 holds the flaps of the valve together, preventing passage of any fluid from the bladder.

Other apparatus can be used to prevent the flow of fluid through the mounting element 32 prior to its desired use, while still allowing easy opening when desired. For example, an elastomeric disk of self-sealing, rubber-like material can be used in place of the duckbill valve.

The valve 35 in Figure 4 is positioned adjacent the lower edge of the mounting element 32, with a short extension of the mounting element 32 and its central opening extending into the valve, and forming a ledge 40 against which the valve 35 may seat firmly.

The molded or extruded elastomeric bladder 29 is tubular in shape with an open end and a closed end at the closed end is an enlarged portion 33. The embodiment of the bladder 29 shown in Figure 2 is molded with a closed end forming a necked-down portion 41 and an enlarged solid ball end 33. The necked-down portioιr ^' 41 and enlarged ball end 33 of this embodiment of the bladder 29 are seen in greater detail in Figure 5.

An alternative embodiment of the bladder 29 is shown in Figure 9, where the bladder is molded or extruded as a straight tube. After the tube is cut to the appropriate length, one end of the tube is folded over and held firmly with a clamp 42 to close off the end of the tube, forming the closed end of the tube with an enlarged portion 33.

The locking element 34 of the valve mounting element 32 of the preferred embodiment (Figure 4) is preferably a thin-walled plastic clamp having a set of inter-locking teeth. After the open end of the bladder 29 is stretched over the smaller end of the mounting element 32 the locking element 34 is clamped on, over the open end of bladder 29. The unflanged end of the mounting element 29 and the locking ring 34 sandwich the open end of bladder 29 to provide a tight seal and a snug fit between the bladder 29 and the mounting element 32. In some instances it may be desired to have the section of the mounting element 32 around which the clamp 34 is placed be slightly, longer in the axial direction than the width of the clamp 34, and to provide a slight flare or rim on the end of the mounting element so the clamp 34 clamps down on a neck of smaller diameter than the end of the valve mounting element to provide added security against the bladder 29 slipping off the mounting element. The bladder's unstressed length is less than the distance from the mounting element 32, when attached at the first mounting 19, over the prestressing surface 24 to the second mounting 28, so the bladder is stretched when the mounting assembly 32 is attached to the opening 19 and the closed end is attached to the second opening 28, as will be discussed below.

Assembly of the bladder cassette 4 in Figure 2 will now be explained. The bladder assembly 8 is placed in the housing 6. The enlarged end 33 of the bladder 29 is placed in the space 28 in the prestressing surface 24 in Figure 2, or between surface 24 and the sidewall- 13, as

shown in Figure 5. The necked-down portion 41 of the bladder 29 passes through the slot 28. The slot 28 is sufficiently narrow to prevent the enlarged end 33 of the bladder 29 from passing through slot 28. The edges of the slot 28 in the prestressing surface 24 are rounded to prevent tearing of necked down portion 41 of the bladder itself. The bladder 29 is then stretched over the smooth, convex curved prestressing surface 24 and the mounting element 32. is engaged with the U-shaped opening 19. When both ends of the bladder assembly 8 are fixed in the housing 6, the bladder 29 is stretched along the prestressing surface 24, and the bladder 29 is stressed under tension. The curve of the prestressing surface is such that the stretched bladder 29 follows the surface closely and smoothly.

The groove 39 on flange 36 of the mounting element 32 snugly engages opening 1 , and the resilient, elastomeric material of the bladder 29 produces a force normal to the

■ top wall 10 to pull. the upper rail of the flange 36 firmly against the top wall 10. The slot 28 near the second, lower end of the prestressing member firmly holds the closed end 31 of the bladder. The normal force produces a friction force to secure the mounting element 32 in the wall 10. After the bladder assembly 8 is mounted within the main housing 6, the cover 7 is closed to complete the cassette 4.

When the alternative bladder shown in Figure 9 is used, the assembly is generally the same. The enlarged end 33 of the bladder formed by folding over and clamping the end of the bladder tubing is inserted in the space between the prestressing surface 24 and the- sidewall 13. A section of bladder tubing adjacent the enlarged end 33 is placed in the slot 28. Again, the enlarged end 33 of the bladder is too large to pass through the slot 28, so the closed end of the bladder 29 is held firmly adjacent the lower end 26 of the prestressing surface 24. The

valve end of the bladder assembly 8 incorporating this alternative bladder may be identical to that shown and described above with reference to Figure 4, and the attachment of it to the housing 6 is as described above. The stretching of the empty bladder 29 stresses its walls so as to place its fluid contents under pressure even when there is little fluid in the bladder. This pressure in the nearly empty bladder helps to ensure a smooth, even flow of fluid when the bladder is coupled to an appropriate flow controller 5. The amount of prestressing, and thus the pressure imposed on the fluid to eject it as the bladder nears empty, can be varied by using bladders of different length. A shorter bladder will be under greater tension when it is stretched over the curved prestressing surface 24 than a longer bladder. This greater tension will translate into greater pressure on the fluid in the bladder.

The length of bladder may be chosen so as to dispense a known volume of liquid. The volume of the bladder may be from 5 to 1000 mis, for example 100, 250, 500, or 1000 mis .

The bladder 29 is sufficiently elastic that it does not rupture when it is so stretched, or when it is further stressed by filling with fluid. Preferably the bladder 29 should be sufficiently elastic that it can be filled to the point at which the bladder occupies virtually the entire interior of the cassette housing 6, except for the portion between the prestressing surface 24 and the sidewall 13. The flow controller 5 is removably attached to the top of the bladder cassette 4 to open- the valve 35 and to regulate the flow of fluid from the bladder 29 into the flow tube 2.

Referring to Figures 2 and 3, the flow controller 5 preferably comprises a housing 44 in the form of block having an opening or chamber 45 in it. The block 44

additionally includes a fluid passage through it comprising an inlet passage 46, an outlet passage 47, and a portion of the cavity 45. A shut-off element 48 fits into the chamber 45, a probe 49 is connected at the end of the inlet fluid passage 46, and a control mechanism 50 controls the shut-off element 48. The shut-off element 48 moves within the cavity 45 to control the cross sectional flow area of the fluid flow path through a portion of the cavity 45 from the inlet passage 46 to the outlet passage 47.

The control mechanism 50 is sealed from the fluid passage from the inlet passage 46 to the outlet passage 47 by sealing the shut-off element 48 in the cavity 45 so fluid flowing through the portion of the cavity 45 from the inlet 46 to the outlet 47 does not flow around the shut-off element 48 to the control mechanism 50. Thus, the control for the shut-off is provided outside the fluid flow passage and the -fluid being dispensed does not contact the control mechanism. The preferred shut-off element 48 includes a cylindrical portion 51 and a frusto-conical end portion 52. The larger base of the frusto-conical portion 52 abuts the cylindrical portion 51. On the cylindrical portion 51 , near the joint with the larger base of the frusto-conical end 52 is a shallow annular groove carrying a seal 53. The remaining exterior surface of the cylindrical portion 51 has outside threads 54.

The opening 45 extends to one end of block 44 in this preferred embodiment of the flow controller. The shape of chamber 45 in the block 44 corresponds to the shape of the shut-off element 48. The chamber 45 has a cylindrical portion 55 (Figure 3) and a frusto-conical portion 56. The cylindrical portion 55 of the chamber 45 extends through the block 44 to one of the end faces. The fluid passage through the block 44 has an inlet opening 46 and an outlet opening 47 in the block 44. One

end of the inlet passage 46 opens into the frusto conical portion 56 of the chamber 45. The other end of the inlet passage 46 extends to one of the large rectangular faces of block 44. The outlet opening 47 extends from the frusto-conical portion 56 of the block opening 45 to the face of the block 44 opposite the face having the inlet opening 46.

The shut-off element 48 fits into the chamber 45 as shown in Figure 3. When instal-led, the frusto-conical portion 52 of the shut-off 48 fits into the frusto-conical portion 56 of the cavity 45, and the cylindrical portion 51 of the shut-off 48 fits into the cylindrical portion 55 of the chamber 45. The 0-ring seal 53 fits tightly between the shut-off 48 and the walls of the chamber 45 to provide a fluid seal to prevent fluid from leaking out through the portion of chamber 45 beyond the flow passage and the shut-off element 48. The seal 53 is positioned on the shut-off element 48 so that when the shut-off 48 is in its innermost posi-tion the seal 53 is outward of the outlet passage 47, so it is not in the fluid passage between the inlet opening 46 and the outlet opening 47. This seal 53 seals the control mechanism 50 from the fluid flow passage.

A probe 49 extends coaxially from the inlet opening 46. The probe 49 can either be a tubular piece of acceptable medical grade material or a spike, both of which are known in the art. A tubular piece of medical grade material would be used in conjunction with a duckbill valve attached to the mounting structure 32. A spike may be used when a disk of self-sealing rubber-like material is substituted for the duckbill valve. The end of the probe 49 contacting the inlet 46 may be flared outward slightly to wedge the probe 49 in the opening of the valve mounting structure 32 and seal the flow path through the flow controller 5.

A flow restrictor (not shown) may be fitted within the inlet opening 46. Such a flow restrictor produces an opening that varies in size in response to the pressure of the fluid in the bladder 29. The flow restrictor may constrict the opening to produce a smaller opening and reduce the amount of fluid flow at higher pressures. As the fluid pressure in the bladder 29 drops, the opening of the flow restrictor gets larger. The pressure responsive flow restrictor evens out the flow rate of the fluid coming from the bladder 29. Thus, the flow rate of the fluid stays substantially constant until the bladder 29 is essentially empty. A flow restrictor having a fixed orifice may also be used to obtain similar results in some situations. Fluid flows through the flow controller 5 by flowing through the probe 49, into the inlet passage 46, through the frusto-conical portion 56 of the chamber 45 past the frusto-conical portion of the shut-off element 48, and then through the outlet passage .47. ^' The 0-ring seal 53 on the cylindrical portion 51 of the shut-off element 48 prevents the fluid from flowing past the shut-off element 48 to the position control mechanism 50 and through the open end of the chamber 45.

The axial position of the shut-off element 48 within the block chamber 45 is adjustable to control the amount of fluid that flows from the inlet passage 46 to the outlet passage 47. When the shut-off 48 is at its extreme innermost position, the frusto-conical portion 52 of the shut-off seats snugly against the frusto-conical portion 56 of the chamber 45, and no fluid can flow around the frusto-conical portion of the shut-off from the inlet passage 46 to the outlet passage 47. As the shut-off 48 is moved axially outward, a small gap develops between the frusto-conical portion of the shut-off and the walls of the chamber 45, allowing a small amount of fluid to flow past the shut-off from the inlet passage 46 to the outlet

passage 47. As the shut-off 48 is moved farther out, the gap between the shut-off and the opening walls widens , allowing a greater amount of fluid to flow through the cavity portion between the inlet and outlet passages of the flow controller 5. Changing the axial position of the shut-off 48 in the chamber 45 varies the cross-sectional area of the flow path. The flow rate of fluid through the flow controller 5 varies as the cross-sectional area of the flow path varies. The position of the shut-off element 48 in the chamber 45 is controlled by the control knob 50, which threadably engages the cylindrical portion 51 of the shut-off element 48 by means of threads 57 on a central aperture in knob 50. The thumb control 50 is fitted within a slot 58 in the block 44. The slot 58 is open on the top, but is preferably closed on the bottom. The control knob 50 is knurled on the outside perimeter so a person can. easily turn it with his finger -or thumb. When the control knob or disk 50 is rotated, the threads 57 on the disk 50 engage the threads 54 on the shut-off 48 to move the shut-off 48 into or out of the chamber 45 to vary the fluid flow rate through the flow controller 5. When the desired flow rate is achieved, the threads 57 on the control disk 50 and threads 54 shut-off 48 help maintain the position of the cylindrical portion of the shut-off 48. The threads 54, 57 are sealed from the fluid flow path by the seal 53 around the perimeter of the shut-off element 48, axially between the frusto- conical portion 52 and the threads 54.

In some applications it may be desirable to provide a fixed, predetermined flow rate. In such situations, a stationary shut-off 48 eliminates error on the part of the user or medical personnel. The flow rate is predetermined for the particular medication and the position of the shut-off 48 is fixed in the cavity 45 to provide that

fluid flow rate, and the user-adjustable control knob 50 becomes unnecessary.

Referring to Figure 3, two openings are located on the rectangular surface of the block 44 having the inlet opening 46. These openings fit with the alignment pins 22 on the top 10 of the cassette housing 6. The two preferably cylindrical openings have inside diameters slightly larger than the outside diameters of the aligning pins 22, and the distance between the centers of the openings is the same as the distance between the centers of the aligning pins 22.

In assembly of the flow controller 5 and the bladder cassette 4, the aligning pins 22 are inserted into the openings in the block 44 while the probe 49 is inserted through the valve 35 in the mounting element 32. The probe 49 thus opens the valve 35. The probe 49 and two pins 22 should be parallel to ensure that the flow controller 5 will align with the cassette 4 during connection. After the flow controller 5 Is placed on the cassette 4, the probe 49 extends past the duck bill valve 35 and into bladder 29.

The outlet passage 47 of the flow controller is connected to micro bore tubing, such as is known in the art, which serves as the line 2 to the patient (Figure 1). The pressure of the fluid in the bladder 29 forces fluid through the flow controller 5, the outlet 47 and the dispensing conduit, such as the line 2 and the needle 3.

Advantageously, the bladder 29 is filled while in the cassette 4. The flow controller 5 is not needed to fill the bladder 29. This allows multiple bladder cassettes 4 to be filled at a remote location and used interchangeably with one flow controller 5.

The bladder 29 is filled after the bladder assembly 8 is positioned within the main housing 6 and the cover 7 is locked into place with the lip 16 and the locking tooth 15. The bladder 29 is filled with an instrument such as a

syringe or commercially available filling machine such as are presently in use in hospital pharmacies, capable of producing a large pressure in the bladder 29. A probe such as the flow controller probe 49 is mounted on the syringe. The probe is passed through the duckbill valve 35 or self-sealing rubber-like disk and the medical fluid is inserted into the bladder 29. When the bladder 29 is full, the instrument is removed and the duckbill valve or self-sealing rubber-like disk closes, preventing the outward flow of the fluid. With a full bladder 29, the cassette 4 can be attached to the flow controller 5 with the aligning pins 22 and the spike or probe 49 for use.

The flow controller 5 and the cassette 4 are two separate parts that form an interchangeable system. Thus, only a limited number of flow controllers 5 needs to be kept on hand, which can be used with any bladder cassette 4 of a particular size. With the bladder cassette 4 and the flow controller 5 interchangeable, a user's stocking requirements are simplified. The cover 7 of the housing 6 preferably includes a window 59 (see Figures 1 and 2) to allow observation of the bladder 29 as it empties. The interior surface of the back 9 of the cassette housing 6, opposite the window 49, may be marked with graduations to indicate the quantity of fluid remaining in the bladder 29. In the preferred embodiment, the various graduations are colored to further aid personnel in observing the bladder status as it empties .

Referring now to Figures 7 and 8, an alternative apparatus for controlling the flow rate through the flow controller is shown. The shut-off element 48 and control knob 50 of the embodiment described with reference to Figures 2 and 3 for regulating the flow between the inlet passage 46 and the outlet passage 47 are replaced by a shut-off element 60 providing rack and pinion control to align one of a plurality of separate, distinct flow

openings 61 for connecting the inlet and outlet passages 46, 47 of this flow controller 62 to change the cross- sectional flow are of the fluid passage through the controller. For this embodiment, the inlet passage 46 and outlet passage 47 of the flow controller 62 are axially aligned on opposite sides of a perpendicular elongate opening or cavity 63 in the block 64 housing the flow controller 62. An elongate rack 60 having a toothed segment 65 and an opening segment 66 is contained within the elongate cavity 63.

The opening segment of the elongate rack 60 has a plurality of openings 61 through it of distinct sizes. Each of these openings 61 may be moved into alignment between the inlet passage 46 and the outlet passage 47 of the flow controller block by longitudinally, moving the elongate rack 60 within the block opening.

The movement of the rack 60 is accomplished by the interaction of the teeth 65 of the toothed segment of the rack 60 and the pivoting pinion 66 and knob 67. The knob 67 projects outside the block 64 of the flow controller 62 so the user has access to it to turn it. The knob 67 rotates in one location in block 64, while the rack 60 moves within the opening 63. Adjustment of the rate of fluid flow from the flow controller's inlet passage 46 to the outlet passage 47 is provided by turning the knob 67. When the knob 67 is turned, the teeth of the pinion 66 engage the teeth 65 of the rack 60 to move the rack 60 longitudinally until the proper opening 61 is aligned between the inlet and outlet passages 46, 47.

The openings 61 in the rack 60 are spaced so only one opening aligns with the flow path at any given time. Flow is shut off when the rack 60 is positioned so the inlet and outlet passages are between openings 61 in the rack 60 by a set of seals, one around the inlet opening and another around the outlet opening. These seals also

ensure that when one opening 61 is selected fluid does not seep around the shut-off element 60 to flow through others of the openings 61 , thus yielding a different flow rate than desired. Further, the control mechanism consisting of the toothed portion 65 of the rack 60 and the pinion 66 are completely outside the fluid flow passage.

Numbers (Figure 8) may be spaced along the side of che rack 60 opposite the teeth 65 of the toothed portion. The edge of the block 64 may have a view window 68 through which one number is visible at each position of the rack 60 to indicate which opening 61 is aligned in the fluid flow path. The numbers may correspond to flow volumetric rates associated with each opening 61 in the rack 60.

Referring to Figure 10, an apparatus for conveniently aligning and holding the bladder cassette 4 is shown schematically. A holster 69 permanently houses the flow controller 5. The holster 69 has a sliding cradle member 70 having a first, open position, and a second, closed position. the open position of the cradle 70 is shown with phantom lines in Figure 10. The sliding cradle 70 includes an L-shaped element 71 , having an upturned end 72. A bladder cassette 4 fits snugly in the sliding member 70. The cassette 4 can be mounted in the cradle 70 when the holder 69 is in the open position, extended out from the holster body 73. The cassette 4 engages the flow controller 5 when the cradle 70 is moved to the closed position within the holster body 73. The sliding element 70 holds the cassette 4 in correct alignment as it slides into position. The cassette is aligned by virtue of its position in the L-shaped element 71 sliding holder 70. When the bladder in the cassette 4 is empty, the cradle 70 may be slid to the open position, and the cassette 4 removed and replaced.

Figure 6 discloses an apparatus for holding a plurality of bladder cassettes 4 and flow controllers 5. The apparatus includes a- holster 74 with a plurality of

flow controllers 5 integrally attached to the holster 74. The cassettes 4 are removable, and slide into and out of compartments 75 in the holster 74. A door 76 on the bottom of the holster 74, which may be hinged or sliding, encloses the compartments 75 and holds the cassettes 4 in place during use, while allowing access to change the bladder cassettes 4 when necessary.

The flow controllers have probes (not shown) such as spikes, or tubes of appropriate medical grade material attached to the inlet openings (not shown). The outlets (not shown) empty into a mixing chamber 77. The fluids mix and the pressure of the multiple bladders forces the mixture from the holster outlet 78 where the fluid can be injected into a patient. Some alternative embodiments of this invention are illustrated by Figures 11-17.

Referring first to Figure 11 , there is shown an exploded view of an alternative, preferred dispenser of this invention comprising the main housing ^' 6 for containing an auxiliary housing 79 to which in turn is mounted bladder assembly 8 so that housing 79 and bladder assembly 8 can together slidably fit into the main housing 6 through an open end 80 in housing 6. The bladder dispenser is then completed by capping the resultant assembly with flow controller 5. Particularly, auxiliary housing 79 comprises on its upper surface 80 a slot tf1 extending from a free edge 82 of surface 80. Slot 81 is for receiving the attachment means 83 at the outlet of bladder assembly 8. The lower end of auxiliary housing 81 , which first enters the main housing 6, has a slot 28 for receiving the attachment means 33 for the closed end of bladder 29. Slot 28 extends upwardly from the free end of structural member 23 in a direction substantially parallel to the longitudinal axis of bladder 29. Adjacent slot 28 are two prongs 84 and 85 which engage by snap-fit recesses 86 and 87 on the interior floor of main housing

6. Also to insure that auxiliary housing 79 aligns properly with main housing 6 and is held therein, housing 79 has lugs 88 which engage slots 89 in the rim 90 of open end 80 of housing 6. Auxiliary housing 79 also has structural member 23 extending between slots 28 and 81 to form the convex prestressing surface 24 over which bladder 29 is to be stretched. The means of attachment of the bladder assembly 8 to curved surface 24 is as follows. Firstly, the closed end attachment means 33 is hooked behind slot 28 which engages a neck portion 41 in the bladder. Since attachment means 33 is wider than slot 28 it cannot pass therethrough and the bottom end 31 of the bladder is therefore retained there. Bladder 29 is then stretched across curved, prestressing surface 24 and the upper outlet end 30 with its attachment means 83 is slid into slot 81 on the upper surface 80 of housing 79. Attachment means 83 has a peripheral groove 91 sized to fit groove 81 in housing 79 and since the upper surface 92 of attachment means 83 is larger than groove 81 it will not pass therethrough. The distance between grooves 81 and 28 in housing 79 are such that bladder 29 is stretched over surface 24.

Bladder assembly 8 shown in Figure 11 also includes an indicator 93 hingeably attached to attachment means 83. When bladder 29 is filled, it bears against indicator 93 which pivots about its hinge to a position which indicates that the bladder is full. As the bladder is emptied, indicator 93 swings back following the collapsing bladder and the arcuate movement of indicator 93 can be seen through window 49 in main housing 6. Window 49 is marked with graduations 94 which indicate the approximate volume of liquid in bladder 29. When bladder assembly 8 on auxiliary housing 79 are together in place in main housing 6, the resulting assembly is capped with flow controller 5. A probe 49 extending below flow controller housing 44

ruptures a seal 95 on the outlet to bladder 29. The contents of bladder 29 may then be delivered from outlet 95 from flow controller 5, the flow of fluid being regulated by control mechanism 50. Normally, outlet 95 from flow controller 5 is capped by a luer lock 96.

The details of the means for attaching the outlet end 30 of bladder 29 to stretch and pressurize the bladder, and its associated outlet and valve can better be seen in Figure 12. In that Figure, attachment means 83 comprises a generally rectangular member 97 whose upper surface 92 is provided with inlet and outlet apertures 98 and 99, respectively. Member 97 has a circumferential groove 91 around its side walls for engagement with the slot 81 in auxiliary housing 79 shown in Figure 11. Attachment means 83 has a generally cylindrical portion 100 extending below outlet 98 and terminating in an externally ribbed portion

101. The outlet end of bladder 29 slides over the ribbed

• portion 101 and is held there by a C-clamp 102 around bladder 29 and over ribbed ^■ portion 101. C-clamp 102 has teeth 103 on each arm which progressively engage as the clamp is tightened around bladder 29. Consequently the outlet end of bladder 29 is firmly clamped to attachment means 83.

Outlet 98 and attachment means 83 includes an internal outlet passage (not shown) which is fitted a one-way valve 104 which is preferably a duckbill valve. Valve 104 is kept in outlet 98 by means of a cap 105 and the outlet 98 is then sealed by means of a foil sheet 106 over outlet 98. Sheet 106 is perforated by probe 49 when flow controller 5 is attached. Inlet 99 in attachment means 83 has an internal channel (not shown) which is in fluid communication with bladder 29 through extension 100. Seated in outlet 99 is an additional one-way valve 107 which is also preferably a duckbill valve. This outlet is retained in outlet 99 by means of locking cap 108 which in turn is mounted with a luer lock cover 109. Bladder 29

can be filled by means of a syringe through filling cap 108 or for automatic filling by means of a probe through that cap. Then, luer lock 109 is screwed onto filling port 108. Attachment of luer lock 109 to filling port 108 is such that it is free to rotate thereon so as to render the assembly tamper-proof.

In this and other embodiments shown herein, bladder assembly 8 is disposable either alone or in combination with the ^' housing to which it can be attached. Thus, main housing 6 in Figure 2 can also be disposable. However, since the housing shown in that figure is relatively complex it is preferred that the two-component housing arrangement of the type shown in Figure 11 is used so that bladder assembly 8 can be disposed along with auxiliary housing 79. This then reduces the cost of the disposable item and is more convenient since the bladder assembly can be disposed of without detachment from the prestressing, curved surface.

One disposable ^• combination of this type is shown in Figure 13 which more clearly shows the assembly of closed end attachment means 33 through slot 28 over element 23. Figure 13 also more clearly shows indicator 93 connected to attachment means 83 by means of a pivot 110 at a point approximately one quarter of the length of indicator 93 from the upper end 111 of indicator 93. A hollow tube 112 is mounted on means 83, in alignment with indicator 93 and between its upper end 111 and pivot point 110. Inside tube 112 is a coil spring 113 which bears against indicator 93 and normally biases indicator 93 about its fulcrum point towards bladder 29. As previously explained, as the bladder 29 empties, indicator 93 follows' the collapsing bladder to indicate the approximate volume of its contents.

Referring to Figure 14, there is shown details of the flow controller housing 44 in this embodiment which comprises a raised portion 114 and a lower portion 115.

Portion 115 has a circular hole 116 through it. Hole 116 accepts by snapfit a generally cylindrical member 117. Member 117 has around its lower periphery a grooved flange 118 for snap-fit engagement with hole 116 in housing 44. Member 117 carries control knob 50 which has an internal, generally cylindrical chamber 119 sized to fit over the vertical walls 120 of element 117. Around the upper walls of member 117 is an annular projection 121 which includes a ratchet which can be selectively engaged by a lug 122 on the inner wall of chamber 119 in control cap 50. The selective engagement is achieved by raising cap 50 over element 117 until lug 122 engages the ratchet. Under these circumstances cap 50 is locked on the teeth of the ratchet so that the flow control can no longer be readily adjusted. When adjustment of the flow is required, cap 50 is pushed downwardly over element 117 to disengage lug 122 from the ratchet. Cap 50 may then be rotated freely to adjust a flow control member, which will be described in more detail below, which is engaged by a cavity 123 inside cap 50. Cap 50 has an external rib 124 which will engage a projection 125 on the raised portion 114 of housing 44. This is to prevent cap 50 from turning more than one complete revolution so as to limit the extent of flow variation from the dispenser of the invention to prevent excessive flow levels.

Preferably, cap 50, member 117 and the flow controller attached to cap 50 is a unit which is disposable from housing 44.

Cavity 123 in cap 50 engages a correspondingly shaped portion 125, shown in Figure 15, at one end of a shut-off element 48 located in flow housing 126. Housing 126 comprises an inlet passage 46 through probe 49 which is used to perforate the outlet seal 106 (Figure 12) in bladder assembly 8 as shown in Figure 12. Inlet passage 46 is in fluid communication with outlet passage 47. The axis of outlet passage 47 is arranged at approximately 90°

to the axis of inlet passage 46. Inlet passage 46 comprises a frusto-conical portion 56 before continuing past outlet passage 47 into a generally cylindrical chamber 55. Shut-off element 48 comprises a frusto- conical end 52 at the other end from control cap end 126. The center portion of shut-off element 48 includes a cylindrical portion 51 having a size and shape corresponding to that of chamber 55. The forward end of cylindrical portion 51 carries behind frusto-conical portion 52 an 0-ring seal 53 which bears against seating 127 at the end of chamber 55 adjacent the junction of inlet passage 46 and outlet passage 47 so that all fluid flows along these passages rather than into chamber 55. A portion of the internal wall of chamber 55 is threaded, as at 54, to engage corresponding threads 57 on the external surface of shut-off element 48. The assembly is contained in member 117 by means of spaced annular ribs 128 and 129 which form an annular groove 130 between them for snap-fit into a circular hole 131 in the base of element 117 (Figure 14).

The operation of the flow controller in this embodiment is similar to that described in relation to the flow controller of Figure 3. Thus, as control cap 50 is turned the walls of cavity 123 in cap 50 bear against shut-off element 48 to turn it through its threaded portion and thereby move the frusto-conical shut-off portion 52 in the correspondingly shaped portion 56 of inlet passage 46. It will be appreciated that as shut-off element 48 moves along the axis of this passageway the available flow path around the periphery of shut-off element 48 will be varied in cross-section as the element moves in that passage thereby regulating the flow of liquid from dispenser 1.

Some further preferred embodiments of the invention are shown in Figures 16 and 17. In Figure 16 there is shown an alternative construction for the main housing 6

of the dispenser 1 of this invention. In a manner similar to that shown in Figure 11 , dispenser 1 is separable into a main housing 6 and an auxiliary housing 79 for carrying bladder assembly 8. In the embodiment shown in Figure 16, main housing 6 has a generally cylindrical shape, open at one end 80 to receive housing 79 and bladder assembly 8 in combination. In Figure 17, auxiliary housing 79 fits into an opening 80 in the side of the main housing 6. In this embodiment, auxiliary housing 79 comprises opposite vertical side walls 131 and 132, respectively, joined by a base wall 133 and an upper surface 80. Surface 80 has a cut out slot 81 for receiving the upper attachment means 83 (not shown) of bladder assembly 8. Attached to the inside of wall 132 is structural element 23 having a curved surface 24 over which bladder 29 (not shown) is to be stretched. Member 23 is attached at its first, upper end 25 to the inside of wall 132 and is braced near its lower end by attachment to wall 132 through support member 27. The lower, second end 26 of member 23 is spaced from the floor 133 of housing 79 so that the other lower attachment means 33 (not shown) of bladder 29 may be hooked into and behind that space. Wall 131 of auxiliary housing 79 is the leading wall which enters the main housing 6. Wall 131 has a channel 134 across its width for snap fit engagement with a corresponding rib (not shown) on the interior, corresponding wall 135 of main housing 6. The lower, central portion of wall 135 is cut to form a tongue 136 bearing the engagement rib so that tongue 136 may be lifted by the finger to disengage the rib and channel 134 and thereby remove auxiliary housing 79 from the main housing 6. The upper surface 137 of main housing 6 has a slot 138 in its leading edge 139 so that auxiliary housing 79 may be removed from or inserted into the main housing 6 with the flow controller 5 attached to the bladder assembly 8 (not shown). Flow controller 5 in Figure 17 is similar to that described in previous

embodiments and comprises a probe 49 for fluid communication with the contents of the bladder and an outlet 95 capped by a luer lock 96. A shut-off element 48, as previously described, is located in an internal chamber (not shown) in the flow controller 5 and is attached to, and turned by, annular disk 50 which rotates around a fixed collar 138 which carries graduations 139 along which pointer 140 on disk 50 moves to indicate the flow rate selected.