|Publication number||US3021841 A|
|Publication date||Feb 20, 1962|
|Filing date||Mar 14, 1957|
|Priority date||Mar 14, 1957|
|Publication number||US 3021841 A, US 3021841A, US-A-3021841, US3021841 A, US3021841A|
|Inventors||Burke George K|
|Original Assignee||Baxter Laboratories Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (36), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Feb. 20, 1962 G. K. BURKE 3,021,841
INTRAVENOUS ADMINISTRATION EQUIPMENT Filed March 14, 1957 FIG. I
63 INVENTOR GEORGE K. BURKE ATTORNEY United States Patent Ofiice 3,921,841 Patented Feb. 20, 1962 3,021,841 INTRAVENOUS ADMlNISTRATION EQUIPMENT George K. Burke, Bethichem, Pa., assignor, by mesne assignments, to Baxter Laboratories, Inc., Morton Grove, IiL, a corporation of Delaware Filed Mar. 14, 1957, Ser. No. 646,088 in Claims. (Cl. 128--214} This invention relates to venoclysis equipment, and more particularly to an improved device, for use in intravenous administration, for the injection of fluid alternatively under conditions of gravity flow or forced injection.
In the administration of injection fluids, such as plasma or plasma substitutes, the fluid is caused to flow into the vein at a comparatively slow but steady rate. However, in cases of emergency it may be necessary to force copious quantities of the fiuid into the vein in a short period of time. Accordingly, it is advantageous to provide a single intravenous administration apparatus which is adapted to effect a gravity flow of the injection fluid, under normal conditions, while being further adapted to effect the forced injection of predetermined quantities of the fluid when necessary or desirable. One form of apparatus which may be advantageously'utilized for this purpose is described and claimed in my co-pending application Serial No. 394,681, filed November 27, 1953, now Patent 2,967,325 issued October 6, 1959, for Venoclysis Equipment. The present invention relates to specific structural improvements in the apparatus of the co-pending application, to the end that the apparatus may be utilized with greater efliciency and with improved effectiveness.
In general, the intravenous administration equipment of the type concerned herein includes a hypodermic cannula, adapted for insertion in the vein of a patient, and
communicating at one end with a length of flexible tubing. Connected in series relation with the cannula and tubing are a manually operable displacement pump, a drip through the drip observation chamber, pump, tubing and cannula into the vein. The rate of fluid flow may be controlled by means of an adjustable clamping device applied to the tubing, above the hypodermic cannula, and, advantageously, the rate of flow may be observed from the drip observation chamber, which is arranged so that the injection fluid enters the chamber in discrete droplets of as certainable volume, the flow of droplets being observable through a transparent outer housing of the drip observation chamber.
Under emergency conditions, it may be necessary to force blood into the vein at a rate greater than that possible through normal gravity flow, and, for this purpose the displacement pump may be actuated manually, advantageously by squeezing with the hand, to rapidly force predetermined quantities of injection fluid into the vein.
Ideally, the actuation of the displacement pump has no effect on the operation of the administration equipment under gravity flow. However, with presently known apparatus, operation of the displacement pump tends to cause a backfiow of the injection fluid into the drip observation chamber, located above the pump, so that the chamber becomes filled with fluid. When this occurs, it is no longer possible to observe the drip rate, i.e., the rate at which the discrete droplets of fluid enter the charm her from the supply container. This presents considerable problems in actual practice, since observation of the drip rate is generally the only means by which the attendant can determine whether fluid is flowing through the system, and at what rate.
Accordingly, one of the specific improved features of the present invention resides in the provision of an improved intravenous administration equipment including, in series, a drip observation chamber and displacement pump, in which improved valve means are provided in the pump to avoid backflow of fluid into the drip chamber during operation of the pump, or at least to reduce backflow to such a substantial extent that the level of fluid in the drip chamber is not materially increased. More speciflcally, the invention provides an improved check valve assembly, including valve and valve seat elements of improved design, and improved means for supporting the valve element, whereby the valve is permitted to close more rapidly and more effectively, upon operation of the pump, than has been possible heretofore. I
Another specific advantageous feature of the invention resides in the provision of a displacement pump of novel and improved construction, which is less expensive to manufacture and more effective in operation than similar apparatus of heretfore-k nown design. In this respect, the intravenous administration equipment of the type contemplated herein is intended for but a single use, after which it is discarded, and so must be of relatively economical design. At the same time, the structure must be extremely sturdy, and substantially percent foolproof, since physicians will entirely avoid the use of equipment which even occasionally fails during use.
formed and whereby a sturdy and non-separable mechanical pump structure is created. Specifically, the improved structure comprises novel end fittings for the flexible pump chamber, including novel coupling elements which cooperate with the check valve assemblies to secure the ends of the pump chamber in the manner desired.
Another specific improved feature of the present invention resides in the provision of an improved intravenous administration apparatus, including a drip observation chamber and a manually operable displacement pump, connected in series, wherein the drip chamber and pump form a compact, unitary assembly, providing for economical manufacture, packaging, storing, and shipping, and greatly facilitating the handling of the apparatus in use.
For a better understanding of the invention, and for a description of additional advantageous features thereof, reference should be made to the following detailed specification and accompanying drawing, in which:
FIG. 1 is a front elevation, with parts broken away, of an intravenous administration apparatus incorporating the features of the invention;
FIG. 2 is an enlarged elevational view, partly in section, illustrating features of construction of the improved displacement pump assembly incorporated in the apparatus of FIG. 1;
Below the drip observation chamber Ill is a pump assembly 14, which receives fluid from the chamber it) and delivers it, normally by gravity flow, into the upper end of a length of flexible tubing 15. The other end of the tubing 15., which will be referred to as the lower end,
is connected to a short'length of surgical tubing 16, by
means of a suitable fitting 17, and the surgical tubing 16 is, in turn, connected to a hypodermic cannula 18, which may be of a conventional type adapted for insertion into the vein of a patient.
In general, the apparatus is placed in operation by inserting the tubular extension 11 through the bottle stopper 12 and suspending the bottle 13 upside-down, whereby the fluid therein flows into the drip observation chamber by gravity. Conventionall an air cannula 19 is inserted through the stopper 12 and extends to a point near the bottom wall of the bottle 13 (top wall when the bottle is inverted) so that air may flow into the bottle as fluid is drained therefrom.
Fluid entering the drip observation chamber 1%, through the tubular extension 11, passes through a drip tube 20, from which the fluid, in the normal operation of the apparatus, falls in discrete droplets into the chamber 10. The drip observation chamber 10 is formed in part by a transparent outer housing 21, through which the fall of droplets from the drip tube 20 may be observed, and in this way a physician or other attendant may determine whether .the fluid is flowing properly from the bottle 13 and the approximate volumetric rate of flow.
Fluid within the drip observation chamber flows through a filtering screen 22, of very finemesh, and into the upper end of the pumpassembly 14, through an opening 23 in the upper end thereof. The pump 14 has a check valve assembly 24 at its upper end, to be described in greater detail, which is normally open and therefore normally permits fluid to flow through the inlet opening 23. The lower end of the pump 14 also has a check valve assembly 25, to be described in greater detail, which is also normally open and permits the fluid within the pump to flow through a pump outlet opening into the tube 15.
At some point along the length of the flexible tube 15 is a conventional valve member 27, having a tapered slot (not specifically shown) therein, which is adapted to be moved transversely of the principal axis of the tube to constrict the interior passage thereof in varying degrees. The arrangement is such that the valve member 27- may be employed to control the fiow of fluid through the flexible tubing 15, it being understood, in this respect, that the tubing sections 15, 16, and cannula 18 are disposed below the outlet of the pump 14 during normal operation of the apparatus, so that fluid tends to flow to the tubinglS by gravity.
Fluid passing through the flexible tubing 15, beyond the valve member 27, flows through the short length of surgical tubing 16 and into the hypodermic cannula 13 to be discharged into the vein of a patient. The surgical tubing 16 is provided primarily for the purpose of permitting hypodermic injections of additive substances into the stream of fluid flowing from the bottle 13, by projection of a needle through the side wall of the tubing 6 16. The tubing 16, being self-sealing, will not leak fluid following withdrawal of a needle therefrom.
In normal operation, fluid draining from the bottle 15 will fill the system to a point somewhat below the lower end of-the drip tube 20, as indicated, by way of example only, at line 28. Accordingly, the pump 14 is completely filled with fluid, as are the sections 15, 16 of the tubing,
while at the same time the level of'fluid is sufliciently below the lower end of the drip tube 20 to permit of the formation of individual droplets of fluid at the end of the drip tube, so that the input of fluid may be visually observed through the transparent drip housing 21.
As will be understood, the flow of injection fluid through the administration apparatus, under the action of gravity alone, is quite slow, this being a desirable feature under most conditions. However, under certain emergency conditions it is desirable to inject a substantial quantity of fluid into the patient in a relatively short time. Accordingly, the pump 14, which is filled with fluid, may be actuated to force a certain quantity of the fluid at a rapid rate through the tubing 15, 16 and cannula 13. To this end, the pump includes a flexible outer casing 29 adapted to be deformed manually, as by squeezing with the hand, whereupon the upper check valve assembly 24 closes and fluid is forcibly displaced from the pump, through the lower outlet thereof. The lower check valve assembly 25 prevents any return flow of fluid into the interior of the pump when the casing 29 is subsequently allowed to expand, or when the fluid pressure in the lower portion of the system for some other reason exceeds that in the pump casing.
One of the important considerations of the operation of the new intravenous administration apparatus is the prevention of the backflow oi fluid through the upper check valve assembly 24 during operation of the pump 1d. Thus, past experience has shown that there is a tendency for substantial quantities of fluid to escape through the upper check valve when the pump 14 is initially brought into operation. Such backflow of fluid may raise the fluid level 28 in the drip observation chamber 19 up to the lower end of the drip tubefifl, or so near thereto as to prevent the formation of individual droplets, so that it is impossible to determine either the rate of flow of the fluid or whether or not it is flowing at all. This, of course, is intolerable and steps must be taken to lower the fluid level, as by removing the cannula 18 to temporarily increase the rate of flow of fluid.
Another important consideration, in respect of intravenous administration apparatus of the type herein described, is the provision of an economical, compact, and wholly dependable mechanical assembly which may be quickly brought into operation and efliciently utilized for the purpose intended. The new apparatus incorporates many specific features, to be presently described, which jointly provide substantial improvements in the structure and operation of the new apparatus.
Referring now to FIG. 2, the upper check valve assembly 24 comprises a multi-purpose fitting 3b, which is advantageously molded from plastic material, such as clear polystyrene. The upper valve fitting St? has a base flange portion 31 forming, in ettect, the upper wall of the fitting, in which there are provided upwardly opening concentric recesses 32, 33, as wellas a central opening 23, forming an inlet into the pump. The inner one of the concentric grooves is adapted to receive the lower end of the filter screen 22, the screen being of generally cylindrical form, closed at its upper end. The outer groove 32 receives the lower end of the drip observation housing 21, which is also advantageously formed of clear polystyrene material, the housing 21 being of generally cylindrical cross-section and having a reduced upper portion from which project the tubular extension 11 and drip tube 20, as integral parts of the housing. In the assembled apparatus, the observation housing 21 and filter screen 22 are cemented or otherwise secured in the respective concentric grooves 32, 33, whereby to be rigidly connected to the valve fitting 3t In accordance with the invention, the upper valve fitting 3b is provided interiorly with an axial recess 34, into which projects an annular flange 35, defining the .inlet opening 23 and having a frusto-conical lower surface 36 forming a valve seat. As shown in FIG. 2, the
axial flange 35 projects below the upper end of the annular recess 34, as defined by the base flange 31, a substantial distance, which may be in the order'of oneeighth inch, in a fitting having an overall diameterin the order of 1 inches. Accordingly, the flange 35, together with the depending outer cylindrical wall 37 of the valve fitting 3t), defines an annular pocket 38, which forms an important part of the invention. The pocket 38, as will be described in connection with the operation of the valve assembly 26, serves to trap air which would otherwise interfere with the proper operation of the valve.
At the lower end of the wall 37 of the upper valve fitting is mounted a valve guide member 39, formed of plastic material, such as clear polystyrene, which comprises a vertically disposed cylindrical guide sleeve 40, suspended in coaxial relation to the valve fitting 30 by means of integral diametrically disposed supports 41 (FIG. 3). At the ends of the supports 41 are integral arcuate flanges 42, received against the lower end of the valve fitting wall 37 and cemented rigidly thereto. In accordance with one aspect of the invention, the guide supports 41 are of narrow transverse dimension and are provided with pointed upper surfaces, as indicated in FIGS. 1 and 2. The arrangement is such that fluid may flow downward, through the valve assembly, Without the occurrence of substantial bubble formations on the guide supports.
Loosely received in the cylindrical guide sleeve 40 is the stem 43 of a valve plunger 44. Advantageously,
the head portion 45 of the valve plunger is of hemispherical shape, giving the plunger a mushroom-like appearance. The plunger 44 is advantageously formed of relatively soft surgical rubber material, having a specific gravity somewhat less than the injection fluid to be administered with the apparatus. The arrangement is such that, when the pump chamber is filled with fluid, the valve plunger 44 will tend to float in the fluid and be urged toward its closed position, against the frusto-conical valve seat 36. The head of the fluid is great enough, however, to hold the plunger open sufliciently to permit a proper gravity flow of fluid, as will be understood.
The lower valve assembly 25, in the illustrated form of the invention, includes a valve fitting 46, formed of material such as clear polystyrene, and having a bottom wall 47 and an upwardly extending cylindrical outer Wall 48. The walls 47, 48 form a cylindrical recess, into which projects an integral, generally cylindrical, valve guide 49. The guide 49, in effect, forms an extension of a tubular outlet 50, leading downward from the body of the fitting 46, and has a plurality of vertical slots 51 (FIG. 4) therein providing for the relatively free flow of fluid into the outlet 50.
As shown in FIG. 2, the valve guide 49 loosely receives the stem portion of a valve plunger 52, the plungor being substantially the same as the plunger 44 of the upper valve assembly. The upper end of the valve guide 49 forms an abutment surface, against which the head of the valve plunger 52' may rest. However, as will be understood, in the normal operation of the apparatus, under gravity flow conditions, the valve plunger 52 will tend to float in the surrounding fluid. Y
Received at the top of the lower valve fitting 46 is a cap 53, formed of material such as clear polystyrene and having radially and axially extending flanges adapted to snugly engage the end surface and inner surface of the cylindrical wall 48, and to be cemented thereto. The cap 53 has a central opening 54 therein, forming an outlet from the pump chamber, and has a frusto-conical valve seat 55 facing downward, directly above the valve plunger 52.
In the illustrated form of the invention, the valve cap 53 has an annular recess or pocket 56 surrounding the valve seat 55, which may be effective in trapping air bubbles formed about the valve seat. However, as will be come apparent subsequently, the lower valve assembly does not form a critical part of the injection apparatus, as
is not an important consideration; in fact, in some cases, the lower valve assembly may be omitted altogether.
Extending between the upper and lower valve assemblies is the normally cylindrical pump casing 29, which is relatively flexible, being formed of a suitable plastic material such as plasticized polyvinyl chloride. In accordance with the invention, the 'ends of the pump casing 29 are received over the cylindrical walls 37, 48 of the valve fittings 30, 46, the said walls having tapered outer surfaces and being of somewhat larger diameter, at least at the base, than the inside diameter of the casing. In order to secure the casing ends tightly to the fittings 30, 46, a pair of tube clamps 57, 58 of improved design are provided, which grip the casing 29 adjacent its ends, firmly retaining the casing in sealed relation to the fitting 3G, 46, and which lockingly engage portions of the valve fittings to form a rigid and durable mechanical structure.
The fittings 57, 58 are in the form of collars, having openings 59 therein of approximately the same diameter as the pump casing 29. The inner walls of the openings 59 advantageously have sharp gripping shoulders 60,.61 (lower FIG. 2) which, in the assembled apparatus, are embedded in the casing wall to lockingly grip the latter.
Each clamping collar has a generally cylindrical outer wall 62, of greater diameter than the pump casing 29, which has a plurality of integral locking fingers 63 spaced circumferentially thereabout. The locking fingers 63 have beveled end faces 64, and locking shoulders 65 are adapted to engage flanges 66 on the respective valve fittings 36, 46. As indicated in FIG. 2, the flanges 66 have beveled faces 67 adapted to engage the beveled faces 64 of the locking fingers, upon axial application of the locking collars to the valve fittings, whereby the locking fingers are forced outwardly over the flanges 66 and into locking engagement therewith.
In the assembly of the pump casing and valves, the locking collars 57, 58 are slipped over the casing 29, after which the ends of the casing are applied over the tapered outer walls of the valve fittings 30, 46. The end portions of the casing are flared outwardly somewhat by the tapered outer surfaces of the fitting walls 37, 48, so that a relatively tight connection is afforded. The locking collars 57, 58 are then applied to the respective valve fittings 36, 46, so that the fingers 63 are lockingly engaged with the flanges 66 thereof.
As will be observed in FIGS. 1 and 2, the diameter of the central openings 59 in the locking collars is such that, when the collars are applied to the valve fittings, the annular space between the fittings and the openings is less than the Wall thickness of the pump casing 29. Accordingly, the walls of the casing are deformed, and a cold flow of the plastic casing material takes place, so that the casing is, for all practical purposes, mechanically locked together with the fittings and collars.
In the operation of the new administration apparatus, fluid flows from the bottle 13, through the drip observation chamber 10, pump 14 and tubing 15, into the vein of a patient. The pump valves are normally open, although the valve plungers 44, 52 tend to float in the fluid and therefore tend to seat against their respective valve seating surfaces. Under normal conditions, the level of the fluid is such that the drip observation chamber 10 is partly filled, although not to such an extent that the fluid level is close to the drip tube, and the inflow of fluid may be observed in the form of discrete droplets falling from the drip tube 20.
If it becomes necessary to force fluid through the apparatus at an increased rate, the flexible pump casing 29 is compressed manually, as indicated in FIG. 2, to displace a portion of fluid therein. When the pump is actuated, the valve element 44 of the upper valve assembly 24 immediately seals tightly against the valve surface 36, preventing backflow of fluid into the drip observation chamber 10, and the fluid is forced out through the bottom valve assembly 25. The lower valve element 52 is, of course, forced downwardly by the force of the downwardly'fiowing fluid.
Advantageously, the size of the pump chamber 29 is such that when it is squeezed to a collapsed condition, by a hand of average size, approximately twenty-five cubic centimeters of injection fluid will be displaced therefrom. This may be accomplished by so dimensioning the casing 29 that the effective portion has a volume in the order of 32-35 cc.
After the pump casing has been manually collapsed, to effect a forced. injection of fiuid, it is released and permitted, by reason of its inherent resiliency, to return to its normal cylindrical condition. This causes the lower valve assembly 25 to close, and fluid again flows into the pump chamber through the upper valve assembly 24.
One of the most important aspects of the invention resides in the structure of the upper valve assembly 24, particularly in respect of the provision therein of the annular air pocket 38' surrounding and generally above the valve seat 36. In the normal operation of apparatus of the type herein concerned, minute bubbles of air tend to adhere to the valve seating surface 36' and surrounding surfaces. As a result, when the pump 14 is actuated, in-
stantaneous closing of the valve plunger 44 is prevented, and an excessive quantity of the injection fluid flows upwardly from the pump chamber, into the drip observa* 'tion chamber. As mentioned previously, this often causes an intolerable condition, in that the drip observation chamber becomes filled, by the back-flowing fiuid and further flow observation is rendered impossible. This condition is satisfactorily remedied in accordance with the present invention, by providing the annular air pocket 38 above the valve seating surface 36, which traps air' bubble formations formed in the valving area and thereby efiectively prevents the undesirable accumulation of bubbles on the valving surfaces.
Another important feature of the invention resides in the provision of an improved valve assembly, for intravenous administration equipment, in which the support or guide for the valve plunger is of a novel and improved design. Thus, in the upper valve assembly 24, the valve guide 39 comprises supports 41 of minimum cross-section and having pointed upper surfaces. The arrangement is such that air bubble formations on and about the supports 41 are avoided, and the consequent interference with proper valve operation is eliminated. The structure of the valve guide 39 is also advantageous in that it may be inexpensively manufactured and easily assembled into the complete valve assembly.
Another important aspect of the invention resides in the provision of an intravenous administration apparatus of the type described, which incorporates novel and improved structural features providing for easier aseembly and resulting in a compact, unitary and highly rugged assembly which is adapted for eflicient handling and use.
To this end, the new apparatus includes improved com 1 bination fittings, by means of which the series-related drip observation chamber and pump chamber are mechanically interconnected as a single unitary structure. In addition, the new apparatus incorporates improved means for securing the opposite ends of the flexible pump casing to the respective valve assemblies, whereby to aflord a rigid, sealed, mechanical connection. The arrangement is such that assembly of the apparatus may be carried out expeditiously, without special skills, and a highly satisfactory structure is afforded.
It should be understood, however, that the specific form of the new apparatus herein illustrated and described is intended to be representative only, as certain. changes maybe made therein without departing from the clear teachings of the invention. Reference should therefore be made to the following appended claims in determin ingtne full scope of the invention. Y
1. An intravenous administration apparatus of the type adapted. to provide a continuous channel for injection fiuid flowing from a source of supply to a hypodermic cannula comprising, in combination, a drip observation chamber, a pump below the chamber, channel forming means connecting said pump and chamber in series relation, said channel forming means including a check valve located below said chamber and above said pump, said check valve comprising a valve fitting having an upper wall and depending side walls forming a downwardly opening valve chamber, said upper wall having an openiug therein forming an inlet, a valve seat surrounding said inlet and exposed to said valve chamber, said fitting having an annular recess therein surrounding said valve seat and located above said seat forming an air pocket, and a valve element movably supported below said valve seat and adapted for movement into sealing relation with said valve seat and formed of a material of less density than the injection fluid.
2. The intravenous administration apparatus of claim 1, in which the inlet opening of said valve fitting is defined, at least in part, by an annular flange projecting downwardly from said upper wall, said air pocket being defined in part by said annular flange.
3. The intravenous administration apparatus of claim 1', in which said valve seat is an annular frusto-conical surface disposed at an angle of in the order of 45 with respect to the axis of said fitting, and said valve element has an active valving portion of spherical contour.
4. The intravenous administration apparatus of claim 1 in which the valve element is a valve plunger of rnushroom-like shape having an enlarged active valving portion and a slender elongated guide portion, and which includes a valve guide member, said guide member having a sleeve-like portion adapted to receive and guide the guide portion of said valve plunger, said guide member further having a pair of integral diametrically disposed supports secured to the depending side walls of said valve fitting and supporting said sleeve-like member in coaxial relation thereto, said supports having pointed upper surfaces to prevent the formation of air bubbles thcreabout.
5. The intravenous administration apparatus of claim 1, in which said valve fitting has means at its upper end for securing a portion of said drip observation chamber, said chamber being formed in part by said upper wall, and said valve fitting further having means at its lower end for securing a portion of said pump, said pump being formed in part by said upper wall.
6. In an intravenous administration apparatus of the type adapted to provide a continuous channel for injection fluid flowing from a source of supply to a hypodermic cannula and including a drip observation chamber, a pump below the chamber and connected in series relation therewith, and a check valve between the pump and chamber, the improvement characterized by said valve comprising a fitting formed of rigid plastic material, said drip observation chamber comprising a housing formed of plastic material and secured rigidly to said valve fitting, said chamber being formed in part by said fitting, and said pump comprising a tubular section of deformable plastic material, said section being rigidly secured at one end to said fitting, said pump being formed in part by said fitting.
7. The intravenous administration apparatus of claim 6, in which the depending walls of said fitting are tapered and of smaller outside diameter at the bottom, said section of deformable plastic material being generally cylindrical in form and having an inside diameter less than the large-diameter portion of the tapered walls of said fitting, said sectionbeing adapted to be secured in rigid and fluid-tight relation to said fitting upon axial application of said section over said tapered walls.
1 8. The intravenous administration apparatus of claim 7, which includes a locking collar adapted to be received over said tubular section and said tapered walls and to be lockingly engaged with said fitting, said collar having an opening therein of a diameter not substantially greater than the outside diameter of said tubular section, whereby upon axial application of said collar over the assembled section and tapered walls said tubular section is deformed and gripped by said collar.
9. The intravenous administration apparatus of claim 8, in which said locking collar has an internal shoulder adapted to contact said tubular section upon axial application of the collar over the assembled tubular section and tapered walls, said deformable plastic material being adapted to cold flow under continued pressure whereby portions of said material flow behind said shoulder to mechanically interlock said tubular section with said collar.
10. The intravenous administration apparatus of claim 6, in which said drip observation housing has a generally cylindrical base portion, said drip observation chamber includes a filtering screen having a generally cylindrical base portion of smaller diameter than the base portion of said housing, said fitting having concentric annular grooves in its upper wall adapted to receive the respective base portions of said housing and filter screen.
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|U.S. Classification||604/185, 604/213, 210/448, D24/118, 137/559, 604/252|