High-flow Capacity, Self-regulating Bypass Spike

Abstract

A bypass spike suitable for aseptic insertion through a one-holed stopper into a liquid reservoir for withdrawing liquid at a rapid rate therefrom. The bypass spike is particularly suitable for use in a series of liquid reservoirs from which liquids are to be withdrawn sequentially and in which the vent air of the first of the reservoirs is used as vent air for all the remaining reservoirs.

Description

This invention relates to apparatus for controlling the flow of a liquid from a series of reservoirs and more particularly to a bypass spike suitable for aseptic insertion through a single-hole stopper to achieve a high, automatically controlled flow of liquids while maintaining the liquids under sterile conditions. The apparatus of this invention is particularly useful in processing blood.

Long term storage of human blood requires that it be frozen in a liquid medium to protect it during storage. U.S. Pat. No. 3,145,913 describes and claims a preferred method and apparatus for handling blood which is to be stored. The blood is collected directly into a one-use sterile plastic liner placed in a certrifuge rotor, or in a disposable rotor without a liner, wherein the red cells are stored after replacement of the intracellular and intercellular water by glycerol. When the blood is to be used, it is brought up to temperature, the liner, if one is used, is placed in a centrifuge rotor and the glycerol is replaced by a suitable saline liquid while the red cells remain in the centrifuge.

In the so-called Meryman protocol for deglycerolization, the deglycerolization comprises treating the blood cells with prescribed quantities of saline liquids of decreasing concentrations. As an example, after predilution with a 12% NaCl solution, the cells are treated with a 1.6% NaCl solution and then immediately thereafter with an 0.8% NaCl solution. In this protocol, full quantities of each treating solutions are used in sequential order. It has been proposed that this treating step using several different solutions in sequence can be performed automatically without any intervention by a technician by venting the first stoppered upturned liquid reservoir, from which the first treating solution is delivered, into the fluid path of the second treating solution so that the vent air becomes available to the second stoppered upturned liquid reservoir only after the first liquid reservoir is empty. In a similar manner, if a third treating solution is used, the vent air from the second liquid reservoir is used in emptying the third liquid reservoir, and so on.

The liquid reservoirs of treating solution are typically rubber stoppered glass bottles, suspended from a suitable support such as is shown, for example, in U.S. Pat. No. 3,552,577; and the treating liquid is gravity fed into a tubing connected to the interior of the bottle by means of a so-called "bypass spike" which is forced through a sealing diaphragm in the stopper. The tubing in turn is connected to a controllable-rate liquid pump such as illustrated, for example, in U.S. Pat. No. 3,565,286 (FIGS. 10-13). In order to empty the liquid reservoirs in this manner while maintaining a completely sterile regime it is necessary to provide a flow of sterile air into the upturned bottles. It is, of course, possible to use a two-holed stopper having two separate spikes inserted through the two holes, one spike for air and one for liquid discharge. It is preferable, however, from safety and convenience points of view, to use the commercially available one-holed stopper and a single spike.

The presently available single-holed stoppers and spikes are made for the delivery of parenteral solutions at much lower flow rates than the 300-400ml/minute rate desirable for delivering a treating solution to a centrifuge rotor in blood declycerolization. The spikes presently used for delivering parenteral solutions are molded plastic and their solution and air passages are not adaptable for handling rapid flow rates. Moreover they rely upon a plastic tip for puncturing the stopper diaphragm.

It is therefore a primary object of this invention to provide an improved bypass spike to serve as the means of fluid communication between the interior of a liquid reservoir and a liquid delivery tubing. It is another object of this invention to provide a bypass spike of the character described which provides self-regulating control of liquid flow at high flow rates. Still another object is to provide a bypass spike particularly suitable for use in a red blood cell treating protocol. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The high-flow capacity, self-regulating bypass spike of this invention is characterized as having a thin-walled stainless steel tubing inserted in a plastic molded spike to serve as the vent passage. The stainless steel tubing terminates internally within the spike in a molded vent passage and socket which are located around the main liquid passage and it extends externally beyond the end of the molded plastic tip.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 illustrates the use of the bypass spike of this invention;

FIG. 2 is an exploded view of the bypass spike showing the alignment and assembly of the four components;

FIG. 3 is a longitudinal cross section of the bypass spike of this invention;

FIGS. 4 and 5 are two side elevational views of the molded tip end of the spike;

FIG. 6 is a end-on view of the tip end of the spike pin with the stainles steel air vent in place;

FIG. 7 is an end-on view of the connecting end of the spike pin;

FIG. 8 is a cross section of the gas vent socket taken at right angles to the cross section of this element as shown in FIG. 3;

FIG. 9 is a cross section of the gas vent socket taken through plane 9--9 of FIG. 3; and

FIG. 10 is a cross section of a one-hole rubber stopper showing the insertion of the tip of the bypass spike about to puncture the sealing diaphragm of the stopper.

The use of the high-capacity, rapid-flow bypass spike of this invention is illustrated in FIG. 1. Liquids which are to be delivered sequentially are contained within liquid reservoirs 10, 11 and 12 which are held by any suitable means (not shown) to have their delivery ends facing downwardly so that the liquid may be gravity fed through liquid delivery conduit 13 to a desired delivery point, e.g., a centrifuge rotor. A suitable pump (not shown) may be associated with delivery conduit 13. Each bottle is closed with a one-holed rubber stopper 14, seen in enlarged cross section in FIG. 10. It will be seen in FIG. 10 that the stopper has a sealing diaphragm 15 and a uniquely configured hole 16 so that when the tip end of the bypass spike punctures the sealing diaphragm the openings into the spike tip are sealed off until the spike has completely penetrated through hole 16 and enters the interior of the bottle. The rubber stopper design and its function is described to illustrate the use of the bypass spike and it is not part of this invention.

Returning to FIG. 1, it will be seen that a bypass spike 20 of this invention is used for bottle 10, spike 21 for bottle 11 and spike 22 for bottle 12. The bypass spike 20 for bottle 10 is connected through tubing 23 with a source of sterile air (not shown) and through spike connector tubing 24 to bypass spike 21 for bottle 11; and bypass spike 21 of bottle 11 is connected through spike connector tubing 25 with bypass spike 22 of bottle 12. The flow of fluid from bottle 10 to the centrifuge rotor (not shown), or other point of delivery, is through bypass spike 20, conduit 24, bypass spike 21, conduit 25, bypass spike 22 and delivery tubing 13. When bottle 10 becomes empty as shown in FIG. 1 the air from the bottle serves as vent air for bottle 11, and so on. By using bottles containing the precise amount of each liquid required and by placing them in the correct sequence in which their contents are to be used, it is possible with the arrangement illustrated in FIG. 1 for the technician to make only one hookup, start the apparatus and then leave it unattended. The desired sequential delivery of the liquids is thereafter automatic, and remains fail-safe so long as no in-between air leak occurs.

FIG. 2 is an exploded view of the high flow rate, self-regulating bypass spike of this invention, e.g., spike 20 of FIG. 1. The bypass spike is seen to be formed of four elements: a thin-walled air vent tubing 30, a spike pin member 31, a socket member 32 with fluid flow control passages, and a spike body member 33. The spike pin, socket member and spike body are preferably formed by molding a suitable synthetic resin material such as a polystyrene, polycarbonate or the like.

Air vent tubing 30 must be made of a material suitable for forming a thin-walled (typically 0.009 inch thick) rigid tubing with an outside diameter of the order of 0.075 inch. It is preferably formed of stainless steel.

The spike pin member 31 is shown in side elevational view in FIG. 2, in cross section in FIG. 3, in the detailed drawings of the tip end in FIGS. 4-6 and in the end-on view of the connecting end in FIG. 7. Reference should be had to all of these drawings wherein like components are referred to by like reference numerals. The tip end 35 of spike pin 31 provides three equally spaced openings 36, 37 and 38 defined between three equally spaced connecting members 39, 40 and 41 which join an air vent retaining ring 42 to the main body 43 of the spike pin (FIGS. 4-6). The tip end preferably has smooth radii around the three ports 36, 37 and 38, a configuration which essentially eliminates cutting out any little pieces of rubber from the stopper when the bypass spike is inserted through the stopper.

Opposite the tip end 35, the spike pin member has a connecting end 45 adapted for joining to the socket member 32 and body member 33. This connecting end comprises an outer annular ring 46 joined to spike pin body 43 through shoulder 47. (FIGS. 3 and 7). Within the volume 48 defined by outer annular ring 46 is a fitting ring 49 molded integral with shoulder 47 and spike tip body 43.

The internal wall 50 of ring 49 makes a smooth joining with the internal wall 51 of spike tip body 43. The channel 52 defined between wall 51 and the air vent tubing 30 terminates at the tip end at ports 36, 37 and 38 and opens into a liquid channel in socket member 32 as described below. The external wall 55 of fitting ring 49 is adapted for joining either by plastic welding or adhesive bonding techniques to the internal wall 56 of a socket-defining ring 57 of the socket member 32; and the internal wall 58 of outer annular ring 46 is similarly adapted for joining to the external wall 59 of main wall 60 of spike body member 33. In the particular embodiment of the bypass spike illustrated in FIG. 3, these interfitting walls are so dimensioned that they also make tight fits between the wall ends and their respective engaging surfaces so that fluid tight seals are formed. Thus the end surface 61 of ring 49 contacts the internal wall 62 of socket member 32, the end surface 63 of outer annular ring 46 contacts the surface 64 of seating flange 65 which is integral with wall 60; and the end surfaces 66 and 67 of socket ring 57 and body wall 60 contact the internal surface 68 of shoulder 47. This arrangement has been found convenient for assembling the bypass spike.

The socket member 32 is shown in detail in FIGS. 2, 3, 8 and 9 and reference should be had to these figures in the following description wherein like reference numerals are used to identify like elements. It is the purpose of the socket member and its associated passage defining elements to provide for the seating and alignment of the thin-walled air vent tubing, to provide fluid communication between the air vent tubing and an external connection and to provide fluid communication for the liquid flowing through the tip end into a fluid discharge at the end of the spike. To this end the socket member 32 is formed to comprise a main socket body 75 and a discharge tubing 76 which extends to within a short distance of the discharge end of spike body 33. The socket body 75 is formed as a short cylindrical socket section 77 joined with socket ring 57 which is a part thereof; and socket section 77 is joined with socket discharge tubing 76 through shoulder 78. Socket section 77 has oppositely disposed cutouts 79 into which opposite ends of a fluid passage 80, perpendicularly aligned with gas vent tubing 30, open to annular passage 81 defined between the external wall of socket tubing 76 and the internal wall of body member 33. Fluid passage 80 is defined within a socket insert member 82 which is best seen in FIGS. 8 and 9. This insert member is essentially rectangular, extending across the diameter of the socket body 75 and providing a counter-sunk bore 83 in which gas vent tube 30 is seated. Fluid passage 84 in insert member 82 connects the air passage in vent tube 30 with annular passage 81 which in turn is connected to the passage defined within body side arm 85 through opening 86. In FIG. 3, connecting arm 85 is 90.degree. out of position for convenience of illustrating it in cross section. In actual construction, opening 86 faces the wall of main socket body 75, not cutout 79 as shown.

Since liquid entering through the spike tip must be discharged through the discharge connector 90 of spike body 33, fluid channel means must be provided within the socket member to attain this desired liquid flow. As will be seen from the cross sectional drawings of FIGS. 3, 8 and 9, this is accomplished by reason of the essentially flat configuration of socket insert member 82 which defines oppositely disposed passages 91 and 92 on either side of the insert member. These passages are open to passage 52 and to the passage 93 defined within socket discharge tubing 76. This passage network leading from spike tip end ports 36-38 to spike body discharge connector 90 is of sufficient height and cross sectional area throughout to permit the rapid liquid flow rates required.

The relevance of liquid flow path height and the cross sectional area of the liquid flow path, particularly the diameter of passage 93, may best be understood from a brief analysis of the forces which produce fluid flow in the system incorporating the bypass spike. The maximum flow of liquid through the bypass spike from the liquid reservoir, e.g., bottle 10, to which it is attached is determined by the height of the liquid surface in the bottle above the exit of fluid passage 93. Any attempt to increase the liquid flow rate beyond this maximum value by either creating a vacuum at the outlet of discharge connector 90 or by supplying air pressure through connecting arm 85 results in a condition of mixed flow of air and liquid down through connector 90. Therefore, in a system such as this, it is not possible to increase the liquid flow rate through passage 93 beyond the maximum rate set by the hydrostatic head of liquid above the outlet of passage 93 and by the resistance to fluid flow that is inherent in the total liquid flow path extending from ports 36, 37 and 38 in the tip end to the outlet of passage 93.

Although the one remaining solution, i.e., increasing the length of discharge tubing 76 (and hence passage 93) and likewise the length of spike body member 33, would appear to be a simple one, formation of the components by practical injection molding techniques places restrictions on the length of such components. Thus, it has been found that a liquid flow passage length, from ports 36-38 to the discharge end of tubing 76, of approximately three inches provides the necessary hydrostatic head to give a liquid flow rate of up to about 400 ml per minute. This hydrostatic head and flow rate are maintained right up until the instant the liquid reservoir runs dry.

The diameter of passage 93 is limited by the density and surface tension characteristics of the liquid being handled and it should not be greater than that which will permit the tubing 93 continuously to remain filled with liquid during liquid flow. If the diameter of passage 93 is larger than the critical size for the liquid used, bubbles of vent air will enter into it and it will have only a partial cross section of liquid in it. The presence of such vent air in passage 93 effects a partial loss in the hydrostatic head necessary to maintain the high flow rates desired. In using the bypass spike of this invention to deliver saline solutions at a flow rate between about 300 and 400 ml per minute, it has been found that the inside diameter of delivery passage 93 should not be greater than about 0.2 inch using a hydrostatic head of about 3 inches. This combination of dimensions gives a maximum flow rate for saline solutions.

The operation of the bypass spike of this invention may be described with reference to FIGS. 1, 3, 8 and 10. The tip end of the spike which terminates with the extending exposed end of the rigid thin-walled gas vent tubing 30 is inserted with pressure through the sealing diaphragm 15 of the one-holed rubber stopper 14 (FIG. 10) which seals a liquid reservoir, e.g., bottle 10. In like manner, bypass spikes are inserted into the rubber stoppers of the bottles containing the remaining liquids to be supplied in sequence.

Typically, the bottles of saline solutions used in blood cell processing are under vacuum as received and in order to maintain aseptic conditions throughout their discharge, it is necessary to provide sterile vent air and to insure that it remains sterile throughout the protocol. When the stopper is first penetrated, there is an in-rush of air, and if this air is derived directly from the surrounding atmosphere it may carry contaminants. The tip end of the bypass spike is so designed that when the exposed end of the air vent tubing 30 just beings to penetrate sealing diaphragm 15 of the stopper (see FIG. 10) the rubber diaphragm stretches over ports 36-38 effectively sealing them off until the tip end beyond these ports is sealed. This in turn forces the vent air to enter through the vent air passage of the bypass spike and makes it possible to provide sterile air into the bottle. This can be done by providing already sterilized air or by placing a suitable filter in the air inlet line 23 (FIG. 1).

In the arrangement illustrated in FIG. 1 the sterile venting air enters through arm 85 and passes through passage 81, 80 and 84 into air vent tube 30 which is open to the interior of the bottle. Liquid from the bottle is discharged through the liquid passage network, comprising openings 36-38 and passages 52, 91 and 92 and 93, to be discharged through spike discharge 90. So long as liquid is being discharged from bottle 10 (FIG. 1) the liquid from this bottle flows through bypass spikes 21 and 22 entering through the side arm 85 of the spikes and passing directly out through discharge passage 90 by way of annular passage 81 which must, of course, have a cross section sufficiently large to permit the liquid flow rates desired. During this condition of flow no liquid leaves bottles 11 and 12 because no vent air is available to them.

Once bottle 10 is emptied, it is used to supply sterile vent air to bottle 11. At this point, vent air enters side arm 85 of bypass spike 21 and is delivered to the interior of bottle 11 as described above. Liquid from bottle 11 then follows the liquid passage network of passages 52, 91, 92 and 93 for delivery to delivery tubing 13 through passage 81 of bypass spike 22. Thus any number of liquid reservoirs may be connected in series for the sequential discharge of liquids without the need for periodic attendance.

The first bottle of a series, i.e., bottle 10 of FIG. 1 may, if desired, not use one of the bypass spikes of this invention if other means are provided to introduce sterile vent air and to discharge liquid. Thus, for example a two-holed rubber stopper with an air vent line in one hole and a liquid discharge line may be used. However, the ability to use the same bypass spike in all of the series of liquid reservoirs to be discharged sequentially eliminates any confusion or mix-up.

Commercially available aseptic bottle closures generally accommodate spikes of about 0.25 inch outside diameter. Using practical injection molding techniques, the largest internal diameter of a single-hole spike will have a cross sectional area no greater than about 65% of the cross sectional area represented by the outside diameter of the spike. Use of a thin-walled stainless steel gas vent tube in the center of the internal molded passage reduces the net cross sectional area available for liquid flow to about 53 percent. With this net cross sectional area and the required hydrostatic head as previously defined, the desired flow rates may be attained. However, if the liquid and gas passages were both molded, the cross sectional area for liquid flow would be reduced to far below that required to obtain the desired flow rates. Thus the combination of a molded liquid flow passage and a thin-walled metal gas vent passage makes it possible to provide a bypass spike suitable for use with commercially available aseptic bottle closures and at the same time capable of achieving relatively high liquid flow rates.

The use of the thin-walled rigid air vent tubing projecting beyond the molded tip end and the fluid tip openings possesses the added advantage of providing means to release air bubbles sufficiently high within the liquid reservoir to prevent entrainment of the bubbles in the discharging liquid and likewise to prevent the impairment of liquid flow control which bubble entrainment would cause. Moreover, the projecting thin-walled rigid air vent tubing serves as a very effective tip for easy penetration through the stopper diaphragm.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limited sense.

Claims

I claim:

1. A molded plastic bypass spike for effecting liquid flow from a reservoir, adapted for insertion by its tip end through a one-holed aseptic reservoir closure and to be sealed therein and having a spike pin member including a gas vent passage defining means and a liquid discharge passage, the improvement comprising a spike body member having a side arm and a discharge connector, a socket member within said spike body member in which said gas vent passage defining means terminates and a free passage through said socket member connecting said side arm with said gas vent passage defining means and with said discharge connector, said bypass spike being further characterized in that said gas vent passage defining means is formed as a thin-walled rigid metal tube centrally positioned within said spike and extending beyond the molded plastic tip end, whereby the cross section of said liquid discharge passage is of a dimension to permit a full, rapid, continuous liquid flow therethrough.

2. A bypass spike in accordance with claim 1 further characterized in that said liquid discharge passage is of a height to provide a hydrostatic head which in combination with said cross section of said liquid discharge passage is adapted to provide a liquid flow rate of at least 300 ml per minute.

3. A bypass spike in accordance with claim 2 wherein said liquid discharge passage is about three inches in length.

4. A bypass spike in accordance with claim 1 wherein said molded plastic tip end has an outside diameter no greater than about 0.25 inch.

5. A bypass spike in accordance with claim 1 wherein said rigid metal tube is stainless steel.

6. A bypass spike in accordance with claim 1 wherein said molded tip end has an outside diameter no greater than about 0.25 inch, and said rigid metal tube is a stainless steel tube with an outside diameter of about 0.075 inch and wall thickness of about 0.009 inch, whereby over 50 percent of the cross sectional area of the passage defined within said tip end is available for liquid flow.

7. A bypass spike in accordance with claim 1 further characterized in that said molded plastic tip end has three uniformly spaced ports serving as the inlet of said liquid discharge passage and that said tip end has smooth radii around said ports, whereby, when said tip end is inserted through the sealing diaphragm of said reservoir closure, any tendency to abrade particles from said closure is minimized.

8. A bypass spike in accordance with claim 1 further characterized in that said molded plastic tip end has uniformly spaced ports serving as the inlet of said liquid discharge passage and that said tip end has smooth radii around said ports, whereby when said tip end is inserted through the sealing disphragm of said reservoir closure, an air-tight seal is formed against said diaphragm as it is distended and before it is penetrated.

9. A high-flow capacity, self-regulating bypass spike for effecting liquid flow from a reservoir and adapted for insertion through a one-holed aseptic reservoir closure, comprising, in combination

a. a molded plastic tubular spike pin member having a tapered tip end and a connecting end, said tapered tip end having uniformly-spaced liquid ports and terminating in a gas vent tube retaining ring;

b. a thin-walled, rigid gas vent tube extending through said gas vent tube retaining ring of said spike pin member and projecting beyond both said tip end and said connecting end of said spike pin member;

c. a cylindrical socket member adapted at one end to be joined to said connecting end of said spike pin member and terminating at the other end in an extended discharge tube, said socket member having therein an essentially rectangular insert member adapted to provide a seat for that end of said gas vent tube which projects beyond said connecting end of said spike pin member and having passage means providing fluid communication between the passage within said gas vent tube and the outside of said socket member, said socket member also defining at least one passage in said insert member for providing fluid communication between the interior of said tubular spike pin member and said extended discharge tubing thereby forming within said spike a connected liquid discharge passage; and

d. a spike body member sealed at one end to said connecting end of said spike pin member and axially aligned with and surrounding said socket member and its extended discharge tube, thereby defining an annular passage around said socket member and said discharge tube, said spike body member having a side arm and a discharge connector aligned with said discharge tubing.

10. A bypass spike in accordance with claim 9 wherein said liquid discharge passage is of a height to provide a hydrostatic head which in combination with said cross section of said liquid discharge passage is adapted to provide a liquid flow rate of at least 300 ml per minute.

11. A bypass spike in accordance with claim 10 wherein said liquid discharge passage is about 3 inches in length.

12. A bypass spike in accordance with claim 9 wherein said spike pin member has an outside diameter no greater than about 0.25 inch.

13. A bypass spike in accordance with claim 9 wherein said rigid gas vent tube is stainless steel.

14. A bypass spike in accordance with claim 9 wherein said spike pin member has an outside diameter no greater than about 0.25 inch and said rigid gas vent tube is a stainless steel tube with an outside diameter of about 0.075 inch and wall thickness of about 0.009 inch, whereby over 50 percent of the cross sectional area of the passage defined within said spike pin member is available for liquid flow.

15. A bypass spike in accordance with claim 9 wherein said spike pin member has smooth radii around said ports, whereby, when said spike pin member is inserted through the sealing diaphragm of said reservoir closure, any tendency to abrade particles from said closure is minimized.

16. A bypass spike in accordance with claim 9 wherein said spike pin member has three ports and has smooth radii around said ports, whereby, when said spike pin member is inserted through the sealing diaphragm of said reservoir closure an airtight seal is formed against said diaphragm as it is distended and before it is penetrated.