proceeding to a detailed description of the present invention , the flexible expansion means , generally 10 , is shown in fig1 in conjunction with a standard i . v . set , generally 11 , which will include two spaced apart injection sites 24 and 30 which are connected to the flexible expansion means , generally 10 , by means of lengths of tubing 26 and 29 . flexible expansion means 10 is composed of an outwardly pleated , flexible tubing having expandable wall sections 15 and a central passageway 17 having a width greater than the diameter of tubing 26 and 29 . the i . v . administration set 11 will include the usual i . v . solution container 12 which will be supported by the usual support means through bail 14 . a vented piercing pin , generally 16 , will have the usual drip chamber 19 and air vent 18 . a length of tubing 20 will interconnect drip chamber 19 with y - injection site 24 and the flow of liquid through tubing 20 is controlled by a flow control clamp 22 . at the opposite end of the set is a length of tubing 34 connected with y - injection site 30 and the flow of liquid therethrough controlled by slide clamp 36 . a needle adapter 39 provides attachment for hypodermic needle 40 . two hypodermic syringes 42 and 43 having hypodermic needles 46 and 45 , respectively , are placed in pierceable engagement with reseal caps 25 and 32 of y - injection sites 24 and 30 , respectively . fig2 illustrates the flexible expansion means 10 when it will be filled with a retrograde volume of fluid 44 supplied by syringe 43 . it will be noted that the fluid 44 fills the space between the pleated wall sections 15 . this will be explained later in the operation . fig3 illustrates an alternative embodiment , generally 50 , of a flexible expansion means wherein the flexible expansion means is in the form of a length of corrugated tubing having pleated side walls 53 . as is similar to flexible expansion means 10 , it is utilized in the same i . v . administration set as illustrated in fig1 with a length of tubing 55 interconnected to drip chamber 19 and solution container 12 as well as to first injection site 54 . tubing 59 is also interconnected with injection site 54 having a reseal cap 56 for engagement with hypodermic syringe 73 by means of needle 57 . a length of tubing 60 also connects corrugated tubing 50 with a second injection site 62 which communicates with hypodermic syringe 71 by means of needle 64 passing through reseal cap 63 . another length of tubing 66 extends from reseal site 62 with the flow therethrough controlled by slide clamp 68 . needle adapter 69 secures hypodermic needle 70 thereto . fig4 is an enlarged view showing the corrugated tubing 50 with side walls 53 in the expanded state and the retrograde fluid 44 contained therein . this will be later referred to in the operation immediately to follow . a better understanding of the advantages of the flexible expansion means 10 and 50 will be had by reference to their operation . the i . v . administration set 11 will be packaged in the usual manner as illustrated in fig1 except that the hypodermic syringes 42 and 43 will not be in contact with the injection sites 24 and 30 . neither is the hypodermic needle 40 nor i . v . solution container 12 usually attached . when it is desired to administer the fluid in container 12 , the hypodermic needle 40 will be attached to needle adapter 39 and the vented piercing pin and drip chamber 16 pierced through the usual rubber stopper in container 12 . fluid flow will be controlled through the set by means of flow control clamp 22 and by opening slide clamp 36 . when it is desired to administer the retrograde additive liquid in syringe 43 , such as vitamins , the slide clamp 36 will be placed in a closed position and hypodermic syringe 42 will be positioned in contact with y - injection site 24 with hypodermic needle 46 pierced through reseal cap 25 and plunger 48 in an inward position . when it is desired to introduce the additive material , syringe 43 will have hypodermic needle 45 pierced through cap 32 and the contents of the syringe delivered into the y - reseal injection site 30 by moving plunger 49 into the syringe barrel . as clamp 36 is in a closed position , the contents of the syringe will fill into tubing 34 and 29 whereupon it will expand into the expansion means 10 . as this is occurring , the liquid in the expansion means 10 will in many instances fill it completely until it appears in the condition shown in fig2 . the excess liquid will then flow into tubing 26 and syringe 42 with an automatic moving outwardly of plunger 48 . it will be recognized also that tubing clamp 22 will be in a position to close tubing 20 which will have previously been filled with liquid from container 12 . to deliver the retrograde volume of liquid 44 , all that is required is that the syringes be removed from the injection sites and slide clamp 36 be opened . the retrograde volume will flow out to hypodermic needle 40 until the expansion means will assume the previous condition as indicated in fig1 . the operation of the expansion member 50 shown in fig3 and 4 will be as previously described for unit 10 . pleated tubing 53 will be in a collapsed condition before the retrograde fluid is introduced which is illustrated in fig3 . with the retrograde fluid 44 introduced it will assume a position as shown in fig4 . accordingly , the only difference between utilizing the corrugated tubing 50 over the pleated chamber 10 is that it will be effected over a longer vertical dimension . the pleated or corrugated tubing representing the flexible expansion means 10 and 50 is composed of a resinous , plastic material such as polyvinyl chloride and can be formed in the usual manner into the pleated or corrugated condition . it is assembled in an i . v . set such as between two lengths of tubing 26 and 29 by solvent bonding as the same plastic material can be used for the tubing as well as for the expansion means 10 or 50 . alternatively , different thermoplastic materials can be used such as polyolefins and still be sealed or bonded together such as by means of epoxies . it will be appreciated that in place of a vented piercing pin 16 a nonvented one could be employed when a self collapsing container is employed such as a flexible container . further , when the flexible expansion means 10 or 50 is employed with a positive pressure system , such as an i . v . pump , it is important that the expandable wall sections 15 and 53 remain in one of two stable conditions , extended or collapsed . if they are allowed to collapse by their own resilience , they will influence the delivery rate and may bolus the patient . the preferred manner is to have them extended until the medication has been pushed toward the patient . they could then be collapsed by compressing them to their original shape . they would then be ready for use for the next retrograde medication procedure . it is apparent that some means of holding the expansion sections extended or collapsed against the pump pressures ( up to 40 psi ) must be employed if they are to be utilized in conjunction with an i . v . pump . this would be accomplished in using materials and fabrication methods to adjust the force required to expand or contract the pleated walls . the expansion or contracting sections should be of such rigidity that the sections , when filled with medication , will remain extended . controlled expansion is also required for if they expand unintentionally , the unit can draw blood into the catheter or needle . upper injection sites 24 and 54 are disclosed in conjunction with flexible expansion means 10 and 50 . while resulting in a less practical unit , these could be eliminated if the additive volume is less than the volume of the expanded section and the clamps above and below are closed when filling . overfilling will pressurize the capacity between the clamps : if the upper clamp is opened first , excess will go up to the drip chamber ; if the lower clamp is opened , the excess will be delivered to the patient ( bolus ). in utilizing the two syringe systems , one should be aware not to remove the same amount as added . it will thus be seen that through the present invention there is now provided a flexible expansion member for an i . v . administration set which will allow for varying the retrograde volume of an additive i . v . fluid . the flexible expansion member permits a large volume of liquid to be placed in an i . v . administration set between the respective injection sites obviating the need for a long length of flexible tubing . as will be readily appreciated , the i . v . solution container is usually set at a predetermined distance above the patient and the use of a long length of flexible tubing can be a problem because of potential kinking or constriction . it will be further seen that the flexible expansion means is simple in its construction and can be readily fabricated from standard thermoplastic materials and molding techniques . the foregoing invention can now be practiced by those skilled in the art . such skilled persons will know that the invention is not necessarily restricted to the particular embodiments presented herein . the scope of the invention is to be defined by the terms of the following claims as given meaning by the preceding description .
an i . v . administration set is provided with a flexible expansion section so as to accommodate an additional volume of liquid without the use of excessive lengths of tubing . the expansion section is in the form of pleated or corrugated tubing which , upon the introduction of liquid into an i . v . set such as by means of a hypodermic syringe , will accommodate an additional portion of liquid which is known in the i . v . administration art as a retrograde volume .