US3325062A - Fluid injection apparatus - Google Patents

Description

June 13, 1967 R. 1. HARRIS, SR.. ETAL- 3,325,062

FLUID INJECTION APPARATUS Filed April ll, 1966 m mDQm Affitti! f .fill 12711111 NO United States Patent O 3,325,062 FLUED INJECTION APPARATUS Rano J. Harris, Sr., and Rano J. Harris, Jr., both of Baton Rouge, La., assgnors to Precision Sampling Corporation, Baton Rouge, La., a corporation of Louisiana Filed Apr. 11, 1966, Ser. No. 541,723 8 Claims. (Ci. Z22-386.5)

This invention relates to the art of dispensing fluids in quantitative volumes, at high efficiency, accuracy and precision. In particular, it relates to precision bore apparatus for dispensing fiuids. More particularly, it relates to a precision bore needle syringe containing new and novel seal features integral with the forward end of the bore of an enclosing cylinder, and with a piston movable therein.

The dispensing of small accurately measured volumes of fluids, especially gases, into systems operated at high temperatures and pressures, or both, presents acute difficulties. Gas syringes, e.g., are generally constructed by providing a tubular member or barrel at an end of which is mounted a hollow or tubular needle. The openings through the barrel and needle provide a continuous bore or passageway lying through the axis of the device, and into which is provided a snugly fitting movable piston or plunger. A major problem relates to the difficulty of confining or containing a gas within the desired volume inside the barrel forward of the face of the piston, especially when the piston is forced forward to compress and expel the gas through the needle at relatively high pressure.

When the measured quantity of fluid, eg. gas, is to be injected the pressure will force gas around the face of the piston and into the annular space between the inside wall of the barrel and the external surface of the plunger. Obviously, this dificulty increases with the increasing pressure of the system into which the gas is to be injected.

Moreover, aside from this problem there is lan even more acute difficulty associated with delivering all of a measured quantity of the lffuid, e.g. gas, forward of the face of the piston. Present devices are constructed of readily deformable materails and the forward end of the barrel of present devices provides a dead volume so that gas located therein cannot be ejected by positive action of the piston. This produces error, and the error increases with greater pressure. For example, a given or normal error due to the dead space, e.g. at atmospheric pressure, will be substantially trebled when the gas is to be injected into a system against a pressure of three atmospheres; or the error will be increased eight fold if the gas is injected against eight atmospheres -of pressure.

A further problem is that concerned with leakage of gas at the junction or location wherein the needle adjoins the barrel.

The objective of the present invention is to obviate these and other prior art difficulties. In particular, it is the object of this invention to provide a needle syringe with a barrel having precision bore, uniform from one end to the other, and within which is mounted a movable piston provided with an integral forward seal for fiushing with the forward end of the barrel. It is also an object to provide a fixed seal at the forward end of the barrel permitting precise and precision contact between the face of the piston seal and the fixed seal to eliminate any dead space at the forward end of the barrel. The invention relates especially to the overall combination of the seal-piston unit, the precision bore within which the seal-piston unit moves, and the fixed seal located at the forward end of the barrel. More particularly, it is an object to provide an easily movable cylinder-piston unit slidably disposed within the precision bore of the barrel of a needle syringe, to

Patented `fune 13, 1967 flush precisely with a fixed seal located at the forward terminal end of the barrel. A further object is to provide a fixed novel seal in which the needle is mounted to suppress shock and prevent leakage of fiuids, especially gases, around the annulus of the needle.

These objects and others are achieved in accordance with the present invention which contemplates the combination of a precision bore, tube or barrel within which is fitted a movable piston, provided with an integrally mounted seal the face of which is adapted to flush precisely with the face of a fixed seal located in the forward end of the barrel. Contact between these seals virtually eliminates any dead space Within the barrel and, as such, positively displaces and expels fluids from the barrel and through the needle.

A feature of the invention relates to the movable seal of the piston for preventing leakage of Huid around the face of the piston into the annular space between the external surface or diameter of the piston and the inside of the walls of the tubular member or barrel. An additional feature relates to the fixed packing or seal located at the forward end of the barrel within which the needle is mounted. Another feature of interest relates to the use of a slidable side vented needle by virtue of which a sample or specimen can be trapped within the precision bore.

A feature of the piston-seal assembly resides in the novel construction, nature of the materials, and the association between the piston and the seal. A portion of the piston upon which the seal is to be circumferentially mounted is grooved or undercut. An open centered resilient member is then drawn over the undercut portion, capping same and leaving a void or space between the internal enclosing wall of the resilient member and the exposed surface defined by the undercut. This void is gas filled to an extent sufficient to partially inflate the seal, or if confined by the enclosing wall of a chamber, sufcient to thrust the external wall of the resilient member outwardly and into close contact with the enclosing wall.

The invention will be better understood by reference to the following detailed description and to the accompanying drawings, to which specific reference is made in the description.

Referring to the drawings:

FIGURE 1 shows an elevation View, in partial section, of a precision lbore needle syringe, this including the combination of a precision bore through the barrel 4of a syringe, a piston located within said bore, the piston being provided with a forward seal integral therewith, and a fixed seal located at the forward end of the barrel this serving as a seating arrangement for attachment of the needle, and as a surface for precision contact with the seal of the piston,

FIGURE 2 is an enlarged fragmentary section view of the embodiment of FIGURE 1 showing a portion of the barrel and the forward portion of the piston, upon which is provided a novel seal feature, and

FIGURES 3 and 4 are fragmentary views, in section, of another embodiment wherein a movable needle with a side opening is provided for opening `and closing the inside of the precision bore to the exterior.

Referring specifically to FIGURE l, the device 10 depicted is a needle syringe for measuring and dispensing small quantities of iiuid, especially gases. The device 10' is composed generally of an enclosing wall, forming a tubular member or barrel 11. The barrel 11 is open through its center or along its central axis, `and on the forward end thereof is affixed a hollow or tubular needle 12. The forward or terminal end 121 of needle 12 is sharpened or pointed, hollow ground if desired, and the opposite end thereof is affixed within the forwardly tapered retainer nut 13. Within the opposite end of barrel v11 is fitted a reciprocable piston 20, at the forward end of which is provided a novel seal constituting a key and novel feature of the present invention.

In a preferred embodiment the needle 12 is also fitted into the retainer nut 13 and provided with a novel seal feature. The primary function of retainer nut 13 is to hold needle 12 and packing 15 (the needle-fixed seal feature) in the forward end of barrel 11. The retainer nut 13 is provided with an externally threaded shank 132 and is affixed upon the forward end of barrel 11 via engagement with an intern-ally threaded cylindrical shaped barrel extension number 14 secured to the forward end of barrel 11. Extension member 14 can be cemented upon the end of barrel 11, if desired. Thus, where barrel 11 is constituted of glass an epoxy resin can be used to cement a metal member 14 to barrel 11. The retainer nut 13 is provided with an internal opening 131 into which is fitted the tubular needle 12. The needle 12 is pressed tightly into a packing 15 located at the forward end of barrel 11, the

packing constituting a forward seal to prevent leakage of gas about the annulus between the needle 12 and opening 131 of retainer nut 13. Preferably, the needle 12 is not projected all the way through the packing 15 which can be cemented or otherwise aixed to the front of barrel 11 if desired. In position, the precision formed opening through needle 12 is contiguous to and precisely aligned with the axis of the opening through barrel 1-1.

A reciprocable piston is fitted into the opposite end of barrel 11. At the opposite extremity of barrel 11 is thus provided an open centered end plug or capping member 17 through which is fitted the movable piston 20. The rear terminal end of piston 20 is provided with a thumb button or handle 21, and at the opposite or forward end of piston 20 is provided a seal 30 to be more fully described by specic reference to FIGURE 2.

The forward portion of the capping member 17 is provided with an externally threaded shank 171, the member 17 being held in place at the end wall of barrel 11 via union between the shank 171 and the cylindrical shaped internally threaded member 18. The latter member, i.e. member 18, is rigidly secured upon the terminal end of barrel 11, as by cementing. The primary function of capping member 17 is to prevent high pressures from forcing piston 20 out of barrel 11. In other words, even if the piston 20 is forced t-o its extreme position toward the end of the barrel 11 it will not be blown out of barrel 11.

At the forward end of piston 20 is provided a generally cylindrical shaped open end member which forms the resilient seal 30. This seal 30 is movable with piston 20. The open end member 31 fits tightly over the terminal end of piston 20 and snugly within the confines of or inside the tubular walls of barrel .11. The seal 30, in combination with the piston, and in combination with the piston and tubular barrel, constitutes a novel feature of the invention.

It will be observed that the forward end of piston 20 is provided with undercuts, circumferential grooves or cutaway portions 22 and thereover is tightly fitted the open end cylindrical capping member 31. It will be observed that the cutaway portions 22 provide open spaces 32 lying between the shoulders or projections formed by the undercuts 22 in the forward end of piston 20'. An O- rinig 33 is also provided toward the rear of the cutaway portions 22. The presence of the O-ring 33 creates a partial vacuum at the time the seal is formed by pushing piston 20' into capping member 31 and helps in maintaining the seal in place. The O-ring 33 also aids in maintaining a space between cutaway portions 22 and the internal wall of resilient member 31, as well as to offer resistance against inward deformation and to apply a force upon the latter. The external surface of resilient member 31 is provided with a plurality, in this instance four, of vanes 311, 312, 313, 31.1, formed by circumferential grooves cut into the external surface of resilient member 31. The vanes 311, 312, 313, 314, particularly the latter three- viz 312, 313, 31.1-are generally lof equal or slightly larger cross-sectional diameter than the inside diameter of barrel 11, and also slightly larger than the cross-sectional diameter of the adjacent portions of the capping member itself, so that these members can be caused to press tightly against the inner walls of the barrel 11.

A feature of the seal-piston combinationis that the open spaces 32 inside the resilient member 31 contains gas, at superor `above-atmospheric pressures lto exert force outwardly to project the vanes 311, 312, 313, 31.1 against the inner walls of barrel 11. Preferably sufficient gas is provided within openings 32 to produce pressures ranging from about 30 to about 1000 pounds per square inch, and more preferably from about 30 to about 150 pounds per square inch. In accordance therewith gas is provided to, contained an-d trapped within the openings 32 of the resilient member 31 surrounding the cutaway portion 22. The wall of the resilient member 31 is thrust outwardly to press the circumferential vanes 311, 312, 313, 31.1 tightly and snugly against the inside wall of barrel 11 to provide la very effective leakproof seal.

In pressurizing the seal of the seal-piston combination, consideration is given to the amount of pressure against which a specimen is to be injected. This means that the gas pressure to be employed is to a lange extent pre-selected in accordance with the pressures against which a fluid specimen is `to be injected. The seal is pressurized to exert sufficient force against the inside wall of the cylinder to prevent leakage of the specimen about the annular space. This means that if a fluid is to be injected into a system, e.g. a gas chromatograph, supplying an instrument pressure of 150 pounds per square inch, the pressure exerted by the seal against the inside wall of the cylinder will not be less than 150 pounds per square inch and generally will be more to compensate for the slight positive pressure necessary to inject the specimen. If e.g. the instrument pressure is 1000 pounds per square inch, the seal pressure will be greater than 1000 pounds per square inch.

The gas used in pressurizing the seal should be one which is inert to the metal piston and to the material of which the seal -is composed, nitrogen and helium have been found excellent gases for such usage.

The resilient member 31 should preferably, be constructed of a material which provides a considerable amount of resiliency ab initio, i.e. even prior to the time that it is formed and placed over the cutaway portions 32 of plunger 20 and pressurized. Suitable resilient materials are e.g. natural and synthetic rubbers, caoutchouc, guttapercha, neoprene, Thiokol, Koroseal, Butyl rubber and the like; resins, plastics and plastic-like materials such as eg. nylon, polypropylene and the like. In certain instances metals can also be employed, e.g. alloys of iron and steel, and the like. Lubricantscan be added. Preferably, however, the material is one which possesses self` lubrlcating properties as well as resiliency. Certain hard resins, plastics, plastic-like materials, and compositions are known to possess such properties. Outstanding materials for such usage are e.g. polymerized halogenated ethylenes, especially polyuoroethylenes such as polytetrafluoroethylene and compositions thereof. A particularly outstanding material is that sold under the trademark Teflon (-Du Pont). This material has a very slippery surface, is highly resilient, especially `when pressurized with sufficient gas to provide pressures ranging at least about 30 pounds per square inch and more preferably from about to about 500 pounds per square inch. As such, e.g. the piston 20 `readily holds such gas pressures and is readily reciprocable within barrel 11, little effort being required to work the piston 20. The seal withstands the very high gas pressures without leakage around the seal. Another advantage residing in the use of e.g. Tefion involves its relative low cost, its high inertness and :relative lack of memory or retention of most gases, and the relative ease in forming such seals.

In the embodiments described by reference to FIG- URES l and 2, a Teflon seal `filled with helium gas to provide pressures ranging from about 500 pounds per square inch, utilized on the end of a stainless steel piston and Working within a stainless steel barrel is employed to measure various specimens of gas and inject same into a gas chromatograph operating at 150 F. against pressures of about 500 pounds per square inch. In accordance therewith leakage around the face of the plunger was successfully prevented. The specimen was substantially totally inject in to the instrument.

The outstanding feature of the combination is that dead space at the forward end of the device is entirely eliminated, and total injection from -barrel 11 occurs. In accordance with such embodiment the needle 12 is tightly fitted within the fixed seal or packing 1.5 located at the forward end of barrel 11. The face of movable seal 30, upon forward movement of piston 20, flushes precisely with the face of fixed seal 15 so that all fiuid within the precision bore `of barrel 11 is driven into the openings of needle 12 and injected into the system.

A specifically preferred type of syrin-ge is that combination shown by reference to FIGURES 3 and 4. Only the forward portion of a syringe is shown, it being contemplated that the balance of the structure shall be identical to the embodiment shown by reference to FIGURE 1.

The embodiment of FIGURES 3 and 4 is characterized by a side vented needle 02, a side vent portion 012 which is slidable into and out of the fixed packing 015. The retainer nut 013 can thus be screwed all the way into the extension member 014 so that the shoulders at the forward end of the opening 016 will be thrust against the boss 09 to cause movement of needle 02 and projection of the needle opening 012 outside of packing 015 and into the barrel 011. This opens the chamber within barrel 011 through the needle. Conversely, as shown by reference to FIGURE 4, when the retainer nut 013 is screwed partially out of extension member 014 the forward portion or extremity of the retainer nut 013 impinges upon boss 08 forcing it forward, moving needle 02 forward sufficiently to withdraw opening 012 into the packing to close the chamber of the barrel 011 to the needle 62.

In another embodiment, also, a wire can be extended from the forward end of plunger and in alignment with the opening or passageway through the needle 02, 12 to displace every trace of fiuid therefrom in an ejection stroke of piston 20.

In a typical operation, the dispensing end 121 of the precision ground needle 12 is placed into a supply of gas to be measured and injected. The piston 20 is retracted to the right or withdrawn to the desired extent to draw gas through the opening of needle 12 and inside the portion of barrel 11 forward of plunger seal 30. The distance of piston withdrawal can be conveniently determined by indicia marks (not shown) appropriately scribed upon the barrel, this being particularly effective and simple when the barrel 11 is constructed of a clear or transparent material, e.g. glass or plastic. To dispense the measured volume of liquid, e.g. into a gas chromatograph, the point 121 of needle 12 is thrust through a septum and the piston pushed forward, or to the left, to dispel the gas.

It `will be apparent that the present invention is susceptible to certain modifications and changes without departing 'the spirit and scope thereof.

Having described the invention what is claimed is:

1. In combination, apparat-us defined by an enclosing wall forming a tubular barrel with a precision bore, an enclosing wall at the forward end of the barrel, a fixed seal formed by a packing located ins-ide the forward wall, a hollow needle projecting through an opening within said fixed seal, a reciprocable piston fitted into the bore from the opposite end of the barrel, said piston being provided with undercuts in the surface thereof and an open centered resilient member which covers the undercuts of the piston to form a seal having an enclosed opening which can be filled with gas sufficient to cause the outer surfaces of the resilient member to be thrust outwardly to press tightly and snugly against the inside circumference of the wall of the tubular barrel to form an effective leak proof seal, movable with the piston, but which can be flushed precisely with the forward fixed seal to eliminate dead space within the barrel.

2. The apparatus of claim 1 wherein the outer surface of the resilient member is grooved to provide a plurality of vanes which can be projected against the inner wall surface of the tubular barrel.

3. The apparatus of claim 2 wherein the seal consists essentially of Teon.

4. The apparatus of clairn 3 wherein the enclosed opening within the resilient member is provided with sufficient gas to provide a pressure of from about 30 to about 1000 pounds per square inch upon the inside wall of the tubular barrel.

I5. The apparatus of claim 1 wherein the forward wall of the tubular barrel is formed -by a retainer nut threadably engaged to the barrel and through which a tubular needle is projected and anchored within the forward fixed packing which serves as a seal.

6. The apparatus of claim S wherein the fixed seal is Teon.

7. The apparatus of claim S wherein the needle is provided with a side opening and is movable into and out of the fixed packing to open and close off the needle to the bore.

8. The apparatus of claim 7 wherein the needle is provided with a pair of bosses, one located Within the retainer nut and one outside the retainer nut.

References Cited UNITED STATES PATENTS 3,157,323 11/ 1964 Kitterman 222-5210 3,223,282 12/1965 KlOe'hn 222-386 X 3,244,324 4/1966r Croslin 21212-444 X 3,253,592 5/1966 Von Pechrnann 222-386 X ROBERT B. REEVES, Primary Examiner. N. L. STACK, Assistant Examiner.

Claims (1)

1. IN COMBINATION, APPARATUS DEFINED BY AN ENCLOSING WALL FORMING A TUBULAR BARREL WITH A PRECISION BORE, AN ENCLOSING WALL AT THE FORWARD END OF THE BARREL, A FIXED SEAL FORMED BY A PACKING LOCATED INSIDE THE FORWARD WALL, A HOLLOW NEEDLE PROJECTING THROUGH AN OPENING WITHIN SAID FIXED SEAL, A RECIPROCABLE PISTON FITTED INTO THE BORE FROM THE OPPOSITE END OF THE BARREL, SAID PISTON BEING PROVIDED WITH UNDERCUTS IN THE SURFACE THEREOF AND AN OPEN CENTERED RESILIENT MEMBER WHICH COVERS THE UNDERCUTS OF

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