阅读说明：本技术 鸭嘴隔垫 (Duckbilled spacer ) 是由 C.A.卡里斯尔 M.M.马雷 D.L.琼斯 E.J.海尼 D.S.哈巴德 于 2018-12-17 设计创作，主要内容包括：一种包含鸭嘴阀组件的隔垫包括从隔垫的主体延伸到鸭嘴阀组件的多个弹性体肋。当插入注入端口腔中时,隔垫的主体与腔之间的过盈配合产生的力通过肋传递到鸭嘴阀组件。肋构造成当针穿过鸭嘴阀组件时在铰接点处可逆地塌陷,并且间隔开以帮助将针在鸭嘴阀组件中对中。肋通过降低处于较高入口压力的压缩力的集中来减少鸭嘴阀组件上的磨损,同时保持足够的压缩力以在较低入口压力下关闭鸭嘴阀组件。(A septum containing a duckbill valve assembly includes a plurality of elastomeric ribs extending from a body of the septum to the duckbill valve assembly. When inserted into the injection end mouth, the forces generated by the interference fit between the body of the septum and the cavity are transferred through the ribs to the duckbill valve assembly. The ribs are configured to reversibly collapse at the hinge point as the needle passes through the duckbill valve assembly and are spaced apart to help center the needle in the duckbill valve assembly. The ribs reduce wear on the duckbill valve assembly by reducing the concentration of compressive forces at higher inlet pressures, while maintaining sufficient compressive forces to close the duckbill valve assembly at lower inlet pressures.)

1. A spacer, comprising:

a body formed of a resilient elastomeric material, the body including a central axis;

a cavity in the body, the cavity comprising an inner wall;

a duckbill valve assembly in the chamber; and

a plurality of ribs extending from the duckbill valve assembly to the inner wall.

2. The septum of claim 1, wherein the duckbill valve assembly is recessed from the bottom end in the cavity.

3. The spacer of claim 1 wherein,

the main body includes:

a first portion having a top end, a bottom end, a side extending between the top end and the bottom end, and a flange extending from the side; and

a second portion having a top end, a bottom end, sides extending between the top and bottom ends, and a recess in the top end sized and shaped to receive the flange and the bottom end of the first portion.

4. The spacer of claim 3, wherein the cavity is located in a bottom end of the second portion.

5. The septum of claim 4, wherein the duckbill valve assembly is recessed within the cavity from a bottom end of the second portion.

6. The spacer of claim 3, wherein the first portion includes a central bore extending along a central axis.

7. The spacer of claim 6, wherein said central bore includes at least one constriction.

8. The septum of claim 6, wherein the duckbill valve assembly comprises a slit; and wherein the septum is configured to enable a needle to be inserted sequentially into the top end of the first portion, through the central aperture, the bottom end of the first portion, the recess, and the duckbill valve assembly, and out of the slit.

9. The spacer of claim 3, wherein the second portion is generally cylindrical and includes an upper portion having a first diameter and a lower portion having a second diameter, the first diameter being greater than the second diameter; and is

Wherein the second diameter is sized to fit at least partially within a gas chromatograph injection port.

10. The spacer of claim 1, wherein each of the plurality of ribs comprises a hinge point.

11. The septum of claim 1, wherein each of the plurality of ribs comprises a thinner portion attached to the duckbill valve assembly and a thicker portion attached to the inner wall.

12. The septum of claim 1, wherein the duckbill valve assembly comprises a pair of opposing sides and comprises a slit, and wherein at least one rib extends from each side of the duckbill valve assembly at a non-perpendicular angle relative to the slit.

13. The spacer of claim 12 wherein said angle is in the range of 5 degrees to 85 degrees.

14. The septum of claim 12, wherein at least two ribs extend from each side of the duckbill valve assembly, the ribs being spaced apart from each other.

15. A method of using a gas chromatography spacer comprising:

providing a spacer having a body formed of a resilient elastomeric material, the body having a top end, a bottom end, and at least one side extending between the top end and the bottom end,

a cavity in the bottom end, the cavity comprising an inner wall,

a duckbill valve assembly in the chamber, the duckbill valve assembly including a slit, an

A plurality of ribs extending from the duckbill valve assembly to the inner wall, wherein each rib of the plurality of ribs extends from the duckbill valve assembly at a non-perpendicular angle relative to the slit; and

inserting the bottom end into a GC injection port;

wherein the interference fit between the GC injection port and the body applies a compressive force to the sides that is transmitted through the ribs to the duckbill valve assembly.

16. The method of claim 15, further comprising inserting a needle into a top end of the septum and through the duckbill valve assembly, the needle protruding from the slit, wherein, during the inserting, each of the plurality of ribs bends around a hinge point in each rib.

17. The method of claim 15, wherein the angle is in a range of 5 degrees to 85 degrees.

18. A method of using a gas chromatography spacer comprising:

providing a spacer having a body formed of an elastomeric material, the body having a top end, a bottom end, and at least one side extending between the top end and the bottom end,

a cavity in the bottom end, the cavity comprising an inner wall,

a duckbill valve assembly in the chamber, and

a plurality of ribs extending from the duckbill valve assembly to the inner wall, wherein each rib of the plurality of ribs extending from the duckbill valve assembly includes a hinge point; and

inserting the bottom end into a GC injection port;

wherein the interference fit between the GC injection port and the body applies a compressive force to the sides that is transmitted through the ribs to the duckbill valve assembly.

19. The method of claim 18, further comprising inserting a needle into a top end of the septum and through the duckbill valve assembly, wherein during the inserting, each of the plurality of ribs bends around a hinge point in each rib.

20. The method of claim 18, wherein each of the plurality of ribs comprises a thinner portion attached to the duckbill valve assembly and a thicker portion attached to the inner wall.

Technical Field

The septum containing the duckbill valve assembly includes a plurality of elastomeric ribs extending from the body of the septum to the duckbill valve assembly. When inserted into the injection end mouth, the forces generated by the interference fit between the body of the septum and the cavity are transferred through the ribs to the duckbill valve assembly. The ribs are configured to reversibly collapse at the hinge point as the needle passes through the duckbill valve assembly and are spaced apart to help center the needle in the duckbill valve assembly. The ribs reduce wear on the duckbill valve assembly by reducing the concentration of compressive forces at higher inlet pressures, while maintaining sufficient compressive forces to close the duckbill valve assembly at lower inlet pressures.

Background

Gas chromatography ("GC") is a widely used analytical technique with high sensitivity. Typically, a liquid sample is injected through an elastomeric seal (a "septum" typically made of silicone rubber or other elastomer) into a hot injection port where the sample is vaporized in an inert gas stream and the components are separated as the gas stream is swept through a chromatography column. The components eluted from the column are detected with a high sensitivity detector. The inertness and reproducibility of the injectate is critical to maintaining a high level of detection accuracy.

The primary purpose of the spacer is to seal against carrier gas leakage so that the sample is properly eluted through the column. Ideally, the septum must act as an effective hermetic seal for up to several hundred injections, each requiring a needle to penetrate the thickness of the septum. The spacers may be exposed to temperatures ranging from ambient temperatures to approximately 300 c and may be exposed to pressures up to 100 psi. The temperature and pressure experienced by the portion of the septum inserted into the injection port may be referred to as the inlet temperature and inlet pressure, respectively.

GC spacers used in the current laboratory to a large extent meet the requirements of reliable sealing and essentially follow a single basic design: a solid disc or plug of elastomeric material through which the needle is pierced to inject the sample. While this basic design does work effectively as a seal, one problem that has not heretofore been addressed is the inadvertent introduction of contaminating particles into the GC inlet. Repeated needle penetration through the septum wears the septum and roughens the needle, causing particulate septum material and metal fines to be brushed from the needle into the inlet. The spacer material adds volatile contaminants on the chromatographic baseline that appear as peaks interfering with the desired peaks from the sample components, and both the spacer material and the metal fines may act as adsorbents or catalysts, removing or degrading the components in the inlet before they can be detected.

At least one mechanical seal is available on the market that significantly reduces the generation of particles by replacing a solid elastomeric disc with a molded duckbill valve assembly (U.S. patent nos. 4,954,149 and 5,531,810). For each injection, the duckbill valve assembly will open because a blunt or "bullet" needle extends through the assembly. After removal of the needle, the assembly is closed by a combination of: (1) the relaxation of the rubber duckbill valve assembly that deforms due to the presence of the needle, (2) the air pressure that is exerted on the microvalve assembly inside the GC inlet, and (3) the metal spring (in U.S. patent No. 4,954,149) or clip (in U.S. patent No. 5,531,810) that is fixed to the duckbill valve assembly is biased to force the assembly closed. The first mechanism of closure assembly depends on the inherent elasticity of the rubber. As the rubber is exposed to elevated temperatures inside the GC inlet for extended periods of time, the rubber may harden and thus the elasticity may decrease over time. The second closure mechanism may not be sufficient to close adequately, especially when mechanical seals are used at lower pressures. Softer rubber is easier to relax and is more sensitive to air pressure but is also more sensitive to wear and hardening. Harder rubbers have greater wear resistance but are less prone to loosening and respond less to air pressure. Thus, these references rely on mechanical springs or clips to reliably close the duckbill valve assembly after withdrawal of the needle. However, mechanical springs and clips must be manufactured to precise tolerances and attached to the septum properly, as an overly stiff spring or an overly tight clip may increase wear of the septum, and an overly flexible or improperly attached spring or clip may not provide adequate sealing and allow for leakage. Furthermore, in prior art mechanical seals, the mechanical spring and clip are relatively expensive components and also add to the complexity of the product.

Another approach contemplated in U.S. patent No. 4,954,149 is to replace the metal spring with a pair of opposing radial ribs to close the duckbill. The ribs are comprised of a solid material adjacent the outer edge of the septum and disposed perpendicular to the duckbill orifice. This arrangement increases the friction on the elastomeric material, with the only way to relieve stress being to compress the rubber in a direction perpendicular to the slit. In this way, the ribs function similarly to using a solid material stopper, as both designs limit the deformation of the duckbill lip in a direction perpendicular to the slit when the needle is inserted.

Disclosure of Invention

It is an object of the present invention to reduce contamination in the GC inlet and provide an improved seal at low pressure by providing a novel duckbill septum. The duckbill septum includes a plurality of elastomeric ribs extending from the body of the septum to the duckbill valve assembly. When inserted into the injection end mouth, the force created by the interference fit between the body of the septum and the cavity is transferred through the ribs to the duckbill valve assembly, thereby providing a sealing force.

This summary is provided to introduce a selection of concepts that are further described in the detailed description and the drawings contained herein. This summary is not intended to identify any essential or essential features of the claimed subject matter. Some or all of the described features may be present in the respective independent or dependent claims, but should not be construed as limiting unless expressly recited in a particular claim. Each embodiment described herein is not necessarily intended to address each and every object described herein, and each embodiment does not necessarily include every feature described. Other forms, embodiments, objects, advantages, benefits, features, and aspects of the present invention will become apparent to one skilled in the art from the detailed description and drawings contained herein. Moreover, the various apparatus and methods described in this summary section, as well as elsewhere in this application, can be expressed in a number of different combinations and sub-combinations. All such useful, novel, and inventive combinations and sub-combinations are contemplated herein, and it is to be understood that express expressions of each of these combinations are not necessary.

Drawings

The invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings.

Figure 1A depicts a top perspective view of a first embodiment of a duckbill septum.

FIG. 1B depicts a bottom view of the spacer of FIG. 1A.

FIG. 1C depicts a side view of the spacer of FIG. 1A, with the opposite side being the same.

FIG. 1D depicts an end view of the spacer of FIG. 1A, with the opposite end being identical thereto.

FIG. 1E depicts a cross-sectional view of the spacer of FIG. 1A along line E-E of FIG. 1C.

Figure 2A depicts a top perspective view of a second embodiment of a duckbill septum.

FIG. 2B depicts a bottom view of the spacer of FIG. 2A.

FIG. 2C depicts a side view of the spacer of FIG. 2A, with the opposite side being the same.

FIG. 2D depicts an end view of the spacer of FIG. 2A, with the opposite side being the same.

FIG. 2E depicts a cross-sectional view of the spacer along line E-E of FIG. 2C.

Figure 2F is a photograph showing the interior surfaces of the duckbill valve assembly of the septum of the second embodiment after multiple injections.

FIG. 2G is a photograph showing a bottom view of the second embodiment septum with a needle extending through the valve assembly.

Figure 3A depicts a top perspective view of a third embodiment of a duckbill septum.

FIG. 3B depicts a bottom view of the spacer of FIG. 3A.

FIG. 3C depicts a bottom perspective view of the spacer of FIG. 3A.

FIG. 3D depicts a cross-sectional view of the spacer along line D-D of FIG. 3C.

FIG. 3E depicts a cross-sectional view of the spacer along line E-E of FIG. 3C.

FIG. 4 is a graph of the compressive stress (N/mm2 or MPa) experienced by the first and third embodiment spacers in a pressure environment of 1psi, 3psi, and 5 psi.

FIG. 5 is a graph of the compressive force (N/mm2 or MPa) experienced by the first and third embodiment spacers under pressure conditions of 20psi, 25psi, and 30 psi.

Figure 6A depicts a bottom view of a needle extending through a third party duckbill spacer.

FIG. 6B depicts a bottom side perspective view of the third spacer of FIG. 6A.

FIG. 6C depicts a bottom end perspective view of the third spacer of FIG. 6A.

Figure 7 is a schematic illustration of the contact forces applied to a needle extending through the first embodiment duckbill septum, the second embodiment duckbill septum and the third embodiment duckbill septum (left figure) and the third embodiment duckbill septum (right figure).

Figure 8 is a graph of von mises stress experienced by the septum of the first embodiment (simulating the duckbill septum of the second embodiment) (left view) and the septum of the third embodiment (right panel) with simulated spring forces upon needle insertion.

Figure 9A depicts a top perspective view of a fourth embodiment of a duckbill septum.

FIG. 9B depicts a bottom view of the spacer of FIG. 9A.

FIG. 9C depicts a bottom perspective view of the spacer of FIG. 9A.

FIG. 9D depicts a cross-sectional view of the spacer along line D-D of FIG. 9C.

FIG. 9E depicts a cross-sectional view of the spacer along line E-E of FIG. 9C.

FIG. 10 is a graph of the compressive stress (N/mm2 or MPa) experienced by the septum of the first embodiment and the septum of the fourth embodiment in a pressure environment of 1psi, 3psi, and 5 psi.

FIG. 11 is a graph of the compressive force (N/mm2 or MPa) experienced by the first and fourth embodiment spacers under pressure environments of 20psi, 25psi, and 30 psi.

Figure 12 is a graph of von mises stress experienced by the septum of the first embodiment (simulating the duckbill septum of the second embodiment) (left) and the septum of the fourth embodiment (right) with simulated spring forces upon needle insertion.

Detailed Description

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to selected embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended; any alterations and further modifications in the described or illustrated embodiments, and any further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the invention is shown in detail, although it will be apparent to those skilled in the art that some features or some combinations of features may not be shown for the sake of clarity.

Any reference herein to "the invention" is a reference to a series of embodiments of the invention and no single embodiment includes all features that are necessarily included in all embodiments, unless so stated. Moreover, although reference may have been made to "advantages" provided by some embodiments of the invention, other embodiments may not include those same advantages, or may include different advantages. Any advantages described herein should not be construed as limiting any claim.

Specific quantities (spatial dimensions, dimensionless parameters, etc.) may be used explicitly or implicitly herein and, unless otherwise indicated, are provided by way of example only and are approximations. Unless otherwise stated, discussion of a particular composition of matter (if any) is provided as an example only, and does not limit the applicability of other compositions of matter, particularly other matter having similar properties. The terms top and bottom as used herein refer to the orientation of the septum as shown in the drawings and to the movement of a needle inserted into the top of the septum, through the septum and emerging from the bottom. It should be understood that the spacer can be mounted on the fitting in a variety of orientations such that the insertion point "top" can be oriented laterally, angularly, or upside down.

Referring to figures 1A-1E, a first embodiment of a duckbill septum 10 is formed in two parts for ease of manufacture. The first portion 12 has axial symmetry and is generally cylindrical with a top end 14, a bottom end 16, sides 18 extending between the top and bottom ends 14, 16, a first diameter 20, and an axis 22 extending substantially perpendicular to the first diameter 20. The central bore 24 extends along the axis 22. The first portion 12 also includes a flange 28 extending from the side 18, the flange 28 having a second diameter 30 that is greater than the first diameter 20. In some embodiments, the central bore 24 includes at least one constriction 26, also referred to as a "wiper," along the length of the bore 24. These constrictions 26 act as a seal when the needle is inserted through the bore 24 and mechanically prevent dust from passing through the bore 24, thereby wiping dust from the needle as it passes sequentially through each constriction 26.

The second portion 32 of the duckbill septum 10 has bilateral symmetry and is generally cylindrical in shape having a top end 34, a bottom end 36, sides 38 extending between the top and bottom ends 34, 36, and a duckbill valve assembly 40 extending downwardly from the bottom end 36. An upper portion 42 of second portion 32 has a first diameter 44, a lower portion 46 of second portion 32 has a second diameter 48, and first diameter 44 is greater than second diameter 48. Axis 22 extends through second portion 32 substantially perpendicular to first diameter 44 and second diameter 48. The second portion 32 includes a recess 50, the recess 50 being sized and shaped to receive the flange 28 and the bottom end 16 of the first portion 12. The friction fit between the flange 28 and the recess 50 partially retains the first portion 12 within the second portion 32. The duckbill valve assembly 40 includes a slit 52 such that a needle can extend into the tip 14 of the first portion 12, through the central bore 24, into the recess 50, and through the duckbill valve assembly 40, protruding from the slit 52. The duckbill valve assembly 40 further includes a pair of opposing sides 54 and a surrounding notch 56.

The first embodiment of duckbill septum 10 was found to have undesirable leakage without a mechanical spring or other mechanism to assist in closing the duckbill valve assembly 40. As shown in table 1, duckbill septum 10 leaked immediately when subjected to only 1psi of pressure, leaked after about 300 injections when subjected to 5psi of pressure, and initially leaked when subjected to 3psi of pressure and/or leaked after 40 injections (tests were run in duplicate at 3 psi). The septum should preferably be injected at least one thousand times before a significant leak occurs.

Table 1: leak rate of first embodiment duckbill spacer-conditions: 1psi-5psi, 275 deg.C inlet, 1/4 turns of nut screw, first contact, 23 gauge conical point needle, and methanol injection. Leak rates were measured using a flowmeter that provided the leak rate (in milliliters per minute) and an electronic leak detector (showing 0 to up to 7 lamps as the leak rate increased).

Referring to figures 2A-2E, a second embodiment of a duckbill septum 110 is identical to the first embodiment 10, but also includes a mechanical spring 158. A spring 158 is located partially within the recess 56, surrounds the duckbill valve assembly, and includes a pair of arms 160, the pair of arms 160 contacting the opposing sides 54 of the duckbill valve assembly 40, applying a force biasing the duckbill valve assembly 40 closed. The spring 158 preferably exerts substantially equal and opposite forces on either side of the duckbill valve assembly 40 to keep the needle centered in the valve assembly 40. The spring 158 is preferably designed to exert sufficient force to reliably close the valve assembly 40 in the absence of a needle, but excessive force increases wear of the rubber duckbill valve assembly 40 as the needle is inserted and withdrawn. Figure 2F shows the interior of the duckbill valve assembly 40 of this second embodiment, and the wear due to repeated injections through the spring with excessive closing force. Material abraded from the valve assembly may cause particulate contamination in the GC and/or may prevent proper sealing of the duckbill valve assembly, thereby causing leakage. Figure 2G shows needle 162 eccentrically extending from the slit of the second embodiment duckbill septum 110 due to the asymmetric closing force provided by spring 158. In addition to these problems, mismounting of the spring 158 may result in accelerated wear of the spacer 110 or mechanical failure of the spring 158.

Referring to figures 3A-1E, a first embodiment of a duckbill septum 210 is formed in two parts for ease of manufacture. The first portion 12 in this third embodiment is substantially identical to the first portion 12 in the first and second embodiments 10 and 110. As with other designs, the first portion 12 has axial symmetry and is generally cylindrical with a top end 14, a bottom end 16, sides 18 extending between the top and bottom ends 14, 16, a first diameter 20, and an axis 222 extending between the top and bottom ends 14, 16 substantially perpendicular to the first diameter 20. The central bore 24 extends along an axis 222. In some embodiments, the central bore 24 includes at least one constriction 26 along the length of the bore 24. The first portion 12 also includes a flange 28 extending from the side 18, the flange 28 having a second diameter 30 that is greater than the first diameter 20.

The second portion 232 of the duckbill septum 210 has bilateral symmetry and is generally cylindrical in shape having a top end 234, a bottom end 236, and sides 238 extending between the top end 34 and the bottom end 234. An upper portion 242 of the second portion 232 has a first diameter 244 and a lower portion 246 of the second portion 232 has a second diameter 248, the first diameter 244 being greater than the second diameter 248. In some embodiments, the second diameter 248 is about 5.38mm, which results in an interference fit of about 0.075mm when inserted into a standard sized GC injection port. In some embodiments, the first diameter 244 of the upper portion 242 is about 8.50 mm. In certain embodiments, upper portion 242 has a height of about 1.5mm, and lower portion 246 has a height of about 3.94 mm. In other embodiments, the interference fit between the spacers 210 and the GC injection port may be achieved by other means, such as an internal sheath, radial forces in the GC injection port resulting from vertical compression of the spacers 210, or other means or mechanisms known in the art.

The axis extends through the second portion 232 substantially perpendicular to the first diameter 244 and the second diameter 248. The top end 234 of the second portion 232 includes a recess 250, the recess 250 being sized and shaped to receive the flange 28 and the bottom end 16 of the first portion 12. The friction fit between the flange 28 and the recess 250 partially retains the first portion 12 within the second portion 232. In other embodiments, the first portion 12 and the second portion 232 may be joined via an adhesive, chemical bond, or other means known in the art. When engaged, the first portion 12 and the second portion 232 are collectively referred to as the body of the spacer.

The bottom end 236 of the second portion 232 includes a cavity 264 defined by the generally cylindrical lower portion 246. Duckbill valve assembly 240 is positioned within cavity 264. As shown in fig. 3C, 3D and 3E, the duckbill valve assembly 240 is recessed from the bottom end 236 by about 0.28mm to avoid contact between the duckbill valve assembly 240 and the GC inlet. The duckbill valve assembly 240 includes a slit 252 so that the needle can extend into the top end 14 of the first portion 12, through the central bore 24, out of the bottom end 16 of the portion 12, into the recess 250, and through the duckbill valve assembly 240, out of the slit 252. A plurality of ribs 266 extend from duckbill valve assembly 240 to an inner wall 268 of cavity 264. In the depicted embodiment, two ribs 266 extend from each side 254 of the duckbill valve assembly 240, each spaced on either side of the axis 222.

In use, at least the lower portion 246 of the spacer 210 is positioned within the GC injection port. The predetermined interference fit between the septum 210 and the injection port mouth creates a compressive force that is transmitted from the side 238 through the ribs 266 to the opposing side 254 of the duckbill valve assembly 240. In some embodiments, pressures greater than about 0.5MPa on the interior sealing surface 270 of the duckbill valve assembly 240 provide adequate sealing, but pressures greater than about 2.5MPa tend to increase wear of the duckbill valve assembly 240 upon repeated injections. In other embodiments, where a harder or softer elastomeric material is used in the spacer 210, the higher or lower pressure may be sufficient to provide an adequate seal or may result in increased wear. The change in geometry of the ribs 266 may also be changed to enhance sealing at low pressures or to minimize wear during needle insertion and retraction, particularly at higher pressures.

As best seen in figures 3B and 3C, the geometry of the ribs 266 enables the duckbill valve assembly 240 to utilize multiple modes of relaxation, particularly compression, bending and stretching, during displacement of the needle. When the needle is inserted, compression occurs along the axis of each rib, relieving some of the stress that would otherwise cause undesirable wear. In addition, each rib 266 includes a relatively thin portion 267 secured to the duckbill valve assembly 240 and a relatively thick portion 269 secured to the interior wall 268, the thin portion 267 and thick portion 269 being arranged at non-parallel angles to form a geometric hinge point 271 along the length of the rib 266. In some embodiments, the width of thinner portion 267 is about 0.375mm, while the width of thicker portion 269 increases from about 0.375mm when it is in contact with thinner portion 267 to about 0.98mm when it is in contact with inner wall 268. As the needle is inserted through the duckbill valve assembly 240, the thinner portion 267 may deflect, causing the rib to bend around the hinge point 271. Together, these features allow the ribs 266 to deflect to accommodate the needle as it is inserted through the duckbill valve assembly 240. Finally, stretch relaxation is achieved along each side 254 of the duckbill valve assembly 240 because the material can deflect into the available space between the ribs 266 in a direction perpendicular to the slit 252 to accommodate the circumference of the needle. For this reason, the septum 210 includes two ribs 266 spaced on either side 254 of the duckbill valve assembly 240. In other embodiments, the spacer 210 may include additional or fewer ribs on each side 254, or may utilize curved ribs that are capable of bending.

The elastomeric ribs 266 also reduce the effects of wear at higher operating pressures because the ribs reduce the effective duckbill surface area exposed to the GC inlet internal pressure. The effect of reduced wear is significantly in the range of about 3psi to about 100psi of operating pressure. Further, the angle of the ribs 266 with the needle allows for additional contact area between the sealing surface 270 and the needle, reducing the compression force concentration from two points to four points. The reduction in compressive force on the duckbill valve assembly 240 at higher pressures thus results in reduced wear on the sealing surface 270. Also, the angle of the ribs 266 relative to the needle provides additional centering because the needle is supported by four points, rather than only two points as in previous designs. In the depicted embodiment, the thinner portion 267 of each rib 266 is oriented at an angle of approximately 67.5 degrees relative to the slot 252. In other embodiments, the angle may not be perpendicular to the slit (i.e., not 90 degrees), between 5 degrees and 85 degrees, or between 30 degrees and 75 degrees, depending on the desired characteristics of the spacer 210. For example, higher angles may more effectively transmit compressive forces to a duckbill valve assembly and may be more suitable for use in spacers for GC operating at lower pressures, while lower angles may be more suitable for use in spacers for GC operating at higher pressures.

Experimental evidence indicates that the third embodiment of the duckbill septum exhibits better performance in closing the duckbill valve assembly than the first embodiment (lacking springs or ribs to facilitate closing). Referring now to fig. 4, finite element analysis was used to verify the effectiveness of the interference fit concept at low pressure sealing. The analysis shows a top view of the duckbill seal lip depicting compressive stress in the direction of the sealing surface, as compared to the first and third embodiments of the duckbill septum. Without being bound by theory, it is assumed that the higher the compressive stress acting on the sealing surface, the better the sealing performance at low operating pressures. In these results, white indicates essentially no compressive stress, while dark color indicates higher compressive stress. The results show that the duckbill spacer of the third embodiment provides a greater compressive stress of the duck lips at 1psi than the duckbill spacer 10 of the first embodiment at 5 psi.

Referring now to figure 5, finite element analysis shows a reduction in the compressive stress of the third embodiment of the duckbill septum in the direction of the sealing surface, as compared to the first embodiment. The analysis shows a top view of the duckbill seal lip depicting compressive stress in the direction of the sealing surface, as compared to the first and third embodiments of the duckbill septum. In these results, white indicates essentially no compressive stress, while dark color indicates higher compressive stress. The results show that the third embodiment of the duckbill septum was calculated to provide a compressive stress at 30psi similar to the first embodiment of the duckbill septum at 20 psi. At these higher pressures, lower compressive stresses are preferred to reduce wear.

The duckbill valve assembly deforms around the needle as the needle is inserted into the assembly. Figures 6A, 6B and 6C show the third party duckbill spacer 310 deformed around needle 362 to produce a convex "diamond" shape. This deformation is based on two contact points between the needle 362 and the spacer 310 on opposite sides of the slit 352. This arrangement of forces is schematically illustrated in the diagram in fig. 7. In contrast, as shown in the right drawing of figure 7, the third embodiment of the duckbill septum deforms around four contact points corresponding to the locations of the ribs.

Finite element analysis shows that the von mises stress of the first embodiment duckbill spacer is reduced compared to the third embodiment duckbill spacer, assuming an applied spring force of 0.15N (simulating the action of the spring, as in the second embodiment duckbill spacer), as the needle is inserted into each of the spacers. Figure 8 shows a bottom view of a corresponding spacer depicting von mises stress. In these results, white indicates substantially no von mises stress, while dark indicates more von mises stress. As shown, the duckbill spacer of the third embodiment not only has a lower von mises stress concentration, but also has better needle centering due to the increased contact points.

Referring to figures 9A-9E, a fourth embodiment of a duckbill septum 310 is formed in two parts for ease of manufacture. The first portion 312 in this fourth embodiment is generally similar to the first portion 12 in the first, second and third embodiments 10, 110, 210, but includes a shortened upper portion above the flange 328. As with other designs, the first portion 312 has axial symmetry and is generally cylindrical with a top end 314, a bottom end 316, sides 318 extending between the top and bottom ends 314, 316, a first diameter 320, and an axis 322 extending between the top and bottom ends 314, 316 substantially perpendicular to the first diameter 320. A central bore 324 extends along axis 322. In some embodiments, the central bore 324 includes at least one constriction 326, also referred to as a "wiper," along the length of the bore 324. These constrictions 326 act as a seal when the needle is inserted through the bore 324 and mechanically prevent dust from passing through the bore 324, thereby wiping dust from the needle as it passes through each constriction 326 in turn. The first portion 312 also includes a flange 328 extending from the side 318, the flange 328 having a second diameter 330 that is greater than the first diameter 320.

The second portion 332 of the duckbill septum 310 has bilateral symmetry and is generally cylindrical with a top end 334, a bottom end 336, and sides 338 extending between the top end 34 and the bottom end 334. The upper portion 342 of the second portion 332 has a first diameter 344, the lower portion 346 of the second portion 332 has a second diameter 348, and the first diameter 344 is greater than the second diameter 348. In some embodiments, the second diameter 348 is about 10.35mm, which results in an interference fit of about 0.145mm when inserted into a standard sized GC injection port. In some embodiments, the first diameter 344 of the upper portion 342 is about 11.72 mm. In certain embodiments, the upper portion 342 has a height of about 1.75mm, while the lower portion 346 has a height of about 2.9 mm. In other embodiments, the interference fit between the spacers 310 and the GC injection port may be achieved by other means, such as an inner sheath, radial forces in the GC injection port resulting from vertical compression of the spacers 310, or other means or mechanisms known in the art.

The axis extends through the second portion 332 substantially perpendicular to the first diameter 344 and the second diameter 348. The top end 334 of the second portion 332 includes a recess 350, and the recess 250 is sized and shaped to receive the flange 328 and the bottom end 316 of the first portion 312. The friction fit between the flange 328 and the recess 350 partially retains the first portion 312 within the second portion 332. In other embodiments, first portion 312 and second portion 332 may be joined via an adhesive, chemical bond, or other means known in the art. When engaged, the first portion 312 and the second portion 332 are collectively referred to as the body of the spacer.

The bottom end 336 of the second portion 332 includes a cavity 364 defined by the generally cylindrical lower portion 346. The duckbill valve assembly 340 is positioned within the cavity 364. As shown in fig. 9C, 9D and 9E, the duckbill valve assembly 340 is recessed from the bottom end 336 by about 0.55mm to avoid contact between the duckbill valve assembly 340 and the GC inlet. The duckbill valve assembly 340 includes a slit 352 such that a needle can extend into the top end 314 of the first portion 312, through the central bore 24, out of the base assembly 340, and out of the slit 352.

A plurality of ribs 366 extend from the duckbill valve assembly 340 to an inner wall 368 of the cavity 364. In the depicted embodiment, two ribs 366 extend from each side 354 of the duckbill valve assembly 340, each rib being spaced on either side of the axis 322.

In use, at least the lower portion 346 of the spacer 310 is positioned within the GC injection port. The predetermined interference fit between the septum 310 and the injection port creates a compressive force that is transmitted from the side 338 through the ribs 366 to the opposing side 354 of the duckbill valve assembly 340. As noted in connection with the third embodiment spacer 210, pressures greater than about 0.5MPa on the interior sealing surface 370 of the duckbill valve assembly 340 provide an adequate seal, but pressures greater than about 2.5MPa tend to increase wear of the duckbill valve assembly 340 upon repeated injections. In other embodiments, where harder or softer elastomeric materials are used in the spacer 310, higher or lower pressures may be sufficient to provide adequate sealing or may result in increased wear. The change in geometry of the ribs 366 may also be changed to enhance sealing at low pressures or to minimize wear during needle insertion and retraction, particularly at higher pressures.

As best seen in figures 9B and 9C, the geometry of the ribs 366 enables the duckbill valve assembly 340 to utilize a variety of relaxation modes, particularly compression, bending and stretching, during displacement of the needle, as described above in connection with the third embodiment septum 310. When the needle is inserted, compression occurs along the axis of each rib, relieving some of the stress that would otherwise cause undesirable wear. Each rib 366 includes a relatively thin portion 367 secured to the duckbill valve assembly 340 and a relatively thick portion 369 secured to the inner wall 368, the thin portion 367 and the thick portion 369 being arranged at non-parallel angles to form a geometric hinge point 371 along the length of the rib 366. In some embodiments, the width of the thinner portion 367 is about 0.375mm, while the width of the thicker portion 369 increases from about 0.375mm when it is in contact with the thinner portion 367 to about 2.11mm when it is in contact with the inner wall 368. The thinner portion 367 may deflect as the needle is inserted through the duckbill valve assembly 340, causing the rib to bend around the hinge point 371. Together, these features allow the ribs 366 to deflect to accommodate the needle as it is inserted through the duckbill valve assembly 340. Finally, stretch relaxation is achieved along each side 354 of the duckbill valve assembly 340 because the material can deflect into the available space between the ribs 366 in a direction perpendicular to the slit 352 to accommodate the circumference of the needle. For this reason, the septum 310 includes two ribs 366 spaced on either side 354 of the duckbill valve assembly 340. In other embodiments, the spacer 310 may include additional or fewer ribs on each side 354, or may utilize curved ribs that are capable of bending.

The elastomeric ribs 366 may also reduce the effects of wear at higher operating pressures because the ribs reduce the effective duckbill surface area exposed to the pressure inside the GC inlet. The effect of reduced wear is significantly in the range of about 3psi to about 100psi of operating pressure. Further, the angle of the ribs 366 to the needle allows for additional contact area between the sealing surface 370 and the needle, thereby reducing the compression force concentration from two points to four points. The reduction in the compressive force on the duckbill valve assembly 340 at higher pressures thus results in reduced wear on the sealing surface 370. Also, the angle of the ribs 366 relative to the needle provides additional centering because the needle is supported by four points, rather than only two points as in previous designs. In the depicted embodiment, the thinner portion 367 of each rib 366 is oriented at an angle of approximately 60 degrees relative to slit 352. In other embodiments, the angle may not be perpendicular to the slit (i.e., not 90 degrees), between 5 degrees and 85 degrees, or between 30 degrees and 75 degrees, depending on the desired characteristics of the spacer 310. For example, higher angles may more effectively transmit compressive forces to a duckbill valve assembly and may be more suitable for use in spacers for GC operating at lower pressures, while lower angles may be more suitable for use in spacers for GC operating at higher pressures.

Experimental evidence indicates that the fourth embodiment of the duckbill septum exhibits better performance in closing the duckbill valve assembly than the first embodiment (lacking springs or ribs to facilitate closing). Referring now to fig. 10, finite element analysis was used to verify the effectiveness of the interference fit concept at low pressure sealing. In comparison to the first and fourth embodiments of the duckbill septum, the analysis shows a top view of the duckbill seal lip depicting compressive stress in the direction of the sealing surface. Without being bound by theory, it is assumed that the higher the compressive stress acting on the sealing surface, the better the sealing performance at low operating pressures. In these results, white indicates essentially no compressive stress, while dark color indicates higher compressive stress. The results show that the duckbill spacer of the fourth example provides a duck lip compressive stress at 1psi that is greater than the compressive stress achieved by the duckbill spacer 10 of the first embodiment at 5 psi.

Referring now to figure 11, finite element analysis shows a reduction in the compressive stress of the fourth embodiment of the duckbill septum in the direction of the sealing surface, as compared to the first embodiment. In comparison to the first and fourth embodiments of the duckbill septum, the analysis shows a top view of the duckbill seal lip depicting compressive stress in the direction of the sealing surface. In these results, white indicates essentially no compressive stress, while dark color indicates higher compressive stress. The results show that the fourth embodiment of the duckbill septum was calculated to provide a compressive stress at 30psi similar to the first embodiment of the duckbill septum at 20 psi. At these higher pressures, lower compressive stresses are preferred to reduce wear.

Finite element analysis shows that the von mises stress of the first embodiment duckbill spacer is reduced compared to the fourth embodiment duckbill spacer, assuming an applied spring force of 0.15N (simulating the action of the spring, as in the second embodiment duckbill spacer), as the needle is inserted into each of the spacers. Figure 12 shows a bottom view of a corresponding spacer depicting von mises stress. In these results, white indicates substantially no von mises stress, while dark indicates more von mises stress. As shown, the duckbill spacer of the fourth embodiment not only has a lower von mises stress concentration, but also has better needle centering due to the increased contact points.

As will be apparent to those skilled in the art after reviewing the present disclosure, modifications to rib thickness, rib geometry, or interference fit will allow the duckbill valve assembly 240, 340 to accept various gauges of blunt/bullet needle types and to adjust desired performance characteristics, such as the operable pressure range and wear rate (by adjusting the closing force). The third and fourth embodiments of the spacers 210, 310 disclosed herein are shaped and dimensioned to fit two common types of GC inlets. It should be understood that other embodiments or modifications of the disclosed embodiments may be used to adapt other sized GC inlets. Furthermore, tests have shown that rib-engaging area ratios in the range of 1.0625 to 3.50 provide better performance levels in the third and fourth embodiments of the spacers 210, 310. The ratio of the area that the ribs engage is defined as the surface area of the ribs 266, 366 that engages the inner walls 268, 368 of the cavities 264, 364 divided by the surface area of the ribs 266, 366 that engages the duckbill valve assembly 240, 340.

Various aspects of different embodiments of the present disclosure are represented in paragraphs X1, X2, and X3, as follows:

x1: one embodiment of the present disclosure includes a spacer, comprising: a body formed of a resilient elastomeric material, the body including a central axis; a cavity in the body, the cavity comprising an inner wall; a duckbill valve assembly in the chamber; and a plurality of ribs extending from the duckbill valve assembly to the interior wall.

X2: another embodiment of the present disclosure includes a method of using a gas chromatography spacer, the method comprising: providing a spacer having a body formed of an elastomeric material, the body having: a top end; a bottom end; and at least one side extending between the top end and the bottom end; a cavity in the bottom end, the cavity comprising an inner wall; a duckbill valve assembly in the cavity, the duckbill valve assembly including a slit; and a plurality of ribs extending from the duckbill valve assembly to the inner wall, wherein each of the plurality of ribs extends from the duckbill valve assembly at a non-perpendicular angle relative to the slit; and inserting the bottom end into a GC injection port, wherein the interference fit between the GC injection port and the body applies a compressive force to the sides that is transmitted through the ribs to the duckbill valve assembly.

X3: another embodiment of the present disclosure includes a method of using a gas chromatography spacer, the method comprising: providing a spacer having a body formed of an elastomeric material, the body having: a top end; a bottom end; and at least one side extending between the top end and the bottom end; a cavity in the bottom end, the cavity comprising an inner wall; a duckbill valve assembly in the chamber; and a plurality of ribs extending from the duckbill valve assembly to the inner wall, wherein each of the plurality of ribs extending from the duckbill valve assembly includes a hinge point; and inserting the bottom end into a GC injection port, wherein the interference fit between the GC injection port and the body applies a compressive force to the sides that is transmitted through the ribs to the duckbill valve assembly.

Other embodiments include features described in any of the preceding paragraphs X1, X2, or X3 in combination with one or more of the following:

wherein the duckbill valve assembly is recessed from the bottom end in the cavity.

Wherein the body includes a first portion having a top end, a bottom end, sides extending between the top and bottom ends, and flanges extending from the sides, and a second portion having a top end, a bottom end, sides extending between the top and bottom ends, and a recess in the top end sized and shaped to receive the flanges and bottom end of the first portion.

Wherein the cavity is located at the bottom end of the second portion.

Wherein the duckbill valve assembly is recessed within the cavity from the bottom end of the second portion.

Wherein the first portion includes a central bore extending along the central axis.

Wherein the central bore comprises at least one constriction.

Wherein the duckbill valve assembly includes a slit and wherein the septum pad is configured such that a needle may be sequentially inserted into the top end of the first portion, through the central bore, the bottom end of the first portion, the recess, and the duckbill valve assembly, and out of the slit.

Wherein the duckbill valve assembly comprises a slit, and wherein the septum is configured such that a needle may be inserted sequentially along the central axis into the bottom end of the first portion, through the central bore, the bottom end of the first portion, the recess, and the duckbill valve assembly, and out of the slit.

Wherein the second portion is generally cylindrical and includes an upper portion having a first diameter and a lower portion having a second diameter, the first diameter being greater than the second diameter, and wherein the second diameter is sized to fit at least partially within the gas chromatograph injection port.

Wherein each of the plurality of ribs includes a hinge point.

Wherein each of the plurality of ribs comprises a thinner portion attached to the duckbill valve assembly and a thicker portion attached to the inner wall.

Wherein a rib-engaging area ratio of each of the plurality of ribs is in a range of 1.0625 to 3.50.

Wherein the duckbill valve assembly includes a pair of opposing sides and includes a slit, and wherein at least one rib extends from each side of the duckbill valve assembly at a non-perpendicular angle relative to the slit.

Wherein the angle is in the range of 5 degrees to 85 degrees.

Wherein the angle is in the range of 30 degrees to 75 degrees.

Wherein at least two ribs extend from each side of the duckbill valve assembly, the ribs being spaced apart from each other.

Further comprising inserting a needle into a top end of the septum and through the duckbill valve assembly, the needle extending from the slit, wherein during said inserting, each of the plurality of ribs bends around a hinge point in each rib.

Further comprising inserting a needle into a top end of the septum and through the duckbill valve assembly, wherein each of the plurality of ribs bends around a hinge point in each rib during said inserting.

The foregoing detailed description has been given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modifications may be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention. Although specific spatial dimensions are illustrated herein, these specific numbers are given by way of example only. If used herein, the reference system generally refers to various directions (e.g., top, bottom, upper, lower, forward, rearward, leftward, rightward, etc.) that are only used to aid the reader in understanding the various embodiments of the present disclosure, and should not be construed as limiting. Other reference systems may be used to describe various embodiments.