WO2002036182A2

WO2002036182A2 - Septum with chamfer and linear pre-piercing

Info

Publication number: WO2002036182A2
Application number: PCT/US2001/049877
Authority: WO
Inventors: David L. Jones; Glenn E. Thomas
Original assignee: Chromatography Research Supplies, Inc.
Priority date: 2000-11-03
Filing date: 2001-11-01
Publication date: 2002-05-10
Also published as: WO2002036182A3

Abstract

A disc-shaped self-sealing septum (10) for use in the injection port of a gas chromatoraphy system, having a generally conically shaped chamfered indentation (40) extending partially toward the bottom surface (26) of the septum (10) and a linear pre-piercing (50) extending from the bottom end (44) of the chamfered indentation (40) toward the bottom surface (26) of the septum member (10). The linear per-piercing (50) is sized to receive an elongated member for injection of a sample into the system. The beveled sidewalls of the chamfered indentation (40) guide the tip of the elongated member to the linear pre-piercing (50), and the linear pre-piercing (50) allows the elongated member to travel a consistent path during repetitive injections through the septum (10), thereby minimizing damage to the septum (10).

Description

SEPTUM WITH CHAMFER AND LINEAR PRE-PIERCING

This application claims the benefit of U.S. Utility Application No. 09/705310, filed 03 November 2000. TECHNICAL FIELD

The present invention relates to a self-sealing septum having a generally conically shaped chamfered indentation with a linear pre-piercing extending from the bottom end of the chamfered indentation toward the bottom surface of the septum, the linear pre-piercing sized to receive an elongated member. The pre-piercing may extend through the septum. BACKGROUND ART

Septa are used in gas chromatography systems as part of an injection port for the introduction of a sample into the system through an elongated member, such as a hollow needle attached to a syringe. The septum provides a point of access to inject the sample into the system, separates the internal environment in the gas chromatography system from the external environment, and also functions to prevent the escape of gas from the system.

To inject a sample into the system, the needle is inserted completely through the septum, the syringe piston is depressed to expel the sample into the system, and then the needle is immediately withdraw from the septum. The septum forms a seal with the outside of a needle when the needle is inserted into the septum, and the septum reseals itself when the needle is withdrawn, preventing escape of gas through the septum.

The sample may be injected manually or by an auto sampler, which is used when multiple samples must be analyzed. An auto sampler automatically draws up the required amount of the sample from a sealed vial and injects it through the septum. The auto sampler may inject and then withdraw the needle from the septum very rapidly, such as in a fraction of a second. After a run has been completed, the auto sampler then automatically injects the next sample. A septum may be penetrated a multiplicity of times during normal use.

Syringe needles used for gas chromatography are usually made from stainless steel. Various sized needles with various shaped and sized needle tips can be used, including tips having a beveled, rounded or blunt shape.

Septa are produced in an array of sizes to fit a variety of makes, models and injection systems for gas chromatography systems. Septa are usually shaped in the form of thin, generally circular, discs and are generally sized to fit injection ports with diameters ranging from five millimeters to seventeen millimeters (0.195 - 0.663 inches), although they may be of any needed size. A septum is generally mounted horizontally in a recess in the injection port. A septum nut is then screwed down onto the injection port to clamp the septum in place. The septum nut may contain a needle guide to assist in positioning the needle for injection into the septum. Septa which will be pierced multiple times during sample injection are generally composed of one or more layers of elastomer materials which will reseal after perforation by a needle. The elastomer material used may be one or a combination of layers of butyl rubber, silicone rubber, PTFE, or any other suitable elastomer material.

The main factors that affect septum life include: temperature, condition and type of the needle, and the precision of the placement of repetitive injections. The septum's ability to reseal and the integrity of the septum itself are lessened over time as the number of needle penetrations increases. Needles may core or tear a small amount of elastomer material from the septum as they are injected through the septum, and it is common for some elastomer material to disappear from the region of penetration during a series of injections. In cases of coring, chunks of elastomer material have been punched out of the septum. When the syringe piston is pushed in during injection, the chunks of septum material may be injected into the system with the sample. This damage to the septum can result in gas leakage from the system and may also cause sorption and bleed complications as a result of septum material being forced into the system.

Penetrations at different closely spaced positions can join together, greatly weakening the septum. Penetration of the needle in the same spot each time minimizes damage to the septum and extends the life of the septum. Some septa are pre-pierced prior to injection to provide a pre-determined penetration site. Some different septa have a pre-drilled hole partway through which functions as a needle guide. Some different septa are protected by a layer of rigid material, such as stainless steel, which contains a guide hole for the needle to pass through.

Great Britain Patent Application 2336316A, filed by Smiths Industries Public Limited Company, teaches a self- sealing septa having a double seal involving an outer member 13 and an inner member 1 . These members include respective pierced passages 16 and 18 therethrough, which are preferably formed by piercing without removal of material. In use, as seen in Figure 3, pressure keeps member 14 adjacent member 13, thereby compressing passage 18.

French Patent Application 2767583, filed by Junior Instruments Societe Anonyme, teaches a septum 4 having a spherical indentation 5, seen in Figure 1, for reducing the thickness which a needle must penetrate. Figure 2 shows the downward bowing of the septa when needle 7 is inserted, and Figure 3 shows the upward movement when the needle is removed.

U.S. Pat. No. 3915677, to Asbjorn, teaches an injector with at least two septa for gas chromatographic apparatus and other equipment. The two or more septa are arranged in relative positions so that a hollow needle first penetrates one septum whereby the tip of the needle enters the interior of the injection chamber. Thereafter, the needle is forced through a second septum whereupon the tip of the needle appears on the outside of the chamber where the needle can be cleaned of any material torn from the septa before being retracted into the injection chamber for injection of the sample .

U.S. Pat. No. 3693455, to Frederick et al . , teaches a sample injection device having two septa, each backed by a disc of rigid material having a needle hole therethrough. The septa are preferably of silicone rubber and the disc of stainless steel.

All tech U6401 Data Sheet for a Septum Needle Guide teaches a septum with a cylindrical pre-drilled hole partway through the septum to function as a needle guide.

Choosing Septa Wisely, by Scientific Resources, Inc. (SRi) , discloses pre-scored septa composed of layers of silicone and PTFE which are scored only through the silicone rubber layer and discloses that other septa makers score through the whole septa.

Applicant is aware of no prior art where a septum contains a pre-piercing and a generally conically shaped chamfered indentation which functions to guide an elongated member to the first end of the pre-piercing. DISCLOSURE OF THE INVENTION

The present invention relates to a disc-shaped self- sealing septum for use in the injection port of a gas chromatography system which has a generally conically shaped chamfered indentation with a linear pre-piercing extending from the bottom end of the chamfered indentation toward the bottom surface of the septum member, the linear pre-piercing sized to receive an elongated member for injection of a sample into the system. The chamfered indentation extends partially through the septum member toward the bottom surface of the member. The septum has a linear pre-piercing to allow the elongated member to travel a consistent path to minimize damage to the septum through repetitive injections through the septum. The linear pre-piercing is connected to the bottom end of the chamfered indentation and preferably extends through the member to the bottom surface. The beveled sidewalls of the chamfered indentation slope toward the first end of the linear pre-piercing and act as a guide to direct the tip of the elongated member to the linear pre- piercing. The septum is composed of a resilient elastomer material which flexes and spreads to receive and form a seal around the elongated member and reseals after the elongated member is withdrawn. Alternatively, the linear pre-piercing may not extend completely to the bottom surface, which would allow the elongated member to penetrate the septum member to complete a consistent path through the septum on first insertion.

It is an object of the present invention to overcome the shortcomings of the prior art devices described above. It is a further object of the present invention to provide a self-sealing septum which provides a consistent path through the septum to minimize damage to the^' septum.

It is a further object of the present invention to minimize or eliminate complications caused by damage to the septum, such as gas leakage.

More particularly, the septum of the present invention comprises a member, the member having a top surface, a bottom surface, the top surface having a center; a chamfered indentation in the member, the chamfered indentation having a substantially conical shape, the chamfered indentation having a top end, a bottom end and beveled sidewalls, the chamfered indentatipn located on the member top surface, the chamfered indentation extending from the member top surface partway toward the member bottom surface; and a linear pre-piercing in the member, the linear pre-piercing having a first end, a length, and a second end, the first end of the linear pre- piercing located toward the chamfered indentation bottom end, the length of the linear piercing extending at least partially towards the member bottom surface. Even more particularly, the preferred embodiment of the present invention comprises a generally disc-shaped self- sealing septum sized for use in the injection port of a gas chromatography system, where the septum is composed of silicone rubber, and where the septum comprises a member, the member having a top surface, a bottom surface, the top surface having a center; a chamfered indentation in the member, the chamfered indentation having a substantially conical shape, the chamfered indentation having a top end, a curved bottom end and beveled sidewalls, the chamfered indentation located on the member top surface substantially in the center of the top surface, the chamfered indentation extending from the member top surface partway toward the member bottom surface, the chamfered indentation top end having a greater diameter than the chamfered indentation bottom end; and a linear pre-piercing in the member, the linear pre-piercing having a first end, a length, and a second end, the first end of the linear pre-piercing located toward the chamfered indentation bottom end, the length of the linear piercing extending completely to the member bottom surface, where the linear pre-piercing is formed by penetration of the member without removal of material, where the linear pre-piercing receives and seals around an elongated member when said elongated member is extended axially therein, and where the linear pre-piercing seals closed when the elongated member is withdrawn. BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings, wherein: Figure 1 shows a top perspective view of the septum of the preferred embodiment of the present invention, which has a chamfered indentation extending from the top surface of the septum member toward the bottom surface and a linear pre- piercing, extending completely from the bottom end of the chamfered indentation, through the second thickness of the septum member, to the bottom surface of the member;

Figure 2 shows a top view of the septum of Figure 1; Figure 3 shows a bottom view of the septum of Figure 1; Figure 4 shows a cross-sectional view of the septum of Figures 1-3 along the lines 4-4 of Figure 2, where the complete linear pre-piercing is shown in cross-section; and Figure 5 shows a cross sectional view of the septum of Figures 1-3 along the lines 4-4 of Figure 2 where an elongated member is received within the linear pre-piercing. Figure 6 shows a cross-sectional vi'ew of a modified form of the septum disclosed in Figure 1 along the lines 4-4 of Figure 2, where the linear pre-piercing extends only partially through the second thickness of the member toward the bottom surface of the septum member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the Figures, Figure 1 shows the septum 10 of the instant invention having a generally disc shaped member 20 with a top surface 22, a bottom surface 26, a first thickness 30, and a second thickness 32. The first thickness 30 of member 20 extends from the member 20 top surface 22 to the member 20 bottom surface 26. The top surface 22 has a center area 24. A chamfered indentation 40 is located in the top surface 22 of the member 20, preferably in the center area 24 of the top surface 22, as shown in Figures 1-2 and 4- 5; however, the chamfered indentation 40 may be located at any point on the member 20 top surface 22.

As shown in Figures 1, 4 and 5, the chamfered indentation 40 extends partially through the first thickness 30 of the member 20 toward the member 20 bottom surface 26. The second thickness 32 extends from the chamfered indentation 40 bottom end 44 to the member 20 bottom surface 26, along the length of a linear pre-piercing 50. The chamfered indentation 40 has a substantially conical shape and has a top end 42, a bottom end 44 and beveled sidewalls 46 with the diameter of the top end 42 being greater than the diameter toward the bottom end 44.. The chamfered indentation 40 bottom end 44 is preferably curved and is preferably curved toward the member 20 bottom surface 26. If curved rather than angular, the bottom end 44 preferably has a diameter of at least 0.256 millimeters (0.01 inches).

The septum 10 has a linear pre-piercing 50 having a first end 52, a length 54 and a second end 56 connected to the chamfered indentation 40. The first end 52 of the linear pre-piercing 50 is located toward the chamfered indentation ^'40 bottom end 44. The first end 52 of the linear pre- piercing 50 may be located on any part of the bottom end 44 but is preferably located at a point nearest to the bottom surface 26 of the member 20. The linear pre-piercing 50 preferably extends completely through the second thickness 32 of member 20, so that second end 56 is located at the bottom surface 26 of member 20, as shown in Figures 3-5.

As shown in Figure 5, the linear pre-piercing 50 is sized to receive an elongated member 2, such as a hollow needle or a capillary tube, extending axially therein. The top end 42 of the chamfered indentation 40 is wide enough to easily accept the elongated member 2 and preferably has a diameter of approximately one millimeter (0.039 inches). The beveled sidewalls 46 of the chamfered indentation 40 slope toward the first end 52 of the linear pre-piercing 50 and act as a guide to direct the tip 4 of the elongated member 2 to the first end 52 of the linear pre-piercing 50. The complete linear pre-piercing 50 provides the elongated member 4 with a consistent path as it 'travels through the septum 10. The septum 10 is composed of a resilient elastomer material, preferably silicone rubber, which is preferably also resistant to high temperature. When the tip 4 of the elongated member 2 is pressed against the first end 52 of the linear pre-piercing 50, the sides of the linear pre-piercing 50 first end 52 flex and spread to receive the elongated member 2, 'as does the length 54 of the linear pre-piercing 50 as the elongated member 2 is pushed through the linear pre- piercing 50. The elastomer material of the member 20 then embraces the elongated member 2 to form a seal around the elongated member 2. The tip 4 of the elongated member 2 may be pressed through the length 54 of the linear pre-piercing 50 toward and then past the linear pre-piercing 50 second end 56 until the tip 4 protrudes beyond the bottom surface 26 of member 20. After the sample material is injected into the gas chromatography system through the elongated member 2, the elongated member 2 may be pulled back through the linear pre- piercing 50, which then seals closed when the elongated member 2 is withdrawn from the linear pre-piercing 50 due to the resilient qualities of the elastomer material. The linear pre-piercing 50 allows an elongated member 2 to be repetitively inserted through and then withdrawn from the septum 10 with minimal damage to or loss of elastomer material from the septum 10. The beveled sidewalls 46 of the chamfered indentation 40 guide the tip 4 of the elongated member 2 to the first end 52 of the linear pre-piercing 50, greatly increasing the likelihood that the elongated member 2 will travel a consistent path and be inserted through the septum 10 in the same place during each injection.

The member 20 of the septum 10 of the preferred embodiment, shown in Figures 1-5, is formed by introducing the elastomer material, heated into liquid form, through a small gate hole into a mold. The mold is shaped to produce a generally disc shaped member 20 with a chamfered indentation 40 in the center 24 of the top surface 22 of the member 20. The member 20 is generally disc shaped, but may be of any geometric shape and size to fit an injection port of a gas chromatography system. After the elastomer material has cooled, the member 20 is removed from the mold and placed on a jig with the member 20 bottom surface 26 supported by the jig surface. The member 20 is positioned on the jig surface over a hole in the jig surface which preferably has a diameter of approximately 1.6 millimeters (0.0625 inches). The linear pre-piercing 50 is then formed by passing a solid needle through the bottom end 44 of the chamfered indentation 40 toward and through the bottom surface 26 of the member 20 and then through the hole in the jig surface. The solid needle used to create the linear pre-piercing 50 preferably has a size 23 AWG (0.573 millimeters) body with a beveled tip which tapers to a fine point. The solid needle penetrates the member 20 and creates a split in the elastomer material as it passes through the member 20. No material is removed from the member 20 by the solid needle as it creates the linear pre-piercing 50, which allows the sides of the linear pre-piercing 50 to seal together when the elongated member 2 is withdrawn from the linear pre-piercing 50.

Alternatively, the linear pre-piercing 50 may also be formed during molding of the septum 10 member 20 by shaping the mold body to have a thin linear projection which creates the pre-piercing 50 in the finished molded member 20. The elongated member 2 used for sample injection preferably has a maximum size of 23 AWG (0.573 millimeters) and preferably has a rounded or blunt tip 4 with a maximum size of 26 AWG (0.405 millimeters) to allow the elongated member 2 to be received by the linear pre-piercing 50 with a minimum of friction or abrasion.

Figure 6 shows a cross-sectional view of a modified form of the present invention where the partial linear pre- piercing 150 extends only partially through the second thickness 132 of the member 120 toward the bottom surface 126 of the septum 110 member 120. The generally disc shaped member 120 has a top surface 22, a bottom surface 126, a first thickness 30, and a second thickness 32. The first thickness 30 of member 120 extends from the member 20 top surface 22 to the member 120 bottom surface 126. The top surface 22 has a center area 24. A chamfered indentation 40 is located in the top surface 22 of the member 120, preferably in the center area 24 of the top surface 22; however, the chamfered indentation 40 may be located at any point on the member 120 top surface 22. The chamfered indentation 40 extends partially through the first thickness 30 of the member 120 toward the member 120 bottom surface 126.' The second thickness 132 extends from the chamfered indentation 40 bottom end 44 to the member 120 bottom surface 126. The chamfered indentation 40 has a substantially conical shape and has a top end 42, a bottom end 44 and beveled sidewalls 46 with the diameter of the top end 42 being greater than the diameter toward the bottom end. The chamfered indentation 40 bottom end 44 is preferably curved and is preferably curved toward the member 120 bottom surface 126. If curved rather than angular, .the bottom end 44 preferably has a diameter of at least 0.256 millimeters (0.01 inches) .

The septum 110 has a partial linear pre-piercing 150 having a first end 52, a length 154 and a second end 156 connected to the chamfered indentation 40. The first end 52 of the partial linear pre-piercing 150 is located toward the chamfered indentation 40 bottom end 44. The first end 52 of the partial linear pre-piercing 150 may be located on any part of the bottom end 44 but is preferably located at a point nearest to the bottom surface 126 of the member 120. The partial linear pre-piercing 150 extends only partially through the second thickness 132 of member 120, so that second end 156 is located within the second thickness 132, ■ rather that at the bottom surface 126 of member 120. The partial linear pre-piercing 150 is sized to receive an elongated member 2, such as a hollow needle or a capillary tube, extending axially therein. The top end 42 of the chamfered indentation 40 is wide enough to easily accept the elongated member 2 and preferably has a diameter of approximately one millimeter (0.039 inches). The beveled sidewalls 46 of the chamfered indentation 40 slope toward the first end 52 of the partial linear pre-piercing 150 and act as a guide to direct the tip 4 of the elongated member 2 to the first end 52 of the partial linear pre-piercing 150. The part.ial linear pre-piercing 150 encourages the elongated member 4 to travel a consistent path through the septum 110. The septum 110 is composed of a resilient elastomer material, preferably silicone rubber, which is preferably also resistant to high temperature. When the tip 4 of the elongated member 2 is pressed against the first end 52 of the partial linear pre-piercing 150, the sides of the partial linear pre-piercing 150 first end 52 flex and spread to receive the elongated member 2, as does the length 154 of the partial linear pre-piercing 150 as the elongated member 2 is pushed through the linear pre-piercing 50. The elastomer material of the member 120 then embraces the elongated member 2 to form a seal around the elongated member 2. The tip 4 of the elongated member 2 may be pressed through the length 154 of the partial linear pre-piercing 150 toward and then past the partial linear pre-piercing 150 second end 156 until the tip 4 cuts through the un-pierced portion of member 120 below the partial linear pre-piercing 150 second end 156 until the tip 4 protrudes beyond the bottom surface 126 of member 120. After the sample material is injected into the gas chromatography system through the elongated member 2, the elongated member 2 may be pulled back through the member 120 and partial linear pre-piercing 150, which then seal closed when the elongated member 2 is withdrawn due to the resilient qualities of the elastomer material. The partial linear pre-piercing 150 allows an elongated member 2 to be repetitively inserted through and then withdrawn from the septum 110 with minimal damage to or loss of elastomer material from the septum 110. The beveled sidewalls 46 -of the chamfered indentation 40 guide the tip 4 of the elongated member 2 to the first end 52 of the partial linear pre-piercing 150, greatly increasing the likelihood that the elongated member 2 will travel a consistent path and be inserted through the septum 110 in the same place during each injection.

The member 120 of the septum 110, shown in Figure 6, is formed by introducing the elastomer material, heated into liquid form, through a small gate hole into a mold. The mold is shaped to produce a generally disc shaped member 120 with a chamfered indentation 40 in the center 24 of the top surface 22 of the member 120. The member 120 is generally disc shaped, but may be of any geometric shape and size to fit an injection port of a gas chromatography system. After the elastomer material has cooled, the member 120 is removed from the mold and placed on a jig with the member 120 bottom surface 126 supported by the jig surface. The partial linear pre-piercing 150 is then formed by passing a solid needle through the bottom end 44 of the chamfered indentation 40 toward but not through the bottom surface^' 126 of the member 120. The solid needle used to create the partial linear pre- piercing 150 preferably has a size 23 AWG (0.573 millimeters) body with a beveled tip which tapers to a fine point. The solid needle penetrates the member 120 and creates a split in the elastomer material as it passes through the member 120. No material is removed from the member 120 by the solid needle as it creates the partial linear pre-piercing 150, which allows the sides of the partial linear pre-piercing 150 to seal together when the elongated member 2 is withdrawn from the partial linear pre-piercing 150. Alternatively, the partial linear pre-piercing 150 may also be formed during molding of the septum 110 member 120 by shaping the mold body to have a thin linear projection which creates the partial linear pre-piercing 150 in the finished molded member 120.

The elongated member 2 used for sample injection preferably has a maximum size of 23 AWG (0.573 millimeters) and preferably has a rounded or blunt tip 4 with a maximum size of 26 AWG (0.405 millimeters) to allow the elongated member 2 to be received by the partial linear pre-piercing 150 with a minimum of friction or abrasion.

The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A septum, comprising: a. a member, said member having a top surface, a bottom surface, said top surface having a center; b. a chamfered indentation in said member, said chamfered indentation having a substantially conical shape, said chamfered indentation having a top end, a bottom end and beveled sidewalls, said chamfered indentation located on said member top surface, said chamfered indentation extending from said member top surface partway toward said member bottom surface; and c. a linear pre-piercing in said member, the linear pre-piercing having a first end, a length, and a second end, said first end of said linear pre- piercing located toward said chamfered indentation bottom end, said length of said linear piercing extending at least partially toward said member bottom surface.

2. The septum of Claim 1, where said linear pre-piercing is formed by a penetration of said member without removal of any member material.

3. The septum of Claim 1, where said linear pre-piercing extends completely from a location toward said chamfered indentation bottom end to said member bottom surface.

4. The septum of Claim 1, where said linear pre-piercing extends partially from a location toward said chamfered indentation bottom end toward said member bottom surface.

5. The septum of Claim 1, where said chamfered indentation bottom end is curved.

6. The septum of Claim 1, where said chamfered indentation is located substantially in the center of said member top surface.

7. The septum of Claim 1, where said top end of said chamfered indentation has a top end diameter and said bottom end of said chamfered indentation has a bottom end diameter diameter, said top end diameter being greater than said bottom end diameter.

8. The septum of Claim 1, where said beveled sidewalls of said chamfered indentation slope toward said first end of said linear pre-piercing.

9. The septum of Claim 1, where said member is composed of a resilient elastomer material.

10. The septum of Claim 9 where said resilient elastomer material is silicone rubber.

11. The septum of Claim 9 where said linear pre-piercing receives and seals around an elongated member when said elongated member is extended axially therein, and where said linear pre-piercing seals closed when said elongated member is withdrawn.

12. The septum of Claim 1, where said member is generally disc shaped.

13. The septum of Claim 1, where said member is sized to fit an injection port of a gas chromatography system.

14. The septum of Claim 1, where said septum is formed in a mold.

15. The septum of Claim 14, where said linear pre-piercing is formed during molding of said septum, and where said linear pre-piercing extends completely from a location toward said chamfered indentation bottom end to said member bottom surface.

16. The septum of Claim 14, where said linear pre-piercing is formed during molding of said septum, and where said linear pre-piercing extends partially from a location toward said chamfered indentation bottom end toward said member bottom surface.

17. The septum of Claim 1, where said member having said chamfered indentation is formed in a mold.

18. The septum of Claim 17, where said linear pre-piercing is formed after molding of said member by a penetration of said member, and where said linear pre-piercing extends completely from a location toward said chamfered indentation bottom end to said member bottom surface.

19. The septum of Claim 17, where said linear pre-piercing is formed after molding of said member by a penetration of said member, and where said linear pre-piercing extends partially from a location toward said chamfered indentation bottom end toward said member bottom surface .