Autosampler syringe with compression sealing

#The present invention relates to liquid chromatography apparatus, and more particularly to a syringe used by an autosampler to acquire samples of liquids.

#In various analytical procedures, including liquid chromatography, a large number of liquid samples are processed sequentially in the same apparatus. An autosampler is used to obtain samples of liquids which are to be analyzed. The autosampler typically uses a syringe to acquire the sample. Performance of autosamplers is significantly influenced by the accuracy of sample acquisition and wear resistance of the syringe. Various configurations of syringes used to obtain liquid samples are known in the art.

#An example of one type of known syringe is generally illustrated in FIG. 1. This prior syringe comprises a cylinder 10, having a first and a second end. The cylinder 10 is typically made of glass. The cylinder 10 has a bore hole 12 through its central portion which extends from the first end to the second end. A piston 14 which enters the bore hole 12 through the first end of the cylinder 10, is configured to slide in and out of the bore hole 12. A plunger 16 is attached to the piston 14 at an end portion thereof and is configured to be inserted for slidable engagement in the bore hole 12. The plunger 16 is typically made of Teflon. The area where the plunger 16 and the bore hole 12 come into contact creates a liquid tight seal. As the piston 14 is pulled out of the bore hole 12, the plunger 16 creates a vacuum which draws a sample into the bore hole. This necessitates that the bore hole 12 and the plunger 16 be fabricated within strict tolerances to achieve desired accuracy of sample.

#The foregoing and other features and advantages of the present invention will be more fully understood from the following detailed description of illustrative embodiments, taken in conjunction with the accompanying drawing in which:

#FIG. 1 is an illustration of a prior art autosampler syringe;

#FIG. 2 is an illustration of an autosampler syringe according to present invention;

#An autosampler syringe of the present invention is generally illustrated in FIG. 2. In this illustrative embodiment, a syringe is shown comprising a cylinder 30, having unitary, integral first end 31 and second end 33, and a displacement rod 32. The cylinder 30 has a bore hole 34 through its central portion which extends from the first end 31 to the second end 33. In the present invention no critical bore tolerance is required, as bore sealing is not a function of the internal bore diameter, thus significantly lowering cost of manufacturing the presently disclosed syringe. A constant area seal 36 is located at the first end 31 of the cylinder 30. In this illustrative embodiment, the constant area seal 36 and the cylinder 30 are manufactured as a unitary structure further reducing manufacturing costs. The displacement rod 32 is slidably inserted in the bore hole 34 through a hole in the constant area seal 36. The outside diameter of the displacement rod is dimensioned to tightly yet slidably contact the constant area seal 36 to form a substantially liquid tight seal. Accordingly, there is no wear between the displacement rod 32 and the inner walls of the bore hole 34 because they do not come into contact with each other. The cylinder in this illustrative embodiment is unitarily produced using Ultra High Molecular Weight Plastic.

#A fitting portion 38 of the displacement rod 32 remains outside of the cylinder 30 and has a fitting either mechanically fastened to or unitarily integrated with the displacement rod 32. The fitting 38 is configured to be connected to a mechanical actuator as a function of the instrument in which the autosampler syringe is to be installed. The mechanical actuator, as known in the art, moves the displacement rod 32 in or out of the bore hole 34 to acquire or expel a sample. The displacement rod 32 has a crosshole 40 at a point where it can either be positioned inside the bore hole 34 or outside of the constant area seal 36. When the cross hole 40 is positioned outside the constant area seal 36 it has no effect on the drawing in or discharge of a sample. When the cross hole 40 is positioned inside the bore hole 34, it allows undesired fluid trapped inside the bore hole 34 to be vented. Undesired fluid is vented to outside the bore hole 34 through a pathway inside the displacement rod 32 to the end of the displacement rod 32 and through a vent hole 42. The fitting portion 38 has a ridged end 44 or other means of connection so that a flexible hose or other conduit can be attached for the purpose of diverting undesired fluid to a waste containment area (not shown).

#The second end 33 of the cylinder 30 is formed into a threaded protrusion 46 for attachment to known mechanisms for receiving the acquired sample (not shown). The threaded protrusion 46 in this illustrative embodiment also acts as a static seal between the cylinder 30 and the receiving mechanisms. The static seal will not lose its integrity upon undergoing heating and cooling as does the Teflon seal used by many prior art fluid transfer devices as it is unitary and integral to the cylinder and does not involve engagement of materials having significantly dissimilar coefficients of thermal expansion.