US 3783694 A
A punch assembly for releasing individual samples contained in metallic capsules into an analytical instrument includes a punch for piercing the capsule. The punch has a generally cylindrical piercing front end having a chamfered front surface formed by a plane cutting the front surface at an oblique angle and a central longitudinal channel extending from the front surface through the length of the punch. The cylindrical front end has a diameter which is only moderately smaller than the interior diameter of the capsule, so that the punch acts at least in part as a piston to push the sample material into the longitudinal channel which is connected to the analytical instrument. A relatively rapid flow of transfer gas is caused to flow around the surface of the punch into the capsule to both avoid sample loss and to carry the rest of the sample into the longitudinal channel. The punch assembly thus tends to inject all of the sample into the analytical instrument (e.g., a gas chromatograph) rapidly as a discrete relatively compact "packet" or "slug" of sample material.
Claims available in
Description (OCR text may contain errors)
[ll]  Jan. 1974 PUNCH FOR PIERCING SAMPLE CAPSULES Inventors: Eginhart Otte; Dietrich Jentzsch,
both of Uberlingen/Bodensee, Germany Bodenseewerk Perkin-Elmer & (10., GmbH,, Uberlingen/Bodensee, Germany Filed: Mar. 3, 1972 Appl. No.: 231,618
 Foreign Application Priority Data Mar. 18, 1971 Germany P 21 12 991.9
US. Cl 73/422 GC Int. Cl. G011n 1/22 Field of Search 73/422 GC; 23/259  References Cited UNITED STATES PATENTS 6/1972 Frank et al 73/422 GC 3,635,093 5/1969 Downs et a1. 73/422 GC 3,730,002 5/1973 Penton 73/422 GC Primary Examiner-Donald O. Woodie] Assistant ExaminerDaniel M. Yasich [5 7] ABSTRACT A punch assembly for releasing individual samples contained in metallic capsules into an analytical instrument includes a punch for piercing the capsule. The punch has a generally cylindrical piercing front end having a charnfered front surface formed by a plane cutting the front surface at an oblique angle and a central longitudinal channel extending from the front surface through the length of the punch. The cylindrical front end has a diameter which is only moderately smaller than the interior diameter of the capsule, so that the punch acts at least in part as a piston to push the sample material into the longitudinal channel which is connected to the analytical instrument. A relatively rapid flow of transfer gas is caused to flow around the surface of the punch into the capsule to both avoid sample loss and to carry the rest of the sample into the longitudinal channel. The punch assembly thus tends to inject all of the sample into the analytical instrument (e.g., a gas chromatograph) rapidly as a discrete relatively compact packet or slug of sample material.
5 Claims, 3 Drawing Figures PUNCH FOR PIERCING SAMPLE CAPSULES This invention relates to a punch for piercing sample capsules made of metal as used in sample injectors of injecting discrete separate samples into analytical instruments, said punch being cut at its end by a plane cut obliquely to its longitudinal axis and having a central transfer gas channel terminating in the end defined by this cut.
In published German patent application No. 1,598,176, corresponding to United States patent application Ser. No. 719,037, filed on Apr. 5, 1968 in the name of Peter Frank, Dietrich Jentzsch and Helmut Kruger and assigned to the assignee of the instant application, said United States patent application having been abandoned in favor of continuation, application Ser. No. 18,378, filed Mar. 13, 1970 copending therewith, issued as US. Pat. No. 3,672,227 on June 27, 1922, a method of and apparatus for injecting individual liquid or solid samples into analytical instruments is disclosed. In particular, the sample is initially sealed in a metallic vessel by a mechanical deformation; this metallic vessel is then introduced into the gas flow system in the heated inlet section, is pierced there, rinsed by transfer gas, and the empty sample vessel is then removed fromthe flow system prior to the beginning of the next following analysis. For this purpose, the metallic vessel (sample capsule) is mounted in a cavity of a plunger and pressed onto a stationary punch (or mandrel) which pierces the sample capsule.
In a sample injector or punch assembly of the type indicated, a punch has been proposed which has a conical or frusto-conical end the tip of whichmay be cut by an angled plane so as to be chamfered. A central gas transfer channel may connect with the punch tip (FIG. 7). The punch is mounted on a base element of basically cylindrical shape in the front face of which a plurality of axially (longitudinally) extending exit channels surround the punch. Transfer gas is supplied (in the FIG. 7 form) through the central channel in the punch to rinse (i.e., carry in its flow) the sample substance inside the sample capsule (after piercing of the sample capsule) through axial grooves on the side'faces of the punch (see German printed patent application No. l,934,487,published Jan. 21, 1971) and the axial exit channels to the analytical instrument, in particular to a gas-chromatographic separating column.
It is an object of this invention to provide a punch of the type indicated in the beginning, which permits a rapid injection of the sample into the analytical instrument as a sharp packet or slug.
According to the invention this object is attained by providing that the punch has a thickened end of chamfered basically cylindrical shape and the central transfer gas channel leads directly to the analytical instrument.
Therefore, in such a new punch assembly, the transfer gas is not supplied centrally through the punch into the capsule and discharged from the capsule around the punch, thereby entraining the capsule contents (i.e., the sample) as in the prior device. Rather, the central transfer gas channel leads directly to the analytical instrument, (for instance, a gas-chromatographic separating column); and as the thickened cylindrical end of the punch pierces the capsule, the punch initially acts like a piston so that the sample substance can only expand (and in fact is partially pushed) into the transfer gas channel. Upon further advance of the capsule (which may be mounted in a cartridge provided with a respective cavity) relative to the punch, the transfer gas flows into the capsule from around the punch and rinses the sample substance through the transfer gas channel.
Advantageously, the cross-section of the central gas channel is great with respect to the cross-section of the annular channel defined between the outer circumference of the punch end and the capsule walls. This ensures that the vaporous or evaporating sample substance expands only into the central transfer gas channel, while a comparatively high pneumatic resistance against sample flow outwardly through the annular channel is obtained. The transfer or carrier gas entering the capsule through the annular channel advantageously has a high linear velocity.
The thickened end of the punch may be followed by a tubular throat having an outer diameter slightly less than that of the end.
A more specific further provision of this invention is that the throat may be followed by a cylindrical base portion including at its remote end an axial collar surrounding the central transfer gas channel, said collar protruding sealingly into the end of a transfer gas tube. The punch may consist of oxidized zirconium and the transfer gas tube may consist of glass. The punch may be mounted together with the transfer gas tube in a cylindrical chromium steel jacket.
A single exemplary embodiment of this invention will now be described more fully with reference to the accompanying drawings, in which:
FIG. 1 illustrates in longitudinal section on an enlarged scale a punch of the invention as it pierces a sample capsule;
FIG. 2 is a longitudinal section of the entire assembly for supporting the punch and introducing the sample and carrier gasto the analytical instrument; and
FIG. 3 illustrates in section on an enlarged scale a sample capsule used in connection with the punch of the invention prior to its sealing.
As best seen in FIG. 1, the punch of the invention has a thickened end 16 of generally cylindrical shape, which has been cut by a plane 12 obliquely to its longitudinal axis. A tubular throat 14 of reduced diameter is between the punch end 16 and the larger diameter cylindrical base 16. At the other or rear end the base 16 has an axial collar 18. Parts 11), M, 16 and 18 are preferably integral. A gas transfer channel 2111 surrounded by the collar 18 at the left and terminating at the right in the chamfer 112 extends centrally through the thickened end 16, the tubular throat 141, the base 16 and the collar 18. The collar 18 protrudes sealingly into the end of a transfer gas tube 22 leading to the analytical instrument. The punch base 16 is mounted in a cylindrical jacket 24, so that the base 16 enters into an axial bore 26 of the jacket 24 with its rear (i.e., left) surface resting on a shoulder 28 in bore 26. The gas tube 22 is disposed in the reduced diameter extension 30 of bore 26.
A sample capsule 32 is mounted in an appropriate cavity 341 in a cartridge-like plunger 36, which is separate from and slidable (in the horizontal direction in FIG. 1) relative to the other elements (16-30).
The sample capsule is a metallic vessel 32, which originally was of the form as is illustrated in FIG. 3. A measured volume of a sample substance is introduced into this vessel. Thereafter, the vessel is compressed mechanically at the upper end in FIG. 3 and is sealed as by cold welding. This sealed end is the end 38 of the capsule 32 shown in FIG. 1. When the plunger 36 is moved forwardly in FIG. 1 (from the right towards the left), the punch pierces the advancing capsule 32. Transfer gas (e.g., the carrier gas in a gas chromatograph) is supplied in the direction of the arrows 40.
During the early part of the piercing action, the capsule is substantially held sealed by the cylindrical thickened portion of the punch, so that the sample substance in the capsule 32 is substantially forced to expand (i.e., is pushed by the piston-like action of the punch) into the central transfer gas channel 20. Upon further advance of the plunger 36 carrying the capsule 32, a narrow annular channel 42 is formed around the throat 14 relative to the opening in the capsule and between the thickened end 10 (as well as throat 14) and the capsule walls, through which transfer gas enters the capsule 32 and rinses (i.e., pushes by its flow) the residual sample substance into and through the transfer gas channel 20. The cross-section of the annular channel 42 (in particular its width as measured in the radial direction) between the punch end 10 and the capsule walls is less than the cross-section (diameter) of the transfer gas channel 20. Thereby, a high gas flow rate in the annular channel 42 is provided on the one hand, while ensuring on the other hand that the expanding sample substance in the capsule 32 cannot escape out of the capsule through the annular channel 42.
The punch itself (that is, the parts 10, 14, 16 and 18) is preferably made of oxidized zirconium. The transfer gas tube may consist of glass, while the jacket 24 is preferably made of chromium steel.
FIG. 2 is a scale illustration of the entire assembly which is rigidly attached to the punch of the invention. The end of jacket 24 remote from the punch is held by means of part 44 in a fixed portion of the instrument with which the assembly is used. In the exemplary embodiment illustrated, with which favorable results were obtained, the outer diameter of the thickened end 10 of the punch is 1.8 mm. The central transfer gas channel has a diameter of 0.5 mm. The diameter of the base 16 is 3 mm., while the diameter of the tubular throat 14 is 1.5 mm. The sample capsule 32 according to FIG. 3 used with the punch according to FIG. 2, has an outer diameter of 3 mm. and a wall thickness of 0.2 mm.
The punch assembly of the invention permits a rapid transfer of the vaporous substance under analysis to, for example, the separating column as a single discrete packet or slug" of sample substance. Moreover, it permits glass tubing to be used for conveying the sample substance from the punch to the analytical instrument. As compared with the constructions described in the beginning of the specification, manufacture of the new punch is simplified.
What is claimed is:
1. A punch assembly for piercing metallic samplecontaining capsules and to inject the sample into an analytical instrument, comprising:
a punch having a chambered cylindrical piercing end,
formed by a plane obliquely cutting the front surface of the basically cylindrical piercing end, said piercing end having an outer portion with a diameter slightly smaller than the interior diameter of a cylindrical sample capsule;
a tubular throat portion directly behind said cylindrical piercing end, said throat portion having an outer diameter which is slightly less than the outer diameter of said cylindrical end;
and a longitudinal central channel extending from said front surface through the entire length of said punch,
whereby as said punch piercingly enters a sample capsule, said cylindrical end acts, at least in part, as a piston for forcing at least part of the sample material into the longitudinal channel toward the sample-receiving inlet of the analytical instrument, and after the punch has substantially entered the sample capsule, a transfer gas will readily enter between the pierced end of the capsule and the throat portion to assist in sweeping the sample material into the longitudinal channel into the analytical instrument, so that the sample tends to be injected as a compact packet into the analytical instrument.
2. A punch assembly according to claim 1, in which:
the diameter of said longitudinal central channel is greater than the radial width of the annular channel defined between the outer surface of said cylindrical piercing end of said punch and the inner walls of the sample capsule pierced thereby,
whereby escape of the sample around the punch through the annular channel is inhibited.
3. A punch assembly according to claim 2, in which:
said punch further comprises a relatively large diameter cylindrical base portion connected to the rear of said throat portion, and a relatively small diameter axially extending collar portion connected to the rear of said cylindrical base;
said longitudinal central channel extending continuously through said cylindrical piercing end, said throat portion, said cylindrical base portion and said collar portion;
said assembly also comprising a gas tube sealingly connected to the collar portion of said punch to receive the sample from said longitudinal channel and convey it to the analytical instrument.
4. A punch assembly according to claim 3, in which:
said entire punch, including said cylindrical piercing end, said throat portion, said cylindrical base portion and said collar portion, consists of oxidized zirconium;
and said gas tube consists of glass.
5. A punch assembly according to claim 4, in which:
said assembly further comprises a cylindrical chromium steel jacket surrounding and supporting said gas tube and at least said cylindrical base portion of said punch.