AUTOMATIC SAMPLE HANDLING DEVICE

Abstract: A sample handling device for automatically handling a multiplicity of samples, particularly the encapsulated sam­ ples for evaluation using a differential scanning calorimeter, on an individual basis, comprises a vacuum means which is capable of transferring a new sample to be substituted for a tested sample and a means which is capable of removing and re-placing a cover means to allow the transfer of the new sample to be substituted for the tested sample.

Description: Title: Automatic sample handling device and method. The present invention relates to a device and a method for automatically handling a plurality of samples on an individual basis. A differential scanning calorimeter (DSC) is commonly employed as one method for thermally analyzing a material. Using DSC analysis, the difference in energy fed into a test material and a reference material are measured as a function of temperature, while the test material and the reference material are subjected, in an environmental (measuring) cell, to a controlled temperature program. In a conventional evaluation using a DSC, a relatively small, encapsulated sample of the test material is placed in the measuring cell containing a sample of the reference material, and the measuring cell is then covered with a lid having a passageway to allow the escape of gas from the measuring cell. In addition, one or more thermal -sleeves and/or protective hoods are generally placed over the measuring cell. Following the thermal evaluation, which generally takes..about one hour, the insulating sleeve(s) and/or protective hood(s) are removed from the measuring cell and a new, encapsulated sample to be tested exchanged for the previously tested sample of the test material Heretofore, this periodic sample transfer, a time consuming operation, has been conducted manually. Unfortunately, for various reasons (e.g., the required number of operations and the comparatively small size of the encapsulated samples, no one has heretofore effective ly automated the sample transfer procedure of a differential-scanning calorimeter with success. Therefore, it remains highly desirable to provide an effective and economical device for handling a number of samples over an extended period of time. Accordingly, in one -aspect, the present invention provides such a device for automatically handling a multiplicity of samples. Said device comprises (a) a sample holder capable of holding a plurality of -samples, (b) a vacuum means which, during any one cycle of operation is capable of moving one or more of the samples from the sample holder to a receptacle for periodically receiving one or more of the samples, placing the sample in the proper location within the receptacle and removing the tested sample from the receptacle, and (c) a transfer means which, during a cycle of operation, is capable of removing a cover means and any protective hood(s) or insulating sleeve(s) from the receptacle to allow the replacement of the sample therein and of replacing the cover and any protective hood(s) or insulating sleeve(s) after placement of the sample. In the device, the vacuum means and/or sample holder operate in manner such that a new sample is transferred from the sample holder to the receptacle during each cycle of operation. In a preferred embodiment, the transfer means is a vacuum means. In said embodiment, a preferred means for covering the receptacle is designed so that gases can freely pass to or from the receptacle but a vacuum can-effectively be applied to the cover. A preferred cover means for the receptacle comprises a disk or sheet having one or more perforations or passages therein which allow the flow of gas from one surface of the disk or sheet to the opposite surface and a continuous disk or sheet which allows essentially no gas to flow therethrough. The perforated disk or sheet and the continuous disk or sheet are interconnected by a conduit having one or more perforations or passages such that gas passing through the perforated disk or sheet subsequently passes from the conduit through said perforations-orpassages. In another preferred embodiment, the cover means, insulating sleeve and protective hood conventionally employed in combination with the DSC cell are designed so that, after their removal to allow sample transfer, the insulating sleeve can be placed in a receptacle, preferably a tapered receptacle, formed from, or fixed to, the top of the protective hood and the cover means can be placed in a container formed from, or fixed to, the top of the insulating sleeve. In this manner, the removal and replacement of the protective hood, -insulating sleeve and cover means can be effected using a minimum of movable apparatus. The apparatus of this invention is unique in that it provides an effective and economical means for automatically transferring, in a systematic order, the relatively small, encapsulated samples used for DSC analyses or similar evaluation techniques. Moreover, the complexity of the equipment required to provide such automatic sample transfer is surprisingly small. For example, the lifting of the relatively small encapsulated samples as well as the comparatively larger and heavier cover means, insulating sleeve and protective hood for subsequent movement can be accomplished using one vacuum, thereby requiring a single source of vacuum. In addition, the movement, i.e., the removal and replacement, of the small, encapsulated sample and the cover means, insulating sleeve and protective hood can be conducted using air-driven pistons and a single source of compressed air. In another aspect, the present invention resides in a method for automatically handling a multiplicity of samples, said method being a cyclic operation comprising the steps of; 1. a) removing an encapsulated sample of a tested material from a sample receptacle; b) transferring an encapsulated sample of an untested material from a sample holder capable of holding a plurality of samples to the receptacle; and -c) placing the untested sample in the proper location within the receptacle; using a first vacuum means; and 2. a) covering the receptacle with a cover means and any protective hood(s) and/or- insul-ative sleeve(s) after placement of the sample; and b) removing the cover means and any protective hood(s) and/or insu lative sleeve(s) from the receptacle following evaluation of the test material; using a second vavuum means; wherein the first vacuum means and/or sample holder cooperate so that a new sample is transferred from the sample holder to the sample receptacle during each cycle of operation and the cover means is designed so that gases generated during the evaluation of the test material can pass freely from the sample recep tacle through one or more perforations or passages in the cover means but a vacuum applied to the cover is not necessarily exposed to said passages or perforations. The apparatus and method of the present invention are useful for automatically handling experimental samples, thereby allowing continuous and unattended evaluation of a plurality of samples over an extended period. The apparatus and method are particularly useful in conjunction -with conventional DSC type equipment, including both the power-compensation DSC and the heat flux DSC An understanding of this invention will be facilitated by referring to the accompanying drawings, in which Fig. 1 is a schematic representation which illustrates an embodiment of the present invention wherein the apparatus of the present invention is employed in conjunction with a DSC, Fig. 2 is a part-sectional side-elevational view of a preferred sample holder, Fig. 3 is a schematic isometric top view of the sample table illustrated in Fig. 2 further depicting a means for moving the sample holder to ensure a new sample is tested following each cycle, Fig. 4 is a detailed schematic representation, partly in cross-section, of a preferred cover means, insulating sleeve and protective hood for enclosing the measuring cell of the DSC depicted in Fig. 1. Referring now more particularly to the drawings, Fig 1, which represents an embodiment of the present invention, depicts a differential scanning calorimeter cell 92 having a support 1 and a receptacle 2. A first vacuum means 90 for transferring samples of the materials to be tested from a sample holder, such as sample table 10, to the receptacle 2 of measuring cell 92 and for removing tested samples therefrom, comprises a first air cylinder 3, which is supported by a stand 4 and connected to a source of air (not shown) by means of lines 61a and 61b. Cylinder 3 has a slidable piston or rod 5 connected to a movable support 6. Movable support 6 supports a second air cylinder 7. Second air cylinder 7 its connected to the source of air by means of lines 62a and 62b. A vacuum nozzle 9 is connected to cylinder 7 by a slidable piston or rod 8. Vacuum nozzle 9 is connected to a source of vacuum (not shown) by means of line 51. The sample table 10 is rotably mounted on a base 11 by means of a rotating rod or bearing 21. The table 10 and nozzle 9 are positioned so that vacuum nozzle 9 can pick up a sample from table 10 and transport it to the receptacle 2 of the DSC unit. The sample handling apparatus depicted in Fig. 1 further comprises a second vacuum means 91 having a third air-driven cylinder 12 supported by a stand 13 and connected to an air source by means of lines 64a and 64b. Associated with cylinder 12 is a slidable piston or rod 22, which supports a fourth air-driven cylinder 14. Cylinder 14 is connected to an air source by means of lines 63a and 63b. Associated with cylinder 14 is a -slidable piston or rod 15 having a vacuum cup 16 connected thereto. Vacuum cup 16 is connected to the source of vacuum by means of line 54. In the embodiment depicted by Fig. 1, the means for enclosing the receptacle 2 of the DSC cell 92 comprises a cover means 20, an insulating sleeve. 18 and a protective hood 17. Cover means 20 is shown to rest in a container 19 which is permanently fixed to insulating sleeve 18. Insulating sleeve 18 rests,.in turn, on the protective hood 17. During each cycle of operation of the apparatus shown, the tested sample is removed from receptacle 2 by extending the slidable piston 5 associated with first cylinder 3 so that the second cylinder means 7 and the vacuum nozzle .9 are positioned directly over the open receptacle 2 of the DSC cell 92. Slidable piston. 8 is then extended until nozzle 9 contacts the encapsulated sample of the tested material within the-receptacle 2. A vacuum is created in nozzle 9 by means of line 51 which allows the sample to be withdrawn from the receptacle upon the return of piston 8 towards its original position. Piston 5 is thereafter returned to its original unextended position. During its return,, the vacuum in nozzle 9 is interrupted briefly to allow the tested sample to drop harmiesely -therefrom. An encapsulated :sample of an untested material to be exchanged for the just removed sample of tested material .is removed from sample table 10 by extending piston 8 to allow the nozzle 9 to contact the untested sample on table 10. The vacuum existing in nozzle 9 allows the removal of the encapsulated sample from table 10 upon the return of piston 8 to its original position. To place the sample of the untested material in the receptacle 2 of the measuring cell 92, piston 5 its again extended so that second cylinder means 7 and vacuum nozzle 9 are properly positioned directly over the open receptacle 2 of DSC cell 92. At the completion of such extension, nozzle 9, still carrying the untested sample, is lowered into the receptacle by extending piston 8. The vacuum existing in nozzle 9 is then released. Piston 8 is then returned, without the sample, to its original position, leaving the encapsulated sample of the untested material-positioned in its proper location within receptacle 2. Subsequently, piston 5 is also returned to its original, unextended position. Prior to the testing of the newly -positioned sample, the cover means 20, insulating sleeve 18 and protective hood 17 are placed over the receptacle 2 of the DSC cell 92. The cover 20 is replaced by extending piston 15 so that vacuum cup 16 contacts the cover means. A vacuum is generated in vacuum cup 16 by means of line 54 sufficient to lift the cover from the container 19 upon return of piston 15 to its original, unextended position. Cover 15 is subsequently placed over the receptacle 2 by extending piston means 22 such that the cylinder 14 and piston 15 are properly positioned directly over the DSC cell 92. Subsequently, piston means 15 its extended.thereby lowering the cover means -20 in the receptacle 2. The vacuum.in-the vacuum cup is subse quently released. The piston and vacuum cup:l6 are.ret = ed to their original, unextendedposition,.leavingthe covermeans 20 in its proper location in receptacle 2. The piston 22 is then returned to its original, unextended position. The insulating sleeve 18 and protective hood 17 are placed over the receptacle 2 following a similar. procedure -Specifically, the piston 15 is extended - so that the vacuum cup 16 contacts the insulating sleeve 18 or the container- 19 affixed. thereto so that upon the return of the piston -to its original -position, -the insulating sleeve is .carried by the vacuum cup. The piston 22 is then extended to a proper position over the DSC cell. Subsequently, the piston 15 is extended to place the insulating sleeve over the receptacle 2 of the DSC cell 92. The vacuum to the vacuum cup 16 is then released and the pistons 15 and 22 returned to their original, unextended positions. The protective hood 17 is then placed over the DSC cell by picking up the protective hood 17 from its rest position by means of piston 15 and vacuum cup 16. Thereafter, piston 22 is extended to properly position the protective hood 17 over the DSC cell. The piston 15 is then extended and the vacuum of vacuum cup 16 released, leaving the hood 17 covering the DSC cell 92. The pistons 15 and 22 are then returned to their unextended position. The protective hood, insulating sleeve and cover means are easily removed from the DSC cell by performing the above described steps in a reversed order. Although the embodiment illustrated shows the use of vacuum, which is generally preferred in the application of the present invention, the transfer means for transferring the cover means and any insulating sleeve(s) or protective hood(s), may alternatively, and suitably,- comprise a magnet (if the cover, sleeve and/or hood are of a suitable material) or the like for effecting the transfer operations described. During each cycle of the hereinbefore described operation, the sample holder and/or first vacuum means operate so that an encapsulated sample of a new, untested material can be supplied to the receptacle of the DSC cell during the next cycle of operation. Any of a variety of methods can be employed. to ensure that a new sample is transferred from the sample holder to the DSC cell during--each cycle of operation. Of such methods, one preferred method includes rotating the sample table 10 during each cycle so as to position.a.new sample under vacuum nozzle 9 following each cycle of operation. A preferred sample table 10 and carrier support 6 which provide such movements are depicted in Figs 2 and 3. Specifically, Figs. 2 and 3 depict a round sample table useful in the embodiment shown in Fig. 1. The illustrated sample table preferably comprises a multiplicity of equidistantly-spaced-sample receptacles 121 which form a circle having the same centre or essentially the same centre as table 10. The size of table 10 is primarily selected on the maximum number of samples to be tested prior to operator intervention. Typically, the table contains sufficient sample receptacles so that the operation can be effected overnight without the necessity of an operator being present, i.e. the table will conventionally hold a sufficient number of samples to provide a continuous operation of at least 16 hours. As illustrated, a series of permanently affixed catch pins 120 extend in a circle round the centre of sample table 10. In the embodiment illustrated, twice as many catch pins extend from table 10 as there are sample receptacles contained by the table, and each of the pins is spaced equidistantly from the two adjacent catch pins. Fig. 3 shows, in more detail, the sample table and the means for moving the sample table so that an untested sample is made available for placement in the receptacle of the DSC cell during each cycle of operation. Specifically, Fig. 3 depicts the carrier support 6 having a support arm 130 for supporting cylinder 7. At or near the base of carrier support 6, is a spring-loaded, movable trigger 131. In operation, the movable trigger 131 of carrier support 6 interacts with the catch pins 120 extending from table 10 to cause sufficient rotation of sample table '10 to provide a new encapsulated sample during each cycle of operation. Specifically, as a new sample is being transported to receptacle 2, the trigger 131 of carrier support 6 catches one catch pin 120 in a manner such that table 10 rotates half the distance required to place a new sample under vacuum nozzle 9. When the carrier support 6 is returned to its original position, there is no movement in the sample table 10 when trigger 131 contacts a catch pin 120 owing to the partial rotation of trigger 131 around the catch pin. Once contact between pin 120 and trigger 131 is terminated, & gger 131 is returned to its original position by spring 132. When piston 5 is ex-tended to remove the tested sample from the DSC cell, the contact of trigger 131 with catch pin 120 rotates the.sample table 10 sufficiently to place the new sample directly unaer nozzle 9. Again, upon the return of piston 5 to its unextended- position the -spring load of trigger 131 provides no additional -rotation- .of the-tabie upon the contact of catch pin 120 and trigger 131. In the manner described, the sample table is moved so that the vacuum nozzle 9 is now capable of transferring a new sample of an untested material to the differential scanning calorimeter cell during each cycle of operation. This technique merely illustrates one method for ensuring that a new sample is available during each cycle of the sample handling device and should not be construed as limiting the scope of the present invention. With regard to the other components-useful in this invention, Fig. 4 illustrates a preferred cover means, insulating sleeve, and protective hood. The preferred cover means 20 comprises a gas-permeable disk or plate 106, whose permeability permits the passage of gases through plate or disk 106, and a continuous plate or disk 107 which is essentially impermeable to the passage of gas therethrough. Permeable plate 106 and non-permeable plate 107 .are connected or joined by means of a permeable conduit 104 which allows the passage of gas from the interior of the conduit to the environment. In the embodiment shown, gases flowing through the passage(s) or perforation(s) in plate 106 can flow through the passage(s) or perforation(s) in the conduit 104. In this way, during the evaluation of the sample material, any gases generated are free to escape from the receptacle containing the sample, thereby preventing an excessive pressure build-up therein. In addition, a controlled atmosphere can be maintained within the receptacle by purging the cell using a suitable purge gas. Moreover, since top plate 107 is essentially impermeable to the passage of gas, a vacuum can be effectively applied to the top surface thereof and not readily be dissipated. As a result, the cover means is easily moved by the vacuum cup 16 during the removal and replacement operation. Insulating sleeve 18 is shown withba container 19 affixed thereto. Container 19 has space provided;for receiving the cover means 20 after its removal from the measuring cell 92. Similarly, the from tective hood 17 has a receptacle 101 for receiving insulating sleeve i8. The receptacle 101, as depicted in Fig. 4, is advantageously tapered and conforms to the shape of the .insulating sleeve 18. A receiving ring 10pal such .as depicted in the embodiment illustrated in Fig. 4, for receiving hood 17 upon its removal-.from around the 'DSC -cell is also advantageously employed herein. Receiving ring 100 comprises a receptacle 108 which is preferably tapered and conforms to the shape of the protective hood 17. The described receptacles 119, 101 and 100 ensure proper placement of the cover means, insulating sleeve and protective hood upon their sequential removal from the DSC -cell, thereby ensuring continuous and repeatable performance of the sample handling device. The cylinders 3, 7, 12 and 14 are advantageously air-activated, and, where necessary to dampen vibration, supplemented by the presence of oil. Preferably, each cylinder is capable of being activated by a single source of air. In operation, while each movement of the air-driven cylinders and the application or release of vacuum, as required, to the-vacuum nozzle or vacuum.cup can be effected manually, the advantages of the present invention are recognized when the movement of the cylinders and the application of vacuum are controlled by a supervisory control system. Supervisory control systems and techniques for using same are well-known in the art and reference is made thereto for the purposes of this invention. Pneumatic valves operated in combination with microprocessor control have been found to be particularly useful in the operation of the automatic sample handling device as illustrated in Fig. 1. The vacuum nozzle 9 and vacuum cup 16 are designed so that, with the same vacuum, vacuum nozzle 9 is capable of transporting the encapsulated sample without significant damage occurring thereto and vacuum cup 16 is capable of securely transporting the cover means, insulating sleeve and protective hood. The nozzle 9 and vacuum cup í6 illustrated in the Figs. are merely representative of a design that can be suitably employed herein. Vacuum nozzles and/or cups of other design capable of performing the same function -are 'also suitably employed herein.

Claims: CLAIMS 1. An apparatus for automatically handling a plurality of samples on an individual basis, said device comprising (a) a sample holder capable of holding a plurality of samples, (b) a vacuum means which, during any one cycle of operation, is capable of moving one or more of the samples from the sample holder to a receptacle for periodically receiving one or more of the samples, placing the sample in the proper location within the receptacle and removing the tested sample from the receptacle, and (c) a transfer means which, during a cycle of operation, is capable of removing a cover means and any protective hood(s) or insulating sleeve(s) from the receptacle to allow the 'placement of the sample therein and to replace the cover and any protective hood(s3 or insulating sleeve(s-) after placement of the sample, wherein the first means and sample holder operate in manner such that a new sample of untested material is transferred from the sample holder to the receptacle during each cycle of operation.2. The apparatus of claim 1 wherein the transfer means for moving the cover means and any insulating sleeve(s) or protective hood(s) is a vacuum means. 3. The apparatus of claim 2 wherein the means covering the receptacle is designed so that gases can .freely pass to or .from the receptacycle but a vacuum can effectively be applied to the cover means. 4. The apparatus of claim 3 wherein the cover means for the receptacle comprises a disk or sheet having one or more perforations or passages which 'allow the flow of gas from one surface of the disk or sheet to the opposite surface and a continuous disk or sheet which allows essentially:no gas to flow therethrough, the perforated disk or sheet and the continuous disk .or sheet being connected by a conduit having one or more passages or perforations such-that gas passing through the perforated disk .or sheet subsequently passes through the perforations or passages of the conduit. 5. The apparatus of claim 1 wherein the cover means, insulating sleeve and protective hood are designed so that, after their removal to allow sample transfer, the insulating sleeve can be placed in a receptacle formed from, or fixed to, the top of the protective hood and the cover means can be placed in a container formed from, or fixed to, the top of the insulating sleeve. 6. The apparatus of any of claims 1-5 wherein the apparatus is capable of automatically handling a plurality of the encapsulated samples employed in conjuction with DSC analysis. 7. The apparatus of claim 2 wherein the removal and re-placement of the cover means and any insulating sleeve 6r protective hood and the transfer of the encapsulated sample is accomplished using one vacuum. 8. The apparatus of claim 7 wherein the removal of the cover means and any insulating sleeve or protective hood is accomplished by means of air activated cylinders and each cylinder is operated by a single source of air. 9. The apparatus of claim 8 wherein the vibration of one .or more of the cylinders is dampened by oil. 10. A method of automatically handling a plurality of samples, said method being a cyclic operation comprising the steps of; 1. a) removing an encapsulated sample of a tested material from a sample receptacle; b) transferring an encapsulated sample of an untested material from a sample holder capable of holding a plurality of samples to the receptacle; and c) placing the untested sample in the proper location within the receptacle; using a first vacuum means; and 2. a) covering -the receptacle with a cover means and any pro tective hood(s) and/or insulative sleevels) after placement of the sample; and b) removing the cover means and any protective hood(.s) and/or insulative sleeve(s) from the receptacle following .evalua- tion of the test material; using a second vacuum means; wherein -the first vacuum means and sample holder cooperate so that a new sample is transferred from the sample holder to the sample receptacle during each cycle of operation and the cover means is designed so that gases generated during evaluation of the test material can pass freely from the sample receptacle through one or more perforations or passages in the cover means but that a vacuum applied to the cover is not necessarily exposed to said passages or perforations.

Inventors: LAARHOVEN, JOHANNES P. M., TORFS, JAN C. M., VAN HEEL, CHRISTIAAN F. J.
Applicants: DOW CHEMICAL (NEDERLAND) B.V.
Application year: 1984
Main classification: G01N1
IPC codes: G01N35, G01N1