US2970513A - Apparatus for analysis of materials - Google Patents

Description

Feb. 7, 1961 J. L. WATERS APPARATUS FOR ANALYSIS oF MATERIALS 2 Sheets-Sheet l Filed March 25, 1957 Feb. 7, 1961 J. L. WATERS 2,970,513

APPARATUS FOR ANALYSIS OF MATERIALS Filed March 25, 1957 2 Sheets-Sheet 2 PQE-554 57 ATTORNEY APPARATUS FOR ANALYSIS OF MATERIALS James L. Waters, Framingham, Mass., assigner to Mine Safety Appliances Company, Pittsburgh, Pa., a cor poration of Pennsylvania Filed Mar. 25, 1957, Ser. No. 648,045

6 Claims. (Cl. 88-14) This invention relates to an apparatus for use in the analysis of materials, and more particularly to an improved construction of such apparatus and its component parts.

Apparatus of the type relating to this invention, such as multibeam optical infrared analyzers are operative for their intended purpose when constructed in a manner to provide a stable transmission of light paths traversing the analyzer. Such stability is dependent upon the rigidity and thermal characteristics of the construction of the analyzer. These specific construction features cannot be provided without giving careful consideration to fabrication procedures and costs, material costs, and weight and space requirements.

Present construction practices involve the assembly of many components easily susceptible to instability of light transmission resulting from the inability to withstand vibrations present within and around the analyzer, and the inability to prevent creep or slow relative motion between components due to thermal changes or stress relief. Where some measure of success has been obtained in providing desired rigidity for many components, disadv-antageous thermal inefliciency, increased number of supporting and fastening components, increased fabrication problems, increased weight and bulkiness, and increased fabrication and material costs have resulted to prevent solving the analyzer stability problem. Consequently, present day analyzer constructions have not proven satisfactory even for limited periods of analyzer operation.

Accordingly, it is among the objects of this invention to provide a multi-beam optical apparatus having components of a construction which'have the capacity to withstand effects of vibrations and thermal changes to which apparatus of this type may reasonably be subjected. A further object is to provide a device having few components that are readily fabricated and assembled, and which is light in weight, small in size, and comparatively inexpensive to produce. Another object is to provide a device which retains its operational eiciency and accuracy for a long period of use. Another object is to provide a multi-beam optical apparatus having stable light transmitting paths.

Other objects and advantages will become apparent from the following description and annexed drawings in which:

Fig. 1 is a top plan view, partly in section, of an infrared gas analyzer;

Fig. 2 is a side elevation, partly in section, of the device shown in Fig. 1;

Fig. 3 is a horizontal sectional view of another form of cell block unit shown in Figs. 1 and 2;

Fig. 4 is a horizontal sectional view of still another form of cell block unit; and

Fig. 5 is a horizontal sectional view of a. combined cell block and detector block unit.

It is particularly pointed out that the instant invention is'limited to a combined cell block and detector block unit (or analysis unit) per se illustrated in Fig. 5 only.

and the combination of this unit with the source unit described hereinbelow with reference to Figs. 1 and 2.

The invention illustrated in Figs. 1-4 is the joint invention of James L. Waters and Arthur W. Snkinson and claimed in a separate co-pending application Serial No. 648,044 led March 25, 1957, and described here,-

inbelow to set forth more clearly a disclosure of the in,- stant invention.

This invention is applicable to, and is herein illustrated as embodied in, gas analysis apparatus wherein infrared radiation is caused to travel along two paths and is caused to traverse the cell containing the gas to be analyzed in one of said paths, and wherein the gas in said analysis cell affects the relative intensity of the beams. The gas is ordinarily continuously passed through said analysis cell. An advantageous mode of analysis of this type is described in co-pending appicaton Serial No. 403,525 filed January l2, 1954, and entitled Gas Analysis Apparams. This application has matured as Patent No. 2,802,109 issued August 6, 1957.

Referring to Figs. l and 2, the apparatus is shown Vas comprising three single block units S, C and D, each of which is generally rectangular and made of, for example, aluminum which has high heat conductivity and can be maintained at a uniform elevated temperature. Source unit S provides a housing or block comprising passages 1 and 2 having arranged therein infrared sources 3 and4, the beams from which, may be interrupted or alternated by the interrupter member 5 rotatably actuated by motor 6 through motor shaft 7. Cell unit C is connected to unit S in abutting relationship by suitable mechanical fastening means, such a`s bolts 8 in a manner whereby the end surfaces of units S and C are in thermal contact with each other. Unit C is apertured to receive an electrical heating unit 10 providing means for elevating the apparatus to a uniform elevated temperature. Unit C provides a housing or block forming an analysis or sample gas chamber or pas'- sage 11 and a comparison gas chamber or passage 11a aligned with passages 1 and 2 of unit S. Chamber 11 extends throughout the length of unit C and is sealed at one end by a window 13 of infrared transmitting material,I such as calcium fluoride. Recess or passage 12 is provided in the end of unit C for containing window 13 and a lead washer 14. Washer 14 is inserted between the end of chamber 11 and window 13 to safeguard the latter from expansion and contraction of metallic components due to thermal variations. Window 13 is slightly spaced from the end of unit C and the Wall of recess 12 for this same purpose. Preferably, washer 14 is connected to the end of chamber 11 by cement, and window 13 is connected to Washer 14, similarly, by cement. The peripheral space between the wall of recess 12 and win dow 13 and Washer 14 conveniently forms a trap for excess cement. Wall 15 of chamber 11 is highly polished to limit absorption of infrared radiation through the walls of unit C. A convenient means for passing analysis gas through chamber 11 is provided, such as through conduits 16 and 17. Recess 12a, window 13a, lead washer 14a, wall 15a, and conduits 16a and 17a are identical in construction and function as the counterpart components just described. Conduits 16a and 17a, however, are preferably sealed after reference gas charnber 11a is lled.

Detector unit D is secured to unit C in abutting relationship for thermal contact therewith by fastening means, such as bolts 20, and provides a housing or block forming gas chambers or passages 21 and 21a. These chambers 21 and 21a are aligned with chambers 11 and 11a,

and are connected together, at the rear thereof, by conduit means 26 leading into a chamber 27 closed'by a flexible membrane or diaphragm 28. Chambers 21 and 'easily attached in immovable true alignment.

21a are sealed at the ends aligned with chambers 11 and 11a by a window construction substantially identicial to that described for chambers 11 and 11a. Recesses or passages 22 and 22a, however-are enlarged to accommodate O rings 25 and 25a to provide a gas seal between units C and D to prevent gas from escaping from chambers l1 and 11a. Thus, with vthe exception of the enlargement of recesses 22 and 22a, just mentioned,

Windows 23 and 23a, lead washers 24 and 24a are con- `structed and arranged to seal chambers 2li and 21a in the same manner as described above for chambers il and 11a. Chambers 21 and Zla contain a detector gas to which diaphragm 28 is responsive. Condenser microphone 29 receives signals emanating from the vibrations of diaphragm 28, and such signals may be amplified and further recorded, if desired. Chambers 2l, 21a, and 27 may be `filled with detector gas through conduit 36, Vwhich in turn, is subsequently sealed.

For the operation of the known infrared analyzer, such yas here described and illustrated, reference may be had to Patent No. 2,648,775, and/or co-pending application Serial No. 403,525 mentioned above. Briefly stated, the analyzer of this invention passes beams from infrared sources 3 and 4, alternately, through analysis or sample ,gas chamber 11 and comparison or reference gas chamber 11a into chambers 2l, 21a and 27 containing a detector gas. The absorption of infrared radiation by the analysis gas is reflected in the detector gas chambers to vibrate diaphragm 28 and produce a signal which is picked up by microphone 29. Thus, the composition of the -gas being analyzed can be determined.

The primary advantages of the analyzer construction hereinabove described should now be obvious. Since the analyzer comprises only three units with few connectors, stability of light transmission can be easily provided throughout the length of the analyzer regardess of how great vibrations may be within and around the analyzer. Further, since only a few components are employed and these are readily connected in excellent thermal contact with each other, it is possible to maintain equal temperature conditions throughout the entire analyzento prevent unequal absorption of infrared radiation through the walls of the device. This unequal absorption, of course, would result in unequal radiation through the analysis and reference gas chambers. Moreover, the unitized construction permits using only a single Ywindow between aligned passages which results in in- '-creased'and equal light transmission through the charnbers. and results in decreased costs. Also. simple fastening means securing each of the units together can be employed to provide a rigid structure whose components are Making the cell unit as a singe housing or block further provides equal stability for the analysis and reference gas chambers.

Reference is now made to Fig. 3 wherein is shown another form of cell unit C1 which may be substituted for unit C shown in Figs. l and 2. The only material difference between units C and C1 is that the latter' comprises tubular, stainless steel, liners 35 and 35a forming an analysis or a sample gas chamber 31 and a comparison or reference gas chamber 31a, respectively. The inner walls of liners 35 and 35a are gold coated and highly polished to increase the reectivity of the liners to thereby decrease the absorption of the infraredradiation passing through the liners. The remaining structure of unit C1, that is, heater 20a, recesses or passages 32 and 32a, windows 33 and 33a, lead washers 34 and 34a and conduits 36 and 36a, is identical in construction and function to the counterpart structure shown in Figs. 1 and 2. Thus, unit C1 is fu'ly interchangeable with unit C, and is connected to units S and D in precisely the same manner as is shown in Figs. l and 2 for unit C. As mentioned, the advantage of such substitution is to utilize a cell block unit having a minimum amount of infrared radiation absorption through the walls of the unit to provide a more equal and accurate light path.

Referring to Fig. 4, a still kfurther form of the cell unit is shown and designated as C2. Cell unit C2 is likewise interchangeable with either units C or C1, and is assembled with units S and D as described above. Unit C2 provides a housing or block forming an analysis gas chamber" or passage 41 and a reference gas chamber or passage 41a extending from recess or passage 42a. These chambers are formed by tubular, stainless steel, gold coated, liners 45 and 45alidentical to liners 35 and 35a of Fig. 3, with the exception, that liner 45 is shorter in length than liner 35. Unit C2 comprises a recess or passage 42 for the reception of an aluminum, tubular, insert 47 containing a tubular, stainless steel, gold coated, liner 49 extending therethrough forming a gas lilter chamber 40. v Insert 47 is recessed at 48, and chamber 40 is sealed at both ends by a window and washer assembly comprising windows 43, 43 and lead washers 44, 44. Windows 43, 43 and 43a and lead washers 44, 44 and 44a are constructed identically to the counterpart construction fully described above. Chamber 40 is adapted to contain a gas which will function as a filter for tilterf ing out desired bands of light in the infrared spectrum. Conduits 46 and 4&1, and heater 10b have been provided for the purpose hereinbefore described. For those applications of the analyzer where it is desirable that the infrared radiation be filtered ahead of the analysis gas, cell unit C2 can be substituted for either units C orA C1. In addition, all the advantages of using high reflective liners are obtained. Some conventional means, not shown, of filling chamber 40 with lter gas is provided; such as, conveying the gas through an aperture in liner 49 through the wall of unit C2 after the ends of liner 49 have been sealed by the window and washer assembly, and then, sealing the aperture. Alternatively, conduit pipe means might be employed for this purpose.

It should be readily understood, when referring to Figs. 1 4, that recesses 22, 22a, window assemblies 23, 24, 23a, 24a and O rings 25, 25a (Fig. l), could be bodily reversed and disposed within the ends of cell units C, C1 and C2 for sealing the open ends of the analysis and reference gas chambers of each cell unit. Such modification requires only that the chambers be spaced from the ends of the units in the same manner as is shown for the opposite sealed ends of the cell units. Moreover, only one chamber in the cell unit may be so sealed by such reversal of parts while retaining the illustrated construction for the other chamber.

Referring now to Fig. 5, a combination cell unit and detector unit, hereinafter referred to as an analysis unit, is shown and designated as CD. This analysis unit vCD is employed when analysis of a simple gas is desired. Unit CD is substituted for units C and D of Figs. l and 2, and is connected directly to source unit S by bolts 8. Unit CD provides a housing or block forming detector gas chambers or passages 6l and 6ta communicating with each other at the rear by conduit means 66 leading into a gas chamber 67 closed by a flexible membrane or diaphragm 68. Condenser microphone 69 receives the signals caused by the vibrations of diaphragm 68; such signals being amplified and recorded, if desired. These components are similar to those shown in unit D of Figs. l and 2. Chamber 61 is sealed by tubular insert 57 forming an analysis gas chamber 51, and chamber 61a is sealed by lead washer 64a and window 63a contained in recess or passage 62a. Insert 57 is similar to insert 47 of Fig. 4, but does not include a liner and comprises, in addition, a conduit 56 for passing analysis gas through chamber 51. Recess or passage 52, windows 53, 53, lead washers S4, 54 and recess 58 are identical to the counterpart components shown in Fig. 4. Also, recess 62a, window 63a, lead washer 64a and heater ltlcare ofthe same construction and function as the counterpart components disclosed in Figs. l4. ln Fig. 5, chamber 61a functions as a comparison or reference gas chamber in addition to its function as a detector gas chamber. That is, the analysis gas is compared with the detector gas for detecting gas constituents. These chambers may be filled with a detector gas through conduit 70, for example, after chambers 61 and 61a are sealed; after which, conduit 70 is sealed.

Having explained the principle of the present invention and having illustrated and described what is considered to be the best embodiment, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A multi-beam optical analyzer for the analysis of materials comprising a light source unit having passage means for directing light beams, a single metal block analysis unit having two chambers extending therethrough and optically aligned with said passage means, one of said chambers adapted to contain an analysis material and the other of said chambers adapted to contain a reference material, said unit having a third chamber cornmunicating with the reference chamber and optically aligned with the analysis chamber, light transmitting means sealing the end of the reference chamber adjacent said source unit and both ends of the analysis chamber, and detector means contained within said analysis unit in iiuid communication with said reference and third charnbers for detecting the light absorbed therein.

2. A multi-beam optical analyzer for the analysis of materials comprising a single housing light source unit having passage means 'for directing light beams, a single metal block analysis unit, said units having parallel end surfaces rigidly connecting in abutting relationship with each other, first and second recesses formed in the end of said analysis unit that abuts said source unit, a first chamber adapted to contain a reference material and extending from said iirst recess, a second chamber extending from said second recess and communicating with said reference chamber, a tubular insert forming a cha.; ber adapted to contain an analysis material and disposed in said second recess, first light transmitting means disposed in said first recess and sealing the end of said reference chamber, second light transmitting means sealing both ends of said analysis chamber, said chambers being optically aligned with said passage means, and detector means contained within said analysis unit in uid communication with said first and second chambers for detecting the light absorbed therein.

3. For use in a multi-beam analyzer for the analysis of materials, the improvement comprising a single metal block unit having rst and second cylindrical chambers extending from one end thereof, a third cylindrical chamber in said unit extending in optical alignment with said second chamber, said first and third chambers communito contain a reference material, said second chamber adapted to contain an analysis material, light transmitting means sealing the end of said first chamber adjacent the said one end of the unit and sealing both ends of said second chamber, and said block having a detector means in Huid communication with said first and third charnbers and seaiing the rear ends of said rst and third chambers.

4. For use in a multi-beam analyzer for the analysis of materials comprising a single metal block analysis unit having a lirst chamber extending from one end thereof, irst light transmitting means sealing said iirst chamber at said one end, said unit forming a passage extending from said one end, a tubular insert forming a second chamber disposed in said passage, second light transmitting means sealing both ends of said secondV chamber, a third chamber extending from said second chamber and in optical alignment therewith, said first and third chambers communicating with each other at the rear ends thereof and adapted to contain a reference material, said second chamber adapted to contain an analysis material, and said biock having a detector means in uid communication with said rst and third chambers and sealing the rear ends of said first and third chambers.

5. For use in a multi-beam analyzer for the analysis of materials comprising a single metal block analysis unit having first and second recesses extending from one end thereof, a lirst chamber extending from said ilrst recess, light transmitting means disposed in said first recess and sealing the end of said iirst chamber, a tubular insert forming a second chamber and disposed in said second recess, light transmitting means sealing both ends of said second chamber, a third chamber extending from said second chamber and in optical alignment therewith, said first and third chambers communicating with each other at the rear ends thereof and adapted to contain a reference material, said second chamber adapted to contain an analysis material, and said block having a detector means in fluid communication with said first and third chambers and sealing the rear ends of said first and third chambers.

6. The unit of claim 5 and, said iirst and second light transmitting means each comprising window means spaced from the walls of said iirst and second recesses, each of said window means including windows and expansion members, and said members being disposed between said windows and said first and second chambers.

References Cited in the le of this patent UNITED STATES PATENTS

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