An article appeared on page 510, Volume 11, of the Philosophical Magazine in 1881 in which Alexander Graham Bell reported upon certain experiments which he conducted to study the sound-emitting properties of materials when exposed to the action of rapidly interrupted sunlight. Bell, among other things, introduced samples of material into a chamber and passed an intermittent beam of sunlight therein to produce audible effects. Bell observed that when the sample was in an acoustical resonant chamber the maximum response was achieved at a frequency of interruption equivalent to the resonant frequency of the chamber. While Bell was primarily interested in producing sound, he did recognize that this effect could be employed to study the properties of the material.
In the U.S. Pat. No. 3,948,345 which issued on Apr. 6, 1976, there is disclosed methods and means for analyzing solid and quasi-solid substances. This is accomplished by detecting signals which are established between a substance being tested and a surrounding fluid by a source of radiant energy whose amplitude is varied and whose frequency is scanned. An acoustic responsive transducer is located to sense the changes in the energy level of the surrounding fluid and transduces these acoustical energy changes into electrical signals that are characteristic of the substance being analyzed.
In the aforesaid U.S. patent there is disclosed in FIGS. 9-21 thereof the types of response graphs or curves obtained for a plurality of solid substances when analyzed by said patented system and method. Further reference to said patent is directed to obtain a more thorough understanding of said photoacoustic system for analyzing solid and quasi-solid substances.
Reference is also directed to the copending application, Ser. No. 567,640, filed Apr. 14, 1975 which is a continuation-in-part of U.S. Pat. No. 3,948,345, and which application discloses several embodiments of photoacoustic cells especially designed for use in said photoacoustic system of said U.S. Pat. No. 3,948,345.
The photoacoustic cell of this application is especially designed for use with the system and method of analysis of solid and quasi-solid materials as described in said aforesaid U.S. Pat. No. 3,948,345 and enables series of tests to be easily repetitively performed, said cell being relatively simple in structure and operation as compared to other sample test cells heretofore known.
Therefore, an object of this invention is to provide a new and improved photoacoustic cell.
Another object of this invention is to provide a new and improved photoacoustic cell which is readily adaptable to perform repetitive tests on solid and quasi-solid substances.
Another object of this invention is to provide a new and improved photoacoustic cell which is applicable for a wide variety of uses.
Other objects and advantages of the photoacoustic cell of this invention will become apparent to one skilled in the art upon reference to the following disclosure of a preferred embodiment.