The Chemist and the Patent WILLIAM S. HILL Member, Examining Corps, 8~United States Patent Ofice I
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OST students show a complete unfamiliarity with patents, and even most industrial chemists show a reluctance to study them. The average student confronted with a typical chemical patent will probably, a t first, be able to make neither head nor tail of it. The language seems confusing. Many broad statements are often made without qualification. Not much of the caution found in the scientific journals is evident. The claims are the worst of all-they may seem to mean absolutely nothing. The patent doesn't read with the lucidity of a textbook either. Of course the reason for this confusion is that the'patent is a legal document and is couched in the h&t legal terminology that the patent attorney can devise. Here in a general sort of way is the manner in which most patents are drawn up. To illustrate it, a typical patent of recent issue will be taken in some detail. In the upper left-hand comer is the date of issue--in this case December 7, 1943. In the upper right-hand comer is the issue number-2,336,267. Below the caption, United States Patent Office, is the patent number, repeated, followed immediately by the title "Method of making airplane fabric." Following the title is the name of the patentee, Robert L. Lester, and his address, Newburgh, N. Y., followed by the assignment-to E. I. du Pont de Nemours & Company, Wilmington, Del. Below the assignment are the
words "no drawing," the application date, March 27, 1942, and the application serial number, 436,477. The last lme of the heading contains the number of claims, 3, and the classification, 117-7. A glance into the Manual of Classification of Patents will show that class 117 is titled "Coating; Processes and miscellaneous products," and it is seen that subclass 7 is for those processes involving stretching or tensioning. The first paragraph of the specificationis a statement of the art to which the invention relates: ". . . coated fabrics, and more particularly to those designed for use in covering air frames of airplanes." The next few paragraphs are a brief summary of the manner in which it has been customary to apply coated fabrics to aircraft surfaces, pointing out the evils and disadvantages of some of the prior methods. I t is pointed out that the general practice has been to "tailor an uncoated fabric to the airframe," then brush or spray coat with about six coats of cellulose derivative dope, drying each one, and sanding two or three times. This older method is relegated to the scrap heap as being both tedious and time-consuming. The next three paragraphs deal with the objects of the present invention. Stated simply, the object is to provide a satisfactory predoped fabric. One paragraph is then devoted to a description of the invention in general terms. It involves coating a
Patented Dec. 7. 1943
UNITED STATES PATENT OFFICE 2,336,267
METAOD OF MAKING AiRPLANE FABRIC Robert L. Lester, Newburgh, N. Y., assignor to E. I. du Pont de Nemours & Company. Wilmington, Del., a corporation of Delaware No Drawins. Application March 27, 1942. Serial No. 436,477 3 Claims. (C1. 117-7) the prior art attempts, in order that the partial!^ This invention relates to coated fabrics, and coated fabric vould shrink after it was attached more particularly to those designed for use in to tile air frame and subsequently wetted with covering air frames of airplanes. additional spray coats, it was necessary to use In the construction of aircraft, the pr3ctice has been to.tailor an uncoated fabric to the air 6 very little or no plasticizer in the pre-doping compcsition. The unplasticized or sliehtly plasframe of an airplane and subsequently by brushticizea coating rendered the fabric too stiff for ing or sl;rnying. or Combination of both methods, satisfactory tailoring to the air framc. When to apply a solution of cellulcse derivative ccatsufficientplasticizer was added to the coating to ing in sufficient quantity to tauten and protect the fabric. The uncoated fabric is sewn in the I0 render the coated fabric sufficiently supple for satisfactory tailoring to the air frame, the coatform of a "sock" and afkr turning it "inside out"
water-wet fabric with a cellulose derivative coating having a very low ratio of softener to film-forming material. The coating dope is made up, applied, and dried, so that the dry coating is deposited in the interstices in a porous condition and capable of penetration by solvents when additional coats of dope are later put on. Then follow three examples of cellulose-derivative dope compositions with directions for treatment of the fabric. The examples are followed by some general observations on their use. In order to broaden the disclosure and obtain as broad claims as possible there are included some suggestions designed to show how the specificexamples may be varied. For example, i t is pointed out that cellulose acetopropionate may be used in place of cellulose acetobutyrate and that the proportions of plasticizer to film-former may be varied more widely than the examples show. Following this is a statement of a few of the advantages of the invention such as: ". . . results in a supple predoped fabric which may be easily and readily tailored to an airframe with no more difficulty than an uncoated fabric." Last are the claims followed by the inventor's printed sipnature. Claim 1 is: - " ~~
"The process of manufacturing predoped airplane fabric of improved pliability and suppleness which comprises wetting the fabric with water, applying thereto a water-insoluble cellulose derivative coating composition containing a volatile solvent for the cellulose derivative, and evaporating said solvent at a rate greater than the evaporation of the water in the said fabric to precipitate the cellulose derivative and render the coating discontinuous."
wary of all such broad assumptions. Too often when certain homologs are tried they give results diierent from those which the patent would have led one to expect. In such case the patent very likely contains some invalid claims, since some of them are drawn to cover too much territory. A general rule might be to assume nothing beyond the actual examples explained in detail in the patent. It is interesting to note that the late W. H. Carothers obtained one of his patents by establishing the fact that glycols of certain carbon chain lengths did not esterify with certain acids to yield resinous products as many previous patents on alkyd resins would have led him to assume. Instead, microcrystalline solids of high molecular weight were produced.' I t must also be remembered that an inventor does not usually disclose every last detail of his process. He often omits mention of those conditions which produce optimum results, although those which he does disclose must produce .the results he describes--oth&se he has a patent that can easily be broken in the courts. It must also be remembered that the information contained in a patent is supposed to be for those "skilled in the art" and it is assumed that people in that category do not need every small direction and detail of nrocedure. The next question that would probably occur to one who at this point desire to become better ac. quakted with the use of Patents is: How can I find the ones which might help me in solving a certain problem, or, which would serve as bases for research 1 am conducting, or, which would give me information on the particular part of chemistry I am now studying? The answer to this question is not too simple, but here are some suggestions. Practically all chemical patents available to us, both our own and those of several foreign countries, are abstracted and listed in Chemical Abstracts. The abstract, however, is usually very brief and may give only the indication that this particular patent does or does not relate to the subject in which one is interested. If i t does, and if i t is a U. S. patent, send 10 cents to the Patent Office in Washington for a printed copy. If i t is a patent from one of the foreign countries with which we have an exchange agreement, photostats of it may be had a t 20 cents per sheet. Another way to obtain all possible patent information relating to a certain subject is to go to Washington and make use of the Patent Office search room. Here there are available classification manuals showing how all U. S. patents are logically arranged in more than 300 classes. Copies of the officialclassification manual are available to the general public a t a cost of one dollar. Class 260 is about the largest single class of chemical patents, although there are also many other classes devoted to this subject. A study of the subclasses under the main class should indicate the ones most
The patent discussed above was taken as an example of a simple and clearly worded disclosure. The claims also are comparatively easily understood. It is a compliment to the company to which this patent is assigned that its patent department draws up patent applications in a simple straightforward manner. It is the misfortune of the patent examiner, and others, that many chemical patents are unduly prolix and difficult to comprehend. The general outline of this particular patent is the one which is usually followed. A patent must he read with certain ideas always in mind. An applicant for a patent is trying to cover as broad a field as possible to prevent later patents from nullifying the effect of his own. Sometimes he has pursued his research far enough to establish the fact that many analogous substances will work in his process and produce satisfactory results. To use one example among many, it is common for inventors working with reactions involving the higher fatty acids to give an example using one of t h e m s a y s t e a r i c a n d then state that other fatty acids will work just as well. They accordingly draw some claims to the use of higher fatty acids in general rather than to any one of them. The Patent Office often allows such claims and the FMNKL,R., with asssistance from HARRY A. N ~ L L E , courts sustain them. The chemist, however, when "Chemists should read pstents." Ckem. Eng. N m r , 19, 1400 using the disclosure of patents in his research, must be (1941).
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likely to contain patents concerned with the information sought. In the search room these subclasses are in the form of boxes called "shoes" which are filled with all the U. S. patents that have ever been issued in that subclass since patents were given order numbers and classified. Along with these are also to be found official cross references from other classes and subclasses which the classification division has deemed pertinent. A complete search involves the use of a great deal of imagination, since all product classes must be considered along with method and composition classes. It would be a very rare case indeed in which a search would lead to but one subclass. The classification of the entire field of modem industrial art is naturally very complicated. The methods used in classifying U. S. patents are to be found in a booklet, "The Classification of Patents," published
by the Government Printing Office (1917). However, this is not up to date; it needs revision. The OficialGazette is published every Tuesday by the Patent Office,and is the best means of keeping up-todate in the patent world. In it are one claim or more and a t least one figure from the patent drawings, if any, of every patent issued since the previous Tuesday. In an average week, a t present, about GOO patents are issued. Of these, about 100 are interesting to the chemist. It does not take too long to scan these hundred or so, but the Oficial Gazette is not to be had in every library. Furthermore, it contains only claims, and these are often useful only to indicate whether the reader should inyestigate the original patent. Many trade journals publish frequent digests of patents issued in their specialized fields. Such a service has recently been offered by THISJOURNAL.
