1922, the original contract first became "effective," within the meaning and intention of the parties, when shipments were commenced on October 3, 1922, at which time the contract with the New York Central Lines had in fact been closed, and such New York Central contract thus afforded the means for then fixing price (as of the effective date) and avoided the lapsing of effect of, or revived, the original contract. Each of these contentions presupposes a continuance of binding obligation on both parties under the original contract of November 25, 1921. [1] We are of the opinion that, deliveries not having started on April 1, 1922, and the seller having no contracts with other railroads then in effect, the clearly intended method and means for fixing price failed, the provision as to price became ineffective and inoperative, and the contract became unenforceable by reason of the indefiniteness of this controlling element and the necessity for further agreement thereon. National Imp. & Trading Co., Inc., v. Clark, 270 F. 54 (C. C. A. 2); Weston Paper Mfg. Co. v. Downing Box Co., 293 F. 725 (C. C. A. 7); Louisville Soap Co. v. Taylor et al., 279 F. 470 (C. C. A. 6) 27 A. L. R. 119.

[2] In seeming recognition of this uncertainty as to price, an exchange of views upon the subject was proposed by the purchaser immediately upon the possibility of shipment arising. The fact that both parties considered themselves as bound by the contract of November 25, 1921, at least to the extent of being under obligation to agree upon price, does not affect the situation, since both likewise recognized the necessity of price determination. There was no binding and enforce able contract then in existence between the parties. They were negotiating to make definite and certain that which then was indefinite and uncertain. That which had not been agreed upon was made the subject of agreement. The court may not inquire into the secret or unexpressed intention of one or both of the parties. Its sole duty lies in determining the meaning of the language used when considered in the light of the situation of the parties and the purposes and subjectmatter of the contract. General Supply Co. v. Marden, etc., Co., 276 F. 786-788 (C. C. A. 3); Ryan v. Ohmer, 244 F. 31-34 (C. C. A. 2); Corbett v. Winston Elkhorn Coal Co., 296 F. 577 (C. C. A. 6). So considered, we are of the opinion that the expressed agreement or understanding that the coal should "be billed" the purchaser at $3.50 per ton was not the fixing of a merely tentative or temporary price, for bookkeeping purpos

es, but the determination of a final and ultimate price, for the purposes of the contract, which was thus revived and made effective.

This position is emphasized by application of several of the well-known doctrines in aid of construction. The court will ordinarily give that construction to the language used which conforms to the practical construction placed upon the language by the parties themselves. In the present case the railway company continued to treat the price of $3.50 as the sales price, without reservation or qualification, for several months after it must reasonably have been assumed that contracts with other roads had been entered into by the coal company. Invoices were submitted by the seller and paid by the buyer at that price without question that the sale was thereby definitely completed and the obligations of the parties pro tanto discharged. The correspondence of the parties shows no slightest suggestion that the price fixed was but tentative until after the decline of coal prices and the letter of the seller under date of January 16, 1923, offering refund in the event of extension of the contract and the sale of additional tonnage. Even then the suggestions as to price revision by the buyer were offered in the spirit of seeking favor rather than as an assertion of right. It was only when the buyer apparently contemplated the possibility of securing a price reduction in consideration of the payment of its contract indebtedness without litigation, that the present argument was presented. This is a practical interpretation of the contract by the parties while engaged in its performance and presents one of the most satisfactory tests of the true construction to be applied. Uinta Tunnel Min. & Transp. Co. v. Ajax Gold Mining Co., 141 F. 563 (C. C. A. 8); Kentucky Distilleries & Warehouse Co. v. Lillard et al., 160 F. 34 (C. C. A. 6); Nelson et al. v. Ohio Cultivator Co., 188 F. 620 (C. C. A. 6).

[3] Two other doctrines in aid of construction seem pertinent, namely, that the letter of September 29th having been drawn by the buyer, although accepted by the seller, the provisions of such letter must be most strongly construed against the buyer; and, secondly, the doctrine "expressio unius est exclusio alterius." If any ambiguity arises from the use of the word "billed," the court will lean toward that construction most favorable to the seller; and if the price was not intended to be final, it is almost inconceivable that the parties should have omitted express provision as to the time and method of revision. The mere absence of any such express provi

Suit by the Grand Rapids Refrigerator Company against Philip Ellis Stevens and another, as executors of the estate of Isaac Frank Stevens, deceased. From a decree of dismissal, complainant appeals. Affirmed.

William J. Belknap, of Detroit, Mich. (Frank E. Liverance, Jr., of Grand Rapids, Mich., and J. King Harness, of Detroit, Mich., on the brief), for appellant.

Nathan Heard, of Boston, Mass. (Frederick A. Tennant, of Boston, Mass., and Edward N. Pagelsen, of Detroit, Mich., on the brief), for appellees.

Before DENISON and MOORMAN, Circuit Judges, and HICKENLOOPER, District Judge.

HICKENLOOPER, District Judge. Complainant below appeals from a decree of the District Court dismissing the bill of complaint in an action for alleged infringement of two patents issued to W. H. Whittier-No. 970,672, September 20, 1910; and No. 1,147,288, July 20, 1915.

[1, 2] Claims 7 and 8 of patent No. 970,672 (quoted in the margin 1) pertain directly to a specified form of shelf support in a refrigerator, consisting of a bolt passing through an opening in the porcelain-coated steel lining, and a closed type of nut with washer attached, which, in position, engages the lining and extends inwardly from the refrigerator wall, thus forming a support for the shelf in the provision chamber. In the District Court these claims were held invalid

for want of invention. This precise type of shelf support is old in analogous arts, but its use in combination with the porcelaincoated steel linings of refrigerators is urged as of such great novelty and utility as to be patentable.

Prior to the use of the shelf supports of the patent, all manufacturers of porcelainlined refrigerators used the ordinary screw hook, the screw portion of which was inserted through openings left therefor in the lining and screwed into the wooden casing beyond

until the washer provided at the head of the

17. A refrigerator, comprising a case, a lining

in the case and spaced apart from the same, a shelf support projecting inward from the lining, and engaging the inner surface of the same, and a fastening extending through the lining and into the support and having a head between the lining and case spacing the same apart.

8. In a refrigerator, a lining having an opening, a shelf support engaging the lining at one end and covering said opening, and a fastener

inserted through said opening and within the

support.

screw contacted with or engaged the surface of the lining. Frequent difficulties were encountered in this practice, due to the rigidity of attachment between lining and case and the contraction and expansion to which the lining was subjected by temperature changes. The linings also had a tendency to warp somewhat in the process of baking the porcelain coating, and where the lining bulged inwardly at the opening left for the shelf support, a greatly increased pressure was often necessary to affix it. Thus in inserting the shelf supports, as well as afterwards, there was a marked tendency to chipping of the porcelain. This is said to be avoided in the patented device by attaching the shelf supports to the lining before the lining is placed in the case, by rotating the bolt or threaded portion of the support while that carrying the washer and in contact with the porcelain is held immovable during attachment, and by thus eliminating all stress and strain due both to attaching the shelf support and to temperature changes.

Other advantages are claimed for the new use, such as the fact that the supports are easily cleaned, that the head of the bolt member operates as a spacing means between the lining and the case, and that the washer entirely covers the opening, preventing circulation of air or the entrance of germs; but these are mere incidental results, either existing in the shelf support of the prior art

or of insufficient moment to evidence existence of invention, even if functioning as al

leged, which, in the case of the bolt head of doubtful existence, utility, or necessity. spacing the lining from the case, is at least

We are convinced that in the adoption of

the specific shelf support of the claims in is

sue the patentee exercised no more than a high degree of mechanical ability and power of selection. It may well be that the enumerated advantages of the use of this device in connection with enameled or poreclain-coated metal had not theretofore been recognized, but the device itself is old, and as described in the patent operates in a manner identical with the devices of the prior art. The use of the, shelf support of the patent is only a new or enlarged use of an old device. Such discovery of new uses for or newly observed functions of a device well known in the mechanical or structural arts is not patentable invention. Penn. R. R. v. Locomotive Truck Co., 110 U. S. 490, 4 S. Ct. 220, 28 L. Ed. 222; Dunham Co. v. Cobb, 19 F. (2d) 328, 330 (C. C. A. 6), and especially the very complete treatment of this subject and cita

claims, but restricted to more specific details of construction. Its allowance is requested." The device which it is alleged infringes the claims in suit omits all "means extending over" the outwardly bent portions of the lining, but to attach the lining to the frame use is made of a series of horizontal clamping connections, bolted to the outside walls of the lining by the shelf supports, flanged and perforated at the forward ends and secured to the frame by screws. The outwardly turned edges of the sides of the lining are thus tightly drawn and firmly held to the posts of the frame, but by means not extending into the grooves or over such edges. In both the patent and the alleged infringement the points of contact of the edges of the lining and the posts are hidden by a finishing strip. This is but a very minor detail of construction.

It is now contended, however, that the means claimed in the patent are but the preferred means of attaching the lining to the posts, that the clamping plates of the defendant are but the mechanical equivalents of the means claimed, and that the inventor should be given the benefit of the full scope of his improvement in the art. The decisions of the Supreme Court and of this and other circuits upon the doctrine of the range of equivalents open to a patentee in the protection of his invention, commencing with Winans v. Denmead, 15 How. 330, 14 L. Ed. 717, and extending down to the most recent decisions, are too well known to need citation or individual comment. It is sufficient to say that, in general, the doctrine of these decisions has no application to a case of voluntary limitation by the patentee or of estoppel by Patent Office proceedings. It is manifest that all linings must be firmly attached to the front frame of the refrigerator, and that, if all possible means of such attachment were to be included within the scope of the invention, a lining of the shape disclosed in the patent would itself be patentable, without regard to the means of attachment. Notwithstanding this obvious fact, the patentee canceled his claims for the lining alone, inserted in each claim a provision for attachment in a definite manner, and is now estopped from seeking the benefit of that construction of the claims allowed which would make them the full equivalent of the claims canceled. I. T. S. Rubber Co. v. Essex Rubber Co., 272 U. S. 429, 444, 47 S. Ct. 136 (71 L. Ed. 335);

Campbell v. American Shipbuilding Co., 179 F. 498 (C. C. A. 6); Vanmanen v. Leonard, 248 F. 939 (C. C. A. 6).

While these cases are specific in holding that it is immaterial whether the Examiner was right or wrong in the rejection of the original claim, or in his view of the patentability of the device as originally claimed, the language of the Supreme Court in I. T. S. Rubber Co. v. Essex Rubber Co., supra, is so appropriate to the situation here existing that it seems unnecessary to quote from or comment upon the decisions of this court and those there cited. To quote the language of the Supreme Court is demonstrative of its application:

"So, where an applicant whose claim is rejected on reference to a prior patent, without objection or appeal, voluntarily restricts himself by an amendment of his claim to a specific structure, having thus narrowed his claim in order to obtain a patent, he 'may not. by construction, or by resort to the doctrine of equivalents, give to the claim the larger scope which it might have had without the amendments which amount to a disclaimer.' Weber Elec. Co. v. Freeman Elec. Co., 256 U. S. 668, 677 [41 S. Ct. 600, 603 (65 L. Ed. 1162)]."

By so canceling original claims 1, 2, and 3, the patentee has surrendered all claim to a monopoly in a lining alone of the specific form used by both plaintiff and defendant, and has limited himself to a narrow range of equivalents of the attaching means specifically disclosed and claimed. By the action of the patentee in the Patent Office proceedings, he did give up material rights (Bundy Mfg. Co. v. Detroit Time-Register Co., 94 F. 524 [C. C. A. 6]) in order to secure that which he retained. This does not bar such patentee from relying upon the claims granted (Egry Register Co. v. Standard Register Co., 267 F. 186 [C. C. A. 6]), but it does estop him from now seeking, under the doctrine of equivalents, that which he so specifically relinquished. We are of the opinion that the means used by the defendants for attaching the lining to the frame was a substantial departure from the means specified and claimed in the patent in suit, and it is therefore unnecessary to determine the question of invention. The petition was properly dismissed on the ground of noninfringement.

Judgment affirmed.