steam as that disclaimed in the English patent, and shows that the disclaimer was in all probability made because it was well known to the patentee and to the officials who issued the letters patent that another was the original and first inventor of the patented valve. Nothing of the kind is embraced in the claims of the English patent granted to the patentee, nor is there anything in the specification which has any tendency to show that the patentee ever supposed that he invented that feature of the improved valve which he disclaimed.

Two patents for the improvement have been granted in this country, one (the original) to the alleged inventor, and the reissued patent to the complainant, on which the suit is founded. Neither of the patents granted contain any disclaimer of the kind mentioned in the English patent, though it is conceded that both the original and the reissued patent were granted for the same invention as the English patent. Nor could that concession properly be withheld, as it is as certain as truth that the feature of the steam-valve in question was fully and clearly described in that specification, and that the patentee stated that he wished it to be understood that he did not lay any claim to the recoil action, nor to the extension of the valve laterally beyond its seat.

Explicit as that disclaimer is, still it is assigned for error by the complainant that the circuit judge erred in giving weight to it, but the court here is of the opinion that there is no merit in that objection. Instead of that, the court decides that the patent in suit, in order that it may be held valid, must be construed in view of the disclaimer contained in that patent and be limited to the particular devices shown in the specification for effecting such recoil action of the steam.

Taken as a whole, the facts show conclusively that the assignor of the complainant was not the first person to devise means for using the recoil action of steam to assist in lifting the seat of the steam-valve, for the purpose described, and it follows that the patent in suit must be limited to what he actually invented, which is the devices shown in the specification and drawings, to enable the party to avail himself of such recoil action.

Decided support to that view is found in the specification of the Beyer patent, which shows that the apparatus in question had an overhanging downward-curved lip and an annular recess, into which the steam was directed downward on issuing between the valve and its seat, while a portion of the steam impinged against the projecting part of the valve. Viewed in the light of that suggestion, it is clear, as decided by the circuit.judge, that the assignee of the invention in controversy cannot claim that Naylor was the original and first inventor of that feature of the improvement, nor can it properly be claimed that he invented the combina tion in a spring safety-valve of every form of a projecting overhanging downward-curved lip in such a device, with the annular recess surrounding the valve-seat, into which a portion of the steam is directed as it issues between the valve and its seat. Limited in that way, as the

patent must be in order that it may be upheld as valid, the question remains whether it has been infringed by the respondents.

Throughout the steam-valve used by the respondents is the valve patented to George W. Richardson, whose patent makes a part of the record. He obtained his patent September 25, 1866, nearly a month earlier than the date of the original American patent granted to Naylor. His invention, as he describes it, consists in increasing the area of the head of the common safety-valve, outside of its ground joint, and terminating it in such a way as to form an increased resisting surface, against which the steam escaping from the generator shall act with additional force after lifting the valve from its seat at the ground joint, and so, by overcoming the rapidly-increasing resistance of the spring or scales, will insure the lifting of the valve still higher, thus affording so certain and free a passage for the steam to escape as effectually to prevent the bursting of the boiler or generator, even when the steam is shut off and the damper left open.

Safety-valves previously in use were not suited to accomplish what was desired, which was to open for the purpose of relieving the boiler, and then to close again at a pressure as near as possible to that at which the valve opened. Sufficient appears to show that Richardson so far accomplished that purpose as to invent a valve which would open at the given pressure to which the valve was adjusted and relieve the boiler, and then close again when the pressure was reduced about two and onehalf pounds to the inch, even when the pressure in the generator was one hundred pounds to the same extent of surface, which made it in pactice a useful spring safety-valve, as proved by the fact that it went almost immediately into general use.

Other inventors prior in date to the Naylor invention attempted to make the desired improvement in the common safety-valve, and it is evident from what appears in the record that the efforts of one or more of them besides Beyer were attended with more or less success; but it is unnecessary to enter into those details, as it is obvious, from what appears in the Beyer patent, that Naylor did not invent the overhanging downward-curved lip of the improved valve, nor was he the first to use an annular chamber surrounding the valve-seat, into which a portion of the steam is deflected as it issues between the valve and its seat; and the court here concurs with the circuit judge that his patent must be limited to the combination of the other elements with such an annular recess as he has described, and operating in the described manner, so far as such recess, separately considered or in combination, differs in construction and mode of operation from the patented steam-valves which preceded it, as shown in the evidence giving the antecedent state of the art. From which it follows that the claims of the reissued patent in suit cannot be held to cover the safety valve used by the respondents, which in its construction and mode of operation is substantially different, as appears from a comparison of the models and an inspection of

the drawings, as well as from the description given of the same in the respective specifications.

Support to that view of a decisive character is also derived from the testimony of the expert witnesses on both sides. Enough appears in the explanations of the specification and the expert testimony to satisfy the court that it was the intention of the inventor of the complainant's valve to use the impact of the issuing steam upon the concave lip of the valve to assist in lifting it without other aid, except so far as it was helped by the diminution of atmospheric pressure on the top of the valve, consequent upon the issuing of a portion of the steam in an upward direction around the periphery of the valve, the annular chamber into which the steam is discharged on leaving the valve serving no other purpose than that of a conduit for the steam, if the valve is constructed in accordance with the drawings of the original patent.

Examined in the light of these suggestions, it is plain that the steamvalve used by the respondents cannot be held to be an infringement of that described in the specification of either of the three patents representing the invention claimed by the complainant.

Coming to the specification that describes the steam-valve used by the respondents, it will at once be seen that its construction and mode of operation are substantially different in important particulars, as follows: When the valve opens, the steam expands and flows into the annular space around the ground joint. Its free escape, which might otherwise be too free, is prevented by a stricture or narrow space formed by the outer edge of the lip and the valve-seat. By these means the steam escaping from the valve is made to act by its expansive force upon an additional area outside of the device, as ordinarily constructed, to assist in raising the valve, the stricture being enlarged as the valve is lifted from its seat, and varying in size as the quantity of the issuing steam increases or diminishes.

Important functions, not very dissimilar in the effect produced, are performed by the two patented valves in controversy; but the means shown in the respective specifications and the mode of operation described to produce the effect are substantially different in material respects, which shows to a demonstration that the complainant cannot prevail, unless it can be held that his assignor invented the overhanging downward-curved lip, and that he was the first to use an annular chamber surrounding the valve-seat, into which a portion of the steam is deflected as it issues between the valve and its seat. Neither of these conditions can be found in favor of the complainant, and of course it cannot be held that the respondents have infringed his patent.

Confirmation of that conclusion of the most conclusive character is found in the testimony of the experts, which will not be reproduced, as it would extend the opinion beyond a reasonable length.

Experiments almost without number were made by the experts, and the court is furnished with very many exhibits intended to explain the

construction and mode of operation of the different steam-valves described in the various patents given in evidence in the case; but the court has not found it necessary to enter into those details, preferring to rest the decision upon the construction of the complainant's patent, and his failure to show that it has been infringed by the respondents.

Decree affirmed.

HYNDMAN v. ROOTS ET AL.

(O. G., vol. xiii, p. 868.)

[Supreme Court of the United States. No. 252. October Term, 1877.]

1. The validity of Reissue Letters Patent No. 3,570, granted P. H. and F. M. Roots, July 27, 1869, for a rotary blower, sustained.

2. An invention which consists in surface-coating the interior of a blower-case—i. e., its end pieces or head-plates and the concaves-with plaster-of-paris or equivalent, so that the revolving pistons will work true and air-tight, is clearly infringed by the substitution of a composition of litharge and glycerine for the plaster.

3. For the purposes of the invention, the composition is the substantial equivalent of the plaster, and its use a palpable evasion of the patent.

4. Where the concave arcs of the blower were made of a certain size, and located in certain relation to the axes of the revolving piston-sweeps, so that the entire casing might be cast in one piece, and yet permit the ready removal of the abutments and pistons: Held, that to copy the proportions and relative position of the arcs. was none the less an infringement, even though the respondent did not make his casing in one piece.

APPEAL from the circuit court of the United States for the southern district of Ohio.

Messrs. Wood & Boyd for appellant.

Mr. James Moore for appellees.

Mr. Justice SWAYNE delivered the opinion of the court:

This is a case in equity. The bill is founded upon two patents. One of them is Reissue No. 3,570. It bears date on the 27th of July, 1869. The original of this reissue bore date on the 11th of August, 1868. The other patent is dated June 21, 1870. It is numbered 104,585, and was issued to the appellees as the assignees of Hardy and Wood, the alleged inventors.

The bill was dismissed at the hearing as to this latter patent, and no appeal was taken. It may, therefore, be laid out of view, and will not be again adverted to. The other original patent and the reissue are for improvements in cases for rotary blowers.

The bill charges infringement, and prays for an injunction and a decree for profits and damages. The answer denies the novelty of the alleged invention; denies that the reissue is for the same thing as the original patent; denies that the complainants were joint inventors, if inventors at all, and denies infringement.

Such were the issues made by the appellant in the court below. That court found all of them in favor of the appellees, and decreed accordingly.

Here the same points have been insisted upon.

In relation to all of them, except the one last mentioned, we deem it sufficient to say that we concur with the court below. We think the evidence leaves no room for reasonable doubt as to either of them. The questions are questions of fact. No legal proposition is involved. To analyze the testimony in order to vindicate our conclusions would serve no useful purpose. Our further remarks will be confined to the subject of infringement. That is the hinge of the controversy between the parties.

It is difficult to convey clear ideas of complex machinery by any description that can be given. Drawings are more effectual, and models are still more so. If the model be full and accurate, it is, indeed, the thing itself in miniature.

The appellees, as the case is before us, confine their claims to improvements in the shell or case of blowers. The internal mechanism is in no wise in question. They say the objects of their invention were to avoid the necessity of boring out the interior concave surfaces of the case, and of facing-off or planing the head-plates, and to render it practicable to cast the entire outside casing in one piece. They describe two modes of making the blower-heads true. One is to form them into planes at right angles to the shafts of the abutments, parallel with each other, equidistant from each other in all their parts, by giving to the inner surface of each plate a coating of plaster-of-paris, ydraulic cement, or other material having like plastic properties. This is suited to blowers of the smaller sizes. When this method is used the plaster-of-paris may be put on while in a plastic condition by means of a sweep made to turn in the boxes of the blower-shafts, so that it will shape the linings of the ends as may be desired.

The second method is to use inside or secondary metal plates made in their outlines to conform to the interior of the case, and to face or plane them off, so as to make them perfectly true. A space is left between these secondary plates and the ends of the case, which is filled with plaster-of-paris of the proper consistency. After the plaster has set, the plates are secured in their places in any suitable manner. In making the inner surface of the arcs of the case true, the usual way of the patentees is to work from the center of the shaft-journals as fixed points. They give the inner part of the concaves a coating of plaster-of-paris, and work it into the proper shape and proportions while it is setting, by means of a sweep attached to a shaft turning in the journal-boxes of the blower as in the case of the head-plates when plaster is applied to them. While the plaster or other similar material is becoming set, they slowly move the sweep, so as to give the coating exactly the required shape and thickness. Sometimes, instead of using the sweep, they use a cylinder