U.S. Supreme Court
Ashcroft v. Railroad Company, 97 U.S. 189 (1877)
Ashcroft v. Railroad Company
97 U.S. 189
1. Reissued letters patent No. 3727, granted by the United States, Nov. 9, 1869, to Edward H. Ashcroft, assignee of William Naylor, for an improvement in steam safety valves, being a reissue of original letters No. 58,962, granted to Naylor Oct. 16, 1866, cannot, in view of the disclaimer of said Naylor in his specification, upon which English letters patent No. 1830 were sealed to him Jan. 19, 1864, and of the prior state of the art, be construed to embrace a combination, in every form of spring safety valve, of a projecting, overhanging, downward curved lip or periphery, with an annular recess or chamber surrounding the valve seat, into which a portion of the steam is deflected as it issues between the valve and its seat, but must be limited to a combination of the other elements of his device, with such an annular recess of the precise form, and operating in the manner described, so far as such recess, separately or in combination, differs in construction or mode of operation from those which preceded it.
2. Said reissued letters, thus limited, are not infringed by the use of a steam safety valve made in substantial compliance with the specification of letters patent No. 58,294, granted Sept. 25, 1866, to George W. Richardson.
English letters patent No. 1830, dated July 21, 1863, and sealed Jan. 19, 1864, were granted to William Naylor, of England, for improvements in safety valves and in apparatus connected therewith. The specification describes his invention as consisting,
"when using a spring for resisting the valve from opening, in the employment of a lever of the first order, one end resting by a suitable pin upon the safety valve, and the other end of the lever resting upon the spring, the end resting upon the spring being bent downwards to an angle of about forty five degrees from the fulcrum, so that when the valve is raised by the steam the other end of the lever is depressed upon the spring downwards, and at the same time is moved inwards towards the fulcrum, thus virtually shortening the end of the lever, and thereby counteracting the additional load upon the valve as it is raised from its seat by the greater amount of compression put upon the spring."
He also describes a contrivance consisting of a lateral branch or escape passage for a portion of the steam after it has passed the valve, the valve being made to project over the edges of the exit passage, the projecting edges of the valve being made to curve chanroblesvirtualawlibrary
slightly downwards, so that the steam on issuing between the valve and its seat will impinge against the curved projecting portion of the valve, and a portion of it be directed downwards into the annular chamber surrounding the central passage, which chamber communicates at once with the branch exit pipe, whilst the other portion of the steam ascends past the edges of the valve. He then says,
"By this means I am enabled to avail myself of the recoil action of the steam against the valve, for the purpose of facilitating the further lifting of such valve when once opened; but I wish it to be understood that I lay no claim to such recoil action, nor to the extension of the valve laterally beyond its seat."
The specification of English letters patent No. 1038, granted to Charles Beyer for improvements in safety valves, dated April 25, 1863, and sealed Oct. 16, 1863, describes his invention as consisting
"in forming a flange around the valve, commencing at the outer edge of the valve facing, which flange is under cut and concave in shape, and the concave side is towards the seating of the valve, which has also a flange upon it, commencing at the outer edge of the valve seating, but the upper surface of this flange is convex, and corresponds nearly to the concave surface of the flange upon the valve. There is a slight space between the concave and convex surfaces of the two flanges, which diminishes towards the outer edges of the flanges. When the steam begins to escape from between the surfaces of the valve, it gets between the concave and convex surfaces of the two flanges, and its force thus acts upon a larger area, and reacts upon the concave surface of the valve, and causes it to open to a greater extent than the ordinary valve."
Letters patent of the United States No. 58,962 were issued, Oct. 16, 1866, to said Naylor for an improvement in safety valves. The description of his invention in the specification is substantially the same as in that of his English patent. Nothing is said, however, of availing himself of the "recoil action of the steam against the valve, for the purpose of facilitating the further lifting of such valve when once opened;" nor is there any disclaimer, as in the English specification, of the recoil action and the extension of the valve laterally beyond its seat. The claim of the specification was the arrangement chanroblesvirtualawlibrary
in safety valves "of bent levers of the first order, acting in combination with a spring or springs, the whole operating in the manner and for the purpose set forth." Sept. 8, 1869, Naylor assigned his letters patent to Edward H. Ashcroft, who thereupon surrendered them for reissue. The specification of the reissued letters to Ashcroft, as the assignee of Naylor, which are No. 3,727, and bear date Nov. 9, 1869, declares that the main object to be attained by the invention, viz., the counteracting the additional load upon the valve as it is raised from its seat produced by the increased resistance of the spring,
"is accomplished by using a lever of the first order, one end resting by a suitable pin upon the safety valve, constructed and arranged as hereinafter described, and the other end of the lever resting upon a spring; but, in lieu of having this lever straight or nearly so, I propose to bend downward that end which is acted upon by the spring to an angle of about forty five degrees, so that when the valve is raised by the steam the other end of the lever is depressed upon or against the spring downward, and at the same time is moved inward toward the fulcrum, thus virtually shortening the end of the lever, and thereby counteracting the additional load upon the valve as it is raised from its seat by the greater amount of compression or tension, as the case may be, which is put upon the spring; and my invention also consists in the valve C, constructed with projecting downward curved lip or periphery, and in the annular chamber D, surrounding the valve seat, whereby, as the spring is compressed by the lifting of the valve, the projecting lip of the valve and the annular recess are available in causing an increased pressure on the valve, and thus overcome the increased resistance of the spring, due to its compression, as hereinafter more fully set forth."
"Figs. 1 and 2 represent, respectively, a vertical section and front elevation of a safety valve constructed according to my invention."
"A is the main thoroughfare, leading directly from the boiler; B, a lateral branch or escape passage for a portion of the steam after it has passed the valve C. I make this valve to project over the edges of the exit passage A, and to curve its projecting edges slightly downward, as shown in Fig. 1, so
that the steam, on issuing between the valve and its seat, will impinge against the curved projecting portion of the valve, andp align="justify"> that the steam, on issuing between the valve and its seat, will impinge against the curved projecting portion of the valve, andp align="justify"> that the steam, on issuing between the valve and its seat, will impinge against the curved projecting portion of the valve, and a portion of it will be directed downward into the annular chamber D, surrounding the central passage A, and communicating with the exit pipe B, while the other portion of the steam ascends past the edge of the valve."
The claims of the reissue are:
"1. The combination and arrangement, with the hereinbefore described safety valve, of bent levers of the first order, and the spring or springs, in the manner substantially as hereinbefore set forth."
"2. The safety valve C, with its overhanging, downward curved lip or periphery, and annular recess D, substantially as herein shown and described, and for the purpose set forth."
"3. The annular recess D, surrounding the valve seat, substantially as herein set forth."
"4. The combination of the valve C and the annular recess D, as herein set forth, and for the purpose described."
Figs. 1 and 2 are as follows:
Dec. 14, 1869, this bill was filed by Ashcroft, to enjoin the alleged infringement by the Boston and Lowell Railroad Company of his reissued letters. The answer denied that they were for the same invention as that described in the original letters, that Naylor was the first and original inventor of the improvements specified in the reissued letters, or that they embrace the valve used by the company, and averred that the valves used by it were described by and embraced in letters patent of a prior date to that of Naylor's invention, and were made under letters patent No. 58,294, granted by the United States, Sept. 25, 1866, to George W. Richardson.
The specification of Richardson's patent describes his invention as follows:
"E E is the valve seat."
"F F is the ground joint of the valve and seat."
"P is the countersink or centre upon which the point of the stud extending from the scale lever rests in the usual manner."
"The nature of my invention 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, 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 damper left open."
"To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation. To the head of the common safety valve, indicated by all that portion of Fig. 2 lying within the second circle from the common centre, I add what is indicated by all that portion lying outside of the said circle, in about the proportion shown in the figure. A transverse vertical section of this added portion is indicated, in Fig. 4, by those portions of the figure lying outside of the dotted lines p p, p p, while all that portion lying within the dotted lines p p, p p indicates a transverse vertical section of the common safety valve alone. This increased area may be made by adding to a safety valve already in use, or by casting the whole entire. "
"I terminate this addition to the head of the valve with a circular or annular flange or lip c c, which projects beyond the valve seat E E, Fig. 3, and extends slightly below its outer edge, fitting loosely around it and forming the circular or annular chamber D D, whose transverse section, shown in the figure, may be of any desirable form or size. This flange or lip c c, fitting loosely around the valve seat E E, is separated from it by about 1/64th of an inch for an ordinary spring or balance. For a strong spring or balance this space should be diminished, and for a weak spring or balance it should be increased to regulate the escape of the steam as required. Instead of having the flange or lip c c project beyond, and extend below and around the outer edge of the valve seat, as shown in Fig. 3, a similar result may be attained by having the valve seat itself project beyond the outer edge of the valve head and terminating it with a circular or annular flange or lip, extending slightly above and fitting loosely around the outer edge of the flange or lip c c of the valve head, but I consider the construction shown in Fig. 3 preferable."
"With my improved safety valve, constructed as now described, and attached to the generator in the usual way, the steam escaping in the direction indicated by the arrows in Fig. 3 first lifts the valve from its seat at the ground joint E F, and then, passing into the annular chamber D D, acts against the increased surface of the valve head, and by this means, together with its reaction produced by being thrown downwards upon the valve seat F E, it overcomes the rapidly increasing resistance of the spring or balance, lifts the valve still higher, and escapes freely into the open air until the pressure in the generator is reduced to the degree desired, when the valve will be immediately closed by the tension of the spring or balance. The escape of the steam, by means of this safety valve, is so certain and free, that the pressure of the steam in the generator or boiler will not increase beyond the point or degree at which the valve is set to blow off."
"What I claim as my improvement, and desire to secure by letters patent, is a safety valve with the circular or annular flange or lip c c constructed in the manner, or substantially in the manner, shown, so as to operate as and for the purpose herein described."
The drawings referred to in Richardson's specification are as follows: chanroblesvirtualawlibrary
The court below, upon final hearing, dismissed the bill, upon the ground that there was no infringement. The complainant then appealed here.