US155821A - Improvement in safety-valves - Google Patents

Description

U"1\r1Tr.nv STATES PATENT OFFICE.,

EDWARD H. ASHOROFT, OF BOSTON, MASSACHUSETTS.

, IMPROVEMENT `IN SAFETY-VALVES.

Specification forming part o f Letters Patent No. 155,821, dated October 13, 1874; application filed August 27, 1874.

thereon, which form a part of this specifica-- tion- Figure 1 being a sectional elevation of the valve and its case, showing the passage for steam from the generator, the valve resting on its seat, the chamber into which the steam is deflected by the curved lip of the valve,

the apertures through which it passes to the.

outer chamber, and said outer chamber, up through which it passes to the atmosphere. Fig. 2 is a plan View of the valve-case, the valve being removed so as to show the valveseat, and the chambers through which the steam' passes in escaping. Fig. 3 `is a plan view of the valve and its case, the valve being shown in.V position, and Fig. 4 is a plan view of the under surface of the valve, showing the form of the curved lip, and of Vthe wings which guide itin its case.

Corresponding letters refer to like parts in the several figures. l

This invention relates to that type of lsafetyvalveswhich are constructed with reference to having an additionalamouut of lift iniparted to them beyond what is due to" the pressure of steam or other gases upon that portion of their under surfaces which is Within the ground-joint, such additional lift being necessary for the relief of the excess of pressure which accumulates in steam-generators, it being an improvement upon a valve patented in England. on the 21st of January, 1864, by William Naylor, and in this country on the 16th of October, 1866, it having been reissued on the 9th day of October, 1869, in the name of E. H. AsHcRoF'r, as the assignee of the said Naylor. j

rEhe improvement'which forms the subjectmatter of this application consists in providing the case of the valve with an additionalv chamber, through which the steam escapes into the air after it has passed the ground joint andthe chamber surrounding the valveseat, oneV object being to provide the valve as a part of its construction with an escape-passage adjusted, or capable of being adjusted, to produce the required recoil action of the steam in the chamber surrounding the valveseat-or, in other words, to adapt it to any given pressure under Which it is intended to be used-and thus obviate the necessity of depending upon variations inthe size of the escape-pipe to produce that effect, as is the case in the valve constructed and applied in the manner described in the said Naylor patent. In the latter case the degree of the recoil action of the steam against the valve, for further lifting it, is effected, according to the directions of said patent, by varying the size of the escape-pipe bolted to the iiange of the escape-passage of the valve, thus necessarily relying upon the skill and care of the mechanic who .sets the valve upon the boiler to effect its successful operation, according to the design of the inve11tor5but in my valve constructed as herein described that necessity is entirely obviated by the additional or outer case, which permits the requisite adjustment of the valve to the pressure under which it is to be used, independent'of any extraneous appliances.

In constructing valves of this type, and withV my improvement-s attached, I use a case, A,

having upon its lower end a projection, A, which is provided with a screw-thread, or other suitable device, for attaching it to a steamgenerator, pipe, or other vessel inwhi'ch steam or other gas is held, the lower end of said projection being open, in order that a passage may be formed through it and through a pipe,

alternately opened and closed as thepressure v in the generator or other vessel rises above or lhe pipe B just.

falls to the point at which it is desirable to maintain it, a seat, D, is provided, that portion thereof upon which the valve rests being beveled, in order that the valve Amay be made to fit tightly thereon. Outside of the scat this valve is provided with an overhanging downwardly-curved lip, D', its outer diameter being such as to cause it to extend outward to within one-sixty-fourth part of an inch, more or less, of the inner surface of the wall which divides the two chambers or passages, as will soon be described,

the intention being to so arrange these parts,

not be allowed to pass upward and escape di-` rectly into the atmosphere, but shall be deected downward or outward by the lip of the valve into the chamber E, the outer diameter, and, consequently, the area of the cross-section, of which may be varied at pleasure, so as to exert, by the recoil action of the steam therein, the required amount of lifting pressure upon the valve, the force of such action being regulated by the number or area of the openings in the wall of said chamber. As a consequence of this method of constructing the chamber and valve referred to, there is applied to the y under surface of the lip of the valve an'amount of pressure` which will act in conjunction with the steam in the generator, and thus cause it to be raised a greater distance than it would be possible to raise a valve with the pressure of steam acting only upon that portion thereof which is within the ground joint. 'This valve is provided with win gs or with a stem for guiding it in its movements, and is to be held down, so as to control the pressure in the generator in any of the well-known methods, such as by the use of a weight or spring, the latter of which I prefer.

It is apparent that in practice the steam or gas which passes into the chamber E must be allowed to escape therefrom, otherwise the valve could not be seated when the pressure in the generator had been reduced to the proper point, as the valve in closing under such circumstances would have to compress the entire body of steam in such chamber, with the exception of the small quantity which would escape around the lip of the valve, which compression wouldA so delay the valve in its closing movement as to allow sufficient steam to escape from the generator to cause a reduction of the pressure therein to a point considerably below what it was when the valve rose from its seat.

. In order that proper provision may be made for the escape of steam from chamber E in such regulated quantities as to maintain the requisite pressure therein, to aid in holding the valve up the required length of time, and then allow it to seat itself when the pressure in the gen erator has been reduced to, or slightly below, the point atwhich the valve was set to rise, I provide in the wall which separates the inner from the outer chamber, or from the one next to it, when more than two are used, a

number of apertures, G G, of which there may v be one or several. Through these apertures the steam passes to the outer chamber F, its egress being controlled by the area and number thereof. Outside of the last-named chamber the outer wall of the case is placed, and, as said chamber is so constructed that no steam 'can escape therefrom, except at its upper end, it follows that all the steam which passes through the aperturesG will be directed upward, and thus made to pass the upper surface of the valve, in doing lwhich it will cause the atmosphere which is directly above said valve to be displaced and carried away therefrom, and thus the valve will be raised a greater distance from its seat than it otherwise would.

The outer wall of the case of the valve may be extended upward for any desired distance, and thus made toA form a pipe for conducting away the escaping steam, or a pipe for that purpose may be attached to said wall or made to surround it, and extend upward for any desired distance.

I have found, in practice, that the wall .which divides the two chambers of the case should be extended upward somewhat above the lower surface ofthe lip of the valve when said valve rests upon its seat. The distance which said wall extends above the point referred to should be varied according to circumstances, it being one-quarter of an inch, or thereabout.

In constructing large valves of thischaracter it may become necessary to use more than two chambers for the purpose of dividing the volume of the steam into severaL parts, and thus causing it -to act upon a greater area of the atmosphere in escaping.

Having thus described my invention, what .Iclaim, and desire to secure by Letters Patent, 1s

The combination, in a safety-valve, of a case having in it a conduit for conducting the steam from the generator to the under surface of the valve, a chamber into which the steam is directed by the curved lip ofthe valve, a series of apertures for the passage of the steam from the inner to the outer chamber, and one or more chambers outside of the one into which the steam is directed by the valve, the parts being arranged to operate substantially as and for the purpose set forth.

In testimony that I claim the foregoing as my own invention I affix my signature in presence of two witnesses.

EDWARD I-I. ASHOROFT.

Witnesses:

CHAs. E. MARCHAND, C. M. GONNELL.

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