US41756A - Improved safety-valve attachment - Google Patents

Description

UNITE STATES PATENT OFFICE.

wILLIAM cAMEnEn, or READING, PENNSYLVANIA.

IMPRo'vI-:D SAFETY-VALVE ATTACHMENT.

Specification forming part of Letters Patent No. 41,756, dated March 1, 1864. l

a full, clear, and exact description of the con.-

struction and operation of the same, reference being had to the annexed drawings, making a part of this specifica-tion, and to the letters of referencemarked thereon.

The nature of my invention consists in using a pressure-equalizing spring, A, to make the safety-valve C of a boiler as reliable, or nearly so, as if said valve were held down by what is usually called a dead-weight7 on the end vof the lever D, but dead-weights cannot in all cases be used to advantage-as, for instance, on locomotive-boilers; therefore To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation.

Figure I is the side view of my safety-valve arrangement, where E represents a steamdome, C the safety-valve, D safety-valve lever, B, pressure-indicating spring, usually called spring-balance. F and G are the two arms of a lever which connect the spring-balance B with the pressure equalizing spring A. H is a stand for holding the spring A and the levers F and G.

Figs. II and III are similar arrangements,

and the letters Inarked thereon are corresponding with the letters in Fig. I. These views are intended to show that I do not claimas my invention any particular combination or form of the pressure-equalizing spring A.

It is well known by those skilled in the art, that if a safety-valve lever is fastened to one end of a springbalance and the other end of the same spring-balance is fastened to the boiler or some other xed point, it cannot rise without increase of power over and above the power it was calculated for, for if a safetyvalve is held down by a lever whose proportions for length are as one to ten, said valve cannot be lifted one-eighth of an inch off its seat without raising the end of the lever ten times onefeighth, or one and one-fourth inches, which distance on the ordinary spring-balance is equal to twenty-eight pounds-or, in other words, to pull the spring-balance for holding the end of said lever one and one-fourth inches aparty requires twenty-eight pounds, and which, multiplied by ten, will amount to an additional power of two hundred and eighty pounds on the valve. To avoid such an increase of power, I cause a spring, A, Fig. I, to act on the arms F and G with such a force that it will hold the safety-valve G against the desired steam-pressure, and which pressure may lbe indicated by the usual spring-balance B.

Now, suppose the escape of the steam requires the end of the lever D to ascend from K to L, Fig. I, the ends ofthe arms F and G will turn round the center Ithe same distance without such an increase of power as shown above in the ordinary arrangement, for whatever the spring A is increased in power by being pulled down, the effective length of the arm G is decreased. The calculation of a particular ease as an example will make the above more clear.

Suppose the general arrangement were as shown in Fig. I, and the pressure on the safetyvalve .C to be five hundred pounds, the longitudinal proportions of the lever D are as one to ten. It would require 500-;-1()=50 pounds at the end K, to counterbalauce the pressure on the valve C. The motion of the lever D from K to L is to b e one and seven-eighths inch. The arm F is to move equal distances above and below the horizontal line, and measures four and one-half inches when measured horizontal at either of the extreme positions, its actual length being four and ve-eighths inches. The arm G forms an angle of seventy degrees with the center line of the spring A when the lever D is at K, and a perpendicular from center I to center-line of spring A will, in this case, measure three and one-fourth inches, but when the lever D is atL the angle will then be fty degrees, and the perpendicular from center I to center lineof spring A will then only measure two and one-half inches, the actual length of arm G being three and three-eighths inches. Now, for to calculate the strength of the spring A, I have the following proportions:

First. Si 4%:250 69.23. Si is the effect ive length of arm G. 4 is the effective length of arm F. 50 is the pressure, in pounds, on arm F, and 69,25% is the weight, in pounds, which the spring Awould have to sustain when the lever D is at K.

Second. 2% 4&4: 50 90. 2% is the effective length of arm G. 4% is the effective length of arm 50 is the pressure of pounds on arm F, a d 90 is the weight, in pounds, which the spring A would have to sustain when the lever D is at L4 The elasticity of the spring A would be 9069- 1 2ff-=201l677 pounds in linches7 this being the vertical distance through which the arm Gr moved.

The angles of seventy and fifty degrees, re spectively, could be somewhat altered without much ai'ecting the general result, but I recommend the above angles as convenient, for two reasons: irst, ii'they are much less than seventy and fifty degrees, then the spring A w ll have to have a greater elasticity, which would make itneeessarily long and inconvenient; and, second, if the angles are much more than seventy and fifty degrees, then the arrangement can no more be called a substitute for a deadweight on the lever l), as it would only be correct at the beginning and end ofthe motion it was calculated for, but between these two points it will valy too much to be a great im provement over the old system. From this it will be seen that the success of this arrangement depends on the spring A being,1 such that its elasticity and power increases in propor tion as the length and power of the lever G decreases', which decrease can only be effected by placing the spring A at such an angle with the arm G as will answer the purpose, and it is this particular relation of the spring A to the lever G which I desire to get patented.

I have shown in the accompanying drawings some of the endless variations in which my inode for holding down safety-valve levers is illustrated. In Fig. III the spring A is an elliptical one, and might as wellbe replaced by an indiarubber spring, or any other substance which has strength and elasticity enough to answer the purpose.

What I claim as my invention, and desire to secure by Letters Patent, is-

A pressure-equalizing` spring, A, acting on the safety-valve lever D, in the manner and for the purpose substanii illy as set forth.

WM. CAM ERER.

Wil nesses JNO. C. WoLLrsoN, A JOHN Jos. LAI-IME.

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