T H BURRIDGE STEAM SAFETY VALVE.

Patented Apr. 23, 1867.-

W 'Zizasaes lniteh grates gatmt @ffitje.

THOMAS H. BURRIDGE, OF LOUIS, MISSOURI, ,ASSIGNOR TO HIMSELF AND G. C. FABIAN, OF THE SAME PLACE.

Letters Patent No. 64,070, dated April 23, 1867.

IMPROVEMENT IN STEAM SAFETY-VALVES.

TO ALL VHOM IT MAY CONCERN:

Be it known that I, T. H. BURRIDGE, of St. Louis, in the county of St. Louis, and State of Missouri, have invented certain new and useful improvements in Steam Safety-Valves; and I do hereby declare that thet'ollowing is a full and complete description of the construction and operation of the same, reference being had to the accompanying drawings, making a part of this specification, in which the drawingis a. view of thcvalve apparatus. i

A represents a section of a steam boiler, B the seat of the safetywalve, C the valve, D the link by which the valve is attached to the lever E. F is a supplementary lever, to the free end of whichis attached the weight G. II are standards, to which the levers are pivoted, and I a yoke, by the means of which the lovers are kept in proper relation to each other. It will be seen that the free end of the lcv'er'E is made to curve upward, thus presenting acurving upper side to the lower side of thclever F, which is provided with a corresponding curvature. the two fitting into each other, as shown in the drawing. The position of the levers its thus shown is such as when the valve is at rest or closed. In this position the lever F rests upon the lever E at the point X, and at which point the weight exerts .the least amount of resistance to the pressure of the steam upon the valve, which, by way of illustration, may be supposed to be one hundred pounds, which is as much as the boiler is allowed to carry. Now, if thepressure of the steam be raised above one hundred pounds, the valve opens, and as it opens the effective resistance of the weight increases by the shifting of the points where the two lovers touch; that of the lever E nearer to the free end, and that of F nearer to the pivoted end, thus multiplying the resistance of the weight by changing the relation of thel evers according. to the pressure of the steam above one hundred pounds exerted on the vhlve. By this it will be evident tha-t all excess of steam above one hun dred pounds will he allowed to blow off, and the valve immediately closed when the extra pressure is reduced, whi h is not the case when the ordinary safctywhlve is used, for it will allow thesteam to blow ofi' when below what the boiler may be allowed to carry, for the momentum of the steam will not permit the valve to return to its scat until the pressure of steam in the boiler has sunk very much bclow what the boiler is allowed to bear, and thus occasion a loss of steam. This defect arises from several causes: first, the valve presents a larger surface to the escaping steam when up-aud blowing oil, than when down or closed, hence is required a greater pressure to lift the weight in consequence of this expansion of the steam by the opening oi the valve; secondly, the lever on rising from its station-l position, moves the weight through the arc of a circle, thereby shortening the length of the fulcrum, and, as a conseqiience, more pressure is required to raisethe weight, but the principul reason is the momentum of the steam caused by the blowing off from the boiler. Liquids and fluids being governed by the same law, when at rest or confined, there is a dead pressure, more orless, according to circuun stances; but when allowed t5 escape there is an increased pressure or power from the velocity on the escaping ol' steam. This additional pressure is sometimes so great on the valve as to throw the wcightaud lcvcr entirely From their place, and in most instances prevents the valve f'romaeturning to its scat until the pressurcis very onuch reduced below that allowed the boi|cr to carry, and thus-causing a large waste of steam. By the application of this arrangement of'levers this difliculty is avoided, for it' the steam in the boiler is raised above one hundred pounds to the inch, the lever F will be first raised, and in raising will shift ,the fulcrum in both levers, and thcrchy efi'ecting an increased value of the weight, which extra weight will returu the valve to itsseat at one hundred pounds by'following down the steam as it sinks lower; that is, it will not allow the. velocity of the steam to create a momentum above the static pressure in the boiler of any considerable amount when the valve has returned nearly to its seat. 7

Thus it will hc'sccu that 1 increase the value of the weight on the safety-valve in greater proportiou thau the momentum increases when the steam lifts the valve This compensating power of the lovers meets and resists the increased pressure on tho.valve occasioned by the momentum o'f'thc steam, for suppose the ordinary safetyvalve to be raised out of its normal position bypn excess of steam, then ifa little extra weight is added to the lever the valve will rcturuto its statical position long before it would if allowed to return without this additional weight being applied. The result will be'no loss of steam below what the boiler is allowed 'to carry; but without this additional weight the valve will continue up by the momentum, and the steam escape until the pfessuxe sinks very much below what the boiler will bear, and thus occasion a less of steam. This adaitiorml weight is what this compensating lever will supply, and thereby prevent a loss of steam in blowing ofl -as-nb'oye said.

What I claim as my improvement, and desil e to secure by Letters Patent, is-

.The Levers E F, constructed and arranged in relation to each other-, and valire, substantially as and for the pu rpose set forth. I I V V THOMASH. BURRIDGE.

Witnesses WM. REHBERG, AD. V. WEIsE. J