US55387A - Improvement in piston-heads for steam-engines - Google Patents

Description

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EDWARD SULLIVAN, OF PITTSBURG, PENNSYLVANIA.

Specication forming part of Letters Patent No. 55,387, dated June 5, 1866.

To all whom t may concern.'

Be it known that I, EDWARD SULLIVAN, of the city of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Piston-Heads for Steam-Engines; and I do hereby declare the following to be a full, clear, and exact description thereof, reference being had to the annexed drawings, in which- Figure l is a section through the axis of the piston head and rod. Figs. 2 and 3 are sections through the axis of the valve for admitting steam into the piston-head.

In each of the iigures like letters denote similar parts.

My improvement has for its object the admission of live steam into the interior of the hollow pistonhead of a steam-cylinder furnished with metallic ring-packin g by means of a self-acting valve or valves so constructed as to produce a uniform pressure of steam on all points of the inner circumference of the ring-packing, such pressure being less in degree than that of the live steam in the cylinder and bearing any required proportion thereto.

In piston-heads of steam-cylinders in which live steam from the cylinder is admitted into the piston-head in the rear of the expansible metallic packing for the purpose of pressing the rings outward, and thus keeping the packing-rings tight, notwithstanding the gradual-` abrasion of the metal of which they are composed, the pressure ofthe steam is so great as to cause an excessive friction, which not only rapidly wears away the cylinder and packing, but involvesaserious loss of power. In order therefore to overcome this difficulty and secure a uniform and sufficient but not excessive pressure of live steam on the inner surface of the rings of metallic packing within the piston-head, I have invented a valve, of which one or more are placed on each side of the piston-head, and which is so constructed as to present a much larger area of surface to the steam inside of the piston-head than it does to the steam in the cylinder,and which,being opened by the pressure of the steam in the cylinder to admit steam into the piston-head, is self-closed so soon as the pressure of steam on the larger surface within the piston-head exceeds the pressure on the smaller surface outside.

In order to enable others skilled in the art to construct and use my improvement, I will proceed to describe its construction and operation.

In the drawings, Fig. 1, a is the piston-rod, to which is attached the upper disk, b, of the piston-head. ois the lower disk or cap, which is fastened by screws s s, or otherwise, to the block d, which is an extension of the pistonrod. below the upper disk, b. e is a ring or hollow cylinder o f iron or brass placed between the disks b and c, forming the sides of the piston-head. rIlhe ringI e is splitor out through from top to bottom (or else has holes through it) to allow the steam to pass out from the cavity of the piston-head to the narrow space between the outer surface of the ring e and the inner surface ofthe packing-rings fff. These packing-rings are made ot' the usual material, being metallic rings cut at one point, or in sections, and placed outside of the ring e, between the two disks b and c, so as to leave a narrow space, t', between the outside of the ring e and the inner surface of the packingrings j'. A valve, g, made of brass or other suitable material, is screwed into around hole in the upper disk, b, and a similar valve into the lower disk, e, the valves being placed so as to project into the cavityof thepiston-head and to protrude very slightly, if at all, from the outer surface of the disks.

The construction of there valves is shown in Figs. 2 and 3, which are sections through the axis of the valve, the valve being represented as open in Fig. 2 and closedin Fig. 3.

rPhe external shape of the valves g is cylindrical, of uniform diameter, excepting at one end ath, where the diameter is reduced and the surface is tapped with screw-thread by which it is screwed into the disks c and b, the length of the screw being' equal to the thickness of the disk into which it is to be inserted.

The valve g is bored through from top to loottom, the upper portionof the bore (marked 7c) being cylindrical, and of larger diameter than the lower portion, l, the difference in diameter between the upper and lower portions of the bore being proportioned according to the relative degree of pressure of steam required lfor the inside and outside of the piston-head in inverse ratio, so that if the pressure of steam inside the piston-head is desired to be onefourth'of that in the cylinder of the engine the area of the, larger bore k is made four times as great as that of the smaller bore-l. The lowest portion of the bore of the valve may be still further reduced, as shown at m, Figs. 2 and 3, for the reason hereinafter stated.

On top of the valve-cylinder g is screwed a cap, n, which also has a hole, o, the diameter of which on the under side of the cap is equal to the diameter of the largest part 7c of the bore of the cylinder g, but which tapers slightly upward, so as to prevent the valve-piston p being blown out of the cylinder g. The valvepiston p is a cylindrical metallic disk which fits in the large bore 7o of the cylinder g, and is furnished with a stem, q, on its under side, which enters and its accurately in the lesser bore l. The depth of the large bore 7c is sufficient to allow the piston p to rise high enough to elevate the bottoni of the stein q above the transverse passages 'r i', bored through the axis ofthe cylinder g, and intersecting each other in the lesser bore l of the cylinder g, as seen in Fig. 2. When the piston p is down the steln q covers the mouth of the passages fr r and closes the communication between the bore b and the passages r 1^. When the piston is down, as in Fig. 3, the'lower end of the stem q rests o n a ledge formed by the slight reduction of diameter' of the bore of the cylinder g below that point, as before stated.

The valves constructed as described, and screwed into the upper andlower disks, b and c, of the piston-head ,operate as follows: When the live steam in the cylinder of the engine is pressing upon the under side of the piston-head it enters the bore m in the valve-cylinder g, and pressing upon the end of the stem g, raises the valve-piston p to the position shown in Fig. 2, opening the passages i" r, through which the live steam rushes into the interior ofthe piston-head, filling its cavity and finding its way through theslit or openings inthe ring e, into the space i, back of the packing-rings f f f, and pressing them outward against the inner surface of the cylinder of the engine. So soon as the pressure of the steam inside of the pistonhead on the surface of the top of the piston p exceeds the pressure on the Linder side of the stem q the piston p will be forced down, closing the apertures or passages o" i, and preventing the further access of steam, and as the surfacearea of the piston p exposed to the action of the steam within the piston-head is greater than the surface-area ofthe under side of the stem q exposed to the action of the steam in the steam-cylinder of the engine, the pistonvalve p will close, while the pressure of steam per square inch is proportionally less in the piston-head than in the cylinder of the engin e. Ifthepiston p and the stem q be of such relative diameters that the area of the former be equal to sixteen times the area of the latter, (their diameters being in the ratio of one to four,) then a pressure of steam within the piston-head of twenty pounds per square inch on the piston p of the valve will balance a pressure of steam of three li undred andtwenty pounds per square cient pressure of steam may he applied to forcev out the packing-rings, and that this pressure will always bear a certain relative proportion to the working pressure of the steam in the engine; and that the pressure applied to the packing-rings will be uniform on all the rings, and not., as is the case in many piston-heads where steam is employed for forcing out the packing, operating on different rings during each stroke of the engine.

' An important feature of my improvement is that my valve in the piston-head does not open and close on every change of stroke of the engine, but retains the steam within the piston, and only opens to admit more steam as and when the pressure of steam within the piston-head falls below the required point. This not only prevents a waste of steam, but, which is more important, obviates the constant shufiling of the packing-rings, caused by suecessive expansions and contractions, which take place when the steam is allowed to escape from the piston-head on the change of stroke, and which causes the rings to wear away more rapidly and injures the surface of the steamcylinder. y

The operation of the valve g on the upper side of the piston-head, when the live steam is above the piston, is similar to that already described in relation to the valve on the under side of the piston-head.

lf preferred, two or more valves may be used on each side of the piston-head.

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

1. The use, in piston-heads of steam-engines furnished with expandin gpacking-rings, of one or more self-actin g valves for the admission of steam therein, each valve consisting of a single valve piston or plunger so arranged that the live steam shall press -on both ends of the plunger at thesame time, one from the inside of the piston-head and the other from the outside, the area of the two ends of the valveplunger diifering in proportion to the relative desired pressure of the steam on the exterior of the piston-head and on the packing-rings within the piston-head, substantially as and for the purpose hereinbefore described.

2. The combination of the valve-cylinder g, piston p, and stem g, forminga self-acting valve for the admission of steam into the interior of piston-heads for regulating the pressure of steam on the packing-rin gs, constructed and operating substantially as hereinbefore described.

3. Combining with the piston-head of a steam-engine having expanding packing-rings a device constructed and operating substantially as hereinbefore described, so as to retain In testimony whereof I, Jche said EDWARD SULLIVAN, have hereunto set my hand.

EDWARD SULLIVAN.

Wi tnesses W. BAImWELL, ALLAN C. BAKEWELL.v

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