US205723A - Improvement in balanced slide-valves - Google Patents

Description

J. C. BRYAN. Balanced Slide-Valves.

No. 205,723. Patented July 9,1878..

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UNITED STATES PATENT OEEIcE.

JOHN C. BRYAN, OF TITUSVILLE, PENNSYLVANIA.

IMPROVEMENT IN BALANCED SLIDE-VALVES.

Spe/rlication forming part of' Letters Patent N0. 205,723, dated July 9, 1878, application tiledl Y April 29, 187e.

To all whom it may concern.:

Be it known that I, JOHN C. BRYAN, of .litusville, county ot' Crawford, and State of Pennsylvania, have invented or discovered 'a new and useful Improvement in Balanced Slide-Valves; and I do hereby declare the following to be a full, clear, concise, and exact description thereof, reference being had to the accompanyingdrawing, making a part of this specication, in which-like letters indicating like parts- Figure l is a longitudinal vertical sectional view of a steam chest, valve, and ports, illustrative of my improvement. Fig. 2 is a like view, showing the valve in a different position relative to its ports. Fig. 3 is a cross-section in the plane of the line m x, Fig. l; and Fig. et is a detached View, in perspective, of the valve, and showing the lower face ofthe relief or balancing plate.

The side walls o' an ordinary steam-chest are shown at A, the bottom at Al, and the top plate at A2.

The steam-ports a a', of the usual or any known construction, lead to the opposite ends ofthe cylinder. Steam is admitted from the steam-generator at B, and passes into the valve by the port I). The live steam admitted by this port passes alternately by ports c a to the cylinder, and the exhaust-steam goes into he steam-chest and out by the exhaust-ports My improved valve D has a middle part, open at top and bottom, but incloscd laterally all around by Walls d d1 d'2 d3. I hus far the valve is believed to be old. Above it is a relief or balancing' plate, l), having rabbeted edges, as shown, which underlie the edges of a hole made in the top plate A2 of the steamchest. The upper face of the balancing-plate Pis, by preference, made so as, in its usual position, to be about flush with the upper or outer face of the steam-chest cover, so as to permit of the use of a ilexible gasket or plate, c, which overlaps the joints, and is secured at its 'edges outside the joints by a cover, n, chambered out on its under side, as at u. The gasket c consists of a thin plate of copper, or other suitable material, and its elasticity is such, and the construction of the plate P is such, that the latter may have a slight vertical motion oi', say, the one-sixteenth of an inch, more or less. A hole, el, is made ceutrally through the balancing-plate P for the admission of live steam to the chamber u', and the gasket is fastened down around the hole by a washer and screws, as shown at c2.

The parts described are so proportioned that the area of surface on the under side of the balancing-plate P subject to steam-pressure through the open top of the valve shall be somewhat less than the area of its upper surface included within the chamber n subject to downward steam-pressure, so that, in the manner well known in the art, the valve will be held down to its seat with the proper degree or amount of force or pressure. The rules governing this are too well known to skilled engine-builders to need further statement.

Further features of improvement are design ed to obviate certain practical difficulties, which I have found to exist in this class of balanced valves. First, when the valve begins a stroke either way, one foot or lower face of the valve commences to eut oft' the supply of live steam to one end of the cylinder. lVhile that part of the valve is passing that particular port, the expansive force of th e steam, acting back through the port, tends to lift that end ofthe valve and thus tilt it on its transverse axis, thus causing it to leak and `subject the gasket e to an irregular breaking-strain. To remedy this, I lengthen the valve D by-extending its side walls at each end, as at e, and, by preference, connect the extreme upper and lower faces of the end extensions e by means of cross-bars e', and make the upper face of the upper bar and extension and the lower face of the lower bar and extension preferably in the plane of the upper L,and lower valvefaces, respectively.

The extensions thus formed bear on the valveseat below while the valve is subjected to the vlifting effect referred to on the balancingplate above, or ou the extended edge of the same, and outside of the vertical plane of the upward pressure. Such extension ofthe valve,

in its relation to the bearing-surfaces, has the l effect to prevent or lessen the tilting referred to, in accordance'with principles of leverage well understood in mechanics.

Another practical difficulty which I obviate results from the upward pressure of the valve ends, already referred to, against the ends of the balancing-plate, which, in addition to evils already mentioned, causes undue friction and cutting at such points. To prevent or lessen this, I pack or cushion the upper faces of the valve ends while passing the ports on return strokes by means of live steam. For this purpose I make recesses s s' in the lower face of the balancing-plate I), one directly over the mouth of each port ay a, and of about the same arca.

As shown in Fig. 1, while the port a is takin g steam the recess s will also be filled with live steam, or steam under expansion. As the valve makes its return stroke and comes to the position shown in Fig. 2, it will cut off steam from a', and also will confine a small quantity of live steam in the recess s', the effective downward pressure of which will nearly or exactly counterbalance the upward pressure of steam against the bottom of the valve through the port a. IIence the effect of back-pressure on the valvefoot will. be wholly eliminated, or, by lessening the area of the recess, partially so, as may be preferred. Also, by enlarging such recess and giving the top of the valve a greater lap thereon, a slight preponderance of downwardpressure can be secured, when desired. After the valve passes the recess, the steam confined therein goes to the exhaust. The same operation takes place at the other end of the valve on its return stroke, and so on alternately.

Vhile the balancing device thus described is sufficiently secure in its place, and, by its connections, to perform with certainty the objects sought, it is also so far free of bolts, clamps, or interloekin g parts as to adapt itself readily to all the varying conditions of use. 'For example, if it be necessary to reverse the engine while taking steam at either end, dan ger of accident will be materially lessened, from the fact that under the excessive pressure resulting therefrom the 'alve or balancin g-plate, or both, may lift or yield sufliciently to allow of enough leakage of steam to prevent explosion or other injury.

Other appliances, as usual with slide-valves, are to be added, such as valve-stem D', stufiing-box D2, and also other desired devices, not usual, may be added.

The terms top and bottom, upper7 and lower are used herein in a relative sense, so that I do not limit myself in the invention to a horizontally working valve arranged in a valve-chest on the upper side of a cylinder.

The object of rabbeting the edge of the bal ancing plate is, in part, to limit the possible upward movement of the plate, and partly to lessen the possible limit of its tilting motion, and at the same time render the construction more compact.

The slide-valve shown and described also diers from other valves in other respects of like construction, in that the steam is exhausted endwise between the cross-bars, which, as shown, constitute a part of the end extension.

I make no claim of exclusive right to anything vshown or described in either of the patents granted to John Baird, April 5, 1864, or George Rieseck, March 31, 1863.

In my improvement it will be observed that the end extension of a vertically-moving balancing-plate, in combination with the end extension of the valve, presents both novelty a-nd utility in a patentable sense, since the plate thereby better prevents the lifting of the end of the valve, while the balaliciiigeii'eet is still secured.

I claim herein as my invention- I'. The balancing-plate I, working like a piston, with a slight range of motion, through a hole in the top plate of the steam-chest, and with its lower surface underlying the edges of the hole in the top plate, in combination with a slide-valve having a bearing-extension at each end beyond the valve foot proper, whereby the balancing-plate, while free to perform its function as such, also bears on the whole, or nearly the whole, upper surface ol.' the valve when the latter is at the ends as well as at the middle of its stroke, substantially as set forth.

2. The balancing-plate I?, working in the top plate ofthe steam-chest, as described, and overlapping the end extensions of the valve, as described, and having a steam-port through or past the same, in combination with a flexible gasket to cover the joint of the balancingplate and cover, and also in combination with a valve having an open top and end extensions, substantially as set forth.

3. The balancing-plate I), having a slight vertical, but no longitudinal, lnotion, made with a hole through or past the same, and recesses s s in its lower face, immediately over the open ends or mouths of the cylinder-ports, in combination with the described valve and gasket, substantially as set forth.

4. The valve D, having the end extensions described, in combination with central steamport B, end exhaust-ports I3 B', and balancing-plate I), having end extensions, substantially as set forth.

5. A slide-valve having a bearing-extension at each end, which projects beyond the valve-foot proper, and having also an end opening through such extension for an endwise exhaust from the valve, substantially as set forth.

In testimony whereof I have hereunto set my hand.

JOHN C. BRYAN.

Witnesses:

J. J. McGonMicK, CLAuDiUs L. PARKER.

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