US21668A - Gearing of ctjt-off valves for steam-engines - Google Patents

Description

' vention, we will proceed to describe its oon- UNITED STATES PATENT OFFICE.

P. W. GATES, D. R. FRASER, AND THOMAS CI-IALMERS, OF CHICAGO, ILLINOIS.

GEARING OF CUT-OFF VALVES FOR STEAM-ENGINES.

Specification of Letters Patent No. 21,668, dated October 5, 1858.

T 0 aZZ whom t may concern:

Be it known that we, P. W. GATES, D. R. FRASER, and THOMAS CHALMERS, all of i Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Variable-Cut-Oif Gear for Steam-Engines; and we do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming part of this specification, in which- Figure l, is a longitudinal central section of part of the cylinder and valve-chest of a horizontal steam-engine, exhibiting the application of our improvement. Fig. 2, is a plan of all the parts below the line w, in Fig. l.

Similar letters of reference indicate corresponding parts in both figures.

This invention consists in certain improved mechanism for operating two cut-off valves which are applied to the back of a slide valve which eHects the induction and eduction of steam to and from an engine and which is capable of liberating the said cut-o valves at such point in the stroke of the engine-piston as may be determined by the operation of a governor or by a permanent adjustment as to allow them to be closed instantaneously to cut off the steam from the cylinder, either by the pressure of steam in the valve-chest or by other suitable means.

To enable others to make and use our instruction and operation.

A, is the cylinder; B, is the valve chest.

a, a, are the steam ports, and Z7, the eX- haust port of the cylinder.

'C, is the main slide valve of the kind known as the short slide, having two passages c, c, through it of a size to correspond with the ports a, a', and the usual exhaust cavity CZ, in its face. This valve has two stems e, e, one at each end, which pass through the ends of the valve chest and are packed by stuffing boxes f, f, therein and it may be operated by an eccentric or in any other well-known manner.

D, D, are the two cut-off valves consisting of solid plates fitted to slide on the back of the valve and provided with separate stems g, g, passing through stuffing boXes L, h',

in the ends of the valve chest. These are furnished outside the valve chest with crossheads i, z", which work on fixed guide rods j, j, and j, y, and which carry two pawls c, 7c', one each, which pawls are capable of engaging respectively in notches Z, Z, in two blocks m, m, attached to the stems e, e', of the main valve. The said pawls have springs fn, a, applied to force them into the notches as they arrive over them, and through their aid the cut-oft' valves are caused to be moved by and along with the main valve.

p, p, are two metal slides, fitted to slide in grooves g, g', in the tops of the heads m, m', and under the pawls 7c, c, for the purpose of throwing said awls out of the notches to allow the cut-o valves to be moved by the pressure of steam to proper positions to cut off the steam from the ports a, a', by the pressure of steam from in the steam-chest acting opposite to their stems g, g. These two slides pass freely through the crossheads i, z", and are connected rigidly with two toothed rack bars r, r, which work in guides s, s', on the top of the steam-chest and which gear on opposite sides of a pinion t, on a shaft u, which works in suitable bearings in a stand E, ereceted above the valve-chest. This shaft u, when turned, moves the rackbars in opposite directions and serves to adjust the two slides p, p', to throw out the pawls Z0, 7c', from the notches Z, Z, and thus disconnect the cut-off valves from the main valve earlier or later in the stroke of the piston. The said shaft might be adjusted by hand to cut olf at any point in the stroke that may be desired, but I have represented it and prefer to use it in connection with a governor, and to this end I employ upon it another pinion t', or extend the same pinion t, to a sufficient length to gear with a toothed rack o, on the regulating rod fw, of the governor Gr. The stand E, which contains the bearings of the shaft u, also serves to support the governor. y, y, are stops attached to the guide rods j, j, for the purpose of arresting t-he crossheads of the cut-off valves and thereby stopping the said valves in proper' position for the pawls c, Za', to take hold of them as the main valve completes its stroke. These stops y, y, and y, y', are made hollow to contain india-rubber cushions and the cross-heads are furnished with piston-like projections 0, 0, and o', 0', to come in Contact with the rubber cushions to prevent violent concussions when the valves are thus arrested. The heads m, m', of the main valve stems are also provided with cavities Z, Z, (Fig. l) at the backs of which are india-rubber cushions 3, 3*, against which strike the ends of piston-like projections 4, 4*, on the crossheads z', z', to stop the cutoff valves in positions to close the ports 0, c', when they return after their pawls have been liberated .from the main valve stem.

To illustrate more fully the operation of the cut-oi:l gear, I will first suppose the slide valve to be in the position shown in Figfl, moving to the right hand as indicated by the arrow on one of its stems. It will be seen that the cut-off valve D is l locked to the main valve by its pawl 7c, in a position to leave the port c, open, and the other valve D', is free of the main valve C, and supposed to be stopped by the stops y', y', shown in Fig. 2 and the passage c', of the main valve. is being uncovered by the movement of C. Steam is being admitted to the cylinder through c, a, and exhausted through a', d. The pawl la, of the valve D, is just being brought by the simultaneous movement of the valves C, D, into Contact with the slide p, and about to be raised out of the notch Z; and as soon as this takes place, the valve D, will be instantaneously driven by the pressure of the steam opposite its rod, over the passage c, and the steam is thus cut cttl from the port a, during the ref mainder of the stroke of the main valve C. As the main valve C completes its stroke, the notch Z', coming under the pawl le, connects the cut-off valve D', and locks it so that the passage c', will remain open during its return stroke till the pawl Z0', is disengaged by coming in contact with the slide p'. During so much of the return stroke of the valve C, as leaves the passage c, in communication with the port (Z, t-he said passage remains covered by the valve D; but the movement of the valve C being continued beyond the point where it closes the port a, the valve D is stopped by the stops y, and the so-continued movement of the valve C, uncovers the top of the passage c, and

brings the notch Z, in the head m, of the stem e, under the pawl 7c, which then drops in and locks it.. The disengagement of the pawl c-, as above mentioned allows the steam to act upon the valve D', to make it cover 50 the passage 0', in the same manner that the disengagement of the pawl Ze, caused the valve D to close the passage c, as before described. In this way the operation proceeds; the operation of the cut-off valves being the reverse in the opposite strokes of the main valve. As the governor rises, t-he slides p, p', are moved apart; and as it falls they are drawn toward each other; in the rst case causing the cut-oli' valves to be liberated and allowed to cover ,the ports 0, c', earlier, and in the latter case later, in the stroke of the piston. Or the shaft u, may be adjusted by hand, and set to cut olf permanently at such point in the stroke as may be desired.k The same mechanism may be used with two cut-ofi valves applied each to one of twov separate main valves, the said main valves being arranged near the ends of the cylinder in separate steam chests or in the same one, both of which arrangements are well known; or it may be used in combination with two cut-otf valves working onv a stationary partition plate which separates them from the main valves.

What we'claim as our invention, and desire'tosecure by Letters-Patent, is

Vorking the cut-olip valves D, D', in combination with a main slide valve C or separate main slide valves of the character described, by means of the pawls 7c, lc', to lock the cut-oiil valves with the main valve or valves in an open condition, the variable or adjustable slides p, 29', to disengage the said pawls, the stops 3, 3*, to stop the said cutoff, valves in a closed condition after their liberation, vand stops y, y, y', y', to stop and o-pen them by the completion of the stroke of t-he main valve or valves; the whole operating substantially as described. 90

P. W. GATES.

D. R. FRASER. THOMAS CI-IALMERS. Witnesses:

I. L. FARGO, A. Gr. WARNER.

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