US252651A - Valve-gear for steaivi-engines - Google Patents

Description

(No Model.)

E. DUGAR.

VALVE GEAR PoR STEAMENGINES.

No. 252,651. l Patented Jan. 24,1882.

F'iEII.

ILO

i F f1 ai? Z J E to A N. PETERS. Pvwmmnugmpnu, wuhingxun, D4 C.

UNITED STATES trice.

areNr VALVE-GEAR FOR STEANLENGINES.

.SPECIFICATION forming part of Letters Patent No. 252,651, dated January 24, 1882. Application tiled November f2.3, 1881, (No model.)

To all whom dit may concern:

Be it known that l, EDELBERT DUGAR, ot' Somerville, county of Middlesex, State of Massachusetts, haveI invented an Improvementin Valve-GearforSteam-Engines, of which the following description, in connection with the accompanying drawings, is a specification.

My invention relates to a valve-gear for steam-engines', and has for its object to cause the valve to be opened more rapidly with relation to the movement of the piston than is the case with the valve-gears now commonly in use.`

The invention is shown embodied in an engine provided with an ordinary slide valve; and it consists essentially in the employment of multiplying gearing between the valve-operating crank or'eccentric andthe valve-stein, so arranged that when the said eccentric is having its most rapid effective movement, as when the piston is near the end of its stroke, the movement of the valve is still more rapid, it opening the port very quickly, while in the furthermovementofthe said eccentric the valve has no t'urther effective movement relative to the port until the piston nearly reaches the end ofits stroke, when the valve is again quickly thrown across its seat, closing one part and opening theother. As herein shown, the valvestem is connected to a wrist-pip mounted on a rocking shaft, provided with a pinion meshing with a segmental gear of larger diameter connected with and oscillated by,the eccentricrod, the said gear and pinion being so proportioned that the latter and the wrist-pin connected with the valve-stein oscillate back and forth for about three-quarters of a revolution, passing and repassing the dead-center relative to the valve-stem at the end of each oscillation, it then producing no effective movement ot' the valve, which is thrown across its seat in the movement of the said wrist-pin between the said deadcenters. The time occupied by the entire oscillation of the wristpin is the same as that occupied in ordinary valve-gears by the valve in shifting from one to the other position, while in the present arrangement the said valve is shifted byabout one-third ot' the said oscillating` movement, the said shifting taking place at the most rapid portion of the said movement, so that the rapidity ot' the effective movement of the valve relative to the stroke of the piston is greatly increased and wire-drawing of the steam at the tirst part of the stroke is wholly obviated.

Figure 1 is a side elevation of a steam-engine provided with my invention Fig. 2, an elevation thereof viewed from the other side, the cylinderand steam-chest being in vertical section; and Fig. 3, a diagram showing the relative positiousoi'thepartsatdifterent points in the stroke ot' the piston.

The main framework @,cylinderb, and steam-y chest c, the piston d, piston-rod c, connectingrodf, and crank g 'upon the main shaft h may he of any usual construction, the said steamchest heilig shown as provided with the usual live-steam ports leading to either end of the cylinder, and an exhaust-port between them, controlled by a slide-valve, t', such as commonly used.

The main shaft h is provided with a valveoperating eccentric, j, having the usual eccentric-strap 7c and rod l,- but instead ot' connecting the said rod with the valve-stem directly, or through the intervention of a simple lever, the said rod is connected with a segmental gear, n, mounted upon an arm, a, of a bracket, a', on the frame a, which meshes with a pinion', n', on a shaft, lo, mounted on the bracket a',

and provided with a wristplate,p, having a wristpin, r, connected with the valve-steam m in any usual manner.

It will be readily understood that the segmental gear a will pe oscillated backward and forward by the eccentricj, its movements being in precisely the same relation to those ofthe piston d in its stroke as those of the ordinary slide-valve when having direct connection with the eccentric, which is mounted with its throw in such relation to the crank g that the eccentric produces the most rapid movement of the gear n while the crank g is passing the deadcenter, the. piston d being at the end of its stroke and almost stationary in the position shown in Figs. 1 and 2. rlhe pinion a is so proportioned rela-tive to the gear a that in the oscillating movement ofthe said gear the wristplate p rotates backward and forward for considerably over halfa revolution, the movement ofthe wrist-pin r being that shown by the dotted are, Fig. 2, limited by the arrow-heads shown at the ends ofthe said are, All that portion.

of the movement of the wrist-pin r over the TOO haltrevolution, or that shown below the horizontal dotted line x, Fig. 2, produces no effective movement ofthe valve relative to thatpart, the edge of the valve th uslying wholly beyond the port-opening, and it is not until after the wrist-pin has moved an equal distance above the said line or that the edge ofthe valve reaches the edge of the port-opening and begins to travel over it, the whole effective movement ot' the valve being' made while the wrist-pin r is traveling from a point above the line at' on the one side to a corresponding point above theline .r on the other side of the wrist-plate, it being shown in Fig. 2 at the middle of its effective movement.

In the diagram, Fig. 3, the are g represents the path of the crank-pin during one stroke of the pistou, the said are being divided into four equal parts,thepointsot` divisionbeingmarked l to 5, respectively. The arcj represents the path of the center ofthe eccentric, it being divided and marked to correspond with the arc f/ The numbered points at a represent the positions assumed by the pivotal connection of the eccentric-rod l with the gear u, and the arc at r represents the corresponding position of the wrist-pin r, while the positions of the edge of the valveand piston are marked oli' att'and d.

It will be seen, ref'erring to the diagram, that in the first quarter of the movement of the crank-wiz., from l to 2-the valve is wholly opened and carried beyond the portopeniug, which was in reality fully opened during about the first half ofthe movement from l to 2; that in the next two fourths of the movement of ,the crank-viz., from 2 to 4--the valve merely plays back and forth slightly upon its seat, without, however, at all covering the port-opening or affecting the flow of steam therethrough, and that during' the last fourth ot' the revolution, or from 4 to 5, the valve wholly closes the port that has been receiving steam and opens the port leading to the other end ot' the-cylinder.

It will be seen that the points 3 4 ofthe position of the valve coincide, or, in other words, while the crank is passing from 2 to '1t the valve moves back a, little toward 1 to the point marked 3, then forward again as far as 2, when it begins its continuous backward movement through 4 to 5. In other words, the continuous movement of the valve from one to the other extreme position, instead of occupying the time of a whole stroke ot' the piston, as is usually the case, only occupies the time of a portion ofthe said stroke.

It will be understood that the movement of the valve 4across its seat in controlling the ports is more rapid relative to the movement of the piston than in the ordinary gearing, where there is a direct connection from valve to its eccentric in the ratio of thcgearnto the pinion n', and that the valve is open to its fullest extent almost at the very beginning of the stroke of the piston, so that the falling ot' the pressure ot' the steam in the cylinder' during the first part ofthe stroke by wire-drawing between the edge of the poltand that of the valve-a thing which has proved a serious detriment to engines ot' certain classes using the ordinary gearing-is wholly obviated.

l claim- 1. In a valve-gear for steam-engines, the valve and its stem and actuating eccentric, combined with mnltililying connecting mechanism between the said eccentric and valvestem, arranged as described, whereby the effective movement of the valve across its seat is more rapid than that derived directly from the eccentric, and the valve has no effective movement during a portion of the moveiuentof the said eccentric, substantially as and for the purpose set forth.

2. The combination of the eccentricand rod and gear connected therewith, to be oscillated thereby, with the pinion and wiist-pin and valve-stem connected therewith, the said pin- .ion and gear being properly proportioned t0 cause the wrist-pin to oscillate in an arc greater than halt' a circle, whereby the movement of the valve from one to the other eXtreme position occupies less time than the stroke of'the piston, substantially as and for the purpose described.

In testimony wherroflhave signed my name to this specification in the presence of two subscribing' witnesses.

EDELnnl-:T DUGAR.

Witnesses:

Jos. VP. LIVERMORF., W. H. SrGs'roN.

Images