US35070A - Improved link-motion for steam-engines - Google Patents

Description

UNITE@ STATES PATENT OFFICE.

JOHN F. ALLEN, OF NE\V YORK, N. Y.

IMPROVED LINK-MOTION FOR STEAM-ENGINES.

Specication forming part of Letters Patent No. 35,070, dated April 29, 1862.

To all whom t may concern:

Be it known that I, JOHN F. ALLEN, of New York, in the county and State of New York, have invented a new and useful Improvement in the Application of the Link-Motion to Steam-Engines, and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and to the characters of reference marked thereon.

The Stephenson, or, as it is sometimes termed, I-iowe, link-motion has heretofore generally been applied to steam-engines as a variable cut-off gear to give motion to one or two lap slide-valves, each of which performs the several offices of admitting, cutting olf, and releasing steam to and from the cylinder, and for points of cut off which correspond nearly with the end of the pistons stroke sueh application is effective, as the valve then receives a quality of motion which allows itfto perform all its said functions in a proper manner; but when the said link-motion in its application as aforesaid is so connected with the kind of valve specified as to cause the said valve to cut off the supply of steam atan early period of the pistons stroke, then the action of the valve in exhausting is suoli that effects arise prejudicial to economyin the use of steam, because excessive exhaust lead is produced at the acting end of the cylinder, while at the opposite ornon-acting end excessive cushioning occurs.

It is the object of my invention to produce a more favorable application of the link-motion, or an equivalent therefor, to the steamengine, so that it may effect a short cut-off, and shall also at the same time maintain a correct exhaust action; and to this end my said invention consists in the combination of a Stephenson link-motion, or an equivalent therefor, as hereinafter specified, with one or more steam or induction valves and one or more exhaust or eduction valves, (the said steamv'alves being separate and having different movements from the said exhaustvalves.) lVhen the exhaust-valves receive mot-ion from that lpart of the rocking lever termed the link, or its equivalent, which is best suited to give to them correct action, while the steam-valves are moved by any other part of the same link, which will cause them to effect a shorter cutoff than that part of the link would do by which the exhaustvalves are moved, substant-ially in the manner hereinafter set forth.

To enable others skilled in the art to male use of my invention, I will describe a mode of putting it into practice.

In the accompanying drawings, making part of this specification, Figure l shows a side elevation of a steam-engine with the cylinder and its appendages in section, illustrating my invention; and Fig. 2 shows a crosssection of the link f.

Similar characters of reference denote the same part in both the figures, in whichct is the main shaft of the engine, on which are secured two eecentrics, l) and c, which are connected, respectively, by their rods d and e with the upper and lower ends of the link f, which link is movably sustained at g by the rod h, which swings on the pivot t'.

rlhe combination of parts above referred to constitutes what is well known as the Stephenson link-motion, the vibratory rocking lever f being termed the link v The link j' is slotted or mortised through nearly from end to end. In this slot are held two sliding blocks, m and n, which can pass each other. (See Fig. 2.)

o is the steam-cylinder, which is shown in section with the steam-chest p and the exhaust chest or passage q.

fr and s are two sliding steam-valves, which, for the rear and front ends of the cylinder, respectively, serve to admit and to cutoff the supply of steam.

u and r are two sliding exhaust or eduction valves lying in chambers or cavities under the cylinder, each communicating with one of its ends, and these said exhaust-valves alternately op en communication between each end of the cylinder and the exhaust chest or passage q.

The exhaust-valves u and t are connected with and receive motion from the block m in the link f through the rod zu, the levers tu and tu?, and the rod w3, While the steam-valves fr and s are connected with and receive motion from the block n through the rod t, le vers t and t2, and the rod 3.

cc is the piston, y the connecting-rod, and 2 the main crank, of the engine, the two parts last mentioned being shown by red lines.

The eccentrics and all the parts which are above specified as constituting the link-motion may be proportioned and set as in customary practice, when applied in the ordinary manner. The curvature of the slot in the link f is that of a circular arc described, when the engine is on either center, from the end of the lever t2 as a center, with the rod t3 for a radius.

The steam-valves may be set with the same lap or cover as that of an ordinary cup slide-valve,which would be suitable for use with the described link-motion in its usual application, while the exhaust-valve I prefer to 4set without lap, or, in other words, so that thepone valve will commence to open when the other completes its close.'

I prefer to set the block m near the end of the link f, because that part of it will produce in the exhaust-valve (through the said o block m and the connections) movements which will open and close them at times as nearly coinciding with the terminations of the pistons strokes as may be desirable.

rlhe block n, from which t-he steam-valves derive their movements, may be set in any part of the link which will cause them to cut off steam at the desired point, and because the action of the steam-valves is Wholly independent of that of the exhaust-valves the eX- tent to which expansion may be advantageously carried will notbe limited on account of incorrect exhaust action being consequent upon a short cut-off.

The block m is made shifting, only so that it may be moved to the extreme opposite end of the link from that in which it is represented when it is desired to reverse the motion of the engine, in which case the block n must also be shifted into the lower half of the link. These said blocks may each be shifted by the means usually employed for a like purpose in ordinary applications of a stationary link. Then it is not desired to have the motion of the engine reversible, the exhaust-valves may derive movement from a pin fixed in asolid part of the link f, corresponding` with the face of the block m, while the block n may be movable in a slot occupying a portion of the upper half of the link only; but the steam- Valves may also be moved by a pin fixed in any part of the link, which will eifect cut off at any unalterable point.

I do not wish to be understood that my invention is limited to an application of the particular link-motion hereinabove specically described, as there are other means by which the vibratory rocking lever f may receive the peculiar movements which are imparted to it by the two eccentrics b and c-as, for example, a single eccentric applied in a manner which is the subj ect of an application for Letters Patent of the United States iiled by me simultaneously with the present, and entitled an improvement in the valve-gear of steamengines; and this last-mentioned improvement, which is a substitute for the Stephenson link-motion, I have particularly contemplated applying in the manner which is the subject of my invention herein described.

My invention is not limited to any particular mode of connecting the valves with the link.

I am aware that separate exhaust and steam valves have been adapted to the cylinders of steam-engines in the manner above described. I therefore disclaim as new separated steam and exhaust valves when these are operated by other means than by a single link-motion; but

What I claim as my invention, an d desire to secure by Letters Patent, is-

The combination of a single link-motion, or its equivalent, as hereinbefore specified,with one or more steam-valves and one or more exhaust-valves, the steam-valves having movements independent of and different from those of the exhaust-valves, When all the said valves receive their respective movements from the single link-motion aforesaid, substantially in the manner hereinbefore set forth, for the purpose specified.

In testimony whereof I have hereunto set my hand this 4th day of April, lSl.

JOHN F. ALLEN.

In presence of- HORACE ANDREWS, C. B. RICHARDS.

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