US417653A - Steam-engine - Google Patents

Description

Nq Model.) J NWOOD.

STEAM ENGINE.

No. 417,653. Patented Dec. 17, 1889.

llllllllllll'lllllllllll! N. PETERS Phcw'uflmgrlpher, Washington. D4 Cv UNITED STATES PATENT OFFICE.

JAMES B. STANWOOD, or CINCINNATI, OHIO.

STEAM-ENGI'N E.

SPECIFICATION forming part of Letters Patent No. 417,653, dated December 17, 1889. Applicationfiled March 18, 1889. Serial No. 303,809. lNomodel.)

To all whom it may concern:

Be it known that 1, JAMES B. STANWOOD, a

a citizen of the United States, residing at Cincinnati, Ohio,have invented new and useful Improvements in Steam-Engines, of which thefollowing is a specification.

My inventionrelates to reciprocating steamengines, having reference principally to that class usuallyknown as the Corliss type, in which separate steam induction and ecluction valves are operated byan eccentric and what 7 is commonl termed releasin ear controlled by a governor for cutting off the supply of steam at a given portion of the stroke of the piston, as requiredto maintain a uniform rotative speed of the crank-shaft under varying conditionsof load. The constructive conditions (as I shall explain more in dethe beginning of compression and governed by the piston itself .asa slide-valve, and the combination of the same with the usual induction and eduction valves and a single eccentric and releasing-gear.

Further objects of the invention are to securea greater amount of cushion than certain valve-gears are capable of giving; also, to assist in giving greater exhaust-area for exhausting the steam from cylinder than can be otherwise obtained without special complication.

My invention is illustrated in the accompanying drawings, in which Figures 1, 2, and 3 are longitudinal axial sections of a steam-engine cylinder constructed according to my improvement, with diagram showing the crank, eccentric, and releasinggear positions corresponding with the several piston and valve positions; and Fig. 4, a diagram indicating the several angular positions of the crank and valve motion plotted upon and in a common circle; and Fig. 5 is a cylinder embodying the same principles of con struction, but with a difierent type of valve.

Before referring specifically to the drawings a few words of general explanation in connection with one class of valve-gears will assist in defining my invention, as hereinafter described more in detail.

In steam-engines with adjustable cut-offs of (what may be generally called) the Corliss type one most distinguishing feature is the combination of a governor with whatis technically known as a releasing gear. This-combination automatically regulates the supply of steam at each stroke of the engine by measuring off a sufficient amount to perform the necessary work and maintain-a constant rotative speed of the crank-shaft. The releasing-gear (duplicated for forward and back piston motion) is placed in the valve mechanism at a suitable position between the driving-eccentric and the steam-induction valves, and embodies a latch or.some equivalent mechanism, which, coming in contact with a lug or stop adjusted as to position by the governor, breaks the connection between steam-induction valve and driving mechanism, allowing the former to be closed by some outside source of stored energy, such as a spring, weight, or vacuum embodied in an instrument known as the F, dash-pot. The releasing-gear can only act while the valve is opening, (either before or after the actual uncovering of the steam-induction port is accomplished.) as at this time only the latch is moving toward the disengaging lug or stop operated by governor. In practice the release of steam-induction valve occurs only after it uncovers the port and before its maximum open position. It is between these points that the cut-off takes place. When, as is the custom in a majority of cases, the driving-eccentric controls not only the steam-induction valves, but also the steam-eduction valves, this peried of cut off is limited by the position the eccentric has to take relative to the crank. The eccentric under these conditions has three functions-namely, first, to admit steam through steam-induction valves at the right instant behind the piston as it begins its stroke; second, to open the steam-. eduction valves to exhaust the steam when the piston is near the end of its stroke, and, third, to close steam-eduction valves at proper point to give the necessary compression to steam left in cylinder when piston is returning to its original position. These points are known, respectively, as points of lead, of release, and of compression. The position of the eccentric to regulate practically these three points must be at some angular position on crank-shaft greater than ninety degrees ahead of the crank in the rotative direction toward which the shaft is turning, except when a rocker reversing the motion of the valve-gear is employed. This angle in excess of ninety degrees is termed the angular advance.

The period, as before stated, during which cutoff can take place is between point of opening of steam-induction valve (the point of lead) and the maximum opening of same valve, the eccentric positions corresponding in time are the point of lead and maximum travel of same eccentric beyond this point. Now, as the eccentric is located on shaft at a greater angular position than ninety degrees ahead of crank, and as crank is nearly on center or at its dead-point when steam-induction valve and eccentric are at their respective points of lead, it follows that the period during which cut off can take place must be limited to crank positions corresponding to eccentric positions of point of lead and maximum travel. The limiting eccentric angle of this period is an angle equal to the difference between an angle greater than ninety degrees beyond deadpoint and an angle one hundred and eighty degrees beyond same dead-point, or to a limiting angle equal to one hundred and eighty degrees, less ninety degrees, plus the angular advance, which is equivalent to an angle less than ninety degrees, and therefore the corresponding limiting crank angle between which cut off can act is an angle less than ninety degrees from dead-point. In practice the corresponding piston position between which cut off can act is between zero and about four-tenths of a stroke.

The invention which I am about to describe is embodied in a cylinder so constructed in combination with separate steam induction and eduction ports operated by a single eccentric as that one of the functions of the eccentric-via, the closing of the steameduction valve-is performed by the piston of the engine, relieving the eccentric of this duty, and thereby allowing the period of cut off to be extended from four-tenths stroke to ,an extent greater even than six-tenths of called a negative angular. advance. This increases the limiting eccentric angle during which cut off takes place to ninety degrees, plus the angular advance, (now negative,) instead of, as above, ninety degrees, minus the angular advance, (positive) In my invention the eccentric has two functions only, the controlling of the point of lead and point of release, and this can be done with an eccentric, as above, with negative angular advance, as is shown by the figures.

In the illustrations given in the drawings, A designates the steam-cylinder; B, its reciprocating piston-head a a, the steam-induction valves controlling the induction-ports from the steam-chamber E, and I) Z) the'eduction or exhaust valves controlling the eduction-ports from the cylinder to the exhaustchamber F. The induction-ports are located in the extreme ends of the cylinder,- as is usual; but I locate the eduction-ports (designated at w in) somewhat toward the center or mid-stroke of the piston, and construct them and the piston-head in such manner as that the piston-head may pass overand govern said ports as a valve. It will be obvious that if the ports are located sufficiently within the extreme limits of the piston-stroke the piston-head in passingsov'er and beyond said ports will compress the residual steam in the cylinder, thus cushioning itself upon the imprisoned steam. The exact location of the ports will therefore be determined by the designer or builder of the engine to produce the desired compression, such being one of the objects of this departure from the usual construction. The compression being thus provided for independently, the valve-moving mechanism and exhaust-valves are entirely relieved of this function, and the relative period of time within which the exhaust-valve is to close is extended to that point in the return-stroke of the piston when it is about to uncover the exhaustrport, thus allowing eccentric position 0 to be adjusted at a smaller angle in advance of crank O. For example, in Fig. 1 the piston B is traveling to the left near the close of the stroke and has just covered the exhaust-port at. The steam-eduction valve b remains still wide open into exhaust-chamber F, and is not fully closed until just before piston-head B has returned to the same position, as shown in Fig. Had the duty of closing valve 1) been performed by the eccentric, it would have been necessary to locate eccentric on crank-shaft at an angle ahead of crank in direction of rotation greater than V O Y, Fig. l, 2, or 3, so that valve bcould have been closed earlier. This angle would be found in practice greater than ninety degrees. The angular period during which cut cit can act is represented by angle V 0 Z, Fig. 2, greater than ninety degrees. Had V O Y been greater than ninety degrees, V 0 Z or angular period during which out 01f could act would be less than ninety degrees.

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It should now be obvious that the limiting crank and eccentric angles at which a single eccentric-valve mechanism with releasinggear can be set in relation to the crank to control cut off are materially enlarged by this construction of cylinder. Again, in Fig. 1

' the piston B is traveling to the left near the close of its stroke, and has just covered the exhaust-port m. Now,'by proportioning the pistonof suitable thickness a primary exhaust can be effected through this same port a: by the uncovering of this port by the op- ,posite side of the piston, and this can be made to take place before the usual opening of the exhaust-valve b",whichonly should be well open before port 00 is reclosed by piston on its return-stroke. The exact thickness of piston will therefore be determined by the use, all, however, embodying substantially i and valve.

designer or builder of the engine to produce the desired exhaust or release of steam from the cylinder, such being also an object of thisdeparture from the usual construction. It will thus be seen that each exhaust port and valve can take added function-to wit, of

aiding inthe opening of the exhaust, which in the ordinary construction of steam-engine cylinders is taken wholly by the oppositeport In other words, the exhaust port and valve, which at a given time in ordinary practice remain wholly closed, may remain open to receive the preliminary portion of the opposite side exhaust.

In the drawings I'can only illustrate the releasing-gear diagrammatically, since several different forms of mechanism are in common the same principle-and all adapted to the purposes of my invention. The general principle of their construction I have already adverted to, and in thedrawings I have exhibited in the form of the diagram in dotted lines the position of the valve-levers with plate and connections, as related to the eccentric position 0 and main crank 0. As the constructive details of i this mechanism apart from the described construction of the cylinder and piston form no part of my'present invention, I am advised that-no further specific description is necessary, and therefore omit the same.

The advantages of this system are that with exactly the same mechanism as has heretofore been employed, first, an extended field for operation of cut off is obtained, increasing the cylinder capacity nearly fifty per cent. more than was heretofore possiblea feature of great value where compounding is necessary; second,the facility with which ample compression is obtaineda point in engines of certain types which has to be sacrificed when greatest range of cut oif is required, and, third, the ease with-which a double release-area is obtained by the uncovering of exhaust-port at one'end of cylinder when piston is at one end of stroke in addition to the usual port-opening by the usual valve.

The diagram Fig. 4 indicates a method of necessary that S, the point of compression brought about by piston covering exhaustport in cylinder, should be so taken that a vertical line drawn through S cuts the circular path of eccentrics motion between M and T, as at N. This insures the. inclosure of the exhaust-port by steam-eduction valve before same port is uncovered by the piston.

In Fig. 5 I have exhibited the application of the principle of my invention to a slidevalve engine. In such case the induction and eduction ports of the cylinder are formed at the same side and open through a common valve seat upon which rides a gridironvalve furnished with a rider or cut-off valve, by which the admission-ports are ultimately controlled.

I claim as my invention and desire to secure by Letters Patent of the United States 1. In a reciprocating steam-engine, the combination of a crank-shaft, a cylinder, two exhaust ports opening from said cylinder, one near each end within the reciprocatory limit of the piston-stroke, a piston adapted to pass over said ports as a valve, and valves governing said ports independently of the piston, substantially as set forth.

2. In a reciprocating steam-engine, the combination of a crank-shaft, a cylinder, two exhaust-ports opening from said cylinder, one

near each end within the reciprocatory limits of the piston-stroke, a piston adapted to pass over said ports as a valve, valves governing said ports independently of the piston, and a single valve-operating connection with the crank-shaft for controlling the induction and eduction of steam to said cylinder, substantially as set forth.

3: In a reciprocating steam-engine, the combination of the following instrumentalities, viz: a crank-shaft, a cylinder having its exhaust-ports opening therefrom near each end within the reciprocatory limits of the pistonstroke, a piston operating in said cylinder and across said exhaust-ports as a valve, separate induction and eduction valves, the latter c011- trolling said exhaust-ports independently of the piston, and a single valve-operating connection with the shaft for operating both sets of valves, substantially as set forth.

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In testimony whereof I have hereunto set JAMES B. STANWOOD.

Witnesses: L. M. HOSEA, E. L. KERR. V

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