US475427A - Single-cylinder compound engine - Google Patents

Description

2 Sheets-Sheet v2.

(No Model.)

B. J.- WOOLF. SINGLE CYLINDER COMPOUND ENGINE.

THE NORRIS PKTERS co., PNOTU-LITHU., msnmawy, n. c

(No Model.) 2 Sheets-Sheet 1.

. E. J. WOOLF.

SINGLE CYLINDER COMPOUND ENGINE.

No. 475,427. Patented May 24, 1892.

UNITED STATES PATENT OFFICE.

ELLIS J. WOOLF, OF MINNEAPOLIS, MINNESOTA.

SINGLE-CYLINDER COMPOUND ENGINE.

SPECIFICATION forming part of Letters Patent No. 475,427, dated May 24, 1892.

Application filed July 14, 1891. Serial No. 399,491. (No model.)

To all whom it may concern.-

Be it known that I, ELLIS J. WOOLF, a citizen of the United States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Single-Cylinder Oompound Engines; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to compound engines, and has for its object to providea single-cylindercompound engine of increased efficiency.

To this end, as one feature of my invention, I so arrange the steam-passage and the valve that the opening of the port to the low-pressure end will be delayed for an interval after the exhaust begins on the high-pressure end at any desired cut-off in either motion without changing the dimensions of the valve, thus giving a longer period of expansion and allowing the stroke from the high-pressure end to be approximately completed before admission of steam to the low-pressure end, and accomplish this result without materially increasing the volume or decreasing the pressure in high-pressure end by non-efiective increased area. Undue preadmission at the low-pressure end is thus avoided and compression in the sameis correspondingly reduced. In my preferred construction for this purpose I locate the steam-passage in the valve itself, and construct the valve so that it has on the inner wall of the valve-cavity an outside lap equal to the outside lap on the valve proper when the valve is in its central position; or, in other words, I give the valve on the inner wall of the valve-cavity a lap, which will cover the low-pressure port for a considerable time after the exhaust begins from the high-pressure end into the valvecavity. I thereby obtain a delay or interval between the time of the beginning of the exhaust at the high-pressure end and the beginning of the opening of the port at the lowpressure end equal to the valve and piston travel required for the ordinary lap, and the pressure is reduced at the high-pressure end only by the small amount corresponding to the proportional additional area of the steam passage orcavity in the valve.

As another feature I provide at the highpressure end an excess of clearance or steam space, thereby obtaining an increased volume and pressure from the same when exhausted into the low-pressure end without increasing the piston area in the high -pressure end. This construction enables me to obtain equal effective pressures on both sides of the piston.

In my preferred construction this extra clearance or steam-space at the high-pressure end is obtained by providingasuitable chamber in the piston-rod, and to fill the same without interferencewith the action from the valvecontrolled port I provide a supplementary port from the steam-chest and provide openings to the clearance-chamber in the pistonrod, so arranged that they will be central with the supplementary port when the crank is on the center. This means of filling the clearance-chamber is very desirable, as the lead-opening at the valve-port would be insufficient to give boiler-pressure in the cy1 inder at the beginning of the stroke if the clearance be sufficient to give equal effective pressure on the opposite sides of piston. The supplementary port extends around the piston-rod, the end Wall of the cylinderbeing recessed for this purpose, and the lengths of the openings through the hollow piston-rod into the clearance-chamber is equal to the bridge-wall between the supplementary port and the cylinder proper. Hence when the piston is in motion the bridge-wall will cover the said openings and cut off admission through the said supplementary port.

Another feature is the combination, with the single-cylinder compound engine, of a valve-gear particularly designed to meet the requirements of such an engine. In such an engine it is very desirable to admit the steam to the low-pressure end for a longer time or greater length. of stroke than to the highpressure end, inasmuch as compression must begin in the high-pressure end coincidently with the cut-off at the low-pressure end. Hence the longer this cut-off at the low-pressure end can be delayed the better the results. The peculiar valve gear combined with this engine accomplishes this result in both motions, (forward and backward of the engine,) and the shorter the cut-off from the high-pressure end the greater is the propor tionate delay in the cut-off at the low-pressure end, which is the variation desired.

The accompanying drawings illustrate the invention, wherein like letters and figures refer to like parts throughout.

Figure 1 is a sectional elevation of an en-l gine embodying all the improvements hereinbefore specified except the supplementary. ports, the valve being shown at the point of= cut-0E on the high-pressure end. Fig.2 is a sectional elevation of the piston, cylinder," and valve identical with Fig. l, exceptthat the valve is shown at thepointof exhaust at the high-pressure end. Fig. 3 is a sectional elevation of the engine proper having the. supplementary port, the valve being shownatf the lead-opening on the high-pressure endu Fig. 4isa diagram illustrating the actions in bothmotions.

A is the cylinder; B, the piston; C, the; steam-chest; D, the valve; E, the valve-stem; F F, the piston-rod of the engine. a is the valve-controlled port at the high-pressure end a/,the corresponding port at the 1ow-pressureend; a,the outsideexhaust of the-usual construction. The valve E is provided with the steam-passage d, which is larger at the high-pressure than at the low-pressure end. The inner wall (1 of the valve-cavity or steam passage d is provided with outside lap, as shown at d", which when the valve is centralj is, as shown equal to the outside lap 11' on the valve proper. Thepiston-rod is hollow, as before stated, and is closed atits outer end. It is also provided with a partition divid 'ing the same into the'two parts 'F F The part F is provided with openings f for the admission of steamto its interior, and constitutes the extra'clearance or steam-space chamber, before noted. I

In the construction shown in Fig. 1 reliance is made on the high-pressure steamsport a to fill this clearancetahamber; butin the con-1 struction shown in Fig. '3 a supplementary port G from the steam-chest isprovided, passi'j ing down throughthebridge-wall and extendied around the piston passageway in the entlf wall of the cylinder, and the openings f inth' the clearance-chamber are located far enoughl back on the rod, so-as to be centralwith the, port G when the crank is on the center, as before stated. When the supplementary port; is employed, a packing-ring H islooated in a, suitable seat of the bridge-wall between the said port and the: cylinder proper. The piston-rod maybepacked bya s'tutfiug K of the, ordinary construction.

Provision is made by a duct L andsteam-f pipe L 'for the admission of live steam tothe interior of the valve at willlin case the same, should be necessary to start'the engine. Q isthepower'shaft driven from the crank:

:and connecting rod'in the usual way,the po-.

sitions of which are shown "by the lines ,q. and q. n a

R is the valve-driving eccentric power-shaft Q.

on the R is the eccentric-strap, which is provided with an extended arm R", the outer end of which is constrained to move in a definite path variable at will by a guide S, fixed to the end of a rock-shaft S. The engagement of the outer end of the arm R" with the said guide is preferably made by a roller R" T is the eccentric-rod, which extends directly from the arm R to the valve-stem; but, instead of being connected to the said arm in the center line of the said arms motion,isconnected to an offset-arm 0*, projecting from the rear of the same or in a direction away from the cylinder. The position of the guide .8 with reference to a vertical line determines the direction or the powershafts movement, and the intermediate positions or angle at which it stands with reference to the vertical in either motion determines the point of cut-olf and the other actions. The guide is rocked to reverse the power-shaft or vary theactions in any suitable way, as by the lever-arm Vand lever-rod V. This gear is in its general features identical with the gear patented to myself and John Peebles, of date July 30, 1889, under patent numbered 407,806, modified forms of which are also shown in'thepatent'issued to E. J. Woolf, of date January 13, 1891, numbered 444,563, andin the patent issued to E. J. Woolf and J ohn Peebles, of date July 14, 1891, No. 455,872, but difierstherefrom in the location of the ofiset arm or point with reference to the direction of the eccentric-rod. 'Inthe said prior patents and in all uses hitherto made of the said gearit was appliedto simple engines,.and in such usage direct connection froman offset-arm projecting away from the cylinder was not desirable. With'the single- .cylinder compound engine, however, this construction. gives the exact results desired, as before stated.

The diagram Fig. 4showsthe actions of this gearfforone revolution of the crank in both the'forward and'backward or under and over motion of the crank. Thisdiagram is drawn from exact scale, and all the parts are symmetrical throughout.

The eccentric is located opposite'the crank.

W represents the path of thepiston-rod pin, which of course corresponds to that of the piston in the cylinder.

W represents the path of the valve-stem pin, which corresponds to that of the valve.

X X represent thecenterline ofthe guide S in .the over motion of 'the crank,looking fromthe cylinder, and X. X the position of the same in the reverse or under motion of the crank.

Q represents the center of the power-shaft.

Y represents the path ofthe eccentric, and Y the path of the crank pin.

Z represents the path oflthe ofiset point of attachment or, pivotpin connecting the eccentric-rodito the ofisetarm 'r when'the guide S is set for theovermotion or in the line XX. The curve Z represents the path of the same point when the guide S is set for the under motion or in its reverse position in the line X X. The positions of the different points are represented by 1 1 in the under motion of the crank and by 2 and 2 in the over motion of the crank.

1 represents the point of cut-oft at the highpressure end and 1 at the low-pressure end, anc 2 and 2 the like points in the other motion. WVith this explanation the various positions can be readily traced on the diagram. An inspection of the path of the cross-head pin will show that the cut-offs 1 and 2' from the low-pressure end, corresponding to the cut-offs 1 and Z from the high-pressure end, are relatively late, the proportional distance being in the case shown about two to one.

It should be noted that the piston-rod is enlarged to reduce the effective area in the highpressure end of the cylinder.

What I claim, and desire to secure by Letters Patent of the United States, is as follows:

1. In a single-cylinder compound engine, a Valve provided with'a cavity for the passage of the steam from the high to the low pressure end of the cylinder and having on the inner wall of the valve-cavity a lap covering the low-pressure port for delaying admission to the low-pressure end after the exhaust begins from the high-pressure end into the valvecavity, substantially as described.

2. In a single-cylinder compound engine, a piston -rod recessed to constitute an extra clearance or steam-space chamberat the high-pressure end and provided with openings to the said chamber for the inlet and outlet of the steam, substantially as and for the purpose set forth.

3. In a single-cylinder compound engine, the combination, with the cylinder having an excess of clearance in the high-pressure endwithout increase of the piston area in the same, substantially as and for the purpose set forth, of a supplementary port from the steam-chest for filling the said extra clearance or steamspace chamber.

4. In a single-cylinder compound engine, the combination, with a piston-rod recessed to constitute an extra clearance or steam-space chamber at the high-pressure end and having openings to the said chamber, of a supplementary port from the steam-chest for filling the said chamber, substantially as described.

5. In a single-cylinder compound engine, the combination, with the piston-rod recessed to provide an extra clearance or steam-space chamber, of a supplementary port from the steam-chest and openings from said chamber through the wall of the piston-rod located at a point on the same back of the piston-head and so as to be central with the said port when the crank is on the center, anda packing-ring seated in the bridge-wall between the said port and the cylinder proper, substantially as and for the purpose set forth.

In testimony whereof I affix my signature in presence of two witnesses.

ELLIS J. WOOLF. lVitnesses:

J AS. F. WILLIAMsON, E. F. ELMORE.

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