US741388A - Steam or similar engine. - Google Patents

Description

PATENTED OCT. 13, 1903.

E. THOMSON. I STEAM OR SIMILAR ENGINE.

APPLIUATION FILED APR. 3. 398.

2 SHEETS-SHBBT 1.

N0 MODEL.

7m: NORRIS PETERS c0, Puo'm-umo, WASHANOTGN, n. c

PATENTED OCT. 13, 1903.

E. THOMSON. STEAM 0B. SIMILAR ENGINE.

APPLIUATION FILED APR. 13, 1898.

2 SHEETS-SHEET 2.

I 1 1 58. '2 E55E5 sit THE NORMS warns COv. FHOYO-LITHO,, WASWNGTON, n. c,

iro. 741,388.

ll ITE Snares Patented October 13, 1903.

amsnr rrrcn.

ELIHU THOMSON, OF SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

STEAM OR SIMILAR ENGINE.

SPECIFICATION formingpart of Letters Patent No. 741,388, dated October 13, 1903.

Application filed April 18, 1898. Serial No. 677,449. (No model.)

To all whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States, residing at Swampscott, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in Steam or Similar Engines, of which the following is a specification.

The chief object of my invention has been to improve the construction and operation of engines to be used with steam, superheated or not, compressed air, or other gases, so as to obtain from an engine of simple construction economical results in the use of steam, &c.,

which will be comparable with the results ordinarily obtained from complex engines, such as ordinary compoundor compound condensing engines. I have found in the practice of my invention that engines of as small a capac- 2o ity as from one to three horsepower may when constructed and operated according to my invention yield results in the economy of steam which, so far as I am aware, have been entirely unknown hitherto and which approach or equal the economies obtained by complex types of engines of the compound or triple compound class of much larger capacity and which far exceed the economical results of the complex forms of engines of 0 the same capacity, and I am thus enabled to do away with complex valve mechanisms, transfer-passages for steam, multiple cylinders of varying diameter, doc.

The principle upon which my improved 5 engine is founded is substantially as follows: I provide a large clearance-space back of the piston which by the instant opening of the valve when the crank is on the dead-point and the piston down is filled almost instan- 0 taneously with steam up to boiler-pressure. This steam or compressed gas is expanded rapidly during the motion of the piston forward and the supply cut off very soon after the crank passes the dead-point. In this 5 manner there is an almost instantaneous filling of the clearance-space with steam, which is almost immediately shut 0% before the piston has moved through any great angle, so that the work of the engine depends almost altogether upon the expansion of the steam admitted to the clearance-space.

As the piston moves forward and the steam expands the power is given to the crank almost entirely by expansion of the charge admitted, and lastly the steam is discharged through a proper exhaust-port, which may be of any desired construction, but which as I have shown it is of the simplest possible characterviz., a set of openings uncovered by the piston at its extreme outward stroke. The steam left in the cylinder as the piston returns is compressed into the clearance-space, giving an amount of compression depending upon the ratio between the volume of the clearance-space and the clearance-space plus the space traversed by the piston. This compression-pressure will generally be a fraction of the boiler-pressure. Thus it may be fifty pounds above atmosphere while the boilerpressure is one hundred and fifty or more. I

My construction insures the separation of temperatures, inasmuch as at no time does the steam reverse its progress or direction of movement in the cylinder between admission and exhaust. The admission end of the cylinder therefore can remain at the temperature of the steam of admission, while the exhaust portion of the cylinder is at a low temperature-that of the steam cooled by expansion in the abstraction of work in moving the piston. In the same way there is no possibility of condensed water or the cooled products after expansion being thrown back upon the hot end or admission end except what is demanded for compression, in itself a heating process. The cylinder at the end of each power-stroke is cleared of cooled and condensed products, such as condensed water. The exhaust-ports being situated as far as possible from the inlet-ports they do not 0 share each others temperature. It is to these and other features of construction to be pointed out to which I attribute the high economies of steam which I have obtained for small-powered and simple engines.

I am enabled by simple means to obtain a compound effect, and so further increase to a certain degree the economy.

My invention relates chiefly, therefore, to engines of simple character whereby the efzoo fects of expansion and compounding-are obtained without the necessity for the complexity of compound engines. The usual expedients of non-conducting lagging or steam-jacketing may be resorted to to protect the cylinders from external cooling. I find, however, that any plain non-conducting lagging is generally suflicient.

Figures 1 and 2 are plan and elevation, respectively, of a compound engine embodying the features of my invention. Figs. 3, 4, 5, 6, and 7 are diagrammatic views of the parts of the engine shown in Figs. 1 and 2. Fig. 8 is a modification in the manner of operating the admission-valve.

Referring first to Figs. 1 and 2, two pistons (which may be of different sizes) P and P are provided with suitable cranks set relatively to each other, so that piston P leads piston P in revolution by, say, ninety degrees up to one hundred and twenty degrees,

as may be selected. Admission to cylinder 0, which may be called the high-pressure cylinder, is made into a large clearance-space or untraversed space at the back when piston P is down. The valve V is shut soon after the crank to piston P passes the deadcenter. The steam in expanding pushes piston P forward and uncovers port E, which admits equalization of pressures between the two cylinders O and 0 back of their pistons. This occurs, preferably, at a point some fifty degrees or sixty degrees of revolution of the crank of piston P before reaching the outer dead-center. The steam from C then follows piston P outwardly, while piston P returns, covers exhaust-port E, and compresses what steam remains in cylinder Oafter such covering of E preparatory to receipt of new steam through valve V into the clearancespace. In cylinder C there need be but little clearance-space. The steam taken over from cylinder 0 goes on expanding in C until piston P is fully out. i

It will be seen that no exhaust-valve is provided for the low-pressure cylinder, the exhaust being controlled by the motions of the pistons themselves. This greatly simplifies the construction and leaves only a single valve V to be operated for a compound ongine. The construction is as follows: The communicating ports E for transferring the steam from cylinder 0 to cylinder 0 are arranged so as to be uncovered not only at the extreme outward stroke of piston P, but also for a similar period. on the extreme inner stroke of said piston, the said piston P being made short enoughto permit this. There are also provided exhaust-openings E, which are uncoveredby piston P at its extreme outer position, as shown in Fig. 1.

The operation will be better understood by reference to Figs. 3, 4, 5, 6, and 7, which are simply diagrammatic views of the parts in the engine of Figs. 1 and 2 at different times of revolution. In Fig. 3 the admission steamvalve V is open and the clearance-space back of piston P is filling with steam, while the crank corresponding thereto is just at deadcenter or a little beyond. Meanwhile since the crank moved by piston P follows crank of piston P at right angles, or thereabout, piston P is at its most rapid rate of motion inward and is discharging steam through port E, which has been uncovered by piston P in its backward stroke. Valve V closes and piston P moves forward, as in Fig. 4, but before reaching the center communicates with cylinder C through port E just as piston P begins its forward motion, as indicated. Both pistons are moving forward in this case with the port E open between them and steam passing from cylinder 0 to cylinder 0 This is continued, as in Fig. 5, while the crank of piston P is passing over its outward deadcenter, piston P making its elfective forward stroke meanwhile. Finally port E, which remained open, is closed by the backward motion of piston P, as in Fig. 5, and piston P I l is ready to open exhaust-port E and so drop the pressure back of piston P to atmosphere or below when condensers are employed.

Fig. 6 shows piston P nearly completing its backward strokeand'opening port E to the atmosphere or condenser from cylinderspace in 0 while piston P has started back ready to expel what remains in cylinder G through port E to atmosphere or condenser. This expulsion goes on through stage Fig. 3 while valve V is open and is completed in the stage (shown in Fig. 7) intermediate between that of Fig. 3 and Fig. 4, where piston P has begun its outward stroke and piston P is just about completing its inward stroke. Piston P is shown as justhaving covered the port E in its outward stroke in Fig. 7, while piston P now on further motion compresses what slight amount of steam remains into its own clearance -space, which is preferably made only slight, as above stated. I am thus enabled to secure the effects of compounding in a simple type of construction of engine.

Where the initial movements of the piston in my engine are given by extraneous power, as by turning over the crank at the start, I may dispense with mechanism for operating the valve V even and cause the piston itself to work the valve, it being only necessary that the valve V shall open for a short interval while piston P is nearly at rest on the inner dead-point. In Fig. 8, Ois the cylinder, as before, P the piston, and V is avalve the stem of which projects inward toward the piston, so as to be struck by the piston and opened for a short interval as the piston is almost down orwhile the crank is passing the dead-center. This admits steam to the clearance space S while said crank is on dead-center and fora very short interval before and after that point is reached. The opening of valve V thus becomes automatic, and the steam is exhausted at port E, as before. This arrangement is useful where the engine is to run at a determined speed once having been started, as in driving dynamos for electric lighting. To lessen the blow of the piston in opening valve V in running at good speed, the ends of piston P may be bored out into a small cylindrical cavity and a disk or piston inserted therein which engages with the valve-stem. A small amount of fluid in the space so provided between the small piston or valve-operating piston and the large piston proper acts to damp the blow struck on the valve-stem. A spring Q may also be provided, holding back the small piston 12 to a definite position when not engaged with the valve-stem.

In describing the engine of my invention no means of governing the speed'have been described or shown, it being understood that various means of governing may be employed where itis necessary that the engine shall be given a regular speed. Thus centrifugal throttie governors may be used to throttle the steam, or the engine may be governed on the hit-and-miss principle, as with gas-enginesthat is, the valve which admits steam may be caused bythe governor to intermit in its opening when it tends to be accelerated beyond normal speed-and this intermission may be put under the control of centrifugal or other governors similar to those used in gas engines.

With simple engines of as low as three to five horse-power constructed substantially as in Figs. 1 and 2, giving a compression of about fifty pounds and with a boiler-pressure of two hundred pounds dry steam, a brake horse-power can be expected to be obtained with an expenditure of about twenty pounds per horse-power hour, the speed of the engine being between six hundred and seven hundred revolutions per minute. Considerably better results can be obtained with larger engines, while my invention secures also a relatively high light-load efficiency as compared with complex forms of compound engines.

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

1. In a compound engine, the combination of a high-pressure cylinder; a low-pressure cylinder; ports in the high-pressure cylinder which admit steam to the low-pressure cylinder when uncovered by the forward move ment of the piston, and exhaust the low-pressure cylinder when uncovered by the backward movement of the piston, additional exhaust-ports for the low-pressure cylinder which are uncovered by the forward movement of the low-pressure piston, and a valve controlling the admission of steam to the high-pressure cylinder.

2. In a compound engine, the combination of a high-pressure cylinder, a low-pressure cylinder, a plurality of exhaust-ports formed in the high-pressure cylinder which are uncovered at each end of the stroke of thehighpressure piston but are unaffected by the movements of the low-pressure piston, a plurality of exhaust-ports which are formed in the low-pressure cylinder and are covered and uncovered by the movements of the lowpressure piston, an outwardly-opening puppet-valve admitting steam to the cylinder, means driven by the engine for opening the valve, and an automatic device for closing the valve.

In witness whereof I have hereunto set my hand this 11th day of April, 1898.

ELIHU THOMSON.

Witnesses:

DUGALD MCKILLOP, HENRY O. WESTENDARP.

Images