US393597A

US393597A - Steam-engine

Info

Publication number: US393597A
Authority: US
Priority date: 1888-03-17
Filing date: 1888-03-17
Publication date: 1888-11-27
Anticipated expiration: 1905-11-27

Description

(No Model.) 4 Sheets-Sheet 1; H. H. WESTINGHOUSE & F. M. EITES.

STEAM ENGINE.

No. 393,597. Patented Nov. 27, 1888.

w a 3 J= u x I Q R Q 88 8 Att (No Model.) 1 4 Sheets-Sheet 2. H. H. WESTINGHOUSBiiz P. M. RITES.

STEAM ENGINE.

- No. 393,597. Patented Nov. 27, 1888.

WITNESSES: e

u Pmns PbawLifiwgrapher, Washington, u.c.

(No Model.)

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STEAM 4 Sheets-Sheet 3.

H. H. WESTINGHOUSE & F. M. RITIBS.

ENGINE.

Patented Nov. 27,1888.

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(No Model.) u 4 Sheets-Sheet 4'. H. H. WESTINGHOUSE & F. M. RITES.

STEAM ENGINE.

No.- 893,597. Pa nted Nov. 27, 1888..

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NITED STATES PATENT Orrrcn.

HENRY HERMAN .VILSTINGHOUSE AND FRANCIS M. RITES, OF PITTSBURG,

PENNSYLVANIA.

STEAM-ENGINE.

FAPECIE'ICATIQN forming part of Letters Patent No. 393,597,;1atez1 November 27, 1888.

Application liled March 17, 1888. Serial No. 267,5l9. (No model.)

To all whom it may concern.-

Be it known that we, HENRY HERMAN WESTINGHOUSE and FRANCIS M. Rrcrns, citizens of the Un ited States, residing at Pittsburg, in the county of Allegheny and State of Penn sylvania, have invented or discovered a certain new and useful Improvement in Steam- Eugines, of which improvement the following is a specification.

[ Our invention relates to compound engines of the \Voolf class or type, or that in which an intermediate receiver is not employed, steam being exhausted directly from the high-press are to the low-pressure cylinder; and its ob- I5 ject is to provide an engine of such type having the functions of admission, cut-off, ex.- haust, and compression effected by a single valve or a coincidently-moving pair of valvesections, in which intermediate reduction of pressure without performance of useful work shall be obviated, the number ofport-governing elements reduced between the high-press are and low'pressure cylinders, and substantially uniform compression effected in the high-pressure cylinder under all variations of load and for all points of cut-off, thus attaiir ing, by the employment of a simplified construction, which is readily applicable under various structural conditions, a more perfect utilization of steam than has heretofore been practicable, as is evinced by the indicatorcards produced by an engine in accordance with our invention.

To this end our invention, generally stated, consists in the combination of ahigh and a low pressure cylinder, a distribution valve or valves governing the admission and exhaust of steam to and from said cylinders, and a clearance'chamber or inclosed passage of determined capacity substantially greater than that normal for the traverse of motive fluid, said clearance-chamber being interposed between the high and low pressure cylinders and communicating continuously with the high- 5 pressure cylinder.

The improvement claimed is hereinafter fully set forth.

Practice has demonstrated it to be a desid eratum in the economical use of steam not only that cylinder-compression shall be effected, but also that it shall be finally raised to the degree of the initial pressure at the commencement of the stroke; and to the end of attaining the highest practicable economy and meeting the present requirements of praetical service it is necessary not only that means should be provided for effecting the degree of compression above indicated, but also that these means should possess the capacity of performing their functions under each and every grade of expansion and variation of steampressure under which the engine may from time to time be operated. Such capacity,

or the attainment of such result, is not, so far as our knowledge and information extends, possessed by or resultant from constructions existing or proposed prior to our invention.

In expansion-engines of the Corliss type and others in which compression is controlled by valves independent of those effecting induction and cut-off the compression is constant, and the valve-motion is imperfect in failing to cause the compression to meet the variations of the boiler-pressure. In singlevalve automatic simple engines compression 5 varies with variation of cut-off and becomes a function of the load instead of a function of the initial pressure, somcti mes rising far above the boiler-pressure with short cut-offs and as far short of it with long ones.

The distinguishing feature of our invention is the provision of a valve which by the same lip admits steam to the low pressure cylinder and exhausts it from the high-pressure cylinder, and which, when cutting off for the low pressure cylinder, at the same time effects compression for the high-pressure cylinder within a clearance chamber of comparatively large volume, the same being preferably such as bears substantially the same ratio to that of 0 the high-pressure cylinder as the volume of the latter bears to that of the lowpressure cylinder.

In the operation of an engine in accordance with our invention we cause the terminal compression in the high-pressure cylinder to be independent of load and to vary with boilerpressure only by commencing high-pressure compression in every case coincidently with the commencement of low-pressure expansion, too the variations of pressure at the point of compression in the high-pressure cylinder thereby compensating the variation of the point of compression in such manner that compression will at all points of cut-01f rise to substantially initial pressure, as illustrated by the compression-curve of the series of indicatorcards shown in Fig. 6.

Our improvement provides a single valvemovenientthat is to say, a valve or a coin cidently-moving set of valves, which valve or valves are so constructed and operated in re lation to a clearance-space of determined capacity, which may be located in a valve-chest and port, or two valve chests and a connecting pipe or passage, or two or more of said members, and which is constantly open to a high pressure cylinder, together with a variable cut off mechanism actuating said. valve or valves so as to insure practically the same highpressure compression curve under all loads and at all points of cut-off, and while said curve necessarily varies with the steampressure, its terminal in its several variations coincides practically in each case with theinitial steampressure, waste of steam in filling clearances being thus shown to be avoided. The duty of the valve or portion of the valve governing the high-pressure cylinder is limited to the performance of the functions of higlrpressu re admission and cutoff, while the valve or portion of the valve which governs the low-pressure cylinder effects the exhaust and com pression of the high pressure cylinder and the admission, cut-off, exhaust, and compression of the low-pressure cylinder. Under these conditions, the entire space between the two cylinders, however included, up to the low-pressure valve or valve-section, is constantly in communication with and serves as a clearancespace for the high-pressure cylinder, and in any modification of the mechanism employed the admission and cut-off of the low-pressure cylinder are respectively effected simultaneously with and respectively correspond with the exhaust and compression of the highpressure cylinder. Variations of the point of cut-ofl' being similar in each of two cylinders governed by a single valve-movement, whether applied in a simple or a compound engine,we

are enabled by the employment of a single valve-movement and the provision of a clearance space of determined capacity for the high-pressure cylinder of a compound engine, in connection with the variations of pressure at the points of cut-off in the low-pressure cylinder induced by the variations of the cor responding points of cut-off in the high-pressure cylinder, to effect high-pressure compression to initial pressure at each and all points of cut-off.

In the accompanying drawings, Figure 1 is a vertical longitudinal central section through a single-acting compound engine, illustrating an application of our invention; Figs. 2 and 3, vertical transverse sections through the same at the lines or m and y respectively, of Fig. 1; Fig. 4, a side view, in elevation, of a double-acting tandem compound engine, illus trating another application of our invention; Fig. 5, a horizontal longitudinal central section through the cylinders and valve-chests of the same, and Fig. 6 a diagram illustrating the form of indicator curves developed in the operation of an engine constructed in accordance with our invention.

In the instance shown in Figs. 1 to 3, in elusive, our invention is applied in a singleaeting compound engine having a preliminary or high-pressure cylinder, 1, and a secondary or low-pressure cylinder, 2, which are secured side by side to the top of a closed crankcase, 5, constituting the bed or support of the engine, and serving also as a tank or receptacle for the lubricating material of the journals and crank-pins of the crankshaft 4, the journals 50 of which rotate in bearings 41, fixed in the ends of the crank-case 5. The cylinders l and 2 are fitted, respectively, with pistons 7 and 8, which are coupled by connecting-rods 9 to the crank-pins of double cranks 10, set oppositely,or with their pins one hundred and eighty degrees apart, on the crank-shaft 4.

Motive fluid is admitted to the high-pressure cylinder 1, exhausted therefrom to the low-pressure cylinder 2, and thence exhausted into the atmosphere or into a condenser by a single distribution-valve, which reciprocates in a valve-chest, 3, provided with nozzles or

passages

15 and 11, to which a supply and an exhaust pipe are respectively connected and communicating with the high and the low pressure cylinders by ports 12 and The valve-chest is preferably lined with a bushing, 40, communicating by proper series of ports with the supply and

exhaust passages

15 and 11 and the cylinder-

ports

12 and 14. The distribution-valve, which in this instance is of the piston type, is composed of a highpressure section, 38, and alow-pressure section, 39, which. are secured upon and reciprocate coincidently with a valve-stem, 16, actuated by an eccentric, 20,which is mounted freely upon the crank-shaft 4, and is varied and adjusted in position relatively to the crank-line, so as to effect variation of the degree of expansion in accordance with variations of pressure or load, or both, by an automatic cut-off governor of any suitable and preferred construction. The governor illustrated, which is mounted upon a supporting-wheel, 25, fixed upon the crankshaft 4, is similar in construction to that set forth in Letters Patent of the United States N 0. 384,485, granted to the Westinghouse Machine Oompany, as our assignee, under date of June 12, 1888; but the same does not in and of itself form part of our present invention, and need not therefore be at length herein described. The valve-stein 16 is connected by a link, 44, to one arm of a bell-crank lever, 45, pivoted in hearings on the low-pressure cylinder 2, the other arm of said lever being coupled by a ball-and'sock'et joint or equivalent flexible connection to an eccentric-rod, 19, secured to the strap 21 of the eccentric 20.

The distance between the sections 38 and 39 of the distribution-valve and their relation in position and degree of traverse to the port 12 of the high-pressure cylinder are so fixed that the space within the valve-chest bushing between the sections 38 and 39, together with that within the port12, shall constitute a clearance space or chamber, 42, the capacity of which preferably bears substantially the same ratio to the volume of the high-pressure cylin-' der as that of the latter to the volume of the low-pressure cylinder, and which is continuously in communication with the high-pressu re cylinder. The ratio indicated is that which We have found in practice to develop the most perfect results; but it will be obvious that the capacity ofthe clearancechamber may be increased or diminished relatively to that recommended by us, although with a corresponding variation from maximum useful effect. Thus, for example, experiment has shown that a clearance-chamber having only twenty-four per cent. of the capacity of the high-pressure cylinder may be employed with a valve which is so set as to cut off at different points in the two cylinders, respectively, compression being in such case commenced later and yet carried to initial pressure; but such construction involvcs the disadvantage that the valve must be set out of square and the lead on one side increased and on the other side correspondingly diminished.

The valve-section 98 opens and closes the port or series of ports in the val ve'bushing 40,

communicating with the supply-passage 15, thereby performing the functions of ad mission and cut-off for the higlrpressure cylinder,the cutoff being affected at different points in the stroke of the piston, respectively, in accordance with the variations of position of the cocentric 20 by the gOVGl'l'lOI. The travel of the valve is such that the high-pressure port 1.2 is continuously open, and hence the exhaustand compression of the higlrpressure cylinder are effected independently ot'the valve-section 38. the duty of which, other than a boundary of the clearance-space 42, is limited to the functions firstabove stated. The valve-section 39 effects the opening and closure of the lowpressnre port 14, and thereby performs the functions of admission, cut-off, exhaust, and coi'npression for the low-pressure cylinder,and also those of exhaust for the high-pressure cy linder during the period ofthe stroke in which the low-pressure port 14 is open and the valvebushing ports of the supply-passage 15 are closed, and of compression for the highpressure cylinder during the period in which both the low-pressure port 14 and the valve bushing ports of the supply-passage 15 are closed.

It will be seen that the closure of the lowpressure port 141- coincidently initiates lowpressure expansion and high-pressure compression. in each case, moreover, the valvesection 39 acts as an end boundary of the clearance-space 42.

In operation motive fluid supplied from the passage 15 to the clearaneechamber and the space above the piston 7 of the preliminary or high-pressure cylinder 1 effects the downward movement of said piston at substantially initial pressure throughout the preliminary portion of its stroke at a point in which, regulated by the governor, under existing conditions of load and pressure, the valve-section 3S closes the ports communicating with the passage 15 and cuts off the supply of motive fluid, the remainder of the stroke of the highpressure piston being effected by the expansion of the motive fluid previously admitted and remaining in the clearance-chamber and high-prcssure cylinder. In the farther traverse of the valve the valve section 39 opens the low'pressure port 14 and admits the motive fluid contained in the clearanee-chamber and high-pressure cylinder to the low-press ure cylinder, which motive fluid effects the preliminary portion of the stroke of the lowpressure piston 3 under compound expansion exerted between the smaller and larger cylinders. The distribution valve has meanwhile commenced its traverse in the opposite direction, in the cou rse of which, at a point regu' lated by the governor, its section 39 closes the low'pressu re port 14', cutting off the supply of motive fluid "from the low-pressure cylinder and coincidently closing the clearance-chamber 42, and thereby commencing high-pressure compression. The remaining portion of the stroke of the low-pressure piston is effected under simple expansion---l hat is to say, by the expansion of the motive fluid inclosed in the low pressure cylinderthe motive fluid inclosed in the high-pressure cylinder and clearance chamber being meanwhile in and by the upward stroke of the high-pressure piston compressed at its terminal to substantially initial pressure. Further movement of the valvein the same direction effects the exhaust of the motive fluid which has impelled the low-pressure piston and admits motive fluid to the clearance chamber and higlrpressure cylinder for the next succeeding stroke of the piston of the latter, such new supply being subject to no reduction of prcssurein filling the clearance-chamber, as it meets therein a previous supply of equal pressure, which is utilized in the exertion of such pressure upon the higlrpressnre piston in the stroke about to be made.

' Variations of the grade of expansion in the operation of the engine would under previous practice involve different degrees, respectively, of terminal high-pressu re compression, from the fact that greater or less volumes of motive fluid are, proportionately to the lateness or earliness of the cut-off, admitted to the high-pressure cylinder, while the compressive action of the piston, being exerted through the same space in each case, is uniform at all points of cut-oft. In the practice of our invention we con ntcrael and com pcnsate for such tendency to variation of the degree of terminal compression above or below initial pressure by effecting each and every grade of lowpressure expansion coincidently with the initiatiou of high-pressure compression within a clearance-space of such volume as has been determined by experimental research to be requisite to admit of the degree of terminal compression being raised to without exceeding that of initial pressure at the commencement of the stroke. Each change of the point of cut off is consequently accompanied by a corresponding change of pressure at the point of initial compression, (which point corresponds with the point of cut-off,) due to the greater or less amount of motive fluid which has been expanded from the high-pressure cylinder into the low-pressure cylinder, so that the later the cut-off and the less the volume of motive fluid on which. compression is to be exerted the greater will be the pressure of said volume, and, conversely, the earlier the cut-off and the greater the volume of motive fluid to be compressed the less will be its pressure.

Figs. 4 and 5 illustrate our invention as ap plied in a double-acting tandem compound engine, the high and

low pressure cylinders

1 and 2 of which are secured in line axially upon a bed-plate, 26, their pistons 7 and 8 be ing fixed upon a common piston-rod, 6, the cross head of which is coupled by a connecting-rocl to the pin of a crank on the shaft 4 in the usual manner. The

ports

12 and 12 of the high-pressure cylinder 1 are governed by a distributionwalve, 38, reciprocating in a valve-chest, 3, to which the steam-pipe 15 is connected, and the

ports

14 and 14 of the low pressure cylinder 2 are governed by a distribution valve, 39, working in avalve chest, 3". The valves 38 and 39 are simultaneously op erated in and throughout their traverse in each direction, the stems 16 and 16, to which they are respectively secured, being coupled to a rocker-arm, 19", which is in turn connected to the eccentricrod 19. The eccentric which operates the valves is mounted adjustably upon the c'ank shat, and is, as in the former instance, varied and controlled in position by an automatic cut-off governor carried by a supporting wheel or case, 25, fixed upon the crank shaft.

The valve 38 of the high pressure cylinder is composed of three pistons, a b b, connected at suitable distances one from the other to the valve-stem 16, the central piston, a, controllinga port or series of ports,12, through which steam is admitted from the steam-supply pipe 15 to the valve-chest, and the end pistons, b b, which are of the same diameter as the central piston, at, having no valve function proper, and serving merely to prevent variation of pressure upon opposite sides of the central piston from acting on the governor. The valve 39 of the low-pressure cylinder is composed of four pistons, (Z d e e, secured upon the valvestem 16, the intermediate pistons, e e, governing ports or series of ports communicating with the induction and eduction ports 14, leading from the valve-chest to the ends of the low-pressure cylinder 2, and a port or series valve.

of ports, 14, leading to the exhaustpipe 11. The end pistons, d d, act similarly to those b b of the high-pressure valve, having no valvefunction proper--that is, as to port opening and closureand being provided to prevent variations of pressure on the outer sides of the center pistons, e e, from reacting on the governor. The val ve-

chests

3 and 3 are connected by low-

pressure steamsupply pipes

15 and 15, each of which communicates at one end with constantlyopen ports in the valve-chest 3 of the high-pressure cylinder and at the other with ports in the low-pressure valvechest 3, which, when uncovered by one of the valve-pistons e 6, lead into the ports 14 of the opposite ends of the low-pressure cylinder. The end spaces beyond the valve-pistons b b and d d in the valve-

chests

3 and 3 a may be open to the atmosphere or exhaustpipe or be connected in each chest by a communicating pipe.

The high and low pressure valves 38 and 39 are coincidently operated by the cccentric-rod 19 and rocker-arm 19, and the point of cutoff is, as heretofore, varied by the adjustments of the eccentric elfected by the governor. The clearance-chamber is in this instance made up of the spaces within the ports of the cylinder and valve chest and lowpressure supplypipes and between the end and central pistons of the high-pressure valve and end and intermediate pistons ofthe low-pressure valve. It will be seen that, as in the former case, said chamber is continuously in communication with the highpressure cylinder, and that the high-pressure valve performs the functions of ad mission and cut-ofi' only, those of high-pressure exhaust and compression and of low-pressure admission, cut-off, exhaust, and compres sion being performed by the low-pressure The diagram Fig. 6 illustrates a series of three superposed indicatorcards, a: y 2, according substantially with cards taken under difierent degrees of expansion, respectively, from an engine constructed in accordance with our invention. It will be seen that the points of cut-off correspond in the two cylinders,and that as the pressure at the beginning of highpressure compression changes the point at which compression begins also changes in such manner that compression reaches and terminates at the same point-2'. 6., at substantially initial pressure for each of the several points of cut-off.

From the instances herein exemplified it will be apparent that the structural features and conditions of the application of our improvement maybe modified in various particulars, in the discretion of those skilled in steam-engineering practice, without departing from the spirit and governing principle of our invention, and we do not therefore limit ourselves to the specific construction herein described and shown, mechanical equivalents therefor, when similarly combined and co-opcrating correspondingly to effect the result at tained by our invention, being considered by us to be within its proper and legitimate scope.

It will be further obvious that our invention is, without departure from its governing principle or substantial change of structural elements, applicable in engines of more than one expansion, as well as in the single-expair sion engines selected for illustration.

\Ve are aware that compound engines have been heretofore proposed having valves whose distribution functions are similar to those of our own, as herein described, and we disclaim therefore, broadly, a valve of such character. WVe are further aware that in said engines a port and valve chest space sufiicient to admit of the passage of steam from the high to the low pressure cylinder has been provided,and that said space has been maintained in communication with the high-pressure cylinder. \Veare not, however, aware of any construction in which said space has been made of determined capacity in the sense in which we employ that term-that is to say, of substantially greater capacity than that which will properly suffice for the traverse of steam or so as to constitute a elearancechamber of capacity sufficiently great to permit of compression to boiler'pressure and prevent compression above boiler-pressure-nor are we aware of a construction in which a valve performing distribution functions similar to those herein described has been combined with a clearance-chamber, as above set forth, and with a variable expansion-gear, whereby the degree of compression attained by us may be effected under any and all conditions of load and boiler-pressure.

The method of distributing motive fluid for the practice of which our improvement is designed and specially adapted is not claimed as of our present invention, the same being fully set forth in a separate application, Serial No. 285.801, filed by us September 19, 1.888.

\Ve claim as our invention and desire to seeure by Letters Patentpressure cylinder of different volumes, respectively, a valve or coincidently-operated set of valve-sections effecting the distribution functions of said cylinders, and a clearance-chamber of determined volumesubstantially greater than that required to serve as an avenue for the passage of motive fluid, said clearancechamber being interposed between the cylinders and communicating continuously with the high-pressure cylinder.

2. In a compound engine, the combination, substantially as set forth, of a high and a low pressure cylinder of different volumes, re spectively, a valve or coineidently-operated set of valve-sections effecting the distribution functions of said cylinders, a variable cut-off mechanism coupled to and actuating said valve, and a clearancechamber of capacity suffieiently great to permit (at all points of cut-off and variations of boiler-pressure) of compression to initial pressure, said clearance-chainber being interposed between the cylinders and communicating continuously with the highpressure cylinder.

3. In a compound engine, the combination, substantially as set forth, of a high and low pressurecylinder of different volumes, respectively, a valve or coiucidently-operated set of valve-sections effecting the distribution functions of said cylinders, a variable cut-off mechanism coupled to and actuating said valve, and a clearance chamber or passage of substantially the same ratio in capacity relatively to the higl1pressure cylinder as that of the high-pressure cylinder to the low'pressure cylinder, said chamber being interposed between said cylinders, and being continuously 85 open to the high-pressure cylinder.

In testimony whereof we have hereunto set our hands.

II. HERMAN \VESTINGIIOUSE. FRANCIS M. ItIIES. \Vitnesses as to II. II. Vestinghonse: S. H. SPRAG'UE, FRANK Mooan, IVitnesses as to F. M. Rites: J. SNowDnN BELL, R. H. Wnrrrnnsnv.