US75387A - Improvement in yalve-geae foe steam-engines - Google Patents

Description

3 SheetsShee t L E. N. DIGKERSON. VALVE GEAR FOR STEAM ENGINES.

No. 75,387. Patented Mar. 10, 1868.

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Letters Patent No. 75,387,, dated March 10, 1868.

IMPROVEMENTlN VALVE-GEAR FOR STEAM-ENGINES.

' a like fixlgehule reicmh to in time soon mint inn mating not at flgeoiiin i Be itknown that I, EDWARD N. DIGKERSON, of the city of New York, have invented a new and useful Improvement in the Valve-Gear. of Steam-Engines'which, when in use, require toho rvevc'rsed, the object of which improvement is'to remedy the defects and retain andimprovc the advantagesof the link-motion, 'as now commonly used.

' At the time of the introduction oi. the link tion by Mr. Stephenson, all'steam-engines which worked steam expansiioly did so by the use of some up independent cat-off, the most simple and effective of which was aslidc working upon the back of the valve, and alternately closing the ports ii hich passed through it. In locomotives this form of cut-0B was sometimes mado adjustable, through a-porticn of the stroke, either by altering the travel of the cut-ofi' slide, by increasing or diminishing the length of the rocker-arms, which transmitted the motion from the eccentric to the slide, or by dividing the slide into tn'oparts, and, by means of a screw, separating those two parts to a greater or less distance from a centre-bar moved by the eccentric. In these twoiorms the independent cut-oiirctained a value in the estimation of some. locomotive-builders above the link-motion" for several years, but finally tho superiority of the link-motion over all forms of the independent cut-oil has been universally acknowledged, and all locomotives are now constructed with that apparatus, or an equivalent of it, and without an independent cutmfi,

Tho-advantages of the link-motion, which have thizs brought'rtj'nto universal use, are two: first, that it forms a cut-0d variable-from almost full stroke to-about ono-fifth of the stroke, readily adjustable by the same lever ivhich'rcvcrses'the engine; and second, that, as a roversor, the link holds as main valves at all times in positive connection-with the hand-gear, so that; in the attempt toroverse the engine, there is no possibility of a failure of the motion of the valves, if the reversing-lever is thrown into the proper position. Tho link-' motion also has the merit of simplicity.

The main disadvantages of tho link-motion" aro four:. first, when used as a cat-oil, it is usually set to open the -steam-valvo beforo'thc piston has reached-the end of the stroke, by reason of which the steam is admitted to resist the travel of the piston before the stroke is completed; second, it contracts the opening into the cylinder very gradually while cutting ofi', in'conscquenc'e of whichthe steam is wire-drawn," and thereby loses a considerable part of the boiler-pressure before it acts upon the piston; third, it opens the exhaust-valve too soon, and releases the steam from the cylinder before it has expended its force in driving the piston to the end of the stroke; and fourthfltolosos the exhaust-valve, through which the steam that has already performed its work is escaping, boiorothe piston' which is driving itiout of tho cylinder has reached the end of its stroke, in consequence of which the steam, which has done, all the work it is capable-of doing, is confined, and cou1- pressed by the piston, in the end of the cylinder, resisting its motion and forming what is called a cnshionfi The first of these disadvantages causes a total loss cf'tho entire poiven'neoessaryio force back thesteam at boilor-prcssure during the pario'dcf premature admission, as well as of the friction upon the jourualsj'orthe some time. If that admission'is for one-halt an inch (it generally is more) oi the stroke of the piston, (or'oue forty-eighth part of the stroke,) and the steam is of thepressure of one hundred and thirty pounds tothe squareineh, theJos's of pmyorfrom this disadvantago willhe equal to twoand three-fourths pounds to the sqnaro inch, average pressure, for thontiro stroke, which is about seven per cent. of the ordinary working power of a locomotive.

The second of those disadvantages causes a loss of all the elastic f me, of which the steam is deprived by being squeezed through an apertureotoo small to pcrmit'the passage, at 'ioilor-pressurmof the quantity needed to fill the cylinder as tho piston moves; Thoamount of this loss varies' ivith the varyingsizes of the ports and the varying speed of the piston, but it is not less-than ten per cent. of the vhole steam power of the locomotive. flhc whole amount of tho loss from this cause is not oxhihitcd hy an indicator diagram," because the water, which is mechanically suspended in the steam, and carried with it from the boiler into the cylinder during the wire-drawing.process, (but less of which would he carried if the port were snfiiciontly opened for a shorter tin c',) produces no sensible effect upon the indicator. I

'lhc third of thoso disadvantages causes a totalloss of all the elastic force remaining in the steam, which might be employed in driving the piston to the end of the stroke, if the exhaust-valve were kept closed until near that point. The amount of this loss varies, In extreme cases, when the average cyliri-der-pressnrsis' high, the loss amounts to full .sixper cent. Its average is not less than three poi-cent. of the working powerof the ordinary locomotive.-

The fourth of these disadvantages, the eushion," cause: a loss which varies with the speed of the engine; the-amount of olearanco," (or vacant space between the piston at-tho end of the stroke and the valve,) and thesize of the exhaust-nozzles. This loss increases rapidly as the rapidity of the strokes increases, and the accumulated resistance from this cause, at high'vclocity,practically-fixes a limit to the speed of a locomotive. In locomotive-cylinders, with the nsval clearance, the absolute less'from the cushion averages seven per cent. The clearance is an evil unavoidable in connection with the link-motion, but in engines provided with my yalvevgear and with a clearance diminished to the practical minimum, a saving of full twenty per cent. will be efi'ected, in consequence of avoiding the cushion. In stating that the absolute loss from the cushiow"" averages seven per cent, proper deduction has been made for the reduced rate of expansion of the'isteam whieli is driving the piston, incident to the higher mean pressure required to ovorcpme the resistancoof the eushionf and proper allowance for the :re-expnr'ision of thecusliion steam, and for the savingaby filling-tho clearance.

By the use ot' myimp i'ovome'nt, the steam-valve is not opened-until the pistonfreach'cs the end of the stroke, or a little later, and is then opened very gradual-1y for a short time. While thesteam-val've' remains open, it supplies the cylinder with stesm,without any material reduction of pressure in'eonsc'quonee of a contract d opening. When the cut-off slide closes the port, its motion-is so rapid as 'to be practically instantaneous. Th exhaust-valve does not release the steam until its force is effectually expended, and then it opens so rapidly as to release the steam instantly, and he "opposite exhaustwalvc does not close until the piston has reached the extreme end of the stroke, so't'hat no cushion is formed, "Thus all the disadvante es of the ordinary linkmotion are remedied, and all the advantages of thc oi'dinary f link-motion are retained by means of a link, which reversestha engine,v but which is so constructed as to reduce the wear upon itself and its connections to an amount practically no greater than is incurred in thevalve-genr of on ordinary stationary engine incapable of being reversed.

When-the pistonis at the end of the stroke, and the crank. on the centre, it is apparent their no power can result from the application-oi steam-pressure upon the piston, but the friction upon th'e journals and crank-pins of an ordinary locomotive; during the first five degrees of the revolution of the engine from the centre, absorbsmore power than is generated by the motion of the piston during thattime; also, the sudden-admission bf steam into the cylinder produces a shock up'on the crank-pins-and journals like thebl'ow of a hammer, making it necessary to reduce the'slaekj of the connections by driving. the keys hard, in consequence of which, great friction, heated journals, andrapiddestructionof the brasses,-'are produced." With the link-motion, when working at or near full stroke, this sudden admission is not neutralized by a cushion, therefore the. engine' must lie-keyed up--very closevfor that position, and when the out oft is short; and the cushion does prevent the shock of sudden opening, the keys are still tigh't,'and the friction is augmented by the resistance of-ono piston against .tbe'othcr, near the centres. The remedy'oi'thcse evils is effected iiifrn-yimprovement by admittingthe steam through a graduatedapcrtnre, and wire-drawi'ng: it during the time occupied by the crank in'inoving through the first few degrees of the stroke, when fullfpressurc on the piston would be injurious. This gradual admission 7 of'steam cannot be, used advantageously in combination with the ordinary link-motion," because, when the link is cutting 0's short, which is its usual-l operut'i'oiuthe gradually-accumulated cushion" imposes a pressure upon the piston before the steam-valve "opens, and thereby prevents a shock, and renders a graduated opening for the admission of steam useless for that purpose, while, at the some time, the slow closingo-f the graduated valve wire-dra\vs" the steam at n. time when its pressure is needed in the cylinder, and thereby causes an absolute loss of power, but in my combination, where thecut-ofl is e'fl'eeted-by'nn independent sl i de, a'gradua,tcd opening may be used without loss, and, therebci'ng n'o tendeneyto a blow or shock, no cushion is 'fneeded'to anticipate and prevent it. Thus the disadvantages of the premature admission of steam and of thefcusliion" may beremedied In the ordinary link-motion, when used as a eut-ofiQ-tho valve opens the port to a very limited extent, and very rapidly, but clososit very slowly, in consequence of which the piston travels five times as i'ur whiloithe 'v'alveis closirig'ss it travelled while it was opening The effect of this relation between the motions of the piston and the valve is to wive-drawftho steam and diminish its power. In myvaIve-gear, the main valve continues to open during the first seventy-five degrees, more or.lcss; of the revolution of the crank, as in the ldQioshioned lap-valve arrangement, so that steam isslwoys supplied in proportio'nto the demand of the cylinder, if not otherwise cut oil or 'suppressed bnt'my' cut-ell vulveis so arranged as to close with almost instantaneous velocity which is not reduced or affected by its adjustment to dilforent points of the stroke. By this means, the disadvantage of wire-drawing" is remedied.

In the ordinary link-motion, the point of exhaust vnrieswith the point of cut-oil', thereby releasing the steam earlier, as its qualitit yiliminishes'; whereas, if a variation in the time of exhaust were desirable, the greater quantity should be released earlier. Inmy valve-gear the point of exhaust is fixed in the construction of the machine, and may be set to the best advantage. In all cases, the ordinary link-motiozi,.wlienused as a out-o5, exhausts too early for economy, but, by separating the cut-oil valvefrom the exhaust-valve motion, this evil is remedied. I

In ,the'ordinary link-motion," the cushion is unavoidable. In my vslve gear, thqblotv or shock being prevented by the. gradual-opening, as before stated, the exhaust-cavity offhe moiiivulve is elongated,- s'o-that both exhaust-valves will be open at the some time near the end of the stroke, and I make the barof the valve, which covers the port, only as wide as the port itself, (line and line with it,') so that the exhaust-valve does not 4 until the stoam-valyc opens, which is at or after the end of thq stroke Thus there can be no accumulation the ct'nri-lc-pins. This sleeve N surrounds the shaft, but is a. loose fit, so that it maybe turned upon it. In he middle of the sleeve there is a slot chi", about two inches wide, and running around the pipe in a plane at right angles to its axes, for one hundred and thirty degrees. The object of this slot is to allow the pinW to he screwedinto the shaft, and to permit the eccentrics, notwithstandingthe pin, to be moved around the shaft for one hundred and twenty degrees. When the eccentrics are at right angles tothe cranks, and ahead of them as the engine moves forward, the pin-W should be screwed into the shaft at the'b'uci; endiofithe slot. 0 is the adjusting-sleeve, which fits outside the pipe N, end is=madc in two semi-cylindricalhalves, bolted together. on the inside of this sleeve two spiral grooves are cut, as seen at Figure 5, which are intended to receive the end of the pin W, which projects beyond the pipe N about aii'inclrand a. half, and also the block X, which is fixed u'pon the inside sleeve, at the end of the slot opposite to the pin, as set. When the sleeve O is moved from end to end upon the sha'ft, the pin W and the block X traverse the spiral grooves from end to end, and are brought nearer together, or removed farther from each other in the direction of rotation. But as the pin W is fixed in reference to the crank of the engine, it is apparent that the cut-oil" eccentrics must change their angular position to the cranks, as the pipe to which they are fiped is forced around the shaft by" the spiral grooves acting upon the block X, and so an adjustment of the cut-off will be effected through as many degrees of the revolution of the engine as the spiral grooves diverge from each other. The travel of the cut-off slide M; is eight inches, being an increase upon the throw of the eccentric, produced by a difference in the length of the rocker-arms. Thepoint at which the cut-oil willbo effected varies about an inch and a quarter from the centre of the travel of the cutoff slide, so that the centre line oi the eccentric must be very nearly at right angles to its rod when the cufwoti' is cflected, and, therefore, must throw the valve, with nearly its highest-velocity, at any possible point of cut-oil, and by adjusting the lengths of the cut-ofl'slide and connecting-rodg the very highest velocity will be secured at the point of usual work, with very little diminution of speed for all other points of cut-oft. The longer the travel of the out-oil slide, the more perfect will be the out ell, but eight inches are enough for all practical purposes.

For the purpose of placingthe adjustment'of the cut-off within the control of the enginc-drirer, a strap, Y, 18 passed in a groove around the sleeve 0; similar to an eccentric-strap, but with one hinge-joint, for the salie of convenience, instead of two bolted joints. At opposite points in this strap two pins are fixed, Z, which pass through holes in the two ends of a reversing-clutch, 1?, which clutch is forced from one side to the other along the pipe, by a. vertical shaft, Q, which has a projecting'block on one side of its axis, that fits easily into a. mortise in the arm of the clutch P. The shaft Q is vibrated from the foot-hoard of the locomotive, b3} means ofa lever and hell-cranks and rods, connecting with it in amanner well known to engineers, for analogous purposes, the'shifting-clutch being an apparatus well known, and used in England, on some locomotivcs,for altering the "angular position and throw of the main eccentrics. Other means for varyingthe angular position of the cut- 05 eccentrics, when in motion, may be used for the purpose of efi'eeting my method of cut-oil, but I recommend this device, in preference to any other I knew of, for similar purposes, because it completelyproteets the spiral epparatusfrom eigposure. v I

In order to enable engineers to construct my link-motinn, and apply it in ull varieties ofsituations, sheet 2 is prepared, exhibiting five various positions of the centredines and centres occupied by the eccentrics, connectiens, links, and valves, in an entire revolution of an engine. The colors, yellow, hlue, re,d, black, and green, indicate the connection between the velves and their connecting parts throughout. Figj. represents ziccase similar to the drawing on sheet 1, where an intermediate hanger and rockershai't are employed between the link and the valve. Fig. 2 represents a case where the link-block is fixed upon one end of a rocker-arm, and the v olve is worked from the other end, .as is usual with the ordinary link-motion.

In constructing a valve-gear, the draughtsm'an should first determino the length of the link which he would lesire to use, as it determines the length of the radius-bar, which, within certain limits, hears aconstantpropor tion to it. The length of the hanger or rocker-arm, upon which the block is fixed, should be from tweiity-five to thirty three per cent. ofthe length of the radius-her D, which supports the centre of the link, and the chord of the lower segment of the slot in the liuh, from the centre-pin to the end of the slot, must be of the sumo I l ng h as the. hanger or rocker-arm, from its centre totlie centre of the block, with one-haltthe length of the block added. For very fast engines, the larger'proportion is better than the smaller, because a greater lead is thereby effected upon the exhaust-valves; butv the proportion of. lead is a matter of judgment for each eonstructor. When that proportion has been determined, the centre of the hanger or rocker-shaft can be fixed by measuring from the centre of the shaft, a distance as much greater than the length of the hanger or rocker-arm as that proportion requires, and. from'theeentre'of the shaft A, an arc of a circle, x 1, should be drawn, at the distance of the centre of the hunger or rocker-shaft. Upon'that arc, saj at 1, the centre of the hanger 'or rdekershnft must be established. From that centre, with a radius equal to the distance between the centre of the hanger-pin or'rocker-shaft and the centre of the block suspended at the lower end ot'the hanger or rocker-arm, describe an arc of a circle, 14 15, intersecting the main are tit- 2, andextcndingeither side of it, somewhat further than the eccentric throw. In this are the centre of the block will always travel. From the point of intersection of these two arcs, 2, describe another ure, 6 7, with the some radius, and the same general dimensions. The principal are, 2; y, will be the track of the centre of the link, as it is raised or lowered in reversing the engine; the first of the small arcs, 1415, will be the truck described by the centre of the block-pin wheh the engine is working; the second of the small arcs will be thetreek describedby a poin't the lbu'er end of the link, as much below its centre as the centre of the block is belotvvthe contre of the rocker-arm, when the link is in its middle position, and the block is permanently held with its centre coincident with the centre of vibration of the link. In this position draw the line 2 11, which will be the chord of the arc of the link. when constructed, and which is of the some length as the hanger-arm. From the-point 11, and atright angleste the of steam or cushion" in the cylinder at the end of the stroke, nor can water becaaght in the cylinder, nor,

when working through the engine, will it produce any jar or-concussion. In the accompanying drawings-- Sheet 1 represents my valve-gear for a locomotive-engine, drawn upon the scale of one-eighth the actual size; and i I Sheet'2 represents the geometry of my link-motion, in a variety of positions, upon the scale ofo'ne-fourth the actual size. p

The same letters refer to the same partsthroug'hout.

In Figure 1, sheet 1, S represents a part of the engine-frame of an eight-wheel locomotive, with the cylinder attached, and with one driving-wheel, shown in red ink. The engine is represented on the after centre. A is the shaft, B is the 'main eccentric and rod, 0 is the cut-oil eccentric, and G its rod. E is the linlc wh-ichis connected, as usual, with the ccccntric,B, at one end, but the other end is free. D is a radius-bag which is quspended by a strap on the .main shaft, around which it vibrates in reversing the engine. The link E is suspended by the pin T to the end of the radius-bar farthest from the shaft, in the same manner as the ordinary link is suspended to the reversing hand-gear. R is a hunger, the upper end of which is suspended upon the frame by a pin, upon which it swings. To the lower end of this hanger the ordinary link-block is suspended a pin, which passes through it. F is a connecting-rod, which connects the hanger and block'pin with the main, rocker-arm H, to work the main valve L, in the usual manner. j i

Figure 2 is a section through the block, connecting-rod, and hanger-end, showing how, for greater rigidity, the end of the oonnecting-r0d has a hollow pin forged upon it, which passes through the block. From the centre of the'main shaft to theceutre of the link-pin '1, through the radius-bar, the distance is thirty inches, and from the centre of t-h e eccentric to the centre of the pin U is twenty-seven inches and four hundrcdths. From 'the'centre of the pin U to the centre line of the link' is three undone-eighth inches. The hanger is eight inches long from centre to centre,'and the link is cut'in a. circle, the radius of which is twenty-eight and one-half inches to the centre line. The throw of the eccentric is fiv'e and one-half inches, and thc' travel of the main valve four ands half inches. The tumbling-shaft K is connected with the centre of the link in the usual position, but around the-hub of the radius-bar, and by its vibration it elevates or depresses the link to the required positions, in the usual manner. v

Figure 6 represents a plan of the ports and valve-seat. The steam-ports, instead of being rectangular, have their outside edges formed in the shape of an obtuse V, the point of the V projecting half arr-inch outside of the usualedge, and the widest port of'the V being seven inches across. The triangular opening thus formed ought to be-one ninth of the travel of the valve in length, and one-half of the width of thepoft, but this-V-shape may be made in the inside edges of the passages through the main valve, and the ports in the seat left rectangular. The proportion here given issuitable'for enginesmakingono hundredmevolutionsa minute,- but for slow moving enginesthis V-shaped port may be more obtuse-withoutproducing a shock. For fast engines,'the port may he graduated fora longer distance ,of'travel, and with a wider base to the triangle, so as to prevent shocks. -Oucfifth of the travel of the valve, and a base to the triangle as wide as the-port, may he used.

The valve gear is represented in the forward position, in which the axis of the centre-pin of thefiink .is in the same line and centre with the aicis of the centrepin cf the hanger R; and as the radius-bar D holds ,the ceutre-pin of the link firmly in that position, there can be no slip of the'block in thelink as it vibrates; hcncc, all wearing of the link and block is avoided, except that which results from the slip of the block in hacking,

when the link is lowered, and the block works in its upper segment. When the link-centreis lowered sothatit coincides with the cent re of the block, the block is firmly held in. the link, exactly thirty inches from the centrc of the shaft, and although the engine may be running, no motion is imparted to the main valve, and all the wear of valves, when the engine is shut oii, is prevented; whereas, in the ordinary flink-mdtion, the valves arelnever entirely at rest when the engine is moving. Another advantage results in my valve-gear from holding the valves still -on the centre, whicbisg. that both exhaust-ports are kept open at the same time, and in running down hill the'piston is not resisted by atmospheric pressure, as it isby the ordinary link-motion, and the engine will run without steam, in many cases, where steam would otherwise be required to keep the train in motion. This peculiarity will be found of vcrygreat .advantnge on railroads having heavy grades, because, in running down a grade of one to one hundred and thirty, with the ordinary link-motion," the engine requires steam enough in the cylinder to balance the atmospheric pressure which resists the piston, and thus is wasted a quantity of steam, half as muchas would be needed to drive the engine thirty miles an hour on a level. My linkmotio'n isnot capable of producing a cut-oif by itself, and is only valuablein combination with an independent cut-cit, but itflma-y be used advantageously with. any'of the forms of independent cut-cit, besides that herein described.

My apparatus for effecting an independent adj ustable cnt-ofi differs from Pall others, in'thc fitct that'its adjustment is etl'sctcd by varying the angular position of the cut-off eccentrics on the main shaft, in consequence of which any desired range-of adjustment can he obtained, and the cut-oil valve will always be closed at its highest velocity nearly. It may be used with any reversing-apparatus. V 4

Fig. 1, of sheet 1, ifepresentsan elevation of one cut-off in action, adjusted to out off nhr the comm e?- xncnt of the stroke. The cut-ofl' slide M isjnst about to close the port through the main valve L, whichv is opening the point of the V-shuped port, for thendmission tff steam at the commencement of a strok I Figure 4 represents a plan of the cut-off :ippar'atus, with one cut-off valve connected, and with the eccentric for the other valve.

Figure 3 is a section through the mainshaft, sleeves, and adj usting-clutch of the cut-off apparatus. "i'hc' eccentrics, O, are fixed upon a pipo or sleeve,'N,- which, .in this case, is cast in'two halveswith the eccentrics, and bolted together. The eccentrics are atright angles with each other, in tho some direction as- V 15:38! i 6 I. I L

is worked from the'other end, as-in' 2, then the motion of the valve willie-equalised by adjusting then igle -which the valve-rocker arm makes with the block-rocker arm, and that adjqstment'will be nianl'c experimentally asfollows: Construct amovable paper sectcr,,havi-ng drawn upon it'the lines 1, 14-1 15'1,-'i-nnd 1,'5,-'n ml pirr it on the drawing at the centre, 1, so that it will coincide withuthe' lines which it imitates. Turn it till it occupies the position of 16 16, and with the dividers measure all and mark 'uponthe line ofthevalve-stem, 21 22, near the chest, the points 21,"25, 26, and 22,,bcing equidistant from the pointslfi, 23, 24,- and 16, respect-' ively. If, the distance 21 25 is the same as the distance'22 26, the sector has heenpl'aced at the right angle win,

the line 114; .if not, move it around thecentre, 1, to another position, andrepeat the experiment untilthelead and travel of the 'valve agree. The length of them-m 1 16 may require to be-variedto suit the desired valve.

travel, which can be donors in the other case. In this-,casc the valve-arm will not} vibrato equal distances each side ofl a lirie perpendicular to the valve rQd, butwill full lower on one side than the other the valve-motion, however, will be true, and an unequal eccentrimthrow will beconverte'd into an equalvalve-tra vel The four'valves and valve s'eats, colored'hlue, red, black, and green, represent the four positionsof the valve at its points of lead and -full throw,.the blue and red colors representing the position of lead on both centres. The opening made by thc lead amounts to a very small triangle, three-sixteenthsof an inch wide and two inches and five-eighths of an inch long, .but the elasticity of'tho valve-gear and the loss of motion in the joints will reduce this small opening materially, and it is not desirableto have any opening until the engine reaches its centre. If there were no elasticity orlost motion,.I would'make the valve so muchlqnger thanitis hc're shown as to cover the'port when the engine is on the contre,and only open it afterward, The rapidity'with which themain vali'e is opened by this valve-gear is such that, notwithstanding the great portion of the travel 'occnpied'in opening the V-Part of the port, the pressure upon the piston isnot diminishcd, except where it is desirable to diminish it in ordentohave the loss of th'e fi'iction while it is greater than the power, and the shock is prevented .withont expense of power. I I

Inconstructing a locomotive, I would advise the engineer notto finish' the lap and p thaust-cavity of thevalve till-.the'valvegear, is all erected and the'positionof the eccentric is adj ustcd ,andjfixoll. when therparts are all inposition, except the valves, let the enginobo placed on one centre, and let tholinh lie placed with its, centre-pin coincident with the centre of the block-pin, as shown in sheet 2. Then, with the eccentric in a posh ion nearly right, ascertain the position of'the point 10, and mark-it. Turn the engiue' to the other centre, and again marl: the position of 10.- r If it'shonld be the same as at first, the eccentric is in ,the right position; if not, th n the eccentric on the shaft, dividing the'error in halves, and again try the position until'thspoint 10 will 'comcto thesamee xact position atubothcentres of the engine. Then key t'h'e eccentric in that-position-nnd never lc tit bslchauged again. Raise the link to the gc-ahead position, as in sheet Land the rocker-arid will move the valve-stem to the lead. Apply'a t'ompret of thin sheetlmctal, of thechape 5! a longitudinal section, through the main valre, in the place of the valve to the valve-scat, so that it will lie-worked by the valve-stem ,as the wheels are turned, and mark upon it the points of the V- shaped ports, when the ongineis on eachcentre; Measure from those points toward the centre of the templet anamountwhich is expected to'bc lost, by elasticity and lost 'motiomone-eighth of an 'inch more .or less, and those points will he the ends of tholap of the valve. From those points measure again toward the centre of the templet a distance equal to the breadth-of the port from the point of :the V to its opposite side, and the points thus ascertained will be the ends of I the'sxhaust-cavity. Cut the o valve to correspond with the templet thus made, and place it in the chest, and it will have'the-lead and travel which the drawing requires. I I

Thelink, instead of being curved, may he composed of two chords of arcs' meeting at thcceptre, and a rectangular block will work in it, enonghclcarance being made at the angle 'of intersection to .perm1t 1t topasl Q thecentre, and, inasmuoh'as the link only uses a small portion of its length at weekend, and-in the centre, to

give position to the'valves, its otherparts'maybe of'irrcgular form, but a true curve is the best.-

' In running a locomotive constructed upon this plan, the throttle-valve and pipe, which should have an area of one-tent f the are of the cylinder all the way to the chests, should he t hrown wide ,openaftcr the engine is fairly started, and the speed of; the machine should be regulated entirely by the lever which controls the posh tion of the cut-oil, whereby the stesm wilI always be admitted to the cylinder at a pressure very near to that in -the boiler, and thegreatest range'of expansion which the load will permit will at all times he obtained, and congequently the greatest economyof steam will result. I I I I I I I,

' By the use of this improvement the entire theoretical power which steam is capable of producing 111 a nonondensing engine of a given si ze, and performing a given work, will be produccljliin a locomotive-engine, with no deductions except those due to the clearanceff the radiation of heat, and thclealtage from imperfect to. structio'n and of the power thus produced much less will be absorbed by friction, when the engmeusporlced by my mtgen, because there is no resistaneebyene piston against the otherat each centre, as there IS with the I link-motion," and because, there being no shook on the centres, the keys may all be slack, and so thare will be no binding of the brasses. The loss, by leakage, also, will be much diminished, becausethe travel of the valve "is constant, whereas with theFIink-motion" the valveis generally moving with a small travel upon the seat,

which it wears down in'the middle, and=when the travel is increased, as it must be freq u'ntly, the valve runs against an l i n l ft, by the reduction of;- the middlei-surface'bf the seat, and the'efi'ect is' to wear-.the valve touching the seat-on its centre, and rocking-either way. The steamthenlealrs under the into a curved surfac I I e ends of the valve, and is wasted, as may be seen-1n any link-motion? engine which has been unning a month,

1 by setting the slides in the centre and opening the throttle-valve nnd-cyli-nder-cochl 1 r l is v '\hat I claim as my Invention, and desire to secure by Letters I I I I I I I 1 A reversing-link, vibrated byonc eccentric capable of being moved III the direction of itslengrb for suspended at its neutral point by a radius-bar, or other equivalent device, npoil whichit vibr'ates, a

upon the oppoite sideof which .it'works the valve for. the forward and backward motion of the engine, substantialiy as described, in combination with'on'independent cot-ofi' apparatus of any sort, for closiog the ports which it opens.

2. An independent cut-ofl' apparotiis, adjustable while the engine is in mosion, by altering the angular position of the eccentric which works the independent. cufi-ofi' slide, in reference to theline of the crank. substantially as described. i The combination of a pin -or blook'fixed in the mainehoft, with a pipe surrounding the mainehaft to which the cubed eccentrics ore fixed,'a.od with on exterior sliding-sleeve surrounding the said pe, provided with two grooves, one of which-receives the end of tho fixed pin, and the other of which-receives a. blocker pin fixed upon the eccentric-pipe, and one or both of which grooves are spiral, as a device for the purpose o" varying the angular position of the e'utmffeceeritriceupon the main shafgsubstontialiy as described.

'4. A graduated opening through'the main port or.va-1ve, in combination with the exhaust-openings, so arranged as that-one exhaust-aperture will be opened before the other closes, and withen independent adjustahie cut-ofi', for the purpose of preventing'a, cushion of the steam and the shock of eudden admission, without wire-drawing" through the graduated opening in cutting oh, substantially as described.

EDW. N. DIGKERSON.

Witnesses:

J. K. Ronnms, Wm. RYAN.

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