USRE7763E - Improvement in valve-gears of steam-engines - Google Patents

Description

BSheets-Sheet 2. .E. N. DICKERSON. VALVE-GEAR JP STEAM-ENGINES.

ReissuedjJune 26, 18"77.

fie. 7,763.

r all Iozventar:

5 t e '6 h s S t v e e h S 6 N o s R E K c I D N E VALVE-GEAR OF STEAM-ENGINES.

Reissued June 26, 1877.

Invfntow v M, 1

23:56 es.- 7 4% I thereof, in whichhaust-valvehrrangements.

, journals and abrasion.

UN TED STATES EDWARD N. moknn'son, on NEW YORK, N. Y.

IMPROVEMENT IN VALVE-GEARS. OF STEAM-ENGINES.

Specification forming part of To all whom it may concern Be it known that [,Enwum N. Droxnnson, of the city and State of New York, have invented a new and useful Improvement in the. Valve-Gear of Steam-Engines, of which the following is a description, reference being hadto the accompanying drawings, making a part Sheets No. 1 and No. 2 represent a complete drawing, in two elevations, of my im provements as applied to a double-valve eightyone inch beam engine,'together with a section of my improved dash-pot. Sheets Nos. 3 and 4 represent the details of the lifting and tripping apparatus of the steamvalves; and Sheets Nos. 5 and 6, the details of the rock-shaft for working the exhaust and steam valves, whose peculiarity is in its ex- The same letters are used to designate the same parts on the different drawings.

The essential conditions for working steam advantageously in a steam-engine are these:

First, that the steam-valve should begin to open slowly, so as to impose the strain of the boilerpressure upon the piston and its connections by degrees, instead of suddenly, as'is usually done; and the reason is that the rectilineal motion of the piston is exceedingly small at or near the center for a comparatively long are of rotation, while the friction incident to the rotary motion of the shaft and crank-pin journals, under a great pressure, is exceedingly large'in proportion, and therefore pressure on the piston at. or near the center is a loss of power, while, at the same time, the consequence of opening the valve suddenly is to impart a blow which develops heat in the journals by impact, makes it neeessary to key up the engine very close, to

avoid the jar incident to taking up the slack motion of the connections suddenly, and thus excludes oil, and, in consequence, induces hot Second, that after the full boiler pressure has been once imparted to the piston gradually, and it begins to move rapidly, and thus create a demand for steam in the cylinder,

' then that the opening should be suflicien'tly rapid and large to supply that demand without wire-drawing the steam.

Letters Patent No. 68,853, dated September i l, 1867; reissue No. 7,768, dated June 26, 1877 application filed J one 5, 1817.

Third, that the steam-valve should be shut with intense rapidity when the time for effecting the cut-oil has arrived, so as to prevent any loss in wire-drawingthe steam by slow closing.

Fourth, that the cut-oil should be accurate spring of the parts or the different degrees of pressure or lubrication.

Fifth, that the exhaust-valve should be opened before the piston reaches the opposite end of the cylinder, at from thirty to forty degrees of the revolution of the crank, (varying with the speed of rotation,) so that the time necessary for condensation shall be taken while the piston is moving the least in proportion to the circular motion of the crank, and therefore while the least loss is sustained at the same time, the exhaust-valve at the end of the cylinder which thepiston is ap proaching shall be held open till the piston reaches the end of its stroke,'so that no retardation shall be sustained by compressing the steam'and making a cushion under the piston.

To comply with these conditions practically is the object of these improvements.

In the accompanying drawings, Arepresents the rock-shaft, which in this engine works all the valves; but it may be made in two or four parts, according to circumstances, retaining the same 'mode of operation. B is a fixed lifter permanently attached to the steam lifting-rod, which operates on the steam-valve stem V only through the intermediate agency of another lifter, C, which is loose upon the lifting-rod, and which depends upon the fixed lifting-rod and lifter B by the stud E, which rests upon the lever L, centered on the fixed lifter B at one end, having a fulcrum, x, (which, in this case, is the bonnet of the valve-chest,) to support its other end. The lever L is made adjustable by the screw 1, which, being turned, shoves the block M upon which the levee is centered, and which slides in a groove cut into the lifter B, so that the relative positions of the fulcrum, the center'of vibration, and the-point on the lever where the up er lifter is and uniform in its action, unaffected by the by withdrawing the pressure from it; while;

supported, may be changed without changing the position of the since their motion is speed by the pressure of the a stud G in respect to the valve-stem, and, as

a consequence, the speed of the initial lift may be altered at pleasure, so as to admit the steam to the cylinder slowly enough to produce the desired result. The adjustment of this lever may be dispensed with, and the lever fixed permanently, but the result is not so good.

By this arrangement, it is apparent that when the lifting-rod begins to rise the valve itself and the lifter C will rise much slower,

reduced by the interposition of the lever between them and the fixed lifter;:but the "speed of opening will. be increased as the lever continues to rise and to elongate the lever by bringing successive points into contact withits lower curved surface. When, however, the lower lifter B has overtaken the upper one, 0, by closing up the gap left between them, (whose width in this case is about two inches, and is measured by the length of the stud E,) then the valve will continue to rise with the motion of the liftingrod.

The lever itself may be made long enough and so shaped as to impart the increased motion without ceasing to act on the valve, which is the best way in fast-moving engines. Thus theilrst and second essentials for working stearrl'advantageously are complied with.

The dash-pot as improved by me is shown on Sheets No. 1 and No. 2, and marked D.

In Figures 1 and 2 it is head the valves, and connected with the valvestems by two suspension-rods and a crosshead underneath, which is the best arrangement ordinarily, although it may be placed otherwise for the sake of convenience. Fig. 3 shows, in a vertical section, the construction of this new dash-pot; and Fig. 4, alsecn tion through the interior plunger at 1 2.

Its peculiarity consistsin having two oyliu-. ders, one fitting inside the other, havingthe=- machine is fiUed full of water and well packed the airvwill "be excluded by the stufl'ing-box, entirely, and, as the interiorcylinder is raised,

an atmospheric vacuum-is ,left underthe plunger, which is therefore forced downwith high ir when released and allowed todrop. The size of the dashpot in the drawing is such as to make the pressure equal to about six'hundred pounds,

if full of water. If half full, the pressure'is less, and thus any desired amount of spring pressure can be given to shut the valve with intense speed, while-the plunger below will arrest it in time to preventl damage' -to the shown, in connec-. 4 tion with the valves, set on three legs. overmechanism for engaging the valves with and disengaging them from the lifter by which theyare opened.

The first part consists in centering the tripper W on the lifter whichlifts the valve itself. so that its action in tripping is accurate and reliable; whereas, bythe old methods, in which the tripper was centered on some other part of the engine than the lifter, the accuracy of its action was impeded by the spring between the parts, and was aifected by the degree of lubrication.

The operation of this tripper will be seen in Fig. 2, Sheet-sNo. 1 and No, 2, where the trip; per Wis centered at c, and derives its motion from. the rod 8, which is connected to one end; of the bell-crank b', and which is caused tovi-. brate by the rod r, which is conneotedsto one end of the double bell-crank T, which is made to vibrate the-reqnireddistanoe (which in this case is about eleven inches) by attaching tothe pin P a connecting-rod made to move with the; motion of the piston,-orother desired motion-,- backward and forward, Sickels' in hispatent oiv September, 1845,.thus causing the tripper W to vibrate backward;

and forward through an arcof about forty de-.

grace, and to pass at each stroke the roller 01' cam which it is designed 'kv strike which it operates to disengage. the valve from the lifter. Thedouble bell-crank T is centered upon a sliding block; set in a vertical slot, and may be raised or lowered at pleasure. by the 'handleiY or any other suitable contriv aims for. adjusting its position, and. by that means thelpoint of ontoif is, variedatpleas, are, with great uniformity. This trippinganparatus may he, made to wonk in: combination with any method e gaging and disengaging the valves.

My new. detaching apparatus is shown in detail in; Sheets Nos. 3 and 4, where-q Fig. 1 represents a section of the. appa'm, tus in working order; Fig. 2, a plan of the.

same; Fig. 3, an elevation of it from the on. gins-roam; Fig.4, a side elevation and ahalf section, in the same drawing, of the. collar; and Figs. '5 and 6, a planand side elevation; of the vibratingdie.

. S is'a circular collar with a number of rat" dial ribsprojecting from it, running from end to end, parallel with the centralaxis, between which channelsare left, separatingthe ribs, which are marked 9 g. This, collar is slipped over the valve-stem, which it surrounds at a free distance,-so asnot to bind it, and is held in its verticalv position by nuts on the valve stem above and below it, h k. When in position, this collar must be prevented from vibrating around the, valve-stem, which is done by a dog fixed to. the lifter and projecting into one of the channels- This as, descnibedby- Me.

col-lar is small enough in external diameter to pass through a hole in the lifter, which is made to receive it, so that the lifter may be raised above it if need be. The vibrating die B. has radial projections,'pointing toward its center, which correspond with the channels in the collar S, but are narrower than they are, so that it can he slipped down outside of the collar,witb the interior projections entering the channels of the collar, and so brought to rest in a recess formed in the lilter O to receive it, as shown in Fig.1, in such a relative position to thecircular channel t, which is cut round the collar S, that it can turn freely in that channel around the collar The outside edge of a segment of the vibrating die is cut with teeth, and a rack, b, is made to fit into them, on which the roller L is fixed, so that when the rack b is moved endwisc the die R is caused to vibrate; but other means of turning it may be used. The nosition in which the die R is set when at rest is such that its radial projections are under the ribs 9 g of the collar S, as shown in plan at Fig. 2, so that when the lifteris raised it carries up the die R and with it the collar S and the valve-stem and valve attached to it. But

when the roller L is moved it vibrates the die It, so as to bring its radial projections to agree with the channels in the collar S, and the collar, being'no longer supported, will slip down through the litter, and so close the valve and produce the cutoff. When the lifter returns to its lowest position again it brings back with it the die R, and as soon as it passes into the circular channel t the spring K forces the rack 11 back again, and so brings the die it under the ribs 9 g, ready for another lift.

The peculiarity of this engaging and disengaging apparatus is that the 'moving part of it vibrates around a center, instead of moving in some other direction, in reference to the valve stem, whereby a uniform lift of the valve can be got, much greater surface to endurc the abrasion at the instant of tripping, and much greater accuracy in the time of tripping. One or more projections may beused, but for heavy valves the more the better. 0n

large single valves, to cut off short, I should recommend the use of twenty inches of length of edges in contact at the instant of tripping.

By these improvements in the tripping apparatus the fourth essential condition is secured.

set with a lead of about twenty degrees in advance of the line of the crank on the shaft, so that one exhaust-valve would be open about two inches when the piston reached the end .of the stroke, while the other one would close only when the piston had reached the end of the stroke. If the engine has to lworked by hand, however, by the use 01 a trip-shaft, then one of the exhaust-toes must be dropped'out of the way, or both exhaust valves will be open at the same time, and the engine cannot be moved by the tripshaft. To effect this improvement in the manner of removing this toe is the object of this part of the improvement, and it is done by having, one of the exhaust-toes F loose on the shaft,

so that it can be vibrated a short distance around its center, while a permanent toe, W, supports the foot of the stud'U, which is set ona center in a recess made in the toe W, and which can be turned to drop into that recess by the handle H, so that the toe which it supports may fall to the level of the top of the toe W,'and thus come down so low as to permit the lifting-rod to closethe exhaust-valve. In that situation the engine can be ,worked by hand by the trip-shaft.

Of course these improvements are applicable to all sorts of engines and all sorts of valves where the steam-valve is independent of the exhaust, and is to be tripped.

What I claim as my invention, and desire to secure by Letters Patent, is-

1. The combination of the two lifters on the samelifting-rod, one being fixed to it and the other sliding upon it, and the lever, for the purpose of effecting the reduction of the ini tial motion of vopening steam-valves, substantially as described.

2 The combination of the lever for opening the steam-valve gradually with the fixed and movable lifters, the one being moved by the motion of the lifting-rod, and the othersupporting a separate disengaging apparatus, substantially as described.

3. A lever, one end of which is raised by the fixed lifter on the lifting-rod, and by which the steam-valve is pried open gradually, so arranged that it can be adjusted to vary the speed of lifting by shifting the position of the fulcrum on the fixed. lifter to which the lifting power is applied, substantially as described.

4. The vibrating tripper, centered upon the lifter itself, which opens the valve, as distinguished from a tripper which is centered on some other part of the machine, substantially as described.

5. The vibrating die for engaging and disengaging the valve-stem to effect a cut-01f, so

arranged that it will vibrate in an arc whose concave side is presented to the valve-stem, substantially as described.

6. The collar which surrounds the valvestem, having one or more radial ribs upon it, for the purpose of co-operating with a movable die to eflect a cut-ofl', substantially as described.

7. A dash-pot whose plunger is composed of two ylinders of unequal diameters, the smaller of which is the arresting-plunger, forming the bottom of the larger one, and whose exterior chamber is composed of soup or secondary reservoir to receive the arrestit is supported, with a. stud lug-plunger, and above it a confining-vessel to guide the larger cylinder of the plunger and to exclude the air, substantially'as described. i 1

8'. The combination, in a rock-shaft, of one false exhausttoe and ouefixed one, by which or prop between them, so arranged that it can be dropped or elevated at pleasure, substantially as des'crihcd.- v,

9. The vertically-adjustable double bellcrank T, in combination with the'two single hell-cranks b b and connecting rods 1 'r, for

purpose of actuating trippers to nnlat-ch valve-stems from their lifters, to effect a variableIcut-off on steam engines,--suhstantially v as described. I l

10, E0! the purpose of engaging and disengaging the 'valvestem of a cut-off valve with and from the lifter, a collar surrounding the valve-stem, and armed with projecting ribs arranged on opposite sides of the" va ve-stem, in combination with a solid die act on by the trippensuppcrted by the lifter and sur rounding'the valve-stem, armed with projecting points corresponding with the ribs of the collar, so that the valve-ste1nl shall be equally supported on both sides of the center in lifting the valve, and, at the same time, have a long surface of contact between the die and collar, to endure the abrasion of tripping when the die is moved, substantially as'described.

' l EDW. N. DIUKERSQN. Witnesses: v 4

WM. 3. BEAMAN, JrEo. H'Emms. H

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