US331506A - Assighob of one-half to - Google Patents

Description

D, OB. LADD.

SLIDE VALVE.

No. 331.506. Patented Dec. 1, 1885'.

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(No Model.) 3 Sheets-Sheet 2.

D. OB. LADD..

SLIDE VALVE.

No. 331,506. Patented Dec. 1, 1885.

(No Model.) 3 SheetS--Sheet 3.

D OB. LADD.

SLIDE VALVE.

Patented Dec. 1, 1885.

t) NTT no dTaTns DENNIS OIB.

LADD, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO FARNSVVORTH, OF SAME PLAGE.

SLIDE-VALVE..

"-lftf'l-"er forming part of Letters Patent No. 331,506, dated December l, 1885.

Application filed March 30, 18H5. Serial No. 160,557. (No model.)

' To ctZZ whom t may concern,.-

Ie it known that I, DENNIS OB. LADD, a citizen oi' the United States, residing at Ghicage, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Slide-'Valve Mechanism for Steam-Engines, of which I do declare the following to be a full, clear, and exact description, reference being had to the accompanying drawings, forming part oi' this specification.

My present invention has relation to the improvement ofthat class of steam-engines wherein the main or driving piston is controlled by a slide-valve so constructed that is to say, provided with lapi-thatit will admitsteam to the main cylinder during a portion only of the piston-stroke, the steam so admitted causing, by reason of its expansion, the completion of the piston stroke. In the usual form of valves of this class the construction is such that one and the same movement of the valve determines proportionately both the period oi' admissiomand exhaust of the steam to and from the main cylinder, so that if the valve be given a very short stroke, in order to cut the steam oit' short,7 the period during which the exhaust-port -of the main cylinder will be opened and steam can escape therep from will be correspondingly lessened. `Hence the force of the expansive steam upon the induction side of the main piston will be resisted by the confined steam and air upon the eX- haust side of the piston, which is unable to escape by reason oi" the exhaust-port being closed. t'

It is a fact well recognized in steam engineering that, in order to obtain the most effective work from the engine, it is of the utmost importance that the back-pressure in the cylinder-that is to saythe resistance on the eX- haust side or" the piston-should be reduced to the lowest degree possible, for the reason that all back-pressure not only diminishes the efficiency of the engine but is also a total loss of energy. Ihe most satisfactory results are obtained, therefore, when the indicator-card of the diagram of the engine shows the line of back-pressure approximating as closely as possible to the atmospheric liuc, or, in other words, shows a practical absence of backpressure. In working engines at a very high rate of speed the steam is usually cut off very short, and it is, therefore, in such cases that the loss incidentto back-pressure is most seriously encountered.

My present invention has for its object to provide a slide-valve of such improved construction that a uniform free exhaust from the main cylinder may` be obtained during both the direct and expansive action of the steam,

and that the hack-pressure incident to the usual closing of the exhaust during such period may be avoided.

To this end my invention consists, primarily, in a slide-valve having escape-ports therein, and provided with suitableI supplemental valve mechanism for opening and closing said escape-ports in such manner that there will be a free exhaust from the main cylinder during the time that the steam therein is acting both directly and eXpansively.

My invention also consists in various novel features of construction hereinafter described, illustrated in the accompanyingdrawings, and particularly defined in the claims at the end of the specification.

Figure lis a perspective view of my improved slidc-valve, showing one side thereof detached. Fig. 2 is a View in side elevation. Fig. 3 is a view in central vertical section. Fig. .tis a view in horizontal section on line x c of Fig. 2. Fig. 5 is a detail fractional View in vertical section on line y y of Fig. 2. Fig. 6 is a view yin central horizontal section on reduced scale, showing my improved valve as applied to the cylinder of an engine. Fig. 7 is a detail perspective view of what I term the supplemcntalpiston and the equalizing-bar. Fig. 8 is a detail perspective View from the back side of what I have termed the supplemental valve.7 Fig. 9 is a detail perspective View of what is termed the auX- iliary valve. Fig. l0 is a view on reduced scale in side elevation, showing the position of the slide-valve within the steam-chest, and showing the means for adjusting the auxiliary valve.

A designates the main body of the slidevalve, which is suitably attached, as by the nut w, to the usual valve-rod, NV, and consists of ahollow or chambered casting provided with an exhaust-cavity, a, upon either side whereof are the escape-ports B and B', which correspond in length to the ports of the steam- Ways c c' of the main cylinder C, although somewhat narrower than such ports. The exhaust-cavity a is preferably cut away at its back, as shown,to decrease the friction-surface of the supplemental valveseat. In the upper and lower parts of the sli devalve between the escape-ports B and B', and communicating with the chamber of the slide valve, are formed, respectively, the cscape-ports BAZ and B3, which communicate with the exhaustport c`z of the main cylinder, and serve to deliver exhaust-steam thereto from the escape-ports B and B of the slide-valve. Vithin the chamber A2 of the main slide-valve is placed the supplemental valve D, theface of which bears upon the seat back of the exhaust-cavity a, and is adapted to alternately open and close the escape-ports B B'. This supplemental valve D, as particularly seen in Figs. 3 and 8,is preferably formed of different thicknesses, the thinnest portions at the top and bottom being held between the cross-bars E and E', the ends of which rest within the grooves e in the wall of the valve. The cross-bars E and E' are held in place by means of the back plate A3,through the bolt-holes at of which suitable bolts, c3, will pass into the holes a* of the slide-valve wall. Upon the back plate Aare formed the lugs c5, through which pass the set-screws c6, that bear upon the cross-bars E andE', and allow the same to be adjusted to compensate for wear. rl'he central portion of the cross-bar E is cutaway, as shown, to allow free egress of the exhaust-steam from the escape-ports B and B and chamber A2 into the escape-port B2. Upon the back of the supplemental valve D is formed the stud d, and

around this stud fits the squared washer d', that enters the squared opening in the equalizing-bar F, the lower end of which is fulcrumed in the socket e2 of the cross-bar E', and the upper end is formed with segmental rackbarf, which engages with the rack-bar g of supplemental pistonvalve G, by which the supplemental valve is moved,as will presently appear. The equalizing-bar is held in place upon the stud l by means of the clampplate F2, which is connected to the shouldered lugs cl2 and d3 of the supplemental valve by means of suitable dowel-pins.

My purpose in connecting the supplemental valve D with its operating-piston G by means of the equaliZing-bar F is to enable movement to be imparted to this valve from a central point, so that greater freedom and evenness of movement and less friction will result than would be the case were the piston connected directly to the valve near its top.

About the center of the back plate A3 of the slide-valve an opening is formed of an area, preferably, somewhat greater than the area of either of the escape-ports B or B', and within this opening is fitted the pressure-plug H, formed of the plates h h', with intermediate Washer-rings united by the screw h2, or in other suitable manner. The function of this pressure-plug is to hold the supplemental valve D snugly against its seat and compensate for any wearl of parts, and this it will accomplish by reason of the inward pressure upon it of the live steam within the steamchest.

From the construction of parts as thus far dened, and by reference to Fig. 6, wherein the position of my improved valve with respect to the main cylinder is sh iwn, it will be apparent that when steam Yis being admitted to the main cylinder through one of the steamways, as c, the exhaust-steam and air upon the exhaust side of the piston can pass freely through the steamway c', escape-port B', chamber A2, and ports B and B3 into the exhaust-cavity a of the slide'valve, whence it will discharge freely into the open air. This discharge ofthe exhaust-steam and air through the steamway c and escape-port B continues until approximately the end of the pistonstroke, so that during the forward movement ofthe piston there will be no confinement of the steam and air on the exhaust side, and consequently no back-pressure to resist the movement of the piston. At the end of the forward stroke of the piston, when the exhaust is practically complete, the supplemental valve D will be forced to close the cscape-port B', and the preferred mechanism by which this movement of the supplemental Valve can be effeted will next be described.

The piston G, connected with the equalizing-bar F, has its ends sustained, respectively, within the cylinders K and K', formed in the wall of the slide-valve A, and both of these cylinders and their connections are in all respects alike. For convenience of construction and replacement of parts, the slide-valve A is formed with the threaded portions a? at its ends, over which portions fit the screw-caps L, that form the ends of the cylinders K K'. From the top of these cylinders extend the steam-channels k'k',whieh, as shown in Fig. 2, terminate in the ports in the groove or way M, wherein works the auxiliary valve N as the slide-valve is moved to and fro within the steam-chest. rIhis auxiliary valve is provided at its top with aloop,n,or other suitable means, whereby it is fixed in a manner permitting slight lateral play on the auxiliary valve stem O, the ends of which are held respectively withina stuflingbox, o, and threaded perforation o in opposite side of the steam-chest, so that by means of the hand-wheel o2 the position of the auxiliary valve may be readily adjusted for the purpose of equalizing the exhaust action at each part of the stroke. The body of the auxiliary valveis hollow, as seen in Fig. 9, and is provided with the end escape-ports, n' n2, adapted to be brought respectively coinci- IOO IIO

dent to the ports of the steam-channels 7c and v k, and is provided also with the long central escape-port, n3,which in the various positions ofthe auxiliary valve with respect to the slidevalve will be held above the escape-port as, that is in free communication with the escapeport B2 in the upper portion of the slide-valve, as seen in Fig. 3. Each of steam-channels 7c and k, at aslight'dist-ance above the cylinders K K', is connected with a cross channel, p, which leads therefrom to the space p of the cushion-valve P. The cushion-valves P and P are provided at their outer ends with stems pwhich project through the caps L, and the diameter of these stems is so much smaller than the diameter of the channels p that when either of these steam-channels is open for the ingress ot' live steam, the corresponding cushion-valve will be forced outward, as shown at the left-hand side of Fig. 2. The space p of each of the cushion-valves P and P communicates with the cylinders K K by means of the short channels p3, and in each end of the piston G is formed an angular channel, g', the rear part of which is adapted to coincide with the steam-channel k, as seen at the right-hand side of Fig. 2.

From the foregoing description the operation of my improved slide-valve will be seen to be as follows: Assume theparts to be in the position shown in Fig. 6, the main piston being at the beginning of its forward stroke, at this instant the relative position of the slide-valve and the auxiliary valve N is such that the upper port of the channel 7u has just been uncovered, and the steam entering` by this channel and the channels p and g, has forced the cushion-plug-P outward, and has forced backward the supplemental piston G, thus causing` it to move the supplemental valve D over the escape-port B of the main valve. Live steam is now being admitted from steamchest A4 through the steamway c of the main cylinder, and the exhaust-steam is escaping freely from the main cylinder through the steamway c' into the escape-port B of the slide-valve, and thence into the chamber A2 of the valve, and through the upper and lower escape-ports, B2 and B3, (see Fig. 3,) into the exhaust-port c2 of. the main cylinder. Steam thus continues to exhaust through the steamway c and escape-port B not only while live steam is entering through the steamway c, but also after the slide-valve has cut off the steam from the way c, so that the steam is workingl expansively, and until on t-he return movement of the slide-valve the escape-port B of this valve is about oppositethe steamway c. It is when the slide-valve is working with a very short stroke that the entire exhaust will thus occur through the escape-port B; but it will be readily seen that if the slide-valve is working with a long stroke, the rst part of the exhaust will occur through the steamway c and escape-port B and the last part of the exhaust through the steamway c and the usual exhaustcavity, a, and exhaust-port o2. When `channel 7c will be uncovered so as to admit live steam, and at the same time the upper` `port of the channel 7s will for an instant coincide with the escape-port a2 of the auxiliary valve N, so as to permit the steam to escape from the cylinder of the supplemental piston.

lt will thus be seen that the live steam entering the channel It' will force the supplemental piston G backward and cause it to so move the supplemental valve D as to uncover the escape-port B of the main slide-valve, and allow the exhaust to escape through said port into the chamber A2 and escape-ports B2 B3 leading therefrom, while at the same time live steam is entering the main cylinder C through the steamway c and is working expansively within the cylinder.

Referring to Fig. 2, and assuming the parts to be in the position there shown, it will be readily understood that if the main slidevalve be moved to the right a sutlicient distance to uncover the upper port of thc chan- .nel k and admit live steam thereto, and at the same time bring the lupper port of the channel It for an instant beneath the escape port u2 of the auxiliary valve N, the pressure of steam upon the stem p of the cushion-valve P would force this valve inward, thereby closing the channel p3. At the same time live steam entering the channel It would 'force the cushion-valve P outward, thereby uncovering the channel p3 beneath said valve, and by passing through the channel g in the end of the piston G would give an initial backward movement to the piston. The piston G as it passed the channel k would be cushioned by the steam coniined between such channel and the cap L of the cylinder, since by reason of the closing of the cushion-valve P the steam could not escape through the channel p3. This cushioning of t-he supplemental piston is of importance, as it avoids all danger of the piston hammering out the ends ot' its cylinders.

From the foregoing description it will be seen that by my improved construction of slide-valve a free and uniform exhaust is obtained from the main cylinder during the period that the piston is working both by the direct and expansive action of the steam, so that all loss of energy and constant increase and cost ot' running the engine incident to back-pressure is entirely avoided. The advantages due to my invention are so obvious as to need no further elaboration.

It will be readily understood that the precise details of construction above described may be varied within wide limits without departing from the spirit and scope of my invention. Thus for example the supplemental valve and piston may be connected directly IIO IZO

together instead of by an equalizing-bar, the arrangement of steam channel may be varied, and certain features of the invention may be employed Without using the invention entire.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. The combination, with a cylinder having suitable steamways, of a main slide-valve having escape ports therein adapted to be brought coincident with said steamways, and having a supplemental valve adapted to open and close the escape-ports of the slide-valve, said slide-valve and supplemental valve being arranged for relative (3o-operation, substantially in the manner and for the purpose described.

2. The combination, with a cylinder having suitable steamways, of a chambered slidevalve having escape-ports therein adapted to be brought coincident With said steamways, and a supplemental valve placed within the slide-valve and adapted to open and close the escape-ports thereof, substantially as described.

3. The combination, With a cylinderl having suitable steainways, of a main slide-valve having escape-ports therein, a supplemental valve for opening and closing the slide-valve ports, and a supplemental piston and an auxiliary valve for controlling the movement of the supplemental valve, said several parts being relatively arranged for co-operation substantially in the manner and for the purpose set forth.

4. The combination, with acylinder having suitable steamways,ot' a slide-valve having escape-ports therein, a supplemental valve for openin g and closing the said escape-ports, asnppleinental piston in connection with said supplemental valves, an auxiliary valve for said piston, and an adjustable rod for said auxiliary valve, substantially as described.

5. The combination, With a cylinder having suitable steamways, of a slide-valve having escape-ports therein, a supplemental valve located Within the slide-valve for opening and closing its escape-ports, and a pressure-plug in the Wall of said slide-valve adapted to hold the supplemental valve to its seat, substantially as described.

6. The combination, With a cylinder having suitable steamways, of a slide-valve having escape-ports therein, a supplemental valve l'or opening and closing said escape-ports, a supplemental piston in connection with the supplemental valve, an auxiliary valve for said piston and cushion-plugs for thesaid piston, the various parts being provided with suitable steam-channels, substantially as described.

7. rlhe combination, vwith a cylinder provided With suitable steamways, of a slidevalve having escape-ports therein, a supplemental valve for opening and closing said escape-ports, a supplemental piston for operating the supplemental valve, and a pivotal link connecting said supplemental valve and piston, substantially as described.

DENNIS OB. LADD.

Witnesses:

GEO. P. Fisrrnn., J r., JAMES H. Piemon.

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