US287877A - Valve-gear - Google Patents

Description

4 R. un N N Tl. K S D N A R G, E L

VALVE GEAR.

No. 287,877. Patented Nov. 6, 1883.-

N. PETERS. Phamuuwgmpmr, wnshlngtan. D. C.

(No Model.) 4 sheets-sheet 2.

j LE GRAND SKINNBR.

VALVE GEAR.

N0. 287,877. Patented Nov. 6, 1883.

(No Model.)` 4 Sheets-Sheet 3. LE GRAND SKINNER.

VALVE GEAR;

Patented NOV. 6, 1883.

IwvewZ-or 4 Wv'TLem-a .r A

(No Model.) Y l 4 seets-sheen 4.

LEv GRAND SKINNER.

VALVE GEAR.

No'. 287,877. Patenped Nov. 6, 1883.

UNITED STAT/EsY APATENT f o FEICE.

LE GRAND sKINNEE, 0E ERIE, PENNSYLVANIA.

VALVE-GEAR.

SPECIFICATION forming part of Lettersv`Patent No. 287,877., datedrNlovember '-6, 1883.

Y Application filed April 26, 1883. (No model.)

To all whom t may concern.-

Be it known that I, LE GRAND SKINNEE, a citizen of the United States, residing at Erie, in the county of Erie and State of Pennsylvania, have invented certain new and useful Improvements in Valve-` Gears for Steam-Engines; and I do hereby declarethe following to be a-full, clear, and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same. f

This invention consists in providing a new and improved valve-gear for steam-engines.

The Object of the invention is to provide a valve-gear for a `singlevalve which may be adjusted to cut off the steam at any desired point in the piston-stroke without affecting the length of traverse of the valve or changing its lead. Y f

\ In all .valvegearsffor operating, a single lvalve with a variable cut-'off with which I am acquainted, the length', of traverse ofthe valve is changed as the time of cut-off is changed, so that the ports at a one -fourth cut oft'A are opened less than when theV cut-off is at Aonehalf the piston-stroke, thus choking both the supply of steam to and'the exhaustingrof it from the cylinder, and also,V giving anuneven -wear to thevalvefseat. These have been some of the chief objections to the use of a single' valve with a variable cut-off. Y

By this device the above objections are overcome, and the ports are opened justas wide for one point of .cutoff as another'. I ,accomplish this resulty by providing" a ,valve gear which gives the valve an intermitting or .varying movementlin each partof its vibratin and still moves it through anunvarying length of traverse.Y The movement of my valve is as follows, beginning with the valve set so as to take steam'at the outer end of the cylinder and ready to cutoff: a sharp, quick movement just far enough to close the port, but not far enough to close the exhaust of the valve communicating with the opposite port, thus leaving the exhaust-passage open; then a dwell until the piston reaches the end of its stroke 5 then afu'rthermovement in the same direction as before, far enough to carry the valve over and open the opposite port; then a dwell until the elected line of cut-off occurs 5 lthen a sharp, quick return movement just far enough to cut off, 1as on the'other side; then a dwell to the end of the pistonstroke, and then a further return movement, opening the valve as in the beginning; then the dwell in which we found the ports in thebeginning. Thus it will be seen that a complete movement of the valve consists of two separate movements each way and a dwell between each of the several movements-fourin all.

My device is illustrated in the accompanying drawings as follows:-

Figure-l is a side elevation of the gear on .the shaft, and a section through the steamchest, valve, and cylinder-ports, `and a series of diagrams showing the positions of the valve at each dwell. Fig. 2 is a perspective view of the gear. Fig. 3 is a section on the line x in Fig.V 2. Figs. 4, 5, and 6 are detailsof construction. Figs.l 7 and8 are views similar to Fig.` Y1, and 'show alternative constructions,

which will be explained in proper place here inafter.

The parts are indicated by letters and num bers'as follows:

1 2 3r are' the frame of the engine, 4 the steam-chest, 5 the cylinder, and6 the valve.

A is the shaft. B and C are cams on the shaft. E and F are levers movedqby the cams. the valve-rod; G', the valvestem; G2, the stuffing-bok or gland in whichthe stem works, and g2 -is a small piston 0n the stem,forming a packing in the gland. 1 Y

V'Motion is communicated from the cams to the valve-rodG through the levers E and F. The form, arrangement, and position of these levers may be varied very greatly. Two modifications are shown in Figs.` 7 and Y8. /Generically they.V may bedened as follows: a vi- Gis.

brating part, F, having a regular movement a secondrvibrating part, E, mounted on the first-named part, F, and moved by it, and also from a fixed cam or eccentric, C, on the shaft;

The valvelrod receives its motion by being t connected only with the last-named vibrating part, E, and therefore its movements will be,

Y first, such as the partE receives from the cam C through the part F, and, second, such as the part E receives directly from the cam B. As shown, these'parts E and F areconstructed andarranged as follows: In Fig. `l the part F IOO is a lever, pivoted at f on standard 3, and treads upon the cani C by a roller, F. The part E is a lever also, pivoted at e to the lever F, and treads upon the cam B by a roller, E. In Fig. 7 the part F is alever pivoted below the shaft-line on the bed I at f, and treading on the cam C by a roller, and the part E is a lever pivoted to the upper end of F at ci, and receiving its motion from a second lever, El, through a connecting-rod, FP. In Fig. S the part F is a sliding bar held in guides f2 f3, and the part E is the saine as in Fig. 7. It requires no explanation to show that these modifications are all the same in effect, being only such changes as any mechanic might adopt as an expedient, and it is also obvious that many other modifications might as easily bc suggested. l

XVe come now to consider the means by which these parts are moved-viz., the cams.

It may bestated at this point that a simple eccentric may be substituted for the cam C and an eccentricstrap be substituted for the roller F. If this were done, the partF would be vibrated without intermissions or dwells of any perceptible duration, which might be desirable, as a continuous movement of the valve, if slow at points where if operated as above stated there are actual dwells, would prevent dead-points.

The cam C is divided into four spaces, two of which, a a and 'b b', are concentric, and the other two, b a and a b, are eccentric. So we have a lift, a b, and a drop, b c, and two dwells, a a and b b, and hence this cam will move the lever F forward during one-fourth of the time and backward during one-fourth of the time, and will make two intermediate dwells, consuming the other two-fourths of the time, and if the valve were moved only by this lever it would have an even reciprocating :movement, with pauses or dwells at each end of its traverse; but the valve is only moved by this lever Fas it moves the other lever,E, and whatever movement the other lever, E, may have per se will also be communicated to the valve. This brings us to consider the second cam, B, which acts directly upon and gives to the lever E an individual or separate movement. This cam is mounted by the side of the other, and if it were not desired to vary their relative positions in order to vary the cut-01T, they would be made of one piece of metal. This cam has four spaces, of which two are dwells, and the other two respectively a lift and a drop. Thus c d is a lift, d d a dwell, d c a drop, and c c a dwell. I have found it desirable to make the lift and drop on this cam precipitous and the dwells long; but such a construction is not essential. It will be observed that these two cams have their throws in opposition one to the other. The movement of the valve from a these two cams, acting upon the two levers,

will be seen to be as follows, beginning with the parts in the position shown, and the shaft revolving in the direction indicated by the arrow:Y v,The first thing that will occur will be the passage of the lift c'd under the roller E.

This will lift the lever E and move the valve to the right so as to close the port, but not enough to close the exhaust. This position is shown in the first diagram. The lift a b on the cam C will next pass under the roller F. This will throw the valve clear over to the right and open theleft port. (See the nextlower diagram.) Then therewill be a dwell until the drop d c runs under roller E. This will draw back the valve and close the left-hand port. (Sec the third diagram.) Afterthis there will be a dwell until the drop Z1 a on cam C runs under the roller F. This will bring the valve back into the position first shown, and there will then be a dwell until the lift c d again acts.

To vary the cut-off, the duration of thc dwell after the valve is moved off the port must be varied. We have seen that the valve was moved off the port into the position shown by the drop b a on cam C, and that the valve will be moved back over the port by the lift c d on cam B. It must therefore follow that any adjustment of the cam B on C which will change the relative positions of these parts of the cams will vary the time between the two movements one way or the other, as the case may be. To effect this variation the cam B is made adjustable upon the cam C by having a slot, D, in it and a set-screw, D', in the cam C.

It will now be seen that the essential features of thisdevice are as follows:

Two cams, C and B, or equivalents,with their throws in opposition, mounted on the engineshaft, and two vibrating parts, F andE, moved, respectively, by said cams, one of which, E, is connected with the valve-rod and iscarried by the other part, so as to be moved by it as well as by its own cam B. WV here the cams IOO and levers are constructed as shown and the engine is horizontally adjusted, there must be some means for keeping the parts in contactas, for example, a spring arranged at some point. force may be employed it need only act upon the lever E to keep both the rollers E and F in contact with the cams. In place of a spring, I have provided for the use of the pressure of the steam in the steam-chest to hold the parts in contact, thus: In place of an ordinary stuffing-box for the valve-stem, I construct a small cylinder, G2, and on the stem place a small piston, g, which is perfectly packed. The pressure of steam from within the chest acts against this piston g with sufficient force to hold the vibrating parts in contact with the cams.

I am aware that cams with levers, sliding blocks, and like devices having rollers or plane friction-surfaces or yokes have been used to move the valve of a steam-engine, and that two cams with their throw in opposition have been used to move two separate valves-as, for instance, an exhaust and a cut-off valve, but I am not aware that heretofore two cams have been employed to give a single valve an intermittent vibrating movement such as It will also be observed that whateverv IIO 1 cams, one of which is connectedwiththevalve- IIS rod and is carried bythe other part, in a' manner substantially as shown, whereby it may vibrate when moved by the cam with which it is in contact, and will be vibrated when the part supporting it is vibrated by the oth er cam.

2. In the valve-gear of a steam-engine, the combination, substantially as shown, of two cams having their throw in opposition, and

made adjustable relatively one with the other,

and two vibrating parts moved, respectively,

by said cams, one of which is yconnected with the valve-rod and is carriedl bythe other part, in a manner substantially as shown, whereby itV may vibrate when moved by the cam with which4 it is in contact, and will be vibrated when the part supporting it is vibrated by the other cam. f Y y 3. In the valve-gear of a steam-engine wherein two cams are used` to move 'two vibrating parts which act upon the valve-rod, the adjustment of said vibrating parts one upon the other, in a 'manner substantially as shown,

whereby a force acting upon one of said parts Y to hold it upon its cam will also hold the other part upon its cam. i t In testimony whereof I affix my signature in presence of two witnesses. 'l

,LE GRAND SKINNER. Vitnesses: Y Y

JN0. K. HALLooK, Roisin. H. PORTER.

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