US642621A - Valve-gear for engines. - Google Patents

Description

No. 642,62l. Patented Feb.'6, I900. M. R. MOORE.

VALVE GEAR FOR ENGINES.

(Application filed Mar. 3, 1899.)

3 Sheets-Sheet I,

(No Model.)

No. 642,62l. Patented Feb. 6, I900.

M. R. MOORE. I VALVE GEAR FOR ENGINES.

(Application filed Mar. 3, 1899.) )7 (No Model.) 3 Sheats-Sheet 3 ifime a: Jm/ewzw: 3 wwum khg "ma "cams PETERs ca. PKOYO-LIYHO WASHINGTON. b. c.

Mrs. TATES) MATTHEW ROBERT MOORE, OF INDIANAPOLIS, INDIANA, ASSIGNOR TO THE ATLAS ENGINE WORKS, OF SAME PLACE.

VALVE-GEAR, FOR ENGINES.

SPECIFICATION forming part of Letters Patent No. 642,621, dated February 6, 1900.

Application filed March 3, 1899.

To all whom it may concern:

Be it known that I, MATTHEW ROBERT MOORE, a citizen of the United States, residing at Indianapolis, in the county of Marion and State of Indiana, have invented a certain new and useful Improvement in Valve-Gear for Steam-Engines, of which the following is a specification.

The valve-motion is intendedto work with an ordinary single slide-valve proportioned for cutting off by the lap. An eccentric gives a smooth motion with no concussions; but when applied to such valve it opens and closes the passages for the induction and ed notion of the steam slowly. This occasions wire-drawingthe obvious reduction of pressure of the steam in passing through a scantily-opened orificein the early part of the opening motion and the last part of the closing motion. Such wire-drawing is a loss. Many efforts have been made to reduce it by providing liberal passages and opening and closing them rapidly and varying the point of cut-off to effect regulation. The present invention is an improvementin mechanism for attaining these ends.

The requirements for a perfect distribution of steam in the cylinder of a stationary engine are-first, at the beginning of each stroke of the piston the steam-port leading into the end of the cylinder behind the piston shall be amply opened to admit steam at as nearly as possible boiler-pressure, the port at the other end of the cylinder being at the same time fully opened to the exhaust-pipe to permit the free exit of the steam which has done work in the opposite stroke; second, these conditions to be maintained, so as to preserve the initial pressure, until the point of cut-off determined by the governor is reached; third, the admission -port to be closed sharply without arresting the exhaust from the opposite end of the cylinder; fourth, these last conditions to continue, allowing the steam to drive the piston by its elastic expansion, until near the end of the stroke;

. fifth, the exhaustion from the opposite end to be closed and the remaining exhaust-steam before the piston to be compressed (sometimes termed cushioned) to raisethe pressure in the clearance-space and valve pas- Serial No. 707,6 '71. (No model.)

sage or passages, and, sixth, this to continue until just before the end of the stroke, when, seventh, the port to the first end of the cylinder is to be opened to the exhaust, so as to discharge from that end preparatory to the commencement of the return of the piston. The like succession of conditions will occur during the return stroke and will be repeated continuously While the engine is in operation, with the required changes in the position of the cut-off point to maintain uniform speed if the load or the steam -pressure varies. These requirements have been fairly Well met in engines having separate steam and exhaust valves for each end of the cylinder and have been approximated in single-slidevalve engines having a separate cut-off valve but there are serious objections to such additional valve. To obtain such motion with simple mechanism and a single valve and which will allow of rapid revolutions without concussion and noise is the object of my invention.

Economical distribution of the steam can be efiected by means of a properly-proportioned single valve alone by operating with a certain step-by-step motion which may be attained bya cam. The valve and valve-stem may be light, but the operating parts have necessarily much weight, and in ordinary valve-gears the action involves noise and concussions, so as to be seriously objectionable. I have discovered that it is practicable to give such motion by two cams,one fixed on the shaft and the other changeable, and two combined sets of parts operated the reby,with the changes of velocity divided between them, so that the full transitions from slow to rapid motion and back again, occurring during each stroke, shall be confined to the valve and valve-stem. The valve having a proper amount of lap moves rapidly at the several periods of opening and closing the passages and moves slowly at intermediate periods. The offsets in the cams are so gradual and the relatively heavy rollers, rods, and levers directly actuated thereby have so moderate changes of motion that the engine may serve at a high speed without concussion. The construction provides for rapidly changing the point of cutoff through a wide range, so that the action of the governor is peculiarly efficient. The combined levers make the valve move in the same direction as one cam and to twice the extent of motion, the motion being received through an arm which I term a rocker, doubled in extent by an additional part, the lever efiect being what is sometimes termed a lever of the third order, while the portion of the motion of the valve due to the other cam is received through a further rocking mo tion of such additional part. This important part I term a rider. It is a lever of the second order, and in addition to its function of in creasing the effective length of the rocker receives and reverses the motion of the secondcam without increasing it.

The accompanying drawings form a part of this specification and represent what I consider the best means of carrying out the i11- vention. The direction of the motion is indicated by the arrows.

Figure 1 is a side elevation, and Fig. 2 a plan view, on a small scale. Fig. 3 is an elevation showing the fixed cam detached, with the offsets exaggerated in sharpness. It stands in the same position as in Fig. 1. Fig. 4 shows the shifting cam superposed in the same position as in Fig. 1. Fig. 5 shows the same with the shifting cam turned forward to induce a shorter cut-off. Figs. 3, 4, 4", 5, and 5" are approximately right-line diagrams showing the effect of the cams. The horizontal dimensions indicate time, while the vertical dimensions indicate positions of the valve. The vertical lines indicate the ends of the several strokes of the piston. Fig. 3 corresponds to Fig. 3, with allowance for the increase of throw of the valve by the lever effect. Fig. 4 corresponds in a reverse sense to the shifting cam in Fig. 4, with allowance for the reversion of the motion induced by the shifting cam due to the interposition of the rider. Fig. 4 is a compound diagram designed to show how the combined efiect of both cams gives the required periods of movement and rest to the valve, with the shifting cam set as in Fig. 1. Fig. 5 is adiagram corresponding to Fig. 5. It is in all respects similar to Fig. 4 except that in this figure the shifting cam has been shifted forward to condition the engine for cutting off at an earlier period in each stroke. It shows the shifting cam extended in approximately right lines. Fig. 5 is a corresponding diagram showing the combined effect when the shifting cam is thus shifted forward. Fig. 6 is a side view of the cams, on a larger scale, in the adjustment shown in Figs. 1, 2, 3, 4, 3, 4, and 4", with the several transition movements properly graduated.

Similar letters of referenceindicate corresponding parts in all the figures where they and B the valve, which may be an ordinary,

preferably a balanced, slide-valve. Between the valve-chest and the main shaft D of the engine is a double set of valve-actuating connections, one a main part G, which I will refer to as the main rocker, or simply the rocker, pivoted to the engine-bed A at G, and the other' a supplementary part, the rider H H H resembling two cranks set nearly oppositely 011 the ends of a short shaft H, which is journalcd on the top of the main rocker. The crank or arm 11 on the outward end of the shaft H projects downward, and to it near its mid-length is connected the rod 0' of a small piston working in a steam-cylinder A receiving steam through a pipe A and provided with means (not shown) for taking away water of condensation, so that its action shall be always elastic. The arm H on the inner end of the shaft II projects upward and is connected to the valve-rod B and thus to the valve-stem B. The outer arm H extends downward .so far that its wrist'pin h at its lower end may come in line with the pivot G, about which the main rocker G vibrates. If the wrist-pin h at the lower extension of H be held stationary in such position while the main rocker G is vibrated, the upper arm H will serve as if it were merely an extension of the main rocker, receiving its motion entirel y from that part, simply having its throw increased by the increased length of the lever; but if, on the other hand, the main rocker G, and consequently the bearing G carrying the rider-center or short shaft H, beheld stationary and the wrist-pin h be moved back and forth a proper distance on each side of the ex tended line of the pivot-center G, then the short shaft will turn in its bearing on the main rocker G and the upper arm H will move the valve B according as the rider is rocked. width'of the cylinder-port. If both the rider and the rocker are given proper cam motions, that of the-rider must be added to that of the main rocker at the first portion of each stroke in order that steam may be freely admitted to the cylinder and be subtracted during the next portion in order that the steam-port may be closed against the admission of steam and the steam-supply be cut off while the port from the opposite end of the cylinder remains open to the exhaust.

The valve is to be so proportioned that one cylinder-port may be fairly well open to the exhaust and the outside lap will still cover the other port and prevent the admission of the steam, being very nearly like a slidevalve designed to operate with an eccentric proportioned to cut off by the lap at fiveeighths stroke and allow a liberal preexhaust and compression.

Referring again to the figures, J is a camrod guided near the cam b'ya supporting-link J and bearing an antifriction-roller J A similar cam-rod L, mounted adjacent thereto, is correspondingly guided by a link L and equipped with an antifriction-roller L Keyed fast on the engine-shaft next its I make this a distance equal to they IIO ' posite end of the cylinder.

main bearing is a peripheral cam I of such form and set in such a position relatively to that of the engine-crank that bearing against the roller at the end of the main-rocker camrod J it will cause the main rocker G to gently, but rapidly, move near the end of each stroke of the piston in the direction and to the extent required to contribute to slide the valve from the exhaust position due to the stroke to the exhaust position due to the following stroke. The portions of the cam periphery which I term' offsets and which cause these motions are formed in easy curves, and the cams are set to cause the closure of one port sufficiently in advance of the opening of the other to give the proper precedence of compression and release. The intervening portions of the periphery of the cam I are nearly concentric arcs, which cause so little motion to the valve that we may refer to it as stationary. Without any rocking motion of the rider the valve will remain in the position of exhaust until near the completion of the stroke,when it will be quickly shifted, so as to close the exhaust, causing compression of the steam remaining in the cylinder. Just before the end of the stroke it will be further shifted to the position of exhaust for the op- This position will then be maintained until the proper part of the stroke is reached for its change to cause the compression near the end of the return stroke, and so on continuously. Under this condition the valve will never move far enough to open the port for the admission of steam, that part of the valve movement being the function of the rider.

Mounted on the engine-shaft adjacent to the fast cam just described is another cam K, against Whose periphery bears the roller at the end of the cam-rod L, attached to the rider H. This cam is loose and is partially revolved on the shaft by the action of the shaft-governor. (Not shown.) The effect of the partial revolution of this cam forward and backward upon the shaft is to vary the time of the motions caused by it with reference to those caused by the fast cam. It will be readily seen that whatever extent of motion is contributed to the valve by the movable cam acting through the rider will be added to or subtracted from the extent of motion caused by the fixed cam acting through the rocker, according as the rider moves in the same or the opposite direction with the rockers. The motion given the valve is therefore a combination of the motions caused by the two cams, varying in character with the positions of the cams with reference to each other.

The action is peculiar and will be described with care, being partially a repetition.

My valve is arrested or is very slowly moved during three periods in each stroke-first, while the valve at one extreme of its motion holds the port uncovered to induct the steam; second, after the valve has so far moved that the induction is closed, out off, while exhaust from the opposite end of the cylinder is not yet arrested, and, third, after such exhaust is closed to cushion the steam in front of the piston. It is moved rapidly in changing from each of these positions to the next.

I use two cams on the main shaft and two cam-rods leading therefrom toward the cylinder. One of these cams is immovably fixed on the shaft. It operates with a gentle twostep motion the stout rocker G. The second cam is capable of being partiallyrevolved on the shaft. I control such changes by a gov ernor. It connects by a cam-rod to the lower arm of the rider. The upper arm of therider is connected to the valve-stem. The valve will be thrown at the periods and to the extents determined by the two cams, one cam giving motion to the main rocker, and thus moving the rider bodily. It does this with a two-step motion, the first throwing it a certain distance and the last throwing it farther. The word last applied to this concluding step of the motion derived from this fast cam is used advisedly, because there is a second step intervening due to the action of the other cam. The fast cam is unchangeable. The other, the movable cam, gives a single prompt rocking motion to the rider to the full extent of its influence at equal intervals in one direction and the other one motion only for each stroke. The rocking motion of the rider due to this cam is given at variable periods. This motion combined with the twostep motion due to the other cam gives in each stroke three periods of rest, the last of fixed length preceded by two variable in length. These rests and the required quick changes of position from one to the other are all attained with gentle movements of the operating parts. It is practicable with this construction to distribute the steam with unusual perfection while each cam alone induces so slight changes and may be of so easy curves that the engine may run at high speeds and all concussion is avoided. It is also practicable with this construction to employ a governor to vary the times of making the first step of the movement in each direction, so as to regulate the speed without changing the lead or the exhaust or the cushioning. The camrods are supported adjacent to the cams by links, so that the rods may move freely endwise.

I have not shown the construction of the governor, because the mode of action of shaftgovernors is well understood by any person skilled in the art of steam-engineering, who will readily apprehend the mechanical con struction required'to revolve the cam on the shaft through about half a revolution, and also because no particular construction of governor is to be considered a part of this invention.

There may be only a simple link N connecting the heavy levers of the governor (not shown) with a short arm K on the cam K,

the link being properly curved to allow the cam to revolve nearly a half-revolution. The proportions and form of this cam K are such as to give to the rider a gentle, but rapid and complete, transition at one movement from one extreme inclination to the opposite and back again at each revolutiorn The movement of the valve induced by this action introduces an intermediate step in each stroke at variable distances from the commencement, thus giving three instead of two periods of rest. By combining the motion from this source with that due to the other cam I and main rocker G, I make the movements and rests of the valve in the three steps peculiarly eflfective, with an easy motion of the two cams and connections by which the motion is induced. I

The governor is keyed on the shaft in such a position that when in its non-active state, as in starting the engine, it will hold the cam K in the position to add the throw of the rider to that of the main rocker just before the compression-point in the stroke is reached. Consequently when the main rocker completes its motion as the engine-crank is passing the center it will open the port to admit steam for the succeeding stroke, and since to add the throw of the rider to that of the main rocker on one side is to subtract it from the other the steam will not be cut ofi until just before the succeeding compression-point is reached. Thus conditioned the steam will follow the piston at full pressure nearly to the end of the stroke. As the speed of the engine increases and approaches the rate required, the governor, under the influence of centrifugal force, will rotate the cam L forward, so that the steam will be cut off earlier, according to the condition of the load, until should there be an extreme tendency to exceed the proper speed the cam will be brought to such a position as to cause the motion of the rider to discount that of the main rocker, and the port will not be opened for the admission of steam until the proper speed is restored.

Allowance is to be made in the adjusting of the cams for the fact that while the fast cam I is so connected as to throw the valve directlyt'. 6., in the same direction as the cam-rod-the other cam K is so connected as to tend to throw the valve reversely-i. e., in the opposite direction from that of its camrod.

It is obvious that to prevent the rollers from being thrown ofi from the peripheries of the cams under rapid revolutions of the engine they must be pressed thereto with considerable force. To supply this pressure is the office of the small steam-cylinder before mentioned. Its piston-rod is pivoted midway of the length of the lower arm of the rider. Pressure upon its piston, therefore, tends to force both the rocker and the lower end of the rider toward the engine-shaft and causes both rollers to bear against their respective cams with a force due to the piston-area and the amount of pressure thereon, which are to be so proportioned as to secure the result desired. Both rollers are thus firmly pressed against the cams, yet free to follow their peripheries without any interference with each other. Cams and rollers are to have hardened surfaces of ample extent to minimize wear.

The mechanism is simple, inexpensive, and durable. The periods of rest are not absolute, the curves of the cams being so rounded as to allow a slow motion, suificient to prevent the seizure of the valve by the friction of rest.

A rider somewhat analogous to mine has been before used on a rocker; but the lower center was out of coincidence with the fixed center of the rocker, and in order to made a coincidence of motion elaborate calculations or trials must be made, and every change by wear, repair, or readjustment would induce marked changes in the'motion. I attach importance to the fact that when the cam is brought to the proper position the fixed center of the rider coincides with that of the rocker, and thus the rider attains a coincident motion with that of the rocker by simply making the required portion of its operatingcam concentric.

Modifications may be made without departing from the principle or sacrificing the advantages of the invention. I do not claim as new the step motion given to the valve nor the use of a cam to induce such motion. I do not confine the invention to any specific form of governor. Any ordinary construction of shaft-governor which will give sufficient motion will serve the purpose.

I claim as my invention.

1. In a steam-engine, a single slide-valve adapted to efiect the distribution and exhaust from both ends of the cylinder and to cut off by the lap, the two cams I and K, contributing through connections including a rocker to give two quick motions in each stroke separated by a period of rest, the cam I and its rod J connected. to the rocker at a point nearer the center of motion than the valve connection, so that the arrangement multiplies the motion, all substantially as herein specified.

2. In a steam-engine, a single slide-valve adapted to efit'ect thedistribution and exhaust from both ends of the cylinder and to cut off by the lap, the two cams I and K, contributing through connections including a rocker and rider to give two quick motions in each stroke separated by a period of rest, the cam K and its rod L connected to an arm of the rocker of such length that while it is desired for the rider to be ineffective its end may coincide with the fixed center of the rocker, substantially as herein specified.

3. In valve-gear for steam-engines, a single slide-valve and ports proportioned for cutting off by the lap, the rocker G and the rider H pivoted thereon, the latter having Widelydivergent arms one of which is connected to the Valve, in combination with the cam I fast on the shaft, shaped for imparting a two-step reciprocating motion to the connected rocker and the loose governor controlled cam K shaped for imparting a single reciprocating motion to the connected rider and a fluidpressure cylinder and piston connected with the rider near the mid-length of the proper arm thereof, arranged to maintain a reliable but yielding contact of each rod with its cam, all substantially as herein specified.

4. In valve-gear for steam-engines, the rocker, a rider pivoted thereon and having widely-divergent arms one of which is connected to the valve, in combination with rods connected to the rocker and to the other arm of above set forth I affix my signature in pres- 3o ence of two witnesses.

MATTHEW ROBERT MOORE.

Witnesses:

F. H. YOUNT, T. R. KAOKLEY.

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