US682757A - Valve-reversing mechanism for explosive-engines. - Google Patents

Description

W. W. SCOTT.

VALVE BEVEBSING MECHANISM FOR EXPLOSIVE ENGINES.

(Application filed Nev. 20, 1899.)

Patented Sept. I7, I901.

(N0 lllodel.)' 2 Sheets-Sheet I.

m: NORRIS PETERS c'o. PHOTO LITHOV WASHINGTON, D. c.

No. 682,757. Patented Sept. l7, l90l.

- w. w. 'SCDT T. v V ALVE REVEBSING MECHANISM FOR EXPLOSIVE ENGINES (Application filed Nov. 20, 1899.) (lo Iodall) I 2 Sheets-Sheet 2.

UNITED STATES PATENT OFFICE.

WALTER W. SCOTT, OF NEW YORK, N. Y., ASSIGNOR TO DIESEL MOTOR COMPANY OF AMERICA, OF SAME PLACE.

VALVE-REVERSIN G MECHANISM FOR EXPLOSlVE-ENGINES.

SIECIFICATION forming part of Letters Patent No. 682,757, dated September 17, 1901.

Application filed November 20, 1899. Serial No. 787,555. (No modeld T0 aZZ whom it may concern.-

Be it known that I, WALTER W. SCOTT, a subject of the Queen of Great Britain, and a resident of the city, county, and State of New York, have invented new and useful Improvements in Valve-Reversing Mechanisms, of which the following is a specification.

My invention relates to valve mechanisms for engines of anytype in which the valverods are operated by cams on a common shaft, and is particularly designed for use in connection with the valve-operating mechanism of the fuel-engine known as the Diesel engine when arranged for marine work. I do not confine the use of my invention to this engine, however, as its application on powerengines of any type is quite feasible.

The object of my invention is to provide a reversing attachment for such valve-operating mechanism of simple, compact, and light construction, easy to operate and to repair.

In the drawings forminga part of this specification, Figure 1 is an isometric View of the engine with myimproved valve-reversing mechanism attached. Fig. 2 is a cross-sectional view longitudinallyof the cam-carrying shaft. Figs. 3, 4, 5, and 6 are detailed views of the cams. Fig. 7 is a diagrammatic end view of the cam-shaft, showing the four cams in their relative positions for giving forward movement to the engine. Fig. 8 is a similar view showing the cams in reverse position for giving backward movement to the engine.

Similar reference characters indicate similar parts throughout the several views.

The Diesel engine shown in the drawings is startedwith compressed air on a two-stroke cycle. This being accomplished, the compressed-air-valve mechanism is thrown out and the fuelvalve mechanism thrown in, whereupon the engine becomes a combustionengine working on a four-stroke cycle,the first stroke drawing in atmospheric air, the second compressing such air to a high temperature, the third or working stroke being caused by the injection of some fuel (usually liquid, as kerosene) which ignites on contact with the hot compressed air, and the fourth expelling the products of combustion. Four valves are therefore necessitated-the fuel-admission valve A, the atmospheric-air-admission valve B,the exhaust-valve C,and the compressed-air admission or starting valve D. These are operated in proper succession by suitable connections A A 13 C D D, provided with antifriction-rollers where they bear on their respective operating-cams A B C D. All these cams are mounted on a shaft E, that is geared to run one revolution to two of the engine, so that ninety degrees of angular motion of the cam-shaft E corresponds to one stroke of the piston. It will readily be seen that the four events which compose a complete cycleadmission of air on the downstroke, compression of the same on the upstroke, admission of fuel to make a power stroke downward, and the exhaust during the following upstrokecorrespond to the four quadrants of the cam-shafts motion. The compressed-air-admission cam D occupies the same quadrant as the fuel-admission cam A and takes its place when starting the engine. (See Fig. 7.)

The fuel and compressed-air admission cams A D do not operate their respective valve-stems A D direct, but move rods A D parallel with them, and upon which are mounted short toes or lifting-levers A D, which can be alternately brought under the valve-stems A D by revolving the rods A D upon which theyare mounted. The lifting-toe D is shown in the drawings in its inoperative and the toe A in its operative position. In this way when the fuel-valve is being operated the compressed-air valve is not, and when the compressed-air valve is in gear the fuel-valve is not, and there is also a middle position of the toes, when neither valve is moved and the engine steps- In practice these toes are so connected that when one is thrown out the other is thrown in, the two operations being substantially simultaneously performed. For this purpose a pinion A is fastened on the cam-rod A and a similar pinion D on the cam-rod D A rack F engages these pinions and can be operated by a lever F, with locking-pin and sector to retain it in middle or either end position. The pinions are of such a length that the endwise movement of the rods A D cannot disengage them from the rack F. For clearness of illustration I have omitted the supporting other way.

by one skilled in the art.

parts and bearings of the valve-stems and cam-rods from the drawings; but the same do not differ from those ordinarily used, and their arrangement will be readily understood An oil-pump (not shown) is operated by the fuel-valve stem and is in operation only when the fuel-valve is used. These devices are already old in the Diesel engine and form no part of my present invention.

It is sometimes necessaryas, for instance, in marine enginesto reverse the engine; and it is the object of my invention to provide means for accomplishing this end. In Fig. 7 I have represented diagrammatically the relative arrangement of the cams and their sequence of operation. The arrow represents the direction of rotation of the cam-shaft, and the quadrants are numbered, respectively, 1 2 3 4 to correspond with the four strokes of the engine-cycle. Now it is evident that if the sequence of operation of the cams, and consequently of the valves, is inverted the engine will be caused to run in the opposite direction, or, in other words, quadrant No. 1 must change place with No. 4, and No. 3 must move over into No. 2. Fig. 8 represents diagrammatically the arrangement of the cams when so shifted for reverse movement, the arrow, as before, indicating the direction of rotation of the cam-shaft. The fuel-admission cam A occupies only about twenty-two and one-half degrees of the third quadrant adjacent to No. 2. Therefore it need only be moved ahead that amount to place it in the correct position for going the The exhaust-cam O occupies about six degrees of quadrant No. 3 and eighty-three degrees of quadrant No. 4, and consequently ends seven degrees short of the end of quadrant No. 4L adjacent to No. 1. It must therefore move backward eighty-three degrees plus six degrees, plus twice seven degrees, or one hundred and three degrees altogether, in order to be in position to run the other way around. The compressed-air-admission cam D occupiesabout eighty-two degrees of No. 3 quadrant, and therefore also moves ahead just that amount. The air-admission cam B occupies about eighty-three degrees of quadrant No. 1, and consequently ends seven degrees short of that end of the quadrant adjacent to No. 4: and must move ahead eighty-three degrees plus twice seven degrees, or ninety-seven degrees altogether. The terms ahead and backward refer to the direction of rotation of the cam-shaft at the time when it is desired to reverse. In order to effect these several angular movements by one operation, the hubs G of the several cams are internally threaded like nuts, but with threads of different pitches and directions, and the shaft E is provided with threads to correspond. These threads are really spirally-arranged splines H, and,

like straight splines, cause the cams to rotate in unison with the shafts rotation, while permitting the shaft to have longitudinal play through the hubs of the cams; but by reason of the spiral arrangement any longi tudinal movement of the shaft will cause angular movement of the cams, dependent in amount and direction upon the pitch and direction of twist of the threads, which are carefully calculated for a given endwise movement of the shaftsay two inches-to shift the cams in the direction and to the angular extent requisite to place them in inverse position, as seen in Fig. 8. The threads and splines thus constitute positive means permanently connected to the cams for changing their angular positions relatively to the shaft and to one another. The construction of the splines H is clearly shown in the cross-sectional view, Fig. 2. The cams are retained longitudinally in position by the bearings I J of the shaft E. The hubs G of the cams also abut against one another to prevent endwise movement. At one end of the shaft is a lever E, with sector and locking-pin to operate the shaft and hold it in the forward or reverse position. The projections oneach cam A B O D are symmetrical. Thisis apparent from the detail views, Figs. 3, 4, 5, and 5, where the incline a has the same slope as the incline a, b as l), c as c, and d as d. It is evident that when arranged for forward movement the valves will open on the inclines a b c d and will close on the inclines a Z; ccl'. When arranged for reverse movement, the opposite action occurs-namely, the valves will open on the inclines a b c d and will close on the inclines a b c d. When the cams are symmetrical, their action is the same in either direction. If desired, the cams may be made asymmetrical, so that the action in reverse movement is different from that in forward movement.

The operation of the reversing mechanism is as follows: Let us suppose the engine to be at speed in the forward direction. The racklever F is now placed in middle position to cause the rack F to disengage the lifting-toe A from the valve-stem A of the fuel-admission, and in the absence of further supply of fuel the engine will come to rest. The camoperating lever E is now moved to its outer limit to reverse the relative positions of the cams A B C D and locked. The rack-lever F is now moved farther to cause the lifting-toe D" to engage the valve-stem D of the compressed-air valve, the first movement of the stem being necessarily given by hand, since the engine is not running. As soon as the engine is satisfactorily under Way the rack-lever F is thrown to its opposite position to disengage the lifting-toe D from the compressed-air-valve stem D and to throw in the fuel-valve toe A and the engine is now running reversed. To put it on forward movement again, a similar series of operations is gone through with, the cam-operating lever E being put into its inner or forward position at the proper time. The engine may be reversed while at speed by throwing the camoperating lever E alone, if care be taken to throw it just when the engine has taken a charge of atmospheric air and is compressing it. In this case the charge so taken will serve both as a cushion to stop the engine and as a source of power to start it in reverse direction. The charge of air alone would not suffice to prevent the crank passing the upper center; but the fuel-cam having been advanced a charge of fuel is admitted before the dead-center is reached, and its combustion and the consequent increase of pressure will insure the reversal of motion. In such case it will be unnecessary to use the compressedair supply, and the rack -lever B" need not be touched. The engine may also be reversed while at speed by first placing the rack-lever F in middle position to shut off the fuel-supply by then throwing the camoperating lever E to reverse the cams while the engine is still running forward and then moving rack-lever F to throw in the compressed-air supply. The compressed air will then stop the engine and start it in the other direction. When properly started, the fuelsupply is to be thrown in in the ordinary manner. There are thus three ways of reversing the enginefirst, by letting it come naturally to rest from want of fuel and starting it in the ordinary way after reversal of the cams; second, by reversing at speed with a charge of atmospheric air in the engine, and, third, by reversing at speed, using compressed air to stop the engine and start it in reverse direction.

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

1. In a valve-reversing mechanism,the com bination of -a rotatable cam-carrying shaft, valve-operating cams thereon and rotatable therewith, valves operated thereby, and positive means permanentlyconnected tothe cams for changing the angular positions of the cams relative to the shaft and to one another, so as to vary the operation of the valves, substantially as described.

2. Inavalve-reversing mechanism,the combination of a rotatable cam-carrying shaft, valve-operating cams thereon and rotatable therewith, valves operated thereby, and positive means permanently connected to the cams for simultaneously changing the angular positions of the cams relative to the shaft and to one another, so as to vary the operation of the valves, substantially as described.

3. In a valve-reversing mechanism,the combination of a rotatable cam-carrying shaft, valve-operating cams thereon and rotatable therewith. valves operated thereby, and positive means permanently connected to the cams for simultaneously reversing the angular positions of the cams relative to the shaft and to one another, so as to reverse the operation of the valves, substantially as described.

4. In a valve-reversing mechanism,the combination of a rotatable cam-carrying shaft capable of longitudinal movement, valve-operating cams thereon and rotatable therewith, said cams being adjustable with respect to'one another, valves operated thereby, means for moving the shaft endwise, and connecting means between the cams and the shaft whereby they are caused to rotate in unison, and whereby, on a longitudinal movement of the shaft, the cams are caused to change their an- 6. In a valve reversin g mechanism the combination of a rotatable cam-carrying shaft capable of longitudinal movement, valve-operating cams thereon and rotatable therewith, valves operated thereby, a shifting-lever for moving the shaft endwise, spiral splines on the shaft, corresponding spiral grooves in the cams, said splines and grooves being of different pitches, whereby the cams and shaft are caused to rotate in unison, and whereby, on a longitudinal movement of the shaft, the cams are caused to change their angular po sitions relative to one another, substantially as described.

7. In a valve-reversing mechanism the combination of a rotatable cam-carryin g shaft capable of longitudinal movement, valve-oper ating cams-thereon and rotatable therewith, valves operated thereby, a shifting-lever for moving the shaft endwise, spiral splines on the shaft, corresponding spiral grooves in the cams, said splines and grooves being of different pitches, whereby the cams and shaft are caused to rotate in unison, and whereby, on a longitudinal movement of the shaft, the cams are caused to simultaneously reverse their angular positions relative to one another, substantially as described.

8. In a valve-reversing mechanism the combination of a rotatable cam-carrying shaft ca pable of longitudinal movement, stationary bearings for said shaft, a series of valve-op= erating-cams on said shaft located between the bearings of the shaft, hubs on said cams encircling the shaft and abutting one another and the shaft-bearings to prevent endwise movement of the cams, valves operated by the cams, a hand-lever for shifting the shaft longitudinally within the cams, spiral splines on the shaft, spiral grooves on the inside of the hubs of the cams, engaging with the spiral splines, said splines and grooves being of different pitches and directions, whereby the cams and shaft are caused to rotate in unison, and whereby, when the shaft is moved longitudinally, the cams are caused to simul taneously reverse their relative angular positions and to operate the valves in inverse order, substantially as described.

9. In a combustion-engine the combination of a combustion-cylinder, valves on said cylinder, valve-stems for the valves, cams to operate the valve-stems having abutting hubs,

my hand in the presence of two subscribing a rotatable shaft on which the cams are mounted, said shaft being capable of longitudinal movement within the cams, stationary means for retaining the cams in alinernent with their respective valve-stems, a hand-lever for shifting the shaft longitudinally Within the cams, spiral splines on the shaft, spiral grooves on the inside of the hubs of the cams, engaging with the spiral splines, whereby the cams and shaft are caused to rotate in unison, and whereby, when the shaft is moved longitudinally, the cams are caused to reverse their relative angular positions and to operate the valves in inverse order, substantially as described.

In testimony whereof I have hereunto setwitnesses.

WALTER W. SCOTT. iVitnesses:

t A. TAYLOR, iii). W. JEFFERY.

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