US2130075A

US2130075A - Exhaust valve means

Info

Publication number: US2130075A
Application number: US114568A
Authority: US
Inventors: Edward S Dennison
Original assignee: Electric Boat Corp
Current assignee: Electric Boat Corp
Priority date: 1936-12-07
Filing date: 1936-12-07
Publication date: 1938-09-13
Anticipated expiration: 1955-09-13

Description

Sept.. 13, 1938. E. s. DENNlsoN EXHAUST VALVE MEANS Filed Dec. '7, 1936 6 Sheets-Sheet 2 z wfL Sept 13, 1938. E. s. DENNISON 2,130,075

EXHAUST VALVE MEANS Filed Dec. 7, 1936 6 Sheets-Sheet 5 Sept. 13, 1938. E. s. DENNlsoN EXHAUST VALVE MEANS Filed Dec. 7, 1936 6 Sheets-Sheet 4 Sept. 13, 1938. E. s. DENNlsoN EXHAUST VALVE MEANS SSheecs-Sheet 5 Filed Dec. '7, 1936 Sept. 13, 1938; E. s. DENNISON 2,130,075

EXHAUST VALVE MEANS Filed Dec. 7, 1936 6 Sheets-Sheet 6 Patented Sept. A13, 1938 UNITEDl STATES PATENT oFFici-z EXHAUST VALVE MEANS Appucatmn'nember 7,1936, serial No. 114,568`

9 Claims.

This invention relates to internal combustion engines and has to do with exhaust valve means and associated features.

The valve means and associatedv features of my invention are illustrated, by way of example, as applied to a two-cycle double-acting injection engine, for which my invention is particularly suitable. Among the objects of my invention are the provision of means for increasing the cylinder charge by preventing escape of air at the start of the compression stroke, controlling the 'exhaust by a single rotary valve continuously driven and of symmetrical construction such that the pressures are equalized and distortion of the valve .5 is prevented, the provision of improved valve operating means for driving a. plurality of valves as a unit while permitting individual adjustment of the valves as well as simultaneous and similar adjustment thereof, and the provision of 'improved means for preventing leakage of exhaust gases about the valve. Further objects and advantages will appear from the detail description. f

In the drawings:

Figure 1 is a side View of a three-cylinder injection engine embodying the valve means of my invention, viewed from the fuel pump and intake manifold side, the center 'cylinder being shown in section with parts shown in elevation;

Figure 2 is a sectional view, on an enlarged scale, taken substantially on line 2-2 of Figure 1, parts being broken away;

Figure 3 is a sectional view, on an enlarged scale, taken substantially on line 3-3 of Figure 1, parts being broken away and other parts being shown in elevation;

Figure 4 is a sectional view taken substantially on line 4--4 of Figure 3, partly broken away and with the intake manifold omitted, certain other parts being also omitted for clearness of illustration;

Figure 5 is a sectional view, on an enlarged scale, taken substantially in the plane of line 5--5 of Figure 3, through two adjacent port belt members, certain parts being broken away and other parts being shown in plan;

Figure 6 is asectional view, on an enlarged scale, taken substantially on line 6-6 of Figure 2;

Figure 7 is a fragmentary sectional View, taken substantially on line 1-1 of Figure 6.

The particular construction of the engine, in general, has no direct bearing on the instant invention and, accordingly. only those features which are related to orcontribute to the invention herein disclosed and claimed need be considered in detail. Preferably, however, the engine construction is similar to that disclosed in my copending application for Internal combustion engine, filed January 7, 1937, Serial No; 119,422.

The engine comprises a. crank case I0 upon which are suitably mounted and secured a plurality of cylinders Il, three cylinders being shown.

A piston I2, shaped as shown in Figure 3, operates in each cylinder and has secured thereto a piston rod I3 operating through a stuiiing box 10 I4 suitably mounted in thelower head I5 of the cylinder. The lower end ofpiston rod I3 is secured in a member I6 to which is secured a crosshead Il' slidable in guideways in the crank case I0. A connecting rod I8 is pivoted at its upper end to member I 6 and is connected at its lower end, in a known manner, to crank shaft I9 of the engine.

An injection nozzle is mounted in the upper cylinder head 2l centrally thereof for injecting 20 fuel into the cylinder axially of the latter, An .injection nozzle 22 is mounted in the lower head I5 radially thereof for injecting fuel into the lower end of the cylinder. Fuel is supplied to the injection nozzles from fuel pumps 23 suitably mounted at one side of the engine and driven in any suitable or preferred manner, there being two pumps for each cylinder.

l 'I'he engine illustrated is a two-cycle doubleacting injection engine. Each cylinder II is pro- 30 vided, at its mid-portion, with a thickened port boss 25 extending circumferentially thereof. Upper and lower series of exhaust ports 26 and 2l, respectively, open through boss 25 at one side of the cylinder and a series of inlet ports 28 open through boss 25 at the opposite side of ,the cylinder, the ports 28 preferably being disposed between the upper series of exhaust ports 26 and the lower series of exhaust ports 2l, as in Figure 3. The two latter series of ports are separated by a bridge element 29 of boss 25. The exhaust and the inlet ports are controlled by the piston I 2 during reciprocation thereof, for exhausting the burned gases and scavenging the cylinder and chargingit with air, in a manner 45 well understoodrin this art.

A port belt member 30 extends about boss 25 and is provided with inwardly projecting ribs 3| which contact boss 25 between the series of inlet ports 28 and the two series of exhaust ports 50 26 and 21. The right side of member 30, as viewed in Figs. 3 and 4, is ilat and has secured thereto an upwardly extending elbow 32 defining, with member 30, an intake passage 33. Elbow 32 is suitably secured, at its upper end, to an air int'ake manifold 3l into which the elbow opens as I shown in Figure 3. As the piston I2 approaches the end of its combustion or` working stroke in either direction the inlet ports 26 are uncovered and the appropriate exhaust ports are also uncovered, the entering air serving to scavenge the cylinder and charge it with air. To facilitate the scavenging operation, the ends of piston l2 are of frusto-conical shape, as shown, for directing the entering air chargetoward the end of the cylinder and thus displacing and expelling the remaining burned gases.

'Ihe portion of member il to the left of ribs 3i, as viewed in Figure 4, iswater Jacketed and ls closed at each end by a removable plate 35. The left end of member Il, as viewed in Figure 3, is flat vand has secured thereto a water-Jacketed elbow Il to the upper end of which is secured a neck 31 opening into an exhaust manifold Il. This manifold also is preferably water-jacketed. The elbow 36 defines, with the adjacent portion of belt member il, an exhaust passage il. Member Il is provided, adjacent its left end as viewed in Figure 3, with inwardly projecting upper and lower lands 46 and 4I, respectively, denning a constriction 42 through which throat portion Il of the exhaust passage opens into the main portion ot this passage. The upper series of exhaust ports 26 open into the upper portion of throat portion 43 and the lower series of exhaust passages 21 open into the lowerportion of the throat portion 45.

Belt member 66 is provided, at the inner end of throat portion Il, with vertically extending thickened weh or bridge elements 46, one of which is shown in section in Figure 3, these elements being disposed between the

exhaust ports

26 and 21 of the upper and the lower series, so as not to interfere with exhaust therethrough of the burned gases. Each element l5 is cored out to provide a passage 46 for flow therethrough of cooling water, and is also provided with an opening accommodating a stud l1 which screws into an entablature ll, the studs passing through a clamping ring 46 seating upon port boss 25 for securing the cylinder Il in position. This means of mounting and securing the cylinder is disclosed more in detail in my above identified copending application for Internal combustion engine, led January 7, 193'?, Serial No. 119,422, and need not be further described nor illustrated here, it sumcing to note that the cylinder is mounted and secured in a suitable manner and that the port member III is of a character to accommodate the cylinder securing'xneans.

At its left end, as viewed in Figures 3 and 4, the port belt member is provided, midway of its height and at each side, with a horizontally extending semi-cylindrical recess. Elbow 36 is bolted or otherwise suitably secured to the left end of port belt member 66 and is provided, at its inner end, with two semi-cylindrical recesses complementary to the recesses in the member 36 and defining @therewith cylindrical openings each of which receives a collar 56 (Figure 5). This collar is provided, at its inner end, with a flange 5i seating in

recemes

52 and 53 in the inner faces of members 66 and 66, respectively, and is provided at its outer end with a :Bange 54 which seats against the outer end faces of members 36 and. I6, collar 66 being thus held against endwfse movement. Collar 66 is further provided, at its inner end, with an inwardly projecting flange 66 defining a circular opening which receives a stub shaft 56 extending :from

the end of a rotary valve 51, secured to shaft 56 in a suitable manner, preferably by casting the valve about the shaft so as to be, in effect, integrally united therewith. It will be understood that valve 51 is provided, at each end, with a stub shaft 56 and is supported by these stub shafts for rotation on a horizontal axis normal to the cylinder axis and parallel to the axis of crank shaft i9. A flanged sleeve 58 is bolted to the end faces of

members

30 and 36 and carries ball bearings 59, of known type, through which stub shaft 56 passes and which support the stub shaft for rotation.

The valve 51 is of symmetrical formation andv comprises three Vanes 60 which are of uniform width and are spaced apart. The vanes ill cooperate with lands 40 and Il for controlling the exhaust passage 39, during rotation of the valve, which is continuously rotated during operation of the engine at two-thirds crank shaft speed, in a manner which will be hereinafter described. Vanes l0 are of such size that slight clearance is provided between the vanes SII and the lands 46 and Il as well as between the ends of the vanes and the adJacent end walls of

members

36 and 36, to accommodate expansion of the valve, these clearances being so slight, however, as not to permit of objectionable leakage of exhaust gases or air. I provide a. special labyrinth packing effective to prevent objectionable leakage of the exhaust gases about the stub shaft 56. This packing is shown in Figure 5. Two series of cast iron rings 6I and 62 are disposed within collar 56 in alternate relation, rings 6I fitting closely, but not tightly, about stub shaft 56 and being loose in the collar 50, rings 62 fitting closely, but not tightly, in the collar 50 and being loose about the stub shaft 56. The lateral faces of the rings are flat and seat one against the other, axial movement of the rings in one direction being limited by flange 55 and axial movement of the rings in the other direction being limited by a ring 63 mounted upon the stub shaft 56 adjacent the ball bearings 55. In the event of exhaust gas entering collar 50, the pressure of this gas holds the rings seated one against the other which, in conjunction with the labyrinthine path through which the gas must travel in order to reach the outer end of collar 56, effectively prevents escape of any appreciable amount of exhaust gas about the stub shaft 56. Since the rings 6I do not nt tightly about stub shaft 56 these rings do not rotate with the stub shaft, though the rings 6| and 62 may creep. Any slight misalignment of the stub shaft 56 is accommodated by radial movement 0f the rings 6I and, due to this movement of the rings, but little wear of the rings or of the stub shaft occurs.

It will be understood that there is one exhaust valve for each cylinder, there being, in the engine illustrated, three exhaust valves since there are three cylinders. The valves 51 are disposed coaxially, as in Figure 4, with their common axis parallel to the engine crank shaft. These valves are connected together for rotation as a. unit, by coupling means which, ln itself, is of known type. One oi the couplings is shown in Figure 5. It comprises two sprocket wheels 65 keyed upon the adjacent ends of two valve stub shafts 56 by keys 66, and confined against endwise movement between the inner raceways of ball bearings 56 and headed screws 61 threading into the ends of the stub shafts with their heads seating in recesses in the sprockets. The sprockets 66 are connected together by a sprocket chain 66 having cross pins 68 which seat snugly between the teeth 10 of the sprocket wheel. One pin 89 of the chain is made removable so that by removing the chain rotaryv movement may be imparted to either valve independently of the other, thus rendering possible relative timing of the valves. After the desired adjustment has been made, the chain is replaced and thereafter the valves rotate together as a unit. It will be understood that in making the desired' adjustment of a valve. the chains of the couplings at both ends of the valve are removed and, after the adjustment has been made, replaced. The coupling is enclosed within an oil retaining housing 1| formed in two sections secured together in a suitable manner, conveniently by bolting. The ends of housing 1| extend about the outer ends of sleeves 58 secured to adjacent pairs of

members

30 and 36, and t tightly about felt sealing rings 12 mounted in circumferential grooves in sleeves 58, adjacent the outer ends thereof, for effecting oil-tight seals between casing 1| and the sleeves.

Itis desirable to make the valve and sprocket units, each comprising a valve and its associated sprocket wheel, identical for the sake of interchangeability and convenience in assembling. This I accomplish by proper selection of the number of teeth on the sprocket wheels. The valves are rotated at two-thirds crank-shaft speed, as will be explained presently. Ii N equals the number of cylinders oi' the engine, and n equals the number of teeth on each sprocket wheel. then n should equal 1.5 N, or a multiple thereof. For example, for a six cylinder engine the sprocket wheels 65 may have either nine or eighteen teeth, and for a ve cylinder engine the sprocket wheels may have fifteen teeth.

The valves 51 are continuously rotated as a unit from the engine crank shaft I8 at two-thirds engine speed. Referring to Figures 1, 2 and 6, a housing 13 is suitably mounted at one end of the engine and supports a gear train 14 driven from crank shaft I8 by means of a gear 15 secured on the crank shaft. Gear train 14 drives, through a gear 16 and a sprocket 11, a sprocket chain 18 passing over idlers 19 and 8D, the latter being carried by a chain tightener 8| of known type. Chain 18 passes through an opening 82 at the left upper portion of housing 13 and about a sprocket wheel 83 mounted on a stub shaft 84 rotatably supported in a supplemental housing 85 suitably secured, as by bolting, to housing 13. A'

closure cap 86, fitting into a corresponding opening in the outer end of housing 85 and bolted to the latter, carries ball bearings 81 which rotatably support the outer end of shaft 84, an abutment member or nut 88 screwing upon this end of the shaft and contacting the inner raceway of the ball bearings. A iiangedsleeve 89 ts into a corresponding opening in the inner end of housing 85 and is bolted to the latter, this sleeve carrying ball bearings 90 which rotably support stub shaft 84 adjacent the inner end thereof. The inner end of stub shaft 84 is coupled to the adjacent end of the stub shaft of the adjacent valve 51 in the same manner in which the stub shafts of the valves are coupled together. 'I'he ratio of the gear train 14 is such that stub shafts 84, and accordingly the valves 51, are driven at two-thirds engine speed.

Sprocket wheel 83 has a ring member 8| secured to one side face thereof concentric therewith. Member 8| is serrated internally for engagement with a, cooperating serrated flange 92 formed integrally with stub shaft 84 for securing the sprocket wheel 83 in rotary adjustment relative to the stub shaft. Inwardly beyond ring member 8| the sprocket wheel 83 is confined between flange 92 and a flanged ring 93 fitting about stub shaft 84 and secured to flange 92 by cap screws 84. By removing the cap screws 84 sufliciently to permit of sprocket wheel 83 being moved away from flange 82 a sulcient distance to disengage ring member 8| from flange 82, the sprocket wheel is disengaged from the shaft and the latter may then be turned relative to the sprocket wheel, thus permitting of simultaneous and similar rotary adjustment of all of the valves 51 relative to the sprocket wheel. 'I'his provides simple and convenient means for effecting desired rotary adjustment of the valves as a unit. After the desired adjustment has been made the cap .screws 84 are tightened up and the sprocket wheel is secured to the stub shaft 84 for rotation therewith as before. Housing 85 is provided with a removable cover 95 bolted or otherwise suitably secured thereto, by means of which ready access may be-had to the interior of the housing.

Referring to Figure 4, a flanged cap member 88 is bolted or otherwise suitably secured to the outer end faces of port belt member 30 and elbow 36 associated with the cylinder Il most remote from stub shaft 84. This cap member may be provided with ball bearings similar to those shown in Figure 5 for rotatably supporting the stub shaft at the outer end of the valve 61 most remote from stub sh aft 84, it being understood that this stub shaft also has associated therewith labyrinth sealing means similar to the means shown in Figure 5.

Since vanes 60 of the respective valves 51 are spaced "l apart, and the valves are driven at two-thirds crank shaft speed, each valve is turned into position to close the exhaust passage once during each of crank shaft rotation. It may be assumed, for purposes of explanation, that in Figure 3 piston I2 is in its upper position of maximum compression, fuel has been injected through nozzle 20, and combustion has occurred, the piston being about to start on its downstroke. It will be noted that the upper series of exhaust ports 26 are closed by the piston, the lower series of exhaust ports being uncovered as well as the series of inlet ports 28. The valve 51 is in open position with two of the vanes 68 thereof spaced from the lands 48 and 4| and dening therewith slots through which the burned gasesl of combustion, occurring during the upstroke of the piston, readily escape into the main exhaust passage 39. During the latter portion of the upstroke of piston i2, exhaust ports 21 are uncovered, the burned gases flowing therethrough into throat 43 and thence into the main exhaust passage 38. The inlet ports 28 are then uncovered and scavenging and charging air enters the cylinder through ports 28, scavenging the cylinder and charging it with air. In* the succeeding stroke the piston I2 moves downward and when it reaches the dotted line position closes inlet ports 28 and, at the same time, two vanes 60 of the valve 51 pass onto the lands 40 and 4|, thus Vclosing the exhaust passage. The lands 40 and 4| are of such length that the exhaust passage remains closed until piston I2 reaches the position in its downward travel at which it covers the exhaust ports 21, at which time the vanes of the valve pass oi of the lands, opening the exhaust passage. In this manner the exhaust passage is closed by the time the inlet ports 28 are closed, preferably simultaneously with the closing of these ports, and is maintained closed until the exhaust ports 21 are closed. This eiIectively prevents escape of air from the cylinder, below the piston, at the start of the compression stroke, which assures a maximum air charge with increased emciency in operation of the engine.

In the continued downstroke of piston i2 the exhaust ports 26 are uncovered and thereafter the inlet ports 28 are uncovered, the valve 61 continuing in open position until the cylinder above the piston has been scavenged and charged with air. In the return upstroke of the piston the inlet ports 2l are closed, valve 51 being then in position to close the exhaust passage and continuing in this position until the exhaust ports 26 have been closed, thus preventing the escape of air at the start of the upstroke, thereby increasing the charge of air in the cylinder.

While the exhaust and inlet ports of the cylinder are preferably arranged in the manner shown and described, for mechanical and other reasons, they may be otherwise suitably arranged, so long as the arrangement of `the ports is such as-to accomplish the objects of my invention. The valves may be driven in any suitable manner other than that illustrated and described, by way of example. It will be noted that the events occurring within the cylinder, with respect to scavenging and charging with air, are controlled by a single valve. The valve used is of uniform diameter and symmetrical formation, which is advantageous in eliminating diiliculties due to unequal expansion and contraction. This valve is continuously driven at relatively low speed, which is mechanically advantageous `for obvious reasons. Since the vanes of the valve are equally spaced, the gas pressure forces acting on the valve are always in balance, thus avoiding transmission of any unbalanced moments to the valve driving means. A further advantage of the symmetrical section of the valve is that it presents a beam structure which is equally stiff under the action of gas forces acting at any angle about the circumference of the valve.

Changes in construction and arrangement of parts of my invention may be resorted to, without departing from the field and the scope of the same, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred form only of my invention is disclosed.

I claim:

1. In a two-cycle internal combustion engine, a cylinder and a piston operating therein, said cylinder having piston controlled exhaust and inlet ports, means defining exhaust and inlet passages leading from and to said exhaust and inlet ports, and means comprising a symmetrical three-vane rotary valve of beam cross-section and cooperating lands controlling said exhaust -passage and effective for closing it substantially simultaneously with closing of said inlet ports and maintaining it closed until said exhaust ports are closed.

2. In a two-cycle double acting internal combustion engine, a cylinder `and a piston operating therein, said cylinder being provided at its midportion with upper and lower exhaust ports and inlet ports between said upper and lower exhaust ports, all of said ports being controlled by said piston, means defining exhaust and inlet passages leading from and to said exhaust and said inlet ports, and means comprising a single threevane rotary valve and cooperating lands controlling said exhaust passage and eiective for closing it substantially simultaneously with closing ot said inlet ports and maintaining it closed until said exhaust ports are closed, the-vanes oi.' said valve being symmetrical and equally spaced and said valve being of beam cross-section.

3. In a two-cycle internal combustion engine, a cylinder and a piston operating therein, said cylinder being provided at one side of its midportion with a series of exhaust ports and at the opposite side of its midportion with a series of inlet ports, all of said ports being controlled by said piston, means deilning exhaust and inlet passages leading from and to said exhaust and inlet ports, and means comprising a single valve rotated at two-thirds engine speed and cooperating lands controlling said exhaust passage and effective for closing it by the time said inlet ports are closed and maintaining it closed until said exhaust ports are closed, said valve having three equally spaced symmetrical vanes and being oi! beam cross-section.

4. In a two-cycle double acting internal combustion engine, a cylinder and a piston operating therein, said cylinder being provided at one side of its midportion with a series of exhaust ports and at the opposite side of its midportion'with a series of inlet ports, all of said ports being controlled by said piston, a member extending about the midportion of said cylinder and defining an exhaust passage comprising a throat portion extending from said exhaust ports and provided with two lands, and a rotary valve of beam crosssection continuously driven at two-thirds engine speed and provided with three equally spaced vanes cooperating with said lands for closing said exhaust passage by the time said inlet ports are closed and maintaining it closed until said exhaust ports are closed.

5. In a two-cycle double acting internal combustion engine, a cylinder and a piston operating therein, said cylinder being provided at one side of its midportion with a series of exhaust ports and at the opposite side of its midportion with a series of inlet ports, all of said ports being controlled by said piston, a member extending about the midportion of said cylinder and deiining exhaust and inlet passages leading from and to said exhaust and inlet ports, said exhaust passage comprising a throat portion extending from said exhaust ports and said member being provided with two lands at the outer end of said throat portion, a rotary valve of beam cross-section having three equally spaced vanes cooperating with said lands for controlling said exhaust passage, and means for continuously driving said valve at two-thirds engine speed and in timed relation to the engine effective i'or closing said exhaust passage by the time said inlet ports are closed and maintaining it closed until said exhaust ports are closed.

6. In a two-cycle internal combustion engine, a plurality of cylinders and pistons operating therein, each of said cylinders being provided at its midportion with piston controlled exhaust and inlet ports, means dening'exhaust passages each comprising a throat portion leading from the exhaust ports of the respective cylinders and provided with lands, coaxial rotatable valves cooperating with said lands for closing the respective exhaust passages by the time the inlet ports of the associated cylinder are closed and maintaining said exhaust passage closed until the exhaust ports of said cylinder are closed, and means for continuously driving said valves as a unit in timed relation to the engine, said driving means lid aisaovs comprising adjustable couplings between said valves permitting individual rotary adjustment thereof.

7. In a two-cycle internal combustion engine, a plurality of cylinders and pistons operating therein, each of said cylinders being provided at its midportion with piston controlled exhaust and inlet ports, means dening exhaust passages each comprising a throat portion leading from the exhaust ports of the respective cylinders and provided with lands, coaxial rotatable valves cooperating with said lands for closing the respective exhaust passages by the time the inlet ports of the associated cylinder are closed and maintaining said exhaust passage closed until the exhaust ports of said cylinder are closed, the common axis of said valves being substantially normal to the cylinder axes and parallel with the engine crank shaft, and means for continuously driving said valves as a unit in timed relation to the engine, said driving means comprising adjustable couplings between said valves permitting individual rotary adjustment thereof.

8. In a two-cycle internal combustion engine, a plurality of cylinders and pistons operating therein, each of said cylinders being provided at its midportion with piston controlled exhaust and inlet ports, means defining exhaust passages each comprising a throat portion leading from the exhaust ports of the respective cylinders and provided with lands, coaxial rotatable Valves cooperating with said lands for closing the respective exhaust passages by the time the inlet ports of the associated cylinder are closed and maintaining said exhaust passage closed until the exhaust ports oi said cylinder are closed, the common axis of said valves being substantially normal to the cylinder axes and parallel with the engine crank shaft, and means for continuously driving said valves as a unit in timed relation to the engine, said driving means comprising an adjustable driving connection permitting simultaneous and similar rotary adjustment of the valves and adjustable couplings between said Valves permitting individual rotary adjustment thereof.

9. In a two-cycle internal combustion engine, a plurality of cylinders and pistons operating therein, each of said cylinders being provided at its midportion with piston controlled exhaust and inlet ports, means dening exhaust passages each comprising a throat portion leading from the exhaust ports of the respective cylinders and provided with lands, coaxial rotatable valves cooperating with said lands for closing the respective exhaust passages by the time the inlet ports of theassociated cylinder are closed and maintaining said exhaust passage closed until the exhaust ports of said cylinder are closed, the common axis of said valves being substantially normal to the cylinder axes and parallel with the engine crank shaft, adjustable couplings between the valves permitting individual rotary adjustment thereof, a stub shaft coaxial with said valves, an adjustable coupling between said shaft and one of the valves, a driven member mounted on said shaft, means for securing said member to said shaft and permitting of relative rotary ad- .iustment between the latter and said driven member, and means for driving said driven member from the engine crank shaft.

EDVIARD S. DENNISON.