US1336344A - Reversing valve-gear - Google Patents

Description

W. E. BROWN.

REVERSING VALVE GEAR.

APPLICATION FILED JAN. 16, I918.

Patented Apr. 6, 1920.

/NVEN TOR WILLIAM E. BRO'WN, OF DETROIT. lvIICT-IIG-AIFT, ASSIGNGR, BY DIRECT AND MESNE ASSIGNMENTS, TO BROWN ENG. rIYEEFJII-TG GOIEPANY, OF DETROIT, MTCHIGAN, A

CORPORATION OF MICHIGAN.

REVERSIll-Gr VALVE-GEAR.

Application filed January 16, 1918.

To all whom it may concern:

Be it known that I, VJILLIAM BROWN, a citizen of the United States, and resident of Detroit, lVayne county, Michigan, have invented new and useful lmprovements in Reversing valve-Gears, of which the following is a description, reference being hat to the accompanying drawings, which are a part of this specification.

This invention has for its object to provide a reversing valve gear for steam engines operating from a single crank pin or eccentric, and having a positive reversing motion with an even distribution of steam to each end or" the cylinder, and with a quick open ing and closing of the ports by a valve having a short travel and giving a constant port opening during the most effective power stroke of the piston.

Another object of the invention is to provide such a reversing valve gear that may be adjusted to produce an earlier or later cut-off allowing any rate of expansion in the cylinder with corresponding economy of operation.

With the above and other objects in view the invention consists in the reversing valve gear, its parts and combinations of parts as herein claimed and all equivalents.

Referring to the accompany ig drawings in which like characters of reference indicate the same parts in different views:

Figure l is a sectional view of a steam engine provided with a reversing valve gear constructed in accordance with this invention, the parts being shown in the positions assumed by them at one end of the piston stroke; and,

Fig. 2 is a similar view thereof with the parts in the position assumed by them when the piston is in the middle of its stroke.

In these drawings 10 indicates a steam engine cylinder in which a piston 11 operates, the piston rod 12 being connected as usual to a cross head 13 traveling in suitable ways. A pitman 1% connects the cross head 13 with a crank 15 on a crank shaft 16 to impart rotation thereto.

A valve chest 17 contains a slide valve 18 controlling ports 19 and 20 leading to the opposite ends of cylinder 10 so as to control connection between them and a live steam port 21 and an exhaust steam port 22. A valve stem 23 is connected with the Specification of Letters Iatent.

Patented Apr. 6, 1920.

Serial No. 212,057.

valve 18 and slidably passes through a static-nary guide 2%.

It is the purpose of the valve gear of this invention to operate the valve 18 by the movements of the crank shaft to automatically connect the ports 19 and 20 with the live steam port and the exhaust respectively to maintain the reciprocating ac tion of the piston, but more particularly to effect the timing thereof in such a. manner 'as to vary the period of expansion between the cut-oil of the live steam and the opening of the exhaust and thereby obtain greater efficiency.

T he valve rod 23 has a lap and lead lever fulcrumed thereon with a link connection at each end for imparting motion thereto from the crank shaft, one link con nection being direct from a crank or eccentric of the crank shaft and the other being indirect or through a reversing link. and the arrangement being such that with both link connections operating in the same direction the valve rod is moved therewith, and when operating in opposite directions the valve rod is moved in a direction depending upon the differential action thereof.

The direct link connection is made by one arm or" a lever 26 pivotally connected with the longer lower end of lever 25 and mounted on a wrist pin 27 on an arm 28 extending toward the center of the crank shaft from the end of crank 15.

The indirect link connection for the other end of lever 25 is made through a reversing link 29 mounted to oscillate on a trunnion 30 and having a laterally extending arm 31 connected by an eccentric rod 32 with a downwardly extending arm 33 forming the other arm of the lever 26. The lever 26 with its rigid angular arm 33 is thus a bell crank lever fulr rumed on the wrist pin 27 and taking part in both of the link connections between the wrist pin 27 and the opposite ends of the lap and lead lever 25. i3. radius rod forms the connection between the reversing link 29 and the upper shorter end of lever 25, such radius rod 34: being pivotally connected to the lever 25 and having pivotal connection with the sliding block 35 which is adjustable in the arc-shaped slot of the reversing link 29. The adjustment of the block in the reversing link 29 so as to carry it to any desired position above or below the pivotal support 30 to change the degree or direction of the movement imparted. by the reversing link to the connecting rod 3% is accomplished by means of a reversing lever 36 fulcrumed at 37 and having an arm 38 carrying a guide 39 through which the end of the connecting rod 3 1- slidably travels. After releasing the lock 40 of the reversing lever 36 from engagement with its notched quadrant etl, said reversing lever may be swung as from its full line position in Fig. l to its dotted line position and thus lift the end of the radius rod to carry the block 35 from the lower end of the slot of reversing link 29 to the upper end to reverse the direction of movement of radius rod 34L in any given movement of the reversing link 3i. Vith the crank at dead center as shown in Fig. 1., the pivotal connection of the radius rod 34 with lever 25 is the center of the are formed by the slot of reversing link 29 so that in' this position of the parts the change in position of the reversing lever and rod 34: is accomplished without movement of the other parts.

The disposition of the parts is such that the influence of lever 26 on lever 25 is the result of the travel of wrist pin 27 as measured in a horizontal direction, whereas the influence of the radius rod 34: on lever 25 is the result of the travel of wrist pin 27 as measured in a vertical direction, as modified by the adjustment of the block 35 in the reversing link slot. The influence on the lever 25 exerted through the reversing link is also modified as to the timing of the action by the fact that the crank action due to the swinging of bell crank arm 26 on its fulcrum 27 with the corresponding swing of arm 33 tends to accelerate the movements of the reversing link produced by the wrist pin 27 at one part of the cycle of operation and to retard them at another.

With the reversing lever 36 in its central position the pivotal connection of the block is in register with the pivotal connection of the reversing link 31 so that radius rod 34L has no motion, and the slide valve influenced by the direct link connection 26 alone will, when the engine is turned over, be reciprocated just the lap and lead, the lead being always on dead center.

With the reversing lever thrown to the right or the left, however, the influence of the direct link connection 26 on the valve will be augmented by the influence of the reverse link 31 and in such a manner that these two influences at times work together to produce a quick throw of the valve, and at other times work in opposition to retard the movement of the valve.

lVith the crank 15 in the position shown in Fig. l and the reversing lever in the position shown in full lines so that the engine is running in the direction of the arrow, the valve 18 is just admitting steam to the left end of the cylinder, the position of the lever 25 determining the amount of lead. As the crank rises above the center line and moves toward the right, it causes the reversing link 31 to swing on its trunnion and throw the radius rod 34. to the left, thus sliding the valve 18 to its full open position on the port 39 leading to the left end of the cylinder. This movement is promptly made notwithstanding the tendency of link 26 to operate in the opposite direction, for the rising movement of the crank which inruences the reversing link to move the valve to the left is its maximum degree of effectiveness at the beginning of the stroke of the piston. while the movement of the crank to the right is at its minimum degree of effectiveness, and the influence of the action through the reversing link strongly predominates. The valve remains in its position open to the left end of the cylinder until the end of the quarter revolution by the crank or the position of the parts shown in Fig. 2. The valve is practically stationaryfrom the time it is fully opened until the end of the first quarter turn of the crank, for the two link connections for. the lap and lead lever 25 act equally in opposite directions to neutralize each other. The waning influence of the reversing link as the crank approaches its highest position is compensated for by the swing of the lower end of link due to its connection with the bell crank arm of the lever 26. This swing carries the end of rod 32 nearer to the trunnion 30 and coir sequently increases the swing of the'reversing link'3l and thus assists in neutralizing the effect of the link connection 26. i

As the crank continues to the right from its uppermost position, shown in Fig. 2, the influence of the link 26 and the influence of the reversing link 31 are combined, both acting in the same direction to move the valve to the right to close the port 19 and thus cut off the supply of steam to the left end of the cylinder and permit of the eXpan- I sion'o'f the steam therein for the remainder of'the stroke of the piston. While the lever 26 continues to move in the same direction as before the reversing lever 31 reverses its direction of swing when the crank passes its uppermost position and throws the radius rod 34; to the right and as both ends of the lap and lead lever 25 aremoved in the same direction, the valve is quickly shifted to its closed position. The ,iproinptness with which this is effected, however, depends upon the amount of throw ofthe connecting rod 34 by the swinging action of the reversing lever 31 and as this is dependent upon the position of the block 35 in the slot of the reversing link, the position of the reversing lever will determine the point of cut-oft and correspondingly the relative period or" expansion.

The rapid travel of the valve to the cut-ofl position continues through its lap travel and when the piston is at the right end of the cylinder, with the crank at its right center, the valve is opened to the right port 20 just the right lead. In this position the reversing link 31 will again be in its middle position and a further rotation of the crank causes it to continue the throw of the radius rod 34, to the right, while the reversal of direction of the piston causes the link 26 to move to the left. The influence of the reversing link 31 predominates over the influence of the link 26 as before to fully open the valve to port 20 for the right end of the cylinder be cause of the former acting at maximum efiiciency and the latter acting at minimum efiiciency. The bell crank arm 33 of link 26 again compensates for the reduction in efliciency of the action on the reversing link 81 as the crank approaches its lowermost position to maintain the neutralizing effect on the lap and lead lever 25 to hold the valve in its full open position, the inclined position of the link 26 causing said arm 33 to swing away from the pivotal connection of the reversing link and augment the swinging movement of the reversing link that causes the radius rod 34 to move to the right.

When the crank passes its lowermost position the reversing link is again reversed in its direction of movement to cause the connecting rod 34 to move to the left and act together with the link 26 moving in the same direction to quickly move the valve to its closed position and cut off the supply of steam to the right end of the cylinder at a point depending upon the position of the reversing lever. On approaching the dead center position, shown in Fi 1, this throw of the valve carries it to the position to open the lead to port 19 at the left end of the cylinder, thus completing the cycle of operation.

It will, of course, be understood that as the valve opens the lead to the port to one end of the cylinder it opens the port to the other end of the cylinder to exhaust.

A change in the position of the reversing lever 36 to carry it to the other extreme position so as to slide the block 35 to the other end of the slot of the reversing link 31 changes the direction of the movement imparted by said reversing link to the radius rod 34 and consequently reverses the direction of rotation of the crank shaft.

With the reversing valve gear of this invention the operation is accomplished by means of a single crank or eccentric, for of course an eccentric may be substituted for the crank shown. The link connections with this crank operating in directions approximately at right angles to each other permits of the accomplishment of a differential action producing quick movements of the valve between comparatively stationary periods without the use of double eccentrics.

The present invention, furthermore, by the two separate link connections between the crank and the lap and lead lever wherein the bell crank connection between them tends to neutralize their resultant eifect upon the valve by augmenting the diminishing influence of one at the time that the opposing influence of the other is approaching its maximum, serves to prolong that period of the valve cycle in which it remains comparatively stationary in its full open position with a corresponding celerity of movement of the valve in the cut-oft.

The invention provides a positive reversing motion with an even distribution of stea m to each end or the cylinder and a quick opening and closing of ports with a nearly stationary valve giving a constant port opening during the most effective portion of the power stroke of the piston.

Any point of adjustment of the block 35 ,above or below the link center will produce .an earlier or later cut-ofi', allowing any rate of expansion in the cylinder with corresponding economy of operation.

Various changes may be made in construc 'tion and arrangement of parts shown without departing from the spirit and scope of the invention and I therefore desire it to he understood that this invention is not limited to any specific form or arrangement of parts except in so far as such limitations are specified in the claims.

lVhat I claim as new and desire to secure by Letters Patent is:

1. A valve gear, comprising a crank shaft, an eccentrically mounted pin thereon, members connected with said pin and extending in directions approximately at right angles to each other, a reversing link to which one member is connected, a lever connected at one end to the other member, a radius rod connecting the other end of the lever with the link. and a valve rod having the lever fulcrumed thereon.

2. In a valve. gear, the combination of a crank shaft, an eccentrically mounted. pin thereon, a lever fulcrumed on the pin, a link, an eccentric rod connecting one arm of the lever with the link, lap and leadlever pivotally connected to the other arm of the first named lever, a radius rod connecting the lap and lead lever with the link, and a valve rod on which the lap and lead lever is tulcrumed.

3. A. valve gear, comprising a crank shaft. an eccentrically mounted pin thereon, a bell crank lever fulcrumed on the pin, a pivotally mounted reversing link, an eccentric rod connecting the reversing link with one Cir bell crank lever, a valve rod having the lap and lead lever fulcrumed thereon, and means ior ad us'tmg the block in the reversing link. at. A valve gear comprising a crank shaft,

an eccentrically mounted pin thereon, a bell crank lever fulcrumed on the :pin, a pivotally mounted reversing link having an areshaped slot, a block slidable in the slot, an eccentric rod connecting the reversing link with one arm of the bell crank lever, a radius rod pivotally mounted on the block, a lap and lead lever pivotally connected at one end to the connecting rod and pivotally connected at the other end to the bell crank lever, a valve rod for the lap and lead lever fulcrumed thereon, a reversing lever, an arm thereon, and a slide on said arm engaging the radius rod for shifting the block in the slot of the reversing link.

5. A; valve gear, comprising a crankshaft, an eccentrically mounted pin thereon, a lever connected with said pin, "an eccentric rod connected with said lever, a pivotally mounted reversing link connected with said rod, a block adjustably mounted in the reversing link, a radius rod pivotally mounted on the block, a lap and lead lever pivotally connected at one end to the radius rod and pivotally connected at the other end to said lever, a valve rod having the lap and lead lever fulcrumed thereon, and means for adjusting the block in the reversing link.

6. A valve gear, comprising -a reciprocating valve rod, a crank shaft having an eccentrically mounted pin, a lap and lead lever fulcruined at an intermediate point on the valve rod and having a link connection with the eccentric pin, a radius rod pivotal ly mounted :on the other end of the lap and lead lever, a pivotally mounted "reversing link, a block slidable in the slot of the reversing link and pivotally mounted on the radius rod, said slot of the reversing link being arc-shaped and in one position of the reversing link being centered on the pivotal connection between the radius rod and the lap and lead lever, a connection between the reversing link and the eccentric pin, and a reversing link connected with the radius rod for sliding the block in the arc-shaped slot of the reversing link.

7. In a valve gear the combination, with a valve rod, of a lap and lead lever connected thereto, a single crank, and linkages connecting said crank with said lever to act together during opening and closing movements of the valve rod and to compensate each other while the valve rod is in its open position.

8. In a valve gear the combination, with a valve fIOCl of a lap and lead lever connected thereto, a driving member, a lever mounted eccentrically intermediate its ends upon said member and connected at one end to said lap and lead lever, a pivoted link, an eccentric rod connecting the other end of said lever with said link, and a radius rod connecting'said link with said lap and lead lever.

In testimony whereof I afiiX my signature in presence of two witnesses.

WILLIAM E. BROWN. Witnesses D. M. 'GHAMBERLIN, URBAN B. MC-INERNEY.

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