US1376093A - Steam-engine valve - Google Patents

Description

' Ei. H. HOLMES. STEAM ENGINE VALVE. APPLICATION HLED JULY 21, 1919.

1,376,093 Patented Apr. 26, 19210 Z INVENTOR UNHT fiTTS ERNEST H. HOLMES, 0F POINT PLEASANT, WEST VIRGINIA STEAM-ENGINE VALVE.

Specification of Letters Patent.

Patented Apr. 26, 1921.

Application filed July 21, 1919. Serial Ito. 312,140.

new and useful Improvement in Steam-Engine Valves, of which the following is a full, clear, and exact description, reference being had to the accompanying drawing, forming part of this specification, in which- Figures 1 and 2 are longitudinal vertical sections of a steam engine cylinder and valve mechanism embodying my invention, the two views showing the moving parts in different positions.

The object of my invention is to provide a piston valve for slow speed steam engines, which will prolong the period of expansive work in the cylinder, by not opening the cylinder exhaust until at or near the end of the expansion stroke; and which will, at the same time, reduce the compression by not closing the exhaust until at or near the end of the exhaust stroke; thus increasing the ethciency of the engine with respect to its steam consumption.

My invention relates particularly to reciprocating piston valves which admit the steam to the cylinder past their inner cutting edges and exhaust past their outer cutting edges or ends; and it consists in making the valve in three parts, viz; a main valve, rigidly connected to the valve stem, and which valve opens and closes the ports connecting the cylinder with the valve chest and controls the admission, cut-ofi and compression; and two auxiliary valves, mounted loosely on the valve .stem between actuating collars, outside the ends of the main valve, and which auxiliary valves open and close auxiliary ports connecting the exhaust spaces or ends of the valve chest with the exhaust pipes or ports, said auxiliary valves thereby controlling the release of steam from the cylinder.

The nature of my invention will be best understood by reference to the accompanying drawing in which I have shown a preferred embodiment thereof and which will now be described, it being premised, however, that various changes can be made in the details of construction and arrangement of the parts without departing from the spirit and scope of my invention as defined in the appended claims.

In this drawing, the numeral 2 designates a steam engine cylinder and 3 the piston therein. 4 is the steam chest connected by a port 5 withone end of the cylinder chamber and by a similar port 6 with the opposite end of the cylinder chamber. The chamber of the steam chest is provided with an end extension 7 at each end, and each of these extensions has an exhaust port 8 and 9, respectively, located beyond the ports 5 and 6 10 deslgnates a main piston valve having a head at each end portion and between which heads is located the steam inlet port 11. This piston valve is rigidly connected to the valve stem 12 which may derive its motion.

from any suitable eccentric or link device which may be most suitable to the particular service for which the engine is designed. As will be noted, this valve is arranged to take steam from the inside and exhaust at the ends.

13 and 14 are the two auxiliary valves, loosely mounted on the valve stem 12, between the actuating collars 15. 16 designates the exhaust ports through the auxiliary valves. These auxiliary valves fit the bore of the extensions or exhaust spaces 7 and control the exhaust from such spaces to the ports 8 and 9.

It will be noted from Fig. 1, which shows the main valve in its mid-position, that such valve has positive steam lap, but negative exhaust lap which is so proportioned that the exhaust closes at or near the end of the exhaust stroke. This reduces the compression, but a valve proportioned in this way when moving in the opposite direction will open the exhaust and release the steam from the cylinder too early in the expansion stroke to obtain the best efliciency. The auxiliary valves are provided to overcome this diiiiculty. The outer edges of these valves are the cutting edges which open and close the auxiliary ports; and the locations of the actuating collars on the valve stem are so chosen that when the main valve closes the exhaust, the auxiliary valve on the same end (which, when moving in this outward direction is pushed ahead by the inner collar) has the same negative lap as the main valve and therefore leaves the cylinder port open; that is, the two valves close their respective ports simultaneously and the auxiliary valve does not cause any more compression than does the main valve. When, however, the valve stem is moving in the opdelayed.

posite direction, the main valve opens the exhaust very early in the expansive stroke, butthe auxiliary valve is now being pulled along by the outer actuating collar and has lagged behind the main valve by an amount equal to the lost motion between the valve and the two actuating collars. It, therefore, opens the auxiliary port later than the main valve opens the cylinder port, and sufficient lost motion is allowed so that the auxiliary valve does not open the auxiliary port until at or near the end of the expansion stroke. In this manner, the release of the steam is In other words, the auxiliary valve has negative lap when closing but positive lap when opening the auxiliary Jort. 1 In Fig. 1 the three valve parts 10, 13 and 1 1- are all traveling in the same direction, as indicated by the arrow, and the valve 13 has the same negative lap in relation to port 8 as the main valve 10 has in relation to the port 5. On the other end of the cylinder, where the exhaust is being opened the valve 14 has positive lap in relation to port 9, while the exhaust lap of the main valve has positive lap.

The operation may be set forth more in detail as follows:

In Fig. 1 the piston is traveling as indicated by the arrow, and the steam in the left hand end of the cylinder is being exhausted through port 5, past valve 10, through ports 16, past valve 13, through portS. The valves 10 and 18 do not close their respective ports until. the piston 3 is nearly at the end of its stroke and therefore only a very slight amount of compression occurs.

In the right hand end of the cylinder, the steam is working expansively and the main valve 10 has already opened ports 6, but the auxiliary valve 14, being moved by the outer actuating collar has not yet opened the port 9, and the release does not occur until this valve opens, which is near the end of the stroke.

The complete cycle of operation is, therefore, as follows for say the left end of the cylinder:

W hen the piston 3 is at the extreme left, the valve 10 has moved far enough to the left from its midposition to uncover a small amount of the port 5 on the steam side, and steam is flowing into the cylinder as the piston moves toward the right. When the piston has moved to the position shown in 2, the valve has reached its extreme travel to the left and is just starting to return. As the piston travels on the valve 10 closes port 5 and the steam is cut oil. A. little later valve 10 opens port 5 to the exhaust side, the conditions and position of valves for the left hand end then being similar to those shown on right hand end of Fig. 1. This, however, does not release the steam from the cylinder, the auxiliary valve being closed.

Traveling still farther toward the right, the auxiliary valve 13 opens port 8 and release occurs. The piston 3 is then near the right hand end of its stroke, moving toward the right. /V hen the valvehas reached its extreme position to the right, the auxiliary and cylinder ports are both wide open and the piston is on its return stroke toward the left, the conditions and positions of valves for the left hand end then being similar to those shown on the right hand end of Fig. 2. The main valve 16 now starts the return stroke toward the left, the auxiliary valve remaining stationary until the lost motion between the inner collar and the valve has been taken up, when it commences to move with the main valve, and the two valves close their respective ports simultaneously, and compression begins. This is very near the left end of the stroke of the piston 3. When the piston reaches the end of the stroke the cycle is completed. The cycle for the right hand end of the cylinder is the same as for the left end.

The advantages ofmy invention will be readily understood, since it provides a simple, eilicient and reliable valve arrangement for steam engines, which prolongs the period of expansive work, by delaying the release, and that at the same time reduces the compression by delaying the closing of the exhaust valves, due to great negative lap on the exhaust side, and which negative lap could not be used to advantage without the means provided for delaying the release.

I claim:

1. The combination with a steam engine cylinder and its valve chest, the latter having an extension chamber at each end provided with an exhaust port, said ports constituting the only means of escape for the exhaust from the cylinder, and the cylinder having a combined inlet and exhaust port at each end portion thereof communicating with the .valve chest and with one of said chambers, of a mechanically actuated piston valve for controlling the said ports, said valve consisting of a main portion rigidly connected to its valve stem, and two auxiliary valves arranged to open and close the said exhaust ports from the extension chamber, said valves being loosely mounted on said stem and arranged to have negative lap when closing and positive lap when opening their respective ports, substantially as described.

2. The combination with a steam engine cylinder and its valve chest, the latter having an extension chamber at each end provided with an exhaust port, said ports constituting the only means of escape for the exhaust from the cylinder, and the cylinder having a combined inlet and exhaust port at each end portion thereof communicating with the valve chest and with one of said chambers, of a mechanically actuated piston valve for controlling the said ports, said valve consisting of a main portion rigidly connected to its valve stem and admitting steam to the cylinder past inner cutting edges thereof and exhausting steam from the cylinder past outer cutting edges thereof, and two auxiliary valves arranged to open and close the said exhaust ports from the extension chambers, said valves being loosely mounted on said stem and arranged to have negative lap when closing and positive lap when opening their respective ports, substantially as described.

3. The combination with a steam engine cylinder and its valve chest, the cylinder having a combined inlet and exhaust port at each end portion communicating with said chest, and said chest having an extension chamber at each end provided with an exhaust port, of a mechanically actuated valve for controlling said ports, said valve having a main portion which directly controls the ports leading from the steam chest into the cylinder, and also having auxiliary valve members actuated by the movement of the main valve portion and arranged to control said exhaust ports from the extension chambers, said auxiliary valves having a negative lap when closing and a positive lap when opening their respective ports, substantially as described.

4. The combination with a steam engine cylinder and its valve chest, there being a port connecting each end portion of the valve chest to the corresponding end of the cylinder, and the valve chest having end extensions beyond said ports, each of said extensions having an exhaust port, of a mechanically actuated main valve in said chest, and auxiliary valves mounted one at each end of the main valve and on the stem of said main valve and having a lost motion connection therewith, said auxiliary valves being located within said end extensions and controlling the exhaust ports, substantially as described.

In testimony whereof, I have hereunto set

Images