US1798816A - Steam engine - Google Patents

Description

March 31, 1931. STEVENS 1,798,816

STEAM ENGINE Filed June 1, 1920 3 Sheets5heet 1 Whig- [NV/ENTOR m ATTORNEY March 31, 1931. R. c. STEVENS 1,798,816

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Patented Mar. 31, 1931 ROBERT C. STEVENS, F ERIE, PENNSYLVANIA STEAM ENGINE Application filed June 1, 1920. Serial No. 385,544.

Uniflow engines are superior in economy of operation to counterflow engines, but in many relations, such as automobiles, they have some disadvantages; as, for instance,

difliculty and inconvenience in starting because of high compression and the trapping of water. The present invention is designed to retain the desirable features of the uniflow engine and provide means avoiding the difiiculties heretofore experienced. Broadly, it

A consists in providing a variable cutoff valve mechanism and system exhausting from the ends of the cylinder at long cut-off and taking the exhaust from the cylinder at points remote from the ends of the cylinder at short cut-oil. In other Words, making the engine operate as to the steam exhausted at the ends of the cylinder on the counterfiow principle with slight compression and effective Water discharge and automatically making the engine upon the shortening of the cut-off operate uniflow engine with its high compression and greater economy. In this I am enabled Without added effort on the part of the operator to obtain the desirable qualities of both types of engine.

In carrying out my invention I prefer to accomplish the results above stated by a valve mechanism having a unitary movement controlling both the admission and exhaust of steam from the ends of the cylinder.

I also preferably utilize a trunk piston operating over intermediate ports, as such a piston, particularly in connection With the end exhaust particularly discharging to a common exhaust passage, has an added economy.

My invention, therefore, consists in these and features and details set forth in the following specification and claims.

The invention is illustrated in the accompanying drawings as follows:

Fig. 1 is a top plan view of the engine, the crank shaft being geared to an axle of an automobile. Fig. 2 is a side elevation of the same.

Fig. 3, an indication card of the engine opcrating at long cut-off with some counterflow movement of steam. V

5 i .Fig. 4, asimilarcard'withthe engine operas indicated by t:

ating at short cut-ofi' and With unifloW movement of steam.

Figs. 5 to 9, inclusive, sectional views showing consecutive positions of valve and piston with the valve operating at long cut-off.

Figs. 5 to 9, inclusive, similar views with the valve operating at short cut-off.

1 marks the engine valve, Q'and 8 steam and exhaust passages controlled thereby. As shown, the valve is driven through thewell known and common Walchaert gear in which 4 is the combination lever actuated through the usual connections from the crosshead 5 and the eccentric c link 6, the control being accomplished in this exemplification by the 5 hand-operated shift rod 7. The engine crank shaft 8 is connected with the axle 9 by atrain of gears 10. a

It will be understood that the invention is not limited to the type of valve gear here shown, nor is it limited to a manually-actuated gear, the only limitation being that it vary the valve travel sufficiently to accomplish the opening and cutting of the end exhaust port at long and short cut-elf. 7

The piston 11 is preferably of trunk piston type and operates the central exhaust port 3, opening the. same at the ends of its stroke and covering the same throughout the remainder of the stroke. The head end port 12 and tail end port 13 lead to passages 2. The exhaust port 3 discharges to the annular exhaust passage 14 and this opens to the center of the valve 1, which, as shown, is of the D valve type exhausting at the center. The ina vention is not limited to this manner of using the D valve nor to a valveof this ty e. The exhaust lap of the valve'is such that at long travel the passages 2 are uncovered and connected With the exhaust passage 14, but a so short travel and cut-oil" does not uncover the passages 2.

The result of this construction upon the operation of the engine can be best understood by a consideration of Figs. 5 to 9 ina5 elusive.

In the series 5 to 9 the valve is driven by the valve gear full travel, as indicated by T, While in the series 5* to 9" the travel is short,

Considering these figures, particularly with relation to the functioning in connection with the head end of the cylinder:

Fig. 5 shows the piston at the extreme head end of the cylinder with the valve in lead position.

Fig. 6 shows the valve wide open, giving steam to the head end of the cylinder'and exhausting from the tail end of the cylinder through the port 13 to the exhaust passage 14 by way of the center of the valve.

Fig. 7 shows the piston advance to the point of cut-E of the valve as shown about 86% of its travel.

Fig. 8 shows the piston, having advanced to the extreme tail end of cylinder, returned to a point where the valve begins to uncover the passage 2 leading from the head end port 12. It will be noted that the main exhaust has been accomplished by the uncovering of the ports 3 by the piston 11 near the end of its advance movement.

Fig. 9 shows the piston at the point of exhaust closure by the valve, the remaining portion of the piston stroke compressing the steam at the head end of the cylinder preparatory to steam admission as at theposi-tion shown in Fig. 5. Note that the port 12 is open to exhaustbetween the positions of Fig. 8andFig.9.

In this series the late cut-off and slight compression assuring a maximum of starting effort and complete water drainage. In the following series the valve travel is, as before stated, short, and there is no exhaust through port 12, and this action is entirely uniflow.

Fig. 5 shows the piston at the extreme head end of the cylinder with the valve at lead position.

Fig. 6 shows the piston advanced to a position with a full opening of the valve. Note that at this extreme position the lap has not uncovered the passage leading from port 13. 1 l

Fig. 7 shows the piston advanced to the point of cut-off by the valve about of the piston travel.

Fig. 8 shows the piston advanced to a position uncovering the exhaust ports 3. It will be noted that in Fig. 7 the piston has not made the turn as in Fig.7. r

Fig. 9 shows the piston on return stroke covering the ports 3, the valvev closing the port 12 against exhaust. Note with the short travel of the valve compression begins with closing of the port 3 by the piston and continuous to the end of the stroke, as the valve does not open the port 12 to exhaust (see Fig. 6 as indicating the closure at extreme position of the valve). Compare this compression with that shown in Fig. 9.

By this means I attain the advantage of securing a powerful working stroke with long admission and smalloco mpression when the engine is first started, thereby enabling it to exert a maximum starting torque, and I secure at high speeds uniflow performance with the attendant early cut-ofi, long expansion, late release, short period of exhaust and high compression, and I attain all of these results without adding any parts to those ordinarily, employed in a single valve engine.

.In ordinary uniflow practice, the length of the exhaust lap 15 is such in proportion to the travel of the valve that the steam port is never open-for exhaust, whereas in my improved construction the length of the exhaust lap is so proportioned to the travel of the valve that, because of long travel at time of starting, the steam port is open for exhaust and on medium or shorter travel; i. 'e., at time of normal running the steam port is not so opened, or at least not opened far enough to prevent the securing of an indicator diagram showing a true uniflow distribution of steam consequently on long travel the engine acts as a counterfiow; that is, the steam passage is utilized also as an-exhaust passage. On shorter travel the engine acts as a =uniflow;

that is, only steam travels through the steamy passages.

Another important advantage obtained by the valve operation described is the case with which wateris removed from the cylinder.

As is well known in ordinary counterfiow en .gines, it is always necessary to first drain the 7 water from the cylinder before starting.

uniflow engines the water is usually drained through the central exhaust ports 3 on the first stroke of the piston.

Since in my present invention the engine starts by operating as a counterflow, it would appear to be necessary to provide the engine with means for draining the cylinder, but such, however, is not the case, because when the engine is being started, that is. when the valve is at its maximum travel T and the engine is acting as a counterflow, the central ports 3'are uncovered on the first stroke, thus at least partly draining the cylinder into the exhaust belt 14, and if water still remains in the cold cylinder this water will be forced out through the steam passage 9., through the interior of the valve 1 and into the exhaust belt 14 on the return stroke ofthe piston.

My improved engine, therefore, is selfdraining and requires no bleeder valves or 7 like devices, but will start cold, even though there be a large amount of water in the cylinder and will rapidly pick up to speed without any indications of water hammer. I

. The trunk piston gives an added economy, in that the wiping of the walls by exhaust steam isavoided. "This is of particular advantage when the auxiliary exhaust leads to the same exhaust passage as the central exhaust, as this results in a momentary inflow and outflow dissipating heat.

What I claim as new is: f-

-1. Inan engine, the combinationef a cylinder ported to receive and exhaust steam at its end and exhaust steam at a point re mote from the end; a piston in the cylinder; a valve controlling the admission and exhaust of steam from the end and varying the point of cut-ofi of the steam as its travel is varied, automatically ett'ecting an end exhaust at late cut-oil and to close the same at early eutoif and means actuating the valve and varying the valve travel through a range throwing the end exhaust into and out of action.

2. In an engine, the combination of a cylinder ported to receive and exhaust steam at its ends and exhaust steam at a point remote from the ends; a piston in the cylinder; a valve controlling the admission and exhaust of steam from the ends and varying the point of cut-off of the steam as its travel varied, automatically effecting end exhausts at late cut-0ft and to close the same at early cut-cit; and means actuating the valve and varying the valve travel through a range throwing the end exhausts into and out of action.

3. In a steam engine, the combination of a cylinder ported to receive and exhaust steam from its end and to exhaust steam at a point remote from the end, both exhausts being to the same passage; a piston in the cylinder controlling the exhaust to the passage; and a valve controlling the admission and exhaust from the end of the cylinder and varying the point of cut-off of the steam as its travel is varied and automatically effecting an end exhaust at late cut-ofi' and closing the same at early cut-ofi', and means actuating the valve and varying its travel through a range throwing the end exhaust into and out of action.

In testimony whereof, I afiix my signature.

ROBERT C. STEVENS.

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