US757411A - Valve-gear. - Google Patents

Description

PAT-ENTED APR. 12, 1904.

No. 757,411. I

s. A; REEVE.

VALVE GEAR.

APPLICATION FILED MAR. 21, 1901.

4 SHfiETS-BHEET 1.

N0 MODEL.

|NVENTEHRI WITNEESESZ No. 757,411. PATENTED APR. 12, 1904.

s. A. REEVE.

VALVE GEAR. APPLICATION FILED IAB. 21, 1901.

N0 MODEL. 4 SHEETS-SHEET 2.

17 INVENITEIRH a; w WITNES E5:

wza fw w No.757,4111 j PATENTED APR. 12, 1904.

s. A. 'REEVB.

VALVE GEAR. APPLICATION FILED MAR. 21, 1901.

L E f N0 MODEL. 4 SHBBTB-SHBET 3.

N0. 757,411, PATENTED APR. 12, 1904.

s. A. REEVE. VALVE GEAR.

APPLICATION FILED MAR. 21, 1901. N0 MODEL.

4 SHEETS-SHEET 4.

IV K27 27 $23 UNITED STATES Patented April 12, 1904.

PATENT OFFICE.

SIDNEY A. REEVE, OF WORCESTER, MASSACHUSETTS, ASSIGNOR TO CHARLES F. BROWN, TRUSTEE, OF READING, MASSACHUSETTS VALVE-GEAR.

SPECIFICATION forming part of Letters Patent No. 757,411, dated April 12, 1904.

Application filed March 21, 1901. Serial No. 52.147. (N model.)

To all whom it may concern:

Be it known that I, SIDNEY A. REEvE, of Worcester, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Valve-Gears, of which the following Isa specification.

This invention relates to valve-gears for -motors of the steam-engine type; and its objects are to attain greater simplicity of mechanism in multiple-valve systems and governor-controlled systems and an improved control over steam distribution to two or more cylinders.

Of the accompanying drawings, Figure 1 represents a side elevation of a reversing steam-engine constructed in accordance with my invention. Fig. 2 represents a view showing a shaft-governor applied to one eccentric of the engine. Figs. 3, 4, and represent diagrammatic views illustrating the derivation of the eccentric motion. Figs. 6, 7 and 7 represent, respectively, a plan, a section, and a modification of a non-reversing engine embodying my invention. Fig. 8 represents a side elevation, and Fig. 9 a transverse section of a modification of the reversing-engine shown in Fig. 1. Fig. represents a side elevation of a modified valve-gear, illustrating a method of governor-control for both forward and backward running.

The same reference characters indicate the same parts in all of the figures.

My invention is primarily intended to afford a method of control for the valves of a two-cylinder engine whose pistons are arranged to reach their dead-points at diiferent instants.

Referring at first to Fig. 1, 1 and 2 designate two cylinders, permissiblythe high and low pressure cylinders of acompound engine, having the usual pistons and rods and the cross-heads 3 4-, connected by pitmen or connecting-rods 5 6 with the pin 7 of a single crank 8 on a crank-shaft 9. In this figure the axes of the cylinders coincide with the dead-center lines of the crank for the respective cylinders; but such coincidence is not essential. The cylinders may be parallel and drive a single crank, as shown in Figs. 8 to i 10, or they may be mounted parallel in the travel of the shaft between the two deadpoints is preferably not great. Although two cylinders only are shown in Fig. 1, these two cylinders may be considered to be the two extreme cylinders of a series, the intermediate members of which lie between the two cylinders 1 2, all of the pistons having different dead-points. The following discussion, therefore, though confined to the case of two cylinders, applies with equal force to a greater number than two.

1O 11 represent the two valves controlling the steam admission and exhaust to and from the cylinders 1 2, and 12 13 represent the two valve-spindles. Ordinarily an engine with two cylinders, if non-reversing,'w'ould be equipped with two eccentrics and two eccentric-rods for operating the respective valves, and if provided with a'reversing link-motion would have four eccentrics, four eccentricrods, and two links, besides the corresponding reversing-levers and other attachments. In reversing-engines with their cylinders disposed angularly, as shown in Fig. 1, the above.

equipment can be reduced by two eccentrics. Iproposeto do away with practically onehalf of this valve-operating equipment, thereby effecting a saving in cost and weight, de

creasing running friction, repairs, &c., and also attaining considerable advantages in steam distribution and control, as hereinafter described.

The manner of deriving my novel valvemotion will be understood from Figs. 3, 4, and

5, inwhich the new positions of the eccentrics ters of the forward and backward eccentrics for a Stephenson reversing link-motion for this valve may be assumed to be at the points 15 and 15, the eccentric radii 9 15 and 9 15 making approximately equal angles with the center line 14 14. Now let the crank be revolved backward to the dead-point 7 Fig. 4, corresponding to cylinder 2, and the same center line 14 1 1 be assumed for a valve-motion for operating valve 11. The eccentric centers 16 16 for a reversing link-motion for operating this valve will then be in the former positions of 15 15 and the latter will have moved backwardly through an angle equal to the movement of the crank. The dotted lines 15 15 and 16 16 represent the paths along which the virtual-eccentric centers for the two links would pass when the links were thrown from full forward gear to full backward gear, the virtual eccentric for any link and pair of eccentrics operating it being the imaginary single eccentric, which would give the valve the motion which it actually receives when partly under the control of each of its two eccentrics. If now the engines were to be equipped with a third Stephenson link with eccentrics centered at 17 17 on radii bisecting the angles between the radii for the forward and back eccentrics of the other two links, as shown in Fig. '5, the virtual eccentric for this third link would have a path represented by the dotted line 17 17 as the third link was thrown from full forward gear to full backward gear. Let the line 17 17 be extended and it will give the intersections 18 19 18 19. If nowthe third link be made of extra length, so that its block may be moved beyond the position corresponding to 17 into the position corresponding to 18 for the virtual eccentric, a pin in said block will obviously receive a motion timed the same as a pin under full control of eccentric 15, though itstravel will be greater than the travel of the latter pin, as indicated by the greater distance of the point 18 from shaft 9 than the point 15. Similarly, a pin located at a point in the third link corresponding to point 19 on the virtual eccentric would receive a motion timed the same as a pin under full control of the eccentric 16, but its travel would be less than the travel of the latter pin. In backward gear the block of this third link when placed in position corresponding to the point 18 would receive a motion timedexactly with that of a block under full control of eccentric 15, but having less travel, and when placed in position corresponding to point 19 it would be timed with a block operated by eccentric 16, but would have a greater travel. Therefore, the question of travel being ignored, a block operated by a third. link at the point 18 for full forward motion and at the point 18 for full backward motion would properly operate the valve of cylinder 1, and similarly another block at the point in the third link corresponding to point 19 for forward and 19 for backward gear would properly operate the valve 11 of cylinder 2. As the distance between the paired intersections 18 19, &c., remains substantially the same for all intermediate positions of eccentric centers 16, &c., on the virtual eccentric paths between full forward gear and full backward gear, the two pins in the third link may be placed in blocks, which simultaneously change their position in the link when the reversing-lever is operated, or they may both be placed in one and the same block.

In Fig. 1, 20 represents the third link alluded to in the above discussion. 17 17 represent the eccentrics for operating said link. 21 22 are the eccentric-rods connecting the eccentric-straps with the link, and 23 21 are two pins connecting the valve-rods 12 13 with a single block 25, mounted to slide in the link 20: 26 represents the reversing-lever. The efi'ects of the unequal travel of the valves may, by a choice of laps and other dimensions such as is within the ordinary skill of those practiced in the art, be counteracted sufficiently to give in practice a steam distribution for both ends of the two cylinders, which is fully as satisfactory as that attained with standard link-motions.

By applying to the forward eccentric 17 a centrifugal shaft-governor 260, Fig. 2, which will move the eccentric center inward along the virtual-eccentric line 17 17 Fig. 5, as the speed of the engine increases beyond a certain point a useful governing eifect may be attained, which is particularly adapted to compound or other multiexpansion engines, for in the operation of the governor the cut-off of the valve 10 0f the high-pressure cylinder will be varied to a greater extent than that of the lowpressure valve 11. and there is thus effected a mean result between the plan of governing both high and low pressure cylinders equally, which affords good speed regulation under variable load, but usually at the expense of good efficiency, and the plan of governing the high-pressure cylinder alone, which, although giving good efficiency, usually results in excessive fluctuations of speed.

Figs. 8 and 9 represent a parallel arrangement of cylinders 1 2 with pistons operating upon a single crank in a manner very similar to that shown in Fig.1 the valves are somewhat widely separated in a transverse direction, being located in valvechests 27 28 on opposite sides of the engine. A novel valve-operating mechanism for this and similar arrangements of valves is then provided. 20 is a link operated by eccentrics 17 17, as before, and having a block 29, which may be considered the equivalent of the upper half of the block in Fig. 1. This block 29 is located upon the end of a short shaft 30, mounted to oscillate in a bearing at the upper end of a vertical rocker-arm 31 on a rockshaft 32. The rock-shaft is mounted in fixed bearings 33 33 on the frame and carries at its opposite end a vertical rocker-arm 34, having In this, however, 1

with the block 29, and its timing and travel are therefore the same as that of the block.

The pin might be placed at any other point rigid with the rock-shaft 32 if it were desired.

to give it the same timing as the block 29, but a different travel. On the opposite end of the short shaft from the block 29 is fixed a short arm or crank 35, which carries the pin 24, to which tl'1e'low-pressure-valve spindle 13 is attached, this pin being placed opposite that point in the arc of the link whose timing and travel it is desired to impart to the lowpressure valve. Any otherpoint in the arc of the link or in that are produced, even though outside of the actual length of the link, may in like manner be duplicated by a pin rigid with the shaft 30.

In applying my invention to a non-reversing engine, such as that illustrated in Figs. 6 and 7, wherein are. shown two cylinders 1 2 in the plane of the crank-shaft operating upon two differently-timed crank-pins 36 37 I provide a link or floating-lever 38,,which is the equivalent of the upper half of the reversinglink 20 in the preceding figures, and locate the pins 23 24 for operating thetwo valve-spindles 12 13 in fixed positions upon the link. An eccentric 17, equivalent to the forward eccentric in the preceding explanation, operates through a connecting-rod 39 on a pin 40,10- cated between the pins 23 24. may be a fixed one, or, as indicated in the drawings, it may be controlled by a shaft-governor 260, in which case the same advantages in the control of a compound engine will be attained as explained in connection with the reversingengine employing the shaft-governor on its forward eccentric. If the eccentric be a fixed one, as mentioned above, the control of the position of the block or blocks in the link may be by hand or by a centrifugal speed-governor of any suitable design. To operate the lower end of the link 38, I provide a fixed eccentric 41, acting through a connecting-rod 42 on a pin 43 on said link. This eccentric is the equivalent of a mid-gear eccentric namely, one located about midway between the forward and back eccentrics of the reversing-engine, or, referring to Fig. 5, its center would be at the point 44 midway of the path 17 17 of the virtual eccentric. Such point 44 in the single-crank engine shown in Fig. 1 would be on a line through the crankshaft and crank-pin when the crank occupied a position midway between its dead-center positions for the two cylinders. In the two- This eccentric sition, and its variation affords the designer an additional factor with which to regulate steam distribution. to a great nicety.

Fig. 7 represents the motion for the lower end of the link 38 as taken from one of the cross-heads of the engine by elongating the link and connecting it through a rod 45 with a lever 46, oscillated on a fixed fulcrum from the said cross-head.

Fig. 10 illustrates a construction affording governor control for one or more valves ofa reversing engineat all times during both forward and backward motion of the engine;

47 is anAllen link, having a sliding block 48, which may operate one valve or may operate more than one valve by some such mechanism as illustrated in Fig. 9. 17 is an eccentric connected by rod 21 to the upper end of the link and controlled by a shaft-governor, and

41 is an eccentric having its center at the point 44, Fig. 5, and connected by rod 42 to a point 49 at about the middle of the link. In all positions of the block 48 above the point 49 the engine will run in a forward direction with governor. control of its cut-01f, and in all positions of the block below point 49 the engine will run backward with governor control of its cut-off in the same manner as though the link were connected at its lower end with a governor-controlled backward eccentric. In this form of my invention the Gooch or Stephenson link-motions or others might be substituted for the Allen link shown, and likewise in Figs. 1, 8, and 9 other forms of linkmotion might be substituted for the Stephenson link shown. reserve the right to use equivalents in place of the devices shown.

It is evident in all the forms of my invention that the link receives a combined rocking and translating movement.

1. In a reciprocating steam-engine, a plurality of cylinders having non-synchronous pistons and non-synchronous valves, a single link connected to produce the complete steamdistributive cycles of movements of said valves, and means connected with said link for giving it a combined rocking and translating movement.

2. In a reciprocating steam-engine, a plurality of cylinders having non-synchronous pistons'and non-synchronous valves, a link connected to operate said valves, means. including an eccentric and a device having a fixed motion for imparting a combined rocking and translating movement tosaid link,

In other particulars also I IIO and means for automatically governing said nected with the link for giving it a combined rocking and translating movement, and means for shifting the position of theblock on the link.

4. In a reciprocating steam-engine, a plurality of valves, a link operating said valves unequally and non-synchronously, an eccentric connected to one portion of said link, and a device having a mid-gear motion, connected to the mid-gear portion of said link.

5. In a reciprocating steam-engine, a link forming part of areversible-link mechanism, a part having a mid-gear motion connected substantially at the middle of said link, an eccentric connectedwith one end of said link, and a governor controlling said eccentric.

6. In a link-motion, a link, a guiding memnature in presence of two witnesses.

SIDNEY A. REEVE.

Witnesses:

CHARLES F. ALDRICH, JOHN W. SHEEHAN.

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