US852757A - Valve-gear. - Google Patents

Description

PATBNTED MAY 7, 1907.

A. D. AUSTIN.

VALVE GEAR.

APPLICATION FILED MAR. 2s, 1906.

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No. 852.757.- PATENTE) MAY?, 1907.

A. n. AUSTIN.

VALVE GEAR.

APPLICATION FILED MAR. 2s, 190e.

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ALBERT l). AUSTIN, OF STTLWELL, KANSAS.

VALVE-GEAR.

i No. 852,757.

Specification of Letters Patent.

Patented May 7', 1907.

Application iilecl March Z3, 1906. Serial No. 307,702.

To @Z whom, it may concern:

Be it known that l, ALBERT D. AUSTIN, a citizen of the United States, residing at Stilwell, in the county of Johnson and State of Kansas, have invented a new and useful Valve-Gear, of which the following is a specification.

This invention relates to valve gear for steam engines, and has for one of its objects to provide a valve gear in which the return movement of the valve to cut off position is accomplished by mechanism independent of the eccentric or other device employed to mani ulate the valve.

A urther object of the invention is to provide a valve gear for imparting true motion to the valve, so that the different events, t'. e., admission, cut off, release, and conpression, will occur at equal periods of the piston travel during both strokes of the piston.

A still further object of the invention is to provide a valve mechanism in which the point of cut off is adjustable from one-quarter to seven-eighths, more or less, of the piston stroke, without affecting the time of release and compression or cushioning.

A still further object of the invention is to provide a valve gear which, when adjusted for a quick cut off, will travel nearly the full stroke during the opening movement, in order to secure a practically full open port, and the admission of steam to the cylinder without wire drawing.

A still further object of the invention is to provide a valve operating device, in the form of an eccentric or its equivalent, which will have approximately double the throw of the valve travel, thus securing rapid movement and large port openings, while the return or cut off movement of the valve is independent of the eccentric.

With these and other objects in view, as will more fully hereinafter appear, the invention consists in certain novel features of construction and arrangement of parts, hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the form, proportions, size and minor details of the structure may be made without departing from the spirit or sacrificing any ofthe advantages of the invention.

Figure 1 is an elevation, showing the cylinder and the steam chest in section, of a valve gear constructed in accordance with the invention', the crank being shown on dead center, and the piston at the end of its out stroke. Fig. 2 is a similar view showing the steam pressure cut off after the piston has made a quarter stroke. Fig. 3 is a view similar to Fig. 1 with the parts adjusted to cut off at about three-fourths stroke, the valve and' piston being in the same position as illustrated in Fig. 1. Fig. 4 is a view similar to Fig. 3, sho wing the steam cut ofl at the completion of three-fourths' of the in stroke of the piston.

Similar numerals of reference are ernployed to indicate corresponding parts throughout the several figures of the drawings.

The cylinder A contains a piston B that is connected by a rod C to a cross head D. From the cross head extends a connecting rod E to a crank pin F, the latter being carried by the crank or crank wheel of the main shaft G. Above the cylinder is a steam chest H containing a D-slide valve I, controlling the flow of steam through cylinder ports J and K, and an exhaust port L.

On the shaft G of the engine is secured an eccentric 10, surrounded by a strap 11 that is connected by a rod 12 to a rocker arm 13, said rocker arm being secured to a suitable shaft 14 that is mounted in bearings in the frame of the engine, the arrangement of the frame and the length of the shaft being determined by the character of the engine with which the valve gear is employed.

The inner end of the shaft 14 carries a crank arm 15, that is provided with an elongated slot 16, extending radially from about the center of the shaft to a point adjacent to the outer end of the crank arm. Extending through the slot 16 is a pin or block 17 that is connected to the bifurcated outer end of a rod 18, the inner end of which is connected to the valve stern. This mechanism opens the valve, and the closing movement thereof is accomplished for the most part by downward movement of the block or pin 17 in the slot 16, the walls of the slot serving at this time as a cam which acts'to eliect movement of the pin or block in such direction as to close the valve and cut olf the flow of steam to the cylinder.

The movement imparted to the crank arm 15 is the same at all times, and the distance to which the valve is opened depends on the distance between the center of the shaft 14 IOO IIO

and the axis of the pin 17. This distance, however, varies but little, and the valve will open quickly and will give afull port opening, no matter what the point of subsequent cut ofiimay be, so that the steam under full boiler pressure may enter the cylinder at once.

Pivoted on a pin 2O carried by the frame of the engine, is a bell crank lever 21,v the approximately horizontal arm of which is connected by a link or links 22 to the pin 17, and the approximately verticalA arm of the bell crank lever'is connected to a pair of parallel links 23 which pass on opposite sides of the vertical arm of a bell crank lever 24 that is pivoted on a pin 25 carried by the engine frame. The ends of the link members 23 are connected by al link 26 to a cut off adjusting lever 27 that is pivoted on a pin 28, and is movable over a locking quadrant 29, the adjusting lever being provided with a locking latch 30 which serves to engage the quadrant and hold the lever in any position to which it may be adjusted.

The bell crank lever 24 is arranged at a point above the cross head D, and its approximately horizontal arm is connected to the cross head by av link 32. The approximately vertical arm of the bell crank lever is provided with an arcuate slot 34 that receives a slidable pin or block 35 carried by the links 23. The curvature of the slot is such that the lever 27 may be adjusted from one end of the locking quadrant to the other, moving the pin 35 from one extreme position to the other without effecting any movement of the valve when the crank pin is on dead center, or is slightly beyond either dead center, so that the adjustment may be readily accomplished.

When the lever is in the position shown in.

Figs. 1 and 2, the adjustment is such that the valve will cut off at one-fourth the stroke of the piston.

With the parts in the position shown in Fig. 1, and the crank pin traveling in the direction indicated by the arrow, the first effect of the movement would be to draw the valve to open position, admitting steam to the outer end of the cylinder. To accomplish this the eccentric acts through the rod 12 and rocker arm 13 to rock the shaft 14 and crank arm 15 l then moves approximately to the dotted line position x ofFig. 1,'and in so doing opens the valve, the opening in this valve being a trifle less than full port opening. As the cross head D moves out, this movement is transmitted through the link 32 to the bell crank lever 24, and as the pin or block 35 is at this time at its highest point in the slot 34, a rapid movement will be transmitted through the links 23 tothe bell crank lever 21, and the horizontal arm of said bell crank lever will force the link 22 down quickly, and this will carry down the pin or block 17 in the slot 16, the walls of the latter then acting as a cam in order to effect movement of the connecting rod 18 in the direction indicated by the arrow in Fig. 2, and the valve will be closed and steam cut off by the time the piston has reached quarter stroke. From` this point on, as the center of the cross head gradually.

approaches the vertical plane of the pin 38 which connects the link 32 to bell crank lever 24, there will be a slight further downward movement of the pin or block 17, and the valve I will continue to move a very short distance toward the left. After the link 32 has been moved beyond the vertical plane, the movement transmitted from the cross head tends to throw the curved arm of bell crank lever 34 to the right, and this movement, transmitted throughv the link 23 and bell crank lever 21, tends to elevate the link 22 and block 17, and at this time the eccentric has passed beyond the center, and the crank arm 15 moved rapidly to the left in order to close the port leading from the crank shaft end of the cylinder, thus cutting off the escape of steam and leaving sufiicient steam at the crank shaft end for cushioning purposes'. At the completion of the stroke, the crank arm 15 is inclined to the left to exactly the same extent as it was formerly inclined `to the right, and the movement will take place at the same speed, but in reverse order, in order to cut off the flow of steam at a quarter stroke of the piston as the latter moves away from the crank shaft.

With the parts adjusted to the position shown in Fig. 3, the cut off will occur at about three-quarter stroke of the piston. It will be noted that in this case the in or block 35 is near the lower end of the s ot 34, and the movement transmitted to the link 23, bell crank 21, and link 22 to the pin or block 17, will be much slower than before, and will not be to the same extent, so that the piston must travel a much greater distance before the flow of steam is cut off. In fact, the cutl ofi1 in this case is not accomplished wholly from the cross head, but the movement lags until the eccentric, drawing the crank arm 15 to the left, effectsclosing of the valve and the cut off of the steam, and

shortly thereafter cuts 0H the release in order to leave a quantity of steam in the cylinder for cushioning urposes. In this case the shutting off of the. release occurs at precisely the same point as where the parts are adjusted in the manner shown in Figs. l and 2, there being no change in release and compression, and if it is desired to effect adjust ment of this portion of the mechanism, recourse may be had. to the usual reversing lever and link connections commonly employed, especially those used in locomotive valve gear.

The lever 27 may be adjusted to any angular position between the two extreme po sitions shown in Figs. 1 and 2, and the point IOO ISO

this Without in any manner a eating the point of release or the Compression. The

mechanism further is so arranged as to permit precisely the same out off, release and.

compression periods at both the in and out strokes of the piston, an operation which is seldom, if ever, accomplished by valve gears now in use.

I Claim 1 l. In valve gear, a valve, a roeker arm, a shaft having stationary bearings carrying said rocker arm, means for rocking the shaft and arm, a bleek mounted on and movable radially of the arm approximately from the axis of the shaft to the outer end of said arm, means for connecting the block to the valve, and means operated by the Gross head of the engine for moving said block.

2. In valve gear, a slide valve, a rocker arm, means for moving the same, a bloek mounted on and movable radially of the rocker arm, means operated from the eross head for actuating said block, and adjustable means for Controlling the extent of movement of the block, and means for Connecting the bloek to the valve.

3. In valve gear, a valve, a rocker arm, means for moving the same, a block mounted on and movable radially of the arm, means for connecting the block to the valve, means operated from the Cross head for moving said blook radially of the arm, and means for adjusting the extent of movement of the block.

4. In valve gear, a valve, a slotted rocker arm, means for moving the same, a block mounted in the slot and movable radially of the arm, means for connecting the block to the valve, a system of links and levers oonneoting the cross head of the engine to the block, and means for controlling the range of movement of said block.

5. In a valve gear, a valve, a slotted rocker arm, a bloek mounted therein and movable radially of the arm, means for operating said arm, means for connecting the block to the valve, a bell crank lever having a slotted arm, a block or pin movable in said slotted arm, means for connecting the bell Crank lever to the cross head, a link Carrying the bloek or pin, means for connecting said link to the block of the rocker arm, a eut-off adjusting lever connected to the link, and means for looking said lever in adjusted position.

In testimony that I claim the Jforegoing as my own, I have hereto aiiixed my signature in the presenee'oi1 tWo Witnesses:

ALBERT D. AUSTIN.

Witnesses:

W. B. WHITAKER, JOHN SUMMIT.

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