US795165A - Slide-valve mechanism. - Google Patents

Description

No. 795,165. PATBNTED JULY 1a, 1905. L. M. PEM-1T.

SLIDE VALVE MBGHANISM.

ArPLIoATIoN PILBD ma. 4, 1904.

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No. r/95,155. PATENTLD JULY 1a, 1905. L. M. PBTTIT.

SLIDE VALVE MBGHANISM.

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No. 795,165. v PATENTED JULY 18, 1905.

L. M. PETTIT. v

SLIDE VALVE. MEGHANISM.

APPLICATION FILED MAB. 4, 1904. l

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UNITED STATES Patented July 18, 1905.

PATENT OEETCE.

SLIDE-VALVE IVIECHANISIVI.

SPECIFICATION forming part of Letters Patent No. 795,165, dated July 18, 1905,

Application filed March 4, 1904. Serial No. 196,616.

T0 all whom, it may concern:

Be it known that I. LAFAYETTE M. PETTIT, a citizen of the United States of America, residing at Oripplecreek, in the county of Teller and State of Colorado, have invented certain new and useful Improvements in Slide- Valve Mechanism; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters of reference marked thereon, which form a part of this specification.

My invention relates to improvements in slide valve mechanism for steam engines, myv object being to provide a construction of this class in which the clearance or the space between the piston and the valve when the piston is at its limit of movement in either vdirection shall be reduced to a minimum.

This is an important feature in slide-valve mechanism, since the less the volume of steam required to fill the clearance-space the quicker will the steam-pressure in this space act upon the piston of the cylinder with the full boiler-pressure. Instead of having long passages extending from the extremities of the cylinder to the steam-chest I provide vertical 'passages or ports leading from the extremities of the cylinder to the steam-chest, and instead of having the cylinder reinforced to form a fiat seat where the slide-valve is located the surface of the valve is formed arc-shaped to conform to the curve of the cylinder, whereby the ports leading from the cylinder to the steam-chest are only of a depth equal -to the thickness of the wall of the cylinder. In this way it is understood that the length of the ports is much less than where the top of the cylinder is reinforced to form a iiat base or platform for the slidevalve. j

Another feature of my improvement is that my improved valve is perfectly balanced.

Having briefly outlined my improved construction, as well as some of the functions it is intended to perform, I will proceed to describe the same in detail, reference being the' valve in a different position.

made to the accompanying drawings, in which is illustrated an embodiment thereof. v

In the drawings, Figure 1 is a vertical longitudinal section taken through my improved slide-valve mechanism and extending into the cylinder. Fig. 2 is a similar view showing Fig. 3 is a cross-section taken through the steam-chest at one end and cutting the cylinder. Fig. 4 is a horizontal' section of the same. Fig. 5 is a perspective. View of the valve, shown in detail. Fig. 6 is a top view of the steam-chest with the top plate removed. Fig. 7 is a section taken through the packing-groove of one of the slide-valve heads. Fig. Sis a detail perspective view of the packing construction.

The same reference characters indicate the same parts in all the views.

Let A designate the steam-chest, whose side walls A extend upwardly from the cylinder, the steam-chest being closed by a top plate A2. The bottom of the steam-chest is curved to conform to the curve of the cylinder, and the wall of the latter is provided with a vertical port A3, located at each end thereof. The slide-valve B is composed of two heads B', connected by a bar B2. The live-steam space is between the heads of this valve, while the steam-chest is provided with an exhaust-port A4, located at each end thereof. The heads of the valve are curved to conform to the curve of the cylinder except at their outer extremities beyond the ports A, where the bottom of the steam-chest is composed of narrow ledges A5, these ledges being of suiiicient length to form a support for the heads of the valve during the longitudinal movement of the latter. At each end of each head of the valve the latter is provided with lugs B3, which project inwardly. The function of these lugs is to balance the valve while it is passing the steam-ports. lf it were not for these lugs or projections, the upward pressure of the steam, whether live or exhaust, on the valve-head while crossing the steam-port would throw the valve out of balance, and thus cause increased resistance to its movement in the steam-chest. The lugs or projections B3, however, project into the steam-chest while the valves are crossing the ports, and the downward pressure of the live steam on these lugs or projections neutralizes the effect of the upward steam-pressure on the valve-heads while crossing the ports. The area of the parts B3 is so regulated as to produce this result. It will therefore be understood that the parts B3 may be made of any suitable size in order to perform the required function. The bottom of the steam-chest is cut away between the seats B4, as shown at B, so that as soon as a valve-head has passed beyond the steam-port into the steam-chest or the space containing the live steam the parts B3, connected with the valve-head, will project over the reduced part B5 of the bottom of the valve-chest `and allow the live steam to pass below the said projections, thus neutralizing the eHect of these projections after they have performed their function. Each valve-head is grooved to receive packing rings or plates B, which interlock and overlap each other in such a manner as to make perfectly steamtight joints. The heads B of the val-ve are of rectangular shape except their bottoms or lower extremities, which are arc-shaped to conform to the curve of the top of the cylinder or bottom of the steam-chest upon which the valve slides. As shown in the drawings, one head of the steam-chest is provided with separated lugs B8, having inwardly-turned outer extremities B. The eccentric-rod C is provided with a T-shaped head C', adapted to enter or pass between the lugs B8 from-v above, after which the eccentric-rod and the valve are connected in operative relation. The rod may of course be detached from the valve-head by simply lifting it out of place in a manner that will be readily understood.

In the drawings the cylinder is designated D, the cylinder-heads D', and the piston of the cylinder D2.

From the foregoing description it is believed that the use and operation of my improved slide-valve will be readily understood. In Fig. l of the drawings the slide-valve is shown moved toward the right far enough to uncover the ports' E and E. In this case the port E is a live-steam port, through which the live steam passes from the steam-chest A between the valves to the right-hand end ofthe cylinder D and to engagement with the piston D2, while the port E becomes an exhaust-port, since the steam at the left of the cylinder is passing out of the latter through the port F into one end of the steam-chest at the left of the slide-valve head and out of a port A4. In the construction shown in Fig. 2 the port E is closed against the live steam, while the port E is still partly open to the exhaust, and

the piston under this arrangement must complete its stroke toward the left by expansion. In this case the steam in the cylinder at the right of the piston will act on the righthand valve-head B with a tendency to force the latter upwardly; but the downward pressure of the live steam in the steam-chest on the parts B3 of this valve-head neutralizes the upward pressure of the steam in the cylinder, whereby a perfect balance of the valve is maintained, while as soon as the right-hand piston Bl is moved sufliciently toward the left (still referring to Fig. 2) to open the port or passage E wide the parts or projections B3 of the said valve-head will overlap the reduced portion B5 of the bottom of the steam-chest, and thus allow the steam to pass beneath the said projections, rendering them neutral or functionless under the conditions named.

The lower packing-plate part B10 on each side of each valve-head is supported upon a pin B12, made fast in the head. This plate is allowed to move outwardly freely on the pin, whose only function is to hold the lower extremity of the plate Hush with the corresponding extremity of the valve-head.

Having thus described my invention, what I claim isM The combination of a steam-chest whose bottom is curved to conform to the curve of the wall of the cylinder, vertical ports connecting the opposite extremities of the cylinder with the opposite extremities of the steamchest, and a slide-valve located in the steamchest and composed of two separated heads, aV

suitable rigid connection between these heads, andinwardly-projecting parts connected with the heads, the bottom of the steam-chest being provided with seats for these projections while the valve-heads are passing the ports moving inwardly, the bottom of the valvechest being cut away, to allow the steam to pass underneath the said projections as soon as the heads have opened the steam-ports wide at their inward travel.

In testimon y whereof I aflix my signature in presence of two witnesses.

LAFAYETTE M. PETTIT.

Witnesses:

OSCAR L. FAIRLEY, CHAs. D. RAUBER.

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