US635092A - Slide-valve. - Google Patents

Description

8 L l D E VA LV E (Application filed Dec. 2, 1898.)

2 Sheets-Sheet I.

(No Modal.)

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Patented Oct. l7; I899. C. C. EGBERT.

8 L l D E VA LV E (Application filed Dec. 2, 1898.)

2 Sheets$heet 2.

(No Model.)

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CHARLES C. EGBERT, OF DUNKIRK, NEW YORK.

8 LI DE-VALVE.

SPECIFICATION forming part of Letters Patent N 0. 635,092, dated October 17', 1899. Application filed December 2, 1898. Serial No. 698,040. (No model.)

To all whom it may concern:

Be it known that I, CHARLES C. EGBERT, a citizen of the United States, residing at Dun kirk, in the county of Chautauqua and State of New York, have invented a certain new and useful Improvement in Slide-Valves, of which the following is a specification.

My invention relates to various new and useful improvements'in slide-valves adapted when operated by a suitable valve mechanism to admit and release in proper rotation a fluid under pressure to and from the ends of a cylinder or cylinders of a motor, compressor, or pump, whereby the latter will perform its work in the desired manner.

My improved slide-valve is especially adapted for use in connection with steam-engines and will be so described in the following description, it being of course obvious that the valve may be suitably changed or modified, according to the use to which it will be applied.

The object of myinvention is to provide a slide-valve that bears upon its seat with apressure which may be made as light as desired and which remains practically constant throughout the travel of the valve. In effecting this object in the manner to be explained I obtain a slide-valve which will be perfectly and accurately balanced.

Prior to my invention slidevalves have been made wherein the balancing thereof has been attempted by excluding the steam-pres sure from a portion of their backs, so that they will bear upon the Valve-seats with a less pressure than if entirely covered by steam. It is evident that the pressure with which these so-called balancedslide-valves bear upon their seats varies in proportion to the steam-pressures in the steam-chest and in the ports and to the area of the portions of the valve face exposed tosuch pressures. In consequence it follows from these conditions that the pressure necessary to maintain one of these valves on its seat while the force tending to lift it is at its maximum will be excess ive when the said lifting force is at its minimum value.

In carrying out my invention and in addition to excluding the steam-pressure in the steam-chest from a portion of the back of the valve I provide a separate area on the back of the valve which is proportional to the area of those portions of the valve-face exposed to steam-pressure and which by means of a suitable passage or passages in the valve is put into communication with the steam which presses on such exposed portions of the valveface.

In carrying my invention further into efiect I so proportion the length of the valve-seat relative to that of the valve that the sum of the areas of those port-ions of the valve-face exposed to steampressure remains practically constant throughout the travel of the valve. In this way I am enabled to introduce onto the back of the valve a varying pressure which is proportional and synchronous with the varying pressure on the face of the valve.

In order that my invention may be better understood, I have illustrated in the accompanying drawings the improvements applied to a slide-valve of a well-known type.

In the drawings, Figure 1 is a plan of a slide-valve at present in use, known as the American balanced valve, illustrating my present improvements applied thereto; Fig. 2, a cross-section on the line X X of Fig. 1, illustrating the balance plate, valve, and valve-seat, and showing the valve in its middle position; Fig. 3, a section similar to Fig. 2, on a similar scale, illustrating the valve advanced on its seat; Fig. 4:, a sectional view similar to Fig. 2, illustrating a slightly-different arrangement with the valve in its middle position; Fig. 5, a section corresponding to Fig. 4: with the valve advanced on its seat; Fig. 6, a plan, on an enlarged scale, of one of the packing-rings, showing a convenient arran gement of steam-tight joint therefor; Fig. 7, an elevation of the same, and Fig. 8, a cross section on the line Y Y of Fig. 7.

In all of the above views corresponding parts are represented by the same letters of reference.

While I have illustrated my invention as being employed in connection with a valve of a special type, it will be, of course, obvious that the improvements may be used with many other varieties of valves wherein the balancing thereof is necessary or desirable.

The valve will work in any position 5 but tight joint with the ring II.

in the drawings and in the explanation that follows the valve-seat is assumed to be in a horizontal plane.

A represents the exhaustport, and the steam-ports, of an engine.

0 is the valve, with a passage-way D' connecting the ends of its face. Uponthe back of thevalve C the plate E is suitably secured. This plate is provided with a shoulder S, making a steam-tight joint with a ring G, and also with ashoulder T, making a steam- The rings G and H bear against the balanceplate I maintained within the valve-chest in any suitable manner, parallel, or nearly so, to the valveseat W. The areas on the back of the valve which are used to balance it may be subdivided in any other way than by the employment of packing-rings Gand H, as described. These packing-rings are made of any desired material and in any convenient manner, and in Figs. 6, 7, and 8 I illustrate a construc tion of steam-tight joint for the ring H which may be employed, if desired, but to which I do not wish to be limited. As shown, the ring H is beveled on its outside circumference and split, in order that it may expand or contract and thereby adjust itself against the shoulder T and the plate F. The shoulder T is beveled on its inside circumference to accommodate the ring I I, whereby the pressure in the space inclosed by the ring tends to expand it and maintain it always in tight engagement with the plate F. In order to prevent leakage through the split 9 in the ring, a rectangular plate f may be employed, fitting tightly against the shoulder T, ring II, and plate F. This rectangular plate is secured in any suitable Way to one end of the ring G, the other end of said ring being allowed to slide freely with respect to said angular plate, whereby the latter does not interfere with the expansion and con- B and B traction of the ring, while at the same time it maintains the desired steam-tight character of the joint.

K is a passage connecting the passage-way D with the space inolosed by the ring H. Preferably the passage K is fitted with a bushing M to prevent the leakage of steam into the space inolosed by the ring H by way of the joint N, formed between the valve 0 and plate E. Passages P P connect the exhaust-cavity V in the valve-seat with the space inolosed by the ring G outside of the ring H. These passages P are formed in bosses p, where they pass through the passage-way D. The passages P conduct to the exhaust-cavity any steam which may leak past the rings G and 1-1.

In the proportions of the device illustrated in the drawings the plate E is substantially circular, as shown, while the valve 0 is essentially rectangular. Those portions of the valve outside of the plate E are therefore pressed downward by the steam-pressure in way D is in communication.

the valve-chest, and this pressure is counteracted to the desired extent by the upward pressure of the steam in the steam-chest on the under side of those portions of the plate E which overlap the valve. These areas are so proportioned as to maintain the valve upon its seat with the desired pressure, which, with my present improvements, maybe made relatively slight at all times, since the varying pressures to which the valve is subjected and which tend to elevate it from the seat are counteracted and counterbalanced by correspondingly-varying pressures in opposition thereto, as will be explained.

In explaining the operation of the device the valve shown in Figs. 4 and 5 will be first considered. With this valve the valve-seat is so proportioned in relation to the length of the valve that at the instant steam is admitted to one of the ports by one end of the valve the other end of the valve begins to overlap the end of the seat. Thus when the end aof the valve is at the edge e of the port 13 the other end b'of the valve is at the end 01 of the valve-seat. It therefore follows from these proportions that the area of the portion of the'valve overasteam-port plus the area of the portion of the valve overlapping the valve-seat is proportional to the area of one steam-port. D urin g that part of the valvetravel that the valve overlaps the valve-seat the steam in the steam-port on the steam end of the cylinder is necessarily at steam-chest pressure; but after cut-off, when the steampressure in that port commences to diminish on account of the expansion of the steam in the cylinder, the valve ceases to overlap the valve-seat. The passage-way D is so arranged that it remains in communicationwith one steam-port until the steam exhausts from that port, when it comes into communication with the other port. This is clearly shown in Fig. 4, wherein the passage-way D is just out off from the port B, and any further movement of the valve 0 will allow exhaust from the port B and will place the passage-way'D in communication with the port B.

It is evident that if the valve-seat be proportioned as in Figs. 4 and 5 the variable force tending to lift the valve from its seat is proportional to the area of one port plus the area of the passage-wayD and to the steampressure in the port with which the passage- In other words, the pressure tending to elevate the valve from its seat in Fig. 5 is that due to the steampressure on the valve-face over the port B and to the overlapping portion of the valve-face beyond the edge d of the seat. As the valve is moved to further uncover the port 13 its area subjected to the steam-pressure in the port will be diminished; but the area of the portion overlapping the valve-seat will be correspondingly increased, so that the changing surfaces which are thus subjected to the but since the passage-way D is in communifull steam-pressure will be of constant area. During cutoff the only portion of the valveface subjected to pressure which tends to elevate the valve will be that covering the port at the steam end of the cylinder, and during this period of the operation the passageway D will be in communication with that port. Owing to the expansion of the steam in the steam end after cut-oil", the force tending to elevate the valve will be grad u ally diminished;

cation with this grad uallydiminishing steampressure, the counterbalancing force on the valve will be correspondingly and proportion ately decreased, as will be explained.

Since the space over the valve which is encom passed by the ring II is in communication with the passages K and D, it follows that the steam-pressure within the said space will be equal to the steam-pressure in the port with which the passage-way D is in communication. If now the said area of the space encompassed by the ring H is proportional to the area of one steam-port plus the area of one end of the passage-way D, then a downward force will be exerted on the back of the valve which is proportional to and synchronous with the upward force exerted on the valve by steam-pressure on the valve-face. In other words, since the pressure during the operation of the valve, other than during the cut-off period, which tends to elevate the valve is that due to the full steam-pressure acting on an area equal to the area of one port plus the area of the passage-way D, and since the space on the back of the valve inclosed by the ring H is proportional to that area and is in communication with the full steam-pressure, the forces tending to elevate the valve from its seat and toward its seat will be counterbalanced. During the cut-off period the force which tends to elevate the valve from its seat will be that due to the steam-pressure on the valve-face covering the steamport, which pressure will gradually drop during the expansion. Since, however, the passage-ways D and K communicate with the port the steam-pressure in the space inclosed by the ring II will be correspondingly and proportionately diminished. In this way it will therefore be seen that I have obtained a valve wherein a perfect balance is at all times secured, whether the pressure which tends to elevate the valve is constant or varying.

Referring now to the valve shown particularly in Figs. 2 and 3, it will be observed that the length of the seat is so proportioned in relation to the length of the valve that the passage-way D will fulfil the functions of an auxiliary port,as is the casein the well-known Allen valve that is to say, at the instant that the end a of the valve passes the edge e of the steam-port B the edge e of the passage-way D passes the end. at of the valve-seat. Steam therefore enters the port B directly and also indirectly through the passage-way D,as illustrated by the arrows in Fig. 3. In a like man be compensated for in proportioning the area excluded from the steam-pressure by the ring G. In other respects, however, the upward force due to the steam-pressure in the steamport and in the passage-way D will be compensated for in the same manner as I have already explained in connection with Figs. 4

and 5name1y, by making the area of the space inclosed by the ring H proportional to the area of one port plus the area of one end of the passage-way D, whereby the steampressure, whether constantor varying, which tends to elevate the valve will within said space exert a counteracting effect, tending to keep the valve upon its seat.

The advantages arising from the employment of my improvements are manifest. Steam-pressure may be excluded from a larger portion of the back of the valve than has been heretofore possible, resulting in a perfect cou nterbalance,in easier working of the valve, in less wear on the valve, the valve-seat, and the mechanism operating the valve, and, if the engine be of the reversible type, enabling it to be handled more easily.

Having now described my invention, what Iclaim as new, and desire to secure by Letters Patent, is as follows:

'1. The combination with avalve-seat, of a slide-valve cooperating therewith and having pressure excluded from a portion of its back,

an inclosed area on the back of said valve,

and a passage-way conducting pressure to the space over said area,substantially as set forth.

2. The combination with a valve-seat, of a Valve cooperating therewith having pressure excluded from a portion of its back, an inclosed area on the back of said valve, and a passage-way connecting the space over said inclosed area with the ports in the valve-seat, substantially as set forth.

3. The combination with a valve-seat, of a valve cooperating therewith having the pressure excluded from a portion of its back, an inclosed area on the back of said valve, and a passage-way connecting the space over said inclosed area with the ports in the valve-seat and with thespace beyond the valve-seat, substantially as set fort I 4. The combination with a valve-seat having steamports therein, of a valve cooperatin g with said valve-seat and having the pres sure excluded from a portion of its back, an inclosed area on the back of said valve, and a passage-way connecting the space above said area with those portions of the valve-face Working over said ports, whereby the pressure within the ports will correspond to the pressure within the inclosed area, substantially as set forth.

5. The combination with a slide-valve having the pressure excluded from a portion of its back, an inclosed area on the back of said valve, and a passage-Way connecting the ends of the valve-face with the space over said area, of a valve-seat with which said valve cooperates, said valve-seat being so proportioned that at the instant pressure is admitted to a port by one end of the valve, the other end of the valve begins to overlap the valveseat, substantially as set forth.

6. The combination with the valve-seat of a cut-off engine, of a valve cooperating therewith and having pressure excluded from a porvalve-seat, whereby when the admission-port is cut off to allow for expansion the passage will conduct the decreasing pressure to the inclosed space, substantially as set forth.

7. An improved slide-valve, having a ring on its back and a passage-Way connecting the valve-face with the space inclosed within said ring, and a balance-plate With which said ring cooperates, substantially as set forth.

8. An improved slide-valve, having an ex This specification signed and witnessed this 28th day of November, 1898.

CHARLES C. EGBERT.

lVitnesses:

S. B. DURAND, W. H. TEW.

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