US66204A - bartlett - Google Patents

Description

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Letters Patent No. 66,204, elated July 2, 1867,

`IlliIPROVEMEN'I" IN VALVE-GEAR FOR STEAM ENGINES'.

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To ALL wHoM rr MA-Y CONCERN:

Be it known that I, LOUIS D. BR'rLETT, ofr Fitchburg, in the county of Worcester, and State of Massachusetts, have invented certain improvements in operating the Valves of Steam Engines as Cut-Oife, of which thefollowing is a full, clear, and exact description, reference being had to the accompanying drawings, making part of -this specification, which- Figure 1 represents the valve-stem of a steam engine, together with my improved arrangement of levers and cams for operating'the same.

Figures 2, 3, and 4, details to be referred-to.

Figures 5 and 6 represent a modication of Amy invention. Y

My invention relates Ito that class of variable cut-oils for steam engines, in which the levers which lift the stems of the valves are carried in or out by the action of the governor, so that they will .be llifted more or less by thefrevolution of, cams so as to-cut olf the steam at the required point.

In engines constructed in accordance with 'the Letters Patent o f the United States granted to Charles H. Brown and Charles Burleigh, on the 15th day of January,.A.` D. 15856', it becomes necessary to revolve the cam-shaft vat a less speed than the main shaft, in'order to permit the steam to follow the piston the whole length of the stroke, should the work on the engine require it. ,This diminution of speed renders it necessary to constructs the valve-gear" with great' nicety, any inaccuracy in'its 'construct-ion or deviation in the angular -velocity of the cam-shaft being much more perceptible in its effect upon the working of the engine than would be the case it the speed ot' the camshaft were the same las that of the main shaft,-thc inuence on the valves being greater in Aproportion as `the angular velocity of the cam-shaft is less than that of the main shaft. A further objection is that when the sliding leveris carried in so that thesteam will be cutoil` near the commencement of the stroke, the cam strikes suddenly against the lever,causing noise and wear upon the parts, which in engines of large dimensions is aserious diculty. I

My invention has for its object to overcome these objections, and enable me to revolve the cam-shaft at the same speed as the main shaft, thus rendering errors in construction less apparent, and consists in lmaking the cams in a circular form, set eccentrically upon their ,shaft to operate levers, the upper 4corners of which act upon the sliding levers which lift the valves; and my invention also consists in the employment, in combination with the circular' cams, of supplementary cams or toes which serve vto bring the upper corners of lthe eccentric levers in contact with the sliding levers, without noise, thus reducing the wear and rendering my invention peculiarly applicable to engines of large size.

I To enable others skilled in the art to understand and use my invention, I will proceed to describe the manner in which I have carried it out.

In the said drawings, A is thestem 'of one-of the inlet .valves of a steam engine, which is operated by the sliding lever B, pivoted to the arm C, which is keyed to a horizontal shaft. Another arm on this shaft is connected with the governor (byv means of` a rod, as seen .in red in 1, the motion of the governor-being thus transmitted through the arm C `to the sliding lever B. I) is a lever, one end of which is connected with the arm C, by means of a pin working in a slot, a'. Within the opposite end of the lever D works a. circular cam, E, set eccentrically upon the camshaft F, which is connected by suitable gearing with the main shaft of the enginc, so that both shafts l,will runat the same speed, andl thus as the cam E is revolved, a horizontal as well as a vertical motion willbc given' to the lever D, the upper corner 7 ofwhich bears against the shoulder b of the sliding lever B, so as to raise the stemV A of the valve and admit ste-am toi the' cylinder as required. In proportion, however, as `the balls of the governor diverge, the lever 'B is carried farther inward in thedirection of the red arrow, iig. 1, causing the shoulder 6 of the lever B to lie more or less over the upper corner 7 of the lever D, and thus, as the cam revolves, the valve will bekept open for a longer or shorter space of time, according to the position of the governor-halls, while, when thc governorballs arent their highest point, the shoulder will be carried in to such an extent that the corner 7 of the lever D will not raise the lever B `as the cam. isv revolved, and consequently thc inlet valve will remain closed. The steam is thu's cutci sooner or later in proportion as the balls of the governor 'are more or less distended. The'` exhaust valves arel operated by levers'and cams similarly tothe steam valves', except that `they are not connected with the g0vernor, and are consequently allowed to open and close without variation. v

I will now proceed to describe the device which I employ for the purpose of bringing the upper cornerT of the lever D into contact with the sliding lever B Without noise or shock, thus reducing the wear upon the parts. G,' iig. 4, lis. a supplementary cam or toe which is attached to the cam E, and bears -upon the straight portionlvc', (igf 2,) ofthe lever D, and this cam G serves to commence the lifting of the parts which raise the valve, without noise or shock, while it also snpportsthe lever D, (as it slides horizontally,) at such a height that its upper corner 7 will `not fall below the under surface of the sliding lever B during the time occupied by a half revolution of the cam-shaft F when the valve is closed. By this arrangement the corner 7 is prevented from striking against thenleve'r B, and all noise and shock are consequently avoided, thus reducing the vWear upon the parts and rendering my invention particularly applicable to engines of large dimensions. Where the speed of the engine is high, or where the weight and strain on the valves are great,.supplementary cams or toes, as above described, are essential; but in smaller engines, or where a low speed is required, the supplementary cams or toes may be dispensed with, eccentric cams only being employed to operate the levers D, as seen in figs. 5 and 6.

The above-described method of operating the valves of steam engines enables meto revolve the camshaft at the same velocity as the main shaft, and thus reduce anyinfluence on the valves occasioned by inaccuracy in' the construction of the valve-gear, or deviation in theiangular velocity of the cam-shaft, a'desideratum heretofore unattained in that yclass of cut-offs Whichallovv the steam to follow the piston throughout the whole or any part of its stroke.

. O'Zaz'm. What I claim as my invention, and desire to secure by Letters Patent, is-

Operating the valve of a steam engine by means of the lever D, actuatedby the eccentric cam E, in connbination with the lever B, substantially as'described. I i l I also claim, in combination with the above, the supplementary cam or toe Gr, operating substantially as described for ythe purpose set forth.

LOUISD. BARTLETT.

Witnesses:

JAMEs M. WooDBUnr, Mosns FAInBANKs.

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