US578213A - cochrane - Google Patents

Description

(No Model.) 2 Sheets-Sheet 1 J. GOGHRANE 85 W. CAMERON. VALVE GEAR.

No. 578,213. Patented Mar. 2, 1897.

(No Model.) 2 Sheets-Sheet 2.

J. GOGHRANE & W. CAMERON.

, VALVE GEAR.

Pate nted Mar; 2, 1897.

co v PHOTO-L nda. WASNXNGTON, nv c.

UNITED STATES PATENT QEEICE.

J OHN COOHRANE, OF BARRHEAD, SCOTLAND, AND VVILLIAIWI CAMERON, OF MARYPORT, ENGLAND.

VALVE-GEAR.-

' SPECIFICATION forming part of Letters Patent No. 578,213, dated March 2, 1897.

Application filed May 4, 1896. Serial No. 590,128. (No model.) Patented in England November 24,1894, No. 22,800.

To all whom it may concern.-

Be it known that we, JOHN OOOHRANE, of Barrhead, in the county of Renfrew, Scotland, and VVILLIAM CAMERON, of Maryport, in the county of Cumberland, England, subjects of the Queen of Great Britain and Ireland, have invented a certain new and useful Improvement in Valve-Gear, (for which we have obtained a patent in England, No. 22,800, dated November 24, 1894,) of which the following is a specification.

This invention relates to the release mechanism of that type of gear in which the steam I and exhaust valvesof engines are operated from one eccentric without the intervention of a wrist-plate, the object being to secure an automatic and variable release and closure of the steam-valves varying from zero to threefourths of the engine-stroke.

The improvements essentially consist of horizontal oscillating levers and bell-cranks under the control of a regulating device, and coupling-rods, detents, and levers.

Under this invention means are employed whereby the detent edges, which hear at certain periods on projections securely fixed to the steam-valve spindles, are caused to describe variable closed curves, the variability of the said curves in relation to the edges of the before-mentioned projections depending upon the action of the governor. In order to obtain this, levers, which are rigidly attached to the detents, are connected by suitable rods to bell-crank levers hung on a horizontal oscillating lever. This horizontal lever may be oscillated by an eccentric suitably set in relation to the main eccentric. This is preferably done from a suitable point located in the eccentric or in the rodthat is, in the rod of the eccentric used for operating the steam and exhaust valves. The levers hung on the oscillating lever besides being connected to the detents are also coupled to the governor-balls in a suitable manner. The detents are hung on levers that are hung on the valve-spindle brackets.

We get all the advantages of a wrist-plate by driving the steam-valves by means of a link from pins located in the exhaust-Valve levers. The links couple the exhaust-valve levers to the levers on which the detents are hung. These detents engage with and are released from projections securely fixed t0 the steam-valve spindles at certain periods. By correctly locating the position of these pins the detents engage quietly with their projections, and their edges describe closed curves similar to those obtained by the use of a wrist-plate. The detents are rigidly attached to their levers, which are connected co to the bell-cranks hung on the horizontal oscillating lever in precisely the same manner as above described.

The detents may be mechanically engaged with and released from their projections, and consequently the engines to which these improvements are applied can be run at a much greater number of revolutions per minute than would be possibleif the detents were not positively engaged and released. Owing to this and to the certainty of the action, the engines are especially adapted for electriclight installations and for driving electrictransmission plants.

In cases where the detents are not directly coupled to the governor-controlled bell-crank levers that are hung on the horizontal oscillating levers they are operated by trip-levers which are not rigidly attached to the detents, said levers being preferably mounted on the same pin on which the detents are hung, but they may be hung on pins located on any suitable part of the levers which carry the detents. The trip-levers are coupled to the bell-cranks in exactly the same manner as in the before-mentioned combinations, but owing to the trip-levers not being rigidly attached to their detents the curves described by the detent edges are notclosed. The governor in this instance merely determines the 0 amount which the detents engage with their projections and the point at which they are released. The detents fall into gear with their projections by gravitation or by the action of a spring. In this case the extent of 5 automatic release can be extended beyond three-fourths of the pistons stroke, but the speed at which the engine can be run must be less than when fitted with the positivelycontrolled detent. Onrelease of detents from their projections the valves in all cases are closed by springs or atmospheric pressure by means of a vacuum dash-pot and are cushioned in the usual manner. As the valves are operated by one eccentric and the range of automatic expansion is from zero to threefourths of the pistons stroke, the release of the detents may take place either during the opening or closing periods of the steam-valves travel. This is obtained by giving the detents two movements, one directly from the eccentric which opens and closes the stean1- valves. The other, hereinafter called the secondary movement, at right angles to the first, determines the engagement and release of the detents wit-h their projections. This movement is given to the detents by the bell-cranks and horizontal oscillating lever, which may receive its movements from any suitable moving part of the engine. In order that the detents may be released automatically at any point of the pistons stroke, according to the load on the engine, the bellcranks are placed under the control of a governor. The governor thus controls the amount of overlap with which the detents engage with their projections, and therefore determines the point of release. As the secondary movement given to the detents by the oscillating lever is a constant, the resultant movement of the detent edge is a close curve. The variability of the release-point depends upon the amount of overlap the detents have at the instant of engagement for any given point of release, that is, the path described by the detent edge leaves the projection earlier the less the amount of overlap; and in order to enable others skilled in the art to which our invent-ion relates to understand how the same may be carried into practice we have hereunto appended explanatory drawings, in which the same reference-letters are used to indicate corresponding parts in all the figures where shown.

Figure 1 is an elevation of a positively-controlled gear in which the detents and levers are rigidly connected together. Fig. 2 is a detached view, to an enlarged scale, of the bell-cranks and connection to governor shown in Fig. 1. Figs. 3 and 4 are detached views showing the detents and levers not rigidly connected together. Fig. 5 is a view analogous to Fig. 1, showing a slight modification. Figs. (3 and 7 are detached views showing the release mechanism of Fig. 5 to an enlarged scale.

Referring to the drawings, in the arrangement shown in Fig. 1 a a are the detents with the rigidly-connected levers b b and are hung to the levers c c, the levers b I) being coupled to the bell-cranks e e by rods (1 d. The bell-cranks e e are hung on the horizontal oscillating lever f, which wit-h its bell-cranks e e is placed equidistant from each of the detent-levers b b and is driven from the eccentrio-rod by means of a bell-crank o. This arrangement is a convenient one when the cy1- inders are arranged tandem.

I11 Figs. 3 and 4: are shown the arrangement preferred of detent and lever when they are not rigidly connected together. They are hung on the pin which is secured to the lever c. The detent a is formed with a finger 7c, armed with a steel face. A similar finger Z is also formed on the lever 19, so that the movement of the bell-cranks is communicated to the detent a through the lever b by the steel faces on these. The movement so communicated is such that it will only release the detent a from its projection 01 and determine the extent of their engagement. It will be obvious that the detent a and lever b may be hung on different pins secured in the lever c, the finger being so formed as to give the same movement to the detent as when hung on the same pin. The projection d is secured to the valvespindle m.

In the arrangement shown in Fig. 5 the levers c c, on which the detents a a with their rigidly-attached levers b b are hung, are driven by means of links from the exhaustvalve levers n it. By correctly locating the centers of the steam and exhaust valves and the points on the exhaust-valve lever from which the levers c c are driven the detents Ct a are brought quietly into contact with their projections 61 C1 The levers b l) are coupled to the bell-cranks e a by rods cl d. The bell-cranks e e are hung on the horizontal oscillating lever f, which is oscillated by the rod 9 from the eccentric-rod h. The bellcranks are connected to the governor G by the rod 2'. The right-hand detent a is engaged with its projection (1 the right-hand steam-valve being opened the amount of lead. The left-hand steam-valve is closed, the lefthand detent a being clear of its projection (1 Figs. 6 and 7 show the release mechanism on a larger scale.

It is to be understood that the release-gear shown by Figs. 3 and 4c may be applied to any of the combinations in place of the rigidlya-ttached detent and lever. It Will also be apparent that the governor may be replaced by a hand-wheel and suitable mechanism by which the release may be controlled by hand instead of automatically.

We claim as our invention 1. In release-gear, the combination of a lever n secured to the exhaust-Valve spindle, a lever a freely hung on the steam-valve bracket, and a coupling-link connecting the said levers, with a lever I) hung on the lever c, and provided with a detent a, and a projection secured to the steam-valve spindle.

2. In release-gear, the combination of levers I) provided with detents a, with a horizontal oscillating lever, two bell-crank levers hung thereon, and connections between the said levers b and the said bell-cranks and between the bell-cranks and the governor, substantially as and for the purposes set forth.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

JOHN COCHRANE. IVM. CAMERON. IVitnesses:

WILLIAM CRAIG, WILLIAM BUCHANAN.

IIO

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