US247659A - Cut-off-valve gear - Google Patents

Description

G. L. KITSON.

, GUT-OFF VALVE GEAR.

No. 247,659. Patented Sept. 2'7, 1881.

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lUNITED STATES PATENT Char-ICE..

GEORGE L. KITsoN, oE PHILADELPHIA, PENNSYLVANIA.

CUT-oFF-VALVE GEAR..

SPECIFICATION forming part of Letters Patent No. 247,659, dated September 27, 1881.

' Application filed February 9, 1881. (Model.)

To all whom t may concern Be it known that I, GEORGE L. KITSON, a citizen ot' the United States, residing in Philadelphia, Pennsylvania, have invented an Improvelnentin Cut-Off-Valve Gear, ot' which the following is a specitication.

My invention relates to an improvement in that class of cutoff-valve gear in which the slide-valve is combined with cut-oftl plates arranged on the back ot the vulve, the movement of these plates being due to friction, and being governed by an adjustable stop or stops.

' The objects ot' my invention are to simplify the construction ot' the cut-off mechanism, to prevent any nndueincreasein the speed ofthe engine owing to derangement of the governor or its connections, and to prevent too rapid a decrease in the area ot' the steam-passages due to the movement of the cut-oli' plate. These objects I attain in the manner hereinafter set forth, reference being had to the accompanyingdrawings, in whichf Figure l is a skeleton perspective view of part ofthe cylinder and valve-chest of a steamengineprovided with an automaticcut-oft-valve constructed according to myinvention; Figs. 2 to S, diagrams illustrating the operation of the valve, and Fig. 9 a transverse section of the valve through one of the steam-ports.

A represents part of the cylinder, and B part of the valve-chest, of an ordinaryr steamengine, D being the piston, D the piston-rod, and E the eccentric-rod, which is connected to a gridiron-valve, F, having steam-ports ab and an exhaust-port, c, working in conjunction with the steam-ports a' b' and exhaust-port c of the cylinder, as usual.

On the back ot' the valve F is a plate, G, forming thecut-oit' valve, said plate being held firmly against the back ot' the valve F by the pressure of steam, and being dependent for its movement upon this frictional contact with said valve F. A stem, d, projects from the plate Gr through a stuffing-box in the valvechest, and this stem is provided with a yoke,

c, which embraces aWedge-shaped block, f,

carried by a vertical sleeve, g, under control of a suitable governor driven by the engine. rBhe block j' thus acts as a stop to limit the eX- tent of movement of the cut-oft plate G, the movement being contracted as the block is raised, and an increased movement being perniitted as the block is depressed, and the narrow portion of the wedge is brought into the path of the yoke. This variation in the movement of the plate Gr is caused to regulate the cutting oft' of steam to the cylinder of the engine, as will be understood on reference to the diagrams, Figs. 2 to 8. l

Figs. 2, 3, and 4 are diagrams representing 6o the operation of the valve when the narrowest portion of the wedge-block is in line with the stem of the plate G, the Wedge occupying this position when the engine has the heaviest load. In this case the wedge exerts practically no 6.5 control over the movement ot' the plate G, the latter moving with the valveF throughout the entire throw of the latter, so that there is no restriction of the entrance of steam into the cylinder from the beginning almost to the end 7o of the stroke. This will he understood on reference to the diagrams, Fig. 2 showing the parts at the commencement ofthe stroke, with Asteam just entering the cylinder through the `ports a a', Fig. 3 showing the piston at mid- 75 stroke and the ports a a' wide open', and Fig. 4 showing the piston at the end ot' the stroke, with the ports a a closed and the opposite ports b b' about to open.

In Figs. 5,6, 7, and 8 I have shown the ac- 8o tion of the valves when the work ot' the engine is light and the wedge-block f is lifted so that the portion of greatest width is in line with the stem of the plate G, the movement ofthe latter being in this case very much restricted and the steam being cut oft shortly after the commencement of the stroke ot' the piston.

Fig. 5 represents the position of the parts at the commencement of the stroke, the valve F moving in the direction of the arrow. By the 9o time thepistonhas moved to theposition shown in Fig. o' the plate G has closed the steamports a a', and these ports remain closed until the end of the stroke,the steam being worked expansively. On the reversal of the direction of movement ot' the valve F after the piston has reached mid-stroke, Fig. 7, the plate G moves slightly with the said valve, so as to prevent the uncovering ot' the port a. ot' the valve before the latter has passed the port a ico of the cylinder. (See Fig. 8.) On the return stroke of the piston the plate Gr acts, in conjunction with the steam-ports b b', in the same manner. rIhe action ot' the exhaust-ports c c will be understood from the diagrams without explanation.

It will be seen that the less the movement of the plate G the sooner will the steam be out oft' from the cylinder, and that an increase in the extent of movement of the plate len gthens the time during which steam is admitted, so that the power of the engine is directly proportioned to the work to be done, the variation in the euttingoi' point being automatically effected through the medium of the governor and wed gabloelr. Where automatic variation is not required, however, the wedge-block may be adjusted by hand, and in some cases the said Wedge-block may be arranged inside the steam-chest and adapted to act directly upon lugs or projections on the back ot' the plate G, a vertical stem from the block passing through the top of the steam-chest, and being attached to the governor-slide or other adjustingdevice. In some cases,also, screw-stems may be passed through the cover-plate of the valve-chest, on opposite sides of a lug on theplate G, the points ot' these screws inside the chest being tapered and adapted to come into contact with said lng, so that by adjusting the screws the movement of the' plate G may be governed as desired.

It will be observed on reference to Fig. 9 that the ports ot' the valve F have their ends dared outward at the top, the object of this arrangement being to increase the area of the outer face of the port, so as to preventtoo sudden a decrease in the area ot' the steam-inlet, as said outer face of the port is covered by the plate G.

The wedgeblock f has at the top and adjacent to its narrowestl'ia'rt an expanded portion, m, the object of which is to prevent any sudden increase in the speed of the engine in the event ot' the breaking of the governor-belt or other derangement of the governor which would permit the wedge-block to fall to its fullest extent, for when such an accident occurs the expanded portion m of the block is brought into the path of the stem of the plate G, the movement of the latter is restricted, and the supply of steam to the engine is almost entirely out oft'.

When it is desired to balance the pressure on the plate G, and thereby reduce the power required to move the same, the rod E ot' the valve F may have an arm provided with jaws for clamping the stem d ot' the plate G, and cansingfriction enough to move the plate, the jaws slipping on the stem when the movement of the plate or stem l is obstructed.

I am aware that it has been heretofore proposed to use in connection with the slide-valve of a steam-engine a pair of frictional cutoff' plates located on the back of the valve, these plates beingindependentofeach other, andeach plate being adapted to actin conjunction with one of the steam-ports of the valve, the movement of the plates in one direction being gov erned by an adjustable block, and in the other direction by contact of the ends of the plates with the ends of the steamchest casing. Such an arrangement, besides lacking the convenience and simplicity of the single plate which I employ, is also objectionable, because it 4nccessitates the use ot' plates ot' such a size that the area of t'rictional contact between said plates and the valve is unduly increased and the movement ot' the valve impeded.

I therefore claim as my invention- 1. The combination of the cylinder of the engine and its ports, the valve F, the single cut-oli' plate G,andan adjustablestop or stops therefor, the movement of the plate G being due to friction, and said plate occupying a substantially central position on the back of the valve F, wherebythe opposite ends of the plate are caused to govern the opposite steam-ports ot' the valve as the latter is reciprocated, all substantially as set forth.

2. The combination ot' the frictional cut-oli' plate G, the governor, and the wedgeblockf, having an expanded portion,m,adjacent to the narrow portion ot' the wedge, as set forth.

3. The combination ot' the cylinder and its ports, the cut-offplate G, and the valve F, having steam-ports flared outward at the outer face, as set forth.

In testimony whereof I have signed my name to this specification in the prcsenceot' two subscribing witnesses.

GEORGE L. KITSON.

Witnesses:

J AMES F. ToBlN, HARRY SMITH.

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