US45322A - Improvement in variable tube-gear - Google Patents

Description

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UNITED STATES PATENT OFFICE.

GEORGE DODDS AND ELIHU DODDS, OF ALLEGHENY, PENNSYLVANIA.

IMPROVEMENT IN VARIABLE TUBE-GEAR..

.To all whom t may concern,.-

Be known that we, GEORGE DoDDs and ELIHU DODDs, of the city of Allegheny, in the I county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Variable Out-Offs for Steam-Engines; i and we do hereby declare the following to be a full, clear, and exact description thereof, reference being had to the accompanying drawings, forming part of this specification, in which- I Figure l is a vertical section through the cut-off apparatus and steam-chest. Fig. 2 is a top view of the cams and cam-yoke of the cut-off apparatus, being a horizontal section through x x, Fig. l. Fig. 3 is a perspective representation of the upper or cnt-oft' cams. Fig. 4 is a perspective representation of the spiral cylinder by which the variation of the cut ott' cams is effected. Fig. 5 is a vertical section through the hollow crown-wheel shaft and spiral cylinder at right angles to the section in Fig. 1.

In the several figures like letters of reference denote similar' parts.

Our invention consists in the use and adaptation of certain mechanical contrivances for 1 the purpose of operating the independent cutoft' valve in steam-engines in such a manner that the point of the stroke of the piston at which the steam is cut off shall be variable throughout the length of the stroke, and so that the point of cutoff shall change with the increased or diminished force of steam, exactly in proportion to the rapidity of stroke of the engine, thus forming a variable cut-off, which may also be rendered adjustable.

To enable others skilled in the art to construct a-nd use our invention, we will proceed to describe the construction and operation of our cut-off apparatus.

In Fig. l, a is the cylinder of the steamengine, and b the piston. c is the steam-chest. d is the working slide-valve, above which is ,f placed the cutoff valve c, which is also a slidevalve, and which, being placed over the port through which the live steam enters the steaml chest, controls the admission ot'steam to either l end of the cylinder. The cutoff valve e is connected by the rod j' with the cam-yoke g g', which has two working-points, each terminating in a friction-roller, t', to reduce the fric i tion of the working-faces of the cams h Ic. The upper or variable cam, It, is the cut-ott' cam, operating to close the cut ofic valve e and shut the steam from the steamchest of the cylinder. The lower cam, k, operates to open the cutoff valve e and admit the steam at the commencement of each stroke ot' the piston, and, as the steam is admitted always at the same points, the cam k is keyed fast to the shaft which operates the governor, and is not adjustable or capable of variation in the relative time of its operation, while the upper or cut-oft' cam, h, is susceptible of variation in its position on the governor-shaft relatively to the lower or opening cam, so as to cnt oft' the steam at any point in the stroke of the pistonrod to within a short distance of the commencement or end of the stroke.

In Fig. l, l is the governor shaft, which is inserted in the vertical hollow shaft m, with which it is connected by a pin, n, which passes through a slot on each side of the hollow shaft m, so that the governor-shaft l will revolve with the hollow shaft m, and at the same time will fall or rise just as the revolutions of the governor o are more or less rapid. The hollow shaft m is connected with the engine by crown-wheels p p', or in some other convenient or usual way, so that the increased or diminished speed of the engine is communicated to the governor.

A short hollow cylinder, q, (through which .1 the hollow shaft m passes,) is attached to the governor-shaft l by the pin n, so that the short cylinder q revolves with the shat't m and governor-shaft l, while it also rises and falls with the governor-shaft. This short cylinder q has two spiral teeth, r i", projecting from the face of the cylinder, the pitch of which is such that each of the teeth passes nearly halfround the cylinder in its whole length, as seen in Fig. 4.

These spiral teeth r r fit in corresponding grooves s in the central circular hole in the upper or cut-oft' cam, h, through which the spiral cylinder q is inserted.

The cnt-off cam It, the shape of which is shown in Fig. 3, is so situa-ted on the shaft m. as that its acting faces are in the same horizontal plane as the friction wheel t at the end of the working-point g of the cam-yoke The cam his not fastened to the spiral cylinder q, nor to the shaft fm, but is supported by means of annular attachment t, which rests on a collar, u, on the hollow shaft m, as seen in Figs. l and 5. The cam h has no vertical motion on the shaft m or cylinder q, but it is caused to revolve with the governor-shaft l and short cylinder q by means of the spira-l teeth 1' i" iitting in the grooves s. It has also another motion on its axis independent ofthe continuous rotary motion, which will be hereinafter explained.

The lower cam, lr, which opens the cut-off valve e and admits steam, has its operative faces in a lower plane than those of the cutoit' cam h, as seen in Fig. 1 and the operative point g of the cam-yoke is in the.same plane as the cam k. The cam k is keyed to the hollow shaft m so as to revolve with it, and has a recess around the shaft m to allow room for the vertical play of the spiral cylinder q of the cut-oft' cam h.

The operation of our cut off apparatus is as follows: When there is full head of steam on and the engine is working too fast, the gov- Ornor revolves very rapidly, which causes'the governor-shaft l to descend in the hollow shaft m, and at the same time depresses the spiral cylinder q, which is fastened to the lower end of the governor-rod l, as shown in Fig. 5, and lefore described. The depression of the spiral cylinder q causes the cam 4l1J to turn on its axis on the cylinder q more or less, as the cylinder is more or less depressed, owing to the spiral teeth r r on the cylinder q working in the grooves s in the cam h, for, as the spiral cylinder has a vertical motion with the governorshaft l, and as the cylinder q, the governorshaft l, and the hollow shaft m are fastened together by the pin n, and as the lower cam, k, is keyed to the hollow shaft m, those parts c lnnot have any relative motion around their cammen axes, although they all revolve together. Now, as the vertical motion of the short cylinder q inside ofthe cut-off cam h cames that cam to move on its axis relatively to the short cylinder q, it will also alter the relative position of the upper and lower cams h and 7c and of their operative faces. The increase of speed of the governor-shaft l, and the consequent depression of the short cylinder y, will bring the operative faces h of the cut-oft' cam nearer to the operative faces k of the lower cam, as shown in Fig. 2. This position ofthe parts of the apparatus is shown in Figs. 1 and 2, where the camface k of the lower cam has opened the cut-off valve e. As the cam is revolving in the direction of the arrow in Fig. 2, it will be seen that the camface h of the cut-off cam is very close to the operative point t' of the cam-yoke, by which the cut-off valve e will be closed. If, however, the speed of the engine should diminish, the governor-rod l would rise and raise with it the spiral cylinder q, which would cause the cut oft' cam h to change its relative position to the` lower cam, k, and assume the position shown by dotted lines in Fig. 2, the effectof which would be that the cut-off valve would not be closed until nearer the end of the stroke.

rlhus the relative position of the' operative faces ofthe cams h and k regulates the length of time which elapses betweenthe admission of the steam and its being cut off, and, as this relative position is altered by the rise and fall of the goveri'ior-shaft, the cut-ott' valve will promptly respond in the action to that of the governor.

Having thus described our improved cutoff apparatus, what we. claim as our invention, and desire to secure by Letters Patent, is-

The combination and arrangement of the opening-cam k and cut-oft' cam h, camyoke g g', and the spiral cylinder q, as a cut-off apparatus constructed substantially as described, with the governor andZcut-off valve of a steamengine, for the purpose of so regulating the closing of the cut-oft' valve as that the point of cut-off shall change with the increased or diminished force of steam in proportion to the rapidity ot' stroke of the engine, thus forming a variable cut-ofi'.

In testimony whereof, the said GEORGE and ELIHU DoDDs have hereunto set their hands in presence of us.

GEO. DODDS.

ELIHU DODDS.

Witnesses:

A. S. NrcHoLsoN, J. M. NEAL.

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