US133741A - Improvement in steam-engines - Google Patents

Description

a. H. BABGOCK. Steam-Engines.

Patented Dec. 10,1872.

AM PHOIO-LITIIOGFAPH/C [OJ/J. (OSBORNE S PROCESS.)

UNITED STATES PATENT 1 OFFICE.

GEORGE H. BABOOOK, 'oE FLAINFIELD,'NEW JERSEY.

lMPROVEM ENT IN STEAM-ENGINES.

Specification forming part of Letters PatentNo. 133,7 1 1, dated December 10, 1872.

To all whom it may concern:

Be it known that I, GEORGE H. BABCOGK,

' of Plainfield, Union county, New Jersey, have invented a certain Improvement in Valve-Motions for Steam-Engines, of which the following is a specification:

I will describe the invention as applied to a small upright stationary-engine regulated byan ordinary centrifugal governor.

One of the advantages, which will be appreciated by engineers as due to this invention, is the equalization of the action on the up-anddown strokes that isto say, it compensates for the changing angle of the connecting-rod in different portions of the stroke. The point of the cut-' off is thesame in the up-stroke as in the down-stroke under all conditions; and so of the point of exhausting, compression, &c. Only one eccentric is employed. The accompanying drawingforms a par'tof this specification. Figure 1 is amend elevation, and Fig. 2 is a side elevation. Fig. 3 is a diagram,showing the motion'of one of the parts on a large scale. v

Similar letters of reference indicate like parts in both the figures.

A is the fixed frame, and A the fixed vertical guides cast therein, which perform the ordinary function of guiding the cross-head. B is the cylinder, and O abelt, which communicates motion to the governor F through beveled gearing, as will be understood. D is the main shaft, receiving the action of the engine through a crank and connecting-rod; which,

. as also other parts of the engine not represented, it will be understood may be of the ordinary or any suitable construction. A single eccentric, d, operates'a stout encompassing part formed in two pieces and bolted together, which I will term an eccentric strap. The lower part I will mark M and the upper part M ,referring to the whole, when necessary, by the single letter M. The lower part M has a groove, which, as the eccentric (1 re volves, is traversed up and down in a constantly-changing inclination on a block, N, which is free to swivel a little on a pin, n, fixed firmly in the framing. The arrangement causes the upper arm M to describe a path somewhat analogous to an ellipse, with its transverse axis horizontal, but with the lower side of the ellipse flattened. The upper end of the arm M carries a block, m provided with adjustable gibs and adjusting nuts and screws. This-block, with its gibs, takes hold slightly but firmly of a slightly-curved piece marked E, which is smoothly finished, and allows the block m to traverse smoothly from its one extremity to the other. As the shaft D revolves the center of the block W describes a path in space which is indicated on'a large scale' in the diagram, Fig. 3. This path is invariable under any given adjustment of the pin n. Its effect, however, on the valve, both with regard to the amount of throw and the time in which the valve arrives at any given point, is greatly modified according as the piece E is inclined more or less. The valve may be an ordinary slidevalve. G is the valvestem, connected 'adjustably to the yoke G,

to which the adjustable curved piece E is pivoted, so that it rises and s'iDkS therewith as the valve is worked. Some portion of the benefit of my invention may be realized by fixing the piece E in an invariable position on the yoke G, or directly upon thevalve-stem, and holding the valve-stem by some suitable guide against any lateral motion, allowing the motion of the block m to be communicated invariably to the valve-stem G. I have, however, added provision for conveniently adjusting the point of cut-off, and for effecting thiswith great perfection by means of agovernor. The piece E is pivoted upon ayoke, G, so that it can be easily turned into various degrees of obliquity. The piece E has an arm, E, extending upward at right angles therefrom. On the center of motion of the piece E E on the pivot e, which connects the piece E E with the yoke G, is carried a lever, H, which turns on a'fixed point, It, in the framing, by means o'f'which lever extending beyond the pivot h a heavy ball, H, is supported, which tends to balance the weight of the slide-valve" and its connections. As the valve is worked the lever of which'is controlledby the governor at rapidly-recurring intervals; while it is also held very strongly against any movement except such as the governor shall indicate. The action of the block 'm. on'the curved piece E tends to disturb the position of the piece E and of the several connections IJ K. At each revolution the rod K is pressed upward, and then again downward with considerable force. Such force would tend to disturb the action of the governor but for the provisions which I have introduced. The slide K is guided so that it is only capable of a strictly vertical motion. It carries a pin, 70 which is received in an oblique slot, 1, in a horizontal slide, I), which latter is operated to the right or left by the bell-crank lever P, according as the governor-balls rise or sink, as will be obvious.

As the center of the block m revolves in its distorted elliptical path there are four points where there is no tendency to disturb the position of those parts. Two of these points are at the opposite ends of the throw of the valve. Here the block exerts no tendency to disturb anything, for obvious reasons. There are also two points in its traverse when the center of the block m is coincident with the prolonged axis of the pivot 0. Here any force exerted by the eccentric, and, consequently, by the block m however great it may be, in the upward or downward. direction is evidently unfelt by the armE and by the connections I J K, because it is exactly on the center of the turning piece E E. When the engine is cutting off at its shortest these points nearly coincide with the pointsbefore named-viz.-, those at the end of the motion of the valve. When the steam is allowed to follow further these points may come in widely-differing parts of the circuit. The rod K is provided with an adjusting-nut, k, as represented, by which the length of the rod can be very nicely adjusted at will.

Operation.

The engine being supposed to be working with .a uniform load at a uniform speed, there is no change in therate of expansion, and the piece E maintains a fixed and uniform amount of inclination, but rising and sinking with each turn of the engine. If the piece E is in a horizontal position, or as nearly so as its curvature will allow, the valve receives an amount of up-and-down motion only equal to the conjugate axis of the imperfect ellipse described by the center of the block m. This motion is only sufficient to allow for the lead and loss, and will give very little steam to the engine. In other words, it cuts oil at the beginning of the stroke. When the governorballs sink and the slide moves, in consequence, to the left, so that the slide K and the rod K sink a little, the arm E is inclined more to the right and the piece E is inclined, and is thereafter held firmly in an oblique position. .In this oblique position the valve gets a greater throw by reason of the fact that the block m in making its long traverse laterally, induces a motion in the piece E and its connections additional to and peculiarly combined with the motion which is due simply to the vertical travel of the block m before referred to. It may not be necessary to give in this specification a prolonged mathematical analysis of the action. What I consider the best proportions are shown in the drawing; and as the obliquity of the piece E is increased or diminished the throw of the valve is increased or diminished.

The parts are so related that, as before re marked, any change of cut-oli' is felt equally on the up-stroke and down-stroke; and the same with the other changeable points, the point of admission, compression, and exhaust.

Some of the advantages due to certain features of the invention may be realized by the employment of only a portion of the combination; but I prefer the whole, as described. There may be little advantage in making the pin a adjustable. I, in fact, prefer to deter mine accurately the best position for this pin and its connected block N, and to fix it permanently in the frame A. A slightly-diflering effect, but nearly as good, may be produced by fixing the pin a on the lower arm M of the eccentric-strap and allowing the block M to traverse vertically in ways carried on the frame.

The arm E extending upward from the curved piece E is of exactly the same length as the upper part or arm J of the bell-crank lever- J. The rod I is also of exactly the same length as the corresponding part of the lever H. These relative proportions are important. They form a figure which, however it may be changed to be more or less diamond-shaped instead of square or rectangular, is always a parallelogram; and, however obliquely the curved piece E is set, it moves always in a position parallel to itself.

I claim as my invention- 1. The piece E attached to the valve-moving mechanism, in combination with a block, an, as specified, and caused to describe an approximate ellipse so as to operate therewith, substantially as herein set forth.

2. The eccentric-strap M M controlled on one side by the pin a and block N, and carrying on the other side a block, m adapted to operate in combination with a properlycurved pieele, E, as and for the purposes herein specifie 3. The adj Listing-arm E and controlling-rod I, with suitable means for adjusting the latter, arranged to serve'relatively to the piece E, valve-stem G, and block on on the eccentricstrap M M as herein specified.

4. The lever H connected to the valve-stem G, and guiding the latter, in combination with the block m operated as shown, and with the piece E E and connections I J K, or their equivalents.

' In testimony whereof I have hereunto set my hand this 28th day of August, 1872, in the presence of two subscribingwitnesses.

Witnesses: GEO. H. BABCOCK.

S. W1Lcox, v I

ARNOLD HtSRMANN.

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