A Catechism of the Steam Engine Part 34

The general arrangement is that of a Steam Cylinder, the piston rod of which, carried through into the water cylinder and attached directly to the water plunger, works back and forth without rotary motion, and of course without using either crank or fly wheel.

[Ill.u.s.tration: Fig. 62.]

In the figures, _a_ is the Steam Cylinder--_b_, the Steam Chest--_d_, a handle for regulating the steam valve--_f_, the starting bar _g, g_, tappets attached to the valve rod, which is moved by the contact of the arm _e_, on the piston rod with said tappets--_h_, the double-acting water plunger working through a packing ring--_o, o_, force valves--_o', o'_, suction valves. The pump piston is represented as moving from right to left, the arrows indicating the course of the water through the pa.s.sages.

The suction valves _o'_, on the right side, and the force valves _o_, on the left side, are show open; _x_, is an air chamber made of copper; _s_, the suction pipe terminating in a vacuum chamber; made by prolonging the suction pipe, and closing it perfectly tight at the top, the connection being made to the pump by a branch as shown; _m, m_, are hand-hole plates, affording easy access to the water valves; _n, n_, small holes through the plunger, which relieve the pressure near the end of the stroke, to give momentum to throw the valves when working at slow speed.

[Ill.u.s.tration: Fig. 63.]

Fig. 63 is a perspective view of H.R. Worthington's Duplex Steam Pump. The prominent peculiarity of this pump is its valve motion. As seen in the cut, two steam pumps are placed side by side (or end to end, if desired). Each pump, by a rock shaft connected with its piston rod, gives a constant and easy motion to the steam valve of the other. Each pump therefore gives steam to and starts its neighbor, and then finishes its own stroke, pausing an instant till its own steam valve, being opened by the other pump, allows it to make the return stroke.

This combined action produces a perfectly positive valve motion without dead points, great regularity and ease of motion, and entire absence of noise or shock of any kind. Both kinds of pumps are made by Mr.

Worthington, of various size according to the requirements, the duplex being used for boiler feed and for the supply of cities with water.

Fig. 64 is a side elevation of the Woodward Steam Pump. The pump is direct acting. The steam and water piston being on the same rod, but momentum is obtained to throw the valves by means of a fly wheel, placed beyond the pump, and connected with the piston rod by a cross head and a yoke. The machine is simple in its construction and action, and is extensively used.

Giffard's Injector, both in Europe and this country, is quite extensively used to supply the place of a pump, as independent feed for all cla.s.ses of boilers. It is represented in elevation and section, figs. 65 and 66.

[Ill.u.s.tration: Fig. 64.]

[Ill.u.s.tration: Fig. 65.]

[Ill.u.s.tration: Fig. 66.]

_A_, steam pipe leading from the boiler. _B_, a perforated tube or cylinder, through which the steam pa.s.ses into the s.p.a.ce _b_. _C_ screwed rod for regulating the pa.s.sage of steam through the annular conical s.p.a.ce _c_, and worked by the handle _d/_. _E_, suction pipe, leading from the tank or hot well to small chamber _m_. _F_, annular conical opening or discharge pipe, the size of which is regulated by the movement of the tube or cylinder _B_. _G_, hand wheel for actuating the cylinder _B_. _H_, opening, in connection with the atmosphere, intervening between discharge pipe _F_ and the receiving pipe through which the water is forced. _I_, tube through which the water pa.s.ses to the boiler. _K_, valve for preventing the return of the water from the boiler when the injector is not working. _L_, waste or overflow pipe. _M_, nut to tighten the packing rings _g_ and upper packing _i_ in cylinder _B_. _N_, lock nut to hold _M_.

The pipe _A_ is connected with the steam s.p.a.ce of the boiler at its highest part, to obtain as dry steam as possible. The pa.s.sage of the steam into _A_ is controlled by a c.o.c.k, as is also the feed pipe to the boiler. In working, both are opened, the steam pa.s.ses through _A_ into the s.p.a.ce _b_, and issuing through the nozzle _c_ with the pressure due to its head, and a partial vacuum by its contact with the feed water, it drives this water in connection with the jet through the pipe _F_ into the pipe _I_ in connection with the water s.p.a.ce of the boiler.

_Method of Working._--Turn the wheel so as to permit a small quant.i.ty of water to flow to the instrument. Open the steam c.o.c.k connecting the apparatus with the boiler. Turn slightly the handle, which will admit a small quant.i.ty of steam to the apparatus; a partial vacuum is thus produced, causing the water to enter through the supply pipe. As soon as this happens, which can be observed at the overflow pipe, the supply of steam or water may be increased as required, up to the capacity of the instrument, regulating either by means of the wheel and handle, so as to prevent any overflow. The quant.i.ty of water delivered into the boiler, may be varied by means of the stop c.o.c.ks on the steam and water pipes, without altering the handles on the injector; a graduated c.o.c.k on the water supply pipe is very convenient for this purpose.

The machines are manufactured by Wm. Sellers & Co. Philadelphia.

As an example of Portable Steam Engines, of which there are large numbers in this country of different manufacturers, we give the representation (fig. 67) of one made by J.C. Hoadley, of Lawrence, Ma.s.s.

[Ill.u.s.tration: Fig. 67.]

In these machines, the rules and proportions of the locomotive engine are adapted to the requirements of stationary power, for all purposes under forty horse power. The leading ideas are: high velocity, high pressure, good valve motion, large fire-box, numerous and short flues, and steam blast. The characteristic features are: great strength of boiler, fully adequate to bear with safety 200. lbs. pressure per sq. in., great compactness and simplicity, large and adjustable wearing surfaces, and the entire absence of all finish, or polish, for mere show.

The cylinder is placed over the centre of the boiler, at the fire-box end, so that the strain due to the engine is central to the boiler (which serves as bed plate); the starting valve is under the hand of the engineer when at the fire door; and both ends of the crank shaft are available for driving pulleys.

For the sake of compactness, the cylinders are set low, by means of a depression in the boiler between the stands of the crank shaft, to admit of the play of the crank and connecting rod. All the parts are attached to the boiler, which is made of sufficient strength to bear all extra strain due to the working of the engine.

They have feed water heater, force pumps, Jackson's governor and valve, belt for governor, belt pulley, turned on the face, steam gauge; everything, in short, necessary to the convenient working of a steam engine. All engines are fired up and tried before they leave the shop, and they are warranted tight, safe, and complete.

A strong and convenient running gear, so arranged as to be easily attached and detached at pleasure, is furnished, if desired; forming, when separate, a useful wagon.

[Ill.u.s.tration: Fig. 68.]

Fig. 68 is a compact vertical engine, as built by R. Hoe & Co., of this city. It is intended to drive printing presses, but is adapted to any kind of work, and is especially suited to such places as require economy of s.p.a.ce. Although the value of expansion has been called in question by some of the engineers of the United States Navy, and under an appropriation from Congress is now to be made the subject of experiment; yet, in almost all the manufactories and workshops of the United States, no matter what the form of steam engine, or the purposes to which it is applied, whether stationary, locomotive, or marine, some form of cut-off, by which expansion of the steam can be availed of, is considered indispensable. Many varieties are in use, but those engines are most popular in which the cut-off is applied directly to the valves on the cylinder, opening them quickly and shutting off almost instantly, avoiding all wire drawing of the steam at the ports, and regulating the speed of the engine promptly. Of this cla.s.s of engines, those manufactured by the Corliss Steam Engine Company, of Providence, R.I., are perhaps the widest known, not only for their extensive introduction, but also from having, by a long and successful litigation, established the claims of the patentee, Mr. George H. Corliss.

[Ill.u.s.tration: Fig. 70.]

Fig. 70 is a section of the cylinder and valve chests of a horizontal Corliss engine. _S_ is the steam connection, and _E_ the exhaust; there are two distinct sets of valves, the steam _s, s'_, and the exhaust _e, e'_, operated independently of each other. In their construction the valves may be considered cylindrical plugs, of which portions near the ports are cut away to admit the steam and reduce the bearing surface; the valves are fitted on the lathe and the seats by boring. The motion given to the valves is rocking, but it will be observed that the valves are not firmly connected to the rocking shaft or cylinder; in the figure the valves are shown shade lined, and the shaft or stem plain; in this way the valves are not affected by the packing of the valve stem, but always rest upon the face of the ports. In the figure the piston is just about to commence its outstroke, the movement of the steam is supposed to be represented by the arrows; the inner steam valve _s_, and the outer exhaust _e'_, are just beginning to open. It will be observed that the outer steam _s'_ is fully closed, whilst the inner exhaust valve _e_ is but barely so, showing that there has been a cut-off on the steam valve, but no lead to the exhaust, that it was left fully open till the completion of the stroke.

[Ill.u.s.tration: Fig. 71.]

Fig. 71 is a side elevation of the cylinder, with the valve connections with the governor. _S_ is the steam pipe; _s, s'_ handles to the steam valves, and _e, e'_ to the exhaust valves, shown in dotted line in fig. 70.

The handles to the exhaust valves are connected directly to a rocking plate _R_, to which motion is given by a connection _x_, with an eccentric on the engine shaft. When once set, therefore the movement of the exhaust valves is constant, and they will always be opened and closed at the same point of the stroke. Connected with the rocking plate _R_, and on opposite sides of its centre, the same as the exhaust valve connections, there are two levers, vibrating on a centre _c_, of which one only is shown, as it covers the other; to the upper ends of these levers pawls are attached, one end of which rests on the stems or rods connected with the handles _s, s'_, of the steam valves; on these stems there are notches against which the pawls strike, and as the levers vibrate inward they push back the stems and thereby open the valves, and this continues for the whole length of the inward motion of the levers, or till the outer extremities of the pawls come in contact with the end of the short lever _l_, which, pushing down the outer end of the pawls, relieves the stems at the other ends, and the valve stem returns to its place through the force of springs attached to the outer extremities of the valve stems _a_, are cylindrical guides to the valve stems, at the inner extremities of which are air cushions. The lever _l_ is connected directly with the governor. As the b.a.l.l.s rise, they depress the extremity, which comes in contact with the pawls sooner, and thereby shut the valves earlier; and on the contrary when the b.a.l.l.s are depressed, the valves remain open longer; as the pawls come in contact with the stems always at one point, the steam valves open constantly, but are closed at any point by the relief of the pawls, according to the speed of the governor.

Fig. 71 represents, partly in section and partly in plan, the cylinder, steam chests, valves, &c., of one of the Woodruff & Beach high pressure Engines, Wright's patent.

Fig. 72 represents, in elevation, the cam shaft, to the upper end of which, not shown in the drawing, is attached the ordinary centrifugal governor.

The cylinder, steam chests, valves, &c., being similar to those of other engines, need no special notice; but the cam for opening and closing the steam valves, fig. 72, requires particular attention, as it embodies a beautiful and simple device for cutting off the steam with certainty at any part of the stroke, the motion being produced automatically by the action of the governor on this cam, throwing it more or less out of centre with the spindle of the governor, as the rotation of the b.a.l.l.s is less or more rapid, the eccentricity of the cam determining the amount of steam admitted to the working cylinder of the engine. To produce this effect the cam is made as follows:

_C_ is a hollow cylinder or sh.e.l.l, with a part of one end formed into a cam proper. Throughout the whole length of this piece, upon the inside, there is a spiral groove cut to receive one end of a feather, by which its pitch or eccentricity is regulated. _C'_ is also a hollow cylinder or sh.e.l.l, of the same length and diameter as _C_, with a similar spiral groove cut on the inside, the outside being perfectly smooth and plain, upon which the toe (_t_) for closing the valves is fastened. The inside piece consists of two hubs _D, D'_, eccentric with each other, and made in one piece, _D_ being turned to exactly fit the inside of the sh.e.l.l _C_, and _D'_ to fit the sh.e.l.l _C'_, the hub _D'_ having a socket (_c_) into which the spindle (_s_) of the governor is screwed; the end (_d_) of the hub _D_ forming a journal or bearing, with a bevel wheel on its extremity to convey motion from the crank-shaft gearing to the governor and cut-off. There is a hole throughout the length of the inside hubs _D_ and _D'_, which is continued through the spindle of the governor, and contains the rod (_r_) that connects the cam with the governor. This hole is eccentric to the outside surface of the hub _D_, as well as to the sh.e.l.l _C_, and concentric with the hub _D'_ and sh.e.l.l _C'_, and with the governor rod (_r_).

The sh.e.l.l _C_ and hub _D_, and sh.e.l.l _C'_ and hub _D'_, are connected together by feathers; one piece of each feather is of a spiral form, and the other a straight or rectangular piece, the two being connected together by a stub on the rectangular piece, which fits into a hole or bearing in the other or spiral piece, so that the latter can turn on the stub and accommodate itself to the groove in which it has to work. The spiral part of each feather works in the spiral groove on the inside of its corresponding sh.e.l.l _C_ and _C'_ respectively, and the rectangular pieces work in a straight groove cut in the hubs _D_ and _D'_, the inner parts of the rectangular pieces being fastened to the governor rod (_r_), so that the feathers are permanently connected with the governor.

The sh.e.l.l _C'_ revolves inside of two yokes (_y_) and (_y'_), one attached to each steam-valve toe, (_a_) and (_a'_) respectively.

On the inside of each yoke, and opposite to its valve-toe, is a raised piece, against which the closing piece (_t_) on the sh.e.l.l (_C'_) acts to close the valves.

This sh.e.l.l (_C'_), as before noticed, has a spiral groove on its inside, similar in all respects to that in the cam-sh.e.l.l (_C_); and being acted upon in the same manner and through the same rod by the governor, it is evident that the closing piece (_t_) on its outside will always hold the same relation to the opening toe on the lower or cam-sh.e.l.l (_C_); and whatever alteration is made in the one, a corresponding alteration takes place in the other, thereby insuring the closing of the valves at the proper time at every point of the variation of the cut-off.

When the several pieces above described are put together, the apparatus for opening and closing the valves and producing the cut-off is complete, as shown in fig. 72, and it operates as follows:

[Ill.u.s.tration: Fig. 71.]

[Ill.u.s.tration: Fig. 72.]

Motion is communicated by gearing from the crank-shaft to the bevel wheel on the piece (_d_) on the end of the hub _D_, and is communicated to the spindle of the governor, which is screwed into the socket on _D'_. As the b.a.l.l.s rise or fall, through change of centrifugal force due to the variation in the speed of rotation, they raise or depress the governor-rod, which pa.s.ses through the spindle and the hubs _D'_ and _D_, and is attached to the feathers, thereby raising or depressing the feathers, which, acting on their respective spiral grooves, instantly alters the lift of the cam on the sh.e.l.l (_C_), and brings the closing toe (_t_) on the sh.e.l.l (_C'_) into proper position for closing, and so regulates the amount of steam admitted to the cylinder.

[Ill.u.s.tration: Fig. 71.]

Consequently, any speed may be selected at which the load of the engine is to move, and any variation from that will be instantly felt by the governor, and corrected by this simple and beautiful device. There is no jar in the working of the parts; the feathers move noiselessly in their grooves; the governor rod moves up and down through the spindle and the hubs _D_ and _D'_, and can be regulated by hand to give any required opening of the steam ports to suit the work to be done. Any change in the amount of work will then alter the speed of the engine, and so affect the governor and cam, as before said.

It is unnecessary to insist on the great economy attained by using steam with a well-regulated cut-off, for practical men know now that the essential points of excellence in the steam engine are a good boiler, which generates the greatest quant.i.ty of steam for the least consumption of fuel; and, secondly, a reliable cut-off, which uses the steam to the best advantage, by admitting the proper quant.i.ty for the work required.

STEAM FIRE ENGINES.--Portable engines for the extinguishment of fires, are an American invention, and to Messrs. A.B. & E. Latta, of Cincinnati, working on the right principles, is due the credit which they claim in their circular, as follows:

"We claim to be the _original_ and first _projectors_ of the _first successful steam fire engine_ in the world's history. There have been many attempts at making a machine of such construction as would answer to extinguish fires; but none of them proved to be available in a sufficiently short s.p.a.ce of time to warrant their use as a fire apparatus. We hold that a steam fire engine should be of such nature as to be brought into requisition in as short a s.p.a.ce of time as is necessary to get the machine on the ground, and the hose laid and ready to work: that is, supposing the fire to be within one square of the place where the steamer is located. The object in locating a machine at any point is to protect that immediate vicinity; and it is therefore absolutely necessary to have it available in the shortest s.p.a.ce of time, and that with unerring certainty. We think that reliability is of the greatest importance to the protection of a city from fire, as everything is dependent on the _working_ of such apparatus in time; and for this reason no expense should be spared on this kind of machinery."

Fig. 73 is a representation of one of the Messrs. Latta's fire engines, of which there are many of different cla.s.ses, according to the requirements; they say that they can furnish engines as low as $1,000, and have made some for $10,000.

The first peculiar feature of this engine is the boiler; it differs entirely from all boilers now in use.

[Ill.u.s.tration: Fig. 73.]