Source : United States Patent Office
Title: Hot Air Engine
Inventor : Philander Shaw, of East Abington, Massachussets
Date: Patented May 2, 1854
Patent #: 10,868
Specification forming part of Letter Patent No 10,868, dated May 2, 1854; Reissued July 17, 1860, No. 1014.
To all whom it may concern:
Be it known that I, PHILANDER SHAW, of East Abington, in the county of Plymouth and State of Massachusetts, have invented certain Improvements in Hot-Air Engines, of which the following is a full, clear, and exact description, reference being had to the annexed drawings, making part of this specification, in which—
Figure 1 is a plan of the engine; Fig. 2, a section on the line W, W, of Figs. 3 and 4, the shell of the auxiliary heater being removed to show the parts within; Fig. 3, a section on the line Y, Y, of gi. 1; Fig. 4, a section on X, X, of Fig. 1; Fig. 5, an enlarged section of the main heater on Z, Z, of Fig. 2.
The nature of my invention consists firstly in the employment of auxiliary heaters, which are so connected together and with each other by means of valves that the air for the supply of the engine shall be pumped in against the minimum pressure within the main heater, while it is worked off at the maximum pressure.
My invention also consists in passing the exhaust air from the cylinder together with the smoke and heated gases from the furnace through the auxiliary heaters in one direction while the air for the supply of the engine is caused to pass in the contrary direction through tubes within these auxiliary heaters by which means the heat is extracted from the exhaust air and smoke and transferred to the air on its way from the air pumped to the heater.
Great inconvenience has heretofore been experienced in the working of hot-air engines from the difficulty of obtaining a packing that will resist the great temperature to which the piston is liable to be raised; to remedy this inconvenience I have adopted the plan of refrigerating the piston by means of a constant stream of cold water which is made to circulate through its interior and thus preserve it at a temperature not exceeding that of boiling water.
To enable others skilled in the art to make and use my invention I will proceed to describe the method which I have adopted of carrying it out, describing first my separate improvements and finally the general operation of the complete engine.
A is the main heater into which the air is received from the auxiliary heaters, and in which it receives a final heating preparatory to being admitted to the working cylinder.
B is the fire box; C, the ash pit of the furnace beneath the heater A.
a are vertical tubes which pass entirely through the heater and through which the smoke and burning gases from the furnace pass.
D, is a chamber which entirely surrounds the heater and fire box, and which opens at the top into the chimney or smoke box E and communicates with the chamber beneath the furnace through the openings d, in its bottom plate, the object of which will be explained hereafter.
F is an air pipe of communication between the auxiliary and the main heaters which is entirely surrounded by the smoke flue G, and is furnished with a valve b, opening downward at its lower extremity.
H, is the auxiliary heater, which is divided into three sections or minor heaters H’, H’’, H’’’. these sections are separated from each other and from the ends of the heater by chamber, I, I’, I’’, I’’’, formed by close fitting partitions, f, f’, f’’, f’’’, f’’’’, f5, the chambers I, I1, I2, I3, communicating with each other through the tubes, c, c’, c’’, K, K’, K’’. The smoke from the furnace enters through the pipe G, into the chamber I’’’, thence it passes through the tubes, c’’, K’’, into the chamber I’’, thence through the tubes K’, c’, into the chamber I’, thence through the tubes K, c, into the chamber I, whence it passes off by the chimney M.
By the arrangement above explained it will be perceived that the compartments H1, H2, H3, are entirely shut off from the chambers, I, I’, I’’, I’’’, and from the smoke flues c, and K, which pass through them. They however communicate with each other through the short tubes, L, L’, these tubes are fitted at their advance ends with valves e, e’, the air from the force pump is admitted into these compartments in succession, passing through compartments in succession, passing through the tubes L and L’, and the valves e, e’, in a manner which will be hereafter more fully described.
N, is the working cylinder; O, the hot-air box which communicates with the heater A through the pipe P.
Q, is the hollow piston, the piston rod of which is also hollow as seen in Fig. 2.
g, is a tube inclosed within the hollow piston rod, and penetrating it at about the point h.
R, is a receptacle for water.
S, S’, are india rubber tubes from the top and bottom of this receptacle- which communicate one with the interior of the hollow piston, and the other with the small tube inclosed therein. By this means the water from the receptacle R, is caused to circulate continually through the hollow piston which is thus prevented from becoming injuriously heated as before mentioned.
T, is the discharge pipe from the working cylinder, which is made to enter the ash pit C, immediately beneath the grate bars, all the advantage resulting from urging the fire with heated air are thus obtained. The excess of the exhaust air not required by the fire passes through the openings d, into the chamber D, which incases the furnace, and off with the heated gases and the products of combustion through the flue G, into the chamber I3, whence they pass out in the manner already described. By thus passing the exhaust air into the chamber D I am enabled to economize the heat which would otherwise be radiated from the outside of the furnace.
The object of thus exhausting the hot air from the cylinder into the ash pit beneath the furnace is twofold; - firstly, the fire is urged with heated air; secondly, such portion of the exhaust air is not thus consumed passes with the products of the furnace into the auxiliary heaters where it is refrigerated by the fresh air entering from the force pump in a manner that will be presently explained.
V, is the force pump for supplying the heater with air, the area of its piston being about one half that of the working piston. Air is admitted to this pump through the valve g’, and escapes through valves in the top of the cylinder into the chamber h’, thence it passes by the pipe A’, into the compartment H’, of the auxiliary heater; here it circulates round the outside of the smoke passages and tubes c, K, and passes (when the pressure is removed from the main heater in the manner which will be hereafter explained) through the short communication pipes L, and valves e, into the compartment H’’, here it again circulates around the smoke pipe c’, K’, and through the pipe L’ and valve e’ into the compartment H’’’, - from this compartment it passes through the pipe F, and valve b, into the heater A.
It is evident that the auxiliary heater may consist of one or more compartments, there being always a valve communication between the last of such compartments and the main heater.
Operation: The air within the main heater A, as it expands closes the valve b, which thus prevents it from returning through the pipe F into the auxiliary heater H, a charge is then admitted to the working cylinder, the capacity of the heater A being such with relation to the working cylinder that when cut off at ¾ stroke or thereabouts the pressure within the heater A shall be very much reduced, the valves b, c’, c, then open, or as soon as the pressure in the compartments is reduced below what it is in the one behind it, — and the pressure for an instant is the same in all the compartments. The expansion caused by the extreme heat within the heater A soon closes the valve b, the valves c’, c being in like manner closed as the heat within the compartment H’’’ is greater than that within H’’, and so on, it being nearer to the furnace. The pressure within H, thus always remains at very near the minimum, and as the air is pumped into this compartment it is evident that it is only resisted by this minimum pressure, while it is worked off from the main heater A at its maximum pressure. The exhaust air from the cylinder as before stated enters the close ash pit C, and the fire is thus urged by a hot blast. That portion of the exhaust air not required by the fire passes off with the products of combustion, and is refrigerated in the auxiliary heater H, by the entering air. The exhaust air may be made to enter the auxiliary heater with the smoke from the furnace, and thus a portion of the advantages above described will be secured, but I prefer the exhaust beneath the fire for the reasons already set forth.
Several heaters and auxiliary heaters may be adapted to a single engine, a charge of air being taken from each in succession.
What I claim as my invention and desire to secure by Letters Patent is —
The within described auxiliary heater constructed and arranged as set forth, the exhaust air and the products of combustion being passed through in one direction while the cold air from the force pump is passed through in the other, by which means the heat is extracted from the heated air and smoke, and transferred to the cold air on its way to the engine, the latter being pumped in against a pressure much less than that at which it is worked off from the main heater as explained.
Witnesses: Sam Cooper John S. Clow