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GB Patent: GB-178,201,321
Improvements and New Mechanism
James Watt - Handsworth, West Midlands, England

USPTO Classifications:

Tool Categories:
propulsion and energy : steam engines




Patent Dates:
Granted: Mar. 12, 1782

Patent Pictures:
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James Watt
1. Admits steam into the cylinder during a certain portion of the descent or ascent of the piston, and allows the elastic force of the steam admitted to press the piston through the remaining portion of its stroke.

2. Details an experiment with a model; finds with one-fourth of the steam used expansively he can do half the work.

3. Describes the parts and operation of the "single impulse "engine."

This is the first account, by the Patentee, of what he calls "my new invented engine, the sole use and benefit of which was "granted to me by an Act of Parliament passed in 1775." It exhibits the following peculiarities: the cylinder is completely closed; the piston rod is inserted into the piston with the "inverted cone;" it works through a "collar of leathers;" the cylinder is cased, and surrounded with steam; nozles enclose the " spindle valves " or puppet clacks; the "valve plates "and their " seats" are ground to fit each other; the valve is moved by a "rack and sector," and their "spindle" guided in a second "socket." The valves are lifted and returned to their seats by hinged levers moved by " tappets, on the plug frame;" the steam presses the piston downwards, and, when the stroke is completed, a communication is opened between the upper and under portions of the cylinder, and the piston rises in it without resistance. The packing of the piston is improved; the air and water are pumped out of the condenser, which is placed in a cistern of cold water, and the water is pumped from the "hot well" to supply the boiler.

4. Describes various contrivances for regulating the decreasing pressure on the piston of steam acting expansively, against the constant load of water in the pumps:—

?1. A wheel or sector is attached to the pump rod, and another to the piston rod, and so connected that the levers whereby they act on each other decrease and increase during the upward and downward movement of the piston, causing the piston rod to descend through equal spaces, and the piston rod to ascend through unequal spaces, exactly proportioned to the varying power of the steam.

?2. Chains wound on one spiral, fixed on the sector to which the piston is attached, and wound off another to which the pump rod is fixed.

?3. A friction wheel, suspended from one sector or wheel, and acting upon a curved or straight part of another sector or working beam.

?4. Causing the centre of suspension of the working beam to change its place during the stroke, whereby the leverage of the piston is increased as the steam expands.

?5. Placing on the working beam a heavy mass which acts against the pressure of the steam, at the commencement of the stroke, and with it, at its termination.

?6. Employing the surplus power of steam, in the first parts of its motion, to give velocity to a mass of matter, which, retaining that velocity, acts to increase the power of the piston, when the pressure of the vapour is decreasing. The action of a fly, which accumulates velocity in the first part of the stroke, and assists the action of the steam in the latter portion.

5. Employing steam to force the piston upwards as well as downwards, into a vacuum formed below and above the piston alternately. Describes the double impulse engine. A slight alteration of the single impulse engine converts it into one of the improved form, and simplifies the arrangement.

6. Compound engine. Connecting, by pipes, the cylinders and condensers of two or more engines, so that each can work pumps or machinery independently of the other connected with it, or concentrate the efforts of both to perform the same operation. The single and double engine may be worked with steam of uniform or decreasing pressure.

7. Connecting the pistons and pump rods to the working beam, by a toothed sector on the beam, working into a toothed rack on the piston rod.

8. Semi-rotative engine. A fixed hollow cylinder, closed, has an axle passing through it, on which a piston is fixed that extends from the axle to the circumference; an orifice on one side of the hinged or abutment valve opens to the boiler, and another orifice to the condenser. Each has a regulating valve. One of the steam valves being opened, and the condenser valve on the opposite side of the piston, the steam forces the piston round towards the condenser orifice; and on reaching it the steam and condenser valves are shut, and the opposite steam and condenser valves opened, which causes the piston to perform a retrograde movement, and transmit a vibratory movement to the axle and rods attached to it, which move the valves and condenser and air pump,

9. Rotative engine. A piston fixed on an axle rotates in a hollow cylindric ring. A hinged valve shuts against the surface of the axle, and divides the cylindric space, and falls back into a recess, so as to form a portion of the cylindric surface, and permit the piston in its revolution to pass over it. A pipe from the boiler opens on one side of the hinged valve, and one from the condenser on the other. The hinged valve being shut, or turned across the cylindric space, and steam being admitted into the space between it and the revolving piston, the latter is impelled towards the condenser orifice; on its reaching that limit the steam and condenser valves are closed, the hinged valve falls back into a recess in the circumference. The revolving piston having passed over, the hinged valve is again moved across the cylindric space; the steam valve is opened, and steam flows into the space between the hinged valve and the revolving piston, which is carried round the annular cylinder as before.

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