This model was submitted to the U.S. Patent Office with the application for the patent issued to W. P. Trowbridge, of New Haven, Connecticut, January 1, 1878, no. 198863; Automatic Boiler & Engine Co., assignee.
The model represents a small vertical coiled water-tube boiler provided with a stack or hopper in the center of the shell, which acts as a fuel reservoir to supply fresh fuel to the fire automatically.
The boiler consists of a cylindrical shell the base of which forms the ashpit above which the grates are supported. The shell above the grates is built with increasing diameter upward to form the firebox, and immediately above this is contracted for a short distance and then continues in a cylinder of constant diameter. Around the firebox and fitting closely to the shell is a single coil of tubing, which is continued up through the cylindrical portion where alternate coils are staggered slightly. Projecting downward within the coils is a second cylindrical shell closed at the top by a removable cover. This shell is used as a fuel reservoir and feeding device and also forms an annular passage with the outer shell which requires the hot gases of combustion to pass over the coils. The automatic fuel supply device is not shown or described.
Reference:
This description comes from the 1939 Catalog of the Mechanical Collections of the Division of Engineering United States Museum Bulletin 173 by Frank A. Taylor.
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