IMPROVEMENTS IN CHIMNEY HOODS AND VENTILATORS
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by Charles Hill Pennycook at the
Office of the Commissioners of Patents, with his Petition, on the 30th
September 1861.
I, CHARLES HILL PENNYCOOK, of Glasgow, in the County of Lanark, North
Britain, do hereby declare the nature of the said Invention of "IMPROVEMENTS
IN CHIMNEY HOODS AND VENTILATORS," to be as follows, that is to say:-
This Invention relates to improvements in apparatus designed to assist
the egress of smoke from chimneys or vents, and prevent down draught, and
also applicable for inducing and assisting the ingress or egress of air when fitted
to ventilating ducts.
The apparatus arranged as for a chimney hood consists of a cylindrical
shell formed or divided internally so as to present one or more helical or screw
shaped passages, and mounted upon an upright spindle so as to revolve as
freely as possible. The lower edge of the cylindrical shell dips down into
an annular trough formed in the bottom or part by which the apparatus is
fixed upon the chimney or vent, and to which the spindle is fixed. This
trough being filled with water which will be continually replenished by rain,
forms a liquid joint, and prevents interference with the internal current at
that part. A cap is attached to the drum or cylinder at a slight distance
above it, the smoke having free egress laterally or radially between the two.
The revolving cylinder and cap are both formed with external pocket-like
vanes having the sides inclined, but with no openings through into the interior
as with vaned hoods hitherto constructed. The slightest external air current

page_text: by acting on the vanes causes the hood to revolve, and the vanes being set
in a suitable direction relatively to the internal screw, the latter in turning
exerts an upward drawing or propelling action on the smoke. At the same
time the upper openings of the smoke passages, in consequence of their
helical form, baffle and prevent any tendency of the air to enter and descend, and
from the motion of the cylinder are as it were continually receding from any
inwardly directed current. To insure the hood's continuing to revolve freely,
a cup is provided to contain oil which keeps the bearing constantly lubricated.
This oil cup is opened by unscrewing the top cap, but an additional internal
screw plug is provided so that the hood may be handled without upsetting
the oil when the cap is off. To prevent noise, a washer or bearing piece of
leather or such like material is fitted in the tube surrounding the central
spindle, this soft material preventing concussion and friction between the
metal parts.
The apparatus constructed as described is applicable as a ventilator to
assist the egress of air, but to assist the ingress of air, the internal screw
passages must be reversed, the external vanes remaining the same, or vice
versâ.
As the rotatory speed of the screw cylinder may be too great sometimes, and
particularly in some applications, as, for example, on railway engines and car-
riages, this Invention further contemplates the application of an appliance such
as a frictional brake for moderating the speed, the action of such appliance
depending on the centrifugal force arising from the rotation.