AN IMPROVED METHOD OF AND APPARATUS FOR VENTILATING PURPOSES
Year: 1876

page_text: LETTERS PATENT to John Denis Macdonald, M.D., of Weston Grove Road,
Woolston, in the County of Southampton, Deputy Inspector General of
Hospitals and Fleets, for the Invention of "AN IMPROVED METHOD OF AND
APPARATUS FOR VENTILATING PURPOSES."
Sealed the 9th March 1877, and dated the 12th September 1876.
PROVISIONAL SPECIFICATION left by the said John Denis Macdonald
at the Office of the Commissioners of Patents on the 12th September 1876.
JOHN DENIS MACDONALD, M.D., of Weston Grove Road, Woolston, in the County
of Southampton, Deputy Inspector General of Hospitals and Fleets. "AN IMPROVED
METHOD OF AND APPARATUS FOR VENTILATING PURPOSES."
This Invention is a twin fan automatic ventilator consisting of three essential
parts, viz. -1, a rotatory fan to which motion is imparted by, 2, a motile fan
on the same axis revolving with the wind, and, 3, a self-adjusting versatile cap
so planned as to direct the action of the wind upon the motile fan to the best
advantage.
1. One side of the rotatory fan is (for aspiration, see Fig. A), turned downwards
on the Drawing forming part of this Spection over the mouth of the shaft, or
any opening through which the air is to be extracted, whilst the other side is cut
off from the external air by a transverse septum between it and the motile fan.
The exhaustive action of the lower or aspiratory fan is therefore confined to the air
within the shaft, which is thus elicited and thrown off in all directions by
centrifugal force.
2. The motile fan is composed of several concave blades or cups erected upon the
before-mentioned transverse septum, or fixed at equal distances around the axis.
In the amount of resistance offered to the wind, the concave side of the blades
exceeds the convex by about one-fourth, so that motion in one direction only is
determined by this difference.
3 The self-adjusting cap is constructed with the view of still further counter-
acting the resistance of the convex side of the motile blades by interruping the
wind, which would otherwise tell upon them to a disadvantage. To effect this the
alternate quarters of the cap are closed, and held in the required oblique position to
[Price 6d]

page_text: the direction of the wind by a transverse symmetrical vane at the top, by which
also the cap is hung upon a central pivot. The concave side of each blade is thus
alone exposed to the wind, while the convex side comes up under one of closed
quarters of the cap with much diminished resistance. Moreover, the closed distal
quarter of the cap is so arranged as to reflect the current of air in the direction
of the movement, and thus supplement the primary force.
4 As above described the apparatus is adapted for aspiration, but by simply
reversing the lower fan, and introducing it within the chamber to be ventilated, it
will become propulsive, as shewn in Fig. B, in the Drawing,
5. The accessaries worthy of notice are two cross rods bent twice at right
angles which form a light cage or framework carrying the pivot for the cap and
the socket for the upper pivot of the fan spindle, the lower pivot of which moves on
a transverse piece within the shaft in the aspiratory form (A), and in a socket at
the centre of a circular plate in the propulsive form (B) of the apparatus.
For the ventilation of circumscribed spaces, e.g., railway carriages and the cabins
of ships, both egress and ingress must be provided for without draught, and con-
sequently both forms of this arrangement would be necessary For ship ventilation in
particular the aspiratory form would be required, for air shafts opening on the poop
and t-gallant forecastlo, & to surmount the hollow iron lower masts. It might also
be employed to promote an up draught in chimneys & smok shafts.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Denis Macdonald in the Great Seal Patent Office on the
12th March 1877.
JOHN DENIS MACDONALD, M.D., of Weston Grove Road, Woolston, in the County
of Southampton, Deputy Inspector General of Hospitals and Fleets "AN IMPROVED
METHOD OF AND APPARATUS FOR VENTILATING PURPOSES."
-
This Invention is a twin fan automatic ventilator consisting of three essential
parts, vis.1, a rotatory fan, to which notion is imparted by (2), a motile fan
on the same axis revolving with the wind, and, (3), a self-adjusting versatile cap
so planned as to direct the action of the wind upon the motile fan to the best
advantage
(1.) One side of the rotatory fan is for aspiration turned downwards over the
mouth of the shaft or any opening through which the air is to be extracted, whilst
the other side is cut off from the external air by a transverse septum between it
and the motile fan. The exhaustive action of the lower or aspiratory fan is there-
fore confined to the air within the shaft, which is thus elicited and thrown off in
all directions by centrifugal force.
(2.) The motile fan is composed of several concave blades or cups erected upon
the before-mentioned transverse septum, or fixed at equal distances around the axis.
In the amount of resistance offered to the wind, the concave side of the blades
exceeds the convex by about one-fourth, so that motion in one direction only is
determined by this difference
(3) The self-adjusting cap is constructed with the view of still further counter-
acting the resistance of the convex side of the motile blades, by interrupting the
wind, which would otherwise tell upon them to a disadvantage. To effect this the
alternate quaiters of the cap are closed and held in the required oblique position to
the direction of the wind by a transverse symmetrical vane at the top, by which
also the cap is hung upon a central pivot. The concave side of each blade is thus
alone exposed to the wind, while the convex side comes up under one of the closed
quarters of the cap with much diminished resistance. Moreover, the closed off side
quarter of the cap is so arranged as to deflect the current of air in the direction of
the movement, and thus supplement the primary force.
(4) As above described the apparatus is adapted for aspiration, but by simply

page_text: Fig. 1 is an elevation of my improved twin fan automatic ventilator, shewn in
position for extraction; Fig. 2, clevation shewn in position for propulsion.
In these Figures a is the common axis of the fans, b is the upper, and c the
lower axis of same; d (Fig. 1), transverse piece or cross bearing lower axis c,
and within the lower border of a metallic collar fitted to the opening; e, iron
framework bearing; f, the pivot of the cap with its safety key above and b
beneath it; g, the cap, to which is fitted the transverse vane h; 3 is the motile
fan, k, the lower rotatory fan, which in the centre is hollow to admit air to
the said fan. In Fig 1, the hollow is below and air is admitted (as shewn
by the arrows) on to the fans; in Fig. 2, the air is admitted above through
the opening on to the vanes of fan k, as shewn by the arrows; d¹ (Fig. 2) is a
circular plate bearing the socket c, and secured to the boarding of the roof at the
circumference.
Fig. 3 is detail view, shewing cap g with the transverse vane h in edge view.
Fig. 4 is detail plan view of the iron framework or cross rods bearing for cap.
Fig 5 shews by elevation my improved arrangements for ventilating drains,
same being also applicable to chimney tops. In this arrangement I use a ventilating
tube fixed into the summit of the soil end of the syphon pipe in the closet, and at
the upper end of the said ventilating tube I fix my twin fan ventilator, same being
at the top of the house clear of all windows, so that the noxious gases are drawn up
and thrown out clear of the house; in this Figure a is the pan of the W.C.; b, the
syphon; c, the soil pipe; d, the ventilating tube; e, the aspiratory fan. This
airangement is shown with a truncated cone, the cone (with aspiratory fan) being
shewn separately in Figures 6 and 7, in Fig 7, the frustrum of the cone is inverted or
the base upwards, provision being made by leaving an interval, except when secured
by ties, between the lower margin of the cone and the upper end of the shaft for the
moisture or rain to escape. In Figs. 5 and 7 the twin fan ventilator may be used
without the cap, as shewn; in Fig. 6, the said frustrum of the cone is formed with
the base downwards, as shewn, and the noxious vapours or smoke (when applied to
a chimney) issues out in direction shewn by the arrows. The top of the frustrum
is closed with a circular plate which cuts off communication with the shaft above.
Sometimes, especially for use in ventilating ships, railway carriages, and such
like, I fix my twin fan ventilator on a shaft so constructed as to allow ingress of fiesh
air and egress of vitiated air; this I effect in manner following which is shown in

page_text: Fig. 8 of the accompanying Drawings) -The shaft a is divided by a longi-
tudinal septum b into two equal parts, which septum is closed, except as regards
an opening on one side above and the opposite side below, the closed portion
being at either end in communication with the central tubes (c and d) It will
thus be seen that by such divisional arrangement the fresh air finds ingress centrally
below at c, while it is circumferential above at c¹. On the other hand, the egress of
vitiated air is circumferential below at d and central above at d¹, where it is in
communication with the aspiratory fan, shewn by the Drawing; Fig. 9 is a cross
section on line A, B, Fig 8.
Having now particularly described and ascertained the nature and object of the
said Invention, and in what manner the same is to be performed or carried out in
practice, I hereby declare that I claim the Invention of an improved method of
and apparatus for ventilation, in which substantially similar arrangements of
rotatory fan, motile fan, self-adjustable versatile cap, and ventilating shaft with
central ingress and egress delivery, to those above described are important and
peculiar points or features
o
•
In witness whereof, I, the said John Denis Macdonald, have hereunto set
my hand and scal, this Ninth day of March, in the year of our Lord One
thousand eight hundred and seventy-seven.
Witness,
SAMUEL ROSS FRYER,
Woolston.
JOHN DENIS MACDONALD, M.D. (L.S)