IMPROVEMENTS IN VENTILATORS
Year: 1878

page_text: LETTERS PATENT to Thomas Henry Blair, of Turnskey, in the County of
"
Tyrone, Ireland, for the Invention of IMPROVEMENTS IN VENTILATORS."
Sealed the 14th March 1879 end dated the 18th October 1878.
PROVISIONAL SPECIFICATION left by the said Thomas Henry Blair at the
Office of the Commissioners of Patents on the 18th October 1878.
THOMAS HENRY BLAIR, of Turnskey, in the County of Tyrone, Ireland.
PROVEMENTS IN VENTILATORS."
"IM-
My improved ventilator consists of a case made of metal or other material, in
which I suspend one or more thin plates of metal or other material, which plate or
plates are capable of coming in contact with the edges of an aperture in the front
of the case, thus forming a valve to prevent the down draught from a chimney or
external air from entering the room to be ventilated, but which allows the vitiated
air to escape.
This valve may be applied as an outlet ventilator in various positions to prevent
a back or down draught.
I will now describe the manner of suspending the plate or plates. Each plate is
supported by two vertical links so as to allow it to hinge freely on the points of
suspension, which are slightly above a line passing horizontally through the centre
of gravity of the plate. These links are sharpened at their upper ends and formed
into hooks to rest in countersunk holes in two sinall brackets attached to the case;
or these pointed ends and brackets may be replaced by loops forming hinges.
The motion of each plate is such as to ensure the free passage of vitiated air
passing through on all sides of the plate, the above-mentioned links being shaped
so as to allow the plate to recede equally from the four sides of the aperture.

page_text: Another way of performing my Invention is by attaching the upper ends of the
above-mentioned links to two vertical rods which rest in bearings on or near to the
bottom of the case, and extend nearly to the top, forming radius rods at each side
of the plate, the movement of which is limited by stops fixed inside the case.
These two radius rods may be made in either one or two pieces.
A cleat hinged to the case is provided for completely shutting the plate against
the edges of the aperture by means of pulling a cord.
I prefer to connect these radius rods at their upper ends by a cross wire upon
which hang the links suspending the plate; or the same object may be attained by
making the radius rods and cross wire all of one piece.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Henry Blair in the Great Seal Patent Office on the 17th
April 1879.
THOMAS HENRY BLAIR, of Turnskey, in the County of Tyrone, Ireland.
PROVEMENTS IN VENTILATORS."
"IM-
My improved ventilator consists of a case made of metal or other material, in
which I suspend one or more thin plates of metal or other material, which plate or
plates are capable of coming in contact with the edges of an aperture or apertures
in the front of the case, thus forming a valve to prevent the down draught from a
chimney or external air from entering the room to be ventilated, but which allows
the vitiated air to escape.
This valve may be applied as an outlet ventilator in various positions to prevent
a back or down draught from entering the room.
And in order that my Invention may be fully understood I will proceed to
describe the accompanying Sheet of Drawings.
Fig. 1 is a side elevation in section and Fig. 2 is a front view of a ventilator
constructed according to my improvements. a is the case, in front of which is the
aperture for the escape of the vitiated air; b is the plate or disc suspended by the
links c to the cross wire d, which cross wire is connected to or forms part of the
radius rods e, e, which rods rest in bearings fat or near to the bottom of the case;
h, h, are stops to prevent the ventilator opening too far; g is a cleat or lever for
closing the ventilator, when required, by means of a cord.
The mode of operation is as follows:-When the pressure of the air within the
room acts upon the plate b it causes the plate to recede bodily, carrying back the
links c and the radius rods e, and allowing the hot or vitiated air to escape, and in
case of any down draught occurring it carries forward the plate and immediately
closes the aperture.
The ventilator can be closed when required by means of the cord attached to the
clcat or lever g. The rods and links may be so adjusted that the plate. b will
remain either open or closed when there is no draught in either direction, and the
edges of the aperture in the case a are provided with india-rubber or other
cushions a¹ for the plate b to close against.
Fig. 3 is a side view and Fig. 4 a front view of a ventilator constructed according
to a modification of my Invention. In this arrangement I dispense with the
links c and cross wire d, and I suspend the plate b to the radius rods e, e, the upper
ends of which are hooked in the brackets a cast with the case, and the lower ends
are bent upwards and enter into the bearings f fixed to the lower edge of the
plate b.
When the pressure of air acts on the plate b it opens at the top until the edge
comes in contact with the radius rods e, and at the same time the lower edge is
opened by the action of gravitation. The plate b can be closed by the cleat g, as
before described.
In both the ventilators above described the plate b recedes equally or nearly
equally from the four sides of the aperture, thereby allowing the vitiated air to
escape freely whenever the pressure is sufficient to open the valve.
Having thus stated the nature of my Invention, and described two convenient
ways of performing the same, I wish it to be understood that I do not intend to
limit myself to the details given, as they may be considerably varied or modified;
and I claim the improved mode of supporting or suspending the valve plates of

page_text: ventilators, as shewn and described in reference to the accompanying Drawings,
and particularly the radius rods e, e.
In witness whereof, I, the said Thomas Henry Blair, have hereunto set my
hand and seal, this Sixteenth day of April, One thousand eight hundred
and seventy-nine.
T. H. BLAIK. (LS.)