[0001] The present invention comprises improvements relating to ventilators and concerns
controllable ventilators which are required to open to exhaust heat, smoke and fumes
from a building in the event of a fire and to close to conserve heat in the building
under normal conditions.
[0002] According to the present invention, such a ventilator comprises an opening flap
ventilator for buildings having a frame defining a ventilation opening, a hinged ventilation
flap for closing the opening, and springs for opening the ventilation flap characterized
by a fused fire prop pivotally mounted on the flap to swing round to engage an abutment
on the frame to prop the flap open in the event of a fire which might otherwise cause
failure of the springs.
[0003] With this arrangement, the ventilator may be opened by its springs in the event of
a fire, and this may be done automatically in response to the onset of a fire condition
using a suitable fire and/or smoke detector.
[0004] The fused prop then acts as an additional safety measure to prevent reclosing of
the flap.
[0005] A specific embodiment of ventilator in accordance with the present invention will
now be described by way of example, and not by way of limitation, with reference to
the accompanying drawings in which :-
FIG. 1 is a cross-section of a ventilator in accordance with the present invention
in an inclined mounted position and shown in its open and closed positions;
FIG. 2 shows an electric motor-gear drive mechanism of the ventilator with its gearbox
housing in cross-section; and
FIG. 3 is a view from the right hand end in Fig. 2.
[0006] With reference now to the accompanying drawings, the ventilator has a hollow frame
10 and a single, bottom hung, outwardly hingeing ventilator flap 11 to provide for
day-to-day and for fire ventilation hinged to the frame at 12. Gas springs 13, one
at each side, are provided for opening the flap 11, the flap then assuming its substantially
vertical position as shown in Fig. 1. An electric motor-gear drive mechanism 14 is
installed inside a hollow, top frame member 10
a of the ventilator about midway between the side frame members 10
b of the frame 10. The bottom frame member is indicated at 10
c. The unit 14 comprises an electric motor 15 and a gear drive mechanism 16 housed
in a gear box housing 17 adapted for flange mounting at 18 inside the ventilator top
frame member 10
a. The unit 14 has an output drive in the form of a winch pulley generally indicated
at 20 and disposed laterally to one side of the unit which is generally elongated
to fit within the hollow top frame member 10
a. The pulley 20 is fixedly carried by an output drive shaft 22 which also carries
the final gear 24 of a spur gear set 24, 26, 28 contained within the housing 17. The
gears 26 and 28 of the spur gear set are mounted on further drive shafts 30, 32. The
drive shafts 22, 30 run in ball races 34 and 36 carried by the housing 17. The drive
shaft 32 runs at one end in a ball race 38 carried by the housing 17, the shaft 32
also being rotatably supported concentrically within a hollow drive shaft 40 which
runs in a ball race 42 carried by the housing 17. The motor shaft 44 fixedly carries
a worm 46 which drives a worm wheel 48 fixedly carried by the shaft 40. The shafts
32, 40 carry laterally outside the housing 17, on the side opposite the winch pulley
20, the two elements 50 and 52 respectively of an electromagnetic clutch 54. The clutch
54, when energised, drivably engages the drive shaft 40 with the drive shaft 32 and
operation of the motor 15 in one direction or the other drives the pulley 20 to open
or close the ventilator.
[0007] In the closed condition of the ventilation flap in which the flap assumes its inclined
condition as seen in Fig. 1, the motor is de-energised but the electromagnetic clutch
54 remains energised by means of a separate electrical circuit. The ventilation flap
is secured closed when in its closed condition by the worm gear set 46, 48 which is
of a gear ratio which is incapable of being back driven. Thus, the gear drive mechanism
16 cannot be overhauled by tensioning the cable whilst the clutch 54 is energised.
[0008] In one arrangement, the clutch 54 is incorporated in a separate electrical circuit,
controlled by automatic fire response means, which maintains the clutch energised
so long as a power supply is available and no fire response is required, so that in
the event of a power failure, the ventilator opens automatically and cannot fail to
function as a fire ventilator under such conditions. In the present example, the electrical
circuit of the clutch 54 includes a smoke or fire detecting device operable to de-energise
the clutch to release the ventilation flap for automatic opening by its gas-springs
in the event of a fire being detected. However, the clutch may be incorporated in
the electrical circuit of the motor so that the clutch remains energised so long as
an electrical power supply is available to operate the motor and open the ventilator
in response to the operation of a smoke or fire detecting device. With this arrangement
the clutch operates simply as a fail safe device.
[0009] For day-to-day ventilation purposes, the ventilator may be opened by its gas-springs
13, upon de-energisation of the clutch 54, and closed by operation of the motor 15,
the clutch 54 then being energised. Alternatively the ventilator may be opened and
closed by operation of the motor.
[0010] In accordance with the invention, a fused fire prop 85 (see Fig. 1), pivotally mounted
on the frame of the flap 11 swings downwardly to engage an abutment 86 on the frame
10 to prop the flap 11 open in the event of a fire which might otherwise cause the
gas-springs 13 to buckle. The prop 85 is formed in two sections normally soldered
together as at 87. The prop sections may be joined together with a separate fusible
joint mechanically fastened to the sections of the prop. A spring 88 may be provided
to swing the prop downwardly and the flap 11 may carry a stop 90 to arrest the prop
in its operative position.
[0011] In the example described with reference to the drawings, the electric motor 15 has
an operating voltage of 24V DC, an output of 80 watts and a normal operating speed
of 3,200 r.p.m. The clutch 54 has an operating voltage of 24 volts DC. The output
torque of the gear drive mechanism 16 is 50 Nm at a speed of approximately 7 r.p.m.
The worm gear set has a gear ratio of 48 to 1 and the spur gear set a gear ratio of
10 to 1. The cable 76 is 2 mm diameter stainless steel wire.
[0012] It will be appreciated that the electric motor-gear drive units 14 which has been
described may be incorporated in other kinds of controllable ventilators used for
fire ventilation purposes, the cable 76 being connected to close, and to control the
opening of, e.g. a pair of hinged, oppositely opening ventilation flaps in a roof
mounted ventilator to close, and to control the opening of, the louvres of a controllable
louvred ventilator by spring action.
1. An opening flap ventilator for buildings having a frame (10) defining a ventilation
opening, a hinged ventilation flap (11) for closing the opening, and springs (13)
for opening the ventilation flap (11) characterized by a fused fire prop (85) pivotally
mounted on the flap (11) to swing round to engage an abutment (86) on the frame (10)
to prop the flap (11) open in the event of a fire which might otherwise cause failure
of the springs (13).
2. A ventilator as claimed in claim 1, characterized in that the opening springs (13)
are gas springs extendible to open the flap (11).
3. A ventilator as claimed in claim 1 or 2, characterized in that the ventilation
flap is hinged along its bottom edge and adapted to be opened into a substantially
vertical position from an inclined, closed position.
4. A ventilator as claimed in claim 1, 2 or 3, characterized in that the prop (85)
is formed in two sections normally soldered together (as at 87).
5. A ventilator as claimed in claim 1, 2 or 3, characterized in that the prop is formed
in two sections fixed together with a separate fusible joint mechanically fastened
to the sections of the prop.
6. A ventilator as claimed in any preceding claim including a spring (88) to swing
the prop downwardly and the flap (11) carries a stop (90) to arrest the prop in its
operative position.