Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION:
Fire Suppression System and Variable Pitch Fan
Assembly and Method of Operation Thereof
NAME(S) OF INVENTOR(S):
Dieter A. Tischler
FIELD OF THE INVENTION
The present invention relates to a fire
suppression system and variable pitch fan assembly, and to
a method of enhancing fire suppressant delivery to an
engine.
R~K~ROUND OF THE INVENTION
An engine compartment of a heavy industrial
vehicle contains mufflers, turbochargers, hot oil pipes,
and other operating components that generate heat. The
air in the operating environment of such heavy industrial
vehicle is often laden with particulate debris that is
highly flammable. To m; n;m; ze the risk of fire damage,
fire suppression systems have been developed for
installation within the engine compartment. Such a fire
suppression system has included a sensor that is capable of
detecting a fire, and a chemical discharge tank that
discharges a fire retardant chemical upon receiving a
signal from the sensor. The most commonly used form of
fire retardant chemical is a dry powder.
A difficulty arises with these fire suppression
systems. The cooling fan on a large engine moves 25,000 to
50,000 cubic feet of air per minute. The cooling fan tends
to blow such a large proportion of the dry powder-like fire
retardant chemical out of the engine compartment, that the
efficacy of the fire suppression system may be reduced.
One way to prevent the cooling fan from blowing fire
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retardant chemical out of the engine compartment is to shut
the engine down immediately upon receiving a signal from
the sensor indicating the presence of a fire and prior to
the discharge of fire retardant chemical. This approach
avoids the problem of air flow, but has the inherent
disadvantage of leaving the heavy industrial vehicle
stranded, possibly placing the driver in great danger as
for example in the middle of a burning wood chip pile or
land fill site, and risking damage to the engine.
In a further solution believed to have been
presented in the prior art, shutters on the engine were
closed upon the detection of a fire to prevent passage of
air through the engine.
SUMMARY OF THE INVENTION
The inventor has proposed here a method of
controlling the injection of fire retardant chemical into
an engine compartment that does not require the engine to
be shut down to be effective and does not require shutters.
The invention is an improvement for engines with variable
pitch fans, such as the variable pitch fan made by
Flexxaire Manufacturing Inc. of Edmonton, Alberta, Canada.
According to one aspect of the present invention
there is provided a fire suppression system and variable
pitch fan assembly, comprising:
a variable pitch cooling fan having a plurality
of blades, the blades having variable pitch, including a
push position, pull position and neutral;
a fire suppression system including a reservoir
of fire retardant chemical, the fire suppression system
having means to initiate discharge of fire suppressant upon
a fire being sensed;
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a temperature sensor for producing output
representative of the operating temperature of an engine to
which the variable pitch fan is to be attached;
a controller for controlling the pitch of the fan
5 blades in response to the output of the temperature sensor;
and
the controller being configured to immediately
move the blades of the cooling fan to the neutral position
upon a fire being sensed.
According to a further aspect of the invention,
there is provided a fire suppression system and variable
pitch fan assembly of claim 1 further including:
a fire sensor connected to provide a signal
indicative of a fire to the fire suppression system;
a switch operative in response to a signal
indicative of a fire to cause delivery of fire suppressant;
and
the switch being connected to the controller to
provide a signal indicative of the presence of a fire.
According to a still further aspect of the
invention, there is provided a method of controlling a
variable pitch fan of an engine, in which the engine has a
desired operating temperature and the variable pitch fan
has constant rotational speed, the variable pitch fan
having fan blades, the method comprising the steps of:
decreasing the pitch of the fan blades when the
engine temperature is below the desired operating
temperature of the engine;
increasing the pitch of the fan blades when the
engine temperature is above the desired operating
temperature of the engine; and
immediately moving the pitch of the fan blades to
neutral upon a fire being detected.
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These and other aspects and advantages of the
invention are described and claimed in the following.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will
become more apparent from the following description in
which reference is made to the appended drawings, wherein:
FIG. 1 is a schematic of a prior art variable pitch
fan and engine assembly; and
FIG. 2 is a schematic of a fire suppression system and
variable pitch fan assembly in accordance with the present
invention.
DETAILED DESCRIPTION OF THE Pn~ nRED EMBODIMENT
For the better understanding of the invention, a
prior art variable pitch fan and engine assembly will now
be described with reference to FIGURE 1. The variable
pitch fan assembly is made by Flexxaire Manufacturing Inc.
of Edmonton, Alberta, and has been installed on various
pieces of heavy equipment, such as woodchip arrangements
sold in North America under the designations D6H, D7H, D8N,
and D9N and made in the United States by Caterpillar Inc.
of Peoria, Illinois.
Engine 12 and variable pitch fan assembly are
positioned within an engine compartment 14. Engine
compartment 14 is from a piece of heavy equipment, a cab 16
of which is illustrated, such as the woodchip arrangements
noted above. Variable pitch cooling fan 18 is disposed
within engine compartment 14 and attached to engine 12.
The blades 21 of cooling fan 18 have plurality of blade
positions, including a push position (reverse blade
position), pull position (conventional or normal position)
and neutral position in which the rotation of the blades
continues and blocks air flow (air block effect). The pitch
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of the blades 21 may be varied in small angular increments
by actuator 23. An exemplary cooling fan is described in
United States patent no. 5,122,034. The air block effect is
described in published Canadian application no. 2,080,268.
A controller 20 is coupled to cooling fan 18 by means of
actuator cable 19 and actuator 23 and serves to adjust the
positioning of fan blades 21 by providing signals to the
actuator 23 along cable 19. A conventional sensor 22 is
provided for sensing the engine temperature. Sensor 22 is
coupled to controller 20 by means of a cable 24. Controller
20 receives power from battery 17.
The controller 20 works as follows. The engine
operating temperature is determined from manufacturer
specifications and is stored in the controller 20 as a set
point. An example is 180F The controller 20 is programmed
so that if the engine temperature is above the set point,
the pitch of the fan blades 21 is increased, and if the
temperature of the engine is below the set point, the pitch
of the fan blades 21 is decreased. The pitch of the fan
blades 21 is altered by the actuator 23 attached to the
variable pitch fan assembly. The rotation speed of the fan
is determined in conventional manner by the pulleys by
which it is attached to the engine 12. The controller 20
is also programmed so that, upon request (by pushing a
purge button on the control panel), the fan blades 21 may
be set to reverse pitch for a desired period of time to
purge the radiator of debris, dust, etc. The time duration
of the purge may also be set through the control panel.
Now referring to Fig. 2, an embodiment of the
invention is disclosed in which a fire suppression system
25 is attached to the equipment at a suitable location,
such as the cab 16, and includes a reservoir 32 of fire
retardant chemical having a discharge tube 26. A fire
sensor 28 of conventional design (for example, a heat or
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infra red sensor) is disposed within the engine compartment
14, for example attached to the engine 12. The fire sensor
28 provides a signal along cable 29 to fire suppression
control switch 27, which in turn is connected via cable 30
to the controller 20. The fire suppression equipment,
including the reservoirs 32 and sensor 28, is conventional
and available from such sources as Ansul Fire Suppression
Equipment, and Levitt Safety Limited, the latter having
offices in Edmonton, Alberta, Canada, and the former being
well known in the industry.
The use and operation of fire suppressant and
variable pitch fan assembly of Fig. 2 will now be
described. Upon receiving a signal from sensor 28, the
fire suppression control switch 27 sends a signal to the
controller 20 along cable 30. The signal on cable 30
activates an interrupt circuit which interrupts the normal
operation of the controller 20. Upon interruption of normal
operation, the controller 20 sends a signal to the actuator
23 causing the fan blades 21 to move to the neutral
position. The fire suppression control 27 then, with a
short delay of a few seconds (about 2-3 seconds), which
allows air within the compartment to settle down, initiates
a discharge of fire suppressant into the engine compartment
14. Once blades 21 have been moved to the neutral position,
cooling fan 18 will continue to rotate with the r.p.m. of
the engine, but there will be negligible air movement. In
addition, due to the air block effect of the fan blades
while rotating in neutral, even if the vehicle is still
moving, there will be effectively no flow of air into the
engine compartment. It is therefore preferred to allow the
fan blades to continue rotating even after the detection of
a fire to provide the air block effect for air moving into
the engine compartment.
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In an alternative embodiment, the cable 30 may be
omitted, and the sensing of a fire can be carried out by a
second fire sensor similar to the sensor 28 connected
directly to the controller 20. In this case, the controller
20 must be programmed to interrupt the variation of pitch
upon occurrence of a signal from the second sensor and move
the blades immediately to the neutral position.
The controller 20 may be the one supplied with
the variable pitch fan made by Flexxaire Manufacturing
Inc., of Edmonton, Alberta, Canada, since it already
includes an unused circuit that may accept the signal from
the switch 27 as an input and that may be used as an
interrupt circuit. Alternatively, the controller 20 may be
made using any of various microprocessors available on the
market programmed in accordance with the information
supplied in this patent document.
The invention is not limited by the type of fire
suppressant used. In addition, upon the occurrence of a
fire, conventional systems may be used to alert the
operator to the fire hazard.
It will be apparent to one skilled in the art
that modifications may be made to the illustrated
embodiment without departing from the spirit and scope of
the invention.
