Note: Descriptions are shown in the official language in which they were submitted.
912~
The present invention relates to an improved
method and apparatus for reducing the oxygen concentration
of the air within a preservation room such as the ones used
for the conservation of fruits or vegetables, in an
energically efficient manner.
Apparatuses of the above-mentioned type are
already known and commercially available. These known
apparatuses are generally efficient but they all have the
disadvantage of consuming much energy thereby increasing
the costs of preservation of fruits or vegetables. This
disadvantage results from the very unefficient way the
energy supplied to these apparatuses is used.
An object of the present invention is to provide
an improved apparatus which overcomes the above described
disadvantage. More particularly, the invention provides
an apparatus comprising means for recovering and reusing
part of the energy already supplied to and consumed by the
apparatus. This apparatus may also be provided with means
for measuring temperature and thereby controlling the
utilization of the above mentioned consumed energy in a more
efficient way.
Another object of the present invention is also
to provide a improved method for reducing the oxygen con-
centration of air within a preservation room. In accordance
with the invention, this improved method comprises the
following steps:
- pumping the air from said preservation room;
- pre-heating said pumped air;
- heating said pre-heated air a~ a predetermined
temperature;
- mixing an inflammable gas with the air at said
predetermined temperature;
- burning said gas with the oxygen of said air
within a catalytic chamber, thereby reducing the oxygen
concentration of said air;
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- cooling said air with a reduced oxygen concen-
tration; and
- returning said cooled a:ir back to the preserva-
tion room;
- where.in said pre-heating step is carried out
by heat exchange with the air having a reduced oxygen
concentration before it is cooled, and by heat exchange
with the air heated through said heating step before it
is mixed with the gas.
Advantageously, this method may also comprise
the steps of measuring the temperature of the heated air
before it is mixed with the gas, measuring the temperature
of the air with a reduced oxygen concentration at the outlet
of the catalytic chamber, and controlling the air-heating
and gas-mixing steps as a function of the two measured
temperatures.
According to the present invention, there is also
provided an apparatus for reducing the oxygen concentration
of air within a preservation room, comprising:
- means for pumping the air from the preservation
room and circulating it within said apparatus;
- means for pre-heating said air pumped by the
pumping means;
- means for heating the pre-heated air at a
predetermined temperature;
- means for mixing an inflammable gas with the
air heated at said predetermined temperature;
- a catalytic combustion chamber wherein said gas
is burnt with the oxygen of said heated air thereby producing
air with a reduced oxygen concentration; and
- means for cooling the air with a reduced oxygen
concentration before returning it back to the preservation
room;
- wherein said pre-heating means comprises a first
heat exchanger for heat exchange between the air with a
reduced oxygen concentration prior its cooling and the air
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pumped by the pumping means, and a second heat exchanger
for heat exchange between the air heated by said heating
means and the air pumped by the pumping means.
The apparatus may also comprise means for
measuring the temperature of the heated air before it is
mixed with the gas, means for measuring the temperature
of the air with a reduced oxygen concentration at the
outlet of the catalytic chamber, and means for controlling
the heating means and gas-mixing means as a function of the
two measured temperatures.
Preferably, the second heat exchanger is incor-
porated to the heating means.
The advantages and other features of the present
invention will become apparent from the following non
restrictive description of the preferred embodiment thereof,
with reference to .he accompanying drawings, in which:
- Figure 1 is a general diagram of the apparatus
according to the present invention;
- Figure 2 shows in greater details the gas-mixing
means forming part of the apparatus of Figure l;
- Figure 3 shows dia~rammatically the electrical
circuit of the apparatus of Figure l; and
- E'igure 4 shows the spray water cooler forming
part of the apparatus of Figure 1.
The apparatus according to the invention as shown
in Figure 1 comprises a compressor 3 pumping the air from the
preservation room (not shown) via a first tube 18, a paper
filter 81 and a second tube 82. The compressor 3 supplies
the pumped air at a pressure that may be of 15 inches of
water through a tube 4 to the outer shell of an heat
exchanger 85 comprising an inner tube and an outer tube.
The inner tube is preferably made of stainless steel material
and the outer tube of steel material. A pressure switch 39
is provided at the outlet of the compressor 3 to stop this
~Z191;27
compressor and switch off the electric power supply of the
apparatus as will be explained hereinafter if the pressure
at the outlet of the compressor 3 becomes unsufficient.
The heat exchanger 85 heat the air at about 300F and supplies
the pre-heated air to a heater 7 through a tube 86. The
heater 7 is also provided with an inner tube 21 and an
outer tube concentrically disposed with respect to each
other. The annular passage defined by these two tubes
constitutes a second heat exchanger in which the air comin~
from the heat exchanger 85 is further pre-heated. The
bottom of the inner tube 21 is opened and slightly spaced
apart from the bottom of the outer tube of the heater
7 which is closed, to direct the air from the annular
passage of the heater 7 toward the inner tube 21 as shown
by the arrows on Figure 1. Two electrical heating coils
are provided and mounted in the inner tube 21 for heating
the air pumped by the compressor at 600F. A thermocouple
20 is disposed at the top of the inner tube 21 to measure
the temperature of the heated air. It will be seen herein-
after that the value of the temperature measured by thethermocouple 20 is used to control the temperature of the
heated air at the outlet of the heater 7 by energizing the
above-mentioned electrical heating coils.
The air heated at 600 is then supplied through
a tube 8 to a catalytic combustion chamber 10. Before
entering the chamber 10, the heated air is mixed with
propane. The mixture is made by introduction of the gas
by means of a gas diffusor 9 inserted into the tube 8.
The catalytic chamber 10 is filled up with an aluminium
and platimiun oxyde catalyst which produces an auto combustion
reaction of the propane mixed in the heated air with the
oxygen of the air at about 600F. The reaction of the
oxygen of the air with propane in the combustion reaction
reduces the concentration of oxygen down to 2 to 3% and
12~9~
raises the temperature of the air to about 1200F. The
inlet and outlet of the catalytic chamber 10, and the
tubes 8 and 13 are provided with connecting flanges 91 that
can be unbolted to remove the catalytic chamber from the
apparatus for maintenance whenever necessary. Advantageously,
the catalytic combustion chamber is dismountable to permit
the replacement of the inner material only instead of the
complete chamber, thereby reducing the maintenance costs.
A thermocouple 92 is provided at the outlet of
the catalytic chamber 10 to measure the temperature of the
air with a reduced oxygen concentration. It will be seen
hereinafter that this measured temperature is used for
controlling the energization of the electrical heating coils
within the inner tube 21 and for opening a solenoid valve
23 shown in figure 2 to supply propane to the diffusor 9.
The air with a reduced oxygen concentration at
1200F obtained at the outlet of the catalytic oombustion
chamber 10 is supplied through a tube 13 to the inner tube
of the heat exchanger 85 wherein it exchanges its heat with
the air pumped by the compressor 3 in the outer shell of
the heat exchanger 85 therebyraising the temperature of
the air within this outer shell to about 3nOF at the out-
put of this outer shell, as indicated hereinabove.
The air having a reduced oxygen concentration is
then supplied through a tube 94 to the bottom of the housing
of a spray water cooler 15 where it is cooled. The air with
a reduced oxygen concentration circulates inside the cooler
15 from bottom to top and is subsequently returned to the
preservation room through a tube 17. The cooler 15 is
provided with a water spray 96 which sprays water onto the
air inside the housing, and with a water drain 22 for evacua-
tion of the water sprayed for cooling the air with a reduced
oxygen concentration before it is returned back to the pre-
servation room. The tube 94 is also provided with connecting
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flanges 91 of the same type as described above for facili-
tating maintenance.
A thermostat 40 is disposed within the tube 17.
As will be seen hereinafter, this thermostat is used for
controling power supply to the apparatus.
Figure 2 of the drawings shows in details the
gas-diffusor 9 mentioned hereinabove. This gas-diffusor is
provided with a solenoid valve 23 controlling the admission
of propane from a propane pressurized bottle. The diffusor
9 is mounted on the tube 8 for mixing the propane with the
heated air from the heater 7. The propane is admitted
through the solenoid valve 23 to a differential gas flow
regulator 24 supplying gas to the diffusor 9 directly through
a conduct 90 or vi~an adjustable gas flow regulator 25. This
gas flow system is used for controling the gas flow from
the propane press~lrized bottle to the diffusor 9.
Figure 3 of the drawings shows the electrical
circuit of the invention. It should be noted that this
electrical circuit incorporates a particular circuit auto-
matically controlling the operation of the apparatus.
The electrical circuit shown on figure 3 is sup-
plied by a 240 volts A.C. source 50 connected to a first
contactor 27 provided with a solenoid coil 27a closing
the contacts of contactor 27 when energized. An automatic
disconnecting switch 28 is also provided to switchoff the
current through the coil 27a, thereby opening the two
contacts of the contactor 27, when opening the door of the
cabinet containing the electrical system for an improved
maintenance safety. A manual disconnecting switch 29
permits to manually close or open the two contacts of con-
tactor 27 by respectively activating or desactiviting the
coil 27a when the door of the cabinet is closed. The coil
27a is connected at one terminal to a lead 26 (passive
lead or negative terminal) of the source 50 and at the other
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terminal to the ground by the intermediary of the two
switches 28 and 29 and the connecting point 61 of a terminal
board. The two contacts of the contactor 27 supply electric
power from the source 50 to the electrical system when closed
(as shown on figure 3).
More particularly, the two contacts of contactor
27, when closed, supply a transformer 37 (220-230/110-115 V)
and contactors 34, 35 and 36.
The two terminals of the secondary of the trans-
former 37 are respectively connected through two fuses 43
(2 amperes fuses for example) to a pair of connectin~ points
64 and 65 of the terminal board 60. The connecting points
of the terminal board 60 will be referred to hereinafter
as poi~nts.
Points 63 and 65 of the terminal board 60 are
each connected to One terminal of a solenoid coil 36a and
supplies with electrical power the control circuit. Point
63 is connected to point 64, which is connected to the
secondary terminal of the transformer 37, through a thermostat
40 and a pressure switch 39. The energization of coi~ 36a
closes the two contact of a air compressor contactor 36
thereby supplying electric power to the air compressor 3.
The thermostat 40 (mounted between points 62 and 63) responsive
to the temperature of the cooled air at the outlet 17 keeps
the circuit supplying the coil 36a and the control circuit
closed at a preset temperature (60F) of the air having a
reduced oxygen concentration after it has been cooled and
before it is supplied to the preservation room. The pressure
switch 39 (mounted between points 62 and 64) is provided
for safety purpose, to switch off and thereby stop supplying the
compressor and control circuit when the pressure at the
outlet of the compressor 3 is lower than a predetermined
value which means that the compressor does not normally work.
A push-button starter 38 is mounted in parallel to the
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pressure switch 39 for by-passing the switch 39 when s-tarting
the compressor 3, until the operational pressure is obtained
(about 15 inches of water) and the pressure switch 39 is
closed for a normal operation.
The -transformer 37 is also connected to point 71
by a wire 74 connecting point 65 to point 71. An other wire
75 connects points 63 and 73 thereby supplying voltage to
point 73.
The control circuit comprises a two points,
temperature switch 30. The thermocouple 92 (shown in
figure 1) has its two terminals respectively connected to
terminals 1 and 2 of the switch 30 thereby supplying the
voltage appearing through the thermocouple 92 to this switch.
The first temperature point or first temperature level
measured by the thermocouple 92 acts on the switch 30 to
energize the solenold 33 through point 71 and terminal 6
of the switch 30. The second temperature point or second
temperature level measured by the thermocouple 92 acts on
the switch 30 to energize the propane solenoid valve 23
(see figure 2) through point 71 and terminal 1~ of switch 30.
The transformer 37 is also connected to terminals
5, 11 and 16 of the switch 30 by point 63 and to terminal
12 by point 65.
Upon activation of the coil 33, the contacts 32a
and 32b of contactor 32 close and respectivel~ connect the
transformer 37 from point 73 to point 68 and from point 71
to point 69. As illustrated on figure 3, terminals 11, 12
and 6 of a one point temperature controller 31 forming part
of the control circuit are respectively supplied by points
68, 69 and 71. The contactor 34 is permanently activated,
when contactor 32 is energized, by the solenoid coil 34a
through point 69, point 70, switch 42 and point 68. The
thermocouple 20 (shown in figure 1) has its two terminals
respectively connected to terminals 1 and 2 of the controller
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~;~1912'7
31. The measured temperature, or voltage appearing through
thermocouple 20, acts on controller 31 to sequentially
activate the solenoid coil 35a through point 68 and terminal
5 of controller 31, thereby closing the contacts of the
contactor 35.
The contactors 34 and 35 respectively supply
electrical power to a permanent heating coil 41b and sequential
heating coil 4la both mounted in the inner tube of the heater
7 of figure 1. The sequential coil is energized only when
supplementary heat is needed to maintain or control the
temperature of the heated air at 600E. A manual disconnect-
ing switch 42 is provided to manually switchoff the coil 34a
of the contactor 34 for stopping supplying power to coil 41b.
The switch 30 may be a Honeywell CB 301 switch and
the controller 31 a Honeywell AB 301 controller (Trademarks).
Figure 4 of the drawings shows in details the
spray water cooler 15. As can be seen, the water is supplied
by a water inlet pipe 44 to a water spray 96 by means of a
water pressure re~ulator 45. The water pressure regulator
45 adjusts the pressure of the water supplied to the water
spray 96 at about 35 psi. This type of cooler advantageously
reduces the consumption of water.
Obviously, the object of the present invention is
not restricted to the above described preferred embodiment.
Some features can be modified, for example replacement of
propane gas with other inflammable gas, substitution of
aluminium and platinium catalist with other types of catalist
material, change in the exact shape or type of the elements
constituting the apparatus, etc... Of course, such modifi-
cations would not change the scope and nature of the presentinvention.
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