Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to electric vehicles such as fork lift trucks
and tow tractors and discloses a temperature regulatlon system for use on such
a vehicle which is intended to be operated in extremely cold environments as
well as extremely warm enviro-nments.
Fork lift trucks have been known for some time. Examples of fork
lift trucks are shown in United States Patent Nos. 3,637,100 and 3~532,238.
While fork lift trucks of the type described in the above-cited patents are
very useful for most applications, special problems arise when such trucks are
to be used in an extremely cold environment, such as a freezer building used to
store frozen food. Fork lift trucks are used to transfer frozen food between
a freezer warehouse and a large freezer road truck. A vehicle operating in
such a freezer warehouse must be able to operate satisfactorily at temperatures
as low as about -30~, while at the same time being able to adapt quickly to
operation in outside temperatures, which may be 90F or higher on hot summer
days.
When a fork lift truck operates in a cold environment, water tends
to condense on the truck (the truck being warmer than its surroundings) and this
condensation causes eventual corrosion or freeze up of the electrical equipment
on the truck. Especially vulnerable are components such as the Silicon
Controlled Rectifier ~SCR~ used in the electrical control system for fork liEt
vehicles of the type shown in the above-cited patents.
Fork lift trucks are sometimes designed such that all, or almost all,
of the electrical components are physically located together, in a so-called
electrical box. In such a case, it is important that the electrical box be
kept dry, to prevent corrosion. But is also important that the temperature oE
the electrical box not become too high, as would tend to happen when the truck
is driven out of the freezer warehouse and into a warm environment.
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It is also necessary to heat other components of the fork lift truck.
~or example, -the accelerator for the vehicle may comprise a set of components
mounted in a box, as shown in ~nited States Patent No. ~,087,776. This
accelerator box needs to be kept dry. Also, the control console of the vehicle
typically contains a set of components, located in one place, and also needs
protection from condensation.
In the past, one solution to the problem of operating an electric
vehicle in an extremely cold environment has been to place electric resistance
heaters at selected locations around the vehicle. The components of, say~ the
electrical box could be kept warm and dry in this manner, at the expense of
electrical energy needed to supply the heat. In addition to requiring large
amounts of energy, resistance heaters will tend to produce too much heat when
the vehicle is driven into a warm enviromnent, since the resistance heat is
added to the heat in the ambient air.
Electric fork lift vehicles are typically driven by DC motors,
which have efficiencies of about 85%, under no load conditions, and about 70%
in a loaded condition. The remaining energy is dissipated as heat. This fact
is particularly ironic in the context of the vehicles for operation in cold
environments, since heat is precisely what is needed at certain key positions
around the truck, to keep components warm and dry.
Accordingly, it is a primary object of the present invention to
provide a temperature regulation system which enables an electrical vehicle to
operate in an environment of extremely cold temperature, and to be able to
alternate between operation in cold and normal environments.
It is a further object of the present invention to provide a tem-
perature regulation system for an electric vehicle in a manner which conserves
energy, by harnessing heat which would otherwise have been wasted
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It is a further object of the present invention to provide a tem-
perature regulation system as described above, wherein the system can be
automatically changed from a closed loop to an open loop system, depending upon
the temperature measured in a particular location on the vehicle.
It is a further object of the present invention to provide a tempera-
ture regulation system as described above, wherein the system tends to prevent
condensation of moisture in critical portions of the vehicle, thereby minimizing
corrosion of important components.
The present invention solves the problem of keeping critical compon-
ents warm and dry while the vehicle is in a cold environment, and does so in a
manner which conserves energy. Furthermore, the invention allows the vehicle
to adjust to the vast difference in ambient conditions between the inside of
a freezer and normal outside temperatures.
The present invention solves the problems described above through
the use of a system of ducts which directs air from the heat-producing motors
in the electric vehicle to various key components around the vehicle. In the
preferred embodiment, heat from the electric traction motor and from the hy-
draulic pump motor is used to heat air in the ducts, which is directed through
the electrical box of the vehicle, as well as through the control console and
the accelerator box. Air is then returned to the traction and/or hydraulic pump
motors for recycling. When the truck operates in an extremely cold environment,
the system of ducts is a closed system. That is, substantially no air from the
outside is allowed to enter the system, and air inside the system does not
escape to the outside.
When the temperature in a given part of the vehicle, such as the
electrical box (the temperature of which should not be allowed to become too
high) attains a predetermined value, several valves are actuated which simul-
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taneously open the system of ducts to the outside air, and block the flow of
air through the ducts from the electrical box to both the control console and
the accelerator. In this manner, outside air is made to pass through the
electrical box, keeping said box from exceeding a saEe temperature.
The system therefore is converted from a closed-loop to an open-loop
system automatically, depending upon the sensed temperature within the elec-
trical box.
Broadly stated, the present invention provides a temperature regula-
tion system, for use in an electric vehicle, operable in both cold and warm
environments~ the vehicle having at least one electric motor and at least one
control component, comprising first duct means for directing air from the
motor ~o the control component, second duct means for returning air Erom the
control component to the motor, means for forcing air through the first and
second duct means, and temperature-responsive means for exposing the control
component to outside air when the temperature of the control component exceeds
a predetermined value.
The invention will now be described in greater detail with reference
to the accompanying drawings, in which:
Figure 1 is an illustration, partly in schematic form, of the tem-
perature regulation system of the present invention, including a cross-sectional
view of the electrical box; and
Figure 2 is a cross-sectional view, taken along the line 202 of
Figure 1.
The present invention is designed particularly for use with an
electric fork lift vehicle, wherein all or most of the electrical components of
the vehicle are mounted in a so-called electrical box, in one compact location
on the vehicle. Also, most of the controls for the vehicle are mounted within
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a control console. In addition, the accelerator for the vehicle may take the
form of an accelerator box. Other groupings of vehicle components may exist
in such a vehicle, and the choice of groupings illustrated in the preferred
embodiment is intended to be illustrative and not limiting.
In Figure 1, the control console is designated generally by refer-
ence numeral 1, the steering wheel being indicated symbolically by reference
numeral 2. The accelerator box is designated by reference numeral 5, and the
electrical box is designated generally by reference numeral 8. The components
within each box are not shown, since a detailed knowledge of the contents of
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each box is not necessary for understanding of the invention.
Locomotion for the electric vehicle is provided by DC motor 10. ~Iy-
draulic lifting capabilities are provided by pump motor 12. Motors 10 and 12
contain fans 80 and 81 positioned within the motors to force air in the direc-
tions indicated by arrows 11.
A pair o~ ducts lS and 16 are connected between motors 10 and 12
respectively, and electric box 8. These ducts terminate in flapper valves 18
and 19, located within chamber 20, which is itself contained within electrical
box 8. The flapper valves close off ducts 15 and 16 except when air is flowing
into the electrical box 8. Air exiting from ducts 15 and 16 passes through
filter 21, as indicated by arrow 22. The purpose of the filter is to remove,
from the air~ carbon particles produced at the brushes ~not shown) oE the DC
motors.
The temperature regulation system is shown in Figure 1 in its closed-
loop state, that is, in the condition suitable for operation within an extremely
cold environment. Under these conditions, air passing through ducts 15 and 16,
and through the electrical box 8, is allowed to pass through valve 25 and into
ducts 27 and 28. Duct 27 carries air to control console 1, while duct 28
carries air to accelerator box 5. After having passed through the control
console and the accelerator box, air flows through ducts 30 and 31, and then
into chamber 32.
Chamber 32 contains a small blower 70 which is positioned to direct
the air through ducts 33 and 34, thereby returning the air to motors 10 and 12,
to be reheated and recycled. The blower 70 also serves to decrease the back
pressure in the ducts. Only one blower in chamber 32 is shown, though more
than one blower could be used.
Attached to chamber 32 is duct 40 which is connected to a valve
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assembly, designated generally b~ reference numeral 42. This valve assembly
comprises a valve plate 43, which is shown in full in its closed position, that
is, preventing outside air from entering the system, and preventing inside air
from leaving the system. Both the valve 25 and valve 43 are operated by sole-
noids, indicated by reference numerals 45 and 46 respectiveLy.
The structure of valve 25 is illustrated in more detail in Figure 2,
which shows another cross sectional view. Valve 25 comprises two portions,
plate 47 and plate 48. Plates 47 and 48 are connected to pivot around pivot
point 75, in a rigid manner ci.e. the plates are fixed with respect to each
other). ~ovement of the plates is effected by piston 4~ via a link 76 which is
pivotally connected to the piston 49 and to plates 47 and 48 at the pivot point
75. Piston 49 is retracted on energization of solenoid 45. Ln the position
shown in Figure 2, plate 47 is seen to cover an opening 50 in the wall 52 of
electrical box 8. When opening 50 is covered by plate 47, plate 48 allows air
to pass into chamber 55, and then into duct 27, as indicated by arrows 56. When
the position of the valve is changed, plate 48 closes chamber 55 to the flow of
air, while plate 47 moves away from opening 50 thereby opening electrical box 8
to the flow of air to the outside through opening 50.
Temperature sensing is accomplished by the use of thermostats 60 and
61, positioned to measure the temperature within electrical box 8. In fact,
thermostats could be located anywhere around the electrical vehicle. I-lowever,
since the electrical box contains the components which are in greatest need
of protection from extremes of temperature, the preferred embodiment shows the
thermostats within the electrical box. In the preferred embodi~ent, thermo-
stats 60 and Sl are connected in parallel, so that one may fail without causing
the system to break down. The electrical connection between thermostats 60 and
61, and solenoids 45 and 46, is not shown in the drawing, but is accomplished in
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any conventional manner.
The operation of the temperature regulation system will now be des-
cribed. When the electric vehicle is located within an extremely cold environ-
ment, the position o~ the valves is as shown in the drawings. That is, valve
plate 43 is positioned to close off chamber 32 from outside air. Also, valvc
25 is disposed as sho~m in -the drawings, permitting air to flow from the
electrical box into ducts 27 and 28, but not to the outside through opening 50.
Thus, the system functions as a closed-loop system, with air being driven by
fans 80 and 81 in the respective motors 10 and 12, around the system, in the
direction of arrows 11.
When the temperature in the electrical box 8 reaches a predetermined
value, generally 120P, thermostats 60 and 61 emit a signal, which causes
solenoids 45 and ~6 to change the positions o:f valves 25 and '12, rlhe position
of valve 25 becomes such, khat plate 48 closes chamber 55 to the passage of air,
and plate -~7 opens electrical box 8 to outside air, via opening 50. Valve ~2
simultaneollsly changes its position such that flapper valve ~3 is in the position
shown in phantom, thereby allowing outside air to enter chamber 32, through duct
40. In this situation, the system functions in its open-loop form.
It is seen, in l~igure 2, that the piston 49 is held in place by a
spring 72. Thus, in the embodiment shown, the solenoid 45 would be energized
in the closed-loop mode and de-energized in the open-loop mode. However, the
invention clearly includes an embodiment llherein the solenoid is de-energized
in the closed-loop mode and vice versa. The important thing is that the valves
change position upon signal from the thermostat. The state of energization of
the solenoid is not important, as long as tlle desired valves are opened and
closed at the desired times.
In the open-loop operation, air from the outside enters chamber 32,
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and is directed through motors 10 and 12, and into electrical box 8, whereupon
the air exits through opening 50 in the electrical box. During this time, air
does not circulate through the other ducts in the system, i.e. the ducts
connected to control console 1 and accelerator box 5, because ducts 27 and 28
have been closed off by valve 25.
When operating in the open-loop system, outside air is therefore
made to cool motors 10 and 12 as well as electrical box 8. Even if the electric
vehicle is operating in an extremely warm environment the temperature differen-
tial between ambient air and the components will provide component cooling.
Air from the outside does not cool the control console 1 and accelerator box 5.
The components in the console 1 and accelerator 5 are of the type which c~m
withstand hlgher operating temperatures than would be tolerated by the components
of the electrical box 8. Of course, were there heat-sensitive elements in the
control console and/or accelerator box ~or elsewhere), the duct and valve system
could be modified to mainta:in air flow to the components in need of cooling,
within the teachings of this invention.
In order to increase the efficiency of cooling of the electrical box,
it is possible to place an additional fan (not shown) within the electrical box
to facilitate the flow of air into the electrical box 8 and out of sa:id box
through opening 50.
It is seen that heat generated from the traction and pump motors 10
and 12 is made to serve a useful purpose, i.e., the heating of the critical com-
ponents of the vehicle, thereby preventing condensation in extremely cold
environments. ~urthermore, the oil line 82, which serves the power steering
system of the vehicle, can be routed through chamber 32, and can therefore be
heated by the hot air which passes through the chamber on its return trip to the
motors 10 and 12. There is thus no need for an immersion heater in the oil tank.
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It is understood that -the above described embodiment is only one
of many variations possible within the spirit of the present invention. As
stated earlier? the precise location of specific components around the vehicle
can be varied in many ways, and additional ducts can be constructed to direct
warm air to such locations. The location and number of thermostats can be
varied as well. The location of fans, to assist in directing air along the
desired path, can be varied in known configurations. It is therefore under-
stood that the present invention is not to be deemed limited by the precise
embodiment descrlbed herein. Other embodiments are intended to be covered within
the scope and spirit of the following claims.
