METHODE ET DISPOSITIF POUR EMPECHER OU RALENTIR LES EFFETS DU GEL SUR LES FRUITS ET LEGUMES

METHODS AND APPARATUS FOR PREVENTING OR RETARDING FRUIT AND VEGETABLE FREEZING

Abrégé anglais

ABSTRACT
Apparatus is provided for protecting crops from frost
damage in the form of a vertical tower fixed to the earth
against gyration, a rotor on top with two airfoil blades
extending upward at a conical angle and drive means drivingly
connected to the rotor through a vertical shaft, said tower
projecting substantially above the level of the trees to be
protected and sufficient to pick up air in the inversion layer
and deliver it to the ground in a generally cylindrical mass to
spread out radially without substantial disturbance of the soil.

Revendications

The embodiment of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. An apparatus for protecting crops, particularly
tree or orchard crops, from frost damage comprising a vertical
tower fixed to earth against gyration, a vertical shaft
extending lengthwise through said tower, a rotor on the top end
of said shaft above the tower, said rotor including a blade
retaining member bent upward to form a conical angle, at least
two blades of airfoil section, means connecting said blades to
said blade retaining member at a pitch angle satisfying the
rotors aerodynamic requirements and drive means drivingly
connected to the drive shaft at the bottom of the tower, said
tower projecting substantially above the level of the trees of
the crop to be protected at a height sufficient for the rotor
to pick up air in the inversion layer and deliver it to the
ground to spread out radially along the earth generally beneath
the foliage of the tree crop and then upwardly through and
between the tree foliage and wherein the rotor blades are
spaced above the ground a distance sufficient to pick up air in
the inversion layer but within the ground effect of zone of the
rotor.
2. An apparatus as claimed in claim 1 wherein the
blades are made with a standard N.A.C.A. airfoil section.
3. An apparatus as claimed in claim 1 or 2 wherein
the vertical shaft is driven by a horizontal shaft through a
pair of bevel gears.
4. An apparatus as claimed in claim 3 wherein the
horizontal shaft is driven by a power take off from a tractor.

5. An apparatus as claimed in claim 1 or 2 wherein
the tower projects one rotor diameter or less above the ground.
6. An apparatus as claimed in claim 3 wherein the
tower projects one rotor diameter or less above the ground.
7. An apparatus as claimed in claim 4 wherein the
tower projects one rotor diameter or less above the ground.

Description

l~f.~
The damaging freeæes which occur in the fruit and
vegetable industries are a well known occurrence. rrh~se freezes
are generally known to be due primarily to the formation oE
atmospheric inversions over a ~airly wide area. This condition
normally occurs on clear, calm, cold nights and is chara¢terized
~y an atmosphere in which air temperature increases with
altitude. Unfortunately, an inversion is an inherently stable
condition which -tends to persist until wind velocities increase
or until daybreak, at which time incoming solar radiation begins
to warm the earth and trees.
The freezing of foliage and of the crop is purely a
radiation phenomena, brought on by the inversion, in which the
soil, foilage and fruit all radiate heat to space. The result
is that the atmosphere cools from the ground upward. As a
result, it is not uncommon to find temperature differentials of
10 or more between the ground and 60 foot levels above the
ground.
The existance of this warm air mass at higher
elevations represents a very large potential energy source which
can be used to oEfset a grove's net radiation heat loss.
TherP have been many m~thods and apparatus proposed in
an effort to solve this freeze problem. Perhaps, the best known
and most time honored is the use of "smudge pots" scattered
throughout the area to be protected. While these are somewhat
effect ve, they fall far short of belng the real answer to the
problem. It has also been proposed to use wind machines to
create a sur~ace wind simulating that which, when it naturally
occurs, reduces the freeze damage. Such machines are
illustrated in Towt U.S. patent 2,481,702; Potter U.S. patent
2,836,932; Beckett U.S. patent 2,895,259; Grabowski U.S~ patent

3,180,570; Coles U.S. patent 3,288,353; and Vertrees et al. U.~.
patent 3,306,533. The difficulty with such machines is that
they were useful only on very calm nights and were at best very
inefficient because they simply mixed the cold air next to the
ground with somewhat warmer air at a limited height above the
ground so that the effective raising of the temperature of the
operative air mass at plant level was very low. In order to
overcome this problem some attempts were made to draw air down
from a higher level through a vertical duct and distribute it
horizontally along the ground as in Graham U.S. patent
2,807,120. Unfortunately, such machines were not strong enough
or effective enough to accomplish the result sought. Another
approach is that shown in Davies U.S. patent 3,003,282 which
attempted to combine the approach of drawing higher level air
down through a duct with the smudge pot approach by heating it
at ground level and then blowing it horizontally across the
surface. Such an approach is expensive and difficult to use.
The present invention is based upon the concept of
transporting large volumes of air from the higher warm air
levels down to the grove floor and spreading i~ radially
outwardly under the tree or foliage canopies. ThiS air spreads
out radially and, being warmer air and therefore less dense,
tends to ascend through and between the ~rees, transferring its
heat to the fruit and ~oliage. This is a totally new concept in
dealing with the freeze problem.
I provide an apparatus and method for protecting
crops, particularly tree crops, against ~reezing which provides
a rotor having a hub and at least two blades, each of an air-
foil section, a blade retaining plate or plates connecting said
blades and hub, said blade or retaining pla~es being bent upward

lZ'~
to form a rotor coning angle to satisEy the rotor's aerodynamic
requirements, a vertical tower fixed to the earth to inhibit
gyration, a vertical drive shaft journaled in the tower,
connecting means between said rotor and drive shaft at the top
of the tower, drive means drivingly connected to the drive shaft
at the bottom of the tower, said tower extending substantially
above the level of trees to be protected, a distance sufficient
to piclc up air in the inversion layer and deliver it to the
ground in a generally cylindrical mass until it reaches the
ground and moves radially along the ground but not so close as
to disturb the soil surface and create dust. This distance is
generally less than two rotor diameters and preferably one rotor
diameter or less above ground level. Preferably, the rotor
blades are made with a standard N.A.C.A. airfoil section.
Preferably, the warm air from approximately one rotor diameter
above the rotor is drawn downwardly through said rotor at a
level one rotor diameter or less above the ground level in a
~; substantially steady sta~e flow having a large number of
retrograde vortices, spreads out radially along the ground level
and then rising by convention and fluid friction vertically from
ground level.
:~
In the foregoing general description of -the invention,
I have set out certain objects,~purposes and advantages. Other~
; objects, purposes and advantages of the invention will be
apparent rom a consideration of the followiny description and
the acccmpanying drawings in which:
Figure 1 is a side elevational view of an apparatus
according to this invention installed in an orchard grove;
Figure 2 is a top plan view of a blade retaining plate
of Figure l;
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f.~2~fæ
Figure 3 is a section on the line III-III of the
retaining plate of Figure 2; and
Figure 4 is a fragmentary section of the tower and
gear box of Figure 1.
Referring to the drawings, I have illustrated a tower
10 mounted on a gear box 11 fixed to a concrete pad 12 in a
orchard. A vertical drive shaft 13 extends upwardly through the
tower and is journaled at the top of the tower in bearings 14
and at the bottom of the tower in bearings 15. Blade retaining
plates 16 are fixed to a carrier ring 17 on the top end of drive
shaft 13. The blade retaining plates have a generally flat
central portion 18a and blade carriers 18 extending therefrom
; with positive dihedral which carry airfoil blades 19. The lower
end of the drive shaft 13 carries a bevel drive gear 20 which
engages a bevel gear 21 at right angles thereto. Gear 21 i5
mounted on one end of a horizontal power shaft 22 which shaft
extends out of housing 11 through bearings 23, 24. The other
end of shaft 22 is connected to a drive means 25,~ such as an
engine directly connected to the gear box or a tractor power
take off, through a drive shaft 26 and V joint 27.
This air is carried downwar~ly and swept along the
surface of the ground radially beneath the trees as shown in
Figure 1. Such an apparatus when combined with the waste hea~t
from the drive engine has a capacity for providing a reasonable
~; degree of frost protection over a wide area with temperature
differentials.
In the foregoing specification, I have set out certain
~; preerred practices and embodiments of this învention, however t
it will be understood that this invention may be otherwise
embodied within the scope o the followins claims.
4.