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Патент USA US3093468

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June 11, 1963
Filed. June 20. 1961
2 Sheets-Sheet 1.
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June 11, 1963
Filed. June 20. 1961
2 Sheets-Sheet 2
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United States Patent 0 " 1C6
Patented June 11, 1963
prising a closed cabinet, a conducting grill supported by
Henry W. Dietert, Kerrville, Tex” assignor to Harry W.
Dietert Co., Detroit, Micln, a corporation of Michigan
Filed June 20, 1961, Ser. No. 118,399
1 Claim.
(Cl. 34--1)
insulating means within the cabinet for receiving a sam
ple of granular material supported by ?lter paper, glass
or the like, a grounded electrode positioned on the op
U! posite side of granular material from the conducting grill
within the cabinet, means for generating a high frequency
electric ?eld between the grill and grounded electrode,
means for heating air to a temperature above the boiling
The invention relates to moisture tellers and refers
point of moisture within the granular material and blow
more speci?cally to a method of and apparatus for dry
ing granular material including electronic means for va 10 ing the air through the grill and cabinet.
Another object is to provide drying apparatus as set
porizing the moisture in the granular material.
forth above including a wave guide for directing a high
This application is a continuation in part of United
frequency electric ?eld between a micro-wave generator
States patent applications Serial No. 273,270, ?led Feb
and a grounded electrode through the granular material.
ruary 25, 1952, and Serial No. 60,147, ?led October 3,
Another object is to provide drying apparatus including
a pair of electrodes, means for creating a high frequency
In the past drying apparatus for removing moisture
electric ?eld between the electrodes, means for blowing
from granular material, such as foundry sand, in de
heated air over the electrodes, a balance, means support
termining the percentage of moisture therein have been
ing a sample quantity of granular material from which
relatively slow in evaporating the moisture. Further,
with prior drying apparatus the heat necessary to evap 20 moisture is ‘to be removed within the high frequency elec
tric ?eld from one end of the balance.
orate the moisture has unnecessarily elevated the tem
Another object is to provide a method of and appara
perature of the drying apparatus. Additionally in the
tus for drying granular material which is simple, econom
past it has often happened that moisture evaporated from
ical and ef?cient.
the specimen being dried has condensed on the surfaces
of the drying apparatus impeding the drying ability there 25 Other objects and features of the invention will become
apparent as the description proceeds, especially when
Attempts have previously been made to provide drying
taken in conjunction with the accompanying drawings, il
lustrating a preferred embodiment of the invention, where
apparatus which alleviate these problems. For exam
ple, it has in the past been the practice to blow heated 30 in:
FIGURE 1 is a diagrammatic representation of dry
air through the drying apparatus to remove the evaporated
ing apparatus constructed in accordance with the inven
moisture therefrom to prevent condensation thereof on
the drying apparatus. Also, infrared radiators have been
FIGURE 2 is a modi?cation of the drying apparatus
used as heating elements to more rapidly heat the speci
mens to cut down the time required to make a moisture 35 illustrated in FIGURE 1.
FIGURE 3 is another modi?cation of the drying ap
paratus illustrated in FIGURE 1 wherein the means sup
Such prior art drying apparatus have however not been
porting the sample of granular material within the high
entirely satisfactory in that the time required to remove
frequency electric ?eld is a balance for providing a direct
the moisture from a specimen cannot be su?iciently re
duced thereby and the temperatures created thereby over 40 indication of the moisture content of a sample of gran
ular material.
the necessary periods of use are objectionable in that
With particular reference to the ?gures of the drawings,
they present a danger to operators and unnecessarily ele
one embodiment of the present invention will now be
vate the temperature adjacent the drying apparatus. Fur
ther blowing of air through the drying apparatus at a
temperature below the boiling point of the evaporated 45 As shown in FIGURE 1 the drying apparatus 10 of the
invention comprises a cabinet 12 including a support 14
moisture has been ineffective to prevent objectionable
therein for a sample 16 of granular material such as
condensation of the moisture on the drying apparatus.
foundry sand which is to be dried. The high frequency
It is therefore one of the objects of the present inven
oscillator 18 and means 20 for transmitting the high fre
tion to provide means for more rapid drying of a speci
quency signal generated thereby through the sample 16
men of granular material than has previously been pos
of granular material is also a part of the drying apparatus
10. Heating means ‘21 including blower 22 and heater
Another object is to provide drying apparatus includ
24 is provided to blow air through the cabinet 12 which
ing high frequency electronic means for evaporating mois
is heated to a temperature above the boiling point of the
Another object is to provide a method of drying gran 55 moisture to be removed from the granular material 16.
More speci?cally the cabinet 12 includes the base 26
ular material including electronically evaporating mois
ture from the material to be dried.
Another object is to provide a method of drying gran
ular material including heating air to a temperature above
the boiling temperature of the moisture to be evaporated
and the vertical walls 28 secured to the base 26 by con
venient means (not shown). A cover 30 is hinged to the
vertical walls 28 by hinge 32, as illustrated in FIGURE 1
to permit entry into cabinet 12.
Support 14 includes a hollow support 34 constructed of
insulating material such as a ceramic positioned Within
the cabinet 12 and holds the grill 36 at one end thereof.
Grill 36 is of conducting material such as, for example,
from the granular material and blowing the air through
the apparatus in which the granular material is being
Another object is to provide drying apparatus includ 65 perforated aluminum. The grill 36 serves as a support
ing means for developing a high frequency electric ?eld,
for a sample carrier 38 which is preferably of ?lter paper
means for supporting a sample of foundry sand within
the electric ?eld and means for blowing air heated to a
temperature above the boiling temperature of the moisture
or may be glass, plastic or the like.
The base 26 of the cabinet 12 is provided with an open
ing 40 therethrough in which the insulating support 42
to be removed from the foundry sand through the drying 70 for the transmission means 20 is secured.
Another object is to provide drying apparatus com
Wall 28 of the cabinet 12 and the support 34 are pro
vided with aligned openings 44 and ‘46 respectively there
in through which the conduit 48 extends. Conduit 48 is
part of the heating means 21 which, as previously indi
cated, also includes the blower 22 and heater 24. In
operation the blower 22 which may be energized from an
electric source (not shown) through conductors 50 is effec
tive to blow air over the heater 24 which also may be
energized from a source of electric energy (not shown)
through conductors 52.
The heater 24 is then effective to heat the air to a
temperature slightly above the boiling point of the mois
ture contained in the sample 16 of granular material posi
tioned over the grill 36. The air thus passed through
cabinet 12 which may be exhausted therefrom by normal
leakage from the cabinet 12 or through an exhaust port
54 is caused to evacuate the evaporated moisture from
the cabinet 12 and thereby prevent condensation of the
moisture therein.
The electronic means for producing the electric ?eld
in which the sample 16 of granular material is positioned
directed toward the grounded grill 66 in cabinet 60 through
a wave guide 83 including baf?es 90 extending transverse
ly thereof for directing the electric wave therethrough.
Operation of the modi?ed drying apparatus 58 is the same
as the operation of the drying apparatus 10.
The modi?cation 92 of the drying ‘apparatus 10 illus
trated in FIGURE 3 provides an automatic indication
of the moisture content of a sample of granular material
94 as it is dried. The drying apparatus 92 includes the
10 means 96 for producing a high frequency electric ?eld
in which the sample 94- of granular material is posi
tioned. Means 98 and 100 are also provided in the modi
?ed drying apparatus 92 to blow hot air over the elec
trodes 102 and 104 of the means 96 for producing the
‘high frequency electric ?eld. The drying apparatus 92
also includes the balance 105 operable to provide an in
dication of the moisture content of the granular material
sample 94 as it is being dried.
The means 96 for producing the high frequency elec
includes the micro-wave generator 18 which may be of
any known type operable to produce an electric signal
having a frequency of between 1700 kilocycles and 2500
tric ?eld includes a micro-wave generator 106 energized
specimen of granular material 16 positioned therebetween
is produced.
electrodes without heating appreciably any conducting
material of the drying apparatus.
through electrical conductors 168 from a source of elec
trical energy (not shown), leans 110 for transmitting
megacycles. One particular frequency which has been
a high frequency electric signal from the micro-wave
successful is, for example, 15 megacycles.
generator 106 to the electrode 104, and grounded elec
The means 20 for transferring an electric signal from 25 trode 102 and electrode 104 between which the sample
the oscillator 18 to the conducting grill 36 is held in
94 of granular material to be dried is positioned. In
position by means of insulating material 42. The ground
operation the micro-wave generator is energized to pro
ed electrode 56 on the opposite side of the sample 16
duce an electric signal which is transferred to the elec
of granular material to be dried from grill 36 forms the
trode 104 to create a high frequency electric ?eld between
other electrode between which the high frequency electric 30 the electrodes 104 and 10?- causing vaporization of the
signal which functions to evaporate moisture from the
moisture in the granular material positioned ‘between the
Thus in over-all operation a sample of granular ma
Each of the heating means 98 and 100 comprises a
terial having moisture therein which it is desired to re 35 blower 112, a heater 114 energized through electrical
move therefrom is positioned on a container 38, such as
conductors 116 from a source of electrical energy (not
?lter paper, and is placed in the cabinet 12 on the grill
shown), and a conduit 118. Thus in operation with the
36. Blower 22 and heater 24 are then turned on so that
heaters 114 and the blowers 112 energized air heated
air heated to a temperature slightly above the boiling
to a temperature above the boiling point of the mois
point of the moisture in the granular material is passed
ture in the granular material in the sample 94 is di
through conduit 48 into support 34 through grill 36 around
rected against both of the electrodes 104 and 102 .to pre
the sample of granular material 16 thereon into cabinet
The micro-wave generator or oscillator 18 is then
vent condensation of moisture from the sample of granu
lar material 94 thereon and to remove the moisture from
energized to produce a high frequency electric ?eld be
the drying apparatus.
tween grill 36 and electrode 56 whereby due to dielectric 45
Balance 105 comprises a balance beam 120‘ pivotally
heating the moisture in the granular material is vaporized.
mounted at 122 and having the pivot support 124 at
The vaporized moisture is not however allowed to con
end 126 thereof for the hook member 128. Hook
dense on the drying apparatus 10 since the heated air is
member 128 is secured to a ‘balance tray 1330 for sup
at a temperature above the boiling point of the moisture
porting the sample 94 of granular material to be dried.
and therefore carries the moisture still in a vaporized state 50 An elongated support member 132 is secured to the other
out of the cabinet 1'2. Further since the high frequency
end of the balance beam 120 along which a second hook
electric ?eld does not function to cause dielectric heating
member 134 having a pivot point 136 thereon may be
in conductor materials to any appreciable extent the
cabinet, grill and electrode may be maintained at a rela
variably positioned. Hook member 134 supports a sec
tively low temperature.
Extremely rapid drying of granular material is thus
accomplished. For example, it is possible with a 15
megacycle electric signal to dry a ?fty gram sample of
placed on the tray 130 and is ‘balanced by a weight on
[tray 138. The hook member 134 is positioned to bal
granular material in approximately thirty seconds.
The modi?cation 58 of the drying apparatus 10 illus
trated in FIGURE 2 includes the cabinet 60 having a
sample compartment '62 and a heated air duct 64 sepa
rated by a perforated grill 66 of conductive material. A
sample of granular material 68 in a container 70 of ?lter
paper, glass or similar material may be positioned in the
sample compartment 62 through the door 72. Heating
means 74 including blower 76, heater 78 and conduit 64
are provided as before to blow hot air through grill 66
to carry away the moisture vaporized from the granular
material sample.
In the modi?ed drying apparatus 53 the high frequency
electric ?eld is produced by a micro-wave generator 32
which is energized from a power supply 84 and cooled by
means of a cooling blower 86 also energized from power
supply 84.
ond ‘balance tray 138 thereon for receiving a balancing
Thus in operation a sample of granular material is
ance the beam 120 about the pivot 122. During drying
of the sample of granular material 94 in the manner
indicated the weight of the sample 94 on the balance
tray 130 will decrease to cause pivoting of the balance
beam 120. The pivoting of the balance beam 120 will
be related to the amount of moisture in the sample of
granular material 94 whereby an indication of the mois
ture content thereof vwill be provided.
The drawings and the foregoing speci?cation constitute
a description of the improved moisture teller in such
full, clear, concise and exact terms as to enable any per
70 son skilled in the art to practice the invention, the scope
of which is indicated by the appended claim.
What I claim as my invention is:
Drying apparatus for removing moisture from a speci
men of granular material such as foundry sand, com
The high ‘frequency electric signal is then 75 prising an outer container including a bottom having an
opening therein olfset with respect to ‘the center of the
outer container into the inner container through the perfo
container which bottom is secured to and closes one end
of the outer container, at top at the other end of the
outer container for closing said other end, an air intake
rated member, around the electrodes and out of the ex
haust opening in the outer container, and a heater posi
tioned in said blower operable to heat the blower air
to a temperature above the boiling point of moisture to
be removed from a sample of granular material posi
and an air exhaust opening extending transversely through
opposite sides of said outer container adjacent the bot
tom of the .outer container with the air intake opening
substantially closer to the opening in the bottom of the
tioned on the perforated member for maintaining the
electrodes at a temperature above the boiling point of
the moisture to prevent condensation of moisture on the
container than the air exhaust opening, an inner Icon
tainer of insulating material having an open lower end 10 electrodes.
positioned within the ?rst container and resting on the
References Cited in the ?le of this patent
bottom thereof, said inner container extending parallel
to said outer container [and having its center offset with
respect to the center of said outer container and posi
rtioned substantially over the opening in the bottom of 15
the ?rst container, a perforated ‘conducting member se
cured over the other end of the inner container for
supporting a sample of granular material, a grounded
electrode supported in the outer container in a location
over the perforated member, a ‘second electrode insulated 20
from and extending through the opening in the bottom of
said outer container to the perforated member for di
recting a ?eld of high frequency electric energy between
‘the perforated member and grounded electrode, means
Brown _______________ _._ Oct. 7, 1947
Dippel ______________ ..._ Mar. 11, 1952
Hagopian ____________ __ Aug. 25, 1953
Calosi ______________ __ Apr. 27,
Cannon ______________ __ Jan. 4,
Millett ______________ __ Apr. 30,
Rudd _______________ __ Dec. 23,
Phillips _____________ __ Dec. 5,
Virginia Polytechnic Institute Bulletin, Eng. Experi
including an oscillator connected to the second electrode 25 ment Station Series No. 42, “Drying Ceramic Products,
by use of Induced High ‘Frequency Electrical Energy,”
by T. C. Vaughan, H. E. Revereomb, W. -A. Murray and
J. W. Whitmore, .1939, pp. 1—20.
conduit extending through the air intake opening in the
Industrial and Engineering Chemistry, vol. 41, 1949,
outer container and emptying into the inner container
for passing air through the air intake opening in the 30 No. 8, pp. 16864694.
for producing and passing through said second electrode
a high frequency electric signal, a blower including a
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