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Патент USA US2112731

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March 29, 1938.
7
I
H. BRUNING E'II' AL
2,112,731
DRYING BOX AND INCUBATOR
Original Filed Sept, 28, 1955
2 Sheets-Sheet 1
March 29, 1938.
H. BRUNING ET AL
2,112,731 *
DRYING BOX AND INCUBATOR
Original Filed Sept. 28, 1935
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2 Sheets-Sheet 2
2,112,731
Patented Mar. 29, 1938v
UNITED STATES
PATENT OFFICE
2,112,731
DRYING BOX AND INCUBATOB
Hans Briining and Otto Schiiller,‘ Hanan, Ger
many, assignors to the firm of W. C. Heraens.
G. m. b. 11., Hanan, Germany
Serial No. 42,032.
Application September 28, 1935, In
Germany May
Renewed November 8, 1937.
18, 1934
9 Claims. »(Cl. $19-35)
2 and 3 respectively both of‘ which are closed by
The present invention relates to drying boxes a bottom 4 and 5 respectively, preferably form
and incubators which are automatically regu
ing part of the corresponding wall. The inner
lated to maintain, with extreme exactness, any cylindrical member 2 consists of sheet metal of
adjustable heat degrees at uniform heat distri
high coe?icient of thermal expansion, surrounds
bution, and particularly refers to the shape and the useful space i of the apparatus and carries
the regulating devices of such apparatus.
' a series of mica heating units ‘I. The wall 2 is
Laboratory-drying boxes and incubators gen- 1‘ insulated against the outer wall I by vitreous
erally used hitherto have the form of a four-sided insulating material 8 or the like. A door I
prism and_as a rule are protected by asbestos hinged at Ill and insulated also by vitreous insu- 10
10 sheets against heat losses‘.
dating material II or the'like serves to close the
As with devices of a cylindrical form the ratio
between outer surface and volume is smaller than
with a prismatic form, the heat losses for equal
volumes are smaller. The insulation may easily
15 be effected by vitreous insulating material or the
apparatus. A frame l2, fitting the useful space
i, may easily be withdrawn and serves to carry
plates it upon which material ‘or the likev to be.
treated may be arranged. In the lowest portion 15
of the walls 2 and‘; an opening is provided and
like, having better heat insulating properties than these openings are connected by a tube It through
asbestos sheets, because the cylindrical inner and which liquid may be drained off in case a vessel
outer walls of the apparatus are self-supporting. ; breaks inside the apparatus. The tube i4 simul
Whereas with boxes of prismatic form uniform taneously serves to introduce air into the space t. 20
distribution of temperatures offers serious dif
20 ?culties, as the heating wires must be stretched Diametrically opposite the tube It a similar tube
II is provided also extending from the useful
upon. tubes .or frames arranged at the bottom, ' space 0 to the outside, where it opens into a
with a cylindrical form uniform heating of the ‘ socket l6 adapted to receive a thermometer II
space may easily be obtained by arranging, in a which extends into the useful space 6 andserves
suitable manner, the heating wires in the form of to indicate the temperature within the apparatus.
25
small mica heating units around the cylindrical
space. By arranging the heating elements near
the door and at the lower half of theapparatus
closer together than at other places and by using
aluminium- or copper-sheet as material for the
30 inner wall, uniformity of temperature of :1‘ C.
may easily be obtained within the whole space.
The shelves or insertion plates are carried by a
frame which may be removed by a simple opera
35 tion, so that the inner wall of the box‘ and all
inner. parts ‘may easily be cleaned.
'
In the accompanying drawings, a construction
according to the invention is ‘shown by way of
example.
\
Fig.1 shows a front elevation of a drying box
according to the invention, partly in cross sec
tion and partly broken away.
.
Fig.‘ _ 2 shows a central longitudinal section
through the device illustrated in Fig. 1,
45
‘ Fig. 2a is a detail view,
'
Fig. 3 is a section on line 3-4 of Fig. 2,
Figs: 4 and 5 are diagrammatic cross sectional
views showing two modified forms of construction of the invention,
> ‘
Figs. 6 and 7 are diagrammatic illustrations of’
50
curves illustrating the action of the invention
with respect to regulation. '
as
In the cylindrical portion of the socket it open
ings. II are provided through‘which damp air
may escape to the atmosphere.
.
_In drying boxes used hitherto the regulation 30
of the temperature is effected by an inwardly
projecting and exposed thermostat responsive to
the temperature within the useful space and con
trolling a relay. In such regulating arrangements
the heat is transferred from the heating elements 35
to the-wall of the useful space,_frorn said wall
to the air in the useful space and from the air
to-the feeler.
-.
,
,
According to the invention, however, in cylin-.
drlcal drying boxes the thermal expansion of the 40
sheet metal member, surrounding the useful space,
with regard to a rod of low coefficient of thermal
expansionis used to regulate the temperature.
As with the novel arrangement the wall of the
useful space itself serves as regulating member, 45
i.v e., the path of heat transfer is considerably
shortened, an extremely frequent action of the
regulating device and thereby a temperature regu
lation of considerably higher precision results.
It is well known already to regulate electrical 50
ly heated tube, stoves and heating plates by using
the expansion of a portion of the wall, however,
‘
‘
it is not known hitherto to use the thermal ex
The drying box or incubator shown in Figs. 1-8 , pansion of a portion of a wall with regard to a
rests upon a foot or support I and comprises an
55. inner and an outer cylindrical wall of sheet metal
rod-shaped body, arranged outside the useful as
2
2,112,7a1'
space of drying boxes and incubators, to eifect
regulation of such devices, probably because in
exactnesses were expected on account of bulgings
of the thin walls and particularly on account of
the fact, that no favored expansion'of these walls
occurs in any direction. Strong prejudices were
to be cast off to use the known principle also in
connection with drying boxes and incubators, be
cause an exact or precise regulation was not to
10
be foreseen.
' , proved,'that by
Thorough tests, however, have
using the known regulating prin
of low coe?lcient of thermal expansion preferably
is ?xed at 24 to‘ the strip 29 itself. The free ends
of the auxiliary heating coils 2| and 22 are, by
wires 25 and 26 respectively ‘connected - to the
heating elements 'I' which in turn‘are connected
by wires 21 and 29 to contacts 29 and 39 ‘(Figs
2 and 2a), forming part of a heating circuit sup
plied with current by any suitable source of ‘pow
or not shown in the drawings. . Other parts of the
heating circuit, as switches, relays, control lamps
and so on, are also not shown in the drawings,
ciple in connection with drying boxes and incu
as they do not form part of the invention. ' The
bators of a cylindrical shape, a considerably bet
ter and more precise regulation is obtained than . contacts 29 and 39 are carried by arms 3| and 32
respectively. The arm 32 may, by means of a
15 has been possible hitherto with‘the use of im
mersed feelers. A further important advantage of ‘spindle 93 provided with a knob 34, be adjusted
the novel regulating device consists in this, that with regard to the arm 3|, thus pressing the con
troubles are avoided which are caused by the tacts 29 and 30 more or less ?rmly together, de
action of corrosive gases upon the-feeler or by pending on the temperature desired to be obtained
within the space 6.‘ The other .arm 9|, carrying
20 bendings, of the latter. The regulating device
according to the novel arrangement is perfectly the contact 29, is swingably arranged and con 20
protected and lies entirely outside the useful nected to the free end ‘of the rod l9.
When the drying box or incubator is heated,
space of the box or incubator. By omittingthe
usual feeler within the apparatus simultaneously the rear wall or bottom 4 expands, whereas the
rod l9 retains about its original length. At a
the available space may be better utilized. '
If, in cases in which a portion of the wall'not . certain temperature, the freeend of the rod l9
directly heated is used for the regulation, the disengages the contact 29 from the counter
regulation of the temperature is to be ‘further contact 39, whereby the heating‘ circuit is opened.
improved, the portion of the wall in questionmay .Upon the now following cooling of the box, the
bottom 4 contracts and the end of the rod I9
be provided with an auxiliary heating coil, op
erating in accordance/with the main heating coil. allows the-contact 9 to again approach its coun 30
ter-contact 30, until he contacts 29, 39 and there
The improvement is based upon the idea to ef
fect an earlier response of the regulating device by the héating circuit are closed again.
Fig. 4 diagrammatically shows another con
than would be the case with heat transfer by
struction of the regulating arrangement. In
35 heat conduction through the cover of the useful
this
case also the wall 2 of-the useful space 9 of
space and by air convection within the useful
drying box consists of a metal of high coef 35
space. As has beenshown by tests, during the the
?cient of thermal expansion and is surrounded
switching off period in which the auxiliary heat
by
a series of heating'elements 1. Parallel to the
ing coil also is rendered currentless, complete
40 compensation results between the temperature of longitudinal axis of‘ the apparatus and-between
the useful space and that of the wall, so that the cylindrical walls 2 and 3 a rod I 9 is arranged 40
which-again consists of material of low coe?icient
switching on of the current again is always'ef
fected at the same temperature. By shortening of thermal expansion. One end 39 of they rod
the heating period, the effect is obtained, that is is connected to the cylindrical wall 2 sur
45 the regulator still more frequently operates than rounding the useful space 6. The free-end of
otherwise and therefore the regulating curve of the rod l9 extends through a hole in the arm II 45
which is swingably arranged and'carries the con
the device is further improv .
v
'
The heating period may, by suitably propor tact 29 connected to the heating circuit. The
tioning the heating. e?ect of the auxiliary heat countercontact 99 cooperating with the contact
29, is carried by the arm 92 which, by means of the
spindle 99 with knob 34, may be brought in
shortening is not allowed to be carried on so far,
1. e. the temperature of the regulator is not al predetermined positions, corresponding to the
temperatures which are desired within the
lowed to so strongly lead thetemperature of the ' space
9.
'
box or incubator, that the amount of heat, sup
The operation of this device is the same as de
55 plied during the heating period to the box or in
scribed with reference to the apparatus shown '
cubator, is, not su?lcient to compensate for the ‘in
Figs. 1-3.
.
‘
'
’
55
idle losses at the adjusted temperature. It has
According
to
a
further
modi?catiomia
tube
been found, that the upper limit for the heating like feeler “provided with an auxiliary heating
eifect of the auxiliary heating lies at about 15% coil
"may, without connection
A with the ‘wall 2 '
of the capacity of the supply
_
If an auxiliary heating is to be provided on surrounding the useful space '6, be'immersed into
Particularly thin walls of sheet metal such as a - the interior of the box or incubator and be used
for the ?ne regulation. The coil 98 is well iso
paper thin'wall, lsuch walls are preferably re
ing, be shortened as desired. Of course, this
inforced by a ?at or pro?led strip of the wall
metal and the auxiliary heating'coil is then ar
ranged upon this strip._ Preferably the strip si
.
multaneously
serves in such cases as expansion
element for operating the regulating contact.
70
may best be seen from Fig. 3, a U-shaped
strip 29
of sheet metal, serving as‘ reinforcement,
is riveted or soldered to the bottom 4 _of_
paratus which is not directly heated. In ‘this
' >U-shaped strip 29 auxiliary heating coils 2| and
connected to each other by a wire 29 and sur
75 rounding the rod_|9, are arranged. The rod l9
‘lated from the tube 35 and the rod II which it
surrounds. The ends of therod l9 are fixedi'o
the closed end 31 of the tube ll and tothe arm,“
9| respectively. For the rest the regulating de
vice corresponds in construction and operation
to the already described devices, with the only
diference, however, that in the apparatus, 'iust
‘described and shown in'Fig. 5, it is the difference‘
of the thermal expansion between the tube ii 70
and the rod l9 which is used tocontrol the cone
vtact’s '29 and 99. The additional heating which
is known already for regulators consisting of hi‘
metal, has, however, hitherto never been used
Z
3
2,119,781
137 for heating that part of the receptacle between
in connection with expansion regulators com
prising a rod.
'
The eiiect obtained by the regulation may be
seen from the'regulating curves diagrammatical
ly indicated in Figs. 4 and 5. Fig. 4 shows the
the points of attachment of said element and of
said circuit maker and breaker, whereby the time
lag in the’action oi the circuit maker and break
er responsive to changes in temperature is di
regulating curve of a'box having the heating coil
arranged at the outside and provided with a closed
inner space into which immerses the-ieeler hav
ing no auxiliary heating coil. Fig. 5 shows the
regulating curve 01' a box of equal construction
10
in which the teeleris heated by an auxiliary heat
minished.
abscissa, also the switching-on temperature is the
same in both cases. The time of the switching
'15 periods,
however, is diilerently long from which
follows the higher exactness of regulation by the
use of the additionally heated regulator.
.
1. In an electrically'heated receptacle for pro
viding a chamber having a substantially constant
temperature, the combination of a receptacle hav
ing a cylindrical side wall-and having end walls,
one of said end walls constituting a closure, said
25 receptacle being constructed of ‘metal having a
high coe?lcient of thermal expansion, with an
insulating covering for said receptacle and‘an
enclosure for ,said insulating covering, electrical
heating elements located outside said receptacle
and inside said'insulating covering, an element
having a low coe?icient of thermal expansion lo
30
, cated outside said receptacle and having one end
?xedly secured to said receptacle adjacent one
edge of the cylindrical wall, a circuit maker and
breaker for controlling said heating elements and
' carried by said receptacle at a point spaced from
they ?xed end oi said ‘element, and'an operative
mechanical connection between the other end oi.’
said element and said circuit maker and breaker
whereby substantially uniform temperature is
-40 maintained in said receptacle, said receptacle
having an auxiliary heating coil controlled by said
circuit maker and breaker and ‘arranged prima
rily for heating that part of the receptacle between
the points of attachment of said element and
of said circuit maker and breaker, whereby the
time lag in the action of the circuit. maker and
breaker responsive to changes in temperature is
45
diminished.
,,
.
a
2. In an electrically heated receptacle for pro
50 viding_a chamber having a substantially con
stant temperature, the combination of a recep
tacle having a cylindrical side wall and having
end walls, one oi said end walls constituting a
55
60
\
65
»
circuit maker and breaker whereby any operating 10
temperature may be selected and maintained
ithin a predetermined rangepi temperatures.‘
curves have the same inclination towards the
-
'
circuit maker and breaker has means for contin
uously adjusting the point of actuation of said ‘
, ing coil. In both cases the heating- and cooling
What we claim is;
'
3. A device as claimed in claim 1 in which said
4. In an electrically heated receptacle for pro
viding a chamber having a substantially constant
temperature, the combination of a receptacle
having a _ cylindrical side wall and having ’ end
walls, one of said end walls constituting aclosure,
said receptacle being constructed of metal having
a high coe?icient oi thermal expansion, with an
insulating covering for said receptacle and an en 20
closure ior said insulating covering, electrical
heating elements located inside said insulating
covering, an element having a low coeiilcient of
thermal expansion carried by said receptacle and
having one end ?xedly secured to said receptacle 25
adjacent one edge or the cylindrical- wall, a .cir
cuit maker and breaker having a movable contact
carrying arm for controlling said heating ele
inents and carried by said receptacle at a point
spaced from the ?xed end of said element, and 30
an operative mechanical connection between the
other end of said element and said circuit maker
and breaker whereby substantially uniform tem
perature is maintained in said receptacle, said
element having a direct mechanical engagement,
with said arm to eliminate backlash in the actu
ation of said circuit maker and breaker.
5. A device as claimed in claim 4 in which said
element slidably engages said arm and said ele
40
ment has a shoulder for actuating said arm.
6. In an electrically heated receptacle for pro
viding a chamber having a substantially constant
temperature, the combination of a support with
a receptacle having a_,cylindrical side wall and
having end walls, said receptacle having its axis 45
extending substantially horizontallyand one of
said end walls constituting a closure, said recep
tacle being constructed of metal having a high
coei?cient of thermal expansion, with an insu
lating covering for said receptacle and an en 50
closure for said insulating covering, electrical
heating elements located outside said receptacle
and inside said insulating covering, an element
having a low coefiicient of thermal expansion lo
55
closure, said receptacle being constructed oi metal cated outside said receptacle and having one end
having a high coe?icient of thermal expansion, ?xedly secured to said receptacle adjacent one
with an insulating covering for said receptacle edge of the cylindrical wall, a circuit maker and
and an enclosure for said insulating‘ covering, breaker for controlling said heating elements and .
electrical heating elements located outside said carried by said receptacle at a point spaced from 80
receptacle and inside said insulating covering, an the ?xed endof said element, and an operative
mechanical connection between the other end of
element having a low coe?lcient of thermal ex
said element and said circuit maker and breaker
pansion located outside said receptacle and hav
whereby substantially uniform temperature is
ing one end ?xedly secured to said receptacle ad
jacent one edge oilthe cylindrical wall, a circuit maintained in said receptacle, said circuit maker 65
maker and breaker for controlling said heating and breaker being located outside said insulation
elements and carried by said receptacle at a and said element extending through said insula
.point spaced from the ?xed end of saidelement,
and an operative mechanical connection between
the other end of said element and said circuit
maker and breaker whereby substantially uni
70 form temperature is maintained in said recep
tacle. said element extending diametrically across
7 one end wall of said receptacle and said receptacle
having an auxiliary heating coil controlled by said
circuit maker and breaker and arranged primari
tion to said circuit maker and breaker.
7- A device as claimed in claim 4 in which the
end wall of said receptacle between said ?xed end
of said element and said circuit maker and break
er is reinforced with a member having substan
tially the same coe?lcient of thermal expansion
as said receptacle.
" 8. In an electrically heated receptacle for pro
viding a chamber having a substantially constant 75
4
2,112,731
temperature, the combination of a receptacle hav
ing side walls and having end-walls, one of said
walls constituting a closure, said receptacle be
ing constructed of metal having a high coemcient
of thermal expansion, with an insulating covering
for said receptacle and an enclosure for said in
sulating covering, electrical heatingelements .10
' cated inside said insulating covering, an element
having a low coe?icient of thermal expansion
carried by said receptacle and having one end
?xedly secured to said receptacle adjacent one
edge of an outer wall, a circuit maker and breaker
having a movable contact carrying arm for con
nection between the other end of said element and
said circuit maker and breaker whereby substan
tially uniform temperature is maintained in said
receptacle, said element having a direct mechan
ical engagement with said arm to eliminate back
lash in the actuation of said circuit‘maker and
breaker.
'
9. A device as claimed in claim 8 in which said
circuit maker and breaker has means for con- -
tinuousiy adjusting the point of» actuation of said
circuit maker and breaker whereby any operat
ing temperature may be selected and maintained
trolling said heating elements and carried by said
within a predetermined range of temperatures.
receptacle at a point spaced from the ?xed end
of said element, and an operative mechanical con~
HANS BRtiNING.
o'rro SCHULLER
15
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