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Патент USA US2069772

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Feb. 9, 1937.
G_ Q_ PEARCE
REFRIGERATION
Filed sept.- 29, 1932
2,069,772
Patented Feb. 9, 1937
2,069,772
UNITED STATES
PATENT- OFFICE
2,069,772
REFRIGERATION
George C. Pearce, Dayton, Ohio, assignor, by
' mesne assignments, to General Motors Cor
poration, a corporation of Delaware
Application September 29, 1932, Serial No. 635,391
21 Claims.
This invention relates to refrigeration, and
(Cl. 62-4)
character which operate continuously without
such a character and capacity, that it auto
matically maintains proper temperature condi
tions in the object to be cooled, notwithstanding
stopping for temperature adjustments in an ob
ject being cooled. Such systems are stopped a
such continuous operation. Such a system has
been more fully described in th’e copending ap
relativelyy few times compared with the stopping
plication, Serial No. 599,239, ñled March 16, 1932,
more particularly to refrigerating systems of the
operations of the usual intermittently operating ` to which reference is hereby made for a further
refrigerating system which stops for temperature disclosure of such a system.
adjustments in the object being cooled. In the
Briefly, such a system includes a compressor
continuously operating systems or in those sys
I0, a condenser II, an evaporator I2. The com- 10
tems which are designed to operate substantially
continuously and stop only for defrosting, repairs
presser discharges the compressed refrigerant to
or the like, or when the atmospheric temperature '
ñed refrigerant through the expansion device I3
to the evaporator I2 where the refrigerant is
evaporated and returns through the line Il to the 15
compressor Ill. The expansion device I3 may be
of any suitable character, but preferably is of
the elongatedmriiice type which maintains a
fixed, and continuously open orifice, so calibrated
drops below the normal range, the period of idle
ness is extremely long, so that the refrigerant
pressure in the system will become substantially
equalized throughout the system. Because of
this, these systems need not, and generally are
not, provided with special unloaders for the com
pressor, and 4therefore are likely to fail to re
start if an attempt is made to restart them
relatively soon after they have been stopped. It
may occur, in the operation of these systems, that
the line current, or source of electrical energy,
may fail for a relatively short period of time, due
N Ul
to an electrical storm or the like, and it is de
sirable that the refrigerating system should re
as to length and cross-sectional area, that it o
maintains the evaporator I2 at the proper tem- “0
perature to maintain the object being cooled at
a substantially constant temperature notwith-`
standing variations in the surrounding atmos
phere. In such a system, the elongated orifice
in the expander I3 permits a continuous passage 25
of refrigerant therethrough, and should the com
presser I0 stop temporarily, this iiow through the
start automatically and safely after such a tem
porary failure of the linelcurrent.
the condenser I I which in turn discharges lique
.
It is among the objects of this invention to
5,3 D
provide a control for the electric motor which
drives the refrigerating system which is capable
of automatically starting the motor when the
current is turned on by the user, and which is
capable of restarting the system safely if the
line current, or source of electrical energy should
be turned off temporarily and then be turned on
orifice continues and in a relatively short time
equalizes >the pressures throughout the refriger
ating system, so that if the compressor should be 30
restarted after such a short time, it. starts with
substantially no load.
Under ordinary conditions, such a system is
stopped only for the purpose of defrosting the n
evaporator I2 and this defrosting operation is ""
performed only once or twice a month and is not
before the refrigerantv pressure has equalized
of the type of stopping operation which is in
sufficiently to permit the motor to start.
tended to maintain temperature conditions in the
object being cooled. On the contrary, such a
Further objects and advantages of the present
invention will be apparent from the following
description, reference being had to the accom
panying drawing, wherein a preferred form of the
present invention is clearly shown.
In the- drawing:
Fig. l is a diagrammatic representation of a
system embodying the features of my invention;
and
-
“In
being cooled to warm above the desired tempera
ture, 'but the operation is performed because of
the large accumulation of frost on the evaporator
and because of its undesirable inconvenience.
After such a stopping operation and because of
'its long duration, the compressor starts under
no load characteristics and hence the compressor
'
Fig. 2 is a diagrammatic representation of a
7.0 slightly modified system.
stopping operation generally permits the object
. `
A refrigerating system embodying features of
this invention is designed to operate continuously
during the normal atmospheric temperature
range maintained in a dwelling Without stopping
for cabinet temperature adjustments, and is of
need not be provided with unloading mechanism,
other than the expander I3 itself. The motor
I5 for driving the compressor may be of the split
phase type which is provided with a starting
winding I6 and a running winding IT, and, as
is usual with this type oi' motor` theV starting
torque is small. Such a motor compresser unit
50 '
‘ à
2,069,772
is capable of startingy only if the entire refrig
eration system has become substantially equal
tem has become thoroughly equalized before
ing the pressure differential load during the
again'attempting to start the motor. To this end
another control 26 is provided. This control re
quires a longer period of time before it becomes
operative than is required by the control 2| and
starting period. . In this particular system, no
also maintains the circuit open for a longer
unloader need be used, as it is possible to permit
period after such failure to start than the
ized as to pressure throughout, or if the unit isv
provided with an automatic unloader for remov
the system to equalize during the infrequentstops ' period maintained by the control 2|. Thus the
which may be necessary.
control 2| may cycle several times before the
The starting control for such a system includes
a device or relay |8 for maintaining a ñow 'of
control 26 becomes operative.
This may be ac
complished by mounting the thermostatic strip
current from the source of electrical supply A ~ 21 on the motor casing 28. This strip 21 actuates
through the starting winding during the start
ing period and for stopping the now of said
15 current at the termination o'f the starting period.
'I‘he control also includes devices for rendering
the means or relay I8 safely reoperative after a ‘
temporary failure of the source of electrical
_energy and for preventing too frequent a start
20 ing and stopping of the motor after such failure
of such source of electrical energy if the com
pressor should fail to permit the motor to start.
To this end the relay I8 may' include a solenoid
I8 in series with the running winding I1 whichv
actuates the contact 20 for energizing the start
ing winding I6. 'I'he construction is such that
the surgecurrent running through the running
winding during the starting period is sufñcient
to pull the contact 20 against gravitational forces,
30 or against a magnetic force, during the starting
period of the motor so that the starting winding
I8 is energized during such period; but the sole
noid I9 is not of sufficient strength-to hold the
contact 2D in closed position after the current
through the winding |1 drops to the normal run
ning value at the termination of the starting
period.
‘
An overload relay 2| is provided which prevents
the surge current from running through the mo
tor for `too long a period of time if the motor
4should. fail to start. Thus means are provided
for opening the electrical circuit if the motor
fails to start after a predetermined period. To
this end an overload relay 2| is provided in the
45 formr of a resistance 22 which heats the thermo
static strip 23 yto open the contact 24 with a snap
action against a resistance such as the permanent
magnet 25. 'I'hus if the motor should fail to start
after a predetermined period, the resistance 22
50 becomes heated and'causes the thermostatic strip
23"to maintain the circuit open until the resist
ance 22 and the thermostatic strip 23 become
-cooled. 'I'his control may be so constructed that
f the heating and cooling period may- be of' any
55
desired length, for example, two minutes each, so
that if the motor fails to start for two minutes
after it has been‘re-energized, the Vcircuit will
remain open for two minutes lWhile the control
65
70
'
to a predetermined temperature. The length of
time required to heat the strip 21 to this tempera
ture is much longer than that required to heat
the strip 23, because the casing 28 contains more
metal than is contained in the resistance `22 and 20
therefore heats or cools much more slowly. The
strip 21 is adapted to close the contact29 after
the casing 28 has cooled to a predetermined
temperature, and this cooling period is much
greater in length than the cooling period of the
resistance 22.
Thus if the motor l5 failsA to_
start after several attempts have been initiated
by the control 2|, the control 26 opens the cir
cuit and maintains it open for a major period of
time which is much longer than the minor periods
of rest maintained by the control 2|. '
A manual control for stopping and starting the
system by the user for defrosting, or the like,
may be provided.
Conveniently one of the con
tacts already provided may be used. Thus a 35
stop 3| may be provided on the rod 32, which
rod may be slidably connected with strip 23 in
such a manner that the contact 24 may be opened
without disturbing the strip 23. A snap acting,
manually operated, lever construction 33 is pro 40
vided to engage the hook> 34 which forms an ex
tension of the rod 32. Thus the user may op
erate the lever construction 33 to open the
contact 24 or may operate it to permit the
contact 24 to be governed by the control 2|.
45A
In the modification shown in Fig. 2, means are
provided _which require a manual reset if the
motor fails to start after a repeated number of
starting attempts after a temporary line fail
ure. To this end the control 26 of Fig. 1' is re 50
placed by a manual reset control 48 shown in Fig.
2. The remaining portion of the system, having
numerals similar to this Fig. 1, but with the
suflix “a” attached, may be the same as the sys
tem shown in Fig. 1. The manual reset control 40 55
may include a spring member 4| tending to open
the contact .42 whichin turn opens the electric
circuit leading to the motorl |0a. The spring 4|
is prevented from opening the 'contact 42 by
ing the heating and cooling'of the relay 2|, the ’ means of a hook l43 which is,in engagement with
refrigerant continuously iiows through the ex
the ratchet wheel 44. The ratchet wheel ‘44 is
pander I3, and reduces the refrigerant pressure soldered to-the stationary shaft 45 mounted on
diilerential in the compressor, so that the com
the motor casing 28a by means of low melting
pressor offers less starting resistance to the mo
point solder. After repeated attempts to start
tor I 5 after the expiration of such four minutes, the motor by means of the automatic control 2| a, 65
when the circuit is again closed, and the motor the motor casing 28a becomes overheated and
once again ~attempts to start. If unsuccessful melts the solder which holds the ratchet wheel
again, the control 2| heats again and thus per
44 stationary on the shaft 45. When the solder
mits another four minute period to lapse before is melted, the ratchet wheel turns and permits
the third attempt is made to restart the motor. the spring 4| to open the contact 42, and thus 70
It sometimes occurs that in the repeated opens the circuit to the motor |5a. The circuit
starting attempts above described, the motor be remains open, until the button 46 is manually
comes overheated and it is therefore desirable to operated to close the contact 42 and to engage
provide a long period of rest to permit the motor the hook 43 in the ratchet 44 after the casing
to cool and to insure that the refrigerating sys
28a has cooled sumciently to permit the-solder to 7'5
2| is cooling. During these four minutes involv
60
the contact 29 against a resistance such as the
permanent magnet 30 to open the circuit with
a snap action after the strip 21 has been heated
3
2,069,772
solidify and again prevent the ratchet 44 from
turning.
circuit.
While the form of embodiment of the invention
as herein disclosed, constitutes a preferred form,
it is to be understood that other forms might be
adopted, all coming Within the scope of the
claims which follow.
period of rest being effective to reclose the motor
.
What is claimed is as follows:
1. A refrigerating system including a compres
sor, condenser and evaporator in a closed refrig
erant cycle, an electric motor for driving said
compressor, said motor having a starting Winding
and a running winding, a source of electrical
energy, a starting control switch for maintaining
' the iiow of current from said source through said
starting Winding during a starting period and for
stopping the ñow of said current at the termina
tion of said starting period, means for rendering
,
,
5. In a refrigerating apparatus, the combina
tion of a compressor, a condenser, a constantly
open liquid refrigerant control device, and an
evaporator in a closed refrigerant circuit, an elec
tric motor for driving said compressor having a
starting torque insuiiìcient to start the compres
sor against pressure differences of the order exist
ing thereacross during normal operation of the 10
apparatus, said motor having a starting winding
and a running winding, a first circuit controller
for controlling the starting winding, a second cir
cuit controller for controlling at least the run
ning winding, means adapted to open the first
circuit controller when the motor approaches
running speed after starting, and means for open
ing the second circuit controller upon the flow
said starting control switch temporarily inoper
of excessive current and for automatically clos
ative after failure of said electric motor to restart
ing theA second circuit controller after an in 20
terruption of the flow of current to the running
after a temporary failure of ‘said source of electri
cal energy, and a continuously open expansion
device between said-condenser and evaporator.
2. `A refrigerating system including a compres
sor, condenser and evaporator in a closed refrig
erant cycle, an- electric motor for driving said
compressor, said motor having a starting Winding
and a running Winding, a source of electrical en
, ergy, a starting control switch for maintaining
the ñow o_f current from said source through said
starting winding during a starting period and for
stopping the flow of said current at the termina
tion of said starting period, means for rendering
winding.
6. In a refrigeratlng apparatus, the combina
tion of a compressor, al condenser, a constantly
open liquid refrigerant control device, and an 25
evaporator in a closed refrigerant circuit, an elec
tric motor for driving said compressor having a
starting torque insufficient to start the compres
sor against pressure diñerences of the order ex
isting thereacross during normal operation of the 30
apparatus, said motor having a starting winding
and a running winding, a ñrst circuit controller
for controlling the starting winding, a second cir
said starting control switch temporarily inopera ‘ cuit controller for controlling> both windings,
" tive after failure of said electric motor to restart ' means adapted to open the first circuit controller 35
after a. temporary failure of said source of elec
when the motor approaches running speed after
trical energy, a continuously open expansion de
vice between said condenser and evaporator, and
means responsive to temperature of said motor
starting, and means for opening the second cir
cuit controller upon the iiow of excessive current
and for automatically closing the second circuit
controller after an interruption _of .the flow of 40
ative while said motor is over-heated.
3. Refrigerating apparatus including a com
pressor, condenser, and evaporator connected in
current to the running winding.
40 for rendering said starting control switch inoper
a closed circuit, said closed circuit having a con
45 tinuously open restricted connection between the
condenser and evaporator for controlling the iiow
of refrigerant to the evaporator during the oper
7. In a refrigerating apparatus, the combina
tion of a compressor, a condenser, a constantly
open liquid refrigerant control device, and an
evaporator in a closed refrigerant circuit, an elec 45
tric motor for driving said compressor having a
starting torque insufficient to start the compressor
against pressure differences of the order existing
thereacross during 4normal operation of the appa
ratus, said motor having a starting winding and 50
a running winding, a first circuit controller for
ation of the compressor, and for equalizing pres
A.Sures 'within the system to unload the compressor
when the compressor is idle, an electric motor
having a starting circuit and a running circuit
for driving the compressor, means for connecting
controlling the starting winding, a second cir
the starting circuit to a source of electric energy,
cuit controller for controlling at least the run
and means for opening the motor circuit and for
ning winding, means adapted to open the iirst
55 preventing the energization of said first men
tioned means when the pressures in the closed
refrigerant circuit have not equalized sufiiciently
to permit starting of the electric motor, said
opening means including means for reclosing the
motor circuit after a period of rest.
e. Refrigerating apparatus. including a com
pressor, condenser, and evaporator connected in a
closed circuit, said closed circuit having a contin
uously open restricted connection between the
65 condenser and evaporator for controlling the flow
of refrigerant to the evaporator during the oper
ation of the compressor, and for equalizing pres
sures Within the system to unload the compresso-r
when the compressor is idle, an electric motor
having a starting circuit and a running circuit
for di iving the compressor, means for connecting
the starting circuit to a source of electric energy,
and means for opening the motor circuit when
said i‘lrst mentioned means is ineffective to start
the electric motor, said opening means after a
circuit controller when the 'motor approaches run 55
ning speed after starting, and means for opening
the second circuit controller upon the ’flow of
excessive current and for automatically closing
the second circuit controller after an interrup
tion of the iiow of current to the running wind 60
ing, said last named means including time delay
means for preventing maintenance of the second
circuit controller in closed position until a pre
determined time has elapsed after the occur
rence of an excessive current flow in the motor. 65
8. In a refrigerating apparatus, the combina
tion of a compressor, a. condenser, a constantly
open liquid refrigerant control device, and an
evaporator in a closed refrigerant circuit, an elec
tric motor for driving said compressor having 70
a starting torque insufficient to start the corn
pressor against pressure diiîerences of the order
existing thereacross during normal operation of
the apparatus, said motor having a starting
Winding- and a running Winding, a first circuit 75
4-
»
'
2,069,772
controller for controlling the starting vvinding,
ning speed after starting, and means for opening
cuit controller for controlling the starting wind
ing, a second circuit controller for controlling
at least the running winding, means adapted to
open the ñrst circuit controller when the motor
approaches running speed afterstarting, and
the second circuit controller upon theV flow of
means for opening the second circuit controller
excessive current and for automatically closing
the second circuit controller' after an interrup
upon the flow of excessive current.
- 12. In 'a refrigerating apparatus, the combina
tion of a compressor, a condenser, a constantly
open -liquid refrigerant control device, and an 10
a second circuit controller for controlling both
windings, means _adaptedto open the iirst cir
cuit controller when the motor approaches run
` tion of the flow of current to the runningv Wind
10 ing, said last named means including time delay
means for preventing maintenance of the second
circuit controller in closed position until a pre
determined time has elapsed after the occurrence
of an excessive current flow in the motor.
9. I_n a refrigerating apparatus, the combina»
tion of a compressor, a condenser, a constantly
open liquid refrigerant` controlfdevice, 'and an
evaporator in a closed refrigerant circuit, said
Acompressor' being constantlyexposed to the pres
20 sures existing in the evaporator and condenser,v
evaporator in a closed refrigerant circuit, said
compressor being constantly exposed to the pres-l
sures existing in the evaporator and condenser,
an electric motor for driving said compressor
having a starting torque insuillcient to .start the
compressor against pressureV differences of the
order existing thereacross during normal opera
tion of the apparatus, said motor having a start- e
ing winding and a running Winding. a'hermeti
cally sealed casing enclosing the motor` and com
an electric motor Afor driving said compressor '- pressor, a first circuit controller f_or controlling
having a starting torque insufficient to start the the starting winding, a second circuit controller
compressor against pressure differences of the vfor controlling' at least the running winding,
order existing thereacross during normal opera
25 tion of the apparatus, said motor having a start
ing winding .and a running winding, 'a ñrst cir
cuit controller for controlling the startingwind
ing, a second circuit controller for controlling
5
so
means adapted to open'thé first circuit controller
when` the motor approaches running -speed after I
starting, and means for opening the second cir
cuit controller upon ~the flow of excessive current.
13. In a refrigerating apparatus, the combina
at least the running winding, means adapted to . tion of a, compressor, a condenser, a constantly
30 lopen the first circuit controller when the motor
open liquid refrigerant control device, and a'n
-approaches running speed after starting, and evaporator in a. closed refrigerant circuit, said - ~
means for opening the second circuit controller
upon the flow of excessive current ‘and for auto-matically closing the second circuit controller
35 after an interruption of the flow of current to.
_the running winding.
10. In a refrigerating apparatus, the combi
nation'of a compressor, a condenser, a constantly
open_` liquid refrigerant control device, and an
'40 evaporator in a closed refrigerant circuit. said
compressor being constantly exposed to the pres
compressor being constantly exposed to the pres
sures existing in the evaporator and condenser,
an electric motor for driving said compressor
having -a starting torque insufilcient to start the
compressor against pressure diiîerences of the
order existing thereacrcss during normal opera-_
>tion of the apparatus, and means for interrupt
ing theñow of current to the motor after cur
rent flow is initiated at a time when the pressure
difference-between the condenser and the evap
orator is_ tooïgreat to permitthe motor to start.
14. Refrigerating apparatus including a closed
an electric- motor for driving said compressor ,
having. a starting torque insufñcient to startthe I refrigerant vsystem comprising a compressor, con
compressor against pressure differences of the denser, and evaporator, an electric motor having 45
sures existing in theevaporator and condenser,
order existing thereacross during normal-opera
a starting circuit and a running circuit for drivingl
- approaches running speed; after starting, and
means- for opening the second -circuit controller
for connectingthe starting circuit to a source of
velectric energyto start the compressor, and means
«the running winding, said last named means
been reduced sumcientlyto permitstarting of the
tionof the apparatus, said motor having a start -the compressor> to circulate refrigerant and to
create a pressure difference in the system on
ing winding a'nd a running winding, a` first cir
cuit controller for controlling the starting wind . either side of. the compressor, said system being
ing, a second circuit controller for controlling provided wlthmeans for reducing the pressure 50
at least the 'rlmning winding, means adapted to ` diñerential across the compressor when the com
Íopen the first circuit controllenwhen the motor presser is idle `-to unload the compressor, means
55 upon the ñow- of excessive current and for auto V>for opening the motor circuit for preventing-the
matically closing the second circuit -controller energization of the electric motor when the pres
after an interruption of the .now of current to sure dlll’erential across'the compressor has vnot
:
including time delay means for preventing main#- „ electric motor, said opening means including
tenance of the `second circuit controller in closed means for reclosing- the motor circuit after a. 60
position until a predetermined time has elapsed ' period
_
o: rest,
after the occurrence ofen 'excessive current flow , 15. Rerrigersuns apparatus including 'a dosed '
in the motor.
`
- ` ~ refrigerant system'comprising-a compressor, con
11. In a refrigeratingappsrstus. the combina
tion of a compressor, ,s condenser, a constantly'
70
denser, and evaporator, an electric motor having
¿starting circuit and a running` circuit for driving
the compressor -to circulate refrigerantk and to
vcreate s_pressure diñerenceA in >the systemen
~either
provided".
side_with
of Athe
means'
compresso
for reducing
, said'. system
the pressure
open' liquid refrigerant .control device. and an
evaporator. in a closed refrigerant circuit,~ said
compressorÁ being constantly expgsed' to the pres- A
sures existing inthe evaporator and condenser,
an electricmotor for driving said compressor Vdifferential across the compressor when the com 70
having a starting torque insuillcicnt to start' the ,p1-essor ¿isidle to unload. the compressor, means
compressor against 'pressure differences of. the - for connecting the startingcircuitto-a source of '
order' existing _thereacross during normal opera.-A electric energy@ startthe compressor, land means
tion ofthe apparatus, said motor having a start
‘ing-windingandarunningwindiug.aflrstcir-
responsiverto the electric' motor current- and to
electric motor
îfor preventing the 75
5
2,089,779
energization of the electric motor under danger
ous conditions.
16. Refrigerating' apparatus including a closed
refrigerant system comprising a compressor, con
denser, and evaporator, an electric motor having
a starting circuit and a running circuit for driving
the compressor to circulate refrigerant and to
create a pressure difference in the system on
either side of the compressor, said system being
10 provided with means for reducing the pressure
differential across the compressor when the com
pressor is idle to unload the compressor, means
for connecting the starting circuit to a source of
electric energy to start the compressor, and means
15 responsive to the electric motor current and toi`
electric motor temperature for opening the elec- -
tric motor circuit under dangerous conditions and
thereafter closing the circuit automatically when
the condition has improved.
17. A refrigerating system including a com
pressor, a condenser and an evaporator in a closed
refrigerant circuit, an electric motor for driving
said compressor, said motor having a starting
winding and a running Winding, a source of elec
25 trical energy, means for maintaining the ñow
of current from said source through said start
ing Winding during a starting period and for
stopping the ilow of said current at the termina
tion of said starting period, means for rendering
30 said ñrst named means reoperative after a tem
porary interruption in the supply of electrical
energy, means for preventing the flow of current
through said windings for a predetermined period
of time if said temporary interruption should
35 prove to be of insufiicient duration to unload said
refrigerating system, said period of time being
longer than said starting period, and means for
equalizing refrigerant pressures in said system
40
during said predetermined period. ~
1S. A refrigerating system including a com
pressor, a condenser and an evaporator in a closed
refrigerant circuit, an electric motor for driving
said compressor, said motor having a starting
winding and a running Winding, a source of elec
trical energy, means for maintaining the fiow of
current from said source through said sîarting
winding during a starting period and for stopping
the flow of said current at the termination
of said starting period, means for rendering
said ñrst named means reoperative after a tern
porary interruption in the supply of elec
trical energy, means for preventing the flow
of current through said windings for a prede
termined period of time if said temporary inter
55 ruption should prove to be of insufficient dura
tion to unload said refrigerating system, said
period of time being longer than said starting
period, and a continuously open expansion de
vice between said condenser andy evaporator for
equalizing refrigerant pressures in said system
during said predetermined period.
19. A refrigerating system including a com
pressor, a condenser and an evaporator in a closed
refrigerant circuit, an electric motor for driving
said compressor, said motor having a starting
winding and a running winding, a source of elec
trical energy, means for maintaining the flow of
current from said source through said starting
winding during a starting period and for stop
ping the ñow of said current at the termination
-of said starting period, means for rendering said
ñrst named means reoperative after a temporary
interruption in the supply of electrical energy,
means for preventing the flow of current through
said windings for a predetermined period of time
if said temporary interruption should prove to be
of insuñîcient duration to unload said refriger
ating system, and means for equalizing refrig
erant pressures in said system during said prede
termined period.
.
20. A refrigerating system including a com
pressor, a condenser and an evaporator in a closed
refrigerant circuit, an electric motor for 'driving
said compressor, a hermetically sealed casing en 20
closing said motor and compressor, said com
pressor being constantly subjected to the pres
sure difference between the condenser and the
evaporator, said motor having a starting winding
and a.running winding, a source of electrical en 25
ergy, means for maintaining the flow of current
from said source through said starting winding
during a starting period and for stopping the ñow
of said _current at the termination of said start
ing period, means for rendering said first named 30
means reoperative after a. temporary interrup~
tion in the supply of electrical energy, means for
preventing the ilow of current through said Wind
ings for a predetermined period of time if said
temporary interruption should prove to be of in~ 35
suliicient duration to unload said refrigerating
system, said period of time being longei` than
said starting period, and means for equalizing re
frigerant pressures in said system during said pre
determined period.
4 c.
21. A refrigerating system including a com
pressor, a condenser and an evaporator in a closed
refrigerant circuit, an electric motor for driving
said compressor, a hermetically sealed casing en
closing said motor and compressor, said com
pressor being constantly subjected to the pressure
difference between the condenser and the evapo
rator, said motor having a starting winding and
a running winding, a source of electrical energy,
means for maintaining the flow of current from 50
said source through said starting winding during
a starting period and for stopping the flow of
said current at the termination of said starting
period, means for rendering said ñrst named
means reoperative. after a temporary interrup 55
tion in the supply of electrical energy, means for
preventing the flow of current through said wind
lings for a predetermined period of time if said
temporary interruption should prove to be of in
sufficient duration to unload said refrigerating
system, and means for equalizing refrigerant
pressures in said system during said predeter
mined period.
GEORGE C. PEARCE.
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