U.S. patent number 3,599,006 [Application Number 04/850,012] was granted by the patent office on 1971-08-10 for condition control device and system.
This patent grant is currently assigned to Deltrol Corp.. Invention is credited to John L. Harris.
United States Patent |
3,599,006 |
Harris |
August 10, 1971 |
CONDITION CONTROL DEVICE AND SYSTEM
Abstract
A number of compressor motors or electric beaters are turned on
and off in sequence to avoid line surges. Each load switch consists
of two flexible blades raised by a cam with the contacts separated.
A latch serves to hold one blade up when the blades are lowered by
the cam, causing contact engagement. A solenoid releases the
latches of all the switches to open them simultaneously in response
to a thermostat becoming satisfied or indicating an unfavorable
condition. Special circuitry protects against compressor short
cycling when the control is applied to refrigeration.
Inventors: |
Harris; John L. (Dalafield,
WI) |
Assignee: |
Deltrol Corp. (Bellwood,
IL)
|
Family
ID: |
25307049 |
Appl.
No.: |
04/850,012 |
Filed: |
August 14, 1969 |
Current U.S.
Class: |
307/39; 219/486;
307/116; 200/50.37; 62/158; 200/39R; 307/41; 392/347 |
Current CPC
Class: |
H02P
1/58 (20130101); G05B 19/063 (20130101) |
Current International
Class: |
H02P
1/58 (20060101); G05B 19/06 (20060101); H02P
1/16 (20060101); G05B 19/04 (20060101); G05g
021/00 (); H01k 043/12 () |
Field of
Search: |
;62/157,158,231
;307/39,41,116,117,115 ;317/25 ;200/30,39,5C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Smith; William J.
Claims
I claim:
1. In a control system for a condition changing system having a
plurality of condition changing units, the combination of, a
condition responsive device, motor driven actuating means, means
for starting said actuating means in response to a predetermined
condition at said condition responsive device, a plurality of load
switches connected to different condition changing units, means
operated by said motor driven actuating means for mechanically
actuating said load switches in sequence thereby activating the
condition changing units in sequence when the condition responsive
device calls for a condition change, control means for stopping
said motor driven actuating means after it has operated the load
switches to activate the condition changing units, a control
device, means mechanically connecting said control device with said
load switchs for actuating said load switches independently of said
motor driven actuating means in a manner to deactivate the
condition changing units when the control device is moved in one
direction, means mechanically actuated by movement of the control
device in said one direction for actuating said control means in a
manner permitting continued operation of the motor driven actuating
means, and means for actuating said control device in said one
direction in response to a predetermined condition.
2. The combination as set forth in claim 1 in which the control
means for the motor driven actuating means consists of a motor
switch connected in circuit with the motor, said motor switch being
operated in one direction by the motor driven actuating means after
the load switches are actuated in sequence, said motor switch also
being operated in the opposite direction by the control device
substantially simultaneously with actuation of the load switches by
said control device.
3. The combination as set forth in claim 2 in which the motor
driven actuating means closes the load switches and opens the motor
switch in sequence and in which the control device is an electric
magnet which on deenergization opens the load switches and recloses
the motor switch substantially simultaneously.
4. The combination as set forth in claim 1 in which the control
device is an electromagnet and in which a single condition
responsive device controls both the electromagnet and the motor
driven actuating means, the load switches being closed in sequence
in response to one condition at the condition responsive device,
and being opened substantially simultaneously in response to
another condition at the condition responsive device.
5. The combination as set forth in claim 1 in which the condition
responsive device controls only the motor driven actuating means,
and the control device is actuated by a separate condition
responsive device responsive to a condition of the condition
changing system.
6. In a control system for a condition changing system having a
plurality of condition changing units, the combination of a
condition responsive device, motor driven actuating means, means
for starting said actuating means in response to a call for
condition change by said condition responsive device, a plurality
of load switches connected to different condition changing units,
means operated by said actuating means for mechanically actuating
said load switches in sequence, thereby activating the condition
changing units in sequence when the condition responsive means
calls for a condition change, means for stopping said actuating
means when the load switches have been actuated for activating the
condition changing units, said motor driven actuating means also
being arranged to mechanically operate said load switches in
sequence for deactivating the condition changing units in sequence
upon continued movement of said actuating means, means for
restarting the actuating means in response to the condition
responsive means becoming satisfied, thereby deactivating the
condition changing units in sequence, a control device, means
actuated by said control device for mechanically operating said
switches in a manner to deactivate the condition changing units
substantially simultaneously and independently of said motor driven
actuating means, and means for actuating said control device in
response to a predetermined condition for causing simultaneous
deactivation of said condition changing units.
7. The combination as set forth in claim 6 in which the control
means for the motor driven actuating means consists of a motor
switch connected in circuit with the motor, said motor switch being
actuated in one direction by the motor driven actuating means after
the load switches are actuated in sequence, said motor switch also
being operated in the opposite direction by the control device
substantially simultaneously with operation of the load switches by
said control device.
8. The combination as set forth in claim 7 in which the load
switches are closed to activate the condition changing units and
the motor switch is closed to stop the motor by shunting the same
and in which the control device is an electromagnet which upon
deenergization opens the load switches and the motor switch.
9. In a control system for a condition changing system having a
plurality of condition changing units, the combination of, a
condition responsive device having a switch which closes upon call
for condition change and which opens when satisfied, control means
including a motor driven actuator having a drive motor and a
plurality of switches connected to different condition changing
units, said actuator being arranged to actuate said switches in
sequence as the actuator moves from an "off" position to a "run"
position, said actuator also being arranged to open said switches
when the actuator returns from the "run" position to the "off"
position, a power source for the drive motor capable of being
shunted without damage, first circuit means including a first motor
control switching means controlling power to the drive motor, said
first motor control switching means being actuated by the actuator
and said circuit means and switching means being connected and
arranged to place the drive motor in circuit with the condition
responsive device switch when the actuator is in the "off"
position, and to provide an independent circuit for the drive motor
when the actuator is away from the "off" position, second circuit
means including a second motor control switching means, said second
circuit means being connected and arranged to shunt the power
source in series with the condition responsive device switch, said
second motor control switch being operated by the actuator and
arranged to close when the actuator is in the "run" position.
10. In a control system for a condition changing system having a
plurality of condition changing units, the combination of, a
condition responsive device, motor driven actuating means, said
actuating means comprising a plurality of actuators and a motor for
driving same, a plurality of load switches connected to different
condition changing units, said load switches being operated by
different actuators and individually comprising a first switch
blade, a second switch blade, cooperating contacts carried by the
switch blades, the first switch blade being biased toward the
second switch blade tending to cause engagement of the contacts,
the second switch blade being biased in the same direction tending
to cause disengagement of the contacts, means including one of said
actuators for moving both of said switch blades against their bias
with the contacts separated to predetermined position and then
releasing the blades, a plurality of latches, said latches being
arranged to support the second switch blade of different load
switches after release by the corresponding actuator for causing
engagement of the load switch contacts, control means controlled by
the condition responsive device for starting said motor driven
actuating means in response to a predetermined condition thereby
activating said condition changing units, control means for
stopping said motor driven actuating means after it has operated
the load switches to activate the condition changing units, and
means including a latch actuator for actuating said latches to
release said latches in response to a predetermined condition,
thereby opening said load switches.
11. The combination as set forth in claim 10 in which the control
means for the motor driven actuating means consists of a motor
switch connected in circuit with the motor, said motor switch being
operated in one direction by the motor driven actuating means after
the load switches are actuated, said motor switch also being
operated in the opposite direction by the latch actuator when it
releases the latches.
12. The combination as set forth in claim 11 in which the motor
driven actuating means closes the load switches and opens the motor
switch in sequence, and in which the latch actuator is operated by
an electromagnet which on deenergization releases the latches and
recloses the motor switch.
13. The combination as set forth in claim 11 in which an
electromagnet operates the latch actuator and in which the
condition responsive device controls both the electromagnet and the
motor driven actuating means, the load switches being closed in
sequence in response to one condition at the condition responsive
device and being opened substantially simultaneously in response to
another condition at the condition responsive device.
14. The combination as set forth in claim 10 in which the condition
responsive device controls only the motor driven actuating means,
and the latch actuator is actuated by a separate condition
responsive device responsive to a condition of the condition
changing system.
15. In a controller for sequentially controlling a plurality of
loads, the combination of, a plurality of load switches, motor
driven actuating means for actuating said load switches, said
actuating means comprising a plurality of actuators and a motor for
driving the same, said load switches being operated by different
actuators and individually comprising a first switch blade, a
second switch blade, cooperating contacts carried by the switch
blades, the first switch blade being biased toward the second
switch blade, said second switch switch blade being biased in the
same direction, means including one of the actuators for moving
both of the switch blades against their bias to predetermined
positions and then releasing said blades, a plurality of latches,
said latches being arranged to support one of the switch blades of
different switches after release by the corresponding actuator,
control means for stopping the motor driven actuating means after
it has released said switches, and means for releasing said latches
and operating said control means to permit continued operation of
said motor driven actuating means.
16. The combination defined in claim 15 in which the control means
for stopping the motor is a switch in circuit with the motor and
having a latch for maintaining it closed, said last mentioned latch
being released with the other latches.
17. In a multiple switch controller, the combination of, a
plurality of switches, motor driven actuating means arranged to
mechanically actuate said switches, a series of separate and
independently mounted latches arranged to hold said switches in
actuated position, means for releasing one of said latches, and
means actuated by releasing motion of said one latch for engaging
and releasing another of said latches.
18. The combination as set forth in claim 17 in which the first
latch is provided with a camming surface arranged to cause
additional movement of the latch after movement to releasing
position, said additional movement being imparted by the switch it
released and causing movement of said other latch in releasing
direction.
19. In a timing device, a cam, first and second switch blades
carrying cooperating contacts and each biased toward said cam,
means providing a first cam follower surface carried by the first
switch blade and riding the cam, means providing a second cam
follower surface carried by the second switch blade and riding the
cam, said cam having a main camming surface and a dropoff section,
the cam follower surfaces and the switch blades being arranged to
provide a gap between the contacts when both cam follower surfaces
are riding the main camming surface of the cam, a latch arranged to
support one of the switch blades in a manner to cause and maintain
engagement of the contacts after the cam follower surfaces have
been passed by the dropoff section of the cam, and means for
releasing said latch to cause disengagement of said contacts.
20. The combination defined in claim 19 in which the means for
releasing the latch is actuated with the cam and releases the latch
at a predetermined position of the cam.
21. The combination set forth in claim 19 in which the means for
releasing the latch consists of an electromagnet arranged to
release the latch upon actuation thereof.
22. The combination set forth in claim 20 in which an electromagnet
is arranged to release the latch independently of the first named
latch releasing means.
23. In a control system for a condition changer, circuit means
including a load switch for controlling the condition changer,
operating means for the switch including a motor driven actuator,
said operating means including actuated means raised by motion of
the motor driven actuator and lowered when the actuator reaches a
predetermined position, said operating means also including a latch
movable from latching to releasing position and vice versa, the
latch and actuated means being constructed and arranged to cause
operation of the switch to start the condition changer when the
actuated means is lowered with the latch in latching position and
to stop the condition changer when latch is moved to releasing
position, means including condition responsive device arranged to
start the motor driven actuator from a first position in response
to a predetermined condition, means for stopping the motor driven
actuator in a second position after it has started the condition
changer, means for releasing the latch and restarting the motor
driven actuator in response to a predetermined condition and means
for stopping said motor driven actuator at said first position.
24. The combination as set forth in claim 23 in which the means for
stopping the motor driven actuator consists of a motor switch
controlling the motor of the motor driven actuator, said switch
being held open by a latching means released substantially
simultaneously with the load switch latch.
25. In a control system for a refrigeration system having a
compressor, the combination of, a power circuit for the compressor,
control means for said power circuit including a condition
responsive device, a timing device, and an electromagnet, control
circuit means including the condition responsive device, the timing
device and the electromagnet for causing closure of said power
circuit to start the compressor in response to a call for condition
change, the control circuit means also being arranged to open the
power circuit in response to the condition responsive device
becoming satisfied, the timing device being arranged to interpose
an equalization delay between opening and closure of the power
circuit sufficient to allow suitable pressure equalization in the
system and to provide an additional delay in event of a short
cycle, the overall time cycle of the timing device including both
delays, means for causing operation of the timing device through
the additional delay period when the compressor starts and for
stopping the timing device at the end of this period if the
compressor is still in operation, means for restarting the timing
device when the compressor is stopped, and means for stopping the
timing device when the equalizing period is substantially
consumed.
26. In a control system for a refrigeration system having a
compressor, the combination of, a power circuit for the compressor,
control means for said power circuit including a condition
responsive device a timing device, and an electromagnet, control
circuit means including the condition responsive device, the timing
device and the electromagnet for causing closure of said power
circuit to start the compressor in response to a call for condition
change, the control circuit means also being arranged to open the
power circuit in response to the condition responsive device
becoming satisfied, the timing device being arranged to provide an
initial delay period between call for condition change and starting
of the compressor, an equalization delay period between opening and
closure of the power circuit sufficient to allow suitable pressure
equalization in the system, and an additional delay period in the
event of a short cycle, the overall time cycle of the timing device
including all three delay periods, the condition responsive device
being arranged to start the timing device on call for refrigeration
and the timing device initiating said closure of the power circuit
for the compressor at the end of said initial delay period, means
for causing operation of the timing device through the additional
delay period when the compressor starts and for stopping the timing
device at the end of this additional delay period if the compressor
is still in operation, means for restarting the timing device when
the compressor is stopped, and means for stopping the timing device
when the equalizing period is substantially consumed if the
condition responsive device is not calling for refrigeration.
27. In a control system for a condition changing system having a
plurality of condition changing units, the combination of, a
plurality of switches connected to different condition changing
units, an electric motor driven actuating means arranged when
started from a first predetermined position to actuate said
switches in sequence thereby activating the condition changing
units in sequence, an operating condition responsive controller
responsive to the load on the system, means controlled by said
operating condition responsive controller for causing the motor
driven actuating means to run from the first position and activate
the condition changing units in sequence when the operating
condition responsive controller calls for condition change, means
controlled by said controller for stopping the actuating means in a
second predetermined position allowing continued operation of the
condition changing units, means for restarting the motor driven
actuator and actuating the switches to terminate operation of the
condition changing units when the operating condition responsive
controller becomes satisfied, means controlled by the condition
responsive controller for stopping the motor driven actuating means
at the first predetermined position, protective means including an
electromagnet for operating said switches to terminate operation of
the condition changing units independently of said motor driven
actuator means, a protective condition responsive controller in
circuit with both the electromagnet and the motor of said motor
driven actuating means, said protective controller acting to
terminate operation of the condition changing units and prevent
running of the actuating means when an undesirable condition occurs
in the system.
28. In a control system for a condition changing system, the
combination of a power circuit for said condition changing system,
control means for said power circuit, said control means including
an operating condition responsive device responsive to the load on
the system, a protective condition responsive means responsive to a
condition in the condition changing system, a timing device, and an
electromagnet, control circuit means including the operating
condition responsive device, the timing device and the
electromagnet for causing closure of said power circuit to start
the condition changer in response to a call for condition change,
and to open the power circuit in response to the operating
condition responsive device becoming satisfied, means in said
control circuit means whereby the timing device interposes a delay
between opening and closure of said power circuit, means in the
control circuit means to start the timing device when the operating
condition responsive device becomes satisfied if the protective
condition responsive device indicates a satisfactory condition in
the system, means in the control circuit means whereby said
protective condition responsive means operates the electromagnet to
open the power circuit independently of the operating condition
responsive device in response to an unfavorable condition in the
system, and means in the control circuit means to render the timing
device inoperative to begin a timing cycle as long as the condition
is unfavorable and render the timing device operable when the
condition becomes favorable, whereby the duration of the
unfavorable condition is added to the delay provided by the timing
device.
29. In a control circuit for a condition changing system including
a condition changer and fluid moving means associated therewith,
the combination of, a first power circuit for the condition
changer, a second power circuit for the fluid moving means, control
circuit means for the power circuits including an operating
condition responsive device responsive to the load on the system, a
protective condition responsive means responsive to a condition in
the condition changing system, and a timing device, said control
circuit means being arranged to close both power circuits to start
the condition changer and fluid moving means in response to a call
for condition change by the first condition responsive device and
to open the first power circuit to stop the condition changer in
response to said first condition responsive device becoming
satisfied, the timing device being arranged to control the second
power circuit to maintain it closed for operating the fluid moving
means a period of time after the condition changer is stopped,
control circuit means arranged to start the timing device when the
operating condition responsive device becomes satisfied if the
protective condition responsive device indicates a satisfactory
condition in the system, the protective condition responsive means
being arranged to cause opening of the first power circuit to stop
the condition changer, and to prevent the timing device from
operating in response to an unfavorable condition, whereby the
fluid moving means is maintained in operation as long as the
unfavorable condition exists.
30. The combination set forth in claim 29 in which the timing
device is also arranged to interpose a delay between stopping and
restarting of the condition changer.
31. In a control system for a condition changer, a condition
responsive device, a power circuit for the condition changer, a
control system for the power circuit including said condition
responsive device, a timing device and an electromagnet, means
whereby said timing device causes closure of the power circuit at
the command of the condition responsive device, and the
electromagnet causes opening of the power circuit independently of
the timing device when said electromagnet is deenergized, means
including a condition responsive device and circuit means
connecting said condition responsive device and electromagnet and
arranged to deenergize the same in response to an unfavorable
condition associated with the condition changer, switching means
actuated by said timing device also in circuit with the
electromagnet, said switching means being connected and arranged to
deenergize said electromagnet independently of said second
condition responsive device during periods when the power circuit
is open, and means whereby said timing device operates the
switching means to energize the electromagnet for allowing
continued closure of the power circuit under the command of the
first condition responsive means when the second condition
responsive means indicate a favorable condition.
32. In a motor driven switching mechanism, a motor, a cam shaft
driven by said motor, said cam shaft carrying a plurality of cams,
a plurality of switches operated from one contact position to
another by said cams, said cams being arranged to operate said
switches in sequence, starting from a predetermined angular
starting point of the cam shaft, means other than the cam shaft for
returning at least one of the switches to said one position,
mechanical interlocking means between said switches, said
mechanical interlocking means being arranged to prevent one of said
switches from being operated to its other contact position if a
switch ahead of it is not in its other contact position, whereby
the cam shaft must return to the starting position before said one
switch can be actuated to its other contact position.
33. The combination set forth in claim 32 in which the switches are
provided with separate control elements having active and inactive
positions and arranged to require the control element of a given
switch to be in active position in order for such switch to be in
its other contact position, the mechanical interlocking means
extending between said control elements.
34. The combination set forth in claim 33, in which the control
elements are latches which must be in latching position in order
for the corresponding switch to assume its other contact
position.
35. In a control system for a condition changer having a plurality
of condition changing units, the combination of, a plurality of
switches connected to different condition changing units, electric
actuating means for actuating said switches, an operating condition
responsive controller, means controlled by said operating condition
responsive controller for causing said electric actuating means to
operate said switches to start the condition changing units in
response to call for condition change, said electric actuating
means being arranged to stop said condition changing units in
sequence in response to the condition responsive controller
becoming satisfied, and protective means including an electromagnet
arranged to actuate said switches simultaneously to stop operation
of said condition changers, said electromagnet being operated in
response to a malfunction and actuating said switches independently
of said electric actuating means.
Description
This invention relates in general to automatic controls and control
systems, and more particularly to timing controls for use in
refrigeration systems having multiple compressors; electric heating
systems having multiple heating banks, machine tools, etc. having a
plurality of motors to be started.
In the refrigeration and air conditioning industry it has become
common to build up a system using a number of smaller compressors
instead of one large one. Such compressors usually take 5 or more
times the current to start as to run. By starting the compressors
in sequence and allowing each to come up to speed before the next
compressor is started, the power requirements for getting the
system into operation are greatly reduced. This reduces the cost of
the power supply and also avoids objectionable light dimming when
the system is started up.
In the electric heating field, it is becoming common to use a
central system having a number of electric heater banks drawing
approximately 5 kw. each. These heater banks are controlled by a
room thermostat which turns them on in response to call for heat
and turns them off when the requirement is satisfied. Due to the
heavy current consumption of the heater banks, turning them on and
off simultaneously would cause objectionable sudden decreases and
increases of light level. It is therefore desirable to bring on the
heater banks one at a time spaced far enough apart so that the
human eye adjusts to the preceeding dimming effect before the next
dimming effect occurs. The same sequence operation in deenergizing
the heater banks is also desirable but is not as important.
The primary object of the present invention is to provide a simple
and compact timing device which is in effect a self-contained
control system for sequence starting and/or stopping of a plurality
of condition changing units such as electric heaters, motors, etc.
A further object of the invention is the provision of a sequence
control unit in which the load switches are closed in sequence by a
timing mechanism and in which these same switches can be instantly
opened in the event of power interruption or a malfunction in the
system being controlled. A further object is the provision of a
device of this type in which the timing mechanism must recycle back
to the starting point before any of the load switches will
reclose.
A further object of the invention is to protect the compressors or
compressor of a refrigeration system by interposing a delay between
the stopping and restarting of a compressor on normal operation
which is sufficient to provide pressure equalization in the system
so that the compressor is never started under a heavy load.
A further object of the invention is to provide a substantially
longer delay between the stopping of the compressor and restarting
if the stopping of the compressor was occasioned by a malfunction
in the system.
Other objects of the invention will appear as this description
proceeds.
For a full disclosure of the invention, reference is made to the
following detailed description and to the accompanying drawings in
which:
FIG. 1 is an elevation with the cover removed showing the preferred
form of multiple switch sequence control mechanism;
FIG. 2 is a top sectional view taken on line 2-2 of FIG. 1;
FIG. 3 is an end sectional view taken on line 3-3 of FIG. 1 and
showing a load switch in open position;
FIG. 4 is an enlarged fragmentary view of a portion of FIG. 3
showing the switch blades riding the cam with the contacts in open
position;
FIG. 5 is a sectional view taken on line 5-5 of FIG. 4;
FIG. 6 is a view similar to FIG. 3, but showing the solenoid
energized and the load switch in closed position;
FIG. 7 is a sectional view taken on Line 7-7 of FIG. 1 and showing
the timer motor switch in closed positions;
FIG. 8 is a view similar to FIG. 7 but showing the motor switch in
open position at the end of a timing cycle;
FIG. 9 is a perspective fragmentary view showing the cascade
latching mechanism in which the release of one latch causes the
release of the next latch;
FIG. 10 is a schematic view showing the sequence switch operation
by the cams on the cam shaft, and the latches on the latch
shaft;
FIG. 10a is a fragmentary showing an alternative motor control
switch for the sequence controller of FIG. 10.
FIG. 11 is a fragmentary view showing a modification in which an
elongated solenoid lever serves to release all of the latches
simultaneously;
FIG. 12 is a schematic wiring diagram showing a preferred
application of the sequence controller to a refrigeration control
system in which a number of separate compressors are brought into
operation in sequence;
FIG. 13 is a schematic wiring diagram showing the application of
the controller to a central electric heating system in which a
number of heater banks are energized in sequence;
FIGS. 14, 15 and 16 show a modified form of cycling switch for the
timer motor for use in refrigeration systems where a positive
pressure equalization period is provided between the stopping and
restarting of the compressors;
FIGS. 17, 18 and 19 are schematic wiring diagrams showing a
refrigeration control system embodying the switch shown in FIGS.
10a, 14, 15 and 16 and the positions assumed by the switches at
different portions of the refrigeration control cycle;
FIG. 20 is a view similar to FIG. 3, but showing a modified form of
the invention in which the switches are opened in sequence instead
of simultaneously;
FIG. 21 is a fragmentary top view of FIG. 20, showing the double
cam and latch construction;
FIGS. 22 and 23 are fragmentary views showing the construction and
operation of Switch T-3b used in schematic FIGS. 25 and 28;
FIG. 24 is a detailed view of the switch T-1b also used in the
schematic FIGS. 25 and 28;
FIG. 25 is a schematic view showing the cam and switch arrangement
of the sequence controller applied to cascade on-cascade off
operation;
FIG. 26 shows a modified form of switch construction in which
switches T-1b and T-3b are operated simultaneously by a single
cam;
FIG. 27 is a view taken on Line 27-27 of FIG. 26;
FIG. 28 is a schematic wiring diagram showing the invention applied
to a cascade on-cascade off electric heat control in which banks of
electric heaters are energized in sequence on call for heat and
deenergized in sequence when the thermostat is satisfied;
FIG. 29 is a fragmentary schematic wiring diagram showing the
position of the timer motor switches when the timer is running;
FIG. 30 is a similar view showing the timer motor switches when the
timer is stopped with the load switches closed;
FIG. 31 is a schematic wiring diagram showing the application of
the cascade on-cascade off controller to a refrigeration system in
which the compressors are brought on in sequence and also turned
off in sequence;
FIG. 32 is a switch sequence chart showing the embodiment of the
invention illustrated in FIGS. 1 to 10 applied to refrigeration
control using the wiring diagram of FIG. 12, and showing operation
on a normal cycle;
FIG. 33 is the same chart as shown in FIG. 32, but showing the
operation which occurs in the event of a short cycle;
FIG. 34 is a sequence chart showing the same embodiment of the
invention applied to electric heating control using the wiring
diagram of FIG. 12;
FIG. 35 is a switch operating chart of the sequence controller
applied to refrigeration control but using the motor control switch
illustrated in FIGS. 14 to 19, inclusive, this chart showing
operation on a normal cycle;
FIG. 36 is a view similar to FIG. 35, but showing the difference in
operation that occurs in the event of a short cycle;
FIG. 37 is a switch operation chart showing the cascade on-cascade
off embodiment of the invention as applied to electric heating
control, this chart showing the switch operation occurring on a
normal cycle;
FIG. 38 is the same chart shown in FIG. 37, but showing the
operation occurring in the event of termination of a cycle by the
limit control or by a power interruption;
FIG. 39 is a switch operation chart of the cascade on-cascade off
embodiment of the invention as applied to refrigeration control,
this chart showing the switch operation as occurs on a normal
cycle;
FIG. 40 is the same chart as shown in FIG. 39 but showing the
switch operation as occurs on a short cycle.
FIGURES 1 TO 10 INCLUSIVE
Referring to FIGS. 1 and 2, reference character 1 indicates
generally a timer housing formed of base member 2 and a top member
3. The base member 2 is generally l-shaped and includes an upwardly
extending portion 4, forming one end wall of the enclosure 1. The
top member 3 is generally Z-shaped having a vertical portion 5,
forming the other end wall of the enclosure. The member 3 also
includes a horizontal lower portion 6 which is secured to the base
member 2. The upper end of the base member 2 is in-turned as at 7
and supports the top member 3. Secured between the housing members
2 and 3 is a terminal panel 10, carrying load switches 11, 12 and
13, and a timer motor control switch 14. The panel 10 may also be
used for supporting various terminals required in the control
system circuits as hereinafter described.
As shown in FIG. 2, a cam shaft 15 is rotatably supported between
the housing members 4 and 5. This cam shaft 15 carries a gear 16
which is driven by a timer motor generally indicated as 17. The cam
shaft 15 also carries cams 18, 19, 20 and 21.
The load switches 11, 12 and 13 are identical, each consisting of
an upper switch blade 22 and a lower switch blade 23 (FIG. 3). The
upper switch blade 22 at its left-hand end is attached to a
terminal bracket 24 which is in turn attached to the switch panel
10. The lower switch blade is similarly mounted to a terminal 25
also secured to the panel. The switch blade 23 is preferably of
channel construction as disclosed in my U.S. Pat. No. 2,786,907
dated Mar. 26, 1967. As shown more clearly in FIG. 4, the switch
blade 23 is provided with an opening 26 into which the cam 18
extends. The switch blade 23 is also formed with an internal cam
follower surface 27 riding the cam 18. The upper switch blade 22
may be of the same construction and includes a cam follower bracket
28 secured to the blade 22 by means of the contact rivet 30. As
shown in FIGS. 4 and 5, the bracket 28 includes a downwardly
extending section 31 which at its lower end is formed inwardly at
32 to provide a cam follower surface. The lower switch blade 23
also carries a contact 33 and is provided with an extension 34
which is selectively supported or released by a latch member 35
(FIG. 3) pivoted on a latch shaft 36. This shaft is supported
between the housing upright members 4 and 5. The latch shaft 36
also carries latches 37, 38 and 39 for switches 12, 13 and 14
respectively. Switch blades 22 and 23 are both biased downwardly
toward the cam or activator 18.
The latch 35 is provided with an upper latching surface 40 which is
adapted to support the extension 34 of the lower switch blade 23
when the latch is engaged (See FIG. 6). This latch is also provided
with a stop surface 41 which engages the end of the switch blade
and limits the inward motion of the latch. As shown more clearly in
FIG. 9, the latches 35, 37 and 38 are of identical construction and
are preferably molded and include driving members 42 and driven
members 43. The driving members 42 and driven members 43 extend
toward each other and the driving member 42 of one latch is located
behind the driven member 43 of the next latch. It will be apparent
that when the latch 35 is rotated clockwise in latch releasing
direction, its driving member 42 will engage the driven member 43
of latch 37 and move latch 37 in releasing direction. This movement
of latch 37 will release latch 38 and this action will continue
until all of the latches in a given unit are released. In addition
to the driving and driven surfaces 42 and 43, the latches are each
provided with a camming surface 44, below the latching surface 43.
This camming surface on the latch causes the downward bias of the
switch blade to apply power to the latch in releasing direction
after the latch has released its switch blade. Thus the force
released when the latch releases the switch blade is used to drive
the latch further in releasing direction and this force thus serves
to release the next latch.
The latch 35 is also provided with an additional latch releasing
surface 45 for release by the solenoid or electromagnet 46. As
shown more clearly in FIG. 9, the latches are molded and are formed
with integral bearing numbers 47 and 48 which also serve as spacers
for the latches on the latch shaft 36. Each latch is provided with
a latch spring 49. These springs are of the torsion type and are
carried by the bearing numbers 48 of each latch. One end of each
spring bears against the rear of the driving member 42 and the
other end of each spring bears upon a spring shaft 50 which is
mounted between the housing members 4 and 5 and is generally
parallel with the latch shaft 36. Thus each latch is biased in a
counterclockwise direction.
The releasing surface 45 of the latch 35 is adapted to be engaged
by one leg 51 of a bell crank lever, the other leg 52 of which is
activated by the plunger 53 of solenoid 46. This solenoid 46 is
mounted on the end wall 4 of the enclosure by spacers 53 which
serve to line up the solenoid lever with the latch 35. The solenoid
lever is preferably molded including hub portion 55 carried by a
stud 56 mounted on the housing member 4. A torsion type biasing
spring 57 surrounds the hub or bearing member 55. One leg of this
biasing spring rests on the spring shaft 50, and the other bears
against a stud 58 forming a part of the solenoid lever. It will be
apparent that the spring 57 serves to bias the solenoid lever in a
counterclockwise direction withdrawing the plunger 53 from the
solenoid proper.
The construction of the timer motor switch mechanism is shown in
FIGS. 7 and 8. This switch, generally indicated as 14, includes a
lower switch blade 60 of channel shaped configuration which rides
the cam 21. The upper blade 61 is of like configuration but is
longer providing a latching portion 62. This latching portion 62 of
the switch blade is arranged to be supported by the latch 39 also
carried on the latch shaft 36. This latch includes a driven surface
63 and a latching surface 64. This latch is also provided with a
stop surface 65. Latch 39 is similar in configuration to latch 34
but is longer as its function is to support the upper switch blade
instead of the lower switch blade. The switch blades 60 and 61
carry contacts 66 and 67 respectively. These switch blades are both
biased downwardly toward the cam 21.
OPERATION OF FIGURES 1 TO 10 INCLUSIVE
With the parts in the position shown in FIGS. 3, 7 and 10, the
control is in the off or standby position. Latches 35, 37 and 38
have been released thus causing the lower switches 11, 12 and 13 to
be open. The latch 39 is also released which causes the timer motor
control switch 14 to be closed. Load switches 11, 12 and 13 are
open due to the cam follower portions of each blade (FIG. 4) riding
the main section 67 of each cam. This main cam surface includes the
generally circular low portion 68 and a rise portion 69. The parts
are proportioned so that as long as both blades ride upon this main
cam surface, the load contacts 30 and 33 remain open.
It will be understood that the timer motor switch 14 is wired in
series with the timer motor. Thus when power is applied to the
timer motor circuit and to the solenoid, the solenoid is energized
and the timer motor is also energized. This will cause the cam
shaft assembly or actuating means to be rotated in a
counterclockwise direction as seen in FIGS. 3, 7 and 10. As shown
in FIG. 10, the cam 18 for switch 11 is in advance relative to the
other cams on the shaft. As the cam shaft is rotated in a clockwise
direction, the cam follower portions of the switch blades both ride
off the circular low portion 68 of the cam 18 and up the slope 69
of the main cam surface. The contacts 30 and 31 remain separated at
this time. As the switch blades continue the rising motion, the
latch 35 is allowed to rotate counterclockwise by the camming
surface 44. Eventually the end portion 34 of the switch blade 23
will clear the camming portion 44 of the latch, allowing the latch
to rotate to bring the latching surface 40 beneath the end portion
34 of the switch blade. On continued rotation of the cam shaft
assembly in the counterclockwise direction, the cam follower
surface 27 of the lower switch blade will ride down the sloping
portion 70 of cam 18 and the latching portion 34 will rest on the
latch surface 40 of latch 35. On continued rotation of the cam
shaft assembly, the follower portion 32 of the upper switch blade
22 will start riding down the incline portion 70 allowing contact
30 to slowly approach contact 31. Shortly before the contacts
engage, the cam follower surface 32 of switch blade 22 drops off at
the drop off section 71 of cam 18, allowing the contacts to engage
with snap action. This arrangement in which the upper contact 30 is
brought slowly into near engagement with the contact 31 and then
dropped off a short distance for contact engagement avoids contact
bounce. This increases the current handling capacity of the switch
which is desirable in heavy current handling obligations such as
electric heating.
It should be noted that latch 35 was allowed to assume latching
position due to the solenoid 46 having been energized. This action
rotated the solenoid bell crank lever clockwise against the action
of its biasing spring, causing the latch releasing portion 51 to be
clear of the releasing surface 45 of latch 35. It should also be
noted that due to the latch being in engaging position as shown in
FIG. 6, the driving surface 42 (FIG. 9) is now out of the path of
the driven surface 43 of the adjacent latch 37. As the cam shaft
assembly continues its counterclockwise rotation, the switch 12 is
actuated in the same manner as described for switch 11. The latch
37 comes into place and the switch blades are lowered causing the
contacts of switch 12 to engage. Later, on continued clockwise
rotation of the cam shaft assembly, switch 13 is closed in the same
manner.
During this time switch blade 60 of the timer motor switch 14 has
been gradually rising due to the gradual rising surface of the cam
21. Due to the engagement of the contacts 66 and 67, the upper
motor switch blade 61 rises and its latching end 62 rises above the
latching surface 64 of latch 39. This permits the latch 39 to
rotate counterclockwise into latching engagement with blade 61. At
the end of the cycle, the cam follower portion of the lower switch
blade 60 drops off the drop off surface of cam 21. The end 62 of
switch blade 61 is maintained in its upper position by the latch 36
and the switch assumes the position shown in FIG. 8 in which the
contacts 66 and 67 are disengaged. As the switch 14 is in series
with the timing motor means 17, it serves as a stopping means for
stopping the timer motor and the actuating means consisting of the
cam shaft assembly.
From the foregoing, it will be apparent that when the timer motor
circuit and the solenoid are energized, the solenoid allows the
latches to assume operative position and the timer motor is
energized for causing the load switches 11, 12 and 13 to close in
sequence. After these load switches have been closed the motor
switch 14 opens which stops the motor, allowing the load switches
to remain closed indefinitely.
The load switches will remain closed and the motor switch open
until the solenoid 46 is deenergized either by a control switch or
by a power interruption. When the solenoid is deenergized, its bell
crank lever rotates counterclockwise under the influence of biasing
spring 57. Portion 51 of the bell crank lever engages releasing
portion 45 of the latch 35 rotating this latch in a clockwise
direction causing the end 34 of switch blade 23 to ride off the
latching surface 40 onto the camming surface 44 of the latch. As
the switch blade 23 is biased downwardly it moves down and its
engagement with the camming surface 44 of the latch causes
continued clockwise rotation of the latch. After the switch blade
starts riding down the camming surface on the latch, the driving
portion 42 of the latch 35 engages the driven portion 43 of the
adjacent latch 37. This releases latch 37 which in turn releases
latch 38 which then releases the motor switch latch 39. Due to the
releasing of latches 35, 37 and 38, both switch blades of switches
11, 12 and 13 once again ride the main camming surfaces of their
respective cams. The switch blades thus assume the positions shown
in FIGS. 3 and 4 in which the contacts are open. Due to the latch
39 of motor switch 14 being released, contacts 66 and 67 of the
motor switch 14 are reclosed which will permit resumption of the
timing means when power is reapplied to the timing motor 17.
It should be noted that unless the solenoid is energized during the
timing cycle, none of the load switches will ever close. Thus if
power is applied to the timing motor but not to the solenoid, the
timer will run and drive the cam shaft assembly in a
counterclockwise direction as previously described. However, due to
the solenoid being deenergized, the initial latch 35 is in released
position and can never assume latching position. Due to the
arrangement of the driving and driven surfaces 42 and 43 between
the latches, none of the latches can ever move into engaging
position. Thus, if the cam shaft assembly rotates it simply raises
and lowers the switch blades without engagement of the
contacts.
It should also be noted that with the interlocking relationship of
the latches, load switch 12 can never close unless the latch 35 of
load switch 11 is already in latching position. Similarly, load
switch 13 can never close unless the latch 37 of load switch 12 is
already closed. In the same manner the motor switch 14 can never
open unless the latch 38 of load switch 13 is in latching position.
The only switch that can close independently of the other switches
is the first operated load switch 11. If a power interruption
should occur after the load switch 11 has closed, the solenoid will
drop out and immediately release latch 35 causing load switch 11 to
immediately reopen. The latch 35 in being released prevents latches
37, 38 and 39 from ever moving into engaging position. Thus when
power is interrupted to the solenoid, the timer cam shaft assembly
must make a complete revolution and reclose the load switch 11
before the other load switches 12 and 13 can close. In other words,
a power interruption during a cycle opens all of the load switches
and the timer will recycle on resumption of power and reclose the
switches in the predetermined order.
In applications where this complete recycling feature is not
desirable, the arrangement shown in FIG. 11 may be used. Here, the
driving and driven surfaces 42 and 43 are omitted from the latches.
Instead an elongated solenoid lever 75 is pivoted between the
enclosure ends 4 and 5 and includes a lever portion 76 operated by
the solenoid 46A. The lever 75 is arranged to actuate the releasing
portions 45 of the latches simultaneously. With this arrangement,
if a power interruption occurs during a cycle, the switches then
closed will immediately reopen. However, on resumption of power,
succeeding switches may be closed even though the switches ahead
are still open. This arrangement also has the disadvantage of
requiring a larger solenoid as it must be powerful enough to
release the latches simultaneously. In the arrangement shown in
FIG. 9, the only power required from the solenoid is enough to
release the initial latch as the force then released is used to
release the next latch.
REFRIGERATION SEQUENCE CONTROL -- FIGURE 12
FIG. 12 shows a schematic wiring diagram for applying my sequence
timing mechanism to a refrigeration system having multiple
compressors. In this circuit, power is supplied to the system by
line wires 80 and 81. A high-low pressure cutout 82 controls the
power to the primary 83 of a low voltage transformer having a
secondary 84. This secondary supplies low voltage power to the
thermostat 85 which is connected to the timer solenoid 86 and to
the timer motor switch T-1 which controls the timer motor 87. It
will be understood that the solenoid in this circuit corresponds to
the solenoid 46 in the structural figures. Switch T-1 corresponds
to the motor switch 14 and the timer motor 87 corresponds to the
motor 17.
The high-low pressure cutout 82 also supplies power to the timer
load switches T-2, T-3 and T-4 which correspond to the timer
structural switches 11, 12 and 13 respectively. Switches T-2, T-3
and T-4 control compressor contacted coils C-1, C-2 and C-3
respectively. These coils in turn control double pole contacts
C-1a, C-2a and C-3a which control compressors 88, 89 and 90
respectively. The contactor C-1 may also control a fan or blower 91
which supplies air to the evaporator or condenser or both of the
refrigeration system, as well understood in the art.
In refrigeration control, it is preferable to arrange the cams and
the timer gearing to provide a time cycle as shown in FIGS. 32 and
33. An overall cycle of approximately 5 minutes is shown in FIG. 32
with switches T-2, T-3 and T-4 closing in sequence. Switch T-2 may
close 10 seconds after the start of the cycle. Switch T-3 may close
10 seconds later and switch T-4 closes another 10 seconds later. In
operation, assuming the high-low pressure cutout 82 is closed, the
thermostat 85 on call for cooling will energize the timer solenoid
86 and also will energize the timer motor 87 through the timer
motor switch T-1 which is now closed. The timer will run for 10
seconds closing switch T-2 which energizes the contactor coil C-1
which in turn energizes the compressor motor 88 and the blower
motor 91. Ten seconds later timer switch T-3 closes, energizing the
contactor C-2 which in turn energizes the compressor motor 89. Ten
seconds later, the switch T-4 closes, energizing the contactor coil
C-3 which energizes the compressor 90. The timer motor switch T-1
will remain closed for the full 5-minute cycle. When it reaches the
end of the cycle, this switch will open, stopping the timer with
the load switches T-2, T-3 and T-4 closed. Thus, on call for
cooling in normal operation, the thermostat closes the timer to
bring on the compressors in sequence and then run for an additional
period of approximately 4 minutes 30 seconds. At this time, the
timer motor stops and the three compressors will operate until
terminated by a power interruption, by opening of the high pressure
cutout 82, or by opening of the thermostat 85. When this happens,
the solenoid drops out, causing an immediate opening of the load
switches T-2, T-3 and T-4 and reclosing of the timer motor switch
T-1. The timer motor does not run at this time as its power is
broken elsewhere. The compressors immediately stop and will remain
out of operation until restarted in sequence on a new cycle.
FIG. 33 charts the switch operation occurring if the refrigeration
system should short cycle by opening of switch 82 after all three
compressors are in operation. If the short cycle occurs, for
example 10 seconds after the third compressor has started, a total
of 40 seconds of the overall cycle will have elapsed. This means
that when power is restored to the control circuit by closure of
the high-low pressure cutout, the timer must run through the
balance of the 5-minute cycle to get to the starting point. This,
in the illustration, would come out to 4 minutes 20 seconds. In
addition, the timer must run the 10-second delay period before
closure of switch T-2 for starting the first compressor. This means
that an overall delay of 4 minutes 30 seconds is assured before
restart of the first compressor. To this delay provided by the
timer is added the time that the high-low pressure switch 82 is
open. Thus a substantial delay may be provided before restart of a
compressor in the event of a short cycle. This gives a certain
amount of protection against compressor burnout from short
cycling.
In the event of a short cycle or power interruption during the
period that the compressors are being started in sequence, any
compressor that has been started will immediately be deenergized.
When power is reapplied to the timer, it will run back to the
starting point before any of the load switches can reclose. Thus
the timer must always recycle to the starting point and restart the
compressors in the proper sequence.
CASCADE ON ELECTRIC HEAT CONTROL --FIGURE 13
FIG. 13 shows the application of the timing mechanism disclosed in
FIGS. 1 to 10 inclusive to control of the heating banks of a
central electric space heating system. Here, the primary of the low
voltage transformer is connected in series with a high limit
temperature control responsive to the temperature in the bonnet of
the electric heating furnace. The low voltage room thermostat
controls the timer solenoid and also controls the timer motor
through the timer motor switch T-1. Switches T-2, T-3 and T-4 of
the timer are connected respectively to electric heater banks H-1,
H-2 and H-3. In this illustration, the blower 92 for the warm air
heating furnace is controlled by a thermostat 93 responsive to the
bonnet temperature of the warm air heating furnace.
In the electric heating application, there is no need for a
prolonged cycle as in the refrigeration control application
previously described. A recommended sequence chart is shown in FIG.
34. Here, the timer is geared for an overall cycle of 60 seconds
and the load switches T-1, T-2 and T-3 are arranged to close at
15-second intervals. This is provided by proper positioning of the
cams on the timer cam shaft.
In this illustration, when the room thermostat 94 calls for heat,
it energizes the timer solenoid and also energizes the timer motor
through the switch T-1. The timer motor will run for 15 seconds at
which time switch T-2 closes. This will energize the heater bank
H-1. Fifteen seconds later, timer switch T-3 closes energizing
heater bank H-2. Fifteen seconds after switch T-3 closes (45
seconds from start), switch T-4 closes, energizing the heater bank
H-3. The timer will continue to run for a 15-second overtravel
period at which time the switch T-1 opens, stopping the timer motor
with the load switches T-2, T-3 and T-4 all closed. When the air
temperature in the warm air furnace rises to the cut-in point of
the bonnet thermostat 93, the blower 92 will be started.
The timer will remain in this ON position until either the room
thermostat 94 or the high limit thermostat 91 opens its circuit.
This will immediately deenergize the timer solenoid causing the
load switches T-2, T-3 and T-4 to open and the timer motor switch
T-1 to reclose. This same action of opening the load switches and
reclosing the timer motor switch will also occur in the event of a
power interruption.
If power should be interrupted during the period that the timer is
closing the load switches in sequence, any switch already closed
will reopen and the timer must return to the starting point and
bring on the heaters in the specified sequence.
FIGURES 14 TO 19 INCLUSIVE
REFRIGERATION CONTROL SYSTEM PROVIDING A
POSITIVE PRESSURE EQUALIZATION DELAY ON A NORMAL CYCLE
WITH ADDED DELAY IN EVENT OF A SHORT CYCLE
In the embodiment of the invention described in FIGS. 12, 32 and
33, a minimum delay of 5 minutes is provided between successive
restarts of the compressors. This provides protection against short
cycling. However, it does not provide a positive delay between the
stopping and restarting of the compressors which insures pressure
equalization in the refrigeration system. On a normal cycle where
the compressors are in operation for over 5 minutes, the timer is
back at the starting point when the compressors stop and thus the
first compressor can be restarted in a period as short as 10
seconds from the time it stopped. An improved system is shown in
FIGS. 14 to 19 inclusive and the sequence is charted in FIGS. 35
and 36.
In this embodiment of the invention the timer mechanism including
the switches 11, 12 and 13 is exactly as shown in FIGS. 1 to 10
inclusive. The only change is in the control of the timer motor. A
special double throw switch 100 as shown in FIGS. 10a, 14, 15 and
16 is substituted in place of the timer motor switch 14 in the
schematic diagram shown in FIG. 10. The switch 100 (FIG. 14)
consists of an upper switch blade 101, a middle switch blade 102,
and a lower switch blade 103. This lower switch blade 103 extends
across the cam 104 and includes an internal cam follower surface
105. In this embodiment of the invention only the lower switch
blade 103 rides the cam 104. The upper switch blades 101 and 102
are controlled by a latch 106. This latch is pivoted on the latch
shaft 36 along with the load switch latches 35, 37 and 38. This
latch is provided with three latching surfaces 107, 108 and 109.
The latch 106 is also provided with a driven surface 110, adapted
to be engaged by the driving surface 42 of the adjacent load switch
latch. Latch 106 also is formed with an operating lever portion 111
extending toward the cam shaft 15. This lever arm 111 is adapted to
be engaged and operated by a cam 112 which is mounted adjacent the
cam 104 and in fixed angular relationship therewith. FIG. 14 shows
the relationship of the parts in the "Standby Postion" where a new
cycle is ready to be started on call for cooling by the room
thermostat or other condition responsive device. Here the contacts
between the top blade 101 and middle blade 102 (T-1a) are closed.
Also, the contacts between the middle blade 102 and the lower blade
103 (T-2a) are open. The middle blade 102 is supported on the
intermediate latch surface 108 of latch 106. Switch blade 103 has
just dropped off the dropoff section of the cam 104. The switch
blade 101 is supported by the closed contacts T-1a and a space
exists between this switch blade and the upper latching surface 109
of the latch 106.
FIG. 17 shows the schematic wiring diagram for the refrigeration
control system embodying the timer motor switch 100. Power is
supplied to the system by line wires 114 and 115. A combination
high-low pressure cutout 116 controls the power supply to the
primary 117 of a low voltage transformer having a secondary 118. A
room thermostat 119 controls the power supply to the timer solenoid
120 and also to the upper switch blade 101 of the timer motor
switch 100. The middle switch blade 102 is connected to the timer
motor 121. The lower switch blade 103 is connected directly to the
transformer secondary 118 and serves to shunt the thermostat
119.
OPERATION OF FIGURES 14 TO 19 INCLUSIVE
With the parts in the positions shown in FIGS. 14 and 17, the load
switches T-3a, T-4a and T-5a (corresponding to switches 11, 12 and
13 of FIG. 10) are open. Contacts T-1a of timer motor switch 100
are closed and thus the timer motor 121 is in circuit with the room
thermostat 119. This thermostat in the Standby Position is open and
thus the timer motor 121 and the solenoid 120 are deenergized.
Assuming the pressures in the refrigeration system are
satisfactory, causing the high-low pressure switch 116 to be
closed, the thermostat 119 on cal for cooling will directly
energize the timer solenoid 120 and will simultaneously energize
the timer motor 121 through contacts T-1a of the motor switch 100.
The timer will now begin functioning as charted in FIG. 35. Ten
seconds from start, switch T-3a will close, energizing the
compressor contactor C-1 causing the first compressor of the
refrigeration system to start. Ten seconds later, switch T-4a
closes energizing compressor contactor C-2 causing the second
compressor to start. Ten seconds later switch T-5a closes
energizing the compressor contactor C-3 causing the third
compressor to start. This completes the initial delay period of 30
seconds. Switch T-1a will remain closed for an additional 2 minutes
30 seconds (3 minutes from start). At this point switch 100 assumes
the Run position shown in FIGS. 15 and 18. As shown in FIG. 15, the
operating lever portion 111 of the latch 106 has been lifted by the
cam 112 on the cam shaft 15. This has caused clockwise rotation of
the latch 106 to the point at which the middle switch blade 102 has
dropped from the latching surface 108 to the lower latching surface
107. The upper switch blade 101 has dropped to the upper latching
surface 109 and is supported thereby. With this position of the
parts, switches T-1a and T-2a are both open. Thus the timer motor
stops with the load switches T-3a, T-4a and T-5a closed causing
operation of all three compressors.
On a normal cycle this condition will prevail until the room
thermostat 119 becomes satisfied. When this occurs, the circuit to
the timer solenoid 120 is broken. This releases the latch 35 which
in turn releases latches 37, 38 and 106. The compressor motors are
immediately deenergized and the timer motor switch assumes the
position shown in FIGS. 16 and 19. Release of the latch 106 at this
point is caused by engagement of the driving surface 42 of latch 38
with the driven surface 110 of latch 106. The clockwise rotation of
latch 106 removes the supporting surface 109 from under the upper
switch blade 101. This same motion also removes the lower latching
surface 107 from the middle switch blade 102. As all of the switch
blades are biased toward the cam 104, the middle switch blade 102
drops to engage switch T-2a and the top switch blade 101 drops to
engage switch T-1a. As shown in FIG. 19, closure of the switch T-2a
establishes a new circuit to the timer motor 121 which is
independent of the thermostat 119. Thus when the thermostat becomes
satisfied, switches T-3a, T-4a and T-5a open and switches T-1a and
T-2a close. The compressors are thus deactivated and the timer
motor is restarted. The timing means will now run through the
minimum equalizing period of 5 minutes back to the Standby
Position. In this illustration it involves 8 minutes running time
from one Standby position to the next.
As the timer approaches the Standby position, the cam follower
surface 105 of switch blade 103 nears the topmost point of the cam
104. This has raised the three switch blades to the point where the
latching surface 108 comes under the blade 102 and latching surface
109 is under the blade 101. When the timer arrives at the Standby
position, the cam follower surface 105 of switch blade 103 drops
off the dropoff portion of the cam 104 and assumes the position
shown in FIG. 14. The middle blade 102 drops to the latching
surface 108 and is supported thereby, this causing switch T-2a to
open. In this Standby position, switch T-1a remains closed due to a
space existing between this switch blade and the upper latching
surface 109.
If the room thermostat should call for cooling during the minimum
equalizing period, it will energize the solenoid 120 of the timer.
However, this will not affect any of the switches. The timing means
must first run through the minimum equalizing period to get to the
Standby position and then must run the additional 10 second delay
period before the first compressor is started.
From the foregoing description, it will be apparent that on a
normal operating cycle, this embodiment of the invention will
provide a minimum delay of 5 minutes 10 seconds between stopping of
the compressors and a restart. This insures an adequate time for
the pressures in the refrigeration system to equalize so that the
compressors are never started under heavy loads.
FIG. 36 charts the operation of the switches in the event of a
short cycle. Here on call for cooling, the thermostat energizes the
timer motor through switch T-1a. The load switches T-3a, T-4a and
T-5a close in sequence starting the compressors. However, something
associated with the refrigeration system is malfunctioning and the
high-low pressure cutout 116 responds by opening its switch for
example 40 seconds from the starting time. This breaks the circuit
to the transformer primary 119 and thus deenergizes the solenoid
120. This solenoid drops out immediately opening the load switches
to stop the compressors, and closing switch T-2a. The additional
delay now interposed before the compressors can restart is the
unused balance of the 2-minute 30-second "Short Cycle Adder." In
this illustration, the additional delay would amount to 2 minutes
20 seconds.
In addition to the additional delay imposed by the timer, there is
also a delay of variable duration provided by the opening of the
high-low pressure switch 116. It should be noted that switch 116 in
deenergizing the timer solenoid also breaks the power circuit to
the timer motor. The timer motor does not restart immediately on
closure of switch T-2a as occurs in the normal cycle charted in
FIG. 35. Instead the delay period provided by the timer does not
start until conditions within the refrigeration system have been
corrected to the point allowing reclosure of the high-low pressure
switch 116.
From the foregoing description, it will be apparent that the
control system shown in FIGS. 14 to 19 inclusive provides for
sequence starting of a plurality of compressors or condition
changing units in response to a call for condition change by the
device 119. On a normal cycle, the compressors are stopped
simultaneously and a delay is imposed by the timing means before
restart which is sufficient for allowing satisfactory pressure
equalization in the refrigeration system. In the event of a short
cycle, a longer delay before restart is provided. This longer delay
is the sum of the time that the high-low pressure switch is open
and the unused balance of the "Short Cycle Adder" provided by the
timing mechanism.
CASCADE ON-CASCADE OFF OPERATION-FIGURES 20 to 30 INCLUSIVE
The two embodiments of the invention previously described bring on
the condition changing units in sequence and turn them off
simultaneously when the requirement for condition change is
satisfied. This simultaneous Off operation in some cases can cause
an undesirable power surge making it preferable to deactivate the
condition changing units in sequence instead of simultaneously. The
present invention also provides for sequence off operation which
will now be described.
Referring to FIG. 20, the timer latch 135 for the load switch 11 is
provided with an inwardly extending arm 140 which is adapted to be
engaged by an "off" cam 141 which is mounted beside the "on" cam
118. The cam 118 is identical with the cam 15 of FIG. 3 and
operates the switch blades of the switch 11 in exactly the same
manner. As shown in FIG. 21, the cam 141 is mounted on the shaft
115 beside cam 118. The latch 135 is formed with the lever portion
140 offset so as to ride cam 141 and be clear of the cam 118.
Latches 135, 137 and 138 are of identical construction. The lever
portion 140 of latch 137 rides cam 142 located beside the cam 119
for switch 12. The lever portion 140 of latch 138 rides on cam 143
located beside the cam 120 for switch 13.
The present invention provides a system for controlling electric
heater banks in a central electric system in which the heater banks
are energized in sequence on call for heat and deenergized in
sequence when the call for heat is satisfied. The invention also
provides simultaneous shut down of all the heater banks in the
event the temperatures within the system become excessive such as
by a malfunction in the system.
This type of operation involves extra switches in the sequence
controller as shown in FIGS. 22, 23, 24 and 25. The schematic
wiring diagram showing the location of these switches in the
control circuit is shown in FIG. 28.
Referring to FIG. 25, switches 11, 12 and 13 are the same as shown
in FIGS. 20 and 21. These switches correspond to switches T-4b,
T-5b and T-6b in the wiring diagram of FIG. 28. In this embodiment
of the invention the timer motor must be stopped after the timing
mechanism has operated the load switches for activating the heater
banks. Also, the timer motor must be restarted when the controlling
thermostat becomes satisfied so as to deactivate the heater banks
in sequence. This is achieved by switches T-1b and T-2b shown in
FIG. 25 wired as shown in FIG. 28. Switch T-2b is identical in
construction to the load switch 11 shown in FIG. 3. Thus, the
contacts of switch T-2b are normally open, and are closed by the
conjoint action of cam 121-a and latch 139 at the proper point in
the timing cycle. This switch T-2b is immediately opened by release
of the latch 139 along with the other latches 135, 137 and 138.
The construction of switch T-3b is shown in FIGS. 22 and 23. This
switch consists of an upper switch blade 145 and a lower switch
blade 146 mounted on the switch panel 10 and riding cam 147 mounted
on the cam shaft 115 along with the other cams of the controller.
As shown in FIG. 22, the upper switch blade 145 has an internal cam
follower surface 148 and the lower switch blade has a similar cam
follower surface 149. Blade 145 carries a contact 150 cooperating
with a similar contact 151 carried by the lower blade 146. The cam
147 preferably has a uniform rise section 152 and a dropoff section
153. The edge of cam follower surface 149 is located on the cam
surface in advance of the edge of the surface 148. Normally, only
the lower cam follower surface 149 engages the cam and the contacts
150 and 151 are closed as shown in FIG. 23. These contacts support
the upper switch blade 145 so that the cam follower surface 148 at
this time does not engage the cam. When the cam 152 rotates to the
point where the dropoff 153 passes under the cam follower surface
149, the lower blade 146 drops to the lower cam surface. At the
same time contacts 150 and 151 separate and the upper cam follower
surface 148 now rests on the upper surface of the cam. On continued
rotation of cam 152, its dropoff section 153 will pass under the
upper cam follower surface 148 allowing the upper switch blade to
drop closing contacts 150 and 151. As shown in FIG. 28 this switch
T-3b is used for controlling the timer solenoid and also for
controlling the blower for the electric heating system.
The other timer motor control switch T-1b is similar in
construction and operation to switch T-3b as shown in FIG. 22.
However, this switch is of the double throw type including an
additional switch blade 156 carrying a contact 157 adapted to
engage a double contact 158 carried by the middle switch blade 159.
The lower switch blade 160 carries a contact 161 engageable with
contact 158 on blade 159. Blade 160 includes a lower cam follower
surface 162 and blade 159 carries an upper cam follower surface
163. All three switch blades are biased toward the cam and a spacer
164 causes the upper switch blade 156 to move in unison with the
lower switch blade 160. This spacer passes through a suitable
opening in the middle switch blade 159. FIG. 23 shows the switch
T-1b at the Standby position in the timing cycle. In this position,
the switch blade 160 has dropped off the dropoff portion 165 of cam
166. Contacts 161 and 158 are separated whereas upper contacts 157
and 158 are engaged. When the cam 166 rotates clockwise from the
Standby position, the dropoff portion 165 of the cam passes beneath
the follower portion 163 of the middle switch blade 159. This blade
now drops causing engagement of contacts 158 and 161 and
disengagement of contacts 157 and 158. At this time, the upper
switch blade 156 is supported by the spacer 164 and thus prevented
from following the dropping of middle blade 159. The timer will now
make almost a full revolution before the dropoff section of the cam
165 passes beneath the cam follower surface 162 of blade 160. At
this time blade 160 drops and the parts reassume the position shown
in FIG. 24.
Referring to FIG. 28, low voltage power is supplied to the timer
motor and room thermostat circuit by a 24 volt leakage type
transformer having a primary 170 and a secondary 171. The timer
motor 172 is connected to the common terminal of switch T-1b (blade
159 in FIG. 24). The room thermostat 173 is connected to one side
of the transformer primary and also to one terminal of switch T-2b.
This room thermostat 173 is also connected to contact 157 of switch
T-1b. It is important in this embodiment of the invention that the
transformer be of the leakage type in which the secondary 171 may
be short circuited without damage. This is for the reason that this
transformer is actually short circuited by the control system for
stopping the timer motor in the "Run" position. The operation of
the complete cascade on-cascade off system will now be
described.
OPERATION OF FIGS. 20 TO 30 INCLUSIVE CASCADE ON-CASCADE OFF
ELECTRIC HEATER CONTROL
Referring to FIGS. 25 and 28, the switches are all shown in the
positions assumed in the Standby position of the sequence
controller. The timer motor switch T-1b has just dropped off
causing engagement of contacts 157 and 158 and disengagement of
contacts 158 and 161. The room thermostat 173 is thus in circuit
with the timer motor through the closed contacts 157 and 158. The
other timer motor cycling switch T-2b is open at this time. Also
switch T-3b is open which has broken the circuit to the timer
solenoid 175 and the blower 176 for the electric heating system.
Also, load switches T-4b, T-5b and T-6b are open and thus the
heater banks 177, 178 and 179 are deenergized.
Assuming that the temperature in the electric heating system is
satisfactory and the limit control switch 180 is closed, the room
thermostat will be in command of the system. On call for heat, the
room thermostat switch will close and complete a circuit to the
timer motor through contacts 157 and 158 of the switch T-1b. The
timer motor will now start driving and rotate the cam shaft 115 in
a counterclockwise direction turning all the cams in unison. The
first action to occur is shifting of the switches T-1b and T-3b.
This action may be simultaneous or one switch may precede the
other. Closure of switch T-3b energizes the timer solenoid 175 in
series with the limit control 180. It also initiates operation of
the blower for the electric system. Shifting of the switch T-1b
opens the timer motor starting contacts 157--158 and closes the
maintaining contacts 158--161. This establishes a circuit to the
timer motor 172 which is now independent of the room thermostat
173. Switches T-4b, T-5b and T-6b will now close in sequence at
predetermined time intervals as charted in FIG. 37 bringing on the
heater banks 177, 178 and 179 in sequence. After the load switches
are closed, switch T-2b closes as described in connection with
switch 11 FIG. 3. Closure of switch T-2b establishes a shunt
circuit for the timer motor in series with the room thermostat
switch 173. This short circuiting of the transformer secondary
reduces the voltage supplied to the timer motor to zero and thus
the timer motor stops at this point. The timing mechanism therefore
stops with all three heater banks energized and the blower in
operation.
Unless overheating should occur and the limit control switch 180
opens, the heating will continue until the room thermostat 173 is
satisfied. This will break the shunt circuit across the transformer
secondary and reapply power to the timer motor through the
maintaining switch 158--161. The switches will now operate as shown
in the chart, FIG. 37. Referring to FIG. 25, it will be noted that
the cam 143 for the switch T-6b is in advance of the cams 142 and
141. Thus when the timing mechanism is restarted by opening of the
room thermostat switch 173, the first action that occurs is the
releasing of the latch 138 of switch T-6b which opens this switch,
deenergizing the heater bank 179. A predetermined time later, the
cam 142 releases latch 137, thus opening switch T-5b deenergizing
heater bank 178. A predetermined time later, the cam 141 releases
latch 135, opening switch T-4b which deenergizes heater bank 177.
The switch T-3b will remain closed for an additional period of time
to maintain the blower in operation for dissipating the heat from
the furnace. Just before the end of the cycle the switch T-3b opens
which deenergize the blower and also the timer solenoid 175. At the
end of the cycle, switch T-1b shifts back to the Standby position
shown in FIGS. 24 and 25. This breaks the maintaining circuit for
the timer motor and also places the timer motor back under the
control of the room thermostat switch 173.
It is desirable to open the motor cycling switch T-2b before
opening of the load switches T-6, T-5 and T-4. Unless this is done,
there is a possibility that the room thermostat might reclose and
stop the timing mechanism in mid position where one or all of the
load switches are open. One way to achieve this result is by the
use of a special cam 121a having a notch 181 just sufficient to
allow switch T-2b to close with the latch 139 in place. Thus just
as soon as the timer is restarted, the blades of switch T-2b are
raised off the latch 139 and the contacts of switch T-2b open. An
alternative method is to use a latch such as 138 operated by a cam
such as cam 120 of switch T-6b.
The above operation as charted in FIG. 37 occurs on a normal cycle
where no overheating occurs. If for some reason, overheating does
occur, the limit control switch 180 will open. This will deenergize
the timer solenoid 175 and also break the power circuit to the
transformer primary 170 thus preventing the timer motor 172 from
operating. Deenergizing solenoid 175 releases the latch 135 causing
opening of switch T-4b. The movement imparted to the latch by the
opening of switch T-4b releases latch 137 opening switch T-5b which
in turn releases latch 138 opening switch T-6b. This same action
also releases the latch 139 opening the motor switch T-2b. This
operation is charted in FIG. 38. It will be noted that the load
switches open instantly in response to overheating and that the
short circuit for the transformer primary is broken so that the
timer motor can operate when the limit control again applies power
to the transformer primary. Switch T-3b at this time remains closed
maintaining the blower in operation for dissipating the overheated
air.
When the temperature in the condition changing system is reduced to
an acceptable value, the limit control switch 180 will reclose thus
reapplying power to the timer solenoid and to the timer motor. The
timer will now run back to the starting point or Standby position
with the heater load switches open. If the room thermostat 173 is
still calling for heat at this time, the timer will start a new
cycle bringing on the heaters in sequence as previously
described.
From the foregoing it will be apparent that the control system
described on call for heat first starts the blower and then
energizes the heater banks in sequence. Unless overheating occurs,
the blowers and heaters will operate as long as the room thermostat
calls for heat. When the thermostat is satisfied, the timer is
restarted and turns off the heater banks in sequence. The system
also allows the blower to operate for an additional period for
dissipating the heated air and then stops the blower until the next
cycle. If overheating should occur, the load switches are opened
instantly instead of in sequence. Also, the timer is prevented from
operating until the overheating is dissipated, thus maintaining the
blower in operation for dissipating the heat. Once the limit
control switch recloses the timer resumes operation back to the
starting point with all of the load switches being maintained open.
If the room thermostat is still calling for heat when the timing
mechanism reaches the starting point, the blower and heater banks
will be again energized in sequence.
CASCADE ON-CASCADE OFF OPERATION FOR MULTIPLE COMPRESSOR
REFRIGERATION SYSTEMS
FIG. 31 is a schematic wiring diagram showing the application of
the cascade on-cascade off system to a refrigeration system having
three separate compressors or condition changing units. This system
utilizes the same mechanism shown schematically in FIG. 25
excepting that the time cycle is lengthened and the cams are
arranged on a cam shaft to give the sequence charted in FIG. 39. On
call for cooling, by the room thermostat 185, the timer motor 172
is energized through contacts 157 and 158 of timer motor switch
T-1b. Shortly thereafter switch T-1b transfers opening contacts 157
and 158 and closing contacts 158--161, establishing the maintaining
circuit for the timer motor. Also switch T-3b closes which
energizes the blower motor 186 for cooling the refrigerator
condenser or evaporator or both. This closure of switch T-3b also
energizes the timer solenoid 175 which pulls in for allowing the
timer load switches to close in sequence by action of the timer
cams. Shortly after switch T-3b closes, switch T-4b closes
energizing contactor coil C-1 which closes its double pole switches
C-1c energizing the compressor 187. A predetermined time later,
such as 10 seconds, switch T-5b closes energizing contactor coil
C-2 which closes double pole switches C-2c energizing compressor
188. A predetermined time later switch T-6b closes energizing
contactor coil C-3 which closes switches C-3c energizing compressor
189. As shown in the chart of FIG. 39 the timer motor will continue
running through the "Short Cycle Adder" period which may be an
additional 2 minutes 30 seconds. At this point switch T-2b closes
short circuiting the transformer secondary and thus stopping the
timer motor 172.
On a normal cycle the compressors and blower will remain in
operation until the room thermostat 185 becomes satisfied. At this
time the thermostat breaks the shunt circuit thus applying power to
the timer motor and causing it to continue operation. The timer
will now proceed through the "Off-Delay" period opening switches
T-6b, T-5b, T-4b and T-3b in the sequence stated. Thus the
compressors and blower motor are deactivated in sequence. At the
end of this "Off-Delay" the timer continues running through the
"Equalize Delay" period. This equalizing period may be as long as 5
minutes. After the timer has run through this pressure equalizing
period, it returns to the Standby position where switch T-1b
assumes the position shown in FIG. 31. The system is thus at rest
and a new cycle will be started on call for cooling by the
thermostat 185.
If a short cycle should occur as by opening of the high-low
pressure cutout 190, it will break the circuit to the transformer
primary 170 and also to the timer solenoid 175. The solenoid will
drop out causing immediate opening of the load switches T-4b, T-5b
and T-6b. This drops out the compressor contactors which in turn
deactivates the compressors. Switch T-3b is not affected by
dropping out of the solenoid and remains closed. Thus power is
maintained to the blower. However, as the high-low pressure cutout
190 has broken the circuit to the transformer primary, the timer
motor will not run even though switch T-2b opened from dropping out
of the solenoid. This deenergization of the timer motor by the
high-low pressure cutout adds an indefinite delay period to the
delay provided by the timer. Once the undesirable condition in the
refrigeration system is dissipated, the safety switch 190 will
reclose thus reapplying power to the timer solenoid and also
energizing the timer motor so that it can begin timing for the
balance of the delay. As shown in the chart of FIG. 40 the delay
provided by the timer at this time is the sum of the unused portion
of the short cycle adder and the regular pressure equalizing period
built into the timer. The load switches T-4b, T-5b and T-6b will
remain open until the timer recycles back to the starting point and
recloses the switches in the proper sequence. Switch T-3b will
remain closed until the timer has entered the equalizing delay
portion of the cycle. At this time the timer solenoid and the
blower motor are deenergized and they will not again be energized
until the start of a new cycle.
From the foregoing description it will be apparent that my cascade
on-cascade off controller when applied to a multiple compressor
refrigeration system provides for starting and stopping the
compressors in sequence during a normal cycle and also provides a
pressure equalization period following the compressor stopping on
one cycle before the compressors can be restarted in the next
cycle. It will also be apparent that my control system provides for
starting the blower in advance of compressor operation and also for
maintaining the blower in operation for a period of time after the
compressors are stopped on a normal cycle. In the event of a short
cycle which is terminated by the high-low pressure cutout, the
compressors are stopped simultaneously and immediately. The timer
motor is deenergized maintaining the blower switch closed as long
as the undesirable condition occurs. In addition, the timer
mechanism itself provides an extra delay in addition to the regular
equalizing delay. These features thus provide a substantial longer
delay between stopping and restarting of the compressors when the
system is malfunctioning than occurs when the system is operating
normally. This increase in delay time in response to
malfunctioning, of course, adds considerable more protection for
the compressors.
In addition, the arrangement of the switch T-3b controlling the
blower and the location of the high-low pressure cutout in the
timer motor circuit serve to maintain the blower in operation
during the entire time that the high-low pressure cutout switch is
open. Thus this arrangement both prolongs the delay period in
response to malfunctioning and also ensures operation of the blower
for dissipating the high or low pressure causing the stoppage. It
should also be noted that the switch T-3 also serves to deenergize
the solenoid when the compressors are out of operation.
FIGS. 26 and 27 show a modification in which switches T-1b and T-3b
are operated simultaneously by a single cam. As shown in FIG. 26,
switch T-3b is of the same construction as shown in FIG. 22 and
includes an upper switch blade 145' and a lower switch blade 146'.
Switch T-1b consists of an upper switch blade 156', a middle switch
blade 159' and a lower switch blade 160'. These switch blades are
anchored to the terminal panel 10 in the same plane as switch
blades 145' and 146' of switch T-3b. The switch blades of switch
T-3b are biased downwardly toward the cam 152. The switch blades
156', 159' and 160' of switch T-1b are biased upwardly toward cam
152. A spacer 195 is loosely mounted in suitable holes in the
switch blades 145' and 159' and serves to cause these switch blades
to move in unison. A spacer 196 extends between the switch blade
146' and the switch blades 156' and 160'. As shown in FIG. 27, this
spacer 196 passes freely through an opening 197 in switch blade
159' and has no effect on the position of blade 159'. The spacer
196 however, bears against the switch blades 156' and 160'. This
serves to maintain the spacing between these two blades and cause
these blades to operate in unison with the cam operated switch
blade 146 of switch T-3b.
In the positions shown, the switch T-3b is open and its lower
switch blade 146' has dropped off the cam 152. Switch blade 145' is
now riding the cam and is in its upper position. As the switch
blade 146' is in its lower position, it has depressed through
spacer 196 the switch blades 156' and 160'. This has caused
engagement of contacts 157 and 158 and disengagement of contacts
158 and 161.
When the cam 152 continues its rotation and drops off the blade
145' this blade drops to cause engagement of the contacts 145 and
146 of switch T-3b. It also through spacer 195 depresses switch
blade 159' disengaging contacts 157 and 158 and engaging contacts
158 and 161.
The arrangement above described using a single cam makes it
possible to make the control package smaller and also ensures
simultaneous actuation of two independent switches in cases where
simultaneous action is necessary.
From the foregoing it will be apparent that the present invention
provides a simple and compact unit for bringing on a number of
condition changing units or motors in sequence. The invention also
provides for either normal simultaneous off operation, or cascade
off operation combined with simultaneous off operation in the event
of a power interruption of malfunction. It will also be apparent
that the invention provides for control of a system, directly by a
sensitive low voltage thermostat or other condition responsive
device and that no complicated circuitry including relays is
involved. It will be further apparent that the invention as applied
to refrigeration control not only provides sequence control for a
number of compressors but also provides for pressure equalization
between normal operations and a prolonged delay between operations
in event of a malfunction.
While a preferred form of the invention has been shown and
described, it will be apparent that many modifications, omissions,
etc. may be made without departing from the spirit and scope of the
invention.
* * * * *