Information
-
Patent Grant
-
6765157
-
Patent Number
6,765,157
-
Date Filed
Wednesday, July 24, 200221 years ago
-
Date Issued
Tuesday, July 20, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Schwegman, Lundberg, Woessner & Kluth, P.A.
-
CPC
-
US Classifications
Field of Search
US
- 200 1 V
- 200 1 R
- 200 5032
- 200 5033
- 200 573
- 200 574
- 200 401
- 200 416
- 200 428
- 200 461
- 200 33 R
- 200 34
- 200 46
- 200 45 G
- 218 154
-
International Classifications
-
-
Disclaimer
Terminal disclaimer
Abstract
A transfer switch that includes output contacts, primary input contacts, secondary input contacts and a toggle mechanism. The toggle mechanism includes moving contacts that alternately connect the output contacts with the primary and secondary input contacts. The transfer switch includes an actuator that rotates the first crossbar to alternately engage a first set of moving contacts with the output contacts and the primary input contacts, and rotates the second crossbar to alternately engage a second set of moving contacts with the output contacts and the secondary input contacts. A method of actuating a transfer switch to alternate the supply of power to an electric load. The method includes rotating a first crossbar within the transfer switch to engage a first set of switching contacts with a primary power source and rotating a second crossbar within the transfer switch to engage a second set of switching contacts with a secondary power source.
Description
FIELD OF THE INVENTION
The present invention relates to a transfer switch, and in particular to a transfer switch that includes an improved actuator.
BACKGROUND
A transfer switch is used to switch an electric load back and forth between a primary source, such as a utility, and a secondary source, such as a generator. Transferring power from the primary source to the secondary source is necessary when the utility experiences a blackout. The transfer switch is also used to switch the power source back to utility power when the power outage is over.
A typical transfer switch is composed of an actuator and a toggle mechanism. The actuator operates by supplying energy to the toggle mechanism to maneuver movable contacts that are within the toggle mechanism relative to stationary power input contacts. The movable contacts engage one set of stationary contacts when power is supplied from the primary source and engage another set of stationary contacts when power is supplied from the secondary source.
Actuators are activated either manually or automatically at a desired time to supply energy to the movable contacts on the toggle mechanism. Many transfer switches are able to disconnect the load from both sources for a desired period of time in order to allow residual electricity to discharge before the load is switched to an alternate power source.
FIGS. 1-4
illustrate an improved electric transfer switch
10
. Transfer switch
10
includes a toggle mechanism
12
(FIG.
2
). The toggle mechanism
12
includes a pair of crossbars
14
,
15
(
FIGS. 3 and 4
) that extend through the transfer switch
10
. The crossbars
14
,
15
in the toggle mechanism
12
are connected to an actuator
16
of the present invention that rotates the crossbars
14
,
15
about their respective longitudinal axes.
A first set of moveable contacts
20
is carried by crossbar
14
and a second set of movable contacts
25
is carried by crossbar
15
. Each moveable contact
20
,
25
is connected to an output contact
21
and is adapted to be intermittently connected to a respective primary input contact
22
or a secondary input contact
23
depending on which crossbar
14
,
15
the movable contacts
20
,
25
are mounted on. Cams
29
are mounted on the crossbars
14
,
15
to maneuver the movable contacts
20
,
25
into, and out of, engagement with the stationary input contacts
22
,
23
.
FIG. 3
shows the movable contacts
20
engaged with the primary input contacts
22
when power is being supplied from a primary power source, such as a utility. As shown in
FIG. 4
, when there is an interruption in the primary power supply, the cams
29
on crossbar
14
rotate to disengage the movable contacts
20
from the primary input contacts
22
, and the cams
29
on crossbar
15
rotate to allow the movable contacts
25
to engage secondary input contacts
23
so that power can be supplied from a secondary power source, such as a generator.
A similar operation is performed to transfer back to the primary source from the secondary source. The cams
29
on crossbar
15
rotate to disengage the movable contacts
25
from the secondary input contacts
23
and the cams
29
on crossbar
14
rotate to allow the movable contacts
20
to engage the primary input contacts
22
so that power can once again be supplied from the primary source.
Springs
28
are disposed between each of the moveable contacts
20
,
25
and another portion of the transfer switch
10
. The springs
28
apply a force to each movable contact
20
,
25
that directs each moveable contact
20
against a corresponding stationary input contact
22
,
23
.
During the operation of a typical transfer switch there may be extreme conditions where the movable contacts can become slightly tack welded to the stationary contacts. Known actuators are often unable to apply a large enough force to the contact-carrying members within the transfer switch to permit the contacts to open in a desired amount of time. In addition, existing actuators often times do not allow for different programmed transitions of the movable contacts within the transfer switch between the stationary input contacts of the alternative power sources. One example of a programmed transition could be where one set of moving contacts is disengaged from the primary input contacts followed by a predetermined delay before the another set of movable contacts is engaged with the secondary input contacts.
There is a need for actuator
16
which can be used with transfer switches that include two rotating crossbars. Actuator
16
is able to independently operate the two crossbars and generate enough operating force to separate any tack-welded contacts that need to be maneuvered by the crossbars. Actuator
16
is also be able to provide for a variety of programmed transitions between two separate power sources.
SUMMARY OF THE INVENTION
The present invention relates to a transfer switch that includes an actuator which is capable of independently operating two rotating crossbars within the transfer switch. Since the crossbars in the transfer switch are operated independently, the actuator may include two similar but interrelated mechanisms such that one mechanism maneuvers one crossbar and the other mechanism maneuvers the other crossbar.
Using two mechanisms within a single actuator facilitates operating the actuator with a variety of programmed transitions between two separate power sources. One such transition could involve including a predetermined delay before switching power sources. Another programmed transition could be a closed transition where both sets of movable contacts within the transfer switch are simultaneously engaged with the primary and secondary input contacts before one set of movable contacts is disengaged. The closed transition provides a no break transfer of power from one source to another. No break power transfers are likely to increase the service life of the contacts within the transfer switch, as well as providing the primary function of supplying loads that can not tolerate any kind of interruption, however brief.
In addition, it is easier to design each of the mechanisms so that they generate a larger operating force on the crossbars than could be generated by a single mechanism. The larger operating force on each crossbar helps separate the movable contacts when the contacts have become tack-welded together.
The transfer switch includes output contacts, primary input contacts, secondary input contacts and a toggle mechanism. The toggle mechanism includes moving contacts that alternately connect the output contacts with the primary and secondary input contacts. The transfer switch further includes an actuator that rotates the first crossbar to alternately engage a first set of moving contacts with the output contacts and the primary input contacts, and rotates the second crossbar to alternately engage a second set of moving contacts with the output contacts and the secondary input contacts.
The present invention also relates to a method of actuating a transfer switch to alternate the supply of power to an electric load. The method includes rotating a first crossbar within the transfer switch to engage a first set of switching contacts with a primary power source. The method further includes rotating a second crossbar within the transfer switch to engage a second set of switching contacts with a secondary power source.
The present invention also relates to a transfer switch that includes output contacts, primary input contacts, secondary input contacts and a toggle mechanism which has a first crossbar and a second crossbar. The transfer switch further includes means for rotating the first crossbar to engage a first set of switching contacts with a primary power source and rotating the second crossbar to engage a second set of switching contacts with a secondary power source.
In another aspect, the present invention is directed to an actuator for a transfer switch. The actuator includes a pair of couplings that are each adapted to be connected to a separate crossbar in the transfer switch, and a pair of indexing mechanisms that are each engaged with a separate one of the couplings to apply torque to the couplings. The actuator further includes a pair of crankshafts that are each engaged with a separate one of the indexing mechanisms to apply torque to the indexing mechanisms, and a pair of stored energy devices that are each engaged with a separate one of crankshafts to apply torque to the crankshafts using energy released by the stored energy devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view illustrating a transfer switch of the present invention.
FIG. 2
is a top view of the transfer switch shown in FIG.
1
.
FIG. 3
is a schematic cross-sectional view of the transfer switch shown in
FIG. 2
taken along line
3
—
3
with the transfer switch in position to supply power from a primary power source.
FIG. 4
is a schematic cross-sectional view similar to
FIG. 3
with the transfer switch in position to supply power from a secondary power source.
FIG. 5
is a side view illustrating the actuator in the transfer switch shown in
FIG. 1
with portions of the actuator removed for purposes of clarity.
FIG. 6
is a perspective view illustrating an opposing side of the actuator shown in
FIG. 5
with portions of the actuator removed for purposes of clarity.
FIG. 7
is a perspective view illustrating an opposing side of the actuator shown in
FIG. 6
with portions of the actuator removed for purposes of clarity.
FIG. 8
is a perspective view similar to
FIG. 7
with additional portions of the actuator removed for purposes of clarity.
FIG. 9
is a perspective view similar to
FIG. 8
with some portions of the actuator added for descriptive purposes.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying drawings which show by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and structural changes made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.
As stated previously,
FIGS. 1-4
show an example embodiment of an electric transfer switch
10
that includes an improved actuator
16
. Toggle mechanism
12
is connected to actuator
16
such that actuator
16
rotates first crossbar
14
to alternately engage a first set of moving contacts
20
with output contacts
21
and primary input contacts
22
. Actuator
16
also rotates second crossbar
15
to alternately engage a second set of moving contacts
25
with output contacts
21
and secondary input contacts
23
.
FIG. 3
shows the movable contacts
20
engaged with the primary input contacts
22
when power is being from a primary power source, such as a utility. As shown in
FIG. 4
, when there is an interruption in the primary power supply, actuator
16
rotates crossbar
14
to disengage the first set of movable contacts
20
from the primary input contacts
22
. Actuator
16
also rotates crossbar
15
rotate to engage the second set of movable contacts
25
with secondary input contacts
23
so that power can be supplied from a secondary power source, such as a generator.
A similar operation is performed to transfer back to the primary source from the secondary source. Actuator
16
rotates second crossbar
15
to disengage the second set of movable contacts
25
from secondary input contacts
23
and rotates first crossbar
14
to engage the first set of movable contacts
20
with the primary input contacts
22
so that power can once again be supplied from the primary source. In some embodiments, first crossbar
14
is parallel to second crossbar
15
and actuator
16
rotates first crossbar
14
in one direction and rotates second crossbar
15
in an opposing direction.
As shown in
FIGS. 5-9
, actuator
16
may include a pair of couplings
60
A,
60
B such that one coupling
60
A applies torque to first crossbar
14
and the other coupling
60
B applies torque to second crossbar
15
(FIGS.
5
and
6
). In some embodiments, actuator
16
includes a pair of indexing mechanisms
62
A,
62
B such that one indexing mechanism
62
A applies torque to one coupling
60
A and the other indexing mechanism
62
B applies torque to the other coupling
60
B. Each indexing mechanism
62
A,
62
B may include a respective fork
63
A,
63
B such that one fork
63
A engages one coupling
60
A and the other fork
63
B engages the other coupling
60
B (
FIGS. 5
,
8
and
9
).
The couplings
60
A,
60
B and indexing mechanisms
62
A,
62
B can have any suitable configuration as long as torque is transferred to the respective crossbars
14
,
15
through the couplings
60
A,
60
B and indexing mechanisms
62
A,
62
B. In addition, in some embodiments indexing mechanisms
62
A,
62
B may include some device other than forks
63
A,
63
B to transfer torque to couplings
60
A,
60
B.
Actuator
16
may further include a pair of locks
64
A,
64
B. One lock
64
A secures one indexing mechanism
62
A and the other lock
64
B secures the other indexing mechanism
62
B when the first and second sets of moving contacts
20
,
25
on the first and second crossbars
14
,
15
are disengaged from the respective primary and secondary input contacts
22
,
23
. Locks
64
A,
64
B prevent crossbars
14
,
15
from moving so that respective moving contacts
20
,
25
can not engage primary and secondary input contacts
22
,
23
unless the corresponding lock
64
A,
64
B is released.
Although locks
64
A,
64
B can have any suitable configuration, in the illustrated sample embodiment, locks
64
A,
64
B include in part, pivot arms
65
A,
65
B (FIGS.
7
-
9
), transfer bars
69
A,
69
B and linkages
73
A,
73
B (FIG.
8
). Actuator
16
may further include a pair of solenoids
66
A,
66
B (
FIG. 9
) such that one solenoid
66
A releases one lock
64
A and the other solenoid
66
B releases the other lock
64
B to allow the respective indexing mechanisms
62
A,
62
B to move. Solenoids
66
A,
66
B may be used in combination with a controller to permit locks
64
A,
64
B to operate automatically.
A partial description of the operation of one of the locks
64
A is summarized hereafter. Plunger
74
A on solenoid
66
A is retracted such that plunger
74
A rotates pivot arm
65
A. Pivot arm
65
A engages transfer bar
69
A, which, in turn, manipulates linkage
73
A permitting fork
63
A to rotate and thereby allow crossbar
14
to rotate.
In some embodiments, actuator
16
includes a pair of handles
67
A,
67
B (FIGS.
5
and
6
). One handle
67
A releases one lock
64
A and the other handle
67
B releases the other lock
64
B to allow the indexing mechanisms
62
A,
62
B to move.
Actuator
16
includes a pair of crankshafts
68
A,
68
B such that one crankshaft
68
A engages one indexing mechanism
62
A and the other crankshaft
68
A engages the other indexing mechanism
62
B. Each crankshaft
68
A,
68
B includes a respective first throw
71
A,
71
B such that one first throw
71
A engages one fork
63
A and the other first throw
71
B engages the other fork
63
B (FIGS.
5
and
9
).
Actuator
16
may further include a pair of stored energy devices, such as springs
72
A,
72
B (FIG.
5
), that engage a respective second throw
75
A,
75
B on each of the crankshafts
68
A,
68
B. One spring
72
A engages one second throw
75
A and the other spring
72
B engages the other second throw
75
B.
In an example embodiment, actuator
16
includes a motor
80
that is coupled to each of the crankshafts
68
A,
68
B through one or more force-transmitting devices, such as gears. Motor
80
adds energy to a respective one of the springs
72
A,
72
B as soon as the corresponding first or second set of moving contacts
20
,
25
on the first and second crossbars
14
,
15
is disengaged from the respective primary or secondary input contacts
22
,
23
. The stored energy in springs
72
A,
72
B is eventually released to move crossbars
14
,
15
and re-engage the first and/or secondary moving contacts
20
,
25
with the respective primary and secondary input contacts
22
,
23
.
Actuator
16
may further include a pair of crank locks
81
A,
81
B. One crank lock
81
A secures one crankshaft
68
A and the other crank lock
81
B secures the other crankshaft
68
A. The respective crank locks
81
A,
81
B secure the corresponding crankshafts
68
A,
68
B after motor
80
stores sufficient energy in a corresponding one of the springs
72
A,
72
B. In some embodiments, handles
67
A,
67
B also release respective crank locks
81
A,
81
B to allow the respective crankshafts
68
A,
68
B to move.
The present invention also relates a method of actuating a transfer switch
10
to alternate the supply of power to an electric load. The method includes rotating a first crossbar
14
within the transfer switch
10
to engage a first set of switching contacts
20
with a primary power source and rotating a second crossbar
15
within the transfer switch
14
to engage a second set of switching contacts
23
with a secondary power source.
Rotating first crossbar
14
within transfer switch
10
may include applying torque to first crossbar
14
using energy delivered by first spring
72
A. In addition, rotating second crossbar
15
within transfer switch
10
may include applying torque to second crossbar
15
using energy delivered by second spring
72
B. In some embodiments, first crossbar
14
and second crossbar
15
are parallel such that rotating first crossbar
14
includes rotating first crossbar
14
in one direction and rotating second crossbar
15
includes rotating second crossbar
15
in an opposing direction.
It is understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
Claims
- 1. A transfer switch comprising:output contacts; primary input contacts; secondary input contacts; a toggle mechanism including a first crossbar and a second crossbar; and an actuator that rotates the first crossbar to alternately engage a first set of moving contacts with the output contacts and the primary input contacts, and rotates the second crossbar to alternately engage a second set of moving contacts with the output contacts and the secondary input contacts.
- 2. The transfer switch of claim 1 wherein the first crossbar is parallel to the second crossbar.
- 3. The transfer switch of claim 2 wherein the actuator rotates the first crossbar in one direction and rotates the second crossbar in an opposing direction.
- 4. The transfer switch of claim 1 wherein the actuator includes a pair of couplings such that one coupling applies torque to the first crossbar and the other coupling applies torque to the second crossbar.
- 5. The transfer switch of claim 4 wherein the actuator includes a pair of indexing mechanisms such that one indexing mechanism applies torque to the one coupling and the other indexing mechanism applies torque to the other coupling.
- 6. The transfer switch of claim 5 wherein the actuator includes a pair of locks such that the one lock secures one indexing mechanism and the other lock secures the other indexing mechanism when the moving contacts on the first and second crossbars are disengaged from the primary and secondary input contacts.
- 7. The transfer switch of claim 6 wherein the actuator includes a pair of solenoids such that one solenoid releases the one lock and the other solenoid releases the other lock to allow the indexing mechanisms to move.
- 8. The transfer switch of claim 6 wherein the actuator includes a pair of handles such that one handle releases the one lock and the other handle releases the other lock to allow the indexing mechanisms to move.
- 9. The transfer switch of claim 5 wherein each indexing mechanism includes a fork such that one fork engages the one coupling and the other fork engages the other coupling.
- 10. The transfer switch of claim 5 wherein the actuator includes a pair of crankshafts such that one crankshaft engages the one indexing mechanism and the other crankshaft engages the other indexing mechanism.
- 11. The transfer switch of claim 10 wherein each of the crankshafts includes a first throw and each indexing mechanism includes a fork such that one fork engages one first throw and the other fork engages the other first throw.
- 12. The transfer switch of claim 11 wherein the actuator includes a pair of stored energy devices and each of the crankshafts includes a second throw such that one stored energy device engages one second throw and the other stored energy devices engage the other second throw.
- 13. The transfer switch of claim 12 wherein each of the stored energy devices is a spring.
- 14. The transfer switch of claim 13 wherein the actuator includes a motor that is coupled to each of the crankshafts.
- 15. The transfer switch of claim 14 wherein the motor adds energy to the stored energy devices when the moving contacts on the first and second crossbars are engaged with the primary and secondary input contacts.
- 16. The transfer switch of claim 10 wherein the actuator includes a pair of crank locks such that one crank lock secures the one crankshaft and the other crank lock secures the other crankshaft.
- 17. The transfer switch of claim 16 wherein the actuator includes a pair of handles such that one handle releases the one crank lock and the other handle releases the other crank lock to allow the crankshafts to move.
- 18. A method of actuating a transfer switch to alternate the supply of power to an electric load comprising:rotating a first crossbar within the transfer switch to engage a first set of switching contacts with a primary power source; and rotating a second crossbar within the transfer switch to engage a second set of switching contacts with a secondary power source.
- 19. The method of claim 18 wherein rotating the first crossbar within a transfer switch includes applying torque to the first crossbar using energy delivered by a first spring, and rotating the second crossbar within a transfer switch includes applying torque to the second crossbar using energy delivered by a second spring.
- 20. The method of claim 18 wherein the first crossbar and the second crossbar are parallel such that rotating the first crossbar within the transfer switch includes rotating the first crossbar in one direction and rotating the second crossbar within the transfer switch includes rotating the second crossbar in an opposing direction.
- 21. A transfer switch comprising:output contacts; primary input contacts; secondary input contacts; a toggle mechanism including a first crossbar and a second crossbar; and means for rotating the first crossbar to engage a first set of switching contacts with a primary power source and rotating the second crossbar to engage a second set of switching contacts with a secondary power source.
- 22. An actuator for a transfer switch comprising:a pair of couplings that are each connected to a separate crossbar in the transfer switch; a pair of indexing mechanisms that are each engaged with a separate one of the couplings to apply torque to the couplings; a pair of crankshafts that are each engaged with a separate one of the indexing mechanisms to apply torque to the indexing mechanisms; and a pair of stored energy devices that are each engaged with a separate one of crankshafts to apply torque to the crankshafts using energy released by the stored energy devices.
- 23. The actuator of claim 22 further comprising a pair of locks such that one lock secures one indexing mechanism and the other lock secures the other indexing mechanism.
- 24. The actuator of claim 23 further comprising a pair of solenoids such that one solenoid releases the one lock and the other solenoid releases the other lock to allow the indexing mechanisms to move.
- 25. The actuator of claim 22 wherein each crankshaft includes a first throw and each indexing mechanism includes a fork such that one fork engages one first throw and the other fork engages the other first throw.
- 26. The actuator of claim 25 wherein each crankshaft includes a second throw such that one stored energy device engages one second throw and the other stored energy device engages the other second throw.
- 27. The actuator of claim 26 wherein each stored energy device is a spring.
- 28. The actuator of claim 22 wherein the actuator includes a motor that is coupled to each crankshaft to add energy to the stored energy devices.
- 29. The actuator of claim 22 wherein the actuator includes a pair of crank locks such that one crank lock secures one crankshaft and the other crank lock secures the other crankshaft.
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