Patent Grant
7696448
1. Field of the Invention
The present invention relates to an electrical switching apparatus operating mechanism and, more specifically to a closing protection mechanism for a closing assembly having an over-toggle linkage.
2. Background Information
An electrical switching apparatus, typically, includes a housing, at least one bus assembly having a pair of contacts, a trip device, and an operating mechanism. The housing assembly is structured to insulate and enclose the other components. The at least one pair of contacts include a fixed contact and a movable contact and typically include multiple pairs of fixed and movable contacts. Each contact is coupled to, and in electrical communication with, a conductive bus that is further coupled to, and in electrical communication with, a line or a load. A trip device is structured to detect an over current condition and to actuate the operating mechanism. An operating mechanism is structured to both open the contacts, either manually or following actuation by the trip device, and close the contacts.
That is, the operating mechanism includes both a closing assembly and an opening assembly, which may have common elements, that are structured to move the movable contact between a first, open position, wherein the contacts are separated, and a second, closed position, wherein the contacts are coupled and in electrical communication. The operating mechanism includes a rotatable pole shaft that is coupled to the movable contact and structured to move each movable contact between the closed position and the open position. Elements of both the closing assembly and the opening assembly are coupled to the pole shaft so as to effect the closing and opening of the contacts. The closing assembly may be actuated manually by a user input or in response to an input from a remote actuator.
The trip device included an over-current sensor, a latch assembly and may have included one or more additional links that were coupled to the toggle assembly. Alternately, the latch assembly was directly coupled to the toggle assembly. When an over-current situation occurred, the latch assembly was released allowing the opening spring to cause the toggle assembly to collapse. When the toggle assembly collapsed, the toggle assembly link coupled to the pole shaft caused the pole shaft to rotate and thereby move the movable contacts into the open position.
Low and medium voltage electrical switching apparatus typically had stored energy devices, such as a closing spring and an opening spring, and at least one link coupled to the pole shaft. The at least one link, typically, included two links that acted cooperatively as a toggle assembly and which were coupled to each other at a toggle joint. When the contacts were open, the toggle assembly was in a first, collapsed configuration and, conversely, when the contacts were closed, the toggle assembly was, typically, in a second, toggle position, that is, an in-line configuration, or in a slightly over-toggle position. The closing spring was usually compressed, or “charged,” by a motor or a user utilizing a lever arm. The closing spring, typically, holds more stored energy than the opening springs and during the closing operation wherein the contacts are moved to the second, closed position, the opening spring was charged. The opening spring biased the pole shaft, and therefore the toggle assembly, to the collapsed position. The opening spring and toggle assembly were maintained in the second, toggle position by the trip device.
When the contacts were in the first, open position, the toggle assembly links, which define lines of force, were “folded,” typically at an acute angle. When the mechanism was closing, a closing component applied a closing force to the toggle joint. The closing component moved the links until the lines of force, that is, the links, were nearly in-line or on “center.” If the fully closed position of the separable contacts was reached before the lines of force were fully in-line, the closing assembly is an “under-toggle” mechanism and the toggle joint continued to rest on the closing component to prevent the toggle joint from collapsing. In this type of closing assembly, the closing component was, typically, a cam. If, during closing, the closing component moved the toggle joint through the in-line position and beyond, the closing assembly is an “over-toggle” mechanism and the toggle joint typically rested upon a stop that is separate from the closing component. That is, the toggle joint typically came to rest on a stop pin that prevented the toggle joint from collapsing in a reverse direction.
In either an under-toggle or over-toggle mechanism, the contacts would initially engage each other when the angle of the lines of force were approaching the in-line position. After the contacts engage, the driving force required to complete the closing of the contacts increases. That is, prior to the contacts engaging each other, the closing component was, essentially, only moving the moving contact and compressing the opening springs. Once the contacts engaged each other, the closing component was required to overcome any electromagnetic forces generated by a current passing through the contacts, as well as, forces created by the contact spring as they were being compressed. If the closing component was not able to overcome these forces, there was a chance that the closing operation could stall. If the closing operation stalls, dangerous arcing may occur at the contacts if the contacts are subject to inadequate force or support, for example is the contacts are held in close proximity or if the contacts slowly separate from each other.
Some under-toggle mechanisms have attributes that mitigate the consequences of a stall. That is, when the closing component is a cam acting upon the toggle joint, the cam surface is rising, that is, increasing in radius, so as to effect the movement of the toggle joint. Such a cam is structured to rotate in a single direction during closing, wherein the radius of the cam is increasing, and subsequent charging, wherein the radius of the cam is generally constant. Thus, if a stall occurs, the cam needs only to be rotated further, such as by charging after the close attempt, to cause the toggle joint to be moved into the proper position.
An over-toggle mechanism, however, is not structured to be supported by the closing component. Typically, the closing component acts upon the toggle joint and is then, slowly, withdrawn during the charging of the closing spring. Thus, unlike an under-toggle mechanism, a stall in such a closing assembly could allow the toggle joint to return to the open configuration. If, for example, the toggle joint is resting on the closing component as it is being slowly withdrawn, the contacts will be slowly separated allowing for dangerous arcing to occur.
It is further noted that a device may have a high-current capacity for withstanding an electrical fault that appears after the device is already closed, but may not have enough mechanical energy to complete a closure on that same fault current. That is, high current flowing in the device adds electromagnetic force to the springs which resist closing and increasing the mechanical energy to close on all such faults would shorten the mechanical life or add cost to the mechanism. The trip device is often self-powered by current passing through the contacts of the electrical switching apparatus, and therefore the trip device is inactive before closing. If a fault current which is higher than the closing, or “making” capacity, but lower than the “withstand” capacity appears in the electrical switching apparatus, the trip device must determine if the operating mechanism is closing, in which case the trip device should trip open to protect against harmful arcing at the contacts due to stalling at less-than-fully-closed, or the operating mechanism was already closed, in which case the trip device should remain closed until the manufacturer or customer-programmed delay time for tripping is reached.
One strategy for immediately tripping an operating mechanism that is closing on a fault above its making capacity is the use of a “time-delay” switch. This type of switch senses the state of the device, typically by sensing the pole shaft position, and connects to the trip device. The switch is held in one state when the device is open, and released to move to its other state when the electrical switching apparatus is closed. The switch assembly typically contains a mass with a relatively light bias spring resulting in an inertial delay off its motion when the device closes. This delay serves as a mechanical memory used by the trip device when a fault current above the making capacity appears. If the switch indicates the “device-closed” position, then the device was already closed some moments before the current appeared and the operating mechanism is not attempting to close on the high current; therefore it is not necessary to trip open to protect against prolonged harmful arcing. If the switch still indicates the “device-open” position, then the device was open moments before and the current flowing is the result of a closure attempt. Thus, the trip device must immediately re-open the contacts to protect against a potential stall.
As a result of its kinematics, an over-toggle mechanism has the characteristic of “over-driving” the contacts as the lines of force passes through in-line, or “center”, before settling back to the full closed position. Therefore, in a normal closing, the pole shaft is at the full closed position twice; once before the lines of force reach center, and again after passing through center. A switch sensing the pole shaft position, such as the time delay switch, is not able to discriminate between fully closed and partially-closed, where it could potentially stall. Despite these characteristics, there are some reasons to select over-toggle mechanism for some applications, rather than under-toggle mechanisms.
The closing protection mechanism provided herein includes a control unit, a sensing switch and a sensing switch actuator. The control unit is coupled to, and in electronic communication with, the trip device. The control unit is structured to receive a sensing switch signal and to provide a control signal to the trip device. The sensing switch is coupled to, and in electronic communication with, the control unit. The sensing switch is disposed adjacent to the toggle assembly. The sensing switch is structured to provide a sensing switch signal to the control unit. The sensing switch actuator is disposed on the toggle assembly. The sensing switch actuator is structured to actuate the sensing switch. The sensing switch is structured to be actuated by the sensing switch actuator when the toggle assembly is in the second, over-toggle configuration.
Thus, the sensing switch detects the “toggle angle” between the lines of force of the toggle assembly and allows for schemes for applying such information to protect against potential stalled closures. The sensing switch of this invention also allows unimpeded tripping motion out of any condition between and including open and closed in this embodiment, the switch is mounted to the mechanism side plate and actuated by a cam lobe at the fixed end of the support link. Preferably, the toggle assembly is driven by a ram assembly as set forth in application Ser. No. 11/693,198, filed Mar. 29, 2007, entitled “SPRING DRIVEN RAM FOR CLOSING AN ELECTRICAL SWITCHING APPARATUS” which is incorporated by reference.
Any time enough current to sense and self-power the trip unit is flowing through the device, a timer, preferably in the control unit, starts counting a number of milliseconds. If the sensing switch does not indicate full closed within the preset time, which may be based on the maximum expected duration of a complete closure at the current range sensed, and could be shorter—including zero delay—if desired to maximize protection at high currents, the electrical switching apparatus trips. Tripping for this reason may create a “cause of trip code” that can be identified by on a display. If a current, even a current close to the “withstand” limit, is sensed, but the sensing switch indicates full-closed, or begins to indicate full-closed within the allowed number of milliseconds, the trip device would sense full successful closure and revert to an appropriate pre-programmed trip delay settings for the current level sensed. Maximum continuity of service is achieved by further sensing the actual outcome in addition to the “predicted” outcome of an attempt to close an individual electrical switching apparatus in its service conditions.
Alternatively, the trip device could be configured not to trip due to a perceived stall condition unless the current is larger than a pre-selected threshold. When the sensing switch reports that the operating mechanism is not fully closed at currents below the threshold, which are less probable events and do not present substantial immediate danger, the contacts would remain closed and a diagnostic code, such as, but not limited to, a unique flashing pattern of a “status” LED could be used to signal a user that the device may not be fully closed, or that there may be a problem with the switch. If an overload or fault current appears later, the trip device would trip the operating mechanism at an appropriate time. This option would further ensure best continuity of service and remove concerns about the reliability of the switch itself or the wiring by eliminating normal-load-current nuisance trips.
It is noted that this configuration has the added benefit of protection when a stalled close occurred with an un-energized primary circuit and then the trip device is later energized when current begins flowing. A time-delay switch would have lost its memory, which extends only a number of milliseconds prior to the appearance of current. A stall is least likely to occur when there is no “electrical load” but is still possible considering the variation and potential “noise factors” a device may be exposed to during its life.
The tolerance band for the point at which the sensing switch changes state to report full closed is the range between in-line configuration and fully closed over-toggle configuration, allowing for practical placement of the sensing switch even with normal product variation. Once the lines of force in the toggle assembly have moved past center, the toggle assembly can be expected to continue to “fully closed” under the forces acting on the toggle assembly. Any position past center constitutes a band where the electrical switching apparatus can safely be considered definitively closed. An over-toggle mechanism has the advantage of this definite band for sensing fully closed, whereas the closed position is less discretely defined on an under-toggle mechanism.
The described closing protection mechanism may also be used as a “trip unit auxiliary switch” that is used on advanced trip units for communicating electrical switching apparatus status, counting close-open operations, and collecting or communicating similar data. Other advantages include its low cost, compactness and mechanical simplicity. It does not require a “mechanical memory” device with its critical balance of force, mass and friction. It is also less susceptible to mechanical shock and insensitive to the electrical switching apparatus orientation.
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As used herein, “coupled” means a link between two or more elements, whether direct or indirect, so long as a link occurs.
As used herein, “directly coupled” means that two elements are directly in contact with each other.
As used herein, “fixedly coupled” or “fixed” means that two components are so coupled move as one.
As used herein, “operatively engage” when used in relation to a component that is directly coupled to a cam means that a force is being applied by that component to the cam sufficient to cause the cam to rotate.
As shown in
The electrical switching apparatus 10 also includes at least two, and typically a plurality, of side plates 27. The side plates 27 are disposed within the housing assembly 12 in a generally parallel orientation. The side plates 27 include a plurality of openings 29 to which other components may be attached or through which other components may extend. As discussed below, the openings 29 on two adjacent side plates 27 are typically aligned. While side plates 27 are the preferred embodiment, it is understood that the housing assembly 12 may also be adapted to include the required openings and/or attachment points thereby, effectively, incorporating the side plates 27 into the housing assembly 12 (not shown).
An electrical switching apparatus 10 may have one or more poles, that is, one or more pairs of separable contacts 26 each having associated conductors and terminals. As shown in the Figures, the housing assembly 12 includes three chambers 13A, 13B, 13C each enclosing a pair of separable contacts 26 with each being a pole for the electrical switching apparatus 10. A three-pole configuration, or a four-pole configuration having a neutral pole, is well known in the art. The operating mechanism 50 is structured to control all the pairs of separable contacts 26 within the electrical switching apparatus 10. Thus, it is understood selected elements of the operating mechanism 50, such as, but not limited to, the pole shaft 56 (discussed below) span all three chambers 13A, 13B, 13C and engage each pair of separable contacts 26. The following discussion, however, shall not specifically address each specific pair of separable contacts 26.
As shown in
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It is noted that, as shown in
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It is noted that an axis extending through the pivot points for each link 70, 72 defines the lines of force acting through the toggle assembly 58. The toggle assembly 58 is structured to move between a first, collapsed configuration (
In the first, collapsed configuration, the first and second link outer ends 74, 76 are generally closer together than when the toggle assembly 58 is in the second, over-toggle configuration. Thus, because the first link outer end 74 is a fixed pivot point, as the toggle assembly 58 moves between the first, collapsed configuration and the second, over-toggle configuration, the second link outer end 76 is drawn toward, or pushed away from, the first link outer end 74. This motion causes the pole shaft 56 to move between its first and second positions. That is, when the toggle assembly 58 is in the first, collapsed configuration, the pole shaft 56 is in its first position, and, as noted above, the movable contact 34 is in its first, open position. Further, when the toggle assembly 58 is in the second, over-toggle configuration, the pole shaft 56 is in its second position, and, as noted above, the movable contact 34 is in its second, closed position.
The ram assembly 60 has at least one biasing device 89, preferably a compression spring 90, a guide assembly 92, and a ram body 94. The ram body 94, preferably, includes a generally flat forward surface 96 that is structured to engage the toggle joint 82, and more preferably the toggle roller 86. The ram body 94 may be solid but, in a preferred embodiment, the ram body 94 is substantially hollow having a loop-like side wall 95 (
The guide assembly 92 further includes a base plate 110 and a stop plate 112. Each pin 104, 106 has a base end 114 and a tip end 116. Each pin base end 114 is coupled to the base plate 110 and each pin tip end 116 is coupled to the stop plate 112 (
The at least one spring 90 is structured to bias the ram body 94 from the first, retracted position toward the second, extended position. When the ram body 94 is in the first, retracted position, the at least one spring 90 is charged or compressed. When the ram body 94 is in the second, extended position, the at least one spring 90 is discharged. Preferably, the at least one spring 90 is disposed between the base plate 110 and a ram body back surface 97 (
As shown in
The rocker arm assembly 136 includes an elongated body 160 having a pivot point 162, a cam follower 164, and a ram body contact point 166. The rocker arm assembly body 160 is pivotally coupled to housing assembly 12 and/or side plates 27 at the rocker arm body pivot point 162. The rocker arm assembly body 160 may rotate about the rocker arm body pivot point 162 and is structured to move between a first position, wherein the rocker arm body ram body contact point 166 is disposed adjacent to the base plate 110, and a second position, wherein the rocker arm body ram body contact point 166 is adjacent to the stop plate 112. As used immediately above, “adjacent” is a comparative adjective relating to the positions of the rocker arm assembly body 160. The rocker arm body ram body contact point 166 is structured to engage and move the ram body 94. As shown, the rocker arm body ram body contact point 166 engages a bearing 101 (
The closing assembly 54 is assembled in the housing assembly 12 as follows. The toggle assembly 58 is disposed with the first link outer end 74 being rotatably coupled to the housing assembly 12 and/or side plates 27. The second link outer end 76 is rotatably coupled to the pole shaft 56 and, more specifically, rotatably coupled to a mounting point 66. The ram assembly 60 is disposed adjacent to the toggle assembly 58 with the ram body forward surface 96 adjacent to the toggle joint 82. That is, the toggle assembly 58 and the ram assembly 60 are positioned relative to each other so that the toggle joint 82 is disposed within the ram body 94 path of travel. More specifically, the toggle joint 82 also moves through a path as the toggle assembly 58 moves between the first, collapsed configuration and the second, over-toggle configuration. The path of the toggle joint 82 is disposed, generally, within the ram body 94 path of travel. Thus, the ram body 94 is structured to engage the toggle joint 82. In a preferred embodiment, the ram body 94 path of travel does not extend to the position of the toggle joint 82 when the toggle assembly 58 is in the second, over-toggle configuration.
The rocker arm assembly 136 assembly is disposed within the housing assembly 12 adjacent to the ram assembly 60. More specifically, the rocker arm body ram body contact point 166 is disposed so as to contact the forward side, that is the side opposite the at least one spring 90, of a ram body roller 100. In this configuration, rotation of the cam 134 causes the ram body 94 to move between the second, extended position and the first, retracted position. That is, assuming the ram body 94 is in the second, extended position and the cam follower 164 is disposed on the outer cam surface 150 at a point adjacent to the outer cam surface point of minimal radius 152, then the rocker arm assembly body 160 is in the second position. Upon actuation of the charging operator 130, the cam shaft 132 and the cam 134 rotate causing the cam follower 164 to move over the outer cam surface 150. At the point where the cam follower 164 engages the outer cam surface 150, the relative radius of the outer cam surface 150 increases with the continued rotation. As the relative radius of the outer cam surface 150 is increasing the rocker arm assembly body 160 is moved to the first position. As the rocker arm assembly body 160 is moved to the first position, the rocker arm body ram body contact point 166 engages the ram body bearing 101 and moves the ram body 94 to the first position, thereby compressing the at least one spring 90. When the ram body 94 is moved to the first position, the rocker arm body cam follower 164 is disposed at the stop radius 155. When the rocker arm body cam follower 164 is disposed on the stop radius 155, the force from the at least one spring 90 is transferred via the ram body 94 and the rocker arm assembly body 160 to the cam 134. That is, the force is being applied in a generally radially inward direction. Because the cam radius at the stop radius 155 is less than at the cam point of greatest radius 154, the cam 134 is encouraged to rotate away from the cam point of greatest radius 154, i.e. toward the step 156. The rotation of the cam shaft 132 is controlled by the latch assembly 180, discussed below.
In this position, any further rotation of the cam 134 will allow the rocker arm body cam follower 164 to fall over the step 156. After the rocker arm body cam follower 164 falls over the step 156, the rocker arm body cam follower 164 does not operatively engage the cam 134. That is, while there may be some minor force applied to the cam 134 by the rocker arm body cam follower 164, this force is not significant, does not cause the cam 134 to rotate, and does not cause significant wear and tear on the cam 134. It is noted that the cam 134 may rotate due to momentum imparted by the rocker arm body cam follower 164 prior to the rocker arm body cam follower 164 to falling over the step 156. Further, as the rocker arm body cam follower 164 falls over the step 156, the rocker arm assembly body 160 is free to move to the second position as the rocker arm body cam follower 164 is now disposed adjacent to the outer cam surface point of minimal radius 152. It is observed that, when the rocker arm body cam follower 164 is disposed at the outer cam surface stop radius 155, the cam 134 engaging the rocker arm assembly 136, which further engages the ram assembly 60, maintains the at least one spring 90 in the charged state.
The cam 134 and the rocker arm assembly 136 are maintained in the charged configuration by a latch assembly 180. The latch assembly 180 includes a latch lobe 182, a latch roller 184, latch prop 186 and a latch D-shaft 188. The latch lobe 182 is fixed to the cam shaft 132 and maintains a specific orientation relative to the cam 134. The latch roller 184 is rotatably coupled to the latch prop 186 and is structured to roll over the surface of the latch lobe 182. The latch prop 186 has an elongated, generally flat body 190 having a latch roller 184 mounting 192, a pivot point 194 and a latch edge 196. The latch prop body 190 is pivotally coupled to a side plate 27 and is structured to pivot, or rock, between a first position (
In this configuration, the closing assembly 54 operates as follows. For the sake of this discussion the electrical switching apparatus 10 will be initially described in the typical condition following an over current condition. That is, the at least one pair of separable contacts 26 are in the first, open position, the pole shaft 56 is in the first position, the toggle assembly 58 is in the first configuration, the ram body 94 is in the first position and the at least one spring 90 is charged, and the rocker arm assembly body 160 is in the first position. To close the at least one pair of separable contacts 26, an operator actuates the latch assembly 180 to allow the latch D-shaft 188 to rotate as set forth above. When the cam shaft 132 is no longer retained by the latch assembly 180, the cam 134 rotates slightly so as to allow the rocker arm body cam follower 164 to fall over the step 156. When the rocker arm body cam follower 164 falls over the step 156, the rocker arm assembly body 160 is free to move to the second position as the rocker arm body cam follower 164 now engages the outer cam surface 150 at a point adjacent to the outer cam surface point of minimal radius 152. At this point, the at least one spring 90 is no longer restrained and the at least one spring 90 moves the ram body 94 from the first, retracted position toward the second, extended position. As the ram body 94 moves from the first, retracted position toward the second, extended position, the ram body forward surface 96 engages the toggle joint 82 and causes the toggle assembly 58 to move from the first, collapsed configuration to the second, over-toggle configuration. As noted above, the ram body 94 path of travel does not extend to the position of the toggle joint 82 when the toggle assembly 58 is in the second, over-toggle configuration. Preferably, the ram body 94 moves with sufficient speed and energy so that, when the ram body 94 reaches the end of the path of travel, the toggle assembly 58 is a few degrees over toggle but not at its final over toggle resting point. Once the toggle assembly 58 is over the toggle point by only a few degrees, the forces of the at least one spring 90 and whatever the remaining momentum of the ram body 94 continue the motion of the toggle assembly 58 towards the second, over-toggle configuration, thereby creating a space between the ram body forward surface 96 and the toggle joint 82.
As the toggle assembly 58 is moved into the second, over-toggle configuration, the pole shaft 56 is also moved into its second position. As the pole shaft 56 is moved into its second position, the at least one pair of separable contacts 26 are moved from the first, open position to the second closed position. At this point the closing operation is complete, however, it is preferred that the operator again engages the charging operator 130 to cause the cam 134 to rotate so that the outer cam surface point of greatest radius 154 again engages the cam follower 164. As described above, the rotation of the cam 134 to this position acts to charge the at least one spring 90. Thus, the at least one spring 90 is charged and ready to close the at least one pair of separable contacts 26 following another over current condition.
The toggle assembly 58 further includes a closing protection mechanism 200. The closing protection mechanism 200 includes a control unit 202, a sensing switch 204, and a sensing switch actuator 206. The control unit 202, preferably, includes a programmable logic circuit and is structured to receive a sensing switch signal and to provide a control signal to the trip device 40. The control unit 202, shown schematically, may be incorporated into the trip device 40, shown schematically. The sensing switch 204 is coupled to, and in electronic communication with, the control unit 202 and is structured to provide a sensing switch signal to the control unit 202. The sensing switch 204 is disposed adjacent to the toggle assembly 58. The sensing switch 204, preferably, has a housing 210 and an actuator member 212. The sensing switch actuator member 212 is pivotally coupled to the sensing switch housing 210. The sensing switch actuator member 212 is structured to pivot between a first, unactuated position (
The sensing switch actuator 206 is structured to actuate the sensing switch 204. That is, in the preferred embodiment, the sensing switch actuator 206 is structured to engage and move the sensing switch actuator member 212 from the first, unactuated position to the second, actuated position. In the preferred embodiment, the sensing switch actuator 206 is a cam lobe 208 disposed at the first link outer end 74.
In this configuration, the sensing switch 204 is disposed adjacent to the pivot point at the first link outer end 74. When the toggle assembly 58 is in the first, collapsed configuration, the sensing switch cam lobe 208 does not engage the sensing switch actuator member 212. Preferably, as the toggle assembly 58 moves into the in-line configuration, the sensing switch actuator 206 initially engages the sensing switch actuator member 212. Then, as the toggle assembly 58 moves into the second, over-toggle configuration, the sensing switch actuator 206 moves the sensing switch actuator member 212 from the first position to the second position. When the toggle assembly 58 moves into the second, over-toggle configuration, the sensing switch 204 generates the sensing switch signal and provides the sensing switch signal to the control unit 202. The control unit 202, in turn, provides the control signal to the trip device 40.
In an alternate embodiment, shown in ghost in
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
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|---|---|---|---|
| 5762181 | Castonguay et al. | Jun 1998 | A |
| 5906271 | Castonguay et al. | May 1999 | A |
| 6610949 | Mori et al. | Aug 2003 | B2 |
| 6646216 | Fanta et al. | Nov 2003 | B2 |
| 6864450 | Chen et al. | Mar 2005 | B1 |
| 7319203 | Briggs et al. | Jan 2008 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20080302645 A1 | Dec 2008 | US |
