Patent Grant
7420133
The present invention relates generally to mechanical door safety interlocks for use with circuit breakers, and more particularly to a simple, mechanical rotary circuit breaker door safety interlock for installation and use in an enclosure having a hinged door to operate a rotary circuit breaker that is actuated by rotation of a shaft that is operated by a handle located on and accessible from the outside of the enclosure with the hinged door closed.
For safety reasons, high-power electrical or electronic devices which contain voltages lethal to people are housed in enclosures that have locking doors. The enclosures are either made from electrically insulating, fireproof material, or they are made of metal and are electrically connected to earth (or safety) ground with large conductors so that if anything inside the enclosure breaks, arcs, explodes, or otherwise malfunctions, the lethal voltage is contained within the enclosure. The enclosure prevents any significant voltage from escaping to the exterior of the enclosure, irrespective of what occurs inside the enclosure.
In such enclosures that contain high-power electrical or electronic devices and/or switchgear, there is often a circuit breaker (which is in essence a disconnect switch) that is placed in series with the incoming electrical power line. This circuit breaker is coupled to a handle that is located on the outside of the enclosure, which handle may be manipulated to operate the circuit breaker located inside the enclosure to turn the electrical power in the enclosure on or off. To protect people from the hazardous voltage that is present inside the enclosure, the circuit breaker is often mechanically interlocked with the enclosure door so that the door cannot be opened when the handle is in the on position.
This mechanical interlocking function is typically performed by an interlock mechanism that is mechanically linked to a circuit breaker that is mounted inside the enclosure. One common type of circuit breaker is a rotary circuit breaker that is actuated by a rotating shaft operated by a handle located on the outside of the enclosure (typically on a bracket that is accessible through an opening located in the door of the enclosure). The handle is rotated between ON and OFF positions to operate the rotary circuit breaker. Rotation of the handle from the OFF position to the ON position actuates the interlock mechanism to cause it to lock the enclosure door closed, and rotation of the handle from the ON position to the OFF position allows the enclosure door to open. The interlock switch should also prevents the power switch from moving from the OFF position to the ON position while the enclosure door is open.
A number of interlock mechanisms have been proposed to date, one of which is illustrated for purposes of example in U.S. Pat. No. 4,835,350, to Ozu et al. This mechanism shown in the Ozu et al. patent represents an improvement over earlier such devices inasmuch as the Ozu et al. mechanism is simpler and has fewer parts. However, the Ozu et al. mechanism still uses two pivoting members and a spring to push the pivoting members into position to engage an interlocking arm. Also, should the spring used by the Ozu et al. mechanism wear out or break, the Ozu et al. mechanism would be rendered ineffective.
The present invention is a mechanical door safety interlock device for use with a rotary circuit breaker that is installed in a enclosure with a hinged door. The door safety rotary circuit breaker interlock of the present invention functions to prevent the enclosure door from being opened unless the rotary circuit breaker has been actuated to turn the power off in the enclosure. It also prevents the rotary circuit breaker from being actuated to turn the power on in the enclosure power when the enclosure door is open. As such, the door safety rotary circuit breaker interlock has safety as its primary goal, ensuring that power coming into the enclosure via the rotary circuit breaker is off whenever the enclosure door is open, thereby exposing electrical components contained in the enclosure which are connected to hazardous voltages only when the enclosure door is closed and the rotary circuit breaker is subsequently placed in the on position.
The door safety rotary circuit breaker interlock of the present invention is designed for use with a rotary circuit breaker that is driven between off and on positions with a rotating mechanism. The rotating mechanism on the rotary circuit breaker is coupled to an actuating handle that is located on and accessible from the outside of the enclosure via a rotating actuation shaft. This shaft typically has a square cross-section, with both the portion of the rotary circuit breaker and the portion of the handle that respectively engage the shaft having a matching square configuration.
The door safety rotary circuit breaker interlock of the present invention includes four essential components: a mounting bracket, a tongue bracket, a latch plate, and a door hook. The mounting bracket is mounted to the enclosure, and has a front plate that is typically received by an aperture in the enclosure door such that the outer surface of the front plate of the mounting bracket is both visible and accessible from outside the enclosure when the enclosure door is closed. The handle, which is typically packaged with the rotary circuit breaker, is mounted on the outer surface of the front plate of the mounting bracket, with the mounting bracket being mounted to the enclosure. The actuation shaft is located between and engaged with both the handle mounted on the mounting bracket in the enclosure and the rotary circuit breaker, which is also mounted in the enclosure.
The tongue bracket is mounted onto the actuation shaft, and includes a tongue that is supported in parallel to and spaced away from the actuation shaft such that the tongue will rotate as the actuation shaft is rotated by the handle. The latch plate is mounted on the back side of the front plate of the mounting bracket for rotation about the mounting point of the latch plate on the front plate. The latch plate has a notch located therein which engages the tongue of the tongue bracket. The latch plate is mounted onto the front plate of the mounting bracket so that gravity will cause the latch plate to move such that the notch in the latch plate moves toward the actuation shaft so that it can engage the tongue of the tongue plate when the shaft is in a certain position.
The door hook is mounted on the back side of the door in a position where it can be selectively engaged by the distal end of the latch plate. When the handle is in the OFF position and the enclosure door is open, the tongue of the tongue bracket is engaged by the notch in the latch plate and the handle cannot be rotated to the ON position. The latch plate is moved to this position by gravity. When the enclosure door is closed, the door hook moves the latch plate (against the force of gravity) to a position in which the notch in the latch plate no longer engages the tongue of the tongue bracket, thereby allowing the handle to be rotated to the ON position.
When the handle is moved from its ON position to its OFF position, the tongue of the tongue bracket is placed in a position to engage the notch in the latch plate. In this exemplary embodiment, the handle must be rotated approximately five degrees past the OFF position in order for the tongue of the tongue bracket to drive the latch plate to a position in which the latch plate no longer engages the door hook, allowing the enclosure door to be opened. In another embodiment, the door can be opened when the handle is in the OFF position. Optionally, the movement of the latch plate by gravity can also be assisted through the addition of a spring.
It may be appreciated that the door safety rotary circuit breaker interlock of the present invention represents both a simplification to and an improvement upon other interlock devices that have been known in the past. Aside from the handle and the actuation shaft which are used to turn the rotary circuit breaker on and off and the door hook mounted on the back side of the enclosure door, the door safety rotary circuit breaker interlock of the present invention has only one moving part, namely the latch plate. No complex linkages or springs are either used or required for the door safety rotary circuit breaker interlock to operate, since gravity provides all the force that is necessary to move the latch plate from its unlocked position to its locked position.
These and other advantages of the present invention are best understood with reference to the drawings, in which:
It will be appreciated by those skilled in the art that the door safety rotary circuit breaker interlock of the present invention is intended for use with a rotary circuit breaker (not shown in
An exemplary embodiment of the door safety rotary circuit breaker interlock of the present invention is illustrated in
Referring first to
Located in the rectangular front plate 42 of the mounting bracket 40 is a large aperture 44 surrounded by four smaller apertures 46. The aperture 44 and the apertures 46 are for mounting a handle 48 on the front side of the rectangular front plate 42. The back side of the handle 48 has two threaded apertures 50 located on a base 52 of the handle 48 on opposite sides thereof to facilitate mounting of the handle 48.
Two bolts 54 extend through two of the apertures 46 in the rectangular front plate 42 and are screwed into the threaded apertures 50 in the base 52 of the handle 48 to mount the handle 48 onto the rectangular front plate 42. The handle 48 has a square aperture 56 accessible from the back side thereof that is rotatably driven by rotation of the handle 48 on the base 52. It will be appreciated by those skilled in the art that the handle 48 rotates with respect to the base 52 to drive the square aperture 56.
The mounting bracket 40 has a rearwardly-extending top plate 58 and a rearwardly-extending bottom plate 60. Located on the right side of the top plate 58 (as the mounting bracket 40 would be viewed from the front side thereof) near the rear side thereof is a mounting flange 62 having a rearwardly-opening (as viewed from the front side of the mounting bracket 40) slot 64 located therein. Located on the right side of the bottom plate 60 (as the mounting bracket 40 would be viewed from the front side thereof) near the rear side thereof is a mounting flange 66 having a rearwardly-opening (as viewed from the front side of the mounting bracket 40) slot 68 located therein. The slots 64 and 68 will receive mounting hardware such as bolts (not shown in
Located in the bottom plate 60 in a position that is near to but spaced slightly from the rectangular front plate 42 is a slot 70 through which an operative component of the door safety rotary circuit breaker interlock of the present invention will extend. The slot 70 is located nearer to the side of the bottom plate 60 on which the mounting flange 66 is mounted than it is to the opposite side of the bottom plate 60.
The right and left sides of the rectangular front plate 42 (as viewed from the front side of the mounting bracket 40) have rearwardly-extending flanges 72 and 74, respectively. The flange 72 two threaded inserts 76 and 78 mounted therein near the top and the bottom thereof, respectively. The threaded inserts 76 and 78 may be used together with the slots 64 and 68 to facilitate mounting the mounting bracket 40 into an enclosure (not shown in
A flat-sided aperture 80 is located in the rectangular front plate 42 above the aperture 44, with the centerline of the flat-sided aperture 80 being somewhat to the left 42 of the centerline of the aperture 44 (as viewed from the front side of the mounting bracket 40). The configuration of the flat-sided aperture 80 is circular with flat sides. The flat-sided aperture 80 will be used to receive mounting hardware shown in
Referring next to
The latch plate has a distal end indicated generally by the reference numeral 86, which distal end 86 will extend downwardly through the slot 70 in the bottom plate 60 of the mounting bracket 40. It is the lateral movement of this distal end 86 that will be used to latch the enclosure door closed, as will become apparent below. The latch plate 82 has flange 88 located on an intermediate portion of the left side of the latch plate 82 and extending toward the direction faced by the back side of the latch plate 82 as it is shown in
The latch plate 82 has a notch 90 located in the right side of the latch plate 82 as it is shown in
Referring next to
A rotatable member 112 has a cylindrical outer configuration that is sized to fit the aperture 108 in the sleeve 102 in a rotatable fashion. The rotatable member 112 has an outwardly extending annular flange 114 located at one end thereof and a square extension 116 located at the opposite end thereof. The surface of the end of the rotatable member 112 having the flange 114 thereupon has a slot 118 located therein to permit it to be driven by a flat-bladed screwdriver or the like. The end of the rotatable member 112 having the square extension 116 thereupon has a threaded aperture 120 located therein.
That end of the rotatable member 112 is inserted into the end of the sleeve 102 having the annular flange 104 thereupon, and the square extension 116 extends fully out of the end of the sleeve 102 having the threaded portion 106 thereupon. A retaining ring 122 is interference-fit onto the square extension 116 to retain the rotatable member 112 in the sleeve 102. The outer diameter of the retaining ring 122 is larger than the inner diameter of the aperture 108, but smaller than the outer diameter of the threaded portion 106 of the sleeve 102.
The assembly consisting of the sleeve 102, the rotatable member 112, and the retaining ring 122 is inserted into the flat-sided aperture 80 in the rectangular front plate 42 of the mounting bracket 40 with the annular flange 104 of the sleeve 102 located on the front side of the rectangular front plate 42 and the threaded portion 106 of the sleeve 102 extending through the flat-sided aperture 80 to the back side of the rectangular front plate 42. A shoulder nut 124 is then screwed onto the threaded portion 106 of the sleeve 102, retaining the sleeve 102 in position in the rectangular front plate 42 of the mounting bracket 40.
The square hole 84 in the latch plate 82 is then placed onto the square extension 116 of the rotatable member 112, with the distal end 86 of the latch plate 82 extending through the slot 70 in the bottom plate 60 of the mounting bracket 40. A small bolt 126 is then inserted through a lock washer 128 and a flat washer 130, and then is screwed into the threaded aperture 120 in the rotatable member 112 to retain the latch plate 82 on the mounting hardware, thereby pivotally mounting the latch plate 82 on the mounting bracket 40. As mentioned above, when the latch plate 82 is so mounted, the flange 88 maintains its position in spaced-away fashion from the back side of the rectangular front plate 42 of the mounting bracket 40.
It will thus be appreciated by those skilled in the art that the latch plate 82 is mounted in the mounting bracket 40 for pivoting movement about the square hole 84 in the latch plate 82. The pivoting movement of the latch plate 82 is limited by the engagement of the distal end 86 of the latch plate 82 with the slot 70 in the bottom plate 60 of the mounting bracket 40. The location of the square hole 84 in the latch plate is well off-center, so when the door safety rotary circuit breaker interlock is mounted in the orientation shown in
Referring next to
The tongue bracket 132 and the tongue bracket mounting plate 134 are made of flat pieces of steel or another durable metal or material. The tongue bracket 132 is L-shaped, with a ninety-degree bend located therein. The base 138 of the “L” of the tongue bracket 132 has a square aperture 140 located therein adjacent the leg 142 of the “L” that is sized to admit the actuation shaft 136. The tongue bracket 132 is shown mounted on the actuation shaft 136 in
The tongue bracket mounting plate 134 is approximately the same size and configuration as the leg 142 of the “L” of the tongue bracket 132. The tongue bracket 132 has four apertures 144 located in the base 142 of the “L” of the tongue bracket 132 and four threaded apertures 146 located in the base 142 of the “L” of the tongue bracket 132 as well. The tongue bracket mounting plate 134 has four threaded apertures 148 located therein and four apertures 150 located therein as well.
When the tongue bracket mounting plate 134 is located immediately on the opposite side of the actuation shaft 136 from the tongue bracket 132 (as shown in
Located at the end of the base 138 of the “L” of the tongue bracket 132 that is distal to the leg 142 of the “L” of the tongue bracket 132 is a tongue 154 that extends from the base 138 of the “L” of the tongue bracket 132 in a direction opposite the direction that the leg 142 of the “L” of the tongue bracket 132 extends from the base 138 of the “L” of the tongue bracket 132. Thus, it will be appreciated that the tongue 154 extends in a direction parallel to and spaced away from the actuation shaft 136, and is located near the end of the actuation shaft 136 which will be driven by the square aperture 56 in the handle 48. The tongue 154 and the base 138 of the “L” of the tongue bracket 132 are preferably made of a single flat piece of steel or another durable metal or material.
When the door safety rotary circuit breaker interlock of the present invention is assembled and operating, the tongue 154 will engage with the notch 90 in the latch plate 82. It will be appreciated by those skilled in the art that the tongue 154 could be suspended from the actuation shaft 136 in a variety of different ways. For example, the tongue 154 could instead be a Z-shaped piece of metal that is rigidly attached to the shaft 136 by welding, clamping or other means suitable for a reliable connection.
Referring next to
The flange 158 has two slots 160 and 162 located therein, which slots 160 and 162 may be used to facilitate mounting the door hook 156 onto the back side of an enclosure door (not shown in
The door hook 156 has a latching area 164 that extends orthogonally outwardly from the side of the door hook 156 at a location that is spaced slightly away from the flange 158. When the enclosure door is closed, the latching area 164 of the door hook 156 will engage the distal end 86 of the latch plate 82 to secure the enclosure door in a closed position on the enclosure. The end of the door hook 156 that is distal from the flange 158 has a tapered engagement area 166 that extends outwardly at an angle until it intersects with the latching area 164. The engagement area 166 will initially engage the distal end 86 of the latch plate 82 as the enclosure door is being closed, moving the distal end 86 of the latch plate 82 aside until the engagement area 166 passes the distal end 86 of the latch plate 82, whereupon the distal end 86 of the latch plate 82 will be engaged by the latching area 164.
Referring next to
Mounted on the enclosure 170 is an enclosure door 174, which is hinged on the left side of the enclosure 170 using a hinge 176. Centrally located on the side of the enclosure door 174 opposite the hinge 176 is a square aperture 178 that will receive the rectangular front plate 42 of the mounting bracket 40 therein when the enclosure door 174 is closed on the enclosure 170. The door hook 156 is mounted on the back side of the enclosure door 174 below the square aperture 178. The door hook 156 is positioned and oriented to engage the distal end 86 of the latch plate 82 when the enclosure door 174 on the enclosure 170. The details of the engagement of the door hook 156 with the distal end 86 of the latch plate 82 will be discussed below in conjunction with
The size of a typical enclosure 170 is approximately 0.8 meters wide, 1.2 meters high, and 0.3 meters deep. The door safety rotary circuit breaker interlock of the present invention is designed to lock the enclosure door 174 on the enclosure 170 when the enclosure door 174 is closed through the engagement of the door hook 156 with the distal end 86 of the latch plate 82.
Referring next to
Referring then to
It will be appreciated by those skilled in the art that the door safety rotary circuit breaker interlock of the present invention does not require a spring or any other biasing means, relying instead only on gravity). All of the force necessary to move the door safety rotary circuit breaker interlock to a locked configuration is provided by gravity acting upon the weight of the latch plate 82. This provides an extra measure of reliability, because there are no springs to break or fall out of the door safety rotary circuit breaker interlock into the enclosure 170. Also, the door safety rotary circuit breaker interlock cannot fail to operate as intended due to a broken or missing spring.
However, a spring 180 may optionally used as a redundant force to urge the latch plate 82 in a counterclockwise direction (as viewed in
Referring next to
Referring now to
To overcome the weight of the latch plate 82 and the friction of the tongue 154 as it contacts the top lip 94 of the latch plate 82, it will be appreciated that some force is required. The requirement of this additional force to rotate the actuation shaft 136 the additional five degrees clockwise (as viewed in
Referring next to
This is also the position that the latch plate 82, the actuation shaft 136, and the tongue 154 will be in as the enclosure 170 is beginning to be shut. In this position, the engagement area 166 of the door hook 156 is just about to contact the distal end 86 of the latch plate 82, which contact will cause the latch plate 82 to begin to be rotated clockwise (as viewed in
Referring now to
Referring next to
It will be appreciated by those skilled in the art that on occasions it may be desirable to allow the rotary circuit breaker 172 to be turned ON by maintenance personnel without first closing the enclosure door 174. Doing so requires moving the latch plate 82 to the position in which it is shown in
This is easy to do when the enclosure door 174 is open, since the distal end 86 of the latch plate 82 extends downwardly from the bottom of the mounting bracket 40 and is thus quite accessible. However, the location of the handle 48 on the mounting bracket 40 relative to the location of the distal end 86 of the latch plate 82 and the force required to rotate the handle 48 are such that it is not possible to simultaneously move the distal end 86 of the latch plate 82 and rotate the handle 48 with a single hand. This ensures that power may not be turned on by someone with one hand while the other hand is in contact with areas of hazardous voltages inside the enclosure 170.
It may also be desirable to allow a closed enclosure door 174 to be opened by maintenance personnel without the rotary circuit breaker 172 first being turned OFF. This is facilitated by the mounting hardware that is used to pivotally mount the latch plate 82 on the mounting bracket 40. By using a screwdriver (not shown) to engage the slot 118 in the rotatable member 112, the latch plate 82 can be manually rotated out of engagement with the tongue 154, thereby allowing the enclosure door 174 to be opened without first turning the rotary circuit breaker 172 being OFF, and to allow the rotary circuit breaker 172 to be turned ON without first closing the enclosure door 174. The size and shape of the flange 114 of the rotatable member 112 together with the weight of the latch plate 82 makes it impossible to rotate the flange 114 of the rotatable member 112 by hand, thereby ensuring that a screwdriver is required. This feature ensures that an intentional action with a tool is required to open the enclosure door 174 while the rotary circuit breaker 172 is ON, thereby ensuring that the enclosure door 174 cannot be opened inadvertently.
A modified version of the door safety rotary circuit breaker interlock of the present invention is shown in
This alternative embodiment may be used if the safety feature that requires a deliberate action to rotate the handle 48 past its OFF position in order to unlock the enclosure door 174 is not desired or if it is not possible due to the characteristics of the rotary circuit breaker 172 being used. Another way of achieving the same operation would be to change the mounting position of the latch plate 82 in the mounting bracket 40 to move it downwardly (as shown in
The exemplary embodiments shown in
For example, in
A tongue 210 extending from a tongue bracket 212 mounted on an actuation shaft 214 is shown in engagement with a notch 216. This is the OFF position, and the distal end 204 of the latch plate 200 is beginning to be engaged by the door hook 208 as the enclosure door is approaching its closed position. In this position, the tongue 210 is engaged by the notch 216, thereby preventing the actuation shaft 214 from being rotated in a counterclockwise direction (as shown in
A tongue 226 extending from a tongue bracket 228 mounted on an actuation shaft 230 is shown in engagement with a notch 232 located on the downwardly-facing side of the latch plate 220 (as shown in
Referring next to
A tongue 246 extending from a tongue bracket 248 mounted on an actuation shaft 250 is shown in engagement with a notch 252 located on the downwardly-facing side of the latch plate 240 (as shown in
Referring finally to
A tongue 266 extending from a tongue bracket 268 mounted on an actuation shaft 270 is shown in engagement with a notch 272 located on the downwardly-facing side of the end of the latch plate 260 that is opposite the distal end 264. This is the OFF position, and the distal end 264 of the latch plate 260 is beginning to be engaged by a door hook 274 as the enclosure door is approaching its closed position. In this position, the tongue 266 is engaged by the notch 272, thereby preventing the actuation shaft 270 from being rotated in a counterclockwise direction (as shown in
It may therefore be appreciated from the above detailed description of the exemplary embodiments of the door safety rotary circuit breaker interlock of the present invention that it represents both a simplification to and an improvement upon other interlock devices that have been known in the past. Aside from the handle and the actuation shaft which are used to turn the rotary circuit breaker on and off and the door hook mounted on the back side of the enclosure door, the door safety rotary circuit breaker interlock of the present invention has only one moving part, namely the latch plate. No complex linkages or springs are either used or required for the door safety rotary circuit breaker interlock to operate, since gravity provides all the force that is necessary to move the latch plate from its unlocked position to its locked position.
Although the foregoing description of the door safety rotary circuit breaker interlock of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
This application claims priority of U.S. Provisional Patent Application No. 60/840,858, which is entitled “Door Interlock for Rotary Actuated Power Switch,” and which was filed on Aug. 29, 2006, the entirety of which application is hereby incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2954444 | Jones et al. | Sep 1960 | A |
| 3122615 | Chace | Feb 1964 | A |
| 3192334 | Dimond et al. | Jun 1965 | A |
| 3299233 | Sciba | Jan 1967 | A |
| 3313896 | Gray | Apr 1967 | A |
| 3970808 | Gryctko et al. | Jul 1976 | A |
| 3980845 | Gryctko et al. | Sep 1976 | A |
| 4074091 | Bischof et al. | Feb 1978 | A |
| 4405844 | Dizon et al. | Sep 1983 | A |
| 4835350 | Ozu et al. | May 1989 | A |
| 4926286 | Maki et al. | May 1990 | A |
| 5493083 | Olivier | Feb 1996 | A |
| 5493084 | Whitaker | Feb 1996 | A |
| 5963420 | Bailey et al. | Oct 1999 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20080053797 A1 | Mar 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60840858 | Aug 2006 | US |
