Patent Application
20110232039
1. Field
The disclosed concept pertains generally to handle operators and, more particularly, to handle operators which extend beyond a flash protection boundary of, for example, a motor control center.
2. Background
A flash protection boundary (“FPB”) is implemented and regulated to protect those that work around live electrical equipment from severe injury resulting from an arc flash. An arc flash is a type of electrical explosion that can result from a low impedance electrical connection to ground or a voltage phase in an electrical system. For example, when insulation or isolation between electrified conductors is breached or can no longer withstand the applied voltage, an arc flash can occur. An arc flash can cause substantial damage, fire or injury. An enormous amount of concentrated energy can explode outward from the electrical equipment, spreading hot gases, melting metal, causing death or severe burns and creating intense pressure that can damage hearing or brain function and light that can damage eyesight. The fast-moving pressure wave also can send loose material, such as pieces of equipment, metal tools and other objects, flying, injuring anyone standing nearby.
An FPB is calculated to determine the distance surrounding the potential arc point inside which qualified workers must be protected when working. In accordance with the National Fire Protection Association (“NFPA”) 70E standard, FPB is defined as the distance from exposed live parts within which a person could receive a second-degree burn if an electrical arc flash were to occur. This standard also defines incident energy as the amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. Incident energy is expressed in calories per cubic centimeter squared (cal/cm2). As workers get closer to the energized equipment, the energy increases. The FPB is different for different types of equipment and depends, in part, on the voltages involved. Typically, the higher the voltages, the larger the danger zone. At voltage levels above 600 volts, the FPB is the distance at which the incident energy is 1.2 cal/cm2, equating to a second-degree burn. For situations where the fault clearing time is 0.1 second (or faster), the FPB is the distance at which the incident energy level equals 1.5 cal/cm2. This is defined by NFPA 70E 130.3(a), second paragraph, and is the burn level at which the skin will just heal without scaring.
In accordance with NFPA regulations, employers are required to perform a hazard analysis to determine FPBs, to provide appropriate protection for employees and to mark with a warning label electrical equipment having a potential for arc flash. A method of determining this boundary is to calculate the magnitude of the arc (a function of the available short circuit current), estimate how long the arc will last (a function of the interrupting time of the fuse or circuit breaker) and then calculate how far away an individual must be to avoid receiving an incident energy of 1.2 cal/cm2.
The FPB distance can be calculated according to EQ. 1 as follows (in accordance with formulae D.3(d) and D.3(e) Modified of NFPA 70E-2004).
FPB=53×MVAbf×T (EQ. 1)
wherein:
FPB represents the flash protection boundary in feet;
MVAbf equals 1.732×V×Isc×0.707/106;
MVAbf represents the bolted fault energy of the arc (MVA);
T represents arcing time (in seconds);
Isc represents bolted short circuit current (in amperes); and
V represents line-to-line voltage (in volts).
All persons crossing the FPB must wear appropriate personnel protective equipment (PPE), such as, but not limited to, protective clothing, for their protection.
In addition to the FPB, there is also a shock protection boundary (“SPB”) which includes a limited approach (“LA”) distance, a restricted approach (“RA”) distance and a prohibited approach (“PA”) distance. The LA distance is the distance an unqualified worker must stay away from energized equipment. The RA distance is the distance that a qualified worker must stay away from energized equipment without voltage rated PPE. The PA distance is the distance considered to be the same as actually touching energized equipment.
An FPB is required around electrical equipment, such as switchboards, panelboards, industrial control panels, motor control centers, and similar equipment, when an individual works on or in the proximity of exposed energized (energized and not enclosed, shielded, covered, or otherwise protected from contact) components. This includes conducting activities, such as examination, adjustment, servicing, maintenance or troubleshooting.
In the case of motor control centers, a motor control center (“MCC”) generally has an assembly of one or more enclosed sections having a common power bus. An MCC can include several motor starters. An MCC is typically used for low-voltage, three-phase, alternating current motors from about 230 volts to about 600 volts. An FPB is calculated for the MCC, and therefore, a worker must typically enter the FPB to perform operations and maintenance on the MCC unit.
The implementation and regulation of FPBs and the provision of PPE afford protection for workers that are required to work in hazardous areas. However, there is room for improvement in removing workers from a hazardous zone. For example, the use of long-handled tools can allow the worker to perform certain operations from outside of the FPB.
These needs and others are met by embodiments of the disclosed concept, which provide a device having at least one handle adaptor for engaging and operating a handle mounted on an electrical switching apparatus.
In an aspect of the disclosed concept, an extendable device for engaging and operating a handle mounted on an electrical switching apparatus is provided. The extendable device includes a first linear portion having a first end and a second end, the first linear portion extending therebetween, and a second linear portion having a first end and a second end, the second linear portion extending therebetween, the second linear portion having an inside surface that forms a chamber and having an inside distance greater than an outside distance of the first linear portion such that the first linear portion is structured to linearly move toward and away from the chamber of the second linear portion; a handle adaptor extending away from the second end of one of the first and second linear portions; and a retainer mechanism structured to engage the first linear portion and the second linear portion such that the extendable device can be adjusted to a particular length and maintained at the particular length, wherein the handle adaptor is structured to engage the handle such that the handle can be moved from a first position to a different second position.
In another aspect of the disclosed concept, a device for engaging and operating a handle mounted on an electrical switching apparatus is provided. The device includes a linear portion having a first end and a second end, the linear portion extending therebetween; a first handle adaptor extending away from the first end of the linear portion; and a second handle adaptor extending away from the second end of the linear portion, wherein each of the first handle adaptor and the second handle adaptor is structured to engage the handle such that the handle can be moved from a first position to a different second position.
In still another aspect of the disclosed concept, an extendable device for engaging and operating a handle mounted on an electrical switching apparatus is provided. The extendable device includes a first linear portion having a first end and a second end, the first linear portion extending therebetween, and a second linear portion having a first end and a second end, the second linear portion extending therebetween, the second linear portion having an inside surface that forms a chamber and having an inside distance greater than an outside distance of the first linear portion such that the first linear portion is structured to linearly move toward and away from the chamber of the second linear portion; a first handle adaptor extending away from the second end of the first linear portion; a second handle adaptor extending away from the second end of the second linear portion; a spring mechanism disposed between the first and second linear portions, the spring mechanism structured to exert a force to linearly move the first linear portion away from the chamber of the second linear portion; and a retainer mechanism structured to engage the first linear portion and the second linear portion such that the extendable device can be adjusted to a particular length and maintained at the particular length, wherein at least one of the first handle adaptor and the second handle adaptor is structured to engage the handle such that the handle can be moved from a first position to a different second position.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
a is an isometric view of an extendable handle operator wherein the handle operator is fully extended in accordance with an embodiment of the disclosed concept.
b is an isometric view of the extendable handle operator of
a is an isometric view of a handle operator having a fixed extension portion and two handle adaptors in accordance with another embodiment of the disclosed concept.
a is an isometric view of an extendable handle operator having a gripping handle and one handle adaptor in accordance with another embodiment of the disclosed concept.
a and 7b are isometric views of a handle operator, wherein the handle operator is engaged with a motor control center disconnect handle in different operational positions in accordance with another embodiment of the disclosed concept.
The disclosed concept is described in association with a handle operator for a motor control center, although the disclosed concept is applicable to handle operators for a wide range of electrical equipment and systems.
Directional phrases used herein, such as, for example, “left,” “right,” “top,” “bottom,” “upper,” “lower,” “front,” “back,” “forward,” “above,” “below,” “clockwise,” “counterclockwise” and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting to the claims unless expressly recited therein.
As employed herein, the statement that two or more parts are “coupled” or “connected” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
The handle operator 1 has a spring mechanism 35 disposed between the first and second linear portions 25,30, and exerts a force to bias the first linear portion 25 away from the chamber 50 of the second linear portion 30. The spring mechanism 35 can include various designs known in the art. The example spring mechanism 35 is a coil spring which is disposed within the chamber 50 of the second linear portion 30 and biases the first linear portion 25. The spring mechanism 35 allows the first linear portion 25 to extend and contract such that the length of the handle operator 1 is extendable and contractable. Further, the handle operator 1 has a retainer mechanism which allows the handle operator 1 to be adjusted to various lengths to maintain the handle operator 1 at a desired length. The example retainer mechanism includes a nub 80 formed on the first linear portion 25 and detents 90 formed on the second linear portion 30. The nub 80 is biased upward to engage one of detents 90. It will be appreciated that a wide range of different retainer mechanisms can be employed. For example, the retainer mechanism can include a double nub and detent formation such that two nubs are formed on a first linear portion and are each positioned 180° apart, and two sets of detents are formed on a second linear portion and each set is positioned 180° apart. The second end 40 of the first linear portion 25 is structured to engage a handle adapter 15. Alternatively, the second end 45 of the second linear portion 30, can engage the same or similar or different handle adaptor. The example handle adaptor 15 extends away from (e.g., without limitation, perpendicular from) the second end 40 of the first linear portion 25. The handle operator 1 can be fabricated such that the handle adaptor 15, the second end 40 and the first linear portion 25 are formed as a single piece or structure. Alternatively, the handle adaptor can be fabricated as a separate piece or structure and connected or otherwise coupled to the second end 40 of the first linear portion 25 by a connector 65 (shown in
The lengths of the first and second linear portions 25,30 and the spring mechanism 35 can vary and can depend on the flash protection boundary (“FPB”) which surrounds particular electrical equipment or systems (not shown). For example, the lengths of the first and second linear portions 25, 30 and the spring mechanism 35 can be such that the total length of the handle operator 1 is extendable beyond the FPB. The example handle operator 1 can be fully extended, fully contracted, or partially extended and contracted. In
a and 2b show another handle operator 1a having the first linear portion 25, the second linear portion 30, the first end 60 and the second end 40 of the first linear portion 25, the first end 70 and the second end 45 of the second linear portion 30, the chamber 50, the nub 80, the detents 90 and handle adaptor 15, as shown in
a shows handle operator 100′ in accordance with an embodiment of the disclosed concept. The handle operator 100′ has the linear portion 130, the first end 140, the second end 145, the first handle adaptor 115 and the second handle adaptor 120, as shown in
The example handle operator 200 has a spring mechanism 235 disposed between the first and second linear portions 225,230, in order to bias the first linear portion 225 away from the chamber 250 of the second linear portion 230. The spring mechanism 235 can include various designs known in the art. The example spring mechanism 235 is a coil spring which is disposed within the chamber 250 of the second linear portion 230 and biases the first linear portion 225. The spring mechanism 235 allows the first linear portion 225 to extend and contract such that the length of the handle operator 200 is extendable and contractable. Further, the handle operator 200 has a retainer mechanism which allows the handle operator 200 to adjust to various lengths and to maintain the handle operator 200 at a desired length. The example retainer mechanism includes a nub 280 formed on the first linear portion 225 and detents 290 formed on the second linear portion 230. The nub 280 is biased upward to engage one of detents 290. The second end 240 of the first linear portion 225 is structured to engage a first handle adapter 215. The second end 245 of the second linear portion 230 is structured to engage a second handle adaptor 220. The example first and second handle adaptors 215, 220 extend away from (e.g., without limitation, perpendicular from) the respective second ends 240, 245 of the respective first and second linear portions 225, 230. The first and second handle adaptors 215, 220 can be connected or otherwise coupled to the respective second ends 240, 245 using various conventional techniques known in the art. The first and second handle adaptors 215, 220 are structured to engage at least a portion of a handle (not shown) on a piece of electrical equipment (not shown), such as, for example, a disconnect handle 310 (shown in
a shows handle operator 200′ in accordance with an embodiment of the disclosed concept. The handle operator 200′ has the first linear portion 225, the second linear portion 230, the first and second ends 260,240, respectively, of the first linear portion 225, the first and second ends 270,245, respectively, of the second linear portion 230, the chamber 250, the spring mechanism 235, the nub 280, the detents 290 and the first handle adaptor 215 as shown in
a and 7b show a handle operator 300 is structured to have a linear shape. The handle operator 300 includes a linear portion 325 which extends from a first end 340 to a second end (not shown). The first end 340 of the linear portion 325 is structured to engage a handle adapter 315. The example handle adaptor 315 extends away from (e.g., without limitation, perpendicular from) the first end 340 of the linear portion 325. The handle adaptor 315 can be connected to the first end 340 using various conventional techniques known in the art. The example handle adaptor 315 is connected or otherwise coupled to the first end 340 using a connector 360. The handle adaptor 315 is structured to engage the upper portion 355 of the disconnect handle 310, or a somewhat different upper end (not shown) of a different disconnect handle (not shown). The handle 310 is pivotally mounted (pivot not shown) on the motor control center unit 320. The linear portion 325 is horizontally aligned with the pivot point (not shown) of the corresponding handle 310 to be engaged. The size and shape of the handle adaptor 315 can depend on the size and shape of the upper portion 355 of the handle 310 to be engaged. An operator (not shown) can move the handle operator 300 to correspondingly switch the disconnect handle 310 clockwise from a first position shown in
It will be appreciated that an operator can be located outside of the FPB (not shown), which is established for the motor control center unit 320 such that the operator holds the handle operator 300 which has a length that is greater than the length of the FPB.
The example handle operators 1, 1a, 1′, 1″, 100, 100′, 200, 200′ and 300 can be constructed of various materials known in the art including durable, rigid materials. Suitable materials for the linear portions 25, 30, 130, 255, 230 and 340 can include polyester pull traded forms or extruded thermo-plastic polymers. The materials may be glass filled. Further, the material will include an electrically-insulative material. Then handle adaptors 15, 20, 115, 120, 215, 220 and 315 can be constructed of metal or plastic. If constructed of an electrically-conductive material, the handle adaptor material will also include an electrically-insulative material. The fixed extension 135 can be constructed of any of these materials which are suitable for the linear portions 25, 30, 130, 255, 230 and 340. The gripping handle can be constructed of a wide variety of materials and can include any of these materials which are suitable for the handle adaptors 15, 20, 115, 120, 215, 220 and 315.
While specific embodiments of the disclosed concept 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 the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
