Abstract:
A device having an upper plate comprising a top face and a bottom face with an opening. A lower plate comprising a top face and a bottom face substantially parallel to the upper plate, with an opening. A middle plate between and substantially parallel to the upper plate and lower plate, capable of moving with respect to the upper plate and lower plate, and having a top face a bottom face and at least one opening. A plurality of gaskets configured to electrically connect the upper plate, the middle, plate, and the lower plate and provide an interface that is designed to allow the middle plate to slide substantially parallel to the upper plate and the lower plate. At least one waveguide through the at least one opening of the middle plate.

Description:
BACKGROUND 
       [0001]    This disclosure relates generally to electromagnetic interference, and more specifically, regards controlling the level of emissions of electromagnetic interference emitted and absorbed from electrical equipment in an enclosure. Electromagnetic interference (EMI) is a disturbance that interrupts, obstructs, degrades, or limits the effective performance of electronics and electrical equipment. It can occur unintentionally as a result of spurious emissions and responses. Electromagnetic compatibility (EMC) refers to ensuring tries to ensure that equipment items or systems will not interfere with or prevent the correct operation of other equipment items or systems through emission or absorption of EMI. 
       SUMMARY 
       [0002]    Disclosed herein are embodiments of a device for attenuating electromagnetic emissions. In various embodiments, the device may include an upper plate having a first top face, a first bottom face and a first opening spanning from the first top face to the first bottom face. The device may also include a lower plate substantially parallel to the upper plate and having a second top face a second bottom face, and a second opening spanning from the second top face to the second bottom face. In addition, the device may include a middle plate between and substantially parallel to the upper plate and lower plate, capable of moving with respect to the upper plate and lower plate, and having a third top face a third bottom face and at least one third opening spanning from the third top face to the third bottom face. Also, the device may include a first gasket physically connected to the first bottom face of the upper plate, bordering the first opening, and electrically connecting the upper plate and the middle plate. Consistent with various embodiments, the device may also include a second gasket physically connected to the second top face of the lower plate, bordering the second opening, and electrically connecting the lower plate and the middle plate. In addition, the device may include a third gasket physically connected to the third top face of the middle plate, bordering at least one edge of the third top face of the middle plate, and electrically connecting the upper plate and the middle plate. Also, the device may include a fourth gasket physically connected to the third bottom face of the middle plate, bordering at least one edge of the third bottom face of the middle plate, and electrically connecting the lower plate and the middle plate. Furthermore, the device may include at least one waveguide that extends through the at least one third opening spanning at least from the first top face of the upper plate to the second bottom face of the lower plate. 
         [0003]    Also disclosed herein are embodiments of a device allowing movability of an egress for cables. In various embodiments, the device may include an upper plate comprising a first top face and a first bottom face, with a first opening spanning from the first top face to the first bottom face. The device may also include a lower plate comprising a second top face and a second bottom face, substantially parallel to the upper plate and with a second opening spanning from the second top face to the second bottom face. In addition, the device may include a middle plate between and substantially parallel to the upper plate and lower plate, capable of moving with respect to the upper plate and lower plate, and having a third top face a third bottom face and at least one third opening spanning from the third top face to the third bottom face. Also, the device may include a plurality of gaskets configured to electrically connect the upper plate, the middle, plate, and the lower plate and provide an interface that is designed to allow the middle plate to slide substantially parallel to the upper plate and the lower plate. Furthermore, the device may include at least one waveguide through the at least one third opening spanning at least from the first top face of the upper plate to the second bottom face of the lower plate. 
         [0004]    Also disclosed herein are embodiments of an enclosure allowing movability of an egress for cables. In various embodiments, the enclosure may include a container having a first opening. In addition, the enclosure may include a device comprising an upper plate comprising a first top face and a first bottom face, configured to substantially seal the first opening of the container, and having a second opening spanning from the first top face to the first bottom face. The device may also include a lower plate comprising a second top face and a second bottom face, substantially parallel to the upper plate and with a third opening spanning from the second top face to the second bottom face. In addition, the device may include a middle plate between and substantially parallel to the upper plate and lower plate, capable of moving with respect to the upper plate and lower plate, and having a third top face a third bottom face and at least one fourth opening spanning from the third top face to the third bottom face. Also, the device may include a plurality of gaskets configured to electrically connect the upper plate, the middle, plate, and the lower plate and provide an interface that is designed to allow the middle plate to slide substantially parallel to the upper plate and the lower plate. Furthermore, the device may include at least one waveguide through the at least one fourth opening spanning at least from the first top face of the upper plate to the second bottom face of the lower plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  depicts an enclosure for a moveable shielded cable egress, consistent with embodiments of the present disclosure. 
           [0006]      FIG. 2A  depicts an example of a cross section of a device for moveable shielded cable egress in a first position, consistent with embodiments of the present disclosure. 
           [0007]      FIG. 2B  depicts an example of the cross section of the device for moveable shielded cable egress in a second position, consistent with embodiments of the present disclosure. 
           [0008]      FIG. 3  depicts a device for moveable shielded cable egress with alignment considerations, consistent with embodiments of the present disclosure 
           [0009]      FIG. 4  depicts a diagonal view and a top view of an example of a cross section of a waveguide fitted with a central plug, consistent with embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Electromagnetic energy from sources external or internal to electrical equipment affects that equipment adversely by causing it to have undesirable responses, such as degraded performance or malfunctions. When this occurs, the electromagnetic energy is called electromagnetic interference (EMI), and the adversely affected equipment is said to be susceptible to EMI. The damaging effects of EMI may pose unacceptable risks in many areas of technology and it may be necessary to control EMI and reduce the risks to acceptable levels. 
         [0011]    EMI is radiated through openings in equipment enclosures, including but not necessarily limited to openings relating to one or more of: ventilation access; cable or meter holes; around the edges of doors, hatches, drawers, and panels; and through imperfect joints in the enclosures. EMI may also be radiated from leads and cables connected to an electrical equipment, or picked up by leads and cables connected to susceptible electrical equipment. 
         [0012]    The present disclosure relates to a system and a device for restricting the emission and absorption of EMI radiation by electrical equipment. The electrical equipment may be within an enclosure that is part of the system. The device may have three layered plates and each plate may have at least one opening. The openings may be aligned, one on top of the other, and provide an egression for cables coming from the electrical equipment. Also, the middle plate may have an opening smaller than the opening of the upper and lower plates. The middle plate and, consequently, the cables, may then be capable of shifting from one position to another. This may allow the cables to be moved when maintenance is performed on the electrical equipment, without forcing the electrical equipment offline. Furthermore, because the opening on the middle plate may be smaller than the openings on the upper and lower plates, adequate shielding may be provided, limiting the emission and absorption of EMI radiation. 
         [0013]    Turning now to the figures,  FIG. 1  depicts an enclosure  100  for a moveable shielded cable egress, consistent with embodiments of the present disclosure. The enclosure  100  may include a device  102  and sidewalls  100   a  and  100   b , bottom  100   c , rear wall  100   d , and front wall  110   e.    
         [0014]    The electromagnetic enclosure  100  may be configured to attenuate EMI between sources and susceptible equipment. Enclosure  100  reduces EMI when EMI fields induce circulation currents in the enclosure and the fields set up by those circulating currents oppose the EMI fields, so that the net fields on the lower side of the enclosure may be reduced. Enclosure  100  may also attenuate EMI fields by a combination of reflection and absorption. Furthermore, the law of reciprocity applies. Enclosure  100  may be thought of as containing EMI emanating from an internal source, or excluding EMI from reaching susceptible equipment. For an enclosed source, the EMI level outside enclosure  100  may be reduced below the level inside the enclosure  100  and susceptible equipment may benefit. When an electromagnetic wave impinges on enclosure  100 , some of the wave&#39;s energy is reflected at the surface of the enclosure, some is absorbed by the enclosure, and some is transmitted through the enclosure. 
         [0015]    For good isolation enclosure  100 , may be fabricated from a single, homogeneous piece of material, without seams, joints, or openings. When an opening is provided for periodic inspection, maintenance, repair, or other purpose, it may be equipped with a cover, door, window, or panel of the same material as the enclosure. However, joints or openings represent an anomaly in the continuity of the enclosure surface and is subject to leakage. A gasket may seal joints in such a way as to restore the enclosure integrity as essentially, a one piece element. 
         [0016]    Furthermore, electrical equipment inside a single piece enclosure may be protected because current from electromagnetic waves may not circulate on the inside wall of an enclosure. The enclosure may not entirely absorb an electromagnetic field, but has current running along its surface that creates a separate electromagnetic field to cancel the effects of the original field. As electromagnetic currents typically take the path of least impedance, they run along the exterior of the enclosure. An opening in the enclosure may cause the current flow to be diverted around the opening. This increase in impedance may cause an electromagnetic wave or EMI to propagate from the opening. 
         [0017]    As illustrated, device  102  may include an upper plate  104 . Upper plate  104  may be composed of a conductive material. Upper plate  104  may operate as a sidewall, top, front, bottom, rear wall or front wall of enclosure  100 . The use of a conductive material for upper plate  104  may maintain a low impedance connection between upper plate  104  and enclosure  100 , therefore, providing a good connection for current to travel along enclosure  100 . Furthermore, upper plate  104  may have an opening. The opening may allow for cables  118 , which may be connected to electrical equipment (not shown) inside enclosure  100 , to be positioned and repositioned in one or more of the x, y and z planes or directions. 
         [0018]    In certain embodiments, upper plate  104  may be coupled to lower plate  106 . Lower plate  106  may also be formed in a shape that allows for it to be placed adjacent to one or more of sidewall  100   a ,  100   b , bottom  100   c , rear wall  100   d , or front wall  110   e . In another embodiment, upper plate  104  may act as sidewall  100   a  of enclosure  100  and lower plate  106  may then be placed adjacent to one or more of the sidewalls, rear wall  100   d , bottom  100   c , and a top wall (not shown). By having an adjacency, lower plate  106  may establish a surface contact with enclosure  100 , which may exhibit lower impedance than a point contact and decrease the EMI emissions. A surface contact may exhibit a lower-impedance than a point contact because a surface contact may establish a better electrical connection than a point contact for current to travel, therefore, lowing the impedance and decreasing EMI emissions. Furthermore, lower plate  106  may be composed of a conductive material. The use of a conductive material for lower plate  106  may maintain a low impedance connection between upper plate  104  and enclosure  100 , therefore, providing a good connection for current to travel along enclosure  100 . Lower plate  106  may also have an opening. The opening may allow for cables  118 , which may be connected to electrical equipment (not shown) inside system  100 , to be positioned and repositioned in one or more of the x, y and z planes or directions. 
         [0019]    As shown in  FIG. 1 , middle plate  108  may be between upper plate  104  and lower plate  106 . Middle plate  108  may have an opening smaller than the openings on upper plate  104  and lower plate  106 . In some embodiments, middle plate  108  is designed to move in the xy plane relative to either, or both, upper plate  104  or lower plate  106 . Furthermore, cables  118  may go through the opening of middle plate  108  and the position of the opening on middle plate  108  in the xy plane may change to allow the position of cables  118  to change relative to the rest of the enclosure. 
         [0020]    Cable egress and ingress from an enclosure and cable position within an enclosure may be a source of many problems. For instance, when servicing an enclosure housing electrical equipment the cables may interfere with the moving of assemblies, subassemblies, drawers, etc. Also, an electrical apparatus of the electrical equipment and the cable density may be such that servicing either may result in accessibility issues and force the electrical apparatus offline. Furthermore, increasing the size of cable egress and ingress openings may interrupt basic system operation. For example, a large opening may not have the shielding properties necessary to prevent EMI emissions from propagating out of the enclosure, e.g., enclosure  100 , or entering the enclosure and may cause the electrical equipment to malfunction. 
         [0021]    A moveable middle plate  108  with an opening configured to allow for the egress and ingress of cables  118  may allow for the position and reposition of cables  118  when maintenance is being done on electrical equipment housed within enclosure  100 . An electrical apparatus may also be installed and removed from electrical equipment in enclosure  100  without removing cables  118 . Furthermore, by fitting middle plate  108  between upper plate  104  and lower plate  106 , the opening may be small enough to continue to provide electrical equipment in enclosure  100  the necessary shielding from EMI emissions. 
         [0022]    In various embodiments, a waveguide  116  may be placed through the opening in middle plate  108 . Waveguide  116  may limit the level of EMI emitted by cables  118  and provide additional shielding to cables  118  from EMI emissions from outside sources. When EMI is emitted, it propagates by the process of electrical coupling. Electrical coupling is the transfer of energy from one medium to another. There are four basic coupling mechanisms: conductive, capacitive, inductive, and radiative. Radiative coupling occurs when source and receptor operate as radio antennas, that is, the source emits an electromagnetic wave which propagates across open space and is received by the receptor. Cables  118 , may operate as antennas, which makes them and the electrical apparatus they are connected to, susceptible to absorbing and emitting radiated EMI. Waveguide  116  may be a structure that guides waves and may be made of conductive or dielectric materials. Waves propagating in open space may come into contact with waveguide  116 . The waves may be confined inside the waveguide  116  due to total reflection from the waveguide, thus, limiting the emission or absorption of EMI by cables  118 . Furthermore, waveguide  116  may be of a shape that gives middle plate  108  increased shielding properties. 
         [0023]    As illustrated, device  102  may be fitted with gaskets  110   a ,  110   b ,  112 . Consistent with various embodiments, gaskets  110   a  and  110   b  may be physically connected to the edges of middle plate  108 . Gaskets  110   a  and  110   b  may be physically connected to the edges of middle plate  108  in various ways such as a conductive adhesion, an indent in middle plate  108 , a conductive fastening pin, etc. Gaskets  110   a  and  110   b  may also be in contact with upper plate  104  and lower plate  106 , but not physically connected so that middle plate may move relative to upper plate  104  and lower plate  106 . Gasket  112  may be physically connected to upper plate  104  in relatively the same way as gaskets  110   a  and  110   b  are connected to middle plate  108 . Furthermore, gasket  112  may be in contact with middle plate  108 , but not physically connected so that middle plate  108  may move relative to upper plate  104  and lower plate  106 . A gasket (not shown) may also be physically connected to lower plate  106 . The gasket may be physically connected to lower plate  106  in relatively the same way as gaskets  110   a  and  110   b  are connected to middle plate  108 . Furthermore, the gasket may be in contact with middle plate  108 , but not physically connected so that middle plate  108  may move relative to upper plate  104  and lower plate  106 . 
         [0024]    As stated herein, electromagnetic currents typically take the path of least impedance and a gap or opening may allow emissions to radiate. The gap may display a high-level of impedance and may not allow the current to flow along device  102  and enclosure  100 . This may cause EMI to be radiated and interfere with the electrical equipment inside system  100 . Gaskets  110   a ,  110   b ,  112  may provide an electrical connection between upper plate  104 , middle plate  108 , and lower plate  106  and allow for the current to flow along device  102  and enclosure  100 . 
         [0025]    Furthermore, as stated herein, middle plate  108  may be configured to move relative to upper plate  104  and lower plate  106  and depending on the positioning and repositioning of cables  118 . This may cause middle plate  108  to experience shear stress from both upper plate  104  and lower plate  106 . Shear stress arises from the force parallel to the cross section of a surface, such as the force exerted by the surfaces of upper plate  104  and lower plate  106  on the surface of middle plate  108 . Therefore, gaskets  110   a ,  110   b , and  112  may be capable of reducing the shear stress experienced by middle plate  108  (e.g., by providing a low friction interface) and allow middle plate  108  to slide between upper plate  104  and lower plate  106 . 
         [0026]      FIG. 2A  depicts an example of a cross section of a device  200  for moveable shielded cable egress in a first position, consistent with embodiments of the present disclosure. The device  200  may include an upper plate  104 , a lower plate  106 , a middle plate  108 , gaskets  110   a ,  110   b ,  112 ,  114 , and waveguide  216 . Upper plate  104 , lower plate  106 , middle plate  108 , gaskets  110   a ,  110   b , and  112  may be configured and may operate in relatively the same manner as discussed above for device  102 . As shown in  FIG. 2A , device  200  includes gasket  114 . Gasket  114  may be physically connected to lower plate  106  in various ways such as a conductive adhesion, an indent in middle plate  108 , a conductive fastening pin, etc. Furthermore, gasket  114  may be in contact with middle plate  108 , but not physically connected so that middle plate  108  may move relative to upper plate  104  and lower plate  106 . Gaskets  114  may also provide an electrical connection between middle plate  108  and lower plate  106 . This may allow for the current to flow along device  200  and enclosure  100 , shown in  FIG. 1 . Also, gasket  114  may be capable of absorbing the frictional force experienced when middle plate  108  moves relative to lower plate  106 . 
         [0027]    In various embodiments, waveguide  216  may be placed through the opening in middle plate  108 . As illustrated in  FIG. 2A , waveguide  216  may be in the shape of a cylinder and may be located at position  1  in the xy plane. Position  1  of the opening in middle plate  108  and consequently, waveguide  216 , may be determined by the positions of the cables attached to electrical equipment within an enclosure, i.e., enclosure  100 . 
         [0028]    In another embodiment, waveguide  216  may have grooves on its inner wall that are capable of receiving cables and partially surround the circumference of the cables. Waveguide  216  may then be fitted with a central plug  400  as shown in  FIG. 4 .  FIG. 4  depicts a diagonal view and a top view of an example of a cross section of a waveguide  216  fitted with a central plug  400 , consistent with embodiments of the present disclosure. As illustrated, central plug  400  may have grooves on its outer wall that are capable of surrounding the remaining circumference of the cables, left open by waveguide  216 . The size of central plug  400  may be determined by the size of waveguide  216 . Also, the grooves on central plug  400  may need to match up with the grooves on waveguide  216 . Therefore, the number of grooves on waveguide  216  and central plug  400  may be determined by the number of cables that are attached to electrical equipment within an enclosure. Furthermore, central plug  400  may provide waveguide  216  and, thus, device  200 , with increased shielding properties. 
         [0029]      FIG. 2B  depicts an example of the section of the device  200  for moveable shielded cable egress in a second position, consistent with embodiments of the present disclosure. As shown, the opening in middle plate  108  and consequently, waveguide  216 , may be located at position  2  in the xy plane. Position  2  may be determined by the repositioning of the cables attached to electrical equipment within an enclosure, e.g., enclosure  100 . For example, it may be necessary to perform maintenance on electrical equipment within an enclosure. It may be determined that an electrical apparatus of the electrical equipment may need to be relocated inside the enclosure to make room for an additional electrical apparatus to the electrical equipment. The relocation of the electrical apparatus and addition of another electrical apparatus may cause problems with the cable position and the current cable egress. By moving the opening in middle plate  108  from position  1  to position  2 , the cables may be placed in a location that may not interfere with the moving of the electrical apparatus, may allow the addition of an electrical apparatus while the current electrical equipment remains online, and may maintain the shielding necessary for the electrical equipment. 
         [0030]      FIG. 3  depicts a device  300  for moveable shielded cable egress with alignment considerations, consistent with embodiments of the present disclosure. Device  300  may include an upper plate  104 , an lower plate  106 , a middle plate  108 , gaskets  110   a ,  110   b ,  112 , waveguides  316   a ,  316   b ,  316   c ,  316   d ,  316   e ,  316   f , fasteners and springs  318   a ,  318   b ,  318   c , and alignment pins  320   a  and  320   b . Upper plate  104 , lower plate  106 , middle plate  108 , gaskets  110   a ,  110   b , and  112  may be configured and may operate in relatively the same manner as discussed above for device  102 . 
         [0031]    As shown in  FIG. 3 , alignment pins  320   a  and  320   b  may be physically connected to upper plate  104 . Alignment pins  320   a  and  320   b  may be used to place middle plate  108  into a locked or detent position for permanent fixed locations or for holding cables, e.g., cables  118 , from  FIG. 1 . The cables may need to be placed in a fixed location while maintenance may be performed on electrical equipment inside an enclosure, to keep the cables from interfering with equipment inside an enclosure, etc. Alignment pins  320   a  and  320   b  may be physically connected to upper plate  104 , however, they may also be physically connected to lower plate  106  or other locations on device  300  that may provide the necessary placement of middle plate  108  into a locked or detent position. Furthermore, there may be more or less alignment pins depending on various embodiments. 
         [0032]    As illustrated, fasteners and springs  318   a ,  318   b , and  318   c  may be physically connected to lower plate  106 . Fasteners and springs  318   a ,  318   b , and  318   c  may be used to reposition middle plate  108  and consequently cables  118 . It may be necessary to reposition cables  118  for several reasons such as unintentional shock, outside vibrations, etc., that cause middle plate  108  to move relative to upper plate  104  and lower plate  106 . One end of a fastener may be physically connected to a plate and the other end of the fastener may be capable of receiving a spring. Fasteners and springs  318   a ,  318   b , and  318   c  may be physically connected to lower plate  106 , however, they may also be physically connected to upper plate  104  or other locations on device  300  that may provide the necessary repositioning of the cables. Furthermore, there may be more or less fasteners and springs as depicted in  FIG. 3  depending on various embodiments. 
         [0033]    In various embodiments, waveguides  316   a ,  316   b ,  316   c ,  316   d ,  316   e , and  316   f  may be placed through the opening in middle plate  108 . As illustrated in  FIG. 3 , waveguides  316   a - 316   f  may be in the shape of cylinders and waveguides  316   a - 316   f  may allow for an individual cable to egress from an individual waveguide. Therefore, the number of waveguides  316   a - 316   f  may be determined by the number of cables that are attached to electrical equipment within an enclosure. Furthermore, having numerous waveguides that allow for individual cables to egress from individual waveguides may increase the shielding properties of device  300 . 
         [0034]    While the invention has been described with reference to specific embodiments thereof, those skilled in the art will be able to make various modifications to the described embodiments without departing from the true spirit and scope of the embodiments. The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that these and other variations are possible within the spirit and scope of the embodiments as defined in the following claims and their equivalents.