Patent Application
20090174982
1. Technical Field
The present invention generally relates to electrical systems (ESD) currents and in particular to the control of electrostatic discharge (ESD) current flow in electrical systems.
2. Description of the Related Art
Many electrical systems experience electrostatic discharge (ESD) which generates ESD currents. The ESD currents flow in an uncontrolled manner across electronic equipment covers and into the chassis. The electronic system's immunity may be affected by the nearby ESD currents through the chassis frame or passing near sensitive circuits. Currents flowing throughout a chassis are reflected by system impedances and this current reflection causes standing waves within the chassis. These standing waves may cause subsequent radiation. The uncontrolled impedance connections at various locations between the equipment covers and the chassis contribute to the variability of the ESD response of the system.
Disclosed are a method and system for controlling the electrical connection between the metallic covers and the underlying metal chassis of an electrical system by the select placement of impedances in a current control connector. The current control connector places an impedance, capable of controlling electrostatic discharge (ESD) currents, between the covers and the underlying chassis. The current control connector comprises a number of metallic and dielectric components. Each of these components is ideally chosen such that the structure and composition of each component contributes to an overall functionality of the current control connector and an ability to control the ESD current flow. The relative placement of the components of the current control connector allows the current control connector to eliminate current flow along a number of paths but control the current flow along a preferred path. Thus, the current control connector prevents damage to and/or upset of the internal electrical system.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.
The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
The illustrative embodiments provide a method and system for controlling the electrical connection between the metallic covers and the underlying metal chassis of an electrical system by the select placement of impedances in a current control connector. The current control connector places an impedance, capable of controlling electrostatic discharge (ESD) currents, between the covers and the underlying chassis. The current control connector comprises a number of metallic and dielectric components. Each of these components is ideally chosen such that the structure and composition of each component contributes to an overall functionality of the current control connector and an ability to control the ESD current flow. The relative placement of the components of the current control connector allows the current control connector to eliminate current flow along a number of paths but control the current flow along a preferred path. Thus, the current control connector prevents damage to the internal electrical system.
In the following detailed description of exemplary embodiments of the invention, specific exemplary embodiments in which the invention may be practiced are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, architectural, programmatic, mechanical, electrical and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Within the descriptions of the figures, similar elements are provided similar names and reference numerals as those of the previous figure(s). Where a later figure utilizes the element in a different context or with different functionality, the element is provided a different leading numeral representative of the figure number (e.g, 1xx for
It is understood that the use of specific component, device and/or parameter names are for example only and not meant to imply any limitations on the invention. The invention may thus be implemented with different nomenclature/terminology utilized to describe the components/devices/parameters herein, without limitation. Each term utilized herein is to be given its broadest interpretation given the context in which that terms is utilized.
With reference now to
In current control connector 100, a screw is utilized to assembly cover 103 to a chassis (not explicitly shown in
Among the steps that are executed in order to realize the current control connector, and which are specific to the invention, are: (a) selecting a group of dielectric and metallic components, each with a particular structure, which when assembled together, controls an ESD current flow; (b) assembling the current control connector with the group of dielectric and metallic components; and (c) controlling the ESD current flow, based on a relative placement of the components within the current control connector. Current control connector 100 is designed to enable a number of current control features, which are described below within the description of
Those of ordinary skill in the art will appreciate that the hardware and basic configuration depicted in
In current control connector 100, screw head 101 rests partially upon metallic disk 105. Metallic disk 105 rests directly upon top isolation component 102. In addition, metallic disk 105 remains affixed in place by metallic insert(s) 106, a section of disk 105 which is inserted inside a hole(s) within top isolation component 102. Top isolation component 102 rests partially upon cover 103. Metallic insert(s) 106 rests directly upon cover 103, which cover 103 further rests partially upon bottom isolation component 107. As a result of the relative placement and structure of the components in current control connector 100, a space (109) exists above a section of metallic disk 105, adjacent to screw head 101, and also adjacent to a section of top isolation component 102.
A complete explanation of current control connector 100 is facilitated with a further view of current control connector 100, depicting a preferred current path, presented in the illustration of
With reference now to
A number of ESD current paths are also illustrated in current control connector 100. Some of the illustrated ESD current paths are undesired paths which are unlikely as a result of the structure of current control connector 100. These paths are undesired because ESD current flow along these paths may cause damage to the internal electrical system. The composition of various components within current control connector 100 contributes to the elimination of these unlikely paths. In order to provide a reference, these paths are illustrated in current control connector 100. Specifically, these unlikely paths are illustrated as follows: (1) first unlikely path 621; (2) second unlikely path 623; (3) third unlikely path 625; (4) fourth unlikely path 626; and (5) fifth unlikely path 624.
On the other hand, a desired path of a controlled flow of an ESD current is preferred path 622. Thus, as current flow is eliminated in the unlikely current paths, a controlled ESD current flow is directed along preferred path 622.
With the design of current control connector 100, ESD currents are prevented from traveling through the undesired high impedance paths. The ESD currents travel instead through an ideal lower resistance (i.e., more conductive) path to reach the chassis. In current control connector 100, arcing is prevented by increasing the distances of any potential arc path, and by employing dielectric components with higher impedance levels within the potential arc path. Thus, the unlikely arc paths are effectively eliminated within current control connector 100. More specifically, the distances of the arc paths are set to be large enough to prevent the flow of ESD currents, given a designated voltage level.
ESD current flow is eliminated along first unlikely path 621, which path 621 includes a section from screw head 101 to top isolation component 102 via space 109. The form of top isolation component 102 is ideally chosen to create a relatively large (high impedance) space (109). In addition, unlikely path 621 is eliminated with the aid of the high impedance characteristic (resulting from the dielectric composition) of top isolation component 102. The ESD current is provided a relatively lower impedance path (illustrated as preferred path 622) from screw head 101, through metallic disk 105, then through insert(s) 106 and along cover 103. The metallic composition of insert(s) 106 ideally connects ESD currents from resistive disk 105 to cover 103. As current takes the path of least resistance, current flow is severely restricted through third unlikely path 625 and fourth unlikely path 626, but flows through metallic insert(s) 106 which is adjacent to both third unlikely path 625 and fourth unlikely path 626. Third unlikely path 625 and fourth unlikely path 626 indicate paths which may include short arc paths adjacent to both insert(s) 106 and top isolation component 102. ESD current flow along second unlikely path 623 is also eliminated by the intrinsically higher impedance of second unlikely path 623 as compared with the relatively low impedance of preferred path 622. Similarly, the relatively high impedance of fifth unlikely path 624 eliminates ESD current flow. Fifth unlikely path 624 includes a section of dielectric insulator 104 and a section of bottom isolation component 107 which contribute to the relatively high impedance of fifth unlikely path 624. Ultimately, preferred path 622 is the designated path for the flow of ESD currents.
In current control connector 100, component structures are essentially lengthened to prevent arcing to the low impedance structures forcing the current through the resistance. The non-metallic (dielectric) plates are connected to collectively increase the ESD discharge distance that forces the current through the resistive metallic disk. The metallic disk itself is relatively conductive and directs the current to redundant metallic inserts that provide the ESD current pathway. For installation in a system where the chassis is closely spaced to the covers, a dielectric (insulator) is placed upon the chassis surface to prevent any uncontrolled secondary discharge paths.
In current control connector 100, since arcing is prevented along these higher impedance paths, ESD currents follow a lower impedance path that is provided through the resistive material on the disks and then through the screw body. The screw is not altered in any way but the current flow and current path provided by current control connector (100) between the cover and the chassis are controlled. Although one embodiment is presented as a configured connection(s) between the covers and the chassis, in yet another embodiment, the connection may also be implemented between chassis sections to limit current flow through the center of the machine to provide added protecting against any damaging effects (to key internal components) that may be caused by ESD currents.
Although current control connector 100 described in
The process of
In the flow chart above, the method is executed as a series of steps. In some implementations, certain steps of the method are combined, performed simultaneously or in a different order, or perhaps omitted, without deviating from the spirit and scope of the invention. Thus, while the method steps are described and illustrated in a particular sequence, use of a specific sequence of steps is not meant to imply any limitations on the invention. Changes may be made with regards to the sequence of steps without departing from the spirit or scope of the present invention. Use of a particular sequence is therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular system, device or component thereof to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
