BRIEF DESCRIPTION OF THE DRAWINGS
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:
FIG. 1 is a side elevational view of a portion of an electrical bus assembly and bus joint therefore;
FIG. 2 is an exploded isometric view of a portion of a maintenance-free electrical bus assembly including a corner bus joint, and a switchgear cabinet having a circuit breaker electrically coupled to the maintenance-free electrical bus assembly in accordance with an embodiment of the invention, with the switchgear cabinet and circuit breaker being shown in simplified form;
FIG. 3A is an exploded isometric view of a portion of a maintenance-free electrical bus assembly including a current transformer (CT) bushing bus joint in accordance with another embodiment of the invention;
FIG. 3B is a partially sectioned side elevational view of the portion of the maintenance-free electrical bus assembly including the CT bushing bus joint of FIG. 3A, showing the fastener and the threaded bore of the bus joint;
FIG. 3C is a close-up view of section 3C of FIG. 3B, showing the engagement between the threads of the bolt and the threads of the threaded bore of the CT bushing; and
FIG. 4 is an exploded isometric view of a portion of a maintenance-free electrical bus assembly including a spout bus joint in accordance with another embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Directional phrases used herein, such as, for example, front, back, top, bottom, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
As employed herein, the term “switchgear device” means a circuit interrupter, such as a circuit breaker (e.g., without limitation, low-voltage or medium-voltage or high-voltage); a motor controller/starter; a contactor; and/or any suitable device which selectively switches voltage, current or power.
As employed herein, the term “electrical bus” or “electrical bus member” means a rigid, solid conductor which carries or transfers voltage, current or power; a power bus bar; a power bus bar connection point; a finger cluster; a power bus bar connection point inside an electrical enclosure (e.g., without limitation, a switchgear cabinet); and/or a power bus structure for a switchgear device, but expressly excluding any grounded conductor (e.g., as used in a frame, enclosure or housing for a number of electrical devices).
As employed herein, the phrase “fastener” and “fastening element” refers to any suitable connecting or tightening mechanism expressly including, but not limited to, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts, and further includes any known or suitable component having a plurality of threads (e.g., without limitation, a threaded bore or aperture) structured to threadably engage the threads of another fastening element.
As employed herein, the phrase “thread form” refers to the particular shape, orientation and/or configuration of the plurality of threads of a particular fastening element.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “perpetually” refers to the substantially permanent or everlasting duration of the connection which is provided by a fastener assembly in accordance with embodiments of the invention. Specifically, the fastener assembly, once fastened, will never unintentionally come loose. In other words, the fastener assembly and the bus joint which it secures does not have to be inspected (i.e., it is maintenance-free) because it will remain secure for at least as long as the predetermined life expectancy (e.g., without limitation, about 15 years to about 50 years or more) of the switchgear device with which it is employed.
As employed herein, the term “number” shall mean one or an integer more than one (i.e., a plurality).
FIG. 2 shows an electrical enclosure 50 for housing switchgear devices 60 (one circuit breaker 60 is shown) including a maintenance-free electrical bus assembly 100 (partially shown). The electrical enclosure in the example of FIG. 2, is a switchgear cabinet 50 having a plurality of sides 52,54,56,58, with a single switchgear device 60 (e.g., without limitation, the circuit breaker 60 shown in simplified form in phantom line drawing in FIG. 2) disposed on or between the sides 52,54,56,58. More specifically, the switchgear cabinet 50 includes a top 52, a bottom 54, and first and second sidewalls 56,58. The maintenance-free electrical bus assembly 100 is electrically coupled to the switchgear device 60, as shown in simplified form in FIG. 2.
In FIG. 2, the switchgear cabinet 50 further includes a front cover, such as, the front door 62, which is pivotably coupled to second sidewall 58 by a pair of hinges 64 and structured to open and close the front door 62 for providing access to the circuit breaker 60 housed by the cabinet 50. It will, however, be appreciated that any known or suitable alternative suitable front cover, such as, for example, a removable front panel (not shown) could be employed. It will also be appreciated that a front cover is not required for the switchgear cabinet 50. It will further be appreciated that the circuit breaker or other suitable switchgear device 60 could be secured within the switchgear cabinet 50 in any known or suitable manner other than the rail structure 66 (shown in hidden line drawing in FIG. 2) coupling the circuit breaker 60 to first sidewall 56 of the switch gear cabinet 50.
As shown in FIG. 2, FIGS. 3A and 3B, and FIG. 4, the maintenance-free electrical bus assembly 100 (FIG. 2), 200 (FIGS. 3A and 3B), 300 (FIG. 4) comprises a plurality of electrical bus members 102,104 (FIG. 2), 202,204 (FIGS. 3A and 3B), 302,304 (FIG. 4), as defined herein, and at least one bus joint 106,206,306 which is comprised of the electrical connection of two or more of the electrical bus members 102,104,202,204,302,304. As shown in FIGS. 2, 3A and 3B, and respectively, a fastener assembly 108,208,308 fastens the bus joints 106,206,306 in order to maintain the electrical connection between the electrical bus members 102,104 (FIG. 2), 202,204 (FIGS. 3A and 3B), 302,304 (FIG. 4). As will be described hereinbelow, the fastener assembly 108,208,308 maintains the secure connection of the bus joints 106,206,306 perpetually.
Each fastener assembly 108,208,308 includes at least one first fastening element 110,210,310 having a plurality of first threads 112,212,312, and at least one second fastening element 114,214,314 including a plurality of second threads 116,216,316. The second threads 116,216,316 of each second fastening element 114,214,314 are structured to threadably engage the first threads 112,212,312 of a corresponding first fastening element 110,210,310, in order to perpetually secure the first threads 112,212,312 and the associated corresponding first fastening element 110,210,310, and thereby resist undesirable loosening of the bus joint 106,206,306 once the fastener assembly 108,208,308 has been fastened (see, for example, fastened fastener assembly 208 of FIG. 3B).
The maintenance-free electrical bus assembly 100,200,300 will be further understood and appreciated with reference to the following EXAMPLES, which will now be discussed individually with reference to FIGS. 2, FIGS. 3A, 3B, and 3C, and FIG. 4, respectively. For simplicity of illustration, only a portion of the maintenance-free electrical bus assembly 100,200,300, and a single bus joint 106,206,306 therefor is shown and described in each EXAMPLE. It will, however, be appreciated that the maintenance-free bus assemblies 100,200,300 could comprise any known or suitable combination of electrical bus members 102,104,202,204,302,304 and bus joints 106,206,306 therefor, other than or in addition to those shown and described herein.
EXAMPLE 1
In FIG. 2, the electrical bus members comprise first and second power bus bars 102,104 electrically connected by fastener assembly 108 at bus joint 106, which is a corner bus joint 106. The fastener assembly 108 includes a pair of threaded fasteners, such as bolts 110, each having a plurality of first threads 112, structured to threadably engage a plurality of second threads (generally indicated by reference 116 in FIG. 2) (see also second threads 216 of FIGS. 3B and 3C which are substantially the same as second threads 116) of corresponding nuts 114. An example of such engagement is provided in the partially sectioned view of FIG. 3B and close-up view of FIG. 3C, described hereinbelow.
Each bolt 110 in FIG. 2 further includes a washer 118 which is disposed between the hexagonal head of the bolt 110 and the first power bus bar 102. The bolts 110 are structured to be inserted through washers 118, through apertures 120 in the power bus bars 102,104, and threadably engaged (i.e., fastened or tightened) with corresponding nuts 114. In this manner, when the bolts 110 and nuts 114 are tightened, the power bus bars 102,104 are perpetually secured in electrical communication between the bolts 110 and nuts 114. Such perpetual securement is provided by way of the particular thread form 117 of the second threads 116 of nuts 114 which, in EXAMPLE 1, as well as in EXAMPLES 2 and 3 described hereinbelow, comprises a SPIRALOCK® thread form 117 (see also close-up view of SPIRALOCK® thread form 217 in FIG. 3C, which is essentially identical to thread forms 117 and 317 in FIGS. 2 and 4). The SPIRALOCK® thread form 117 is available from Spiralock Corporation which has a place of business at Madison Tech Center, 25235 Dequindre Road, Madison Heights, Mich. 48071-0629.
Accordingly, it will be appreciated that the maintenance-free electrical bus assembly 100 provides for a bus joint (e.g., corner bus joint 106) which does not need to be periodically inspected. More specifically, in an application such as EXAMPLE 1, shown in FIG. 2, wherein the bus joint 106 is substantially inaccessible, for example, because it is disposed behind the switchgear device 60, the fastener assembly 108 of the maintenance-free electrical bus assembly 100 provides for a perpetually secure mechanical and electrical connection between the electrical bus members (e.g., power bus bars 102,104) of the bus joint 106 so that the bus joint 106 and thus the maintenance-free electrical bus assembly 100 does not need to be inspected throughout the entire operating life expectancy (e.g., without limitation, about 15 years to about 50 years or more) of the circuit breaker 60.
It will be appreciated, as will now be discussed, that the electrical bus members could comprise any known or suitable electrical bus members, as defined herein, other than the power bus bars 102,104 shown in FIG. 2 and described with respect to EXAMPLE 1. It will also be appreciated that such electrical bus members could be configured in any known or suitable alternative configuration than the corner bus joint 106 of EXAMPLE 1, and could further that the bus joints could comprise more than two electrical bus members. Likewise, the fastener assembly (e.g., fastener assembly 108) could comprise any number and configuration of threaded fasteners other than the pair of threaded bolts 110 and nuts 114, shown in FIG. 2.
EXAMPLE 2
FIGS. 3A and 3B illustrate another example maintenance-free electrical bus assembly 200, wherein the bus joint 206 comprises as the first electrical bus member, a current transformer (CT) bushing 202 which is electrically connected to a power bus bar 204. Thus, the maintenance-free electrical bus assembly 200 of EXAMPLE 2 provides an example in which the first electrical bus member comprises a rigid, solid conductor, such as the CT bushing 202. In such embodiments, the rigid, solid conductor 202 includes an end, such as end 222 of CT bushing 202, and a threaded portion, such as threaded bore 214 in end 222 (best shown in FIG. 3B), comprises the second fastening element. The threaded bore 214 includes second threads 216, which comprise the aforementioned SPIRALOCK® thread form 217, best shown in FIG. 3C. Thus, as shown in FIGS. 3A and 3B, the bolt 210 is inserted through washer 218, through aperture 220 in power bus 204, and threadably engaged with SPIRALOCK® thread form 217 of threaded bore 214 in the end 222 of the CT bushing 202. In this manner, when the bolt 210 is tightened, the CT bushing 202 is mechanically and electrically coupled to the power bus bar 204, with the SPIRALOCK® thread form 217 perpetually maintaining the engagement, as previously discussed.
More specifically, FIG. 3C shows a close-up view of a portion of the threadable engagement between the first threads 212 of bolt 210 and the SPIRALOCK® thread form 217 of the second threads 216 of threaded portion 214 of CT bushing 202 (FIGS. 3A and 3B). As previously discussed, the SPIRALOCK® thread form 217 is available from the Spiralock Corporation. A detailed description of the SPIRALOCK® thread form 217 is available from the materials published on the Spiralock Corporation website, http://www.spiralock.com. Generally, the SPIRALOCK® thread form 217 is a unidirectional internal or female thread form which is structured to mate with conventional male thread fasteners, such as first threads 212 of bolt 210. As shown, the SPIRALOCK® thread form 217 includes a wedge ramp 219 which permits the bolt 210 to spin freely relative to the second or female threads 216 until a predetermined clamp load is applied to the bolt 210. At that point, the crests 221 of the first threads 212 of bolt 210 are drawn tightly against the wedge ramp 219, substantially eliminating radial clearances and creating a continuous spiral line contact along the entire length of the thread engagement. This continuous line contact spreads the clamp force evenly over all of the engaged first and second threads 212,216 thus improving the integrity of the fastener assembly 208, when it is fastened.
EXAMPLE 3
EXAMPLE 3, shown in FIG. 4, illustrates a spout joint 306 wherein the rigid, solid conductor comprises a spout conductor 302 having an end 322 with two threaded portions or threaded bores 314. Each threaded bore 314 has second threads 316, which comprise the aforementioned SPIRALOCK® thread form 317 (best shown in FIG. 3C, as SPIRALOCK® thread form 217). Thus, in EXAMPLE 3, a maintenance-free electrical bus assembly 300 is provided wherein two bolts 310 are structured to be inserted through corresponding washers 318, through corresponding apertures 320 in power bus bar 304, and to be inserted into two corresponding threaded bores 314 in the end 322 of spout conductor 302. As in EXAMPLE 2, previously discussed, when assembled (see, for example, FIG. 3B), the first threads 312 of bolts 310 threadably engage the second threads 316 of SPIRALOCK® thread form 317 (see also the close-up view of identical SPIRALOCK® thread form 317 of FIG. 3C) of the threaded bores 314, in order to perpetually secure the spout joint 306 together.
Accordingly, embodiments of the invention provide a maintenance-free electrical bus assembly wherein the fastener assemblies of one or more bus joints perpetually secure any known or suitable combination of electrical bus members in the desired configuration, thereby substantially eliminating the need to perform periodic preventive maintenance (PM) inspections of the bus joints.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the at 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 invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
Patent Application
20080038949
