Friday, January 28, 2011

Overhead lifter for electrical switching apparatus

Electrical switching apparatus for opening and closing electrical distribution circuits are well known in the art. Such electrical switching apparatus includes power circuit breakers and network protectors which provide protection, and electrical switches which are used to energize and deenergize parts of the circuit or to transfer between alternative power sources.

It is also known to house electrical switching apparatus within an electrical cabinet, such as, for example, a switchgear cabinet for the distribution of electrical power from incoming utility lines to electrical loads distributed throughout a building or other facility. Typically, a plurality of electrical switching apparatus, such as power circuit breakers, are removably mounted within a plurality cells in the electrical cabinet. Such electrical switching apparatus may vary in size and may weigh up to several hundred pounds. Therefore, means must be provided to lift the electrical switching apparatus to properly position the electrical switching apparatus for insertion into their respective cells.

It is known to provide a rail mounted lifter positioned on or adjacent a top side of an electrical cabinet for lifting the electrical switching apparatus for insertion into the cells of the electrical cabinet. One such lifter includes a cantilevered portion that extends outwardly from the electrical cabinet where the lifter includes a winch assembly for connecting to and lifting the electrical switching apparatus. The winch assembly includes a spool for winding a cable thereon. It has been found that often the cable does not wind evenly onto the spool of the winch assembly. The cable has a tendency to accumulate on one area of the spool causing sporadic jumping as the spool turns and releases or retracts the cable. This can result in sudden drops to the electrical switch apparatus during lifting. Of course, the uneven winding of the cable on the spool and the resulting sudden drops to the electrical switching apparatus during lifting are undesirable and may possibly result in damage to the electrical switching apparatus and excessive stress and fatigue being applied to the lifter.
It has also been observed that the lifter has a tendency to bind or twist as a result of the load of the electrical switching apparatus being applied on the cantilevered portion of the lifter. This is particularly the situation when the lifter is supporting the weight of the electrical switching apparatus and it is desired to translate or laterally move the lifter along the top of the electrical cabinet.

These and other needs are satisfied by the invention which is directed to a lifting assembly for lifting an electrical switching apparatus for placement in an electrical cabinet. The lifting assembly includes a first rail member horizontally disposed adjacent a top surface of the electrical cabinet where the first rail member is generally parallel to and positioned adjacent a front surface of the electrical cabinet. The lifting assembly also includes a second rail member horizontally disposed adjacent the top surface of the electrical cabinet where the first rail member is generally parallel to and spaced apart from the second rail member. The lifting assembly further includes a support frame and wheel means mounted on the support frame for providing movement of the support frame along the first rail member and the second rail member. A winch having a spool is provided for cooperating with a cable having a first end attached to the winch and a second end for securing to the electrical switching apparatus and lifting of the same. The lifting assembly includes a pivotable, rotatable cable support member mounted upon the support frame to provide even distribution of the cable on the spool. The cable support member guides the winding of the cable onto the spool of the winch where the cable would otherwise be wound on the spool due to its own natural tendency. The pivotable, rotatable cable support member of the invention prevents the cable from accumulating on one area of the spool which may result in sporadic jumping or sudden drops as the spool turns and releases or retracts the cable.
The wheel means for mounting on the support frame and providing movement of the support frame on the first rail member and the second rail member preferably includes at least one wheel rotatable about a horizontal axis for movement on the second rail member. The wheel means also preferably includes at least one wheel rotatable about a horizontal axis for movement on the first rail member and at least two wheels rotatable about vertical axes also for movement on the first rail member. This wheel configuration provides support for the lifting assembly and also provides lateral stability to the lifting assembly and minimizes binding or twisting of the lifting assembly during lifting of the electrical switching apparatus.

While specific embodiments of the invention 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 invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.

No comments:

Post a Comment