Latch and locate cradle

Details Latch and locate cradle Latch and locate cradle

1998-12-21

2001-01-02

Picard, Leo P. (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

C361S608000, C361S636000, C200S050020

Utility Patent

active

06169653

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to electrical switchgear and specifically to locating and supporting mechanisms for draw-out circuit breakers.
BACKGROUND OF THE INVENTION
Draw-out circuit breakers are well known in the switchgear and panel board industry. The draw-out breaker is slidably received within a drawer-like breaker compartment dimensioned to snugly receive the breaker. Since draw-out breakers can be very large and heavy (100-400 lbs.), it is common to place the breaker on rails that are extendable from the breaker compartment. The breaker can then be racked into one of several positions within the breaker compartment by a worm screw and cam mechanism. At least one of these several positions involves the engagement of primary and secondary movable contacts mounted on the back of the breaker, with associated primary and secondary stationary contacts mounted at the back of the breaker compartment. The primary contacts carry line current into the breaker and load current out of the breaker and, therefore, are generally large. The secondary contacts, which provide monitoring and control connections for the breaker, are generally small compared to the primary contacts. As circuit breaker technology has advanced, the number of secondary contacts required has increased and the physical size of the breaker has generally decreased. Therefore, the available space for secondary contacts has also decreased, thus causing the secondary contacts to be positioned even closer together (miniaturized connectors). It is very important that the movable contacts, both primary and secondary, be properly aligned in the X, Y and Z-axes with their associated stationary contacts mounted in the breaker compartment. In the case of draw-out breakers, which are slidably positioned within the breaker compartment, contact alignment is a function of the breaker and contact support assemblies of the breaker compartment. These support assemblies have been constructed of formed sheet metal parts, which are inherently subject to a buildup of tolerances. Further, the assembly of the formed parts is critical to the proper alignment of the primary and secondary movable contacts on the breaker with the associated primary and secondary stationary contacts in the breaker compartment. It is therefore desirable to incorporate an assembly process that effectively eliminates the tolerance buildup associated with formed sheet metal parts and the critical alignment issues of the assembly process. It is also desirable that the assembly process be self-correcting such that any part that can be misaligned due to a forming process will be brought into properly alignment by the assembly process.
SUMMARY OF THE INVENTION
The present invention provides a one-piece circuit breaker support cradle in which all features critical for contact alignment are precisely punched by a CNC (Computer Numerical Control) machine and remain in the flat after any forming of the support cradle is done. The back panel of the breaker compartment, on which the primary and secondary stationary contacts are mounted or in some fixed relationship with, has all features critical to alignment precisely punched by a CNC machine. The alignment features of the back panel also remain in the flat after any forming of the back panel is done. By eliminating the buildup of tolerances associated with sheared part blanks, formed flanges, and screw type fastening hardware commonly used to support and align a circuit breaker within the breaker compartment, a more precise alignment of contacts is accomplished. The alignment means includes a uniquely shaped slot and locking tab arrangement configured such that a slight friction fit between alignment features of the locking tab and slot ensure precise alignment. The locking tab and slot are also configured such that misalignments between the breaker cradle and the back panel of the breaker compartment caused by metal forming will automatically be corrected during assembly. The design of the locking tab also provides an integrally formed levering feature which makes the friction fit installation of the locking tab into the slot much easier. Once assembled, the friction fit of the alignment slot and locking tab provides precise X, Y and Z-axis alignment between the breaker cradle and the back panel of the breaker compartment. The locking feature of the locking tab ensures that X, Y and Z-axis movement between the two parts is prohibited. Further, secondary attachment means such as screws or rivets will not affect the X, Y or Z-axis alignment between the breaker cradle and back panel. The breaker cradle also includes breaker alignment flanges that prevent X-axis movement of the breaker with respect to the breaker cradle, as might be expected during a seismic event.


REFERENCES:
patent: 4181924 (1980-01-01), Thomas et al.
patent: 4183073 (1980-01-01), Clausing
patent: 4768131 (1988-08-01), Schultz et al.

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