Electricity: conductors and insulators – Boxes and housings – With electrical device
Patent
1996-04-01
1998-04-14
Kincaid, Kristine L.
Electricity: conductors and insulators
Boxes and housings
With electrical device
220 402, H02G 318
Patent
active
057394679
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a modular electric apparatus, in particular of the type for rail installation, provided with inherently fingerproof protection for clamp terminals.
It is known that modular electric apparatus designed for assembly into electric systems are provided with clamp terminals for electrical connection to cables which may have large cross-sectional areas.
The clamps include a jaw or fixed element made of a conductive material and an opposite movable jaw which is moved toward the fixed element by means of a screw to clamp the ends of a conductor in the gap therebetween, thereby securing the conductor mechanically in electrical communication with the fixed conductive element.
The clamp terminals are housed within an insulating plastics casing of the apparatus which provides electrically live parts with a measure of protection from incidental shocks.
However, that protection cannot be made comprehensive because openings have to be left both to operate the clamping screws and for introducing the conductor ends through their respective clamp terminals.
For the clamping screws, such compact tools as Phillips or Allen drivers may be used.
In this case, the access openings for the screws may be made small enough to prevent a finger from getting in, whether by accident or deliberately, of an operator who may be the installer himself or a user given access to the system.
For this purpose, a maximum size has been set for the opening which will comply with this safety requisite, and a standard tool, called the "reference finger" provided for compliance checking.
This requisite cannot generally be met in the instance of openings designed for passing cable ends through to the clamp terminals because these openings are to allow for comfortable introduction of cable ends of large cross-sectional area as well.
Thus, clamp terminals are fingerproofed by means of devices of a secondary type and less than fully satisfactory, such as removable caps of an insulative material applied to the clamp openings or removable protection screens spanning the whole electric panelboard rather than a specific opening.
The risk of incidental contact with the live parts, albeit minor, has not been removed entirely and poses a significant safety problem to the operator.
This problem compounded by that of the proper fitting of the cable ends in the clamp terminals.
The through openings for the cable ends do not allow, under normal installation conditions, for the open or closed state of the clamps to be observed.
Thus, cable ends may be passed through the openings, and rather then enter the jaws for clamping, get misled through the clearance space provided in the apparatus for the jaws, with the result that actual and effective electrical connection of the cable ends to the clamps cannot be ensured.
These problems are solved according to the invention by a modular electric apparatus having an inherently fingerproof protective arrangement for the clamp terminals and comprising a diaphragm of an insulative material slidable within a grooved seat at the clamp opening and driven by the movable jaw as a shutter with variable closure setting according to the position of the movable jaw to only give access, through the opening, to the space between the jaws and to screen off live parts facing toward the opening.
The features and advantages of the invention will be apparent from the following description of a preferred embodiment of the invention and the accopanying drawings, in which:
FIG. 1 is a perspective view of a modular electric apparatus;
FIG. 2 is an exploded perspective view of a detail of the apparatus with inherent protection according to the invention.
FIG. 1 is a perspective view showing schematically a prior art modular electric apparatus for rail installation.
The apparatus 1 has a shape in the general form of a flattened parallelepipedon and is provided with a front wall 2 generally carrying actuation handles and pushbuttons and a back wall formed with rail-hooking teeth.
The top wall 3 is formed with an openin
REFERENCES:
patent: 3803342 (1974-04-01), Stearley et al.
patent: 4605816 (1986-08-01), Jorgensen et al.
patent: 4700437 (1987-10-01), Hoshino
patent: 4929198 (1990-05-01), Strate et al.
patent: 5495659 (1996-03-01), Beakes et al.
Bticino S.P.A.
Kincaid Kristine L.
Patel Dhiru R.
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