DESC:Cable Terminal Box Assembly

Field of the invention

The present invention relates to electrical switches and more particularly, to a cable terminal box assembly for a molded case circuit breaker.

Background of the invention

In cable terminal box assembly of molded case circuit breakers (herein after ‘the MCCB’), a cable is not in direct connection with a terminal. Instead, the cable includes an insulated conductor (spreader link) located inside them for connecting to the terminal. The conductor insulation is removed far enough to allow the conductor to enter the terminal and then tightened in a box clamp by a screw. It is important that the joint between the conductor and the terminal is electrically and mechanically sound without putting undue pressure on the conductor or the terminal.

In order to check the strength of the joint between the conductor and the terminal, the cables are subjected to a pull out test and a short-circuit testing of the MCCB as per standard (IEC 60947-1). In the pull out test, a suitable length of the conductor is secured inside the terminal and a pulling force without jerks for 1 minute is applied in a direction opposite to that of the insertion of the conductor. During the test, the conductor should bear a high pressure/load and shall not slip.

However, the contact surfaces of the terminal and the conductor of the prior art are flat and get separated by the pulling force. Due to lack of friction between the terminal and the conductor against the pulling force, the strength between the terminal and the cable weakens causing the cable to slip out even after being tightened by the box clamp.

Accordingly, there is a need to provide a cable terminal box assembly having an improved conductor-terminal strength that overcomes the problems of the prior art.

Objects of the invention

An object of the present invention is to increase conductor-terminal strength of molded case circuit breakers (MCCB).

Another object of the present invention is to make a cable of a cable terminal box assembly of the MCCB bear a high pressure during a pullout test and a short circuit testing.

Summary of the invention

Accordingly, the present invention provides a cable terminal box assembly. The cable terminal box assembly comprises a terminal, a cable and a box clamp. The cable includes at least one conductor located therein. The at least one conductor includes a flange configured therein. The at least one conductor is adapted for securely entering into the terminal.

The box clamp interlocks the at least one conductor therein. The box clamp includes a groove corresponding to the flange on the at least one conductor. The groove is configured on a bottom wall of the box clamp. When the at least one conductor is anchored and tightened in the box clamp, the flange interlocks with the groove thereby strengthening the connection between the at least one conductor and the terminal. The at least one conductor is tightened in the box clamp by a screw.

Brief description of the drawings

Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:

Figure 1a shows a front view of at least one conductor of a cable terminal box assembly, in accordance with the present invention;

Figure 1b shows a box clamp of the cable terminal box assembly, in accordance with the present invention;

Figure 1c shows a front view of the box clamp of figure 1b;

Figure 1d shows a side view of the box clamp of figure 1b; and

Figures 2 and 3 are schematic views of the cable terminal box assembly showing interlocking between a flange of the at least one conductor and a groove of the box clamp.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a cable terminal box assembly for a molded case circuit breaker (MCCB). The cable terminal box assembly provides a conductor-terminal having an improved strength. The cable terminal box assembly provides a cable that bears high pressure during a pullout test and a short circuit testing of the MCCB.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

Referring to figures 1a-3, a cable terminal box assembly (100) (herein after ‘the assembly (100)’) for a molded case circuit breaker (not shown) (herein after ‘the MCCB’) in accordance with the present invention is shown. The assembly (100) comprises a terminal (10), a cable (not shown) and a box clamp (30).

The cable is flexible and rigid and includes at least one conductor (20) (alternately referred as a spreader link) located therein. The at least one conductor (20) is made up of copper or aluminium metal. However, it is understood that the cable may include a plurality of conductors that are made up of any suitable material in accordance with other alternative embodiments of the assembly (100). The at least one conductor (20) includes a flange (15) configured therein as shown in figure 1b. The flange (15) is in the form of a protuberant bulge. The at least one conductor (20) is adapted for securely entering into the terminal (10). The assembly (100) includes silver, nickel plated or bare copper terminal (10).

The box clamp (30) interlocks the at least one conductor (20) therein. The box clamp (30) includes two side walls (22), a top wall (24) and a bottom wall (26). The top wall (24) includes a central opening (23) as shown in figures 1b-1d. The bottom wall (26) includes a groove (25) corresponding to the flange (15) on the at least one conductor (20). The groove (25) is in the form of a pit/depression.
Specifically, the groove (25) is configured on a middle surface (not numbered) of the bottom wall (26) of the box clamp (30).

When the at least one conductor (20) is inserted in the box clamp (30) through the side wall (22) and tightened in the central opening (23) on the top wall (24) such that the flange (15) interlocks with the groove (25) thereby strengthening the connection between the at least one conductor (20) and the terminal (10). In an embodiment, the at least one conductor (20) is tightened in the box clamp (30) by a screw (not shown). Thus, the flange (15) and the groove (25) provide locking to the terminal (10) and the conductor (20) in the box clamp (30). Due to improved slipping strength between the at least one conductor (20) and the terminal (10), the cable bears high pressure during a pullout test and a short circuit testing of the MCCB.

Advantages of the invention

1. The assembly (100) prevents the cable from slipping out during the pull out testing or in case of fault and thus ensures the safety of human beings.
2. The assembly (100) improves the strength between the at least one conductor (20) and the terminal (10) due to interlocking of the flange (15) on the at least one conductor (20) and the groove (25) on the box clamp (30).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:We claim:

1. A cable terminal box assembly (100) comprising:
• a terminal (10);
• a cable having at least one conductor (20) located therein for
securely entering into the terminal (10); and
• a box clamp (30) interlocking the at least one conductor (20)
therein,
characterized in that, the at least one conductor (20) having a flange (15) and the box clamp (30) having a groove (25) corresponding to the flange (15) such that when the at least one conductor (20) is anchored and tightened in the box clamp (30), the flange (15) interlocks with the groove (25) thereby strengthening the connection between the at least one conductor (20) and the terminal (10).

2. The cable terminal box assembly (100) as claimed in claim 1, wherein the
groove (25) is configured on a bottom wall (26) of the box clamp (30).

3. The cable terminal box assembly (100) as claimed in claim 1, wherein the
at least one conductor (20) is tightened in the box clamp (30) by a screw.