DESC:Operating Mechanism for Secondary Isolating Contacts of Circuit Breaker

Field of the invention

The present invention relates to secondary isolating contacts of a draw-out module and more particularly, to an operating mechanism for the secondary isolating contacts of the circuit breaker.

Background of the invention

A draw-out circuit breaker includes a fixed unit and a movable unit. The fixed unit is attached with a panel. The movable unit is mounted on a guiding rail of the fixed unit. The circuit breaker has three distinct positions namely a service position, a test position and an isolated/disconnected position. The service position is achieved when power contacts and auxiliary contacts both are engaged. When the power contacts are disengaged and the auxiliary contacts are engaged, the test position is achieved. When both contacts are disengaged, the isolated position is achieved. These three distinct positions of the circuit breaker are achieved by using a racking mechanism of a cradle unit of the circuit breaker.

The circuit breakers are available in fixed and draw-out versions. In case of fixed breakers, for providing auxiliary supply, terminal blocks are mounted on the circuit breakers. But for draw-out circuit breakers, secondary isolating contacts (SIC) are used for providing the auxiliary supply. The length and size of the SIC depends on the travel of the draw-out circuit breaker from the test position to the service position and vice-versa. If the travel length of the draw-out circuit breaker is larger, the length of a pin for a plug-socket type SIC or the length of a contact strip for a sliding type SIC is large. Hence, for the larger travel from the test position to the service position of the circuit breaker, the size of the SIC is also large.
In present practice, a typical sliding mechanism exists with one subassembly mounted on the fixed unit and other subassembly mounted on the movable unit. But to adopt the variation or the mismatch between the fixed unit and the movable unit, the width of a sliding contact is made larger. Also, as the travel of the circuit breaker is large, the length of the contact is longer. Hence, the size of the SIC becomes larger to accommodate the mismatch and larger travel of the circuit breaker. Due to the compactness of the draw-out circuit breaker, numbers of the SIC are less in existing scenario. But the requirements of the numbers of contacts are increasing to provide supply to more number of accessories.

To accommodate higher numbers of contact in the limited space, the size of the SIC should be small. Due to larger travel of the draw-out circuit breaker, the length of the contact is also high.

Accordingly, there is a need to provide an operating mechanism that ensures proper engagement of secondary isolating contacts (SIC) and to use small SIC in a circuit breaker to overcome the drawbacks of the prior art.

Objects of the invention

An object of the present invention is to ensure proper engagement of secondary isolating contacts (SIC) of a circuit breaker at a test position and a service position.

Another object of the present invention is to ensure the standardization of the contacts for any circuit breakers having different lengths of travel from the test position to the service position.

Yet another object of the present invention is to reduce the size of the SIC for the circuit breaker which has higher travel from the test position to the service position.
Summary of the invention

Accordingly, the present invention provides an operating mechanism for secondary isolating contacts of a circuit breaker. The circuit breaker comprises a cradle unit and a breaker unit. The cradle unit comprises a guiding rail, a racking mechanism and terminals. The racking mechanism is capable of achieving a service position, a test position and an isolated/disconnected position of the circuit breaker.

The operating mechanism comprises a male secondary isolating contacts block (hereinafter “the male SIC block”), a female secondary isolating contacts block (hereinafter “the female SIC block”), a pair of first brackets, a second bracket, an upper bracket, a lower bracket, a pair of guiding pins, a pair of first springs, a pair of second springs and a pair of circlips. The male SIC block is mounted on the breaker unit. The male SIC block comprises a first housing and a first contact pin. The female SIC block is fixed with the cradle unit. The female SIC block comprises a second housing and a second contact pin. The operating mechanism further comprises a pin cage assembly for terminating a control wire of the male SIC block and the female SIC block. The pair of first brackets is fitted with the circuit breaker. The pair of first brackets is adapted for mounting the male SIC block thereon. The pair of first brackets includes a pair of holes configured thereon for fixing the pair of guiding pins.

The upper bracket is mounted on a top portion of the pair of first brackets and the lower bracket is mounted on a bottom portion of the pair of first brackets. The second bracket is fixed with the cradle unit. The second bracket is capable of fixing the female SIC block on the cradle unit. The pair of guiding pins is placed inside the pair of first brackets and fixed by using the pair of circlips. The pair of guiding pins is capable of guiding the male SIC block while traveling to and fro between the test position and the service position. The pair of first springs is attached and assembled around the pair of guiding pins. The pair of second springs is placed between the female SIC block and the second bracket such that the secondary isolating contacts gets aligned in three directions thereby making the female SIC block floating.

During a rack-in operation, when the circuit breaker moves from the test position to the service position, the first contact pin fully engages with the second contact pin and to accommodate the extra travel of the circuit breaker, the pair of first springs gets compressed and the male SIC block moves towards a front of the circuit breaker. Whereas, during a rack-out operation, when the circuit breaker travels from the service position to the test position, the pair of first springs releases energy and expands while the male SIC block remains stationary at an original position. The contact pins get disengaged only after full expansion of the pair of first springs and the male SIC block moves with the circuit breaker.

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 1 shows a perspective view of a circuit breaker at normal operating condition, in accordance with the present invention;

Figure 2 shows a perspective view of a cradle unit with a female secondary isolating contacts block mounted thereon, in accordance with the present invention;

Figure 3 shows a perspective view of a breaker unit with a male secondary isolating contacts block mounted thereon, in accordance with the present invention;
Figure 4 (a-j) shows an exploded view of various components of an operating mechanism, in accordance with the present invention;

Figure 5 shows a perspective view of the circuit breaker in an isolated/ disconnected position, in accordance with the present invention;

Figure 6 shows a perspective view of the circuit breaker in a test position, in accordance with the present invention; and

Figure 7 shows a perspective view of the circuit breaker in a service position, in accordance with the present invention.

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 embodiments.

The present invention discloses an operating mechanism for secondary isolating contacts (SIC) of a circuit breaker. The operating mechanism is a slider mechanism that allows engagement and disengagement of the SIC at desired positions like a service position, a test position and an isolated/disconnected position. The operating mechanism ensures engagement of the SIC at the test position and the service position and disengagement at the isolated/disconnected position. The operating mechanism is useful for proper alignments of the SIC and mounting any contact with variable engagement and disengagement criteria.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring to figure 1, a circuit breaker (200) at normal operating condition in accordance with the present invention is shown. In an embodiment, the circuit breaker (200) is a draw-out circuit breaker. The circuit breaker (200) comprises a cradle unit (50) and a breaker unit (100). The cradle unit (50) comprises a guiding rail (20), a racking mechanism (40) and terminals (not shown). The breaker unit (100) is mounted on the guiding rail (20). The racking mechanism (40) is used to achieve a service position, a test position and an isolated/disconnected position of the circuit breaker (200). The terminals are used to terminate external links for taking supply.

Referring to figures 2-7, an operating mechanism (150) for mounting secondary isolating contacts (hereinafter “the SIC”) in the circuit breaker (200) in accordance with the present invention is shown. Specifically, the operating mechanism (150) is a spring loaded mechanism that ensures proper engagement of the SIC in the circuit breaker (200). In an embodiment, a pin type (plug and socket type) SIC is used. The SIC is placed on both sides of the circuit breaker (200).

The operating mechanism (150) comprises a male secondary isolating contacts block (104) (hereinafter “the male SIC block (104)), a female secondary isolating contacts block (108) (hereinafter “the female SIC (108)), a pair of first brackets (112) (hereinafter “the first brackets (112)”), a second bracket (116), an upper bracket (120), a lower bracket (124), a pair of guiding pins (128), a pair of first springs (132), a pair of second springs (136) and a pair of circlips (140).

The male SIC block (104) comprises a first housing (not numbered) and a first contact pin (not numbered). The male SIC block (104) is mounted on the breaker unit (100) of the circuit breaker (200).
The female SIC block (108) is fixed with the cradle unit (50) of the circuit breaker (200) and assembled on the second bracket (116). The female SIC block (108) comprises a second housing (not numbered) and a second contact pin (not numbered). The operating mechanism further comprises a pin cage assembly (not shown) for terminating a control wire (not shown) of the male SIC block (104) and the female SIC block (108). During a rack-in operation of the circuit breaker (200), the first contact pin gets engaged with the second contact pin.

The first brackets (112) are fitted with the circuit breaker (200). The upper bracket (120) is mounted on a top portion (not numbered) of the first brackets (112) and the lower bracket (124) is mounted on a bottom portion (not numbered) of the first brackets (112). The male SIC block (104) is mounted on the first brackets (112) with the help of the upper bracket (120) and the lower bracket (124). The male SIC block (104) is attached between the upper bracket (120) and the lower bracket (124). The upper bracket (120) and the lower bracket (124) are used for guiding the male SIC block (104). The first brackets (112) includes a pair of holes (not numbered) configured thereon for fixing the pair of guiding pins (128).

The pair of guiding pins (128) is used for guiding the male SIC block (104) while traveling to and fro between the test position and the service position. The pair of guiding pins (128) is placed inside the first brackets (112) and fixed by using the pair of circlips (140).

The pair of first springs (132) is attached and assembled around the pair of guiding pins (128). During the rack-in operation of the circuit breaker (200), the pair of first springs (132) gets compressed when both the contact pins of the SIC blocks (104, 108) are fully engaged to accommodate the extra travel of the circuit breaker (200). When the circuit breaker (200) is racked-out from the service position to the test position, the pair of first springs (132) releases energy and helps to move the male SIC block (104) to an original position.

The second bracket (116) is fixed with the cradle unit (50) and used for fixing the female SIC block (108) on the cradle unit (50). The pair of second springs (136) is attached with the second bracket (116). In an embodiment, the pair of second springs (136) is placed between the second bracket (116) and the female SIC block (108) such that the SIC gets aligned in three directions thereby making the female SIC block (108) floating. The pair of second springs (136) is fixed from both sides with the help of screws (not shown). The pair of second springs (136) is used to absorb the mismatch between the male SIC block (104) and the female SIC block (108) (hereinafter “the floating female SIC block (108)”).

Rack-in operation:

Figure 5 shows the isolated/disconnected position of the circuit breaker (200) where both the SIC blocks (104, 108) are disengaged from each other. During the rack-in operation of the circuit breaker (200), the breaker unit (100) moves towards the cradle unit (50). Before the circuit breaker (200) reaches the test position, both the housings of the SIC blocks (104, 108) get engaged and aligned. The floating female SIC block (108) mounted through the pair of second springs (136) helps the housings and the contact pins of the SIC blocks (104, 108) to get aligned. The contact pins of the SIC blocks (104, 108) are engaged with each other before the circuit breaker (200) reaches to the test position.

When the circuit breaker (200) reaches the test position, the SIC blocks (104, 108) get engaged at the test position as shown in figure 6. However, the pair of first springs (132) is not compressed. During the rack-in operation from the test position to the service position, the first contact pin of the male SIC block (104) fully engages with the second contact pin of the female SIC block (108). Then to accommodate the extra travel of the circuit breaker (200), the pair of first springs (132) gets compressed and the male SIC block (104) moves towards a front of the circuit breaker (200). At the service position, the contact pins get engaged and the pair of first springs (132) is compressed.
Rack-out operation:

Again referring to figure 5, in the rack-out operation of the circuit breaker (200), the breaker unit (100) moves out of the cradle unit (50). During the travel from the service position to the test position, the pair of first springs (132) releases energy and expands, while the male SIC block (104) remains stationary and the contact pins gets disengaged only after full expansion of the pair of first springs (132) and the male SIC block (104) moves with the circuit breaker (200).

During the travel from the test to the isolated/disconnected position, the contact pins get disengaged and the housings of the SIC blocks (104, 108) come out as shown in Figure 4. The operating mechanism (150) helps to use the smaller length pin inspite of large travel of the circuit breaker (200).

Advantages of the invention

1. The operating mechanism (150) ensures proper engagement of the SIC at the test position and the service position.
2. The operating mechanism (150) ensures the use of the smaller length pin (plug-socket) of the SIC, for long travel of the circuit breaker (200).
3. The operating mechanism (150) ensures the standardization of the contact for any circuit breakers having different length of travel from the test position to the service position and adjusts variation in travel of the circuit breaker.
4. The operating mechanism (150) ensures proper alignment of the SIC of the plug-socket type.
5. The operating mechanism (150) reduces the length of the contact pins and the housings of the SIC blocks (104, 108) by using spring compression mechanism.
6. The operating mechanism (150) is useful in any type of draw-out module and has simple construction and is easy to mount.
7. The operating mechanism (150) helps to accommodate higher numbers of contacts by using small SIC blocks (104, 108), making separate alignment arrangements for the SIC.
8. The pair of first springs (132) attached and assembled around the pair of guiding pins (128) ensures the use of smaller length pin (plug-socket) of the SIC for long travel of the circuit breaker (200) and also, ensures the standardization of the contact for any circuit breakers having different length of travel from the test position to the service position and adjusts variation in travel of the circuit breaker (200).

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. An operating mechanism (150) for secondary isolating contacts of a circuit breaker (200), the circuit breaker (200) having a cradle unit (50) and a breaker unit (100), the cradle unit (50) having a guiding rail (20), a racking mechanism (40) and terminals, the racking mechanism (40) being capable of achieving a service position, a test position and an isolated/disconnected position of the circuit breaker (200), the operating mechanism (150) comprising:
a male secondary isolating contacts block (104) mounted on the breaker unit (100), the male secondary isolating contacts block (104) having a first housing and a first contact pin;
a female secondary isolating contacts block (108) fixed with the cradle unit (50), the female secondary isolating contacts block (108) having a second housing and a second contact pin;
a pair of first brackets (112) fitted with the circuit breaker (200), the pair of first brackets (112) adapted for mounting the male secondary isolating contacts block (104) thereon, the pair of first brackets (112) having a pair of holes configured thereon;
an upper bracket (120) mounted on a top portion of the pair of first brackets (112);
a lower bracket (124) mounted on a bottom portion of the pair of first brackets (112);
a second bracket (116) fixed with the cradle unit (50), the second bracket (116) being capable of fixing the female secondary isolating contacts block (108) on the cradle unit (50) ;
a pair of guiding pins (128) placed inside the pair of first brackets (112) and fixed by using a pair of circlips (140), the pair of guiding pins (128) being capable of guiding the male secondary isolating contacts block (104) while traveling to and fro between the test position and the service position;
a pair of first springs (132) attached and assembled around the pair of guiding pins (128); and
a pair of second springs (136) placed between the female secondary isolating contacts block (108) and the second bracket (116),
wherein, during a rack-in operation, when the circuit breaker (200) moves from the test position to the service position, the first contact pin fully engages with the second contact pin and to accommodate the extra travel of the circuit breaker (200), the pair of first springs (132) gets compressed and the male secondary isolating contacts block (104) moves towards a front of the circuit breaker (200),
wherein, during a rack-out operation, when the circuit breaker (200) travels from the service position to the test position, the pair of first springs (132) releases energy and expands while the male secondary isolating contacts block (104) remains stationary and the contact pins gets disengaged only after full expansion of the pair of first springs (132) and the male secondary isolating contacts block (104) moves with the circuit breaker (200).

2. The operating mechanism (150) as claimed in claim 1, wherein the pair of holes are configured on the pair of first brackets (112) for fixing the pair of guiding pins (128).

3. The operating mechanism (150) as claimed in claim 1, wherein the pair of second springs (136) is placed between the second bracket (116) and the female secondary isolating contacts block (108) such that the secondary isolating contacts gets aligned in three directions thereby making the female secondary isolating contacts block (108) floating.

4. The operating mechanism (150) as claimed in claim 1 further comprises a pin cage assembly for terminating a control wire of the male secondary isolating contacts block (104) and the female secondary isolating contacts block (108).