Claims:We Claim:

1. A cam based locking mechanism (100) for a draw-out type circuit breaker (150), the draw-out type circuit breaker (150) being configured to rack in or out to or from a cradle (140), a racking handle (130) being inserted into the cradle (140) for engaging with a racking screw (120) and rotated to perform racking operation thereof, the cam based locking mechanism (100) being configured to block an insertion of the racking handle (130) into the cradle (140), the cam based locking mechanism (100) comprising:
a housing (90) being served as an enclosure, the housing (90) having an access hole (82) and an opening (84) configured thereon, the access hole (82) being adapted for inserting the racking handle (130) therethrough;
an actuator (80) being configured to slide in and out of the housing (90) through the opening (84) thereof, the actuator (80) having,
• a first surface (50) having at least one hole (45) configured thereon, and
• a second surface (70) being formed as a slot (60), the second surface (70) having a central notch (62), a top projection (64), a bottom projection (66), each projections (64, 66) having a first hole (68) configured thereon;
a blocker (40) being assembled into the slot (60) of the actuator (80), the blocker having a top end (32), a bottom end (34), each ends (32, 34) having a second hole (36) configured thereon;
a pivot pin (30) being slidably received within the slot (60) through the first holes (68) and the second holes (36) for assembling the blocker (40) therein;
a cam pin (25) being fixed to the housing (90) and slidably received within the central notch (62) for constraining movement of the actuator (80);
a reset spring (20) being operably connected with the pivot pin (30), the reset spring (20) having a reset rib (15) for retaining the cam based locking mechanism (100) in an unlocked condition; and
a lock (10) being inserted in the at least one hole (45) for locking the actuator (80),
wherein, when the actuator (80) is pulled out through the opening (84), the blocker (40) slides over the cam pin (25) and completely closes the access hole (82) thereby blocking the insertion of the racking handle (130) and when the actuator (80) slides in the housing (90), the access hole (82) opens, thereby allowing the insertion of the racking handle (130) for the racking operation.

2. The cam based locking mechanism (100) for the draw-out type circuit breaker (150) as claimed in claim 1, wherein the cam pin (25) and the reset rib (15) are used for actuating the blocker (40) to arrest the racking handle (130) in the access hole (82).

3. The cam based locking mechanism (100) for the draw-out type circuit breaker (150) as claimed in claim 1, wherein the blocker (40) is assembled in the slot of the actuator (80) by a drop pin technique using the pivot pin (30).

4. The cam based locking mechanism (100) for the draw-out type circuit breaker (150) as claimed in claim 1, wherein at least three holes (45) are configured on the first surface (50) of the actuator (80) to accommodate at least three locks (10) of saddle diameter from 4mm to 8mm therein.
, Description:CAM BASED LOCKING MECHANISM FOR DRAW-OUT TYPE CIRCUIT BREAKER

Field of the invention:

The invention relates generally to circuit breakers, and more particularly, to a locking mechanism for low voltage draw-out circuit breakers and switch board modules.

Background of the invention:

A draw-out mechanism is used to connect a circuit breaker to a main power source without unbolting/disturbing termination. An operator can rack in or out the circuit breaker to or from a cradle. The cradle has a jaw type spring contacts that is connected to the main power source. When the circuit breaker circuit breaker is racked in, plugs in the circuit breaker engage with the jaw contacts in the cradle, thus establishing a removable joint with the main power source.

The circuit breaker is racked in or racked out in three positions including an isolated position, a test position and a service position. In the isolated position, the circuit breaker is placed into the cradle. The secondary isolating contacts (SIC) get connected at the test condition and the power contacts get connected at the service condition. A racking handle is used to move the circuit breaker from one position to another. In order to avoid an unauthorized movement of the circuit breaker, a locking mechanism is used. The locking mechanism includes a padlock that arrests the insertion or rotation of the racking handle into the cradle. Based on the application, one or more padlocks can be used in on the same cradle.

However, following drawbacks are observed in existing prior art technologies:
1. As most of the padlocks are spring dependent, if the spring is failed in the padlock arrangement, the draw-out mechanism cannot be operated.
2. The padlocking of the draw-out mechanism is not possible in the panel door closed condition of the circuit breaker.
3. The padlock arrests the rotation of the racking screw, thereby damaging the racking mechanism.

Accordingly, there is need to provide a cam based pad locking mechanism for a draw-out type circuit breaker, that overcomes above mentioned drawbacks in the prior art.

Objects of the invention:

An object of the present invention is to provide a foolproof and integrated locking mechanism for a draw-out type circuit breaker.

Another object of the present invention is to improve safety of an operator while accessing the draw-out type circuit breaker.

Summary of the invention:

Accordingly, the present invention provides a cam based locking mechanism (hereinafter referred as, “the locking mechanism”) for a draw-out type circuit breaker (hereinafter referred as, “the circuit breaker”). The circuit breaker is configured to rack in or out to or from a cradle. A racking handle is inserted into the cradle for engaging with a racking screw. The racking screw includes a hexagonal socket for engaging the racking handle thereon. The racking handle is rotated to perform racking operation. The locking mechanism is configured to block an insertion of the racking handle into the cradle. The locking mechanism comprises a housing, an actuator, a blocker, a pivot pin, a cam pin, a reset spring and a lock.

The housing is served as served as an enclosure. The housing includes an access hole and an opening configured thereon. The access hole is adapted for inserting the racking handle therethrough. The actuator is configured to slide in and out of the housing through the opening thereof. The actuator includes a first surface having at least one hole configured thereon and a second surface being formed as a slot. The first surface may also include at least three holes configured thereon. The second surface includes a central notch, a top projection, a bottom projection configured thereon. Each projection includes a first hole configured thereon. The blocker is assembled into the slot of the actuator. The blocker has a top end and a bottom end. Each ends includes a second hole configured thereon. The pivot pin is slidably received within the slot through the first holes and the second holes for assembling the blocker therein. The blocker is assembled in the slot of the actuator by a drop pin technique using the pivot pin.

The cam pin is fixed to the housing. The cam pin is slidably received within the central notch for constraining movement of the actuator. The reset spring is operably connected with the pivot pin. The reset spring includes a reset rib for retaining the locking mechanism in an unlocked condition. The lock is inserted in the at least one hole for locking the actuator. At least three locks may also accommodate in the at least three holes of the first surface of the actuator. When the actuator is pulled out through the opening, the blocker slide over the cam pin and completely closes the access hole, thereby blocking the insertion of the racking handle. When the actuator slides in the housing, the access hole opens. The cam pin and reset rib are used for actuating the blocker to arrest the racking handle in the access hole, thereby allowing the racking operation.

Brief description of the drawings:

Figure 1A shows a perspective view of an unlocked condition of a draw-out type circuit breaker, in accordance with the present invention;

Figure 1B shows a front view of the unlocked condition of the draw-out type circuit breaker of the figure 1A;

Figure 2A shows a perspective view of a locked condition of the draw-out type circuit breaker, in accordance with the present invention;

Figure 2B shows a front view of the locked condition of the draw-out type circuit breaker of the figure 2A;

Figure 3 shows a schematic view of a cam based locking mechanism for the draw-out type circuit breaker, in accordance with the present invention;

Figure 4 shows a perspective view of a locked condition of the cam based locking mechanism of the figure 3; and

Figure 5 shows an exploded view of the cam based locking mechanism for the draw-out type circuit breaker, in accordance with the present invention.

Detailed description of the embodiments:

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 provides a cam based locking mechanism for a draw-out type circuit breaker. The cam based locking mechanism provides a foolproof and integrated padlock for a draw-out mechanism of the circuit breaker. The draw-out mechanism is pad locked in a panel door closed condition thereby improving user interface and safety of an operator.

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 figures 1 to 5, a cam based locking mechanism (100) (hereinafter referred as, “the locking mechanism (100)”)) for a draw-out type circuit breaker (150) (hereinafter referred as, “the circuit breaker (150)”)), in accordance with the present invention is shown. The circuit breaker (150) is configured to rack in or out to or from a cradle (140). A racking handle (130) is inserted into the cradle (140) for engaging with a racking screw (120). Specifically, the racking screw (120) includes a hexagonal socket (not numbered) for engaging the racking handle (130) thereon. The racking handle (130) is rotated to perform racking operation to move the circuit breaker (150) in different positions including an isolated position, a test position and a service position. For safety reasons, only authorized persons are allowed to operate circuit breaker (150) from the isolated position to the test and the service positions or vice versa.

The locking mechanism (100) is configured to block an insertion of the racking handle (130) into the cradle (140). The locking mechanism (100) comprises a housing (90), an actuator (80), a blocker (40), a pivot pin (30), a cam pin (25), a reset spring (20) and a lock (10). The housing (90) is served as an enclosure. The housing (90) includes an access hole (82) and an opening (84) configured thereon. The access hole (82) is adapted for inserting the racking handle (130) therethrough.

The actuator (80) is configured to slide in and out of the housing (90) through the opening (84) thereof. The actuator (80) includes a first surface (50) and a second surface (70). The first surface (50) includes at least one hole (45) configured thereon to accommodate the lock (10) therein. In an embodiment, the first surface (50) also includes at least three holes (45) configured thereon to accommodate at least three locks (10) therein. The second surface (70) is formed as a slot (60). The second surface (70) includes a central notch (62), a top projection (64), a bottom projection (66) configured thereon. Each projection (62, 64) includes a first hole (68) configured thereon. The blocker (40) is assembled into the slot (60) of the actuator (80). The blocker (40) has a top end (32) and a bottom end (34). Each ends (32, 34) includes a second hole (36) configured thereon. The pivot pin (30) is slidably received within the slot (60) through the first holes (68) and the second holes (36) for assembling the blocker (40) therein. In an embodiment, the blocker (40) is assembled in the slot (60) of the actuator (80) by a drop pin technique using the pivot pin (30).

The cam pin (25) is fixed to the housing (90). The cam pin (25) is slidably received within the central notch (62) for constraining movement of the actuator (80). The reset spring (20) is operably connected with the pivot pin (30). The reset spring (20) includes a reset rib (15) for retaining the locking mechanism (100) in an unlocked condition. In an embodiment, sliding walls (not numbered) of the housing (90) hold the reset rib (15) in the position. The lock (10) is inserted in the at least one hole (45) for locking the actuator (80).

In an operation, when the actuator (80) is pulled out through the opening (84), the blocker (40) slides over the cam pin (25). The blocker (40) completely closes the access hole (82), thereby blocking the insertion of the racking handle (130). When the actuator (80) slides in the housing (90), the access hole (82) opens. The cam pin (25) and reset rib (15) are used for actuating the blocker (40) to arrest the racking handle (130) in the access hole (82), thereby allowing the racking operation. In an embodiment, the blocker (40) is stopped by the racking handle (130), when the racking handle (130) is inserted. Hence, the actuator (80) cannot be operated, thereby ensuring the foolproof locking.

Advantages of the invention:

1. The locking mechanism (100) facilitates locking in a panel door closed condition to improve user interface.
2. The locking mechanism (100) allows the locking with at least three locks (10) in a panel door open condition as well as in the panel door closed condition.
3. The locking mechanism (100) arrests the insertion of the racking handle (130) so operating mechanism of the circuit breaker (150) is not stressed.
4. The locking mechanism (100) is an integrated feature of the draw-out mechanism, thus reduces the cost and improves the safety of the operator.
5. An abuse force acts on the blocker (40) is not transferred to the lock (10), thereby ensuring the reliability of the locking mechanism (100).
6. Even after the failure of the reset spring (20), the locking mechanism (100) can be operated by retaining primary functions thereof.
7. The cam pin (25) actuates the blocker (40) to provide the positive locking.

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.