FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
SAFETY MECHANISM FOR OPERATOR OF SWITCHING DEVICE;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT
IS TO BE PERFORMED. 1

FIELD OF INVENTION:
The present invention relates to motor driven apparatus for operating the handle of electrical switching device and more particularly to the safety mechanism for motor operator.
PRIOR ARTS:
Switching devices such as circuit breakers and contactors may be operated manually or with help of apparatus, which are run with help of a motor. Such apparatus have come to be known as motor operators. Motor operators usually contain motor and gear arrangements to result in switching of the switching device connected to them.
Such apparatus are used in industrial applications, requiring compliance with stringent safety requirements. Accordingly, a safety feature is provided in US 5693923 which discloses a motor operator unit for an electrical switch is pivotally mounted on a bracket to swing between a closed, operative position in which an actuator in the motor operator unit engages the switch handle for electrical operation of the switch handle and an open position in which the switch handle is freely accessible for direct manual operation. The compliant actuator which is translated by a motor driven threaded shaft overtravels at each end of its reciprocal path after actuation of the switch handle to toggle a single power switch which determines both direction and shutoff of motor operation. A lockout plate mechanically prevents electrical and manual operation of the switch handle and carries an interlock switch, which only enables motor operation when the motor operator unit is in the operative position and not locked out. The actuator is configured to prevent full rotation of the motor operator to the operative position, if the position of the
2

actuator, which is virtually identified by indicators, does not correspond to handle position.
In US 5693923 a lockout plate with interlock switch are provided which are used to prevent operation of motor operator. It only enables motor operation when the motor operator unit is in the operative position
In US 5693923, a switch, which is in series with the motor, is actuated by cam on the mounting bracket of motor operator when motor operator is engaged with the mounting bracket.
However, no accurate operative position determination is made available. Also, such arrangement allows chances of accessibility of moving actuator at the bottom of motor operator.
Therefore, there is a requirement of a safety mechanism providing accurate and stringent performance.
SUMMARY
The present invention provides a safety mechanism for a motor operator. As per one embodiment of the present invention the safety mechanism allows for operation of the motor operator only when the motor operator is rightly mounted on the switching device.
Embodiments of the present invention may be incorporated in various motor operators. Further, the various embodiments allow modification of the safety mechanism based on the switching device, which is driven by the motor operator.
3

A simple safety mechanism provides a highly accurate and stringent operational condition for the motor operator. This allows operation of the motor operator only when rightly placed on the switching device. Improved safety is provided to avoid accidents or malicious operation of the motor operator and the switching device.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig.l shows the safety mechanism as per one embodiment of the present invention, placed in a motor operator, which is further placed on a switching device.
Fig.2a shows the safety mechanism as per one embodiment of the present invention.
Fig. 2b shows an exploded view of the safety mechanism as per one embodiment of the present invention.
Fig. 3 a shows as per one embodiment of the present invention the safety mechanism during non-operational condition, while the actuator is in lowest position.
Fig. 3b shows as per one embodiment of the present invention the safety mechanism during operational condition
Fig. 3b shows as per one embodiment of the present invention the safety mechanism during non-operational condition, while the actuator is at the uppermost position.
Fig. 4 shows a motor operator embodying the safety mechanism as per one embodiment of the present invention.
4

DETAILED DESCRIPTION OF THE INVENTION
A safety mechanism for motor operator is described. As per one embodiment of the present invention the safety mechanism allows for operation of the motor operator only when the motor operator is rightly mounted on the switching device.
Fig.l shows the safety mechanism (101) placed in a motor operator (103), which is further placed on a switching device (105) for example a circuit breaker. The safety mechanism is designed to sense the placement of the motor operator on the switching device. A cover (107) is provided to engage with the safety mechanism.
As per one embodiment of the present invention a safety mechanism (101) is as shown in fig.2 (a). A housing (12) is provided allowing placement of an actuator (21). A biasing means (31) is provided affecting the motion of the actuator (21). Further, a micro switch (41) is provided to sense the motion of the actuator (21) and provide corresponding signaling for operation of motor operator.
Fig. 2(b) shows an exploded view of the safety mechanism as per one embodiment of the present invention. The housing (12) is provided to have a base (14), which is fixed in the motor operator, the mechanism is used in. Pair of members (16) are provided to be on the base (14) such that the actuator (21) may slide between them. The pair of members (16) may be C-shaped as shown in figure 2(b). Further, the movement of the actuator may be restricted beyond certain limit by a stopper (19) provided in the pair of members (16).
The actuator (21) is provided to have an actuator lever (23), which may slide out of the base (14). The motion of the actuator in the pair of members (16) is required to be
5

corresponded with the micro switch (41). An arm (27) is provided at one side of the actuator (21) towards the micro-switch (41) that engages with the micro switch during certain conditions. On the other side of the actuator a hooking member (25) is provided permanently attached to actuator providing a hole (25b) for engaging one end (31a) of the biasing means (31). The other end (31b) of the biasing means is attached to the base of the housing. The biasing means (31) may be a tension spring or a leaf spring. Alternatively, any biasing means may be provided to support biasing characteristics as described.
A supporting member (18) is provided in the housing (12) to support the micro-switch (41). The micro-switch lever (43) is provided to engage with the arm (27) of the actuator (21). A roller (43a) may be provided on the head of the lever (43) for smooth movement of the actuator (12).
Various positions of the safety mechanism as per one embodiment of the present invention are as shown in fig. 3. Fig. 3a shows the position of the safety mechanism wherein the actuator (12) is at the lowest position under the influence of the biasing means (31). This position corresponds to a default non-operational condition wherein the actuator lever (23) is not pressed by any external object. The lever (43) of the micro-switch is not in engagement with the arm (27) of the actuator (12). The micro-switch therefore is OFF, thereby not allowing the motor operator to operate.
Fig. 3b shows as per one embodiment of the present invention, the position of the safety mechanism wherein an external force is acted on the actuator lever (23). During such position of the actuator the motor operator is in operational condition. Referring to figure 1, the external force is applied from the cover (107) of the switching device.
6

Referring to fig. 3b, the micro-switch (41) allows accurate sensing of the actuator position. In one embodiment of the present invention the height of the arm (27) is provided to be 3mm. This provides for a very precise and stringent position of actuator (12) for which the motor operator is operable, thereby improving the safety. During this position of the safety mechanism the micro-switch is ON, allowing operation of motor in the motor operator. This position of the arm (27) may be configured based on various switching device.
The external force being applied at the lever (23) of the actuator is repelled by the biasing means (31) thereby not allowing free upward motion of the actuator. During the placement of the motor operator on the switching device the force exerted by the biasing mechanism (31) is balanced by the external force exerted on the lever (23). This keeps the motor operator operational during such position.
Fig.3(c) shows, as per one embodiment of the present invention, the position of the safety mechanism wherein the actuator slides to the uppermost position wherein the arm (27) of the actuator is not in contact with the lever (43) of the micro-switch (41). In this position, the arm (27) slides past the lever (43). Such a position may arise from irregular placement of the motor operator. In such conditions the motor operator is restricted from operating. As seen in the figure, the micro-switch (41) is OFF thereby not allowing operation of motor operator.
Fig. 4 shows one embodiment of the motor operator comprising the safety mechanism (180). The motor operator (100) comprises of a carriage (190) to support the motor operator. The safety mechanism is placed at the bottom of the motor operator such
7

that the actuator lever senses the placement of the motor operator on the switching device. Such safety mechanism may be applied to various types of motor operators.
The invention provides a simple and accurate safety mechanism for the motor operator. The motor operator is operational only when mounted on the switching device without any irregularities. Also, malicious operation of the motor operator is also avoided
since the operation of the micro-switch is made possible in very precise position of the actuator.
8

WE CLAIM:
1. A safety mechanism for a motor operator, comprising:
an actuator;
an actuator lever at bottom of the actuator adapted to sense the placement of
the motor operator from a switching device cover;
a housing adapted to allow vertical movement of the actuator;
an arm provided on one side of the actuator;
a micro switch attached to the said housing;
a lever of the micro-switch adapted to engage with said arm of the actuator to
bring the motor operator into operational condition;
a biasing means adapted to bring the actuator to a lowest position wherein the
motor operator is non-operational.
2. The safety mechanism of claim 1, further comprising a roller on the lever adapted to roll along the surface of the arm.
3. The safety mechanism of claim 1, further comprising a stopper in the housing restricting upward motion of adapter beyond topmost position.
4. The safety mechanism of claim 1, wherein the biasing means is a tension spring.
5. A motor operator for switching a switching device comprising the safety mechanism as claimed in claim 1.
Dated this 27th day of February, 2007

9

ABSTRACT
A safety mechanism for motor operator is described. As per one embodiment of the present invention the safety mechanism allows for operation of the motor operator only when the motor operator is rightly mounted on the switching device.
10