Patent Application
20070205086
1. Technical Field
The disclosure contained in this document relates to a linkage for reducing the forces on rotating mechanisms, and particularly to a linkage for connecting the operating mechanism of a high voltage circuit breaker or recloser to interrupters.
2. Description of the Related Art
High voltage circuit breakers are used in the distribution of three phase electrical energy to prevent the flow of current in a circuit when a fault or other disturbance is detected. When a sensor or protective relay detects a fault or disturbance in the circuit, current-carrying contacts in each of the three phases are physically separated to prevent current flow until the circuit is clear. A recloser is similar to a circuit breaker, except that a circuit breaker opens a circuit and keeps it in the open position indefinitely, but a recloser may open and reclose the circuit several times in quick succession to allow a temporary fault to clear. (As used herein, the term “circuit breaker” may refer to either a circuit breaker or recloser.) A circuit breaker or recloser includes interrupters for physically separating the current-carrying contacts and an operating or switching mechanism for providing the energy necessary to accomplish separation of the contacts.
A linkage is provided for mechanically coupling the operating mechanism to each of the interrupters. In general, the linkages or mechanical couplings may be one of several types. For example, in a “push/pull” type coupling, conductive elements are moved into engagement when a rigid rod is moved in one direction, and the coupling elements are disengaged when the rod is moved in the opposite direction. In a rotational coupling, one of the conductive elements moves in response to the rotation of a bell crank as a link element between the three phases of the breaker rotates.
In a circuit breaker having a rotational linkage, the mechanical coupling may include one or more connecting rods, each connected at one end to an operating mechanism and at the other end to a lever. Each lever is connected to a linking element which rotates in response to pivotal movement of the lever due in turn to linear movement of the connecting rod. The linking element may be coupled to bell cranks provided in the terminal portion of the interrupters which pivot in response to rotation of the linking elements to open and close the contacts of the interrupters.
An example of such a mechanical coupling is illustrated in U.S. Pat. No. 5,569,891.
Very high forces can be generated in the linkages and levers of the mechanical coupling of high voltage circuit breakers, especially as the voltage rating of the circuit breaker increases. These high loads will create excessive stresses in the circuit breaker components and also cause flexing in these components that adversely affects motion of the interrupter. Accordingly, these components must be made massive unless something is done to otherwise contain the high forces. There is a need therefore to avoid the expense of making high voltage circuit breaker components massive as the voltage rating of the circuit breaker increases.
In one embodiment, a force containment arm is provided for containing forces acting on a rotatable shaft. The force containment arm has a head with a cylindrical opening for encircling the rotatable shaft and a bearing structure on an inner surface bounding the cylindrical opening, a connector for connecting the arm to a support frame and a stud connecting the connector to the head. In some embodiments the stud may be adjustable for adjusting the distance between the head and the connector.
In another embodiment, a linkage assembly is provided which includes a coupler for connecting two rotatable shaft portions end-to-end. The coupler has a lever for connection to an input mechanism for rotating the shaft. A pair of force containment arms is mounted on the coupler for containing reaction force acting on the shaft and other components connected to the shaft. Each force containment arm has a head with a cylindrical opening for encircling the coupler, a connector for connecting the arm to a support frame and a stud connecting the connector to the head. The head has a bearing structure on an inner surface bounding the cylindrical opening for contact with the coupler. In some embodiments, the stud may be adjustable for adjusting the distance between the head and the connector. In still other embodiments, one or more containment arms may be mounted on the rotatable shaft instead of on a coupler.
In still another embodiment, a high voltage circuit breaker is provided which includes at least one interrupter for opening an electrical circuit, an operating mechanism for actuating the interrupter, a frame for support of the operating mechanism and interrupter, and a mechanical linkage for coupling the operating mechanism to the interrupter. The mechanical linkage includes a rotatable shaft, a lever for rotating the shaft in response to the operating mechanism, a crank connected to the rotatable shaft for actuation of the interrupter, and at least one force containment arm connected to the rotatable shaft and the frame, said force containment arm having a head with a cylindrical opening for encircling said rotatable shaft and a bearing structure on an inner surface bounding the cylindrical opening, a connector for connecting the arm to a support frame and a stud connecting the connector to the head. In some embodiments, a pair of force containment arms is mounted on the rotatable shaft in spaced relation on opposite sides of the lever. In the latter embodiment, a lateral brace may be provided for attachment to each of the containment arms.
Before explaining at least one embodiment in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. For example, all singular forms and the words “a,” “an,” and “the” include the plural reference unless expressly stated otherwise.
Referring to
Referring to
In some embodiments, weather seals may be provided on each side of the bearing to prevent contamination of the bearing. Flexible lip seals, preferably made of a rubber compound, although other flexible materials are possible, are most suited for this purpose. In some embodiments connector 134 may comprise a clevis or other device for connecting the force containment arm to frame 114 near the output shaft of operating mechanism (118 in
In various embodiments, shaft 136 may comprise a solid, corrosion-resistant or plated metal such as stainless steel, a plated steel or high strength aluminum.
In some embodiments the head 132 may comprise two portions 144 and 146 connected by a pin 148 secured by a cotter pin 150. This makes mechanical assembly easier in situations where space is limited. In other embodiments the two head portions may be connected by a bolt and nut, screw or other connector. Similarly, a pin 152, bolt or other connector may be used to attach the connector 134 to frame 114 or other support structure. Referring to
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which are also intended to be encompassed by the following claims.
