Patent Application
20070080766
1. Field of the Invention
The present invention relates generally to under-voltage release mechanisms and, more particularly, to a shock-resistant under-voltage release mechanism having a shock-resistant tripping device.
2. Background Information
Numerous types of circuit breakers are known and understood in the relevant art. A circuit breaker is typically configured to interrupt a circuit in response to a trip event (e.g., without limitation, an over-current condition; an under-voltage condition). Generally, circuit breakers include a moveable contact that is placed into electrical contact with a stationary contact to complete an electrical circuit. When desired, a tripping mechanism moves the moveable contact away from the stationary contact to interrupt the electrical circuit. Numerous types of tripping mechanisms are known.
In one type of tripping mechanism, for example, one or more trip buttons are provided which, when activated, cause a trip bar to rotate. Rotation of the trip bar causes an interruption mechanism to operate, thereby moving the moveable contact away from the stationary contact. The trip button(s) may be depressed manually, or by a plunger of a trip mechanism, or may be operated by other electrical apparatus as needed for the specific application. One such type of trip mechanism, for example, is an under-voltage release mechanism. An example of an under-voltage release mechanism may be found in U.S. Pat. No. 6,255,924 to Turner et al. which is incorporated herein by reference.
The under-voltage release mechanism employs a tripping device that includes a coil, a magnetically permeable core, and a magnetically permeable and movable plunger, as is generally known and understood in the relevant art. When the circuit breaker is in operation and the movable contact is engaged with the stationary contact, the coil of the tripping device is energized. A magnetic field is generated by the coil which causes the plunger to be biased against a spring. When the circuit voltage is greater than a given preset level, the magnetic field generated by the coil magnetically interacts with the plunger and overcomes the force of the spring such that the plunger is retained in a retracted position (i.e., the plunger is kept away from the trip button). When the circuit voltage drops below the given preset level, however, the magnetic field generated by the coil is insufficient to overcome the force of the spring. Accordingly, the spring biases the plunger into an extended position where the plunger engages the trip button, which, in turn, initiates rotation of the trip bar in order to interrupt the electrical circuit.
While generally effective, such under-voltage release mechanisms are unsuitable for some applications. For instance, circuit breakers employing such under-voltage release mechanisms may be subject to relatively high levels of shock-loading which cause such under-voltage release mechanisms to inadvertently and inappropriately trip the circuit breaker.
Thus, a need exists for an improved shock-resistant under-voltage release mechanism having a shock-resistant tripping device.
These needs and others are met by the present invention, which is directed to a tripping device comprising a coil frame, a coil, a plunger, a spring, and an anti-shock device. The coil is fixedly coupled to the coil frame and has a cylindrical channel extending therethrough. The plunger is reciprocatingly received within the cylindrical channel and the spring is structured to bias the plunger within the cylindrical channel. The anti-shock device includes at least one of a number of anti-shock devices structured to eliminate movement of the coil relative to the coil frame or a number of anti-shock devices structured to eliminate movement of the plunger relative to the cylindrical channel.
As another aspect of the invention, an under-voltage release mechanism comprises a mounting bracket, a tripping device, and an angled support. The mounting bracket includes a first portion and a second portion, the second portion being normal to the first portion. The tripping device is fixedly coupled to the mounting bracket. The angled support is fixedly coupled to the mounting bracket between the first and second portions. The angled support is structured to prevent flexing of the mounting bracket.
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
Directional phrases used herein, such as, for example, left, right, clockwise, counterclockwise, top, bottom, up, down, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
As employed herein, the term “number” shall mean one or more than one.
As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined together through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly.
In the current embodiment, the plunger spring 13 is of a generally helical design and is structured to be received by the plunger 11. As discussed above, the first end of the plunger spring 13 engages the first surface of the cap 23. A second end of plunger spring 13 engages a washer 14 which is placed between the plunger spring 13 and the coil frame 17. When compressed, the plunger spring 13 biases the plunger 11 to reciprocatingly move out of the cylindrical channel 16 (i.e., to move the end of the plunger 11 having the cap 23 away from the coil 15).
The plunger reset lever 21 of
The tripping device 10 also includes a number of anti-shock devices structured to eliminate movement of the coil 15 relative to the coil frame 17 and/or a number of anti-shock devices structured to eliminate movement of the plunger 11 relative to the cylindrical channel 16 of the coil 15.
The number of anti-shock devices structured to eliminate movement of the coil 15 relative to the coil frame 17 includes, for example and without limitation, one or both of a clip 18 and a bumper 19.
In the current embodiment, clip 18 includes a base 24 having two sidewalls 25 extending therefrom which generally form a U-shaped structure. Each sidewall 25 includes a protrusion 26 on an inner surface thereof. The clip 18 is structured to couple with the coil frame 17 via a “snap fit”. As a result, the need for screws, adhesives, fasteners, or the like is eliminated. The protrusions 26 are in compressive abutting relationship with the coil 15 when the clip 18 is coupled with coil frame 17, thereby preventing side-to-side motion, for example, during a shock-loading event. Although the protrusions 26 are described in the context of a compressive abutting relationship with the coil 15, it should be noted that other relationships may be used while remaining within the scope of the present invention. For example, a relatively small gap may be present between either or both of the protrusions 26 and the coil 15 while remaining within the scope of the present invention.
The bumper 19, in the current embodiment, is coupled to an outside surface of the coil frame 17, for example, using an adhesive. The bumper 19 is a formed of rubber, although other materials (e.g., without limitation, neoprene) may be used. The bumper 19 is structured to absorb impact and dampen vibrations during a shock-loading event.
The number of anti-shock devices structured to eliminate movement of the plunger 11 relative to the cylindrical channel 16 of the coil 15 includes, for example and without limitation, one or both of a sleeve 12 and a bias spring 20. The sleeve 12 is formed from a non-conductive material (e.g., without limitation, brass; plastic) and is structured to reduce the amount of space present between the outer circumference of the plunger 11 and an inner circumference of the cylindrical channel 16. In
Bias spring 20 is structured to bias the plunger reset lever 21 in a clockwise direction (relative to
The under-voltage release mechanism 30 includes a circuit board 33 which is fixedly coupled to the third portion 31c of the mounting bracket 31. More specifically, a shield 34 is coupled to the left side (with reference to
The plunger reset lever 21 is rotateably coupled to the mounting bracket 31 on pivot 42. More specifically, the hub 21a of plunger reset lever 21 is coupled to pivot 42 using a lever cap 39, lock washer 38, and screw 40. The stop 41 is provided on the mounting bracket 31. When engaged by the plunger reset lever 21, the stop 41 prevents the plunger reset lever 21 from counterclockwise motion (with reference to
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
