The present invention relates generally to circuit breakers for interrupting current from an electrical power supply, and more particularly to tripping shaft assemblies for circuit breakers.
Electronic circuit breakers are used in certain electrical systems for protecting branch electrical circuits that are coupled to an electrical power supply. Some such circuit breakers, such as for low voltage tripping applications (e.g., 100V to 600V), may include a tripping shaft that is mounted in a rigid frame. The tripping shaft includes multiple lever arms that are configured to interface with various tripping components of the circuit breaker, such as a maglatch actuator, interlock, or the like. Assembly of such tripping shafts has been quite complicated and time consuming. Such tripping shafts are typically spring biased so that upon actuation thereof, they may return to a common rotational orientation under a restoring force provided by a return spring. Assembly of the return spring to the tripping shaft can be quite difficult. Accordingly, there is a need for a tripping shaft and tripping assemblies that are easier to assemble and provide adequate spring bias to the tripping shaft.
In a first aspect, a tripping shaft apparatus is provided. The tripping shaft apparatus includes a rigid shaft portion, a first over-molded shaft portion molded onto the rigid shaft portion, the first over-molded shaft portion including at least a first molded lever, a second lever spaced from the first lever, and a torsion spring located between the first molded lever and the second lever.
According to another aspect, a circuit breaker tripping assembly is provided. The circuit breaker tripping assembly includes a frame including first side frame and second side frame, each including a journal, a tripping shaft apparatus including a shaft including a rigid shaft portion including bearing portions configured to mount to the journals of the first side frame and the second side frame, at least a first over-molded shaft portion molded onto the rigid shaft portion, the first over-molded shaft portion including a first molded lever, and a second lever spaced from the first lever, and a torsion spring mounted to the shaft between the first molded lever and the second lever.
According to another aspect, a method of assembly of a circuit breaker tripping assembly is provided. The method includes providing a tripping shaft apparatus including a rigid shaft portion and bearing portions, wherein the bearing portions include larger dimension areas and smaller dimension areas, a first over-molded shaft portion molded onto the rigid shaft portion, the first over-molded shaft portion including at least a first molded lever, a second lever spaced from the first molded lever, and a torsion spring located between the first molded lever and the second lever, providing a frame including first and second side frames including first and second journals with entry slots into the first and second journals, and inserting the smaller dimension areas of the bearing portions of the tripping shaft apparatus through entry slots in the first and second side frames.
Still other aspects, features, and advantages of the present invention may be readily apparent from the following detailed description by illustrating a number of example embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention may also be capable of other and different embodiments, and its details may be modified in various respects, all without departing from the scope of the present invention. The invention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.
The drawings, described below, are for illustrative purposes only and are not necessarily drawn to scale. The drawings are not intended to limit the scope of the invention in any way. Wherever possible, the same or like reference numbers will be used throughout the drawings to refer to the same or like parts.
Because such tripping shafts have relatively large levers positioned along their length, and because installing a spring over the lever is difficult and/or complicated, the location of the spring may be generally relegated to be at the end of the shaft or of complicated design because the spring cannot be received over the levers. Furthermore, because some new versions of the tripping shaft may include levers that are positioned outside of each side frame the tripping assembly, providing spring biasing to the tripping shaft may be further complicated.
In view of the foregoing difficulties, and, in particular, the difficulty in assembly of tripping shafts to circuit breaker frames, and difficulties in providing spring biasing thereof, a novel tripping shaft apparatus for a circuit breaker tripping assembly is provided. The novel tripping shaft apparatus includes an integrated torsion spring. The torsion spring may be provided inboard of one or more levers of the tripping shaft apparatus. Inboard as used herein means that the spring is provided on the shaft between at least two levers of the tripping shaft.
The tripping shaft apparatus according to one or more embodiments includes an over-molded shaft including an integral torsion spring that is provided inboard of at least two levers, i.e., between the two levers. In particular, the tripping shaft includes a rigid shaft portion (e.g., a rigid central portion) that is over-molded with a moldable material (e.g., a polymer) at one or both ends, and the torsion spring is installed on a rigid shaft portion prior to molding. The various levers and possibly other shaft portions may be molded on either side of the torsion spring. Thus, the over-molded tripping shaft apparatus includes an integrated torsion spring provided inboard of the levers. The tripping shaft apparatus 1) enables the torsion spring to be more centrally positioned, and 2) allows the torsion spring to be located so that it is able to engage directly with the a side frame of the circuit breaker frame, and 2) provides for ease of assembly.
The improved tripping shaft apparatus comprises a rigid shaft portion and a first polymer shaft portion over-molded onto the rigid shaft portion, wherein the first polymer shaft portion may include one or more than one molded levers. A second lever may be provided that is spaced from the first molded lever. A second polymer shaft portion may also include one or more than one molded levers. The second lever may be molded as a part of the second polymer shaft portion in some embodiments. Tripping shaft apparatus includes the integral torsion spring received over the shaft between at least two levers, such as between first molded lever and the second lever.
The torsion spring may reside in a sealed mold pocket during the process of over-molding the rigid shaft portion with polymer (e.g., a fiberglass-filled plastic) as will be apparent from the following. Upon completion of the over-molding process, the torsion spring is integrated on the shaft and located on the tripping shaft between levers.
In another aspect, a circuit breaker tripping assembly is provided. Circuit breaker tripping assembly includes a frame including first side frame and second side frame, each including a journal, and a tripping shaft apparatus mounted to the frame at the journals. The tripping shaft apparatus includes a rigid shaft portion including bearing portions configured to mount to the journals of the first side frame and the second side frame, at least a first over-molded portion that is molded onto the rigid shaft portion, the first over-molded portion including at least one molded lever. Another lever may be provided on the tripping shaft apparatus, and may also be molded, and the torsion spring is mounted to the tripping shaft between the levers.
In another broad aspect, a method of assembling a tripping shaft apparatus to a frame of a circuit breaker is provided. The method involves, in one aspect, providing a tripping shaft with a torsion spring included between levers of the tripping shaft, and installing the tripping shaft to the circuit breaker side frames. This may be accomplished without mechanical crimping, secondary mechanism to retain the shaft in the side frames, or any special tooling.
Advantageously, the present invention solves several problems of the prior art, i.e., difficulty of assembly of the tripping shaft to the journals of the side frames of a circuit breaker, and difficulty of including spring biasing to the tripping shaft, especially when the tripping shaft includes levers that are located outboard of the journal locations of the side frames.
These and other embodiments of tripping shaft apparatus, circuit breaker tripping assemblies and methods of assembling a tripping shaft to a frame of a circuit breaker of the present invention are described below with reference to
Referring now in specific detail to
The tripping shaft apparatus 100 includes a rigid shaft portion 102 having a first end 104 and a second end 106 (see
The rigid shaft portion 102 may include first bearing portion 116A and second bearing portion 116B spaced apart from the first bearing portion 116A. The first and second bearing portions 116A, 116B may be configured to register with a frame 350 (
Bearing portions 116A, 116B may each include a cross-sectional shape as is shown in
Again referring to
The tripping shaft apparatus 100 includes a second lever 126 that is spaced from the first molded lever 124 along a length thereof, and a torsion spring 128 located between the first molded lever 124 and the second lever 126.
In some embodiments, the second lever 126 may also be molded, and may be part of a second over-molded shaft portion 130. In other embodiments, the second lever may be cast or machined metal. In the case where a second over-molded shaft portion 130 is used, the second over-molded shaft portion 130 may be molded on the second interface portion 114 on the second end 106 of the rigid shaft portion 102 opposite the first end 104. Both the first over-molded shaft portion 122 and the second over-molded shaft portion 130 may be formed of a moldable material, such as a polymer. More specifically, a polybutylene terephthalate (PBT) polymer may be used. The polymer may be filled with fiberglass fibers at about 25%-30% loading by volume, for example. Other suitable polymers may be used. First over-molded shaft portion 122 and second over-molded shaft portion 130 may be formed in a common mold and during a common molding operation. Optionally, more than one molding operation may be used to mold the first over-molded shaft portion 122 and second over-molded shaft portion 130. In some embodiments, one or more additional levers may be molded. For example, a third lever 132 may be over-molded on the first end 104 or the second end 106.
For example, as shown in
As depicted, a third lever 132 may be molded onto the third interface portion 115 on the first end 104 on an inboard side of the first bearing portion 116A whereas the first molded lever 124 may be molded on an outboard side of the first bearing portion 116A. Additional levers may be molded as part of the first over-molded shaft portion 122 and/or the second over-molded shaft portion 130, or elsewhere. For example, fourth lever 134 and fifth lever 136 may be used to interface with a booster or secondary latch, for example.
In more detail, the torsion spring 128, as best shown in
Torsion spring 128 may include a first spring arm 242 that is configured to register on a lever. For example, first spring arm 242, which may be relatively shorter, may be configured to register on the third lever 132 located between the first molded lever 124 and second lever 126, which may also be molded in some embodiments. The first spring arm 242 may include a length L1, measured from a physical center (e.g., central axis 225) of the wound central portion 238 of the torsion spring 128 to a location of registry with a lever (e.g., third lever 132) of about 11 mm, for example. First spring arm 242 may register in a recess 133 formed in the third lever 132, for example.
Torsion spring 128 may also include a second spring arm 244, that may be relatively longer than the first spring arm 242, and that may be configured to register on the frame 350, such as the first side frame 352 (
As shown in
As further illustrated in
Further, the method 500 includes, in 504, providing a frame (e.g., frame 350) including first and second side frames (e.g., first side frame 352 and second side frame 354) including first and second journals (e.g., journals 455) with entry slots (e.g., entry slots 456) into the first and second journals.
To assemble, the method 500 includes, in 506, inserting the smaller dimension areas (e.g., smaller dimension areas across flats 118) of the bearing portions of the tripping shaft apparatus through entry slots (e.g., entry slots 456) in the first and second side frames (e.g., first side frame 352 and second side frame 354).
The method 500 may further include rotating the tripping shaft apparatus (e.g., tripping shaft apparatus 100) to register the spring arms (e.g., first spring arm 242 and second spring arm 244) of the torsion spring (e.g., torsion spring 128) on the first molded lever (e.g., first molded lever 124) and one of the first and second side frames (e.g., first side frame 352 and second side frame 354) to pre-stress the torsion spring 128.
While the invention is susceptible to various modifications and alternative forms, specific embodiments and methods thereof have been shown by way of example in the drawings and are described in detail herein. It should be understood, however, that it is not intended to limit the invention to the particular apparatus, assemblies, or methods disclosed, but, to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.
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5705968 | Beck | Jan 1998 | A |
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Number | Date | Country |
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2012051098 | Apr 2012 | WO |
Number | Date | Country | |
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20170076898 A1 | Mar 2017 | US |