Patent Description:
It is the object of the present invention to provide an improved circuit breaker.

A circuit breaker with improved trip unit fixation is disclosed. Another circuit breaker and a system also perform the functions of the circuit breaker. A circuit breaker includes a frame and a trip unit mounted in the frame. The trip unit includes a terminal for securing a wire to the trip unit. One of a wall of the frame and the trip unit include a protrusion and the wall of the frame or the trip unit without the protrusion includes an opening. The protrusion conforms to the opening and the protrusion and opening are positioned to oppose movement of the trip unit in a direction of a force resulting from securing the wire in the terminal.

Another circuit breaker with improved fixation of a trip unit includes a frame with a plurality of trip unit slots and a trip unit mounted in each trip unit slot. Each trip unit includes a terminal for securing a wire to the trip unit A wall of a trip unit slot of the plurality of trip unit slots or the trip unit mounted in the trip unit slot includes a protrusion and the wall of the trip unit slot or the trip unit mounted in the trip unit slot without the protrusion includes an opening. The protrusion conforms to the opening and the protrusion and opening are positioned to oppose movement of the trip unit mounted in the trip unit slot in a direction of a force resulting from securing the wire in the terminal.

A system for improved trip unit fixation in a circuit breaker includes an electrical device and a circuit breaker coupled to the electrical device. Power transmitted through the circuit breaker feeds the electrical device. The circuit breaker includes a frame and a trip unit mounted in the frame. The trip unit includes a terminal for securing a wire to the trip unit. A wall of the frame or the trip unit includes a protrusion and the wall of the frame or the trip unit without the protrusion includes an opening. The protrusion conforms to the opening and the protrusion and opening are positioned to oppose movement of the trip unit in a direction of a force resulting from securing the wire in the terminal.

In order that the advantages of the embodiments of the invention will be readily understood, a more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only some embodiments and are not therefore to be considered to be limiting of scope, which is only defined by the claims, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:.

The terms "including," "comprising," "having," and variations thereof mean "including but not limited to" unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The term "and/or" indicates embodiments of one or more of the listed elements, with "A and/or B" indicating embodiments of element A alone, element B alone, or elements A and B taken together.

In some embodiments, the protrusion and the opening are located on a side of the trip unit where the wire is inserted. In other embodiments, the terminal includes a threaded shaft that is rotated to apply a force to the wire to secure the wire to the trip unit and rotating the threaded shaft produces the force that secures the wire to the trip unit in a direction perpendicular to the threaded shaft. In a further embodiment, the threaded shaft includes a head accessible from a top side of the trip unit and the wire is secured to the trip unit on a side of the trip unit and the protrusion or opening is on a bottom portion of the side of the trip unit distal to the head of the threaded shaft. In other embodiments, the frame includes a plurality of trip unit slots and each trip unit slot includes a trip unit. A wall of a trip unit slot of the plurality of trip unit slots or the trip unit in the trip unit slot includes the protrusion and the wall of the trip unit slot or the trip unit in the trip unit slot without the protrusion includes the opening.

In some embodiments, opposing movement of the trip unit in the direction of the force resulting from securing the wire in the terminal further opposes movement of a first component of the trip unit shaped to contact a second component of the frame and/or another trip unit. In other embodiments, the frame includes a trip unit slot where the trip unit is mounted and opposing movement of the trip unit in the direction of a rotational force resulting from securing the wire in the terminal further opposes deformation of a wall of the trip unit slot that allows trip unit movement due to the force. The wall of the trip unit slot affected by deformation is adjacent to the wall of the trip unit slot with the protrusion or opening.

In some embodiments, the wall of the frame includes the opening and the trip unit includes the protrusion. In other embodiments, the protrusion extends through the wall of the frame. In other embodiments, the opening in the wall of the frame includes a notch extending from a top edge of a trip unit slot where the trip unit is mounted in a direction away from the terminal of the trip unit and wherein the protrusion is shaped to fill the notch. In other embodiments, the opening in the wall of the frame includes an opening below a top edge of a trip unit slot where the trip unit is mounted and the protrusion of the trip unit is shaped to fill the opening. In other embodiments, the wall of the frame includes the protrusion and the trip unit includes the opening and the protrusion extends toward the trip unit and the opening in the trip unit is shaped to conform to the protrusion extending from the wall of the frame.

Another circuit breaker with improved fixation of a trip unit includes a frame with a plurality of trip unit slots and a trip unit mounted in each trip unit slot. Each trip unit includes a terminal for securing a wire to the trip unit. A wall of a trip unit slot of the plurality of trip unit slots or the trip unit mounted in the trip unit slot includes a protrusion and the wall of the trip unit slot or the trip unit mounted in the trip unit slot without the protrusion includes an opening. The protrusion conforms to the opening and the protrusion and opening are positioned to oppose movement of the trip unit mounted in the trip unit slot in a direction of a force resulting from securing the wire in the terminal.

In some embodiments, the protrusion and the opening are located on a side of the trip unit where the wire is inserted. In some embodiments, the terminal includes a threaded shaft that is rotated to apply a force to the wire to secure the wire to the trip unit and rotating the threaded shaft produces the force that secures the wire to the trip unit. In some embodiments, the threaded shaft includes a head accessible from a top side of the trip unit and the wire is secured to the trip unit on a side of the trip unit and the protrusion or opening is on a bottom portion of the side of the trip unit distal to the head of the threaded shaft.

In some embodiments, opposing movement of the trip unit in the trip unit slot in the direction of the force resulting from securing the wire in the terminal further opposes movement of a first component of the trip unit in the trip unit slot shaped to contact a second component of the trip unit slot. In some embodiments, opposing movement of the trip unit mounted in the slot in the direction of the force resulting from securing the wire in the terminal further opposes deformation of a wall of the trip unit slot that allows trip unit movement due to a rotational force, where the wall of the trip unit slot affected by deformation is adjacent to the wall of the trip unit slot with the protrusion or opening. In some embodiments, the wall of the trip unit slot includes the opening and the trip unit mounted in the slot comprises the protrusion.

<FIG> is a perspective view illustrating one embodiment of a circuit breaker <NUM> with improved trip unit fixation. <FIG> is a front view and <FIG> is a top view further illustrating the circuit breaker with improved trip unit fixation of <FIG>. The circuit breaker <NUM> with the improved trip unit fixation includes a first trip unit 102a, a second trip unit 102b and a third trip unit 102c (collectively or generically "trip unit <NUM>") with a first protrusion 104a, a second protrusion 104b, and a third protrusion 104c respectively (collectively or generically "protrusion <NUM>"), a bolt <NUM> for each trip unit <NUM>, a frame <NUM>, a top cover <NUM> with a side walls <NUM> on the sides of and in between trip units <NUM>, and openings <NUM> for the bolts <NUM>, and an actuator <NUM>, which are explained below.

Circuit breakers provide overcurrent protection for wiring and other equipment. For example, a particular wire size and type may be rated for <NUM> amperes ("A") so a 50A circuit breaker may be used to protect the wire from the circuit breaker to equipment connected to the wire. In some cases, a circuit breaker also protects equipment connected to the wire, such as a motor, an appliance, etc. Larger circuit breakers are often stand-alone circuit breakers mounted in or near equipment. For example, a circuit breaker may be mounted in a motor controller, motor starter, equipment enclosure, etc. Often, stand-alone circuit breakers are multi-pole and have either two poles for line-to-line single phase power or three poles for three-phase power.

Stand-alone circuit breakers are typically connected to incoming and outgoing wires via a terminal. Other circuit breakers may mount to a panel and have an input connected to bus bars while output terminals are connected to wires and protect the wiring and equipment connected to the output terminals. In some embodiments, a circuit breaker <NUM> feeds and/or is part of an electrical component. For example, the electrical component may be a motor starter, a variable frequency drive, a contactor, etc. In some embodiments, the circuit breaker <NUM> is housed within the electrical component. In other embodiments, the circuit breaker <NUM> is sold together with the electrical component.

Typically, standalone circuit breakers, such as the circuit breaker <NUM> of <FIG>, <FIG> and <FIG> have a frame <NUM> that houses the trip units <NUM>. In some embodiments, the frame <NUM> is called a housing. A top cover <NUM> is placed over the trip units and may extend to the frame <NUM>. An actuator <NUM> is used to mechanically open and close contacts of the circuit breaker <NUM>. The actuator <NUM> may be a dial, as depicted in <FIG>, may be a lever that moves back and forth, or the like.

Circuit breakers <NUM> typically have an inverse-time characteristic used to determine when the circuit breaker will trip on overcurrent. Current flowing in the circuit breaker <NUM> at or less than the circuit breaker rating does not cause the circuit breaker <NUM> to trip (with certain exceptions, such as a ground-fault interrupt ("GFI") circuit breaker). An overcurrent of <NUM> percent typically causes a circuit breaker <NUM> to open within minutes. An overcurrent of <NUM> percent typically causes a circuit breaker <NUM> to open within seconds, and overcurrent of <NUM> percent typically causes a circuit breaker <NUM> to open within milliseconds. Some circuit breakers <NUM> also include adjustments to the inverse-time characteristic for circuit breaker coordination. Some circuit breakers <NUM> include an inverse-time characteristic shaped to allow for motor inrush current, which may be in the range of <NUM> percent to <NUM> percent of the rating of the circuit breaker <NUM>, or possibly higher, so the inverse-time characteristic is adjusted to not trip during motor inrush current. Where the circuit breaker <NUM> includes a motor as a load, the circuit breaker <NUM> is typically rated to handle motor inrush current.

Often, a circuit breaker <NUM> will include a bimetal strip used for overcurrent protection that contributes to the inverse-time characteristic. Often circuit breakers <NUM> may also include a short-circuit trip section that trips the circuit breaker <NUM> as quickly as possible for overcurrent above a particular value. The overcurrent section with the bimetal strip and short circuit section of the circuit breaker <NUM> are sensitive to placement and mechanical forces. Typically, a circuit breaker <NUM> is designed to withstand a particular maximum short circuit current limit. High current through a circuit breaker <NUM> causes mechanical forces, torque, etc. that are capable of causing a circuit breaker <NUM> to explode or be damaged prior to opening if short circuit current is higher than the short circuit current limit of the circuit breaker <NUM>.

While circuit breakers <NUM> are designed for a particular maximum short circuit current, other mechanical forces may cause problems with the bimetal strip, contacts and/or the short circuit current sections of the circuit breaker <NUM>. If mechanical forces cause movement of the bimetal strip, circuit breaker contacts, etc. accuracy of the circuit breaker <NUM> may be affected.

Often, circuit breakers <NUM> include one or more trip units <NUM>, a frame <NUM> where the trip units are placed, a top cover <NUM>, and an actuator <NUM>. In some embodiments, the frame <NUM> is of a particular size. Certain frame sizes accommodate trip units <NUM> of particular ampere ratings. For example, a D-frame circuit breaker <NUM> may have current ratings from <NUM> A to <NUM> A in discrete increments. Frame sizes may also indicate particular features for a manufacturer.

<FIG> depict a circuit breaker <NUM> that includes overcurrent trip units <NUM> on one side and short circuit trip units <NUM> on the other side of the frame <NUM>. The trip units <NUM> interact so that a trip unit <NUM> on one side interacts with a trip unit <NUM> on the back side of the trip unit <NUM>. Each of the trip units <NUM> include a terminal where wires can be secured to the trip unit <NUM> with a bolt <NUM>.

An issue that affects typical circuit breaker accuracy and performance is that when a wire is secured to a trip unit <NUM>, torque and various mechanical forces cause the trip unit <NUM> to move within the frame <NUM>, which causes the bimetal strip and/or components of the short circuit trip unit, contacts, etc. to move enough to affect accuracy of the circuit breaker <NUM>. Often, securing wire into the terminal of a trip unit causes the trip unit <NUM> to move laterally, which may cause deflection of the side walls <NUM> adjacent to each circuit breaker <NUM>. In some embodiments, the side walls <NUM> are part of the top cover <NUM> and in other embodiments, the side walls <NUM> are part of the frame <NUM>. For example, as the bolt <NUM> is screwed into the trip unit <NUM>, rotational forces may cause the trip unit <NUM> to move, which may deflect the side walls <NUM>. Often, the trip units <NUM> do not return to an initial location after the wire has been secured to the trip units <NUM>.

The circuit breaker <NUM> depicted in <FIG> include a frame <NUM> and a trip unit <NUM> mounted in the frame <NUM>. The trip unit <NUM> includes a terminal for securing a wire to the trip unit <NUM>. A protrusion <NUM> in the trip unit <NUM> or wall of the frame <NUM> and the trip unit <NUM> or wall of the frame <NUM> without the protrusion <NUM> includes an opening that conforms to the protrusion <NUM> where the protrusion <NUM> and opening are positioned to oppose movement of the trip unit <NUM> in a direction of a force resulting from securing the wire in the terminal.

In some embodiments, opposing movement of the trip unit <NUM> in the direction of the force resulting from securing the wire in the terminal also opposes movement of a first component of the trip unit <NUM> shaped to contact a second component of the frame <NUM> or another trip unit <NUM>. The first component and the second component may be electrical, mechanical or both. For example, the first component may be a bimetal strip, a contact, etc. and the second component in the frame <NUM> may include another contact or other conductive part that is intended to make contact and conduct electricity with the trip unit <NUM>.

In one embodiment, the protrusion <NUM> and the opening are located on a wall <NUM> of the trip unit where the wire is inserted. In this embodiment, the location of the protrusion <NUM> is close to where movement is anticipated due to securing the wire in the terminal of the trip unit <NUM>. In addition, movement of the trip unit <NUM> caused by securing the wire in the terminal of the trip unit <NUM> is typically in the direction of the X-axis with regard to the position axis depicted in <FIG> and <FIG> and the wall <NUM> of the frame <NUM> and trip unit <NUM> where the wire is inserted into the terminal of the trip unit <NUM> runs in the X and Z axes so placement of the protrusion <NUM> into an opening this wall <NUM> beneficially minimizes movement of the trip unit <NUM> in the X-axis direction.

In some embodiments, the terminal of the trip unit <NUM> includes a threaded shaft, usually in the form of a bolt <NUM>, that is rotated to apply a force to the wire to secure the wire to the trip unit <NUM> and rotating the threaded shaft produces the force that secures the wire to the trip unit <NUM> in a direction perpendicular to the threaded shaft (e.g. in a direction of the X-axis or in the X-Y plane). The trip unit <NUM> extends into the circuit breaker <NUM> in a direction of the Z-axis within a slot in the frame <NUM> so the portion of the trip unit <NUM> in the Y-axis direction and behind the terminal of the trip unit <NUM> minimizes rotation in the X-Y plane, but using the bolt <NUM> to secure the wire to the terminal causes movement of the trip unit <NUM> particularly near the terminal, which in turn does cause some movement elsewhere in the trip unit <NUM>. The protrusion <NUM> and corresponding opening of the trip unit <NUM>/frame <NUM> opposes the movement caused by the rotation of the threaded shaft of the bolt <NUM>.

In some embodiments, the threaded shaft of the bolt <NUM> includes a head <NUM> accessible from an opening <NUM> of the top cover <NUM> and a top side of the trip unit <NUM>. While the head <NUM> is depicted with slots for a Pozidriv® screwdriver, a Philips screwdriver, other openings in the head <NUM> may be used, such as a slot for a flat-blade screwdriver, a Torx® head, an hex key, a combination slot for a flat-blade screwdriver or Pozidriv/Philips screwdriver, etc. In the embodiment, the wire is secured to the trip unit <NUM> on a side of the trip unit <NUM> and the protrusion <NUM> or opening is on a bottom portion of the side of the trip unit <NUM> distal to the head <NUM> of the threaded shaft of the bolt <NUM>.

In the circuit breaker <NUM> of <FIG>, <FIG> and <FIG>, the protrusion <NUM> of a trip unit <NUM> (e.g. protrusion 104a and trip unit 102a) is depicted as centered in the X-axis direction with respect to the trip unit <NUM>. In other embodiments, the protrusion <NUM> is off-center with respect to the trip unit <NUM> and may be left-of-center or right-of-center within a width of the trip unit <NUM>. In some embodiments, two or more protrusions 104a, 104b, 104c are spaced differently across a width of the respective trip units 102a, 102b, 102c.

<FIG> is a perspective view illustrating a frame <NUM> of an embodiment <NUM> of a circuit breaker <NUM> with improved trip unit fixation. The frame <NUM> includes a plurality of trip unit slots <NUM> and each trip unit slot <NUM> is sized for at least one trip unit <NUM>. The trip unit slots <NUM>, in the embodiment <NUM>, include divider walls <NUM> separating the trip unit slots <NUM>. In the depicted embodiment <NUM>, each trip unit slot <NUM> includes space for two trip units <NUM>, each having a terminal against a wall <NUM> on opposite ends of the frame <NUM> and at opposite ends of a trip unit slot <NUM>. In other embodiments, each trip unit slot <NUM> is sized for one trip unit <NUM> where the trip unit <NUM> has short circuit and inverse-time functions in the single trip unit <NUM>. A wall <NUM> of a trip unit slot <NUM> of the plurality of trip unit slots <NUM> or the trip unit <NUM> in the trip unit slot <NUM> includes the protrusion <NUM> and the wall <NUM> of the trip unit slot <NUM> or the trip unit <NUM> in the trip unit slot <NUM> without the protrusion <NUM> has the opening. In the depicted embodiment <NUM>, the frame <NUM> includes the openings <NUM> and the trip units <NUM> include the protrusions <NUM>.

Typically, the trip unit slots <NUM> are sized to match dimensions of the trip units <NUM>. For example, a width of a trip unit slot <NUM> may match a width of a trip unit to minimize lateral movement of the trip unit <NUM>. In other embodiments, the trip unit slots <NUM> and trip units <NUM> include various tabs, openings, latches, etc. so that when a trip unit <NUM> is placed in a trip unit slot <NUM>, the trip unit <NUM> will be secure within the trip unit slot <NUM>. In addition, the protrusion <NUM> matches the opening <NUM> so that placement of the trip unit <NUM> in the trip unit slot <NUM> places the protrusion <NUM> in the opening <NUM>. In some embodiments, the frame <NUM> and/or trip unit <NUM> include slots, gaps, protrusions, latches, ledges, etc. designed to hold the trip unit <NUM> into the frame <NUM>. Also, when the trip unit <NUM> is placed in the trip unit slot <NUM>, in some embodiments, the trip unit <NUM> is secured to the trip unit slot <NUM>. In other embodiments, placement of the top cover <NUM> over the trip unit <NUM> secures the trip unit <NUM> to the frame <NUM> and top cover <NUM>. One of skill in the art will recognize other ways to secure a trip unit <NUM> in a trip unit slot <NUM> where the protrusion <NUM> is also secured in the opening <NUM>.

In some embodiments where the protrusion <NUM> is on the trip unit <NUM>, the protrusion <NUM> extends through the wall <NUM> of the frame <NUM>. The protrusion <NUM>, in some cases, may extend an amount past the wall <NUM> of the frame <NUM>. In other embodiments, the protrusion <NUM> extends through the wall <NUM> of the frame <NUM> an amount so an end of the protrusion <NUM> is flush with a face of the wall <NUM>. In other embodiments, the protrusion <NUM> does not penetrate all the way through the wall <NUM>, but extends deep enough into the wall <NUM> to prevent lateral movement of the trip unit <NUM>. Other configurations of a protrusion <NUM> and an opening <NUM> are discussed in more detail below.

<FIG> is a perspective view illustrating one embodiment of a trip unit <NUM> of a circuit breaker <NUM> with improved trip unit fixation. <FIG> is a front view further illustrating the embodiment of the trip unit <NUM> of <FIG> is a side view further illustrating the embodiment of the trip unit <NUM> of <FIG> is a front section view A-A' further illustrating the embodiment of the trip unit <NUM> of <FIG>. For example, the embodiment of <FIG> may depict a trip unit <NUM> with a bimetal strip <NUM>. In the embodiment, the trip unit <NUM> includes at least a trip unit body <NUM> with a nut <NUM> where the bolt <NUM> is threaded, an angled clamp <NUM>, a conductive element <NUM> and the bimetal strip <NUM>. In other embodiments, the conductive element <NUM> is threaded so that the bolt <NUM> is screwed into the conductive element <NUM> and the embodiment does not include a nut <NUM>. Note that the embodiment depicted in <FIG> is one particular design and other designs of trip units <NUM> with a bimetal strip and with or without short circuit current elements that include a protrusion <NUM> and/or opening <NUM> are contemplated herein. Typically, the body <NUM> of the trip unit <NUM> is shaped to fit in a trip unit slot <NUM> of the frame <NUM> and is shaped to accommodate the nut <NUM>, the bolt <NUM>, the conductive element <NUM>, bimetal strip <NUM> and other parts.

<FIG> is a perspective view illustrating one embodiment of another trip unit <NUM> of a circuit breaker <NUM> with improved trip unit fixation. <FIG> is a front view further illustrating the embodiment of the trip unit <NUM> of <FIG> is a side view further illustrating the embodiment of the trip unit <NUM> of <FIG>. For example, the embodiment of <FIG> may depict a trip unit <NUM> with a body <NUM> of the trip unit <NUM>, a short circuit trip lever <NUM> for mechanical linkage, and a short circuit element <NUM>. The short circuit element <NUM> is not depicted in <FIG> for simplicity, but is included in some trip units <NUM>. Note that the embodiment depicted in Figures 4A-4D is another particular design of a trip unit <NUM> and other designs of trip units <NUM> with a short circuit element and/or contact and with or without a bimetal strip that include a protrusion <NUM> and/or opening <NUM> are contemplated herein.

In some embodiments, the trip units <NUM> include a nut <NUM> or conductive element <NUM> with a threaded opening that matches threads on a threaded shaft of the bolt <NUM> so that turning the bolt <NUM> moves the head <NUM> of the bolt <NUM> and the angled clamp <NUM> toward the conductive element <NUM> of the trip unit <NUM>. In other embodiments, the nut <NUM> is not included and the body <NUM>/<NUM> or conductive element <NUM> of the trip unit(s) <NUM> include an opening and threads for the bolt <NUM> to tighten into the body <NUM>/<NUM> or conductive element <NUM>. When an end of a wire is placed under the angled clamp <NUM> and the bolt <NUM> is rotated to tighten the angled clamp <NUM> against the wire, uneven torque produced by the wire being on one side of the bolt <NUM> increases a tendency of the trip unit <NUM> to move. In addition, rotational forces of tightening the bolt <NUM> once the angled clamp <NUM> presses the wire against the conductive element <NUM> also increase a tendency of the trip unit <NUM> to move. The protrusion <NUM> secured in the opening <NUM> opposes the forces cause by tightening the bolt <NUM> and uneven forces of the wire being on one side of the bolt <NUM>.

In embodiments where the protrusion <NUM> is on the trip unit <NUM> and the opening <NUM> is in the frame <NUM>, the protrusion <NUM> and opening <NUM> may be of various shapes that will resist movement of the trip unit <NUM> when wire is tightened into the terminal of the trip unit <NUM>. <FIG> is a partial front view illustrating one embodiment of a rectangular protrusion <NUM> of a trip unit <NUM> and a corresponding opening <NUM> in a frame <NUM>. <FIG> is a partial top cross section view further illustrating the rectangular protrusion <NUM> of <FIG> depicting an embodiment with perpendicular sides of the protrusion <NUM>. <FIG> is a partial top cross section view further illustrating the rectangular protrusion <NUM> of <FIG> depicting an embodiment with angled sides of the protrusion <NUM>. In the embodiment depicted in <FIG>, the protrusion <NUM> has a width in the X-axis direction less than a length in the Z-axis direction. In some embodiments, the protrusion <NUM> extends through the opening <NUM>. In other embodiments, the protrusion <NUM> extends into an opening <NUM> partially through the wall <NUM> of the frame <NUM>.

In various embodiments, the protrusion <NUM> has various shapes in the Y-axis direction. In some embodiments, sides of the protrusion <NUM> in the Y-axis direction are perpendicular to a face of the wall <NUM> of the frame <NUM>, as depicted in <FIG>. In other embodiments, the protrusion <NUM> is shaped differently, such as angling in a way to flair out so and end of the protrusion <NUM> distal to the trip unit <NUM> is wider than an end of the protrusion <NUM> adjacent to the trip unit <NUM>, as depicted in <FIG>.

<FIG> is a partial front view illustrating another embodiment of a rectangular protrusion <NUM> of a trip unit <NUM> and a corresponding opening <NUM> in the frame <NUM>. <FIG> is a partial front view illustrating another embodiment of a rounded rectangular protrusion <NUM> of a trip unit <NUM> and a corresponding opening <NUM> in the frame <NUM>. <FIG> is a partial front view illustrating another embodiment of a rectangular protrusion <NUM> of a trip unit <NUM>, where the protrusion <NUM> includes a narrow section and a wide section, and a corresponding opening <NUM> in the frame <NUM>. In the embodiment, the protrusion <NUM> may be shaped like an extension from a puzzle piece any may serve to lock the trip unit <NUM> into the frame <NUM> to resist movement of the trip unit <NUM> in multiple directions.

<FIG> is a partial front view illustrating another embodiment of a circular protrusion <NUM> of a trip unit <NUM> and a corresponding opening <NUM> in the frame <NUM> and <FIG> is a partial side cross section view further illustrating the circular protrusion <NUM> of <FIG>. The circular protrusion <NUM> has some advantages in that movement of the trip unit <NUM> is opposed in various directions in the X-Z plane by the circular protrusion <NUM>.

<FIG> is a partial front view illustrating another embodiment of a rectangular protrusion <NUM> of the frame <NUM> and a corresponding opening <NUM> in the trip unit <NUM>. <FIG> is a partial side cross section view further illustrating the rectangular protrusion <NUM> of <FIG>. In the embodiment, the wall <NUM> of the frame <NUM> that is on the side of the trip unit <NUM> where wire is inserted includes a protrusion <NUM> that extends in the Y-axis direction toward the trip unit <NUM>. The trip unit <NUM> includes a corresponding opening <NUM> that conforms to the protrusion <NUM> extending from the frame <NUM>. Having a protrusion <NUM> extending from the frame <NUM> toward the trip unit <NUM> is advantageous to not have the protrusion <NUM> seen from or exposed to the exterior of the circuit breaker <NUM>, which may provide some protection of the protrusion <NUM>.

<FIG> is a partial front view illustrating another embodiment of a rounded rectangular protrusion <NUM> of the frame <NUM> and a corresponding opening <NUM> in the trip unit <NUM>. <FIG> is a partial side cross section view further illustrating the rounded rectangular protrusion <NUM> of <FIG>. Having a rectangular protrusion <NUM> with a rounded end may be advantageous to help guide the trip unit <NUM> during installation. While the rounded protrusion <NUM> is also rounded in the X-axis direction, other embodiments include a rectangular or square cross section in the X-Y plane above a rounded bottom section.

<FIG> is a partial front view illustrating another embodiment of a wide rectangular protrusion <NUM> of the frame <NUM> and a corresponding opening <NUM> in a trip unit <NUM>. <FIG> is a partial side cross section view further illustrating the wide rectangular protrusion <NUM> of <FIG>. The wide rectangular protrusion <NUM> is similar to the embodiment of <FIG>, but wider, which may be useful in strengthening the protrusion against lateral movement in the X-axis direction. While several embodiments of protrusions <NUM> and corresponding openings <NUM> are depicted, other embodiments are anticipated herein and one of skill in the art will recognize other designs for a protrusion <NUM> and corresponding opening <NUM> in frames <NUM> and trip units <NUM> that oppose forces caused by securing a wire into the terminal of the trip unit <NUM> of a circuit breaker <NUM>.

Claim 1:
A circuit breaker (<NUM>) comprising:
a frame (<NUM>); and
a trip unit (<NUM>) mounted in the frame, the trip unit comprising a terminal for securing a wire to the trip unit, wherein securing the wire in the terminal of the trip unit exerts a force suitable to cause the trip unit to move laterally and to deflect two adjacent side walls (<NUM>), wherein the side walls pertain either to the frame or to a top cover (<NUM>) mounted on top of the frame;
characterised in that one of a wall (<NUM>) of the frame perpendicular to the two adjacent side walls and a side of the trip unit facing the wall comprises a protrusion (<NUM>) and the wall of the frame or the side of the trip unit without the protrusion comprises an opening (<NUM>), wherein the protrusion conforms to the opening, thereby preventing lateral movement of the trip unit according to the force caused by securing the wire in the terminal.