FIELD OF THE INVENTION

[0001] This invention is directed generally to circuit breakers, and, more particularly, to a lug assembly having angled wired-binding holes and an hourglass- shaped fastener.

BACKGROUND OF THE INVENTION

[0002] Circuit breakers are well known and commonly used to protect automatic circuit interruption to a monitored circuit when undesired conditions occur. For example, a circuit breaker is designed to interrupt current flowing in the monitored circuit when it detects one or more of an overload condition, a ground fault condition, or a short-circuit condition.

[0003] Typically, a circuit breaker is electrically and physically connected to a power cable via a lug (or wire connector), which includes a wire-binding screw fastened to the power cable. The power cable is received in a cable hole, while the wire-binding screw is received in a wire-binding hole, the two holes being generally perpendicular and aligned with each other. In confined spaces, the lug may include multiple cable holes, each one having a corresponding wire-binding hole (and wire-binding screw). Space, whether equipment space, or dielectric clearance space, is always at a premium for enclosed electrical distribution equipment.

SUMMARY OF THE INVENTION

[0004] In an implementation of the present invention, a compact three-hole lug is mounted to a circuit breaker for attachment of power cables in a small space. The lug includes three primary holes for receiving, respectively, the power cables. The three primary holes include two upper holes and a bottom hole. The two upper holes are located on a front surface, near a top surface, of the lug. The bottom hole is located on the front surface between and below the two upper holes, near a bottom surface of the lug.

[0005] The lug further includes three secondary holes for receiving respective fasteners, which clamp in position the power cables. The secondary holes are located on the top surface and include a first secondary hole, a second secondary hole, and a third secondary hole. The first secondary hole is aligned with, and extends through the lug to, a first upper hole. The second secondary hole is aligned with, and extends through the lug to, the bottom hole. The third secondary hole is aligned with, and extends through the lug to, a second upper hole.

[0006] The first secondary hole and the third secondary hole are symmetrically positioned relative to the second secondary hole. The first secondary hole is angled such that its longitudinal axis is angled toward a longitudinal axis of the second secondary hole. Similarly, the third secondary hole is angled such that its longitudinal axis is angled toward the longitudinal axis of the second secondary hole (and the longitudinal axis of the first secondary hole). The angled orientation of the longitudinal axes helps reduce the size of the lug by allowing the placement of the two upper holes closer to a central location of the front surface, as opposed to closer to an outside edge of the front surface.

[0007] Each of the two upper primary holes receives a fastener, e.g., a wire- binding screw, extending through the secondary holes for clamping a respective power cable in position relative to the lug. The bottom hole receives an hourglass-shaped screw for clamping the respective power cable in position relative to the lug. The hourglass- shaped screw is generally longer than the wire-binding screws received in the two upper holes and has a middle section of reduced material, which allows the power cables received in the two upper holes to clear without interference.

[0008] In another implementation of the present invention, a circuit breaker assembly includes a circuit breaker and a mechanical lug assembly for attachment of power cables. The mechanical lug assembly is mounted to the circuit breaker and includes a main structural body having a cable-receiving face and a wire-binding face. The cable-receiving face is generally defined by a height and a width of the body, the wire-binding face being generally perpendicular to the cable-receiving face and defined by the width and a thickness of the body (noting that the wire-binding face may have angled facets/planes). A plurality of cable holes extend through the cable-receiving face, the cable holes including a first cable hole separated by a second cable hole from a third cable hole. Each of the cable holes is configured to receive a respective one of the power cables. A plurality of wire-binding holes extend at least in part through the wire-binding face, the wire-binding holes including a first wire-binding hole separated by a second wire-binding hole from a third wire-binding hole. The first wire -binding hole has a first longitudinal axis at an angle that intersects a third longitudinal axis of the third wire- binding hole. An hourglass-shaped fastener is received through the second wire-binding hole, the hourglass-shaped fastener having an hourglass section with a contour that generally matches at least in part a corresponding contour of the first cable hole and the third cable hole.

[0009] In another alternative implementation of the present invention, a circuit breaker assembly includes a mechanical lug assembly mounted to a circuit breaker. The mechanical lug assembly includes a body having a first side generally perpendicular to a second side, the first side having a greater surface area than the second side. The mechanical lug assembly further includes a first set of holes extending through the first side, the first set of holes including a pair of symmetrical holes, and a second set of holes extending through the second side, the second set of holes including a first hole, a second hole, and a third hole. The second hole is located between the first hole and the third hole, the first hole having a first longitudinal axis, the second hole having a second longitudinal axis, and the third hole having a third longitudinal axis. The first longitudinal axis is inclined at a first angle relative to the second longitudinal axis, the third longitudinal axis being inclined at a second angle relative to the second longitudinal axis. The first longitudinal axis intersects the third longitudinal axis at a point away from the first hole and the third hole. An hourglass-shaped fastener is received through the second hole, the hourglass-shaped fastener having an hourglass section of reduced material that is positioned near the pair of symmetrical holes.

[0010] Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

[0012] FIG. 1 is a perspective view illustrating a circuit breaker assembly. [0013] FIG. 2 is an exploded view illustrating a mechanical lug assembly.

[0014] FIG. 3 is a cross-sectional view illustrating the mechanical lug assembly.

[0015] FIG. 4 is a side view of a wide mechanical lug assembly.

[0016] FIG. 5 is a side view of a narrow mechanical lug assembly.

[0017] FIG. 6 is a side view of a tall mechanical lug assembly.

[0018] FIG. 7 is a side view of a short mechanical lug assembly.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0019] Referring to FIG. 1, a circuit breaker assembly 100 includes a circuit breaker housing 102 for enclosing internal components of the circuit breaker assembly 100. The circuit breaker assembly 100 includes a plurality of mechanical lug assemblies 104, which are adapted for receiving power cables 106. Alternatively, the power cables 106 can be any wires, terminals, conductors, etc.

[0020] Each mechanical lug assembly 104 is securely mounted in a respective receiving enclosure 108 of the circuit breaker housing 102. Each of the enclosures 108 has a top aperture 110 for facilitating adjustment of fasteners used to clamp the power cables 106 securely in position. For example, a screwdriver or an alien wrench can be inserted through the top apertures 110 to tighten a loose fastener of the mechanical lug assemblies 104 that clamps a respective one of the power cables 106.

[0021] Referring to FIG. 2, the mechanical lug assembly 104 includes a main structural body 120 and a plurality of fasteners 122-124. The main structural body 120 has a cable-receiving face 126 defined generally by a height H and a width W of the main structural body 120. The main structural body 120 further has a wire-binding face 128 defined generally by the width W and a thickness T of the main structural body 120. The wire-binding face 128 is generally perpendicular to the cable-receiving face 126.

[0022] On the cable-receiving face 126, the main structural body 120 has three cable holes 130a- 130c that extend completely through the thickness T. The three cable holes 130a- 130c include a first cable hole 130a that is separated by a second cable hole 130b from a third cable hole 130c. Each of the cable holes 130a-130c is configured to receive a respective power cable 106 (shown in FIG. 1). According to the illustrated embodiment, the cable holes 130a- 130c have generally the same diameter. [0023] On the wire-binding face 128, the main structural body 120 has three wire- binding holes 132a- 132c that extend in part through the height H (as shown and described in more detail in reference to FIG. 3) of the main structural body 120. The wire-binding holes 132a- 132c include a first wire-binding hole 132a that is separated by a second wire- binding hole 132b from a third wire-binding hole 132c. According to the illustrated embodiment, the wire-binding holes 132a- 132c have generally the same diameter.

[0024] The wire-binding face 128 has three sections 128a- 128c, each of the sections corresponding to one of the wire-binding holes 132a- 132c. The three sections include a first section 128a that is generally angled relative to a generally horizontal plane, a second section 128b that is generally parallel to the horizontal plane, and a third section 128c that is generally angled relative to the horizontal plane. In the example of FIG. 2, the first section 128a and the third section 128c are symmetrically angled relative to the second section 128b.

[0025] One of the fasteners 122-124 is an hourglass-shaped fastener 123 that has an hourglass section 123a having an upper section 123b and a lower section 123c. The hourglass-shaped fastener 123 further has a top threaded section 123d and a bottom threaded section 123e. Optionally, only one of the sections 123d, 123e is threaded (e.g., only the top section 123d). A tool-receiving hole 123f is located internally in the top threaded section 123 d and extends longitudinally from a top surface 123g.

[0026] The other two fasteners include a first set screw 122 and a second set screw 124, each with a respective tool-receiving hole 122a, 124a extending longitudinally from a corresponding top surface 122b, 124b. In this example, the set screws 122, 124 are generally identical to each other and have a length LI , L2 that is shorter than a length L3 of the hourglass-shaped fastener 123. In other examples, the set screws 122, 124 can be other types of fasteners, including bolts and other types of wire-binding screws.

[0027] Referring to FIG. 3, the mechanical lug assembly 104 is illustrated with the first set screw 122 and the hourglass-shaped fastener 123 mounted in their respective wire-binding holes 132a, 132b. The first set screw 122 is threadedly engaged within the first wire-binding hole 132a via a set of internal threads 134 of the first wire-binding hole 128. The first set screw 122 protrudes a sufficient distance D within the first cable hole 130a to secure in place, when received, a power cable 106. [0028] The first wire-binding hole 132a extends partially through the height H of the main structural body 120, from the first section 128a of the wire-binding face 128 to the first cable hole 130a. The second wire-binding hole 132b extends partially through the height H, from the second section 128b to the second cable hole 130b. The third wire-binding hole 132c extends partially through the height H, from the third section 128c to the third cable hole 130c.

[0029] The first wire-binding hole 132a has a first longitudinal axis Al that is angled at an angle a relative to a second longitudinal axis A2 of the second wire-binding hole 132b. The first longitudinal axis Al is angled and oriented to intersect, at a point P, a third longitudinal axis A3 of the third wire-binding hole 132c. The third longitudinal axis A3 of the third wire-binding hole 132c is angled at an angle β relative to the second longitudinal axis A2 of the second wire-binding hole 132b. In the example of FIG. 3, angles a and β are symmetrically identical.

[0030] In Fig. 3, the top surface 122b of the first set screw 122 is generally flush with the first section 128a of the wire-binding face 128. The first section 128a is inclined at an angle Θ relative to the second section 128b of the wire-binding face 128. Similarly, the third section 128c is inclined at an angle κ relative to the second section 128b of the wire-binding face. In the example of FIG. 3, angles Θ and κ are symmetrically identical.

[0031] The second set screw 124 is illustrated prior to being secured in the third wire-binding hole 132c. An alien wrench 136 is inserted into the tool-receiving hole 124a to fasten the second set screw 124 into the third wire-binding hole 132c, which includes a set of internal threads 138 for matching the threads of the second set screw 124.

[0032] The hourglass-shaped fastener 123 is threadedly engaged within the second wire-binding hole 132b via a set of top and bottom internal threads 140a, 140b of the second wire-binding hole 132b. When the hourglass-shaped fastener 132 is positioned in the second wire-binding hole 132b, with the top surface 123g being positioned generally flush with the second section 128b of the wire-binding face 128, the hourglass section 123 a matches the contour of the first cable hole 130a and the contour of the third cable hole 130c. Given that the upper section 123b of the hourglass section 123 a, is generally narrower than the top threaded section 123 d, this position allows the hourglass-shaped fastener 123 to clear entirely the first cable hole 130a and the third cable hole 130c. In turn, the clearance facilitated by the matching contours of the upper section 123b and the adjacent cable holes 130a, 130c provides unobstructed insertion of power cables 106 into the respective cable holes 130a, 130c.

[0033] The hourglass-shaped fastener 123 is optionally asymmetrical along its longitudinal axis, having the upper section 123b generally longitudinally smaller than the lower section 123c. One advantage of having an asymmetrical shape is to have the first cable hole 130a and the third cable hole 130c unencumbered throughout a range of positions of the hourglass-shaped fastener 123, as the hourglass-shaped fastener 123 is threaded/unthreaded into the second wire-binding hole 132b.

[0034] The second cable hole 130b is positioned as low as possible from a bottom face 148, at a minimum distance X, to facilitate insertion of as many threads as possible for the hourglass-shaped fastener 123 into the second wire -binding hole 132b. The minimum distance X is dependent on a minimum clearance Y between the periphery of the second cable hole 130b and an internal edge of a mounting hole 149.

[0035] The mechanical lug assembly 104 includes a pair of protrusions 150 extending outwards from left and right faces 151, 152. The protrusions 150 are added for increased strength near the outer periphery of the first and third cable holes 130a, 130c.

[0036] In reference to FIGs. 4 and 5, the configuration of the mechanical lug assembly 104 facilitates attachment of power cables in a smaller available space than otherwise possible. For example, FIG. 4 illustrates a configuration in which a wide mechanical lug assembly 204, such as might be known in the art, has three cable holes 230a-230c that are positioned alongside each other at the same height HI from a topmost section of a wire-binding face 228. Furthermore, each longitudinal axis B1-B3 of wire- binding holes corresponding to the cable holes 230a-230c is generally parallel to each other, in a generally vertical direction. As a result, the wide mechanical lug assembly 204 has a width Wl that is greater than a width W2 of the mechanical lug assembly 104 described above in reference to FIGs. 1-3.

[0037] Specifically, in reference to FIG. 5 (and as discussed above in reference to FIGs. 1-3), the mechanical lug assembly 104 of the present invention has the three cable holes 130a- 130c positioned such that the first cable hole 130a and the third cable hole 130c are at the same height H2 from the wire-binding face 128, and the second cable hole 130b is at a height H3 from the topmost section of the wire-binding face 128. As a result, the mechanical lug assembly 104 of the present invention is narrower than other configurations (such as the exemplary configuration of the mechanical lug assembly 204), and, accordingly, can facilitate clamping power cables 106 in smaller spaces. The narrower configuration is a result of one or more of the following features: (a) the positioning of the cable holes 130a-130c relative to the wire -binding face 128; (b) the angled orientation of the longitudinal axes Al and A3 of the first and third wire-binding holes 132a, 132c relative to the longitudinal axis A2 of the second wire-binding hole 132b; and (c) the area of reduced material in the hourglass section 123a to eliminate or reduce potential interference between the hourglass-shaped fastener 123 and power cables 106 received respectively in the first cable hole 130a and the third cable hole 130c (i.e., to allow power cables 106 to clear the respective cable holes 130a, 130c).

[0038] In reference to FIGs. 6 and 7, a further example illustrates that the configuration of the mechanical lug assembly 104 facilitates attachment of power cables in a smaller available space than otherwise possible. For example, FIG. 6 illustrates a configuration in which a tall mechanical lug assembly 304, such as known in the art, has three cable holes 330a-330c that are positioned alongside at different heights H6, H7 from a topmost section of a wire-binding face 328. The three cable holes 330a-330c are positioned with a first cable hole 330a positioned lower than a second cable hole 330b, relative to the topmost section of the wire -binding face 328, at the same height H7 as a third cable hole 330a.

[0039] Relative to the tall mechanical lug assembly 304, the mechanical lug assembly 104 of the present invention has both a smaller width (i.e., W2 < W4) and a smaller height (i.e., H4 < H5). The smaller size of the mechanical lug assembly 104 of the present invention is a result, in part, of the specific configuration of the cable holes 130a- 130c having the first cable hole 130a and the third cable hole 130c at a height H2 that is as small as possible to decrease angles a and β as much as possible. For example, the lower position of the first cable hole 330a and third cable hole 330c of the tall mechanical lug assembly 304 (i.e., H7 > H2) results in a wider separation width W5 between the two cable holes 330a, 330c (i.e., W5 > W3) because the angles of longitudinal axes C 1 , C3 (of the corresponding wire-binding holes of the first and third cable holes 330a, 330c) with respect to the horizontal longitudinal axis C3 (of the corresponding wire-binding hole of the second cable hole 330b) is increased relative to the angles of longitudinal axes Al , A3 (e.g., angle a' > angle a; angle β' > angle β).

[0040] While particular embodiments, aspects, and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.