Patent Description:
When suspending luminaires, it is sometimes necessary to have suspension cables arranged in adjacent pairs. This may be for aesthetic reasons, or may be due to the necessity to achieve a certain number of conductors with powered suspension cables.

Ideally, tension in all of the suspension cables should be even. However, because of granularity in the cable length adjustment mechanisms typically used in suspended luminaires, it is nearly impossible to achieve balanced cable tension in adjacent pairs using these mechanisms alone.

As suspension cable diameter increases, the increment of length adjustment will also typically increase. For powered suspension cable applications, relatively thick cables are required to reduce electrical resistance. These thick cables lead to coarser increments of length adjustment.

The result of the inability to make fine adjustments to cable length is that only one cable of the pair will carry the load, while the other is inevitably slack. Slack cables are detrimental to the aesthetics of the luminaire. With coarser cable length adjustment increments, the degree of slackness can quickly become unacceptable.

Evenly balancing tension between luminaire suspension cables to remove slack is desirable.

<CIT> describes a luminaire mounting and suspension assembly comprising a mounting unit and a plurality of suspension units. <CIT> discloses a device for raising and lowering of a lighting fixture relative to a support attached to a ceiling, the device has a holding element vertically pivotable between edges, which is supported at a middle coupling point of a balance beam.

In one aspect of the invention a luminaire mounting and suspension assembly in accordance with claim <NUM> is provided. The assembly comprises a mounting unit and a plurality of suspension units. Each suspension unit comprises a housing coupled to the mounting unit and a yoke pivotally coupled to the housing at a pivot point, so as to be pivotable about a pivot axis. The yoke comprises a pair of cable grippers, each cable gripper positioned on opposing sides of each pivot point and configured to grip a suspension cable for suspending a luminaire, wherein the pivot axis is perpendicular to axes of the suspension cables and whereby free rotation of the yoke about the pivot axis evenly balances tension between the suspension cables.

In some embodiments the housing comprises a pair of stops for limiting the range of rotation of the yoke about the pivot axis. In some embodiments the yoke comprises a yoke plate with opposing end portions, and each sidewall of the housing comprises a shoulder defining the stop, whereby engagement of one of the end portions with a corresponding one of the stops defines a limit of the range of rotation of the yoke. In some embodiments the range of rotation of the yoke is limited to no greater than approximately <NUM> degrees, or approximately <NUM> degrees, or approximately <NUM> degrees.

In some embodiments the cable grippers are fixedly coupled to the yoke plate. The cable grippers may be aligned along a plane perpendicular to the axis of the pivot axis. In some embodiments the yoke plate comprises a pair of opposing flanged yoke portions extending perpendicularly from the yoke plate, wherein the housing comprises a housing plate and a pair of opposing flanged housing portions extending perpendicularly from the housing plate, and wherein the pivot point includes pivot pin rotatably coupling the flanged yoke portions and flanged housing portions. In some embodiments the yoke is positioned on top of the housing, whereby the yoke is acted on by compression forces due to the load of the luminaire. In other embodiments the yoke is positioned below the housing, whereby the yoke is acted on by tension forces due to the load of the luminaire. The housing plate may comprise a pair of apertures through which the cable grippers and/or suspension cables extend, the apertures dimensioned to accommodate lateral movement of the cable grippers and/or suspension cables due to the free rotation of the yoke.

In some embodiments the housing is pivotally coupled to the mounting unit. In other embodiments, the housing is fixedly coupled to the mounting unit. In some embodiments the suspension units are evenly arranged about the mounting unit. In some embodiments the assembly comprises a pair of power wires, each power wire extending from the mounting unit to a respective one of the cable grippers and connecting to a respective one of the suspension cables.

In one aspect of the invention a luminaire system in accordance with claim <NUM> is provided. The system comprises a mounting and suspension assembly as described herein and a luminaire suspended by the assembly.

In one aspect of the invention a method of suspending a luminaire in accordance with claim <NUM> is provided. The method comprises providing and suspending a luminaire system as described herein; allowing the limitation of the range of motion of the yoke of each of the suspension units to support the luminaire by one of the suspension cables of each of the suspension units; adjusting length of the suspension cables with the cable grippers until any remaining length discrepancy between each pair of the suspension cables can be overcome with the range of motion of the yoke of each suspension unit; and allowing free rotation of the yoke of each suspension unit about the pivot axis to evenly balance tension between the pairs of suspension cables in each of the yokes.

Further aspects and example embodiments are illustrated in the accompanying drawings and/or described in the following description.

The accompanying drawings illustrate non-limiting example embodiments of the invention.

Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

This invention relates to luminaires, and in particular to assemblies, systems and methods for balanced suspension of luminaires where suspension cables are arranged in pairs. Aspects of the invention relate to providing a plurality of suspension units evenly arranged about a mounting unit. Each suspension unit includes a pair of suspension cables from which a luminaire is suspended. Tensioning between each pair of suspension cables is balanced by a yoke mechanism to remove any slack in the suspension cables.

<FIG> show a luminaire system <NUM> according to an embodiment of the invention. Luminaire system <NUM> includes a luminaire <NUM> suspended by a luminaire mounting and suspension assembly <NUM>. Assembly <NUM> includes a mounting unit <NUM> and a plurality of suspension units <NUM>. Suspension units <NUM> are evenly arranged about mounting unit <NUM>. In the illustrated embodiments three suspension units <NUM> are provided. In other embodiments, less or more suspension units <NUM> may be provided. Each suspension unit <NUM> includes a pair of suspension cables <NUM>.

In <FIG> suspension cables <NUM> are equally tensioned and taut whereas in <FIG> suspension cables <NUM> are taut while suspension cables <NUM>' are slack. That is, <FIG> shows system <NUM> before the suspension cables are automatically balanced by the invention as described herein.

<FIG>, <FIG>, <FIG>, <FIG> show assembly <NUM>, and in particular suspension unit <NUM>, in greater detail. Suspension unit <NUM> includes a housing <NUM> and a yoke <NUM>. Housing <NUM> is coupled to mounting unit <NUM>. In some embodiments, housing <NUM> may be pivotally coupled to mounting unit <NUM> at pivot points <NUM>. In other embodiments, housing <NUM> may be fixedly coupled, or integrally formed with, mounting unit <NUM>.

Housing <NUM> is pivotally coupled to yoke <NUM> at pivot point <NUM>, so as to be pivotable about a pivot axis. In some embodiments, a pair of cables grippers <NUM> is mounted on yoke <NUM>. In other embodiments, cable grippers <NUM> may be integrally formed with yoke <NUM>. Cable grippers <NUM> are configured, as known in the art, to grippingly engage and disengage a suspension cable extending therethrough to adjust the length of suspension cable <NUM> for suspending luminaire <NUM>. Power wires <NUM> extend from mounting unit <NUM> to a respective one of cable grippers <NUM> and connect to a respective one of suspension cables <NUM> to deliver power to luminaire <NUM>.

Cable grippers <NUM> are positioned on yoke <NUM> equidistantally on either side of pivot point <NUM>. The axes of suspension cables <NUM> are perpendicular to the axis of pivot point <NUM>. Accordingly, once the lengths of suspension cables <NUM> are set by cable grippers <NUM>, free rotation of yoke <NUM> about pivot axis evenly balances tension between the pair of suspension cables <NUM>.

Rotation of yoke <NUM> is limited to a range of rotation <NUM> as described herein. Housing <NUM> includes a pair of stops <NUM>. In some embodiments, stops <NUM> are shoulders of sidewalls <NUM> of housing <NUM>. Yoke <NUM> includes a yoke plate <NUM> to which cable grippers <NUM> are fixed. Cable grippers <NUM> may be aligned along a plane perpendicular to the axis of pivot point <NUM>.

Yoke plate also has opposing end portions <NUM>. As shown best in <FIG>, yoke plate <NUM> spans housing <NUM> such that an end portion <NUM> will engage a shoulder <NUM> at one extreme of range of rotation <NUM> of yoke <NUM>, and the other end portion <NUM> will engage the other shoulder <NUM> at the other extreme of range of rotation <NUM> of yoke <NUM>. <FIG> shows rotational movement of yoke <NUM>, indicated by arrow <NUM>, and the resulting vertical displacement of cable grippers <NUM> (and therefore suspension cables <NUM>), indicated by arrow <NUM>. This vertical displacement defines the fine adjustment that evenly balances the tensioning between the pairs of suspension cables <NUM>.

In some embodiments, range of rotation <NUM> of yoke <NUM> is limited to no greater than approximately <NUM> degrees, or approximately <NUM> degrees, or approximately <NUM> degrees.

Yoke plate <NUM> includes a pair of opposing flanged yoke portions <NUM> extending perpendicularly from the front and back of yoke plate <NUM>. Housing <NUM> includes a housing plate <NUM> and a pair of opposing flanged housing portions <NUM> extending perpendicularly from the front and back of housing plate <NUM>. Pivot point <NUM> includes a pin <NUM> rotatably coupling the flanged yoke portions <NUM> and flanged housing portions <NUM>, as best shown in <FIG>.

In the illustrated embodiment, yoke <NUM> is positioned on top of housing <NUM>, and the load of luminaire <NUM> results in compression forces acting on yoke <NUM> as shown in <FIG>. As shown in <FIG>, if the load is uneven (i.e., one cable <NUM> is taut and the other cable <NUM>' is slack as shown in <FIG>), then yoke <NUM> will pivot until it reaches equilibrium with balanced loads as shown in <FIG> (i.e., both cables <NUM> are taut, as shown in <FIG>).

In other embodiments, yoke <NUM> may be positioned below housing <NUM>, and the load of luminaire <NUM> results in tension forces acting on yoke <NUM>. If the load is uneven, yoke <NUM> will pivot until it reaches equilibrium as shown in <FIG>.

Regardless of whether yoke <NUM> is positioned above or below housing <NUM>, the geometry of luminaire <NUM> and the additional suspension units <NUM> (and their respective suspension cables <NUM>) ensure luminaire <NUM> is restricted from rotating around an axis parallel to the pivot axis. In other words, once equilibrium is achieved in each yoke <NUM> of assembly <NUM>, luminaire system <NUM> is stable and not susceptible to oscillation.

As shown best in <FIG>, housing <NUM> may be pivotally coupled to mounting unit <NUM>. In other embodiments, housing <NUM> may be fixedly coupled, or integrally formed with, mounting unit <NUM>.

As shown best in <FIG>, housing plate <NUM> may include a pair of apertures <NUM> through which cable grippers <NUM> and/or suspension cables <NUM> extend. Apertures <NUM> are dimensioned to accommodate lateral movement of cable grippers <NUM> and/or suspension cables <NUM> as yoke <NUM> rotates to achieve equilibrium.

In operation, a luminaire system <NUM> is provided and suspended. The limitation of range of motion <NUM> of yokes <NUM> allows one of each of the pairs of the suspension cables <NUM> of each of the suspension units <NUM> to stably support luminaire <NUM>. The length of suspension cables <NUM> is adjusted using the mechanism of cable grippers <NUM> until any remaining length discrepancy between each pair of suspension cables <NUM> can be overcome with the range of motion of yoke <NUM> of each suspension unit <NUM> (i.e., vertical displacement <NUM> shown in <FIG>). Then, free rotation of yoke <NUM> of each suspension unit <NUM> about its pivot axis will evenly balance tension between the pairs of suspension cables <NUM> in each of yokes <NUM> to remove any slack and provide tautness for each suspension cable <NUM> of luminaire system <NUM>.

Claim 1:
A luminaire mounting and suspension assembly (<NUM>) comprising:
a mounting unit (<NUM>);
a plurality of suspension units (<NUM>),
characterized in that
each suspension unit (<NUM>) comprises:
a housing (<NUM>) coupled to the mounting unit (<NUM>); and
a yoke (<NUM>) pivotally coupled to the housing (<NUM>) at a pivot point (<NUM>) so as to be pivotal about a pivot axis, the yoke (<NUM>) comprising a pair of cable grippers (<NUM>), each cable gripper (<NUM>) positioned on opposing sides of each pivot point (<NUM>) and configured to grip a suspension cable (<NUM>) for suspending a luminaire (<NUM>);
wherein the pivot axis is perpendicular to axes of the suspension cables (<NUM>); and
whereby free rotation of the yoke (<NUM>) about the pivot axis evenly balances tension between the suspension cables (<NUM>).