Grounding rope guide for a dynamo-electric machine

A shaft grounding apparatus including a grounding rope in electrical contact with ground, and an adjustable rope guide configured to guide the grounding rope on an electrically conductive surface of a rotating shaft of an electric machine. The adjustable rope guide includes a plurality of articulating segments configured to provide the adjustable rope guide with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft.

TECHNICAL FIELD

The disclosure is directed to a guide for maintaining a grounding rope against a rotating mechanism of an electric machine. More particularly, the disclosure is directed to an adjustable rope guide configured to guide a grounding rope on an electrically conductive surface of a rotating shaft of an electric machine.

BACKGROUND

In many electric devices, such as electric generators and electric motors, stray voltage may build up on components of the electric device which may adversely affect components of the device, such as bearings within the electric device, and shorten the life of the electric device. In order to prevent current flow through these components, a grounding apparatus may be used to ground components of the electric device. Such grounding apparatus include grounding brushes, grounding straps, grounding ropes and other grounding devices configured to ground the rotating shaft of the electric device.

Accordingly, there is a need to provide alternative shaft grounding apparatus to ground components of an electric device, such as the rotating shaft of an electric device. It may be desirable to provide a shaft grounding apparatus including an adjustable grounding rope guide with a variable radius of curvature to accommodate a range of shaft sizes and/or configurations.

SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing grounding rope guiding structures and assemblies, and uses thereof.

Accordingly, one illustrative embodiment is a shaft grounding apparatus including a grounding rope in electrical contact with ground, and an adjustable rope guide configured to guide the grounding rope on an electrically conductive surface of a rotating shaft. The adjustable rope guide is adjustable between a first position having a first radius of curvature and a second position having a second radius of curvature greater than the first radius of curvature to provide the adjustable rope guide with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft. For instance, the adjustable rope guide may include a plurality of articulating segments configured to provide the adjustable rope guide with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft.

Another illustrative embodiment is a rope guide for a shaft grounding apparatus. The rope guide includes a first guide segment pivotably coupled to a second guide segment. The first guide segment has a first end, a second end, and a channel extending from the first end to the second end for receiving a grounding rope therein. Similarly, the second guide segment has a first end, a second end, and a channel extending from the first end to the second end for receiving a grounding rope therein. The channel of the first guide segment is aligned with the channel of the second guide segment to permit the grounding rope to extend there along.

Yet another illustrative embodiment is a method of grounding a rotating shaft of a dynamo-electric machine. The method includes placing an electrically grounded rope in contact with a circumferential surface of the rotating shaft. An adjustable rope guide is positioned over the rope. The adjustable rope guide is configured to guide the rope on the circumferential surface of the rotating shaft. The adjustable rope guide includes a plurality of articulating segments configured to provide the adjustable rope guide with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft. A first articulating segment of the adjustable rope guide is pivoted relative to a second articulating segment of the adjustable rope guide to adjust the radius of curvature of the adjustable rope guide to match the radius of curvature of the rotating shaft.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the aspects of the disclosure.

DETAILED DESCRIPTION

FIG. 1illustrates a portion of an electric machine2having a rotating mechanism, such as a rotating shaft4. The electric machine2may be a dynamo-electric machine, such as an electric generator which converts mechanical energy into electrical energy, or an electric motor which converts electrical energy into mechanical energy. Accordingly, the rotating shaft4may be a collector ring, or similar structure, of an electric generator or a commutator, or similar structure of an electric motor adapted and configured to interact with or be a part of a sliding connection to complete an electrical circuit between a fixed and a moving conductor to pass electrical current therebetween. For example, in at least some generators or motors, the collector rings or commutators are adapted and configured to complete a circuit with brush assemblies or riggings within the generator or motor. Those of skill in the art will recognize that the size and configuration of the rotating shaft4may vary, depending on the type and/or size of the generator or motor in which the rotating shaft4is used. For example, in some industrial applications, the rotating shaft4may have a diameter of 10 inches or more, 12 inches or more, 14 inches or more, 16 inches or more, 18 inches or more, 20 inches or more, 22 inches or more, or 24 inches or more. In other applications, the rotating shaft4may have a diameter of 10 inches or less, 8 inches or less, or 6 inches or less.

The rotating shaft4, a portion of which is illustrated inFIG. 1, may be an elongate cylindrical shaft having an electrically conductive outer peripheral surface6configured to be in sliding electrical contact with one or more brushes of a brush holder assembly. An exemplary brush holder assembly is described in U.S. Pat. No. 7,034,430, herein expressly incorporated by reference in its entirety. In some instances, a shaft grounding apparatus20may be positioned proximate the rotating shaft4to ground the rotating shaft4. For example, a mounting fixture10may be used to position the shaft grounding apparatus20in close proximity to the rotating shaft4. In some instances, the mounting fixture10may include a first end12mounted to a base8, or other stationary structure, and a second end14mounted to the shaft grounding apparatus20. One such mounting fixture10, is further described in and relates to the subject matter contained in the U.S. patent application entitled MOUNTING FIXTURE INCLUDING AN ARTICULATION JOINT filed on Aug. 5, 2011 by inventor Robert S. Cutsforth and having Ser. No. 13/204,176, which is expressly incorporated herein by reference in its entirety. However, it is understood that the mounting fixture10of any desired configuration to position the shaft grounding apparatus20in close proximity to the rotating shaft4.

The shaft grounding apparatus20may include an electrical box22housing components of the shaft grounding apparatus20. For example, the electrical box22may include one or more, or a plurality of brush holders30including brushes32in electrical contact with the electrically conductive peripheral surface6of the rotating shaft4. The brush holders30may also include a handle34for removing the brush holder30from the electrical box22. In some instances, the brush holders30may be similar to those described in U.S. Pat. No. 7,034,430. The electrical box22may also include a control box24for controlling the flow of electricity from the electrical box22.

The shaft grounding apparatus20may also include a rope guide50extending from the electrical box22. For example, the electrical box22may include first and second side panels26secured (e.g., bolted) to a mount28of the mounting fixture10and to the rope guide50.

Turning toFIGS. 2 and 3, the rope guide50may be an adjustable rope guide configured to guide a grounding rope40on the electrically conductive surface6of the rotating shaft4. For instance, the adjustable rope guide50may be adjustable between a first position having a first radius of curvature and a second position having a second radius of curvature greater than the first radius of curvature to provide the adjustable rope guide50with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft4. In some embodiments, the adjustable rope guide50may include a connector segment56and a plurality of articulating segments52configured to provide the adjustable rope guide50with a variable radius of curvature to closely follow a radius of curvature of the rotating shaft4. In some embodiments, the connector segment56and/or the articulating segments52may be formed of a polymeric material, such as injection molded of a polymeric material, making the components of the rope guide50electrically insulated.

Depending on the diameter of the rotating shaft4, and thus the length of the grounding rope40, the rope guide50may include one, two, three, four, five, six or more articulating segments52pivotably coupled together at hinge points62. For example, the illustrated rope guide50includes a first articulating segment52a, a second articulating segment52b, a third articulating segment52c, a fourth articulating segment52d, and a fifth articulating segment52e, with a first hinge point62abetween the first and second articulating segments52a,52b, a second hinge point62bbetween the second and third articulating segments52b,52c, a third hinge point62cbetween the third and fourth articulating segments52c,52d, and a fourth hinge point62dbetween the fourth and fifth articulating segments52d,52e. The first articulating segment52amay also be pivotably coupled to the connector segment56at a hinge point66.

The electrical pathway for grounding the rotating shaft4may be further understood with reference toFIG. 3. The electrical pathway may include a grounding rope40formed of a conductive material, such as copper or a copper alloy. The grounding rope40, which extends through a channel70of the rope guide50, may be positioned against the conductive surface6of the rotating shaft4such that the rotating shaft4slides against the grounding rope40as the rotating shaft4is rotating. The grounding rope40may be formed of a plurality of twisted multi-filar strands of conductive material, such as copper, or a copper alloy wires. In other instances, the grounding rope40may have a different configuration. As used herein, the term “grounding rope” includes alternative configurations such as a cable, wire, braid, band, strap or other elongate electrically conductive structure.

The grounding rope40may include a first end42coupled to a component in the electrical box22and a second end44hanging over the rotating shaft4in the direction of rotation of the rotating shaft4. In some instances, the grounding rope40may have a length such that about 1 to 2 inches of the grounding rope40extends along the tangent line beyond the tangent between the conductive surface6and the grounding rope40.

The first end42of the grounding rope40may be secured to a brush holder30in the electrical box22. For example, the first end42of the grounding rope40may be clamped between two plates of the brush holder30in some instances. One of the strands46of the grounding rope40may extend further and be secured to a terminal of the brush holder30with a shunt48extending from the brush32of the brush holder30, also in contact with the conductive surface6of the rotating shaft4. From the terminal of the brush holder30, the electrical pathway may pass through the control box24to a grounding wire36to ground38. Thus, the grounding rope40may be connected to ground38through the electrical pathway passing through the electrical box22, and thus grounded.

FIG. 4illustrates the rope guide50extending from the electrical box22with the rotating shaft4removed to further illustrate features of the assembly. For example, the rope guide50is illustrated as including two parallel channels70separated by a dividing wall74configured for positioning a pair of grounding ropes40around the rotating shaft4in parallel with each other. It is understood, however, that in other embodiments the rope guide50may include one channel70, or may include three, four, or more parallel channels70for guiding grounding ropes40against the conductive surface6of the rotating shaft4.

FIG. 5is an enlarged view illustrating the connection between the connector segment56of the rope guide50and the side panels26of the electrical box22. As shown inFIG. 5, the connector segment56may include a first slot58and a second slot60, each configured to receive a fastener, such as a threaded bolt72, therein. The first slot58may be located above the second slot60. Each slot58,60may be defined by a rim of material of the connector segment56. It is understood that although only one side of the connector segment56is shown inFIG. 5, the opposite side of the connector segment56may be similarly configured with a first slot and a second slot to permit adjustment of the connector segment56relative to the electrical box22. The threaded bolts72may extend through holes in the side panels26into the slots58,60of the connector segment56, and may be slidable along the extents of the slots58,60. For example,FIG. 6Aillustrates the threaded bolts72positioned in the slots58,60with the connector segment56at an intermediate position. Arrows shown inFIG. 6Aillustrate the threaded bolts72may travel back and forth along the slots58,60to adjust the angle of the connector segment56relative to the electrical box22. In some embodiments the first slot58may be an arcuate slot, while the second slot60may be an arcuate slot or a straight slot. In other embodiments the first slot58may be a straight slot, while the second slot60may be an arcuate slot or a straight slot.

FIG. 6Billustrates the connector segment56in a first position in which the connector segment56has been adjusted to a first fullest extent permitting the rope guide50to accommodate the smallest diameter rotating shaft4possible, whileFIG. 6Cillustrates the connector segment56in a second position in which the connector segment56has been adjusted to a second fullest extent permitting the rope guide50to accommodate the largest diameter rotating shaft4possible. In the first fullest extent position, shown inFIG. 6B, a first threaded bolt72is positioned at a first end of the slot58and a second threaded bolt72is positioned at a first end of the slot60, the first ends being located toward a first end of the connector segment56. In the second fullest extent position, shown inFIG. 6C, the first threaded bolt72is positioned at a second end of the slot58and the second threaded bolt72is positioned at a second end of the slot60, the second ends being located toward a second end of the connector segment56. Thus, the distance between the first ends of the slots58,60may be equal to the distance between the second ends of the slots58,60, however, the first end of the slot60may be closer to the slot58than the second end of the slot60. The connector segment56may be adjusted to any position between the first fullest extent shown inFIG. 6Bto the second fullest extent shown inFIG. 6Cby moving the threaded bolts72along the elongated slot58and/or the elongated slot60to accommodate a variety of sizes of rotating shafts4. Once the connector segment56has been adjusted to the desired position, the threaded bolts72may be tightened to lock the connector segment56in place relative to the electrical box22.

An exemplary configuration and arrangement of the articulating segments52and associated clamping members80is illustrated inFIGS. 7-13. It is noted that each of the articulating segments52may be substantially similar to other articulating segments52, thus described features, configurations, and aspects described with respect to an articulating segment52may be attributed to any of the articulating segments52of the rope guide50. The articulating segments52may include a first end132and a second end134, with the channels70extending from the first end132to the second end134. The channels70of an articulating segment52may be aligned with the channels70of an adjacent articulating segment to provide continuous channels70extending along the rope guide50. The articulating segments52may be configured such that a first end portion of an articulating segment52overlaps a second end portion of an adjacent articulating segment52. For example, a first end portion proximate the first end132of the second articulating segment52bmay extend into a second end portion proximate the second end134of the first articulating segment52a, while a second end portion proximate the second end134of the second articulating segment52bmay extend over a first end portion proximate the first end132of the third articulating segment52c. Each articulating segment52of the rope guide50may be similarly arranged with adjacent articulating segments52. It is noted that in other embodiments the overlapping portions may be reversed, if desired, with the first end portion of an articulating segment52extending over the second end portion of an adjacent articulating segment52.

In some embodiments, each guide segment52may include an arcuate node110at the first end132and an arcuate extension120at the second end134. The arcuate extension120of the first guide segment52amay be configured to be slidably disposed over the arcuate node110of the second guide segment52b, the arcuate extension120of the second guide segment52bmay be configured to be slidably disposed over the arcuate node110of the third guide segment52c, the arcuate extension120of the third guide segment52cmay be configured to be slidably disposed over the arcuate node110of the fourth guide segment52d, the arcuate extension120of the fourth guide segment52dmay be configured to be slidably disposed over the arcuate node110of the fifth guide segment52e, etc.

Each of the guide segments52may be configured to pivot with respect to an adjacent guide segment52about a pivot axis X to adjust the radius of curvature of the rope guide50. For example, the second end134of the guide segments52may include a post90on each side of the guide segment52centered on the pivot axis X about which the guide segments52may pivot. The arcuate node110may include an arcuate rib112configured to be slidably disposed in an arcuate slot94of the arcuate extension120when the guide segments52are pivoted with respect to one another.

Once adjacent guide segments52have been pivoted to a desired radius of curvature, the guide segments52may be clamped together to lock adjacent guide segments52from further pivotable movement with respect to each other. For instance, a first clamp80may be used to clamp the first and second guide segments52a,52btogether at the first hinge point62a, a second clamp80may be used to clamp the second and third guide segments52b,52ctogether at the second hinge point62b, a third clamp80may be used to clamp the third and fourth guide segments52c,52dtogether at the third hinge point62c, and a fourth clamp80may be used to clamp the fourth and fifth guide segments52d,52etogether at the fourth hinge point62d. It is noted that clamping at each of the hinge points62with a clamp80may be substantially similar to other hinge points62, thus described features, configurations, and aspects described with respect to clamping at a hinge point62may be attributed to any of the hinge points62of the rope guide50.

For example, the adjustable rope guide50may include a clamp80extending over the arcuate extension120of the first guide segment52aand the arcuate node110of the second guide segment52bconfigured to clamp the arcuate extension120of the first guide segment52aagainst the arcuate node110of the second guide segment52b. The clamp80may include a first arm82coupled to a first side of the first guide segment52a, a second arm84coupled to a second side of the first guide segment52b, and an intermediate portion86extending over the arcuate extension120. The clamp80may include a threaded fastener88extending through a threaded bore of the intermediate portion86to press against the arcuate extension120and exert a clamping force against the arcuate extension120. In some instances, the first arm82may be coupled to a post90on the first side of the first guide segment52aand the second arm84may be coupled to a post90on the second side of the first guide segment52a. For example, the first arm82of the clamp80may include an opening98for receiving a first post90of the first guide segment52aand the second arm84of the clamp80may include an opening98for receiving a second post90of the first guide segment52a. The clamp80may pivot about posts90extending from opposite sides of the first guide segment52a, and thus the pivot axis X. The first end132of the second guide segment52bmay include a socket130having an arcuate curvature on each side of the second guide segment52bfor receiving the posts90of the first guide segment52a. The posts90may be pivotably disposed in the sockets130when the guide segments52are coupled together.

The clamp80may be coupled to the second guide segment52bsuch that the clamp80moves with the second guide segment52bwhen the first guide segment52ais pivoted relative to the second guide segment52b. For example, the clamp80may include a tab92extending from the intermediate portion86configured to extend into a notch96defined in the arcuate node110of the second guide segment52b. In some instances, the notch96may be formed in the arcuate rib112of the arcuate node110. Additionally or alternatively, the first and second arms82,84of the clamp80may engage opposing sides of the second guide segment52b. For example, the second guide segment52bmay include projections114extending from the opposing sides of the second guide segment52binto openings116in the first and second arms82,84of the clamp80. In some instances, the openings116may be in communication with the openings98for receiving the posts90of the first guide segment52aWhen assembled together, the tab92may extend through the slot94of the arcuate extension120of the first guide segment52aand into the notch96in the arcuate node110of the second guide segment52b, while the posts90and projections114extend into the openings98and openings116of the clamp80, respectively, on opposing sides of the guide segments52. Thus, the clamp80may couple the first guide segment52ato the second guide segment52b, while allowing pivotable movement therebetween. Accordingly, when the first guide segment52ais pivoted relative to the second guide segment52babout the pivot axis X, the clamp80may pivot about the pivot axis X with the second guide segment52band relative to the first guide segment52a.

Once the guide segments52are oriented and the desired radius of curvature of the guide segments52of the rope guide50is obtained, the guide segments52may be clamped together using the clamps80to lock the guide segments52from further pivotable movement. For example, the threaded fastener88, threadably engaged in the threaded bore of the intermediate portion86of the clamp80, may be rotated to apply a clamping force to the guide segments52. For instance, as shown inFIG. 13, the threaded fastener88may press against the upper surface of the arcuate extension120of the first guide segment52a, which in turn presses against the rib112of the arcuate node110of the second guide segment52b. The clamp80, which also engages the posts90of the first guide segment52a, exerts an opposing force on the posts90. The resulting clamping force may urge the arcuate extension120of the first guide segment52aagainst the arcuate node110(e.g., the rib112) of the second guide segment52band the posts90of the first guide segment52aagainst the sockets130of the second guide segment52b, providing a clamping force to lock the arcuate extension120from pivotable movement relative to the arcuate node110. Thus, as can be seen inFIG. 13, the clamp80may be configured to clamp the first end132of the second guide segment52bbetween the posts90of the first guide segment52aand the arcuate extension120of the first guide segment52a.

In some instances, the first guide segment52amay be clamped against the second guide segment52bat four clamping points. For example, the arcuate extension120may be clamped against the rib112of the arcuate node110at first and second clamping points140a,140b. As shown inFIG. 13, as the threaded fastener88is rotated against the upper surfaces of the first and second arms of the arcuate extension120, the angled surfaces of the arcuate extension120may press against the angled surfaces of the rib112. The wedge-shape of the rib112and the upper portions of the arms of the arcuate extension120may cause the wedge-shaped upper portions of the arcuate extension120to be wedged between the inner surfaces of the clamp80and the angled surfaces of the rib112. It is noted that the gaps144may permit downward movement of the arcuate extension120relative to the arcuate node110as the upper portions of the arms of the arcuate extension120are wedged between the arms82,84of the clamp80and the angled surface of the rib112of the arcuate node110and the clamping force is applied. Due at least in part to the wedge-shaped upper portions of the arms of the arcuate extension120and the wedge-shaped rib112(the wedge-shaped upper portions of the arms of the arcuate extension120being wedged between the inner surfaces of the clamp80and the angled surfaces of the rib112), the clamping forces at the first and second clamping points140a,140bmay increase significantly as the threaded fastener88is rotated downward against the arcuate extension120.

Simultaneously, the posts90may be clamped against the arcuate surfaces of the sockets130at third and fourth clamping points142a,142b. As shown inFIG. 13, as the threaded fastener88is rotated against the upper surfaces of the first and second arms of the arcuate extension120, the clamp80may pull the posts90against the surfaces of the sockets130. Thus, rotating the single threaded fastener88may simultaneously press the first guide segment52aagainst the second guide segment52bat two or more, at three or more, or at four or more discrete clamping points140a,140b,142a,142bto resist movement of the first guide segment52arelative to the second guide segment52b.

It is noted that the hinge point66between the connector segment56and the first guide segment52amay be similar to the hinge points62between adjacent guide segments52. For example, the connector segment56may include an arcuate extension120configured to extend over an arcuate node110of the first guide segment52a, and a clamp80may be positioned over the arcuate extension120to clamp the arcuate extension120to the arcuate node110as described above.

Further illustrated inFIGS. 12 and 13are the channels70configured to receive the grounding ropes40for positioning along the conductive surface6of the rotating shaft4. As can be seen from the figures, a first channel70may be defined between a first side wall76on the first side of the guide segment52and a divider wall74, and a second channel70may be defined between a second side wall76on the second side of the guide segment52and the divider wall74. The channels70may extend parallel to one another to position the grounding ropes40around a portion of the circumference of the rotating shaft4. Thus, the channels70may open out to the bottom of the guide segments52facing the conductive surface6of the rotating shaft4.

The shaft grounding apparatus20may be mounted proximate to the rotating shaft4to electrically ground the shaft4of the electric machine2. For example, the grounding rope40may be placed in contact with the circumferential surface6of the rotating shaft4. For instance, the grounding rope40may be draped over the rotating shaft4with the free second end44of the grounding rope40extending in the direction of rotation of the rotating shaft4. It is noted that in some instances, multiple grounding ropes40(depending on the number of channels70provided in the rope guide50) may be draped over the rotating shaft4to position the ropes40in contact with the surface6of the rotating shaft4.

The adjustable rope guide50may also be positioned around a portion of the circumferential surface6of the rotating shaft4with the rope40extending along the channel70of the rope guide50. In instances in which the rope guide50includes multiple channels70, a rope40may be positioned in and extend along each channel70of the rope guide50.

In order to accommodate the radius of curvature of the rotating shaft4such that the radius of curvature of the articulating segments52of the rope guide50closely matches the radius of curvature of the rotating shaft4and the lower edges of the articulating segments are positioned proximate the surface6of the rotating shaft4, adjacent articulating segments52of the rope guide50may be pivoted relative to each other to adjust the radius of curvature of the adjustable rope guide50. Thus, the rope(s)40may be circumferentially constrained in the channel(s)70of the rope guide50along a portion of the circumference of the rotating shaft4.

In some instances, the connector segment56and the articulating segments52of the rope guide50may be adjusted from a first minimum extent having a radius of curvature of 10 inches or less, 8 inches or less, or 6 inches or less to accommodate a similarly sized rotating shaft4to a second maximum extent having a radius of curvature of 10 inches or more, 12 inches or more, 14 inches or more, 16 inches or more, 18 inches or more, or 20 inches or more to accommodate a similarly sized rotating shaft4. In some instances, the articulating segments52may be adjusted to extend substantially flat, thus accommodating rotating shafts4having an infinitely large diameter. Accordingly, through the adjustability of the rope guide50, the rope guide50may be mounted to a range of sizes of rotating shafts4, such as shafts4having diameters in the range of 6 to 36 inches, in the range of 6 to 24 inches, in the range of 6 to 20 inches, in the range of 6 to 18 inches, in the range of 6 to 16 inches, in the range of 6 to 14 inches, or in the range of 6 to 12 inches, in some instances.

Once the rope guide50has been adjusted to the desired radius of curvature to accommodate the diameter of the rotating shaft4, the hinge points62,66may be clamped to prevent further pivotable movement between adjacent guide segments52, and between the connector segment56and the first guide segment52a. For example, the threaded fasteners88may be tightened against the arcuate extensions120to exert a clamping force to clamp the overlapping portions of the segments together as described above.

Accordingly, the rope guide50may guide the grounding rope(s)40along the rotating surface6of the rotating shaft4. The grounding rope(s)40may be electrically grounded (e.g., connected to ground) to draw stray voltage off of the rotating shaft4to prevent current flow through bearings and/or other components of the electric machine2which could adversely affect the electric machine2.