Patent Application
20180334293
The present disclosure generally relates to endcaps for crossarms used in power transmission systems, systems including a crossarm and an endcap, and related methods of assembly.
Power transmission systems often include above-ground utility poles for suspending electrical power lines. The utility poles are traditionally made from wood, steel, or concrete. When multiple power lines or other related components are supported, a utility pole may include a horizontal crossarm. Crossarms are typically formed of wood, steel, or polymer materials (e.g., plastic or fiberglass), and may be secured to the utility pole through a variety of hardware components. One or more ends of the horizontal crossarm may provide support for one or more suspended power lines. For example, the crossarm may be secured to a ceramic or polymer insulator that attaches directly to a suspended power line.
Crossarms are often formed of a hollow tube of a metal, polymer, or composite material. Unless the cavity of the hollow tube is closed and sealed, birds, insects, and other and other animals may inhabit the cavity, cause damage to certain components, safety issues and/or interfere with maintenance operations. A non-sealed hollow tube may also retain moisture, which may degrade the crossarm over time or promote electrical activity. To solve these issues, an endcap is typically secured to each end of the hollow tube. The endcap is typically secured to the crossarm by bonding to foam injected into the cavity. However, due to process variability, it is possible for the endcap to insufficiently bond with the foam, which may leave it susceptible to failure (by becoming easily dislodged from the crossarm, for example). This problem is typically solved by applying an adhesive to the endcap prior to assembly and/or screwing the crossarm to the endcap, but these solutions are associated with additional assembly time and may compromise the strength and durability of the crossarm and endcap.
One general aspect of the present disclosure includes an endcap for a crossarm. The endcap may have a base portion with a surface configured to face a cavity of a crossarm, a hub extending from the surface and configured to receive a fastening element, a gusset element coupled to the hub, and a brace element. The brace element may be configured to contact an inner wall of the crossarm. The inner wall may at least partially define the cavity. The gusset element may be configured to provide an expansion force to the brace element when the fastening element is received by the hub.
Another general aspect of the present disclosure includes a system having a crossarm, where the crossarm has a cavity defined by at least one inner wall, and an endcap. The endcap may include a base portion configured to at least partially seal an end of the cavity, a hub for receiving a fastening element, a gusset element coupled to the hub, and a brace element secured to the gusset element. The hub may be configured to expand when receiving the fastening element such that the brace element exerts a force on the at least one inner wall of the crossarm.
Another general aspect of the present disclosure is a method including the steps of placing an endcap at least partially within a cavity of a crossarm and receiving a fastening element with a hub of the endcap. The endcap may include a gusset element coupled to the hub and a brace element coupled to the gusset element. Receiving the fastening element may cause the gusset element to provide an expansion force to the brace element.
Various aspects are described below with reference to the drawings, and several of the elements are identified by numerals. The relationship and functioning of the various elements may better be understood by reference to the following description. However, aspects are not limited to those illustrated in the drawings or explicitly described below. The drawings are not necessarily to scale, and in certain instances, details may have been omitted that are not necessary for an understanding of aspects disclosed herein.
In this application, the use of the disjunctive is intended to include the conjunctive. The use of definite or indefinite articles is not intended to indicate cardinality. In particular, a reference to “the” object or “a or an” object is intended to denote also one of a possible plurality of such objects.
Referring to
The first brace element 122A may be secured to a first gusset element 132A. The first gusset element 132A may have a first end 134 attached to a hub 138 and a second end 136 attached to the first brace element 122A. Optionally, the first gusset element 132A may be integrally formed with the hub 138, the first brace element 122A, or both. Similarly, second brace element 122B may be secured to (and integrally formed with) a second gusset element 132B, the third brace element 122C may be secured to a third gusset element 132C, and a fourth brace element 122D may be secured to the fourth gusset element 132D. In some embodiments, a brace element may be defined simply as an end of a gusset element.
An opening 140 may extend at least partially through the hub 138 and/or the base portion 114. In some embodiments (including the depicted embodiment), the opening 140 may extend through the entirety of the base portion 114 and the hub 138. The opening 140 may be configured (e.g., sized, shaped and positioned) to receive the fastening element 106. The fastening element 106 may be a screw, wedge, anchor, pin, hook, or other suitable device. When the fastening element 106 is threaded, the opening may include corresponding female threads. As shown in the depicted embodiment, the fastening element 106 may be inserted into the opening 140 with an outside-in orientation with respect to the cavity 110, but it is also contemplated that the fastening element 106 may be inserted from the inside with an inside-out orientation. The depicted outside-in orientation may be advantageous when it is desirable for the fastening element 106 to be accessible for potential removal of the endcap 102 at a later time, such as during maintenance operations.
The opening 140 may include a default state (e.g., a relaxed state when not engaged by the fastening element 106) and an expanded state. The diameter (or other cross-sectional dimension) of the opening 140 at the end 142 of the hub 138 may be larger when the opening is in the expanded state with respect to the default state. Thus, the opening 140 may move from the default state to the expanded state as it receives the fastening element 106. In some embodiments, the fastening element 106 may have a tapered end 144 (see
As the opening 140 moves from its default state to the expanded state, it may provide an outward-facing or expansion force on the gusset elements 132A, 132B, 132C, and 132D. As a result, the gusset elements 132A, 132B, 132C, and 132D may provide a corresponding outward-facing or expansion force to the respective brace elements 122A, 122B, 122C, and 122D, which may provide a tendency for the brace elements 122A, 122B, 122C, and 122D to move/expand outwards. When the brace elements 122A, 122B, 122C, and 122D are placed within the cavity 110, the brace elements may move towards and engage their respective inner walls 126A, 126B, 126C, and 126D. Then, as the fastening element 106 continues to expand the opening 140, the gusset elements 132A, 132B, 132C, and 132D may begin to compress. The compression may in turn cause the engagement surfaces 124A, 124B, 124C, and 124D to exert a force (i.e., the expansion force) on their respective inner walls of the cavity 110, thereby increasing the maximum static friction between the engagement surfaces 124A, 124B, 124C, and 124D and the inner walls 126A, 126B, 126C, and 126D. As a result, the endcap 102 may become secured to the crossarm 104 in a substantially fixed manner.
When the endcap 102 is not engaged with the fastening element 106, the endcap 102 may be dimensioned such that the width W (defined in this embodiment by a distance between the first engagement surface 124A and the third engagement surface 124C) may be slightly smaller than a cross-sectional width of the cavity 110 of the crossarm 104. Similarly, the height H (defined in this embodiment by a distance between the second engagement surface 124B and the fourth engagement surface 124D) may be slightly smaller than a cross-sectional height of the cavity 110 of the crossarm 104. Advantageously, these dimensions may provide simple and efficient installation of the endcap 102 at the end of the crossarm 104, either prior to, during, or after installation of the crossarm 104 on a greater power system. It is also contemplated that at least one of width W and the height H of the endcap 102 may be slightly larger than respective cross-sections of the crossarm 104 prior to installation, particularly when the gusset elements 132A, 132B, 132C, and 132D are capable of being at least partially moved or compressed by hand. Such an embodiment may provide a small amount of friction between the engagement surfaces 124A, 124B, 124C, and 124D and the cavity 110 during the installation process (but prior to tightening a fastening element completely), which may be advantageous when it is desirable to retain the endcap 102 in place during installation at a worksite but to wait to finalize tightening until after adjustment of other components, for example. In one non-limiting embodiment, the width W may be about 5.4 inches and the height may be about 3.6 inches when the endcap 102 is in a default state, but any other suitable dimensions may be used, and the particular dimensions may be determined and selected based on the dimensions of the model of the crossarm 104.
When the fastening element 106 is engaged with the endcap 102, static friction forces 160 between the endcap 102 and the inner walls of the crossarm 104 may counteract a force 162 pulling the endcap 102 along the longitudinal axis of the crossarm 104. In one test performed by the present inventors, a crossarm and endcap formed in accordance with the present disclosure (without foam in the cavity 110) successfully resisted a force 162 of 35 pounds prior to the endcap moving with respect to the crossarm. With the addition of foam, the design exceeded the load capacity of the testing device (which was 50 pounds). These results represent a substantial improvement with respect to available endcaps at the time of filing of this application, which typically can be removed from a crossarm by applying a 5 pound force or less.
Specific embodiments have been described for the purpose of illustrating the manner in which the aspects of the present disclosure are used. It should be understood that the implementation of other variations and modifications of the embodiments described herein and their various aspects will be apparent to one skilled in the art, and that the invention is not limited by the specific embodiments described.
