Patent Application
20120286055
The present disclosure generally relates to embedded track systems, such as those for streetcars.
In current projects to construct embedded track systems for light rail vehicles (LRV's) and streetcar operations, the switches and crossings (known as “special trackwork” (STW) assemblies) are usually housed in a reinforced concrete outer structural basin with a lining of composite plastic sheeting to provide electrical isolation. The plastic lining is overlapped and heat-sealed all around to be water and electrically tight. Occasionally, a lining of polyurea spray-on coating has been used in place of plastic sheeting.
After the lining is complete, metal components of the STW assemblies are assembled inside the lined tub while taking care to avoid punching holes in the lining. The desire to prevent the formation of holes is apparent in that many specifications call for the use of a layer of asphaltic protection board. Portland cement concrete is placed, usually in a 2-pour sequence, to lock the STW assembly in place, and also to provide a pavement surface for vehicular and pedestrian traffic.
In both cases noted above, electrical isolation often does not meet the specifications for track-to-earth resistivity because of holidays in the lining. Additionally, both methods are labor-intensive and require special skills and equipment to install. The overall installation costs are also quite high, as a number of complicated steps are typically required—a fairly deep excavation, formwork and rebar to construct the basin, the considerable expense of the material and labor to install the isolation lining—plus the cost of installing and cementing in the STW assembly itself.
Systems and related methods involving isolation tubs are provided. In this regard, an exemplary embodiment of a system comprises: an isolation tub formed of fiberglass reinforced plastic resin, the tub defining a reservoir; concrete positioned within the reservoir; and rails extending across the tub and being supported by the concrete, the rails being spaced from each other to form a special trackwork (STW) assembly.
Another exemplary embodiment of a system comprises: a preformed center section having a perimeter edge; a preformed first side section having a perimeter edge; a preformed second side section having a perimeter edge; a preformed end section having a perimeter edge; first and second rail channels; and a cap strip defining a top surface and having a channel facing away from the top surface; the center section, the first side section and the second side section being arranged such that the center section is positioned between the first side section and the second side section and bonded therebetween; the center section, the first side section, the second side section and the end section being bonded together to form a portion of an integrated tub defining a reservoir; corresponding portions of the respective perimeters of the center section, the first side section, the second side section and the end section defining an upper edge; the first and second rail channels extending across the upper edge from the reservoir to an exterior of the integrated tub; the cap strip extending along and being bonded to the upper edge such that the upper edge is received within the channel of the cap strip.
An exemplary embodiment of a method for forming special trackwork comprises: arranging preformed fiberglass reinforced plastic resin sections at a location for a special trackwork; sealing joints between the sections to form an integrated tub; and installing rail channels, each of which is sized and shaped to receive a rail, at locations along an upper edge of the integrated tub.
Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure.
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Systems and related methods involving isolation tubs are provided, several exemplary embodiments of which will be described in detail. In this regard, a representative embodiment of a system involves the use of an integrated tub formed of multiple, readily-transportable sections that can be assembled on site. Notably, the sections can be arranged in various configurations to provide tubs of different sizes and shapes. The sections are sealed together to form a watertight, electrical isolation barrier within which numerous track components can be mounted. As such, a representative integrated tub serves as a complete formwork for concrete that is placed inside the integrated tub to support special trackwork (STW) assemblies and remains in place to serve as a paving surface.
With continued reference to the drawings,
Rail channels (e.g., channels 114, 116) and rails (e.g., rails 118, 120) of the system also are depicted. Notably, the portions of the rails shown in dashed lines are portions that interact directly with other components, such as switch throw mechanism 119. Note also that various details that are beyond the scope of this discussion are not depicted.
The tub sections are preferably factory-made in large dimensions proportioned for shipping and handling purposes, and are assembled in the field. For instance, the sections can be sized to permit truck shipment in a nested fashion for economy and can be shipped with lifting lugs already fitted to allow for ease of jobsite handling. In some embodiments, the sections are formed of fiberglass-reinforced plastic resin. For instance, fiberglass reinforced (hand-laid fabrics for laminate schedule) plastic resin of a styrene-diluted unsaturated polyester-based reactive resin compound can be used. As such, the sections exhibit properties such as electrical resistivity, hardness, resistance to aging, and tensile and compressive strength. These properties tend to assure a long, successful service life. It should be noted that other compounds may be used in other embodiments.
In the embodiment of
Side section 106 is elongate in shape and defines a perimeter with edges 134, 135, 136 and 137. Side section 106 also incorporates a bottom wall 138 and a side wall 139. Side section 108 is a duplicate of side section 106 and includes edges 140, 141, 142 and 143, as well as a bottom wall 144 and side wall 145. End section 110 includes edges 146 and 147 and incorporates a bottom wall 148, an end wall 149 and side walls 150, 151. End section 112 is a duplicate of end section 110 and includes edges 152, 153, and walls 154, 155, 156 and 157.
When assembled, edges 133 and 135, and edges 131 and 143 are bonded together. Additionally, edge 152 is bonded to edges 134, 130 and 140, and edge 146 is bonded to edges 136, 132 and 142. As such, an integrated tub is formed that defines a reservoir 160. It should be noted that various configurations other than that depicted in
In
Also shown schematically in
When assembled, like ones of the sections are oriented in end-to-end relationships. By way of example, the first through fourth center sections are arranged in sequence such that section 202 is positioned between sections 201 and 203. Similarly, the first through fourth left side sections are arranged in sequence such that section 212 is positioned between sections 211 and 213. Additionally, like numbered sections are oriented in side-by-side relationships. For instance, first center section 201 is positioned between first left side section 211 and first right side section 221. Further, end section 230 spans the ends of the first sections, while end section 232 spans the opposing ends of the fourth sections to define a reservoir 234.
The sections are bonded together, such as with a plastic resin of a styrene-diluted unsaturated polyester-based reactive resin compound, to form an integrated tub 235 that is generally rectangular in shape when viewed in plan. Thus, tub 235 exhibits symmetry along a longitudinal axis 236.
Additionally, rail channels are included that are attached to the end sections of the tub. For example, end section 230 includes a rail channel 237, and end section 232 includes a rail channel 239.
The lower side portion and the bottom portion define an included angle (θL), which is between approximately 93° and approximately 95°. Preferably, angle (θL) is greater than 90 degrees.
The upper edge is positioned between the lower side portion and the upper side portion. The lower side portion and the upper side portion define an included angle (θU), which is between approximately 175° and approximately 177°. Preferably, angle (θU) is less than 180 degrees.
An uppermost edge 276 of the upper side portion forms a portion of the upper peripheral edge 278 of the tub. Additionally, a trim section 280 is attached to the inner surface 282 of the upper side portion to form a thickened portion of the tub that reinforces the upper peripheral edge. In this embodiment, the trim section is formed of fiberglass reinforced plastic resin that is bonded to the upper side portion.
Interior surfaces 336 of the rail channel are positioned to receive a lining 338 of an electrically insulative material (e.g., an elastomeric infill material). Notably, a corresponding rail extends within the channel and is electrically isolated therein due to the insulative material.
As shown in
As shown in
In block 458, the perimeter of the tub is supported, such as by installing perimeter lumber backing or steel kickers around the sides of the tub to resist bulging during placement of concrete. Alternatively, the outside perimeter can first be partially filled with lean concrete or hot-mix asphalt (HMA) or compacted gravel to provide the desired support. Then, in block 460, notches (e.g., notches 8 inches wide by 8.50 inches in depth) are cut in locations of the tub where rails will cross the perimeter. Alternatively, the notches can be pre-formed into the sections. Regardless of the manner of formation, the notches are preferably centered on the rail CL and in alignment.
In block 462, rail channels are installed at the notches. In some embodiments, the rail channels are 8.00 inches wide×8.50 inches deep×24 inches in length. Additionally, any upstanding, isolating dividers required for rail/signal/Traction Power (TP) return can be installed.
Then, in block 464 cap strip is installed. This can be accomplished by trimming the top edge of tub to within approximately ¼″ of correct grade and then placing the cap strip along the upper perimeter edge of the tub to the exact grade line.
In block 466, a leak check is performed such as by filling the tub with water and also spark checking for holidays with a megger tester. Any leaking areas can be repaired, after removing the water, such as with fiberglass resin overlay. Water is re-introduced and the tub is retested. When electrical and leakage testing is completed successfully, the water is then removed from the tub. Then, in block 468, a concrete “mud” base is poured. In some embodiments, the base is approximately 5-inches thick and includes mesh reinforcement. Notably, the mesh can be made electrically common with TP return with an optional interruptible connection.
In block 470, STW steel is installed in the tub. By way of example, supports such as steel or plastic ties on adjustable screw legs, or some other support, such as DF pads using locating jigs can be used to adjust geometry to the correct profile. If required, concrete reinforcement can be placed that can be made electrically common with the mesh and the TP return with an interruptible connection. In block 472, the rails are electrically insulated such as by using Icosit™ or a similar polyurethane electrically-isolating elastomeric material around the rails in the rail channels. Notably, a spark test can be performed to ensure electrical isolation.
In block 474, STW encasement concrete is placed (e.g., in a 1- or 2-pour method), finished and cured. Then, in block 476, the installation is completed, such as by cleaning up laitance, flangeways, overspill on STW, etc., installing components such as switch machines, and completing electrical hookups. Thereafter, such as depicted in block 478, final checks are performed, such as track-to-earth resistance tests, systems tests, and track/STW operational tests. It should be noted that various items such as sump pumps, drain catch basins, etc. are not covered by the procedure noted above, but may be required as is known.
There may be various reasons for and/or benefits derived from using a system such as described above over that of a conventional PVC/Elvaloy flexible membrane or spray-on coating such as polyurea. Such reasons and/or benefits may include one or more of the following: an integrated tub is strong and may not require the overlay of protection board to prevent damage and punctures; preform section rigidity allows easy installation on vertical surfaces, and the construction of separator dams in the gauge of the track to isolate the signal rail from the TP return rail, or to separate signal circuits; the use of a chopped glass/polyester resin mix for making the splice joints between the panel boards allows fast and easy sealing in 3-way corners and around blockouts as well as flat surfaces with normal construction skills, and the volume resistivity of the joint material is slightly higher than the factory-made board (see CIEMS Test Report #1060411172); sections can be furnished in large sheets (probably 8-ft×30-ft or more) to minimize joints, and in custom shapes where required, and can be bent to fit large-radius curved surfaces; electrically tight joining of the sections is much easier, faster and surer than the heat-sealing of the PVC/Elvaloy membrane, especially in 3-way corners; the sections can be joined to other materials (such as Icosit™) or with concrete and other construction materials using adhesives versus PVC/Elvaloy that is virtually impossible to bond to other materials with an electrically-tight joint; the sections are not prone to small punctures during installation and subsequent track construction, a problem with both flexible membrane and spray-on coatings; no extended cure time of a concrete tub is required prior to installing an integrated tub, as is required by the spray-on coatings; the integrated tub is ready for further construction steps immediately after joints are made; there is no over-spray problem; by eliminating the outside reinforced concrete “bathtub” substantial cost & time savings can be realized; all tasks required to install the system properly are within worker skill sets and equipment commonly found on these types of construction sites.
It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure.
This utility application claims priority to U.S. Provisional Application 61/485,327, which was filed on May 12, 2011, and which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61485327 | May 2011 | US |
