Non-conductive weldable insulated rail joint

Abstract

An insulated joint for forming an electrical boundary between the rails of a railroad track that is resistant to decay resulting from track forces. The insulated joint includes a ceramic material brazed directly to the ends of adjacent rails by a brazing material or by active soldering. The insulated joint provides a mechanical connection as well as electrical insulation between the adjacent rails and does not require any glue or epoxy and employs insulating materials. Because of the continuous mechanical connection, the insulated joint is robust to train movement and forces applied to the rails, and thus avoids flexing as well as degradation of the joint and rail. The ceramic material may be Yttria-stabilized zirconia (YSZ) and the brazing material may be a high-purity active braze alloy of silver, copper, indium and titanium

Description

TITLENON-CONDUCTIVE WELDABLE INSULATED RAIL JOINTBACKGROUND OF THE INVENTION1. FIELD OF THE INVENTION

[0001] The present disclosure relates to insulated rail joints and, more particularly, to a ceramic and steel assembly that can provide a continuous welded rail connection.2. DESCRIPTION OF THE RELATED ART

[0002] Insulated joints are small sections of train tracks where an electrically insulative material, such as polycarbonate, poly-para-phenylene terephthalamide, and similar plastics, and are bolted or epoxied in place. Insulated joints are used globally both in freight and transit markets to allow sections of train tracks to be electrically isolated from one another and thus provide boundary definitions for electrical signals of a standard track circuit. Insulated joints are prone to wear out over time, however, because they are made of materials that flex and eventually decay and thus can become unglued. This decay also causes functional problems that can lead to safety issues and even train derailments.BRIEF SUMMARY OF THE INVENTION

[0003] The present invention provides a robust insulated joint that is resistant to decay and resulting problems. The insulated joint of the present invention is a continuous molecular / metallurgical connection that provides a mechanical connection as well as electrical insulation between adjacent rails. The insulated joint does not require any glue or epoxy and employs insulating materials that are significantly more robust to train movement and forces applied to the rails, and thus avoids flexing as well as degradation of the joint and rail. In an embodiment, the non-conductive weldable insulated rail joint is formed by a ceramic insert brazed in place between two adjacent rails. The ceramic material of the ceramic insert may be Yttria-stabilized zirconia (YSZ) and the brazing material may be a high-purity active braze alloy of silver, copper, indium and titanium.

[0004] In one exemplary embodiment, the insulated joint comprises a first extension rail having a first end, a second extension rail having a second end, and a ceramic insert joining the first end of the first rail section to the second end of the second rail section. The ceramic insert may be brazed to the first end of the first extension rail and to the second end of the second extension rail. The ceramic insert may be formed from a material selected from the group of materials consisting of yttria-stabilized zirconia (YSZ), silicon nitride SiN, yttria-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP), and magnesium oxide partially stabilized zirconia (MgPSZ). The first extension rail and the second extension rail122524429. v1 -12 / 1 / 25may each include a lower portion having a width that is greater than an upper portion to form a shoulder therebetween. The first extension rail and the second extension rail may each include a tapered portion extending longitudinally from the lower portion so that a first free end of the first extension rail opposing the first end and a second free end of the second extension rail have a geometry corresponding to a standard railroad track rail. The ceramic insert may extend in a single plane between the first extension rail and the second extension rail. The ceramic insert may extend between the first extension rail and the second extension rail in a plurality of planes. The first end of the first extension rail and the second end of the second extension rail may be split to form a first groove extending longitudinally within the first end of the first extension rail and a second groove extending longitudinally within the second end of the second extension rail and the ceramic insert extends longitudinally within the first groove and the second groove and transversely between the first end of the first extension rail and the second end of the second extension rail. The insulated joint may have a plurality of dowel pins extending transversely through the first end of the first extension rail, the second end of the second extension rail, and the ceramic insert. The ceramic insert may be an integral unit extending between the first end of the first extension rail and the second end of the second extension rail. The ceramic insert may be formed by separate sections extending between the first end of the first extension rail and the second end of the second extension rail. The ceramic insert may have a first geometry that interlocks with a second geometry formed by the first end of the first extension rail and a third geometry the second end of the second extension rail. The insulted joint may have a configuration selected from the group consisting of a butt joint, a lap joint, a half lap joint, and a spline joint.

[0005] In another embodiment, the present invention may be a method of isolating a second of a railroad track. In one step, the method includes providing an insulated joint comprised of a first extension rail jointed by a ceramic insert to a second extension rail and having a first free end and a second free end. In another step, the method includes welding the first free end of the insulated joint to a first railroad track. In a further step, the method includes welding the second free end of the insulated joint to a second railroad track so that the first railroad track is electrically isolated from the second railroad track. The method may further include the steps of providing a second insulated joint comprised of a third extension rail joined by a second ceramic insert to a fourth extension rail and having a third free end and a fourth free end, welding the third free end of the second insulated joint to a third railroad track, and welding the fourth free end of the second insulated joint to a fourth222524429. v1 -12 / 1 / 25railroad track so that the third railroad track is electrically isolated from the fourth railroad track.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0006] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

[0007] FIG. 1 is a perspective view of an insulated joint according to the present invention.

[0008] FIG. 2 is a pair of graphs comparing deformation test results between a conventional joint (left) and an insulated according to the present invention (right).

[0009] FIG. 3 is a pair of graphs comparing plasticity and fatigue test results between a conventional joint (left) and an insulated according to the present invention (right).

[0010] FIG. 4 is a perspective view of another embodiment of the present invention coupled to standard rails.

[0011] FIG. 5 is a perspective view of the profile of a ceramic insert of the embodiment of FIG. 4.

[0012] FIG. 6 is a side view of a further embodiment of the present invention.

[0013] FIG. 7 is a perspective view of the embodiment of FIG. 6.

[0014] FIG. 8 is a perspective view of the profile of a ceramic insert of the embodiment of FIG. 6 that shows simulation stress test data.

[0015] FIG. 9 is a cross-section view of an insulted joint and a ceramic insert according to the embodiment of FIG. 6.

[0016] FIG. 10 is a perspective view of a ceramic insert of the embodiment of FIG. 6.

[0017] FIG. 11 is a front view of a portion of the ceramic insert of the embodiment ofFIG. 6.

[0018] FIG. 12 is a side view of a ceramic insert of the embodiment of FIG. 6.

[0019] FIG. 13A is a perspective view of an embodiment of a ceramic insert according to the present invention.

[0020] FIG. 13B is a side view of an embodiment of a ceramic insert according to the present invention.

[0021] FIG. 14A is a perspective view of another embodiment of a ceramic insert according to the present invention.

[0022] FIG. 14B is a side view of an embodiment of of the embodiment of a ceramic insert of FIG. 14A.322524429. v1 -12 / 1 / 25

[0023] FIG. 14C is a top view of an embodiment of a ceramic insert of the embodiment of a ceramic insert of FIG. 15B.

[0024] FIG. 15A is a perspective view of another embodiment of a ceramic insert according to the present invention.

[0025] FIG. 15B is a side view of the embodiment of a ceramic insert of FIG. 15 A.

[0026] FIG. 15C is a top view of the embodiment of a ceramic insert of FIG. 15 A.

[0027] FIG. 16 is a perspective view of a further embodiment of a ceramic insert according to the present invention.

[0028] FIG. 17 is a perspective view of an additional embodiment of a ceramic insert according to the present invention.

[0029] FIGS. 18A through 18E are side views of various other embodiments of a ceramic insert according to the present invention.

[0030] FIG. 19 is a perspective view of a railroad track outfitted with an insulated joint according to the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring to the figures, wherein like numerals refer to like parts throughout, there is seen in FIG. 1, an insulated joint 10 according to the present invention. Insulated joint 10 comprises a ceramic insert 12 that is brazed directly to the end of each of two adjacent extension rails 14 and 16 via a brazed junction 18, thereby forming a single, unitary insulated joint 10. The formation of a continuous rail section that still provides electrical insulation avoids degradation that can occur in the weaker materials used with convention joints and the use of glues or epoxies that can break down over time. Ceramic insert 12 may have a thickness of between 1 / 8 and 1 / 2 inches as need to ensure electrical isolation of any voltages to be applied to the rails. Brazing of ceramic insert 12 to adjacent extension rails 14 and 16 may be accomplished by standard brazing processes, e.g., between 900°F - 2200°F. As seen in FIG. 1, ceramic insert 12 extends in a single plane and is used to form a butt joint. As explained in detail herein, ceramic insert 12 may be extend along several different planes to accommodate different shaped joints, such a butt joint, a lap joint, a half lap joint, or a spline joint.

[0032] Ceramic insert 12 may be formed from Yttria-stabilized zirconia (YSZ). Ceramic insert 12 may alternatively be formed from other insulating ceramic compositions, such as SiN, yttria-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP), and magnesium oxide partially stabilized zirconia (MgPSZ). The material for ceramic insert 12 can be selected according to the physical characteristics needed for joint 10, i.e., joint 10422524429. v1 -12 / 1 / 25must be able to withstand the forces associated with incorporation of joint 10 into standard rail lines. For example, joint 10 must be able to support the weight of trains passing over joint 10. Joint 10 must also be able to endure the longitudinal forces associated with the expansion and contraction of the rails in response to changes in ambient temperature.

[0033] When brazed, junction 18 used to connect ceramic insert 12 to extension rails 14 and 16 is preferably comprised of a high-purity active braze alloy of silver, copper, indium and titanium. For example, brazed junction 18 may be formed from a brazing material having the nominal composition of 43.6 percent Ag, 29.1 percent Cu, 24.3 percent In and 3 percent Ti by weight is acceptable. It should be recognized that other brazing materials that provide low melting temperatures and that would allow for one step bonding of ceramic-to-ceramic and ceramic-to-metal surfaces without metallizing, firing and electroplating may be used. Alternatively, bonding approaches other than brazing may be used for joint 10, such as active soldering instead of brazing. For example, S-Bond 220 is a Sn-Ag-Ti based active solder with minor additions of rare earth elements and Ga to promote wetting and adherence to metals, ceramics and composites without the need for chemical flux or metal plating. Alloys such as this are mechanically activated using specific joining processes.

[0034] Ceramic insert 12 may be formed to have a shape that corresponds to the cross-sectional profile of a track rail, as seen in FIG. 1. Testing has demonstrated that the profile may be important for resisting the mechanical forces of a locomotive traveling over insulated joint 10 as the shape of insulated joint 10 and brazed junction 18 is critical to handling both the vertical and longitudinal forces that will be experienced by insulated joint 10 in the field. Accordingly, the present invention includes various geometries of ceramic insert 12 that improve the performance of insulated joint 10, as described further herein.

[0035] Insulated joint 10 is formed by brazing ceramic insert 12 to extension rails 14 and 16 that have been selected in length to form an insulated joint 10 having a total length of, for example, between two to four feet. Depending on the requirements of local governing bodies, joint 10 could also have a length of nineteen feet or longer as desired. For installation in the field, a pre -manufactured insulated joint 10, i.e., ceramic insert 12 coupled to extension rails 14 and 16, may be transported to the location where an electrical boundary is desired.The existing rails may be cut to accommodate insulated joint 10 using conventional rail cutting procedures, insulated joint 10 may be positioned in place, and then extension rails 14 and 16 may be welded to the existing rails using standard welding procedures. Insulated joint 10 therefore provides a continuous, unitary joint between track rails without the need for bolting or epoxying in place and can be installed in a desired location using standard rail522524429. v1 -12 / 1 / 25cutting and welding techniques. Insulated joint 10 will mimic the performance and robustness of continuously welded rail as opposed to conventional joints that are bolted or epoxied in place and can degrade over time.

[0036] Referring to FIGS. 2 and 3, testing of insulated joint 10 when provided as a butt style joint (right panels) demonstrated an 84 percent decrease in deformation as compared to a conventional insulated joint design (left panels). As further seen in FIGS. 2 and 3, insulated joint 10 also experiences significantly less plasticity and fatigue. The various interlocking options for joint 10 described herein experienced even less deformation that conventional designs when tested in a similar manner.

[0037] Referring to FIGS. 4 and 5, insulated joint 10 may be configured to have other geometries that improve the performance of insulated joint 10. For example, as seen in FIG.4, adjacent extension rails 14 and 16 of insulated joint 10 may include a base section 20 that extends on either side of ceramic insert 12 and extends transversely outwardly to provide a lower portion 22 that is wider than the upper portions of standard rails 24 and 26 of the track where insulated joint 10 is to be positioned. Base section 20 includes tapered portions 28 and 30 that extend from either side of wider lower portion 22 to match the geometry of the sides of standard rails 24 and 26 so that the ends of extension rails 14 and 16 match the geometry of standard rails 24 and 26. The shoulder formed by base section 20 relative to the dimensions of standard rails 24 and 26 and extending longitudinally along extension rails 14 and 16 provides more support, stability, and strength to the section of rail where extension rails 14 and 16 and joint 10 are located.

[0038] As seen in FIG. 5, ceramic insert 12 may be provided as a lap joint between extension rails 14 and 16, where ceramic insert 12 has a central section 40 extending vertically and along the longitudinal axis of extension rails 14 and 16 and standard rails 24 and 26. Ceramic insert 12 includes end sections 42 and 44 that extend transversely to the longitudinal axis of extension rails 14 and 16 and standard rails 24 and 26 from the opposing ends 46 and 48 of central section 40, respectively. As further seen in FIG. 5, the cross- sectional profile of end sections 42 and 44 corresponds to the cross-sectional profile of base section 20.

[0039] Referring to FIGS. 6 and 7, ceramic insert 12 of insulted joint 10 may be configured to have a geometry of an interlocking lap joint, where ceramic insert 12 includes a central portion 50 extending transversely for the width of insulated joint 10. Ceramic insert 12 further includes a first portion 52 extending obliquely upwardly from one end of central portion 50 to the upper surface 54 of extension rails 14 and 16. A second portion 56 extends622524429. v1 -12 / 1 / 25obliquely upward from central portion 50 to a third portion 58, that extends obliquely downward to the lower surface 60 of extension rails 14 and 16, thereby forming a tooth 62 that assists with interlocking of extension rails 14 and 16. As further seen in FIGS. 6 and 7, the lower regions of ceramic insert 12 and extension rails 14 and 16 may be wider to provide additional strength and stability to insulated joint 10, while upper surface 54 has a profile that matches standard rails 24 and 26 so that any wheels traveling along standard rails 24 and 26 will functional normally. Insulated joint 10 may optionally include a notch 64 in lower surface 60 to accommodate a rail tie or sleeper. The stress testing of this embodiment of ceramic insert 12 of insulted joint 10 is shown in more detail in FIG. 8 and a cross-sectional view of an interlocking lap joint option for joint 10 is seen in FIG. 9.

[0040] As further seen in FIG. 7, blind drilled and tapped bolt holes 68 may be provided on both sides of the assembly. Conventional joints require users to weld or braze track wires directly to the rail or drill through the I beam, which can weaken the structure. Base section 20 provides additional structure that avoids degrading of the strength of the assembly with blind drilled and tapped holes allowing user to bolt track wires to the rail without the need for brazing or welding.

[0041] As seen in in FIG. 10, first portion 52 has a lower portion 66 with a width corresponding to central portion 50 and an upper portion 70 with a narrower width and upper geometry that corresponds to the upper geometry of extension rails 14 and 16 and thus also standard rails 24 and 26.

[0042] Referring to FIG. 11, upper portion 70 of ceramic insert 12 has a geometry corresponding to that of the upper portion of extension rails 14 and 16 and standard rails 24 and 26, such as a width of 2.7 inches, a height of between 1.5 and 3 inches, as well as upper radii matching extension rails 14 and 16 and standard rails 24 and 26.

[0043] Referring to FIG. 12, ceramic insert 12 when configured with the geometry of an interlocking lap joint may have first portion 52 and third portion 58 oriented at between 30 and 60 degrees relative to the longitudinal axis of extension rails 14 and 16 and standard rails 24 and 26. Given the dimensions of extension rails 14 and 16, ceramic insert 12 extends a total length of between 9 and 15 inches and has an overall height of 6 to 7 inches.

[0044] Referring to FIG. 13, ceramic insert 12 may be integrally formed as a single unit or provided as a plurality of sections, shown as three segments 12a, 12b, 12c as an example, that are brazed into place.

[0045] Referring to FIGS. 14A through 14C, joint 10 may be configured as a half lap joint with ceramic insert 12 inserted between the end of extension rails 14 and 16 and used to722524429. v1 -12 / 1 / 25couple extension rails 14 and 16 together. As seen in FIGS. 14A through 14C, insert 12 may be provided in multiple sections as described above with respect to FIG. 13. As further seen in FIGS. 14A through 13C, one or more dowel pins 88 may extend transversely through the ends of each of extension rails 14 and 16 to further secure ceramic insert 12 in place

[0046] Referring to FIGS. 15A through 15C, joint 10 may be formed similarly to a spline joint with ceramic insert 12 positioned between the ends of extension rails 14 and 16 and formed as a cross having two opposing tongues 80 and 82 that are received by corresponding grooves 84 and 86 formed in the ends of extension rails 14 and 16. As further seen in FIGS. 15A through 15C, one or more dowel pins 88 may extend transversely through the ends of each of extension rails 14 and 16 to further secure ceramic insert 12 in place and ensure that joint 10 can withstand the forces that will occur when a train travels over extension rails 14 and 16 and when extension rails 14 and 16 and the tracks to which they are attached expand and contract in response to temperature changes. The use of dowel pins 88 may also allow ceramic insert 12 to be placed without the need for brazing as insert 12 and dowel pins 88 can be soldered in place.

[0047] FIG. 16 illustrates joint 10 formed as a double tongue and groove and oriented at 90 degrees relative to the positioning seen in FIGS. 15A through 15C. In FIG. 16, dowel pins 88 extend vertically through the ends of extension rails 14 and 16.

[0048] FIG. 17 shows another embodiment of where joint 10 may be configured as a half lap joint with ceramic insert 12 inserted between the end of extension rails 14 and 16 at an orientation that is 90 degrees from that seen in FIGS. 14A through 14C. Joint 10 further includes a plurality of dowel pins 88 that extend transversely relative to the longitudinal axis of extension rails 14 and 16.

[0049] Dowel pins 88 of FIGS. 15A through 15C and FIG. 16 can be formed from steel and welded, brazed, or soldered in place. Joint 10 will continue to provide electrical isolation when dowel pins 88 are used because the cross shape of insert 12 continues to electrically isolate extension rails 14 and 16 even through dowel pins 88 extend therethrough, separates the 2 end pieces of steel entirely. Any dowel pins 88 used in the embodiments seen in FIG. 14 or FIG. 17, or variations thereon, would need to be formed from a dielectric material, such as the various ceramics described herein, as they cannot be electrically conductive.

[0050] FIG. 18A through 18E illustrates alternative designs for ceramic insert 12, where ceramic insert 12 is shaped to provide additional interlocking between extension rails 14 and 16. For example, FIGS. 18A through 18C show ceramic insert 12 having an822524429. v1 -12 / 1 / 25interlocking geometry relative to a first complementary geometry and a second complementary geometry formed into the ends of extension rails 14 and 16, respectively. Ceramic insert 12 thus employs a jigsaw style configuration that provides for physical interlocking of ceramic insert 12 with extension rails 14 and 16 in lieu of or in addition to brazing or welding. FIG 18D shows ceramic insert 12 formed from two members having an interlocking jigsaw configuration, and FIG. 18E shows ceramic insert 12 extending over a circuitous path with a multiple angles to increase the number of interlocking contacts between extension rails 14 and 16.

[0051] Referring to FIG. 19, a first insulated joint 10 may be installed in a railroad track by welding a first end 90 to one standard rail 24 and an opposing end 92 to an adjacent standard rail 26. A second insulated joint 10 may be installed on the other rail of the railroad track proximately to first insulated joint 10. Ceramic insert 12 of each insulated joint 10 thus isolates standard rail 24 from standard rail 26, thereby allowing the two adjacent sections of track to be isolated from each other and provide boundary definitions for electrical signals of a standard track circuit.922524429. v1 -12 / 1 / 25

Claims

CLAIMSWhat is claimed is:

1. An insulated joint for a railroad track, comprising: a first extension rail having a first end; a second extension rail having a second end; and a ceramic insert joining the first end of the first extension rail to the second end of the second extension rail.

2. The insulated joint of claim 1, wherein the ceramic insert is brazed to the first end of the first extension rail and to the second end of the second extension rail.

3. The insulated joint of claim 2, wherein the ceramic insert is formed from a material selected from the group of materials consisting of yttria-stabilized zirconia (YSZ), silicon nitride SiN, yttria-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP), and magnesium oxide partially stabilized zirconia (MgPSZ).

4. The insulated joint of claim 1, wherein the first extension rail and the second extension rail each include a lower portion having a width that is greater than an upper portion to form a shoulder therebetween.

5. The insulated joint of claim 4, wherein the first extension rail and the second extension rail each include a tapered portion extending longitudinally from the lower portion so that a first free end of the first extension rail opposing the first end and a second free end of the second extension rail have a geometry corresponding to a standard railroad track rail.

6. The insulated joint of claim 1, wherein the ceramic insert extends in a single plane between the first extension rail and the second extension rail.

7. The insulated joint of claim 1, wherein the ceramic insert extends between the first extension rail and the second extension rail in a plurality of planes.

8. The insulated joint of claim 1, wherein the first end of the first extension rail and the second end of the second extension rail are split to form a first groove extending longitudinally within the first end of the first extension rail and a second groove extending longitudinally within the second end of the second extension rail and the ceramic insert extends longitudinally within the first groove and the second groove and transversely between the first end of the first extension rail and the second end of the second extension rail.

9. The insulated joint of claim 8, further comprising a plurality of dowel pins extending transversely through the first end of the first extension rail, the second end of the second extension rail, and the ceramic insert.1022524429. v1 -12 / 1 / 2510. The insulated joint of claim 1, wherein the ceramic insert is an integral unit extending between the first end of the first extension rail and the second end of the second extension rail.

11. The insulated joint of claim 1, wherein the ceramic insert is formed by separate sections extending between the first end of the first extension rail and the second end of the second extension rail.

12. The insulated joint of claim 1, wherein the ceramic insert has a first geometry that interlocks with a second geometry formed by the first end of the first extension rail and a third geometry the second end of the second extension rail.

13. The insulated joint of claim 1, wherein the first extension rail and the second extension rail have a configuration selected from the group consisting of a butt joint, a lap joint, a half lap joint, and a spline joint.

14. A method of isolating a section of a railroad track, comprising the steps of: providing an insulated joint comprised of a first extension rail jointed by a ceramic insert to a second extension rail and having a first free end and a second free end; welding the first free end of the insulated joint to a first railroad track; and welding the second free end of the insulated joint to a second railroad track so that the first railroad track is electrically isolated from the second railroad track.

15. The method of claim 14, further comprising the steps of: providing a second insulated joint comprised of a third extension rail joined by a second ceramic insert to a fourth extension rail and having a third free end and a fourth free end; welding the third free end of the second insulated joint to a third railroad track; and welding the fourth free end of the second insulated joint to a fourth railroad track so that the third railroad track is electrically isolated from the fourth railroad track.1122524429. v1 -12 / 1 / 25

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