BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention will be described by reference to the drawings in which:
FIG. 1 is perspective view of a preferred embodiment of the insulated rail joint assembly in place on a railway track;
FIG. 2 is an enlarged perspective view of a preferred embodiment of the insulated rail joint assembly;
FIG. 3 is an elevation view of the insulated rail joint assembly of FIG. 2;
FIG. 4 is a sectional view of the insulated rail joint assembly, taken along line 4-4 of FIG. 3;
FIG. 5 is a sectional view of the insulated rail joint assembly, taken along line 5-5 of FIG. 3;
FIG. 6 is a sectional view of the insulated rail joint assembly, taken along line 6-6 of FIG. 3;
FIG. 7 is a sectional view of the insulated rail joint assembly, taken along line 7-7 of FIG. 3;
FIG. 8 is a perspective view of a preferred embodiment of a joint bar of the insulated rail joint assembly;
FIG. 9 is an elevation view of the joint bar of FIG. 8;
FIG. 10 is a sectional view of the joint bar, taken along line 10-10 of FIG. 9;
FIG. 11 is a sectional view of the joint bar, taken along line 11-11 of FIG. 9; and
FIG. 12 is a sectional view of the joint bar, taken along line 12-12 of FIG. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
FIG. 1 shows the preferred embodiment of the insulated rail joint assembly 10 inserted into a standard railway track. The insulated joint assembly comprises two rail segments 14 and one or two joint bars 12, the joint bars 12 being fastened to and extending between the respective web portions 64 of said first and second rail segments 14. The joint bars 12 are installed at the abutment of the rail segments 14, against the web 64, and between the feet 68 and heads 70 of the rail segments 14. Rail segments 14 preferably have thick webs, relative to the pre-determined web thickness of the running rails 16. For example, in North America, standard running rails typically have web thicknesses ranging between ⅝″ and ¾″. Rail segments 14 preferably have web thicknesses of approximately 1.5 to 2.5 times the thickness of the running rails 16. For example, 136 TW rail segments may be used in an insulated joint assembly that is to be used between running rails having a web thickness of ⅝″ to ¾. 136 TW rail segments have a standard web thickness of between 1½″ and 2″, or approximately 1 11/16″. The insulated joint assembly 10 is installed into a section of standard track by any suitable method, such as butt welding, at seams 18.
In order to provide additional support and surface area between a tie and the underlying ballast, ties 22 are wider than the ties 24 in the standard track section. Wide ties 22 are preferably located directly underneath the center of joint assembly 10 and under the ends of joint bars 12. Additional wide ties 22 may be used along the railway if additional support is desired.
FIGS. 2 and 3 illustrate an embodiment of an insulated joint assembly 10 in more detail. At the joint 20, end post 26 separates the ends of rail segments 14. End post 26 may be made of any suitable insulating material, such as a pultruded composite, and is preferably machined to match the profile of rail segments 14. In the preferred embodiment, end post 26 is approximately ¼″ thick, although any suitable thickness which will provide the desired insulating properties may be used.
As best seen in FIG. 4, the joint assembly 10 rests on an insulating tie plate 28, and an insulating rail clip 30 secures the base 66 of joint bar 12. While any suitable fastening system may be used to secure the rail clip 30 and tie plate 28, the preferred embodiment of the assembly uses a resilient floating or elastic fastening system. The fastening system comprises one or more bolts 32 held in place with one or more nuts 34, and further securing one or more flat washers 36 around a double coil spring washer 38. The elastic fastening system allows the rail clip 30 to move with the rail 14 as it deflects under the force of passing train wheels without releasing or loosening the connection between the base of rail 14 and the rail clip 30, thereby resisting impact damage to the joint. Tie plate 28 and rail clip 30 may be made of any suitable insulating material, such as a pultruded composite.
As best shown in FIGS. 5 through 7, joint bars 12 are fastened on either side of abutting rail segments 14 with one or more through fasteners. Joint bar 12 is secured to either side of the web 64 of rail 14, preferably resting on the foot 68 and under the rail head 70, providing a close fit between joint bar 12 and rail 14. A composite reinforcing cloth 46 may be glued between rail 14 and joint bar 12 to provide strength to the joint and to insulate the joint bar from the rail.
The strength of an insulated joint is generally limited by the strength of its glue bond, in that when the glue bond ruptures, then the joint has essentially failed. In addition to the composite reinforcing cloth 46 at the bond line, the glue bond may be reinforced by the use of one or more shear strengtheners to inhibit shear failure along the glue bond line. The shear strengtheners may take the form of shear pins 60 inserted into through holes 62 in joint bars 12 and rail web 64. Shear pins 60 are preferably made of non-conductive material, such as a pultruded plastic. Shear pins 60 may be precisely fitted into holes 62 by any appropriate method, such as by cooling them, thus shrinking the diameter of the shear pin 60 down slightly, and allowing the shear pin 60 to fit into through hole 62. Upon warming to ambient temperature, the shear pins 60 expand to their original size, making them very difficult to remove from holes 62. With the shear pins 60 in place, the shear pins 60 must fail, along with the glue bond, in order for the joint to fail, which substantially increases the strength of the joint. Shear pins 60 are more effective for this purpose than typical fasteners, which do not generally fit closely within the through holes in the joint bar and the rail, and therefore do not strengthen the glue bond in the same way as shear pins.
The strength of the glue bond may also be improved by the use of rails with thicker webs, which tend to have a web 64 more closely corresponding to the shape of the inner abutting surface of the joint bar 12. A closer fit between joint bar 12 and rail web 64 means more bonding surface between the joint bar 12 and rail web 64 which in turn produces a higher strength glue bond which can withstand higher loads.
Joint bars 12 are fastened in place with suitable fasteners. Because of the changing cross section of the joint bars 12, the fastener lengths vary. Long through-bolts 48 surrounded with long insulating bushings 50 are inserted into long through-holes 52 through the joint bars 12 and rail 14. Short through-bolts 54 surrounded with short insulating bushings 56 are inserted into short through-holes 58 through the joint bars 12 and the web 64 of rail 14. Insulated bushings 50, 56 prevents contact between metal through-bolts 48, 54 with the holes 52, 58 in the joint bars 12 and rail 14, thereby preventing electrical shorting.
The strength of a rail may be compromised by putting holes through the rail web 64. Stresses tend to concentrate at holes, causing cracks in the rail web and eventually leading to rail failure. The rail joint assembly of the present invention therefore uses a thicker rail web, which can dissipate stresses more easily than a standard thin web rail, and is therefore less susceptible to failure.
The preferred configuration of a joint bar 12 for use in the rail joint assembly is shown in FIGS. 8-12. Joint bar 12 has a non-uniform cross-section through its length. Preferably, joint bar 12 is thicker at the midsection 40, at or near the rail joint, providing increased strength and support in that area by providing an increased modulus. However, towards the end sections 42 of joint bar 12, less support is necessary, so the joint bar preferably has a somewhat smaller cross-section towards at least one of the opposed portions of the joint bar 12, which are end sections 42. End sections 42 have a length and preferably approximately constant cross-sectional area, but in any case have a maximum cross-sectional area which is smaller than the cross-sectional area of the midsection 40. Tapered sections 44 provide a transition between the joint bar midsection 40 and end sections 42.
Alternatively, it is contemplated that the configuration of joint bar 12 may comprise a step between midsection portion 40 and end sections 42, with no tapered portion, such that the cross-sectional areas of the opposed end sections 42 are substantially constant along the length of the end section. In the further alternative, end sections 42 of joint bar 12 may comprise a continuous taper from the midsection portion 40 to the ends of the joint bar 12.
The relatively thick midsection 40 of joint bar 12 has a higher section modulus than prior art joint bars, and therefore provides increased support for the joint at and around the abutment between the rail segments. The midsection 40 is preferably of constant cross-sectional area, to provide equal support to both sides of the joint. Thick midsection 40 tapers, through tapered sections 44, to thinner end sections 42. This configuration provides maximum support for the joint exactly where such support is required, without unduly increasing the overall weight and bulk of the joint bar 12.
While it will be understood that the relative dimensions of the joint bar may vary depending on the particular railway system in which it is used, with reference to FIG. 8, the midsection 40 commences at approximately ⅓ of the length of the joint bar 12 from either end section 42 and ends at approximately ⅔ of the length of the joint bar 12 from that end section 42. Each tapered section 44 commences at approximately ⅔ of the length of the joint bar 12 from the opposite end. If a stepped or continuous taper configuration is used, the midsection may still comprise ⅓ of the overall length of the joint bar 12, with each of the stepped or tapered end sections 42 comprising another ⅓ of the joint bar 12.
It will be appreciated by those skilled in the art that other variations to the preferred embodiment described herein may be practised without departing from the scope of the invention, such scope being properly defined by the following claims.
Patent Application
20070272762
