Patent Application
20250237020
This present disclosure is related to a direct fixation fastener for attaching a rail to a railroad bed.
Bonded direct fixation fasteners (BDFFs) have been used by transit agencies in the United States for many decades. The BDFF design provides a one component solution for the unique needs of the transit railroad systems. Dynamic stiffness of the BDFFs dictates the noise and vibration mitigation performance of the BDFFs. While achieving the desired amount of noise and vibration mitigation, BDFFs must also withstand cyclic wheel loads in diverse environmental conditions for many years. Historically, BDFFs have been made using one grade of rubber and the vertical and lateral stiffness characteristics of BDFFs have been governed by a combination of the geometric details of the design and the properties of the rubber used in the BDFF.
BDFFs with low vertical stiffness are commonly sought to create softer cushions under the rails to provide higher noise and vibration reduction. When the geometrical constraints are set by the end user or track conditions, designers are usually left with softening the rubber element to achieve better noise and vibration reduction. When BDFFs are made softer in the vertical direction, they become softer in the lateral direction as well, which undesirably leads to premature failures under repeated cyclic loading, and also to higher lateral deflection of the rail head.
The majority existing railroad tracks with direct fastening systems reflect a particular footprint, where the fastener is anchored down in two staggered anchor holes. The designers and contractors have the flexibility of selecting a geometry from different design options when a new track is built, but the transit agencies are limited in selecting design options for low vertical stiffness BDFF design during maintenance events or track renewal when the footprint of the fastener and its anchors are set by the original installation.
When low vertical stiffness (− 55,000 lbf/in) of a BDFF is sought for an existing track with fasteners having a standard footprint with a standard stiffness (˜150,000 lbf/in), options are extremely limited. One such option is shown in U.S. Pat. No. 10,428,468, directed to an acoustical direct fixation fastener, but such design is laterally unsymmetrical. Thus, it is desired to provide a low vertical stiffness BDFF for a pre-existing and/or standard footprint where the design's performance is symmetric in the horizontal plane.
In a preferred aspect, the present disclosure comprises a bonded, direct fixation fastener as a supportive structure for a rail on a railroad bed comprising a top member or plate having a center portion having an upper face and a lower face; the top plate defining first and second wall sections each defining an outer perimeter having an outer face defining a lower face section and an upper face section; wherein a first angle between the lower face section and a horizontal surface of the railroad bed is lower than a second angle between the upper face section and the horizontal surface of the railroad bed; a bottom plate or member having first and second anchoring sides connected by first and second elements; wherein the bottom plate or member defines an opening; wherein the bottom plate has first and second wall members each having an interior face; and an elastomeric or rubber portion disposed between the top plate and the bottom plate.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the upper face of the center portion is flat and defines a substantially rectangular or substantially square shape.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the first angle is about 80° and the second angle is about 88°.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the bottom plate or member defines a substantially rectangular shape.
In a further preferred aspect of a bonded, direct fixation fastener of the present disclosure, an interior perimeter of the opening is defined by a plurality linear walls and two semi-circular walls each having a radius of curvature of about 1.75 inches.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the two semi-circular walls has a radius of curvature of about 1.75 inches.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the elastomeric or rubber portion disposed between the top plate and the bottom plate encapsulates all elements of the top plate except for the interior faces of open cylinders for attaching the bonded, direct fixation fastener to a railroad rail and the upper face of the center portion of the top plate and the bottom plate except for a bottom surface of the bottom plate and serrated surfaces around anchoring apertures defined by the bottom plate and the anchoring apertures.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the lower face of the center portion defines first and second beveled edges; wherein each of the first and second beveled edges has an inner portion and an outer portion and wherein a first thickness of the rubber or elastomeric material between the outer portions and a top surface of the bottom plate is greater than a second thickness of the rubber or elastomeric material between the inner portions and the top surface of the bottom plate.
In a further preferred aspect of a bonded, direct fixation fastener of the present disclosure, the first thickness is about 0.85 inches and the second thickness is about 0.63 inches.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, a first thickness of the rubber or elastomeric material between the lower face section of the outer face of the top plate wall and the inner face of the bottom plate wall is less than a second thickness of the rubber or elastomeric material between the upper face section of the outer face of the top plate wall and the inner face of the bottom plate wall.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the first thickness is about 0.88 inches and the second thickness is about 0.98 inches.
In an additional preferred aspect of a bonded, direct fixation fastener of the present disclosure, the bonded, direct fixation fastener produces a vertical spring-rate in the range of about 45,000 lbf/in. to about 65,000 lbf/in.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the top plate has a rail attachment means comprising open cylinders for attaching the bonded, direct fixation fastener to a railroad rail using a clip.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the top plate and the bottom plate comprise one or more of the materials selected from the group of a metal, an alloy, cast steel and ductile iron.
In a further preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the top plate and the bottom plate comprises ductile iron grade 65-45-12.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the first and second elements comprises a beam having a generally trapezoidal cross-section having at least one sharp corner and at least one round corner.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the bottom plate defines a drainage channel from each of the semi-circular walls across the underside of each anchoring side.
In an additional preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the anchoring sides defines an aperture surrounded by a serrated surface for use in attaching the bottom plate or member to a rail bed.
In another preferred aspect of a bonded, direct fixation fastener of the present disclosure, each of the interior faces of the bottom plate is angled at about 75° with respect to horizontal.
In yet another preferred aspect of a bonded, direct fixation fastener of the present disclosure, the elastomeric portion has a hardness in the range of 55 to 65 durometer A or Shore A.
In an additional preferred aspect of a bonded, direct fixation fastener of the present disclosure, the elastomeric portion has a hardness of 60 durometer A or Shore A.
For the present disclosure to be easily understood and readily practiced, the present disclosure will now be described for purposes of illustration and not limitation in connection with the following figures, wherein:
In the following detailed description, reference is made to the accompanying examples and figures that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the inventive subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other embodiments may be utilized and that structural or logical changes may be made without departing from the scope of the inventive subject matter. Such embodiments of the inventive subject matter may be referred to, individually and/or collectively, herein by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single disclosure or inventive concept if more than one is in fact disclosed.
The following description is, therefore, not to be taken in a limited sense, and the scope of the inventive subject matter is defined by the appended claims and their equivalents.
An illustrated preferred embodiment of the low vertical stiffness bonded direct fixation fastener (“LVS BDFF”) 10 of the present disclosure is shown in
Top plate 12 and bottom plate 20 may be made of any durable metal or alloy and are preferably made of cast steel or ductile iron. More preferably, top plate 12 and bottom plate 20 are made from ductile iron grade 65-45-12.
As shown in
An interior perimeter of opening 21 is defined by linear walls 23, 24, 25, 26, 27 and 28 and two semi-circular walls 31 each having a radius of curvature 32 of about 1.75 inches. Bottom plate 20 defines a drainage channel 56 from each of the semi-circular walls 31 across the underside of anchor portion 8 to allow any air, water or other fluid/liquid to drain or be expelled from inside of cavity 21A to the outside environment when the LVS BDFF 10 flexes under load. Preferably, bottom plate or member 20 is adapted to be attached to a rail bed (not shown). For such purpose, each anchoring side 8 preferably defines an aperture 54 surrounded by a serrated surface 55. Bottom plate or member 20 may be attached, using aperture 54, by any means used in the rail industry including spikes, screws, bolts, clips, spring clips, and bolt clamps.
As shown in
As shown in
As shown in
Preferably the LVS BDFF 10 of the present disclosure produces a vertical spring-rate in the range of about 55,000 lbf/in.
In the foregoing Detailed Description, various features are grouped together in a single embodiment to streamline the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the disclosure require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.
This application claims priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63/624,099 filed Jan. 23, 2024, the contents of which are herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63624099 | Jan 2024 | US |
