Abstract:
A tamping blade for a railroad-tamping machine to tamp ballast on a railway line. The tamping blade includes a pad that attaches to a shank of a railroad-tamping machine and is made of hardened steel. A wear-resistant coating covers and protects the surfaces used to tamp the ballast. Wear-resistant inserts are fixed in a leading face of the pad to absorb a large portion of the impact and improve the efficiency of the tamping process. The wear-resistant inserts are positioned to reduce the formation of a wear pattern during use. The method allows for production of a hardened steel pad with a wear-resistant coating and wear-resistant inserts.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a tamping blade for a railroad-tamping machine, and more particularly to a tamping blade having an improved structure to resist wear and a method for producing the tamping blade.  
         [0002]     During use of railroads, ballast supporting the railroads shifts away from the railroad ties. Railroad tamping machines maintain ballast to provide correct alignment and elevation of rails. These tamping machines employ tamping tools that push multiple vibrating blades into the ballast and then towards the rail to compact the ballast supporting the rail. This provides a firm foundation for the rail to support the load of the trains passing over it. This procedure subjects the tamping blade to extremely harsh conditions, as typical ballast includes materials such as rock, wooden cinders, concrete, slag and taconite. Because the ballast also becomes compacted, the tamping blade must break up the ballast in order to repair the ballast. The abrasive nature of the ballast causes tamping blades to wear quickly, necessitating repair or replacement. Each railroad-tamping machine can employ from sixteen to thirty-two tools. Thus, wear and replacement leads to significant expense both in time lost and the cost of replacement blades.  
         [0003]     Many attempts have been made to increase the life of tamping blades by employing wear-resistant materials such as tungsten carbide. For example, U.S. Patent Application No. 2005/0109235 discloses a tamping tool that has a wear-resistant tip inserted into a groove in the end of its blade. Wear-resistant tiles are fixed on the portions of the blade to further protect the blade. Similarly, U.S. Pat. No. 5,261,763 describes a tamping tool having a paddle of carbon steel construction with wear-resistant material brazed to the front, exposed face of the paddle.  
         [0004]     Current tamping blades employing wear-resistant materials are generally made using a soft metal pad. As long as the pad is not exposed to abrasion, and is protected by wear-resistant material, the pads will be fine. But when the wear-resistant material chips off, or the metal pad is otherwise exposed, the soft metal quickly wears away and the tamping blade must be replaced. There is therefore a need for a tamping blade that is less affected by chipping.  
         [0005]     During use, the tamping blade must often break up the ballast. Current tamping blades employ a blunt leading face. The blunt leading face tends to incur impact along the entire length of the leading face and is inefficient for breaking up ballast. Concentrating the impact in a smaller area facilitates breaking up ballast. The stress at the point of impact is greater for a non-blunt blade. There is therefore a need for a tamping blade having a non-blunt leading face capable of withstanding the stress and wear occurring at the point of impact.  
         [0006]     Hardening the metal pad also improves resistance to wear by abrasion. It is therefore desirable to combine wear-resistant material with a hardened metal pad. However, application of wear-resistant material by brazing or welding causes softening of hardened metal, rendering a heat treatment process useless. Using a heat treatment processes after application of a wear-resistant material, such as carbide, would cause the joining material, such as a brazing silver solder to melt off. There is therefore a need for a tamping blade that combines a heat-treated pad with a wear-resistant material and a process to manufacture a tamping blade that combines a heat-treated pad with a wear-resistant material.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention therefore discloses a tamping blade for a railroad-tamping machine to tamp ballast on a railway line. The tamping blade includes a pad that attaches to a shank of a railroad-tamping machine and is made of hardened steel. A wear-resistant coating covers and protects the surfaces used to tamp the ballast. Wear-resistant inserts are fixed in a leading face of the pad and absorb the greatest impact, as well as increase the efficiency of the tamping process. The wear-resistant inserts are positioned to reduce the formation of a wear pattern during use. The method for producing the tamping blade allows for use of a hardened steel pad with a wear-resistant coating and wear-resistant inserts.  
         [0008]     These and further objects and advantages of the present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The illustrative embodiment may best be described by reference to the accompanying drawings where:  
         [0010]      FIG. 1A  shows a perspective view of one embodiment of the tamping blade of the invention.  
         [0011]      FIG. 1B  shows a top view of one embodiment of the leading face of the tamping blade of the invention.  
         [0012]      FIG. 2A  shows a side view of a wear-resistant insert of the invention.  
         [0013]      FIG. 2B  shows a side view of a second embodiment of a wear-resistant insert of the invention.  
         [0014]      FIG. 2C  shows a side view of a third embodiment of a wear-resistant insert of the invention.  
         [0015]      FIG. 3  shows a flow diagram of a method for producing the tamping blade of the invention. 
     
    
       [0016]     All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following description has been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific measurements will likewise be within the skill of the art after the following description has been read and understood. Values provided are representative and are utilized to facilitate the description of the preferred embodiment.  
         [0017]     Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “upper,” “lower,” “side,” “end,”“bottom,” “first,” “second,” “laterally,” “longitudinally,” “row,” “column,” “array,” and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the illustrative embodiment.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     Refer now to  FIG. 1A , which shows a perspective view of one embodiment of the tamping blade  10  of the invention. The tamping blade  10  includes a pad  12 . The pad  12  includes an attachment location  14  where the pad  12  can be attached to a shank of a railroad-tamping machine by welding or other known methods. The welding process should not exceed 350 degrees F. in order to avoid softening the pad  12 . The welding process can be done over a longer period of time in order to avoid too much heat being applied to the pad  12 . The pad  12  further includes a leading face  16  suitable for breaking up ballast and moving and compacting ballast to properly support a rail.  
         [0019]     In order to withstand the harsh environment involved in tamping ballast, the pad  12  is preferably hardened. In the preferred embodiment, the pad  12  comprises a four inch (4″) by four and one-half inch (4½″) by three-fourths inch (¾″) 4140 steel pad having a hardness rating of around fifty-five (55) on a Rockwell C scale. As those skilled in the art will recognize, other conformations of the pad  12  are possible and lie within the spirit and scope of the invention.  
         [0020]     To further protect the surfaces  36  coming into contact with the ballast, the pad  12  includes a wear-resistant coating  18 . In the preferred embodiment, the wear-resistant coating  18  covers the portions of the bordering faces  20 ,  22 ,  24 ,  26  adjacent to the leading face  16 . In this example embodiment, the wear-resistant coating  18  is a continuous coating made of tungsten carbide covering at least one inch (1″) from the edge adjoining the leading face  16  on each of the bordering faces  20 ,  22 ,  24 ,  26 . In this example embodiment, the coating  18  has an average thickness of at least one-eighth of an inch (⅛″). In an alternate embodiment, the wear-resistant coating  18  also covers the leading face  16 .  
         [0021]     The tamping blade  10  further includes a plurality of wear-resistant inserts  28 . In the preferred embodiment, the wear-resistant inserts may be made from tungsten carbide or other hardened material. Prior art tamping blades  10  commonly employ a blunt leading edge. The tamping blade  10  of the invention includes a plurality of hardened inserts  28  having a secured end  30  fixed within the leading face  16  and having a protruding end  32  extending from the leading face  16 .  
         [0022]     As shown in  FIG. 1B , in the preferred embodiment the tamping blade  10  includes a plurality of holes machined into the leading face  16 . In one example embodiment, the plurality of holes  34  are machined to be three-quarters of an inch deep (¾″). The hardened inserts  28  are one inch in length, cylindrical in shape and have a secured end  30  inserted into the plurality of holes  34 , resulting in the protruding end  32  of the hardened insert  28  extending one-quarter of an inch (¼″) from the surface  36  of the leading face  16 . The plurality of holes can be machined to arrange the hardened inserts  28  in a “jogged” pattern. The “jogged” pattern can be used to reduce formation of wear patterns on the tamping blade  10  during use. In this preferred embodiment, ten holes are machined into the leading face  16 , with each hole spaced one-eighth of an inch (⅛″) from the subsequent hole and having an offset of three-sixteenths of an inch ( 3/16″) from a centerline  38 . Alternatively, the plurality of holes  34  can be machined to arrange the hardened inserts  28  in a straight line. Those skilled in the art will recognize that other spacings and patterns can be employed and lie within the spirit and scope of the invention.  
         [0023]     In the preferred embodiment, the plurality of holes  34  have a dimension less than the wear-resistant inserts  28 . This allows attachment of the wear resistant inserts  28  without welding or use of other material. A hammer or arbor press can be used to press fit the wear-resistant inserts  28  within the tamping blade  10 . In this example embodiment, the plurality of holes  34  have a diameter 0.002 inches less than the wear resistant inserts  28 .  
         [0024]     The protruding end  32  of the hardened inserts  28  allows for more efficient and less-wearing breaking up of ballast. The hardened inserts  28  concentrate the force of the tamping blade  10  into a smaller area, allowing for easier breaking up of ballast, thereby requiring less energy. During the horizontal vibration of the tamping blade  10  during the tamping process, the protruding end  32  of the hardened inserts  28  provides a raking effect to shift the ballast into the desired location  14 . In the preferred embodiment, the hardened inserts  28  comprise tungsten carbide or other wear-resistant material, such as hardened D2 steel. As those skilled in the art will recognize, other conformations and dimensions of the hardened inserts  28  on the tamping blade  10  can be employed without departing from the spirit and scope of the invention.  
         [0025]     The protruding end  32  of the hardened insert  28  may be shaped to best suit a desired application as shown in  FIGS. 2A, 2B  and  2 C. In one preferred embodiment, the protruding end  32  has an ovoid shape, as shown in  FIG. 2A . In a second preferred embodiment, the protruding end  32  has a conical shape, as shown in  FIG. 2B . In a third preferred embodiment, the protruding end  32  has a chisel shape, as shown in  FIG. 2C . In one example embodiment, an ovoid shape can be used to break up granite ballast. A conical shape may be employed in hard limestone. A chisel shape can be used in sands and soft limestones.  
         [0026]      FIG. 3  shows a flow diagram of a method for producing the tamping blade  10  of the invention. Prior art tamping blades are hampered by the use of softer metal to provide the base pad  12 . Because the process of soldering wear-resistant material to a base pad  12  would cause softening of the metal used to form the base pad, there is little value to hardening the base pad  12  prior to attachment of a wear-resistant material. After attachment of the wear-resistant material, the pad  12  cannot be subjected to the high heat required for heat treatment, often as high as 1550 degrees Fahrenheit. This heat would result in melting the silver solder or glue used to attach the wear-resistant material.  
         [0027]     In contrast, the method for producing a tamping blade  10  of the present invention allows for use of a wear-resistant material with a hardened pad  12 . The method begins with forming a pad  12  in step  100 . In the preferred embodiment, the pad  12  is formed as a four-inch (4″) by four-and-one-half inch (4½″) by three-fourths inch (¾″) 4140 steel pad.  
         [0028]     Next, the method applies a wear-resistant coating  18  on the portions of bordering faces  20 ,  22 ,  24 ,  26  adjacent to the leading face  16  in step  110 . In this example embodiment, the wear-resistant coating  18  is a continuous coating made of tungsten carbide covering at least one inch (1″) from the edge adjoining the leading face  16  to the bordering faces  20 ,  22 ,  24 ,  26 . In an alternate embodiment, the wear-resistant coating may also cover a portion or all of the leading face  16  in addition to the bordering faces  20 ,  22 ,  24 ,  26 .  
         [0029]     After application of the wear-resistant coating  18 , the method proceeds with machining a plurality of holes  34  in the leading face in step  120 . The plurality of holes  34  can be machined in various patterns to improve the wear resistance of the tamping blade  10 . In one example embodiment, a “jogged” pattern as shown in  FIG. 1  improves resistance against formation of a wear pattern compared with a simple straight-line pattern. In the preferred embodiment, the plurality of holes  34  are machined to have a diameter smaller than the diameter of wear-resistant inserts  28  to be inserted into the leading face  16 .  
         [0030]     The pad is then heat-treated in step  130  to a hardness rating of at least forty on a Rockwell C scale, compared to the usual hardness rating of eighteen of typical pads. In the preferred embodiment, the pad has a hardness rating between forty and sixty. In this example embodiment, a hardness rating of fifty-five can be attained by a typical heat treatment process of heating the pad to a temperature approximately 1500 degrees F., controlled cooling, and tempering by reheating.  
         [0031]     The method for producing a tamping blade  10  then provides for attachment of a wear-resistant insert  28  in each of the plurality of holes  34  in the leading face  16  in step  140 . An arbor press can be used to press fit the wear-resistant inserts  28  into the plurality of holes  34 . Alternatively, a hammer can be used to press fit the wear-resistant  28  inserts into the plurality of holes  34 . In the preferred embodiment, the wear-resistant insert  28  has a protruding end  32  that is shaped according to an intended use.  
         [0032]     As the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.