Patent Publication Number: US-6981556-B2

Title: Ballast excavating chain

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an arrangement of an excavating chain for conveying ballast of a track bed extending in a first plane, the excavating chain being comprised of a succession of linked chain links and being driven in a second plane inclined with respect to the first plane in an operating stage, and a guide wherein the excavating chain is guided, the guide comprising a transverse guide section positioned in a line of intersection of the first and second planes, in the operating stage, and longitudinal guide sections, the longitudinal guide sections being connected to ends of the transverse guide section by joints having a vertical axis and the guide sections defining a guide channel for the excavating chain, the guide channel being defined by a lower glide track and an upper glide track extending parallel to the second plane and an end glide track extending perpendicularly to the second plane, the end glide track connecting the lower and upper glide tracks. 
   2. Description of the Prior Art 
   U.S. Pat. Nos. 4,014,389 and 4,614,238 and DE 31 51 652, whose disclosures are incorporated herein by way of reference, disclose arrangements of this type, wherein an endless ballast conveyor chain is revolved around a track to excavate the ballast supporting the track and to convey the excavated ballast. The chain is guided by a transverse guide section in contact with the ballast bed during operation and longitudinal guide sections linked to the ends of the transverse guide section by joints. Guide rollers extending coaxially with the axes of the joints deflect the excavating chain from the transverse to the longitudinal guide sections. The pivotal connection between the guide sections is necessary to enable the excavating chain to be slightly displaced relative to the track. This facilitates work in restricted areas of the track. It also makes it possible to elongate the transverse guide section for operation in widened track switches. Since efficient ballast cleaning machines require the ballast excavating chain to be subjected to a tensile force of about 100 kilonewton during excavation, the amply lubricated guide rollers are subject to extremely high loads and must be frequently replaced. 
   SUMMARY OF THE INVENTION 
   It is the primary object of this invention to provide an arrangement of the indicated type whose functioning is improved without interfering with the articulate connection between the guide sections. 
   This and other objects are accomplished in accordance with the invention if the end glide track of the transverse guide section is curved around the joints connecting the ends of the transverse guide section to the adjoining longitudinal guide sections, the curved end glide track of the transverse guide section enclosing an acute dihedral angle α with an imaginary plane of elongation of the end glide track of a respective one of the longitudinal guide sections whereby the excavating chain is deflected solely from the transverse to the longitudinal guide sections by contact with the curved end glide track. 
   This enables the excavating chain to be deflected from the transverse to the longitudinal guide sections solely by frictional contact with the curved end glide track, even under high loads and without interfering with the pivotal connection between the guide sections. The special curvature of the end glide track enables the excavating chain to be led between the transverse guide section and the longitudinal guide sections without any problem even when the angle between the guide sections is increased. This configuration does away with the guide rollers at the joints, which have been considered to be a necessary requirement by those skilled in the art. Due to the extreme loads to which they are subjected, special guide rollers had to be provided at high cost and, in addition, extensive lubrication of the rollers was necessary. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, advantages and features of the present invention will become more apparent from the following detailed description of a now preferred embodiment thereof, taken in conjunction with the accompanying drawing wherein 
       FIG. 1  is a side elevation view of a conventional ballast cleaning machine with a ballast excavating chain; 
       FIG. 2  is a schematic top view of the ballast excavating chain; 
       FIGS. 3 and 4  are enlarged fragmentary views showing the deflection of the ballast excavating chain between the guide sections; 
       FIG. 5  is a fragmentary view showing a guide channel in section; and 
       FIG. 6  is similar to  FIG. 3  and showing a conventional arrangement for deflecting the ballast excavating chain. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawing,  FIG. 1  illustrates ballast cleaning machine  2  with arrangement  1  of an excavating chain for conveying ballast  5  of track bed  3  extending in first plane  8 . During operation, the endless excavating chain is guided around raised track  4 , excavates dirty or encrusted ballast  5 , conveys it to screening apparatus  6  for cleaning, whence the cleaned ballast is returned to the track in a known manner. 
   As shown in  FIGS. 2 and 3 , the ballast excavating chain is comprised of a succession of chain links  15  linked to each other by bolts  14  and is driven in a second plane  7  inclined with respect to first plane  8  in an operating stage. The excavating chain is guided in a guide comprising a transverse guide section  9  positioned in a line of intersection of the first and second planes  7 ,  8 , in the operating stage, and longitudinal guide sections  12 . The longitudinal guide sections are connected to ends of the transverse guide section by joints  10  having vertical axis  21 . The guide sections define guide channel  13  (see  FIG. 5 ) for the excavating chain. The guide channel is defined by lower and upper glide tracks  17 ,  17  extending parallel to second plane  7  and end glide track  18  extending perpendicularly to the second plane, the end glide track  18  connecting the lower and upper glide tracks  17 ,  17 . The glide tracks are of a highly wear-resistant material and are replaceably attached to guide channel  13 . 
   As indicated in phantom lines in  FIG. 2 , transverse guide section  9  may be elongated for work in widened track switches, which changes the angular relationship between transverse guide section  9  and longitudinal guide sections  12 . 
   As best illustrated in  FIGS. 3 and 4 , the end glide track  18  of transverse guide section  9  is arcuately curved at  19  around joints  10  connecting the ends of the transverse guide section to adjoining longitudinal guide sections  12 ,  12 . Curved end glide track  18  of the transverse guide section encloses an acute dihedral angle α, preferably about 45°, with an imaginary plane of elongation of the end glide track of a respective one of the longitudinal guide sections (shown in phantom lines in  FIG. 4 ) whereby the excavating chain is deflected solely from the transverse to the longitudinal guide sections by contact with end glide track  18 . In other words, transverse guide section ends  20  are so curved that the excavating chain comes into contact with end glide track  18  only when the angle between transverse guide section  9  and longitudinal guide sections  12  changes. This is shown in  FIG. 2  in phantom lines. 
   As shown in the embodiment illustrated in  FIG. 3 , end glide track  18  of transverse guide section  9  is arcuately curved about a center defined by vertical axis  21  of joints  10  around which the end guide track is curved. 
   As shown in  FIGS. 3 and 4 , a distance a extending perpendicularly to end glide track  18  of longitudinal guide section  12  adjoining joints  10  is identical to radius r of arcuately curved end glide track  19  of transverse guide section  9 . The arcuately curved end glide track of the transverse guide section forms a circular segment with an angle β of 60°. The arcuately curved end glide track comprises a second arcuately curved end glide track  24  between linear portion  23  of transverse guide section  9  and arcuately curved end glide track  20 , and the second arcuately curved end glide track is arcuately curved about a center positioned on line  26  extending parallel to linear transverse guide section portion  23  and passing through vertical axis  21  of joints  10 . 
   This special configuration of the curved end glide track enables the ballast excavating chain to be deflected solely by frictional contact with the curved end glide track and without the need for a guide roller. In an efficient ballast cleaning machine, the excavating chain is driven, for example, with a tensile force of 110 kilonewton in the direction of the downwardly pointing arrow in  FIG. 3 . 
   This differs from the prior art arrangement  1  shown in  FIG. 6 , in which the excavating chain is deflected by guide roller  27  rotatable about vertical axis  21  of the joint linking the ends of transverse guide section  9  to longitudinal guide sections  12 . The guide roller projects through an opening of the end glide track  18  beyond the glide plane. This has the above-noted disadvantages and, in addition, subjects chain bolts  14  to extreme loads.