Patent Publication Number: US-6705232-B2

Title: Machine for tamping ties of a track

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of Austrian utility model application GM 443/2002, filed Jul. 4, 2002, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates, in general, to a tamping machine. 
     A track maintenance machine of this type is provided for tamping ballast underneath ties of a railroad track, and generally includes a machine frame, extending in a longitudinal direction and supported for mobility on the track by two undercarriages, and a tamping unit and a track lifting unit. 
     U.S. Pat. No. 4,655,142 and U.S. Pat. No. 5,515,788 disclose a tamping machine, with a subframe being arranged between two undercarriages of the machine frame and supported for mobility on the track by a further, separate undercarriage. A frame support connects the subframe to the machine frame in a manner allowing displacement of the subframe in the longitudinal direction. The vertically adjustable tamping unit and track lifting unit are arranged on the subframe between the further undercarriage and the frame support. 
     Tamping machines of this type can travel continuously during working operations, whereby the machine frame, which represents a major part of the total mass of the machine, does not have to be stopped at each tie to be tamped and then accelerated again immediately thereafter. This intermittent advance movement is limited only to the subframe, connected to the machine frame, which carries the working units and is designed for displacement relative to the machine frame. 
     It would be desirable and advantageous to provide an improved tamping machine which allows a tamping of track curve sections in a reliable manner. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a tamping machine for tamping ties of a track includes a machine frame extending in a longitudinal direction and supported for mobility on the track by two undercarriages; a subframe arranged between the said undercarriages and supported for mobility on the track by a further undercarriage; a frame support connecting the subframe to the machine frame in a manner allowing displacement of the subframe in the longitudinal direction, the frame support being mounted on the machine frame for displacement perpendicularly to the longitudinal direction; a transverse drive connected to the frame support and linked to the machine frame; and a vertically adjustable tamping unit and a track lifting unit arranged on the subframe between the further undercarriage and the frame support. 
     A tamping machine having a frame support designed in this way is particularly suited for tamping units which are adapted for tamping several ties of the track simultaneously. Owing to the transverse displaceability of the subframe it is now possible to center the tamping unit with respect to the rail in an optimal manner even in track curves. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing in which: 
     FIG. 1 is a simplified side view of a tamping machine according to the invention; 
     FIG. 2 is an enlarged cross-section along section line II—II of the machine show in FIG. 1; 
     FIG. 3 is an enlarged cross-section of a different variant of a connection of the subframe to the machine frame; 
     FIG. 4 is a schematic top view of the tamping machine; and 
     FIGS. 5 and 6 are respective schematic views in the longitudinal direction, showing the track lifting unit and the frame support in different positions during operation. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
     Turning now to the drawing, and in particular to FIG. 1, there is shown a simplified side view of a tamping machine according to the invention, generally designated by reference numeral  1  and including a machine frame  2  which extends in a longitudinal direction and is equipped at both ends with a respective undercarriage  3 . The machine  1  is provided with a motor  7  and a motive drive  8  and is thereby mobile on a track  6  in an operating direction  12 , with the track  6  composed of ties  4  and rails  5 . A control device  10  is located in a work cabin  9  of the machine  1 . 
     Arranged between the two undercarriages  3  of the machine frame  2  is a subframe  11  which has a front end  15  and a rear end  13  with regard to the operating direction  12 . The rear end  13  is supported on the track  6  by means of a further, separate undercarriage  14  having a separate motive drive  18 . Provided at the front end  15  of the subframe  11  are two frame beams  16 , spaced from one another transversely to the longitudinal direction and arranged in opposite relationship, which are supported on the machine frame  2  in a frame support  17  allowing for longitudinal displacement of the subframe  11  relative to the machine frame  2 . Immediately in front of the further undercarriage  14  of the subframe  11 , a tamping unit  19  is provided which is designed for simultaneously tamping three ties  4  of the track  6 . A track lifting unit  20  precedes the tamping unit  19  in the operating direction  12 , with both, the tamping unit  19  and the track lifting unit  20 , being connected to the subframe  11  for vertical adjustment. 
     As can be seen more clearly in FIG. 2, the frame support  17  includes two glide bearings  21  spaced from one another transversely to the longitudinal direction and connected to one another by a transverse yoke  22 . The glide bearings  21  are each equipped with slide rollers  24  to enable a displacement of the frame beams  16 , supported therein, in the longitudinal direction. The transverse yoke  22 , in turn, is supported for transverse. displacement in slide mounts  23  connected to the machine frame  2 . The frame support  17  is thus displaceable in a transverse direction, indicated by arrow  25 , of the machine  1  relative to the machine frame  2 . To execute the displacement, a transverse drive  26  is provided which is articulated, on the one hand, to the machine frame  2  (or the slide mount  23 ) and, on the other hand, to the transverse yoke  22 . 
     The two frame beams  16 , spaced from one another transversely of the longitudinal direction, are connected to one another by means of a transverse beam  29  to which a push rod  30  is articulated by means of a universally acting joint  31 . The push rod  30  is further connected to the track lifting unit  20 . With regard to the longitudinal or operating direction  12 , the glide bearings  21  are arranged between the transverse beam  29  and the track lifting unit  20  (see FIG.  1 ). 
     FIG. 3 shows an alternative embodiment of a frame support  17 , in which the glide bearings  21 —supporting the frame beams  16 —are mounted for transverse displacement on the transverse yoke  22  which, in turn, is connected at its ends to the machine frame  2 . 
     As can be seen in FIG. 4, the transverse displacement of the frame support  17  and thus also the subframe  11  assures that the tamping unit  19  can be best suited to the course of the track  6  even in a track curve, in order to thereby guarantee an optimum tamping result. 
     In FIGS. 5 and 6, a control device  28  is shown which is connected to the transverse drive  26  and also to a measuring device  27 . The measuring device  27  which is designed as a tensioned cable potentiometer is fastened to the track lifting unit  29  and serves to detect a transverse displacement path, indicated by reference character “a”, of the frame support  17  relative to the track lifting unit  20 . Of course, it is also be possible to use a measuring device  27  which operates in a non-contact manner. 
     As soon as a transverse displacement path “a” is detected by the measuring device  27 , when the machine  1  is situated in a track curve (see FIG.  5 ), the transverse drive  26  is automatically actuated by the control device  28 . This causes a transverse displacement of the subframe  11  until the frame support  17  is again positioned centrally above the track lifting unit  20  (or the track  6  in the region of the frame support  17 ), and the transverse displacement path “a” has the value zero (see FIG.  6 ). 
     While the invention has been illustrated and described as embodied in a machine for tamping ties of a track, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.