Single axle truck for large railroad cars
BACKGROUND OF THE INVENTION 
     The invention relates to railroad car trucks or boogies, especially single axle trucks which are manufactured by National Castings Incorporated of Chicago, Ill. under the trademark UNITRUCK. These single axle trucks are mainly used on trailer carrying flat cars (TOFC) and container carrying flat cars (COFC), or on the end cars of articulated bulk load carrying railroad cars, and are rigidly secured to the structural steel framework of the bottom or under carriage of each one of the cars, closest the trackway along which the cars move. Unlike the more commonly used dual axle truck, this single axle truck has for all practical purposes, no steering capability, since its so-called passive steering is limited to about one and one-half degrees measured from either side of a horizontal axis which is normal to the longitudinal axis of a railroad car, when the car is resting on a horizontal trackway. 
     Current freight cars, up to about fifty feet long with truck centers of about thirty-six feet and equipped with single axle trucks of such limited passive steering, can negotiate the curves of existing trackways in the United States without derailing. However, freight cars are ever increasing, in size, some to about ninety feet, in length, to accommodate larger and heavier loads which railway companies are being asked to transport. To use existing, rigidly connected single axle trucks on such extra long freight cars would be prohibitive and cause derailment of the freight cars, since these trucks do not have the steering capability to negotiate such curves. 
     Thus, railroad car builders and the railway companies are faced with two alternate choices. The first choice is to use a dual axle truck at each end of these extra long freight cars, instead of the single axle truck, but this literally doubles the number of wheels, axles and associated parts required in the make up of a train of freight cars. The second choice is to use a single, dual axle truck between adjacent, extra long freight cars, but this presents a problem when freight cars are uncoupled from one another, since at least one end of an uncoupled freight car becomes unsupported for a period of time. The invention is designed to overcome such problems. 
     Briefly stated, the invention is in a device which is used at either end of a railroad car for supporting the car as it moves along a trackway. The device includes a single axle truck which is firmly secured to a rigid, structural steel subframe which, in turn, is rotatably mounted to the structural steel framework of the under carriage of the freight car at each end of the car. Each one of the rotatable, rigid subframes is provided with one or a pair of steering arms which are designed to engage either a single drawbar or an interlocking, rigid jaw or knuckle type coupler, both of which are used to couple adjacent freight cars together. 
     The steering arms are responsive to movement of the car coupling mechanism as the regular or extra long freight cars move along a curved trackway, and act to correspondingly rotate the rigid subframes to actively steer the single axle trucks along the curved trackway. Moreover, the single axle trucks of adjacent, extra long freight cars are only about ten to fourteen feet apart, as compared to about forty-six to fifty feet apart when such trucks are used adjacent each of the opposing ends of, for example, a sixty foot long railroad car, to provide further assurance that no derailments will occur, since the center distance between the trucks of adjacent railroad cars is important and effects or determines the steering characteristics of the trucks. 
    
    
     DESCRIPTION OF THE DRAWING 
     The following description of the invention will be better understood by having reference to the accompanying, wherein: 
     FIG. 1 is a plan view of a portion of adjacent railroad cars which are mounted on single axle trucks which are made in accordance with the invention, the adjacent railroad cars being coupled together by a single drawbar; 
     FIG. 2 is a section of the railroad cars and trucks viewed from the line 2--2 of FIG. 1; 
     FIG. 3 is a front view of one of the railroad cars and trucks as seen, for example, from the line 3--3 of FIG. 2; 
     FIG. 4 is a plan view of one of the railroad cars and trucks, designed to show the use of, for example, an AAR standard type F coupler, in place of the drawbar; 
     FIG. 5 is a plan view, similar to FIG. 1, but of a second embodiment of the invention; 
     FIG. 6 is a section viewed from the line 6--6 of FIG. 5; 
     FIG. 7 is similar to FIG. 3, but of the second embodiment; and 
     FIG. 8 is similar to FIG. 4, but of the second embodiment with an F coupler. 
     FIG. 8 is similar to FIG. 4, but of the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     With general reference to the drawing for like parts, and particular reference to FIGS. 1-4, there is shown portions of two structural steel under carriages 10 and 11 of a pair of adjacently disposed railroad freight cars 12 and 13, respectively, which, for the purpose of explanation, are assumed to be resting on a horizontal trackway 14, as best seen in FIG. 3. A single drawbar 15 is used to couple the adjacent freight cars 12 and 13 together, but can be replaced, for example, by a pair of similar, interlocked AAR standard type F couplers 16, as seen in FIG. 4. 
     A rigid, cross-braced, rectangular structural steel subframe 17 is pivotally mounted adjacent the opposing ends of each freight car or, as seen in FIG. 1, adjacent the confronting ends 18 and 19 of the coupled freight cars 12 and 13. The rigid subframes 17 are mounted for rotation in the same horizontal plane by any suitable pivot mount 20 which is disposed between each one of the rigid steel subframes 17 and the under carriages 10 and 11 of the freight cars 12 and 13. The rigid subframes 17 rotate below the undercarriages 10 and 11 of the freight cars 12 and 13. 
     Each one of the rigid subframes 17 is provided with four, similar, low friction, load bearing pads 21 which are rectangularly spaced on the rigid subframe 17 and designed to slidably contact adjacent metal plates 22 which are diagonally secured to the underside of the under carriages 10 and 11 of the freight cars 12 and 13, closer the trackway 14, to stabilize the freight cars 12 and 13 in supported relation on the substantially smaller, rigid subframes 17 without impeding limited rotation of the rigid subframes 17 relative to an attached railroad car. Each one of the low friction bearing pads 21 can be atop a pedestal 23, as seen in FIG. 3, or fastened directly to the adjacent under carriage 12 or 13, depending on the particular steel structure of the under carriage. 
     A single axle truck 25 of UNITRUCK design, as more thoroughly explained in U.S. Pat. No. 3,394,662 which, by reference, is made a part of this application, is securely fastened to each one of the rigid subframes 17 for rotating, in unison, with the attached rigid subframe. Briefly, a UNITRUCK single axle truck essentially comprises a pair of AAR standard railroad car wheels 26 and 27 (FIG. 3) which are secured at opposing ends cushioning loads imparted to the single axle 30. 
     A pair of steering arms 31 and 32, as best seen in FIGS. 1 and 2, are provided on each one of the rigid, truck subframes 17 for actively steering the single axle trucks 25 along a curved trackway by rotating the truck subframes 17 as the coupled freight cars travel along the curved trackway. Actually, the steering arms 31 and 32 of each truck subframe 17 are designed to engage the coupling mechanism between adjacent freight cars and respond to any lateral movement of the coupling mechanism caused by lateral curvature of the trackway, to correspondingly rotate the attached truck subframes 17, whereby the attached single axle trucks are actively steered along curves in the trackway. 
     Each pair of steering arms 31 and 32 is secured to a truck subframe 17 at opposing laterally aligned sides 33 and 34 of the truck subframes 17, and converge therefrom in a direction towards an adjacent coupled freight car where they terminate at a pair of laterally spaced, outstanding ends 35 and 36 which, in the embodiment of FIGS. 1-3, are designed to be secured by pins or bolts 37 to downwardly extending, rectangular brackets 38 which are carried by the drawbar 15 between the middle of the drawbar 15 and adjacent confronting ends 18 and 19 of the coupled railroad cars 12 and 13. When the coupling mechanism is a standard type coupler 16, the outstanding ends 35 and 36 of the steering arms 31 and 32 are secured to a similarly shaped, downwardly extending, rectangular bracket 40 which is secured to the adjacent shank 41 of the coupler 16. 
     It should be readily apparent that the embodiment of the invention seen in FIGS. 5-8, is essentially the same as that previously disclosed, except for the steering arms which, in this case, comprise a single rectangular plate or pair of parallel, rectangular plates or arms 45 and 46, depending on the vertical angling required of the drawbar 15 or coupler 16. The steering arms 45 and 46 are centrally secured on, and extend from, the side 47 of each of the truck subframes 17 confronting an adjacent freight car, e.g. car 13 when the arms 45 and 46 extend from the freight car 12. The pair of steering arms 45 and 46 are provided with a pair of laterally spaced, similar, but oppositely disposed, upstanding, confronting triangular shaped brackets 48 and 49 which, as best seen in FIGS. 5 and 8, are designed to straddle enlarged, reinforced shank areas 50 and 51 of the drawbar 15 and coupler 16, respectively. The enlarged shank areas 50 and 51 are adjacent the middle of the drawbar 15 and coupler head 52, respectively. The use of a single plate is tantamount to the use of a single steering arm with a bifurcated end for straddling the shanks of the drawbar or coupler. 
     In the second embodiment of FIGS. 5-8, the drawbar 15 and coupler 16 are pinned to a pivot pin 53 which is used in the pivotal connection 20 between the rigid truck subframes 17 and the under carriages 10 and 11 of the railroad cars 12 and 13. Such an arrangement is precluded when the longer, angularly disposed steering arms 31 and 32 of FIGS. 1-4 are used in combination with a standard size drawbar 15 or coupler 16 which are pinned to the railroad cars 12 and 13 between the pivotal connections 20 and the confronting ends 18 and 19 of the railroad cars 12 and 13, respectively. 
     In either embodiment, the parti-spherical butt ends 54 of the drawbars 15 or couplers 16, as best seen in FIG. 6, can be seated in a matingly shaped cavity 55 which is formed in a front follower 56 that coacts with a device 57 which includes, I) resilient pads for cushioning impact loads, or II) adjusting wedges for taking up slack in the coupling arrangement. 
     Thus, there has been described a unique freight car truck structure which has the capability of using single axle trucks on either normal size freight cars or extra long freight cars. The single axle trucks are each secured to a rigid, rectangular platform or subframe which is actively steered or rotated in corresponding relation to lateral movement of the coupling mechanism between adjacent freight cars, as the cars move along curves of the trackway. The use of this single axle truck at each end of a freight car guarantees support for the car during the uncoupling process. Also, the initial cost of using single axle trucks rather than dual axle trucks, is much less, and the repairs are more economical, since fewer parts are involved.