Patent Publication Number: US-6668730-B2

Title: Indexer carriage chain tension and dog control system

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to railway car handling or train positioning equipment and, more particularly, to an apparatus for indexing a string of cars through a work station wherein the cars remain coupled. Within this field, the invention further focuses on a drive system for such an indexer which includes automated direct chain tension control which not only enables the chain to be maintained snug in all sprockets and dog carriages to be moved freely with the dogs retracted in a seeking mode in either direction at one force level, but also enables and controls deployment of the dogs and operation of the carriages to move cars in either direction under full load in a second force range. 
     II. Related Art 
     Trains of varying lengths, some containing as many a hundred or more cars of various sizes and shapes, have long been acknowledged as desirable and efficient carriers of bulk raw material such as coal, iron ore, limestone, various finely divided dry bulk agricultural produces including grains, etc., and liquid or dry chemicals. These cars are typically filled from above and, while some may be emptied using a rotary car dumper as in the case of coal or iron ore, most and particularly, those carrying agricultural products, are bottom-emptied over stationary freight handling equipment such as chutes, conveyor handlers or the like. Thus, whether being loaded or unloaded, the cars may have to be precisely positioned under or over dedicated filling or receiving facilities situated at fixed stations along the railroad track. 
     In the discharge operation, a connected train engine roughly positions one end of a string of cars to be unloaded close to the unloading facility. Because train engines are not well suited for indexing or precisely positioning individual cars or even strings of cars along the track, let alone precisely over individual bins, train positioning devices known as railroad car progressors or indexers have been built and operated at fixed stations. Railroad car indexers of the class of interest include at least one car engaging and propelling member or “dog” for engaging at least one railroad car in a string or trip of cars and moving the string a given distance along the railroad track. The car engaging members are most often situated and operated along an auxiliary indexer track or guideway juxtaposed in parallel relation to the railroad track in the fixed receiving facility. Many car indexers of the class are operated utilizing chains and sprockets to move carriages carrying train-engaging dogs which may operate against the railroad car bogey frames. Indexers of the class are shown, for example, in U.S. Pat. Nos. 4,354,792, 5,709,153 and 6,267,059. As can be seen from these examples, the dogs may be operated vertically or horizontally to engage the bogey frames or even couplings of the cars of interest. 
     One long standing problem involved with chain-operated railway car indexer systems involves the inability to maintain continuous proper chain tension. Thus, an initially tight chain, after numerous operations of the indexer system, loosens as parts tend to wear and the chains then become loosely engaged in the sprockets to the point where teeth may be skipped and malfunctions occur. In the past, these problems were addressed by periodically taking the system out of service to remove one or more links from the chain to restore continuity between the chain and all sprockets involved. It would clearly present an advantage in such a system were the chain tension subject to continuous and automated control. It would create an even still further advantage if an automated chain tensioning system could be realized, not only to maintain proper tension in the system in a first or lower force range when the system is utilized to find and engage a railway car, but also in a second or higher force range to deploy dogs to engage and move the cars to the desired position. 
     SUMMARY OF THE INVENTION 
     The present invention enables a desired tension to be maintained directly from the chain of a chain-operated single direction or reversing railway car indexing system by the provision of a tension regulating system which includes a position-adjustable idler sprocket in conjunction with a controlled operating device with capabilities of producing a plurality of force ranges in the chain which encompass both a dog-retracted idling or car-seeking mode and a dog-deploying car-engaging and positioning mode. 
     In one embodiment, this system is utilized in conjunction with a two-position carriage-connecting cylinder in a dual-carriage reversing car indexing system in which opposed pivotally-mounted dogs are connected by a fixed length tension linkage through a self-centering spring cylinder in a manner such that extension of the carriage-connecting cylinder produces a corresponding movement in the linkage connections which, in turn, produces pivotal deployment of the opposed dogs. In another embodiment using horizontally pivoting dogs, the linkage between dogs may consist of a single connecting rod. 
     The pair of consecutive oppositely disposed dog carriages, each carrying an operable car-engaging dog together form a pair of opposite facing or opposed spaced dogs for use in a reversing system, the inward facing carriage ends being connected by the extensible carriage connecting cylinder which is biased to remain in a retracted or collapsed position until the biasing force is overcome. Biasing is preferably accomplished by utilizing a supply of gas-pressurized fluid to maintain the desired force on the cylinder rod end. 
     The system typically operates in a seeking or idling mode with a chain tension force between 3,000 lbs. (1360.5 kg) and 6,000 lbs (2721 kg) which is sufficient to operate the indexer along the indexing guideway while seeking a railway car with dogs retracted or down and the inter-carriage distance at a minimum. When it is desired to deploy the dogs in moving or in engaging a bogey frame, or the like, the chain force can be increased above the 6000 lbs (2721 kg) threshold necessary to extend the carriage connecting cylinder to its full length at which point it becomes a connecting rod and, at the same time, causes the linkage between the dogs to raise or deploy the dogs. 
     The spring cylinder used in some embodiments contains internal springs which bias the dogs in a down or retracted position. The self-centering spring cylinder compression springs, however, further compress as required to allow a dog to be downed or pushed back as by contact with an obstruction bogey frame from behind in one direction while allowing the other dog to remain in its extended or raised position. Conversely, the compression springs also compensate transition for the situation in which the system pressure is reduced so that the dogs try to retract, but a dog is held in the raised or deployed position by an external force as by being at the time up against a bogey frame by allowing the unobstructed dog to retract or drop even though the other dog is prevented from retracting until the bogey frame is cleared. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like numerals depict like parts throughout the same: 
     FIG. 1 depicts a broken schematic plan or layout view of one possible embodiment of a railway car indexer in accordance with the present invention; 
     FIG. 2 is an enlarged schematic drawing partially in phantom depicting a chain tension controlling system in accordance with the invention (shown without the chain); 
     FIG. 3 is a perspective view of a pair of consecutive oppositely disposed dog carriages connected in accordance with one aspect of the present invention; 
     FIGS. 4 a - 4   c  are side views depicting three positions of a type of vertically pivoting dogs connected to operate in accordance with one aspect of the invention; 
     FIGS. 5 a - 5   c  depict an embodiment employing low clearance horizontally pivoting dogs similar to that of FIG. 1; 
     FIG. 6 a  is an enlarged view showing the operation of a spring cylinder linkage as in FIGS. 4 a - 4   c  with one dog held down by a bogey frame and the other, a free dog, deployed; 
     FIG. 6 b  is a view similar to FIG. 6 a  showing the operation of a spring cylinder linkage in the retracted (dogs down), one dog obstructed by a bogey frame; 
     FIG. 7 a  schematically represents a portable hydraulic hand pump for charging oil into the inter-carriage connecting cylinder; 
     FIG. 7 b  is a schematic diagram of a connector cylinder with attached biasing components; 
     FIG. 8 a  is a partial hydraulic schematic for one embodiment of the invention; and 
     FIG. 8 b  is a truth table associated with the schematic diagram of FIG. 8 a.   
    
    
     DETAILED DESCRIPTION 
     It should be kept in mind that one aspect of the present invention enables a desired minimum tension to be maintained in the chain of a chain-operated single direction or reversing railway car indexing system by the provision of a tension regulating system that includes a position-adjustable idler sprocket operable against the chain to create a desired tension. This aspect is particularly suited to systems which systems that over time develop slack in the drive chains which require adjustment by link removal or the like. 
     The system also enables the operation of a variety of indexers which require multiple chain tension ranges during the course of their operation. The reversing indexers that are the subject of the detailed embodiments are presented by way of example only and not limitation. The detailed embodiments involve dual carriage reversing indexer units which include a force-biased two-position inter-carriage linkage and an associated inter-connected force-biased dog operating linkage mechanism. The multiple chain tension ranges enable the indexer to operate in a seeking mode in the first chain tension range in which the dogs are retracted or down and carriages a minimal distance apart while seeking a railcar to move. Thereafter, a high tension range may be used to deploy the dogs and move engaged cars. The use of a sufficiently high minimum tension or first range also enables the entire drive system to maintain proper sprocket engagement for the chain in all phases of operation. 
     FIG. 1 depicts a broken schematic plan view or layout of a possible chain driven reversing indexer using the tension control system of the present invention. The system, generally at  10 , includes a pair of oppositely disposed dog carriages  12 ,  14 , respectively, having outward facing or far ends  16 ,  18  and respective near or inward directed ends  20  and  22  connected by a connector cylinder  24  (shown in greater detail in FIGS. 3-5 c ). 
     Each dog carriage  12 ,  14  carries a horizontally pivoting low-clearance dog member as at  25  and  27 , shown partially deployed in the figure. The carriage and dogs of FIG. 1 represent a type of low clearance train positioner system described in greater detail in U.S. Pat. No. 6,267,059, the details of which are hereby incorporated by reference for any purpose. 
     The far or outward facing ends  16  and  18  of the respective carriages  12  and  14  are connected to opposite ends of a continuous drive chain  26 , shown broken in FIG.  1 . The drive chain  26  is also carried by a main tail idler sprocket  28 , idler sprocket  32 , tension adjusting idler sprocket  30  and a drive sprocket  34  which, in turn, is concentrically connected to a reversible prime mover  36 , which may be a hydraulic motor or any other suitable device. The drive sprocket  34  may be mounted on the output shaft of a planetary gear box or other speed reducer if desired. 
     As is best pictured in the enlarged detail view of FIG. 2, the mounting of idler sprocket  30  is horizontally displaceable (an inward displaced position being pictured in phantom in FIG. 2) relative to sprockets  34  and  32  to adjust chain tension. The adjustment is accomplished by using a linear operator of adjustable force such as a hydraulic cylinder  38  with extendible rod  40 . One such system uses a cylinder with a 4″ (10.76 cm.) bore and 3″ (7.62 cm.) diameter rod and having a 12″ (30.48 cm.) effective stroke. This provides sufficient stroke to allow tension in the chain to be adjusted with the connecting cylinder either fully extended or fully retracted. A typical stroke of the connecting cylinder between full retraction and full extension in an embodiment such as that pictured in FIGS. 4 a - 4   c  is approximately 5″ (12.7 cm.) and in the embodiment shown in FIGS. 5 a - 5   c,  the total stroke is approximately 9″ (22.86 cm.). 
     FIG. 3 depicts a similar connected dual opposed carriage indexer embodiment  50  with carriages  52  and  54 , connecting cylinder  56  and a dog-operating spring cylinder  58  is mounted beneath connecting cylinder  56 . Carriage  52  carries a vertically pivoting dog  60  and carriage  54 , a dog  62 , and outer end chain receiving members are shown at  64  and  66 . The blind end of cylinder  56  and the end of rod  57  are fixed to the respective inward directed ends  68  and  70  of carriages  52  and  54  by conventional clevis and pin arrangements  72  and  74 , as shown, it being noted that the carriage gap or separation span is determined by the state of extension of cylinder rod  57 . 
     An important aspect of the invention further involves the connection between carriage separation and dog deployment as the operation of the dogs is also controlled by carriage separation. This can best be seen in the side elevational views of FIGS. 4 a - 4   c  which depict the low dog vertical embodiment of FIG. 3, the opposed dogs  60  and  62  are connected by a mechanical linkage which operates through the spring cylinder  58  and which includes compression springs  80  and  82  and movable linkage member  84  with piston  85  and linkage member  86  which is fixed relative to the cylinder  58 . FIG. 4 a  depicts the cylinder  56  with rod  57  in a fully collapsed position and the mechanical dog linkage in the fully extended position forcing the dogs  60  and  62  to remain down. In FIG. 4 b,  the rod  57  is shown partially extended and the inter-dog linkage has correspondingly caused the dogs  60  and  62  to assume a partially raised or partially deployed position. FIG. 4 c  depicts the rod  57  of cylinder  56  in the fully extended position and the dogs fully raised. 
     It will be noted that compression springs  80  and  82  enable the dogs  60  and  62  to be biased in a dropped or down position with the cylinder fully retracted as in FIG. 4 a,  but also compress to enable an individual dog  60 ,  62  to be depressed from the fully raised position as by running under a bogey frame without affecting the extended position of the other dog. Conversely, compression springs  80  and  82  also enable a dog to be held up, as by a bogey frame, when the connecting cylinder is in a fully retracted position and a free dog is dropped. 
     These conditions are illustrated in the enlarged detailed views of FIGS. 6 a  and  6   b  in which the springs themselves have been removed for clarity to illustrate rod positioning. The figures depict the car carriage  90  with sets of wheels  92  and  94  and connected by bogey frame members as at  96 . In FIG. 6 a,  the bogey frame member  96  is shown depressing the dog  60  thereby causing the connecting rod  84  to extend with piston  85  compressing spring  80  (not shown). The free dog  62  remains in the fully upright position. Of course, were the rolls reversed, dog  62  likewise could be depressed under the bogey frame member  96  with dog  60  fully extended as the free dog. In FIG. 6 b,  the connecting cylinder  56  and rod  57  are pictured in the fully retracted position, normally associated with downing of the dogs  60  and  62 . However, the dog  60  this time is caught in the upright position against bogey frame member  96  and is able to remain in that position while the free dog  62  drops. After the carriage  90  moves a sufficient distance to the right so that the dog  60  clears the bogey frame member  96 , the dog  60  likewise will drop. These figures illustrate the flexibility of the dog-operating linkage utilizing the spring cylinder. 
     FIGS. 7 a  and  7   b  further illustrate one embodiment of connecting cylinder  56  with rod  57  in schematic form. The system as shown in  7   b  includes a blind end low pressure system and a rod end high pressure system. The blind end low pressure system includes an accumulator  100  having an inert gas precharge  102  over a hydraulic fluid cylinder oil charge at  104  connected by a hose  106  to a hookup at  108  which include an oil input check valve  110 . Likewise, the cylinder end includes a high pressure accumulator  112  which includes an inert gas precharge at  114  and an oil reservoir  116  connected by hose  118  to input inlet  120  and includes input check valve  122 . The gaseous precharges  102  and  114  are typically nitrogen precharges to a desired accumulator pressure. As needed, additional oil may be supplied to the blind end at  110  and the rod end at  122  utilizing a mechanism such as a portable hydraulic hand pump such as is illustrated in the block  130  of FIG. 7 a  and which includes a fluid reservoir  132 , a hand-operated pumping mechanism  134  valved at  136  and  138 , a pressure gauge  140  and a connecting hose  142  suitably valved at  144 . This system can be attached to the cylinder inputs  110  and  122  to charge the blind end and rod end of the cylinder with oil respectively as needed. 
     FIG. 8 a  depicts a hydraulic control schematic for the embodiment of FIGS. 3 and 4 a - 4   c  and the associated truth table as shown in FIG. 8 b . The schematic pictures a hydraulic reservoir at  152  which is connected through a strainer  154  and valve  156  to a suitable hydraulic pump  158  with drive motor  159 . The output pressure of which is controlled by the system as shown in the broken line at  160 . The hydraulic tension cylinder  38  with rod  40  and tension sprocket  30  are also depicted. The carriage drive system is shown generally at  162  connected to the system by hydraulic lines  164  and  166 . A bogey frame location system includes a locator emitter  168  and receiver  170 . Proximity switches are shown at  172 ,  174  and  176 . The operation of these systems, while of interest is well known to those skilled in the art, and since they form no part of the present invention, it is believed, need not be described in greater detail. The system further includes a grease reservoir  180 , an optical chain counting system at  182  and a main pressure gauge  184  with check valve  186 . The hydraulic supply line is shown by  188  and the return or drain line by  190  with return filter  192 . The two-position chain tension system corresponds to the operation of the hydraulic supply pressure at two distinct valves. In the drawing of FIG. 8 a , a supply pressure of 600 psi (42.18 kg/cm 2 ) at RV 2  is used to operate the system with dogs down and a supply pressure of 1600 psi (112.48 kg/cm 2 ) at RV 1  is used to operate the system with dogs up. 
     With respect to the truth table, for ease of identification, valve-operated  00008  is depicted by  194  and operators  00009  and  00010  by  196  and  198  respectively. Likewise, operator  00011  is depicted by  200  and  00012  by  202 . The operation of these is coordinated with the truth table of FIG. 8 b  enabling the operation of the carriage in either direction with the dogs up or down as shown. 
     FIGS. 5 a - 5   c  depict top views of a system similar to that depicted in FIG. 1 with horizontally operating dogs  25  and  27 , which is similar to the system of FIGS. 3 and 4 a - 4   c  employing connecting cylinder  24 . However, this embodiment employs a single linkage member as at  89  to connect the dogs in fixed linkage. This is possible because this type system is normally operated only after the approximate bogey frame is separately detected and located so that the dogs can be deployed or retracted only when both dogs are free. Such a system is described in greater detail in the above cross-referenced U.S. Pat. No. 6,267,059 which is hereby incorporated by reference herein. 
     This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself. For example, the drive chain and sprocket system may be replaced by a system of cable and pulleys.