Patent Abstract:
A method and apparatus for determining the weight of each axle of a plurality of rail cars of a railroad train passing over a selected section of a railroad track. The apparatus embodies a measuring device that, when mounted to the selected section of the railroad track, measures strain induced in a portion of the track as the rail car passes over that portion of the track to produce an electrical output which is precisely proportional to the load imposed on the portion of the track as each axle of the rail car passes over the portion of the track. The measuring device of the interfaces with a remotely located data processing subassembly that receives the output from the strain gauges and precisely determines the axle weight therefrom.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to weight measuring devices. More particularly, the invention concerns a method and apparatus for determining the axle weight of a railroad car by sensing the deflection in portions of the rails of the railroad track over which the railroad car is passing. 
     2. Discussion of the Invention 
     It has been a common practice in the past to use load cells for measuring the weight of various types of articles or materials, such as those contained within tanks and hoppers. Such measurements have typically been accomplished through the use of load cells that are positioned beneath the article to be weighed. However, in order to install the load cells, the article must generally be raised and, in the case of tanks and hoppers, in many instances, the legs of the tank or hopper must be cut or otherwise structurally modified in order to install the load cells. For these reason, the use of conventional load cells for such weighing operations is undesirable and can result in rather substantial expenditures, inconvenience, and time delays in the installation of the load cells. 
     Another prior art approach sometimes used for measuring the weight of articles or materials contained within supporting structures involves the use of strain gauge devices that are mounted within drilled holes formed in the structural members of the supporting structure. In such instance, the strain gauges are adapted to measure the deformation of the hole in the structural member as the load is increased. Typically the installation of such strain gauge devices is difficult and the reliability of such measurements is frequently suspect. 
     To overcome the drawbacks of prior art measuring systems of the character described in the preceding paragraphs, the present inventor developed a novel clamp-on structural strain gauge sensor that can be mounted to dynamic load bearing structures such as sucker-rod type oil well pumps to produce an electrical output proportional to the deflection of the structures. This novel strain gauge measuring apparatus is disclosed in U.S. Pat. No. 5,423,224 issued to the present inventor. Because of the pertinence of this patent to an understanding of the present invention, U.S. Pat. No. 5,423,224 is hereby incorporated by reference as though fully set forth herein. 
     In one embodiment of the invention described in U.S. Pat. No. 5,423,224, the strain measuring apparatus of the invention can be used in conjunction with conventional weighing instrumentation such as a Weigh Meter and has the ability to convert the analog signal from the strain gauge apparatus to a digital signal for processing and correction and then to reconfigure the data back to analog signals for input to the Weigh Meter. 
     As will be better understood from the discussion of which follows, the method and apparatus of the present invention makes use of a somewhat similar strain gauge sensors to those described in U.S. Pat. No. 5,423,224 to precisely determined the weight of each axle of each of the rail cars of a railroad train passing over the section of railroad track to which the strain gauge sensors have been interconnected. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method and apparatus for determining the weight of each axle of a plurality of rail cars of a railroad train passing over a selected section of a railroad track. 
     Another object of the invention is to provide an apparatus of the aforementioned character which embodies a portable measuring device that, when clamped to the selected section of the railroad track, measures strain induced in a portion of the track as the rail car passes over that portion of the track to produce an electrical output which is precisely proportional to the load imposed on the portion of the track as each axle of the rail car passes over the portion of the track. 
     Another object of the invention is to provide an apparatus of the character described that readily interfaces with a remotely located data processing subassembly that receives the output from the strain gauges and precisely determines the axle weight therefrom. 
     Another object of the invention is to provide an apparatus as described in the preceding paragraphs, which is completely portable and can be quickly and easily interconnected with each rail of the railroad track by relatively unskilled workers using conventional tools. 
     Another object of the invention is to provide an apparatus of the class described which includes sensor means for first sensing the proximity of the wheels of the rail car to the sensors that are connected to the track and for then activating the strain gauge sensors to measure deflection in the rails caused by the rail car passing thereover. 
     Yet another object of the invention is to provide a method and apparatus of the character described which enables the precise measurement of each axle of each rail car of the railroad train as the train moves along the track without requiring that the train be stopped at the sensor locations. 
     Still another object of the invention is to provide a method and apparatus of the character described which includes novel calibration means for on site calibration of the apparatus. 
     In summary, the foregoing objects of the invention are achieved through the use of a strain gauge sensors that are removably connected to sections of the rails of the railroad track over which the rail cars pass through the use of proximity sensor means for sensing the proximity of the wheels of a rail car to the strain gauge sensors to produce an electrical output proportional to the deflection of the sections of the rails caused by the passage of the rail car thereover; and through the use of a data processing subassembly, which the electrical output is transmitted to convert the electrical output into the weight of the axle of the rail car passing over selected the sections of the railroad track. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a generally perspective, diagrammatic view of one form of the apparatus of the invention showing one of the two strain gauge measuring devices of the apparatus connected to a section of one of the rails of a railroad track. 
     FIG. 2 is a generally plan view showing the interconnection of the two strain gauge measuring devices of the invention with the rails of a conventional railroad track. 
     FIG. 3 is a generally perspective view of a portion of the strain gauge measuring device that is shown interconnected with the rails of a railroad track in FIGS. 1 and 2. 
     FIG. 4 is a greatly enlarged, generally perspective view of the sensor base of the strain gauge measuring device shown in FIG.  3 . 
     FIG. 5 is a generally diagrammatic view of a the manner of interconnection of strain gauges which form a part of the strain gauge measuring devices of the invention. 
     FIG. 6 is a generally schematic, block diagram of the various electronic components of the apparatus used for measuring deflection of the rails of the railroad track. 
     FIG. 7 is a generally perspective, diagrammatic view, similar to FIG. 1, but showing an alternate form of the apparatus of the invention illustrating one of the two strain gauge measuring devices of the apparatus connected to a section of one of the rails of a railroad track. 
     FIG. 8 is a fragmentary, side elevational view of one form of calibration device of the invention connected to a section of one of the rails of a railroad track. 
     FIG. 9 is a view taken along lines  9 — 9  of FIG.  8 . 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to the drawings and particularly to FIGS. 1,  2  and  3 , one form of the apparatus of the invention for determining the weight of an axle of a railroad car is there illustrated. As depicted in FIGS. 1 and 2, the strain gauge measuring components of the apparatus of the invention, the details of construction of which will presently be described, are designed to be detachably interconnected with the rails “R” of a conventional railroad track “T”. As previously mentioned, the strain gauge measuring, components of the apparatus are similar in construction and operation to those described in U.S. Pat. No. 5,423,224 issued to the present inventor. 
     The apparatus of the present form of the invention comprises four main subsystems, namely a pair of identical deflection collector base subassemblies, generally designated in FIGS. 2 and 3 by the numeral  12 , a pair of identical first sensor means for sensing deflection in a flexure areas of base members  14  which forms a part of the deflection collector base subassemblies, a pair of spaced apart proximity sensor means connected to each of the deflection collector base subassemblies and data processing means for processing the data received from various the sensor means. As best seen in FIG. 3, base member  14  of each of the identical deflection collector base subassemblies of the first and second strain measuring devices comprises an elongated, bar-like member having first and second ends  14   a  and  14   b  and an intermediate portion  14   c.  Forming a part of intermediate portion  14   c  of the base member is a first flexure area  16 . First flexure area  16  is located between two longitudinally, spaced-apart slots  18  and  20 . Slot  18  extends downwardly from surface  14   d  of member  14  while slot  20  extends upwardly from surface  14   e  of member  14 . The function of the first flexure area  16  will presently be described. 
     Provided proximate ends  14   a  and  14   b  of each of the base members  14  are clamping means for clamping the deflection collector base to the lower surface of the base flange “R- 1 ” of one of the rails “R” of a railroad track “T” (FIG.  1 ). The clamping means of the present form of the invention comprises first and second clamping members  21  and  22  respectively which are interconnected with ends  14   a  and  14   b  respectively of each of the base members  14 . Each of the clamping members  21  and  22  include first and second spaced apart jaws  24  and  26  between which the flange “R- 1 ” of one of the rails is closely received. Each jaw  26  is provided with a multiplicity of gripping protuberances or teeth  28  and each is provided with a threaded aperture  30  that is adapted to threadably receive a threaded bolt  32  which here forms a portion of the clamping means of the invention for urging the flanges “R- 1 ” into clamping engagement with teeth  28  of jaws  26 . 
     In the form of the invention illustrated in FIG. 3, the intermediate portion  14   c  of base member  14  is also provided with a second flexure area  34  which comprises a thin wall  36  that is disposed between first and second cut-out portions  38  and  39  formed in the top and bottom walls  14   f  and  14   g  of member  14 . 
     Turning particularly to FIGS. 3 and 4, the first sensor means of the invention for sensing deflection in elongated base member  14  and for providing to the data processing means a deflection signal corresponding to this deflection, comprises a sensor base  40  which is preferably formed from a section of stainless steel plate. Sensor base  40  is provided with a plurality of cutout portions, which define a plurality of thin wall areas to which foil strain gauges are affixed in a manner now to be described. 
     As shown in FIG. 4, sensor base  40  is provided with a central aperture  42  and a pair of apertures  44  and  46 , which are, located on either side of central aperture  42 . Provided in the top and bottom walls  40   a  and  40   b  respectively of base  40  are semi-circular, cutout portions  48  and  50 . These cutout portions form in conjunction with central aperture  42  first and second thin-wall portions  52  and  54  respectively. Formed between apertures  44  and  46  and central aperture  42  are third and fourth thin-wall portions  56  and  58  respectively. The previously identified, circumferentially spaced, strain gauge sensors are interconnected with sensor base  40  in these thin-wall areas. More particularly, a first sensor  60  is affixed proximate thin-wall portion  52  and a second sensor  62  is affixed proximate thin-wall section  54 . Similarly, a sensor  64  is affixed proximate thin-wall section  56  and a sensor  66  is affixed proximate thin-wall section  58  (see also FIG.  3 ). Each of the sensors  60 ,  62 ,  64  and  66 , which comprises a foil strain gauges of a character that is readily commercially available, are bonded to the thin-wall sections of the sensor base with an appropriate adhesive such as an epoxy and are heat cured in position. The foil strain gauges may be platinum, tungsten/nickel, and chromium and are commercially available from various sources including Muse Measurements of San Dimas, Calif. 
     As best seen in FIG. 5, each of the thin-foil strain gauges are then wired in a typical Wheatstone bridge configuration there shown. Thin-wall portions  52 ,  54 ,  56  and  58  of base  40  respond to tension and compression loading across their length. The load varies depending upon the deflection transmitted from the rails “R” through base member  14  to the sensor means or strain gauges  60 ,  62 ,  64 , and  66 . The strain gauges are highly sensitive and the range of force needed to deflect the sensor may be, for example, between zero and approximately 50 pounds. Signal output and deflection is approximately 0.00025 inches of deflection equaling 0.10 MV/V. As illustrated in FIGS. 1 and 4, the sensor itself is wired via a connector  60   a  to a watertight junction box or housing  70 . As shown in FIG. 2, the two sensor subassemblies are operably interconnected by a connector wire  60   b  that passes between the tracks. In similar manner, the data receiving means of the invention is connected to the sensor subassemblies via a connector  72  that runs to junction box  70  (FIG.  1 ). 
     Forming an important aspect of the apparatus of the invention is energizing means that is operably associated with the first sensor means of each of the strain gauge measuring devices for energizing the first sensor means when the wheels of the rail car are positioned over predetermined sections “S” of the rails “R” that are located directly above elongated base members  14 . In the present form of the invention, the energizing means comprises second sensor means for detecting the proximity of rail car wheels “W” to the sections “S” and for then generating and transmitting appropriate signals to activate and deactivate the first sensor means. As illustrated in FIGS. 1 and 2, the second sensor means here comprise a pair of sensors  74  that are positioned on jaws  21  and  20  proximate bolts  32 . As will later be described, in an alternate form of the invention the energizing means takes the form of a single sensor that is affixed to each rail intermediate the gripping jaws (see FIG.  7 ). Various types of readily commercially available proximity sensors well known to those skilled in the art are suitable for use as sensors  74 . By way of non-limiting example, one well-known type of proximity sensor is the eddy current killed oscillator, or ECKO, which utilizes an oscillator that generates a radio frequency, or RF field, at the face of the sensor. Together, the oscillator and the sensor form a tuned circuit, which oscillates at a predetermined frequency. When a metallic object, or target, is moved toward the face of the sensor, eddy currents are established in the target as a result of the oscillating magnetic field. The development of these eddy currents causes the oscillations to diminish in amplitude, or be killed. Typically, an integrator converts the sine wave signal, which is generated by the oscillator, into a DC signal. The DC signal, which varies in amplitude with the amplitude of the oscillator, is sensed by a device, such as a Schmitt trigger, and converted into a digital signal. The digital signal represents the presence or absence of a metallic target in the region of the sensor face. However, it is to be understood that a number of different types of readily commercially available sensors, other than the ECKO sensor can be used to for the present application. Such sensors include inductive type sensors, which are readily commercially available from a number of sources such as the GRANGERS COMPANY. 
     Turning now to FIG. 6, a differential amplifier  80  is shown connected to the bridge configuration  82  shown in FIGS. 5 and 6. The differential amplifier provides gain so that succeeding stage&#39;s noise contributions are negligible and function to filter out high frequency signals from sources such as vibration, which could affect the output, offset set point. Connected to differential amplifier  80  is an output attenuator  88  that attenuates the output from the differential amplifier so that the total gain from the differential amplifier is several times that of the signal out of load sensors. Connected to the output attenuator is an A to D converter  89  that forms a part of the data processing means of the invention. 
     Connected to and powering the Wheatstone bridge  82  is a power supply  90 , which is also readily commercially available. Reference should be made to incorporated by reference U.S. Pat. No. 5,423,224 for a more detailed discussion of the electrical circuitry of the first strain measuring devices and for a more detailed discussion of the operation of these devices. 
     In accordance with the method one form of the invention, a portion of the soil and gravel beneath each of the rails of the railroad track is excavated to form a cavity having a depth of about six inches and width slightly greater than the width of the strain measuring devices. This done, the strain measuring device is interconnected to the flange “R- 1 ” of each of the rails in the manner shown in FIG.  2 . This interconnection step is accomplished by positioning the clamping members  21  and  22  over the rail flanges “R- 1 ” so that a portion of each of the flanges is received between each of the jaws  24  and  26  of the two strain measuring device. This done the then upstanding bolts  32  are tightened to bring the top surfaces  14   g  of each of base members  14  into pressural engagement with the lower surface of each of the flange R- 1  of the rails of the spaced-apart rail “R”. 
     With the two strain measuring devices thusly interconnected with the spaced-apart rails, in the manner shown in figure 21, the devices are interconnected together by means of connector cable  60   b  (FIG.  2 ). Next the operably interconnected strain gauge measuring devices are operably interconnected by means of connector cable  72  with the remotely located data processing means, which is generally designated in FIG. 1 by the numeral  100 . This done the data processing means  100  is energized by means of a suitable power source such as a battery  106  that is interconnected with the data processing means by a cable  108  (FIG.  1 ). Data processing means  100  comprises a suitably programmed, commercially available computer and includes a display means  110  that is operably associated with the computer for displaying information such as axel weight, axel number and the like. 
     With the apparatus interconnected in the manner shown in the drawings and as described in the preceding paragraphs, as each wheel of the railroad car passes along the rails, the proximity of the wheel will first be sensed by the proximity sensors  74  located closest to the direction of approach the wheel “W” and a suitable signal will be transmitted to the data processing means. The data processing means upon receiving the signal from the proximity sensors will appropriately energize the first sensor means. With each of the wheels “W” of one of the rail car axels positioned over the central section of the rails the deflection of the members  14  of each of the first sensor means caused by the weight of the wheels passing over the section will be sensed by the first sensor means and an electrical signal corresponding to the sensed deflection will be transmitted to the data processing means  100 . As the wheel “W” continues to roll along the track, its position will be sensed by the second proximity sensed sensor  74  and a signal will be sent to the data processing means that will result in the appropriate deactivation of the strain gauge measuring devices. 
     In a manner will understood by those skilled in the art, the electrical signals transmitted from the first and second strain measuring devices to the data processing means  100  will be summed and processed by the computer component thereof used to accurately determine from the signal received the weight of the axle of the railroad car carrying the wheels “W” that have passed over the central section “S” of the rails of the railroad track. It is to be noted that because of the strategic positioning, the first and second sensor means of the invention and, due to their cooperation with the data processing means, accurate measurements of the weight of each of the axles of the train can sequentially be made without the necessity of stopping the train. 
     Turning to FIG. 7, the previously mentioned alternate form of the invention is there are shown. This form of the invention is similar in many respects to that previously described and like numerals are used in FIG. 7 to identify like components. The primary difference between this latest embodiment and the earlier described embodiment resides in the character of the energizing means that is operably associated with the first sensor means of each of the strain gauge measuring devices for energizing the first sensor means when the wheels of the rail car are positioned over predetermined sections “S” of the rails “R”. In this latest form of the invention, the energizing means comprises a single sensor  114  that is affixed to each rail intermediate the gripping jaws. As before, sensor  114  can be selected from various types of readily commercially available proximity sensors well known to those skilled in the art. 
     With the apparatus interconnected in the manner shown in FIG. 7, as each wheel of the railroad car passes along the rails, the proximity of each of the wheels will be sensed by the proximity sensors and an appropriate signal will be transmitted to the data processing means. The data processing means upon receiving the signal from the proximity sensors will appropriately energize the first sensor means that are affixed to each of the tracks. With each of the wheels “W” of one of the rail car axles positioned over the central section of the rails, the rails along with members  14  of each of the first sensor means will be deflected by the weight of the wheels passing over the section. Each of the first sensor means will then cause an electrical signal corresponding to the sensed deflection to be transmitted to the data processing means  100  for processing in the manner previously discussed. 
     Turning next to FIGS. 8 and 9 of the drawings, the novel calibration means of the invention for calibrating the first sensor means is there shown connected to one of the pair of rails of the railroad tracks. This important calibration means here comprises a calibration base  120  having first and second ends  120   a  and  120   b  and first and second openings  122   a  and  122   b  formed proximate the first and second ends. Mounted within each of the first and second openings  122   a  and  122   b  is a plurality of strain gauges  124  for measuring the deflection of the calibration base  120 . Strain gauges  124  are of a character well known to those skilled in the art and their installation and operation is well within the skill of the art. 
     Connected to calibration base  120  is pressure imparting means for imparting pressure to the rail and for controllably deflecting calibration base  120 . The pressure imparting means here comprises a turn wheel assembly  125  that is connected to calibration base  120  intermediate first and second openings  122   a  and  122   b.  This important turn wheel assembly here includes a shaft  126  that is threadably connected to calibration base  120  in the manner shown in FIG.  8 . The turn wheel assembly also includes a hand-engaging wheel  128  that is connected to the upper end  126   a  of shaft  126  for imparting rotation to the shaft. 
     The pressure imparting means of this form of the invention also includes a pressure imparting block  130  having a convex lower surface  130   a  that is disposed in engagement with the rails in the manner shown in FIG.  8 . The pressure imparting block  130  is, in turn, operably interconnected with the lower end  126   b  of shaft  126  of the turn wheel assembly by means of a conventional bearing  131 . In order to connect the calibration base to the rails of the railroad track, first and second connector assemblies  132  and  134  are provided proximate the ends of the calibration base. Each of the first and second connector assemblies comprises a connector yoke  136  and a connector cable  138  that extends between the connector yoke and the calibration base for connecting the connector yoke to the calibration base. More particularly, of each of the connector cables  138  includes a flexible body portion of  138   a  that extends through a bore  120   c  provided in each end of calibration base  120 . Flexible body portion  138   a  terminates in a lower portion  138   b  that is affixed one of the connector yokes and terminates in an upper portion of  138   c  that is connected to an anchoring sphere  139 . As best seen in FIG. 9, each of the yokes  136  includes releasably interconnected side components  136   a  and  136   b  so that when the side components are interconnected in the manner shown in FIG. 9, they will cooperate to define an opening  137  that closely circumscribes the upper portion RU of the rail. 
     In using the calibration means of the invention, the apparatus is first connected to the rail in the manner shown in FIGS. 8 and 9. This done, the first sensor means is also connected to the rail by means of the clamping means (see, for example, FIG.  1 ). With the apparatus thusly in place, turning of turn wheel  128  will cause a downward pressure to be exerted on pressure imparting block  130 . As the downward pressure is exerted on block  130 , cables  138  will, of course, be tensioned so that as the rail is deflected, the calibration base  120  along with the sensor member  14  of the first sensor means will also simultaneously be deflected. The extend of deflection of the calibration base can be precisely determined by the strain gauges  124  that are inter connected with suitable external display means by electronic connector  141  (FIG.  8 ). Using the calibration apparatus, it is readily apparent that the amount of force or weight necessary to deflect the rail by a given amount can be readily determined. Once this information is known, the first sensor means of the apparatus of the invention can be calibrated in a manner such that the amount of deflection of the rails by the wheels of the railroad car can be equated to the weight of the railroad car that is causing the deflection of the rail. The aforementioned method of calibration is well understood by those skilled in the art and the calculations necessary to determine the amount of weight necessary to deflect the rails a given amount as measured by the calibration means and the first sensor means can be readily determined by those skilled in the art. 
     Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.

Technology Classification (CPC): 6