Patent Publication Number: US-2004040368-A1

Title: Apparatus and method for quantity meter testing

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
     [0001] The present invention is based on and claims priority to U.S. Provisional Patent Application No. 60/408,118, filed on Sep. 4, 2002. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates generally to quantity measurement testing devices, and more particularly, to quickly and accurately testing quantity meters, especially water meters.  
       BACKGROUND OF THE INVENTION  
       [0003] Quantity meters are commonly used to measure a liquid&#39;s volume. Water meters are one example of a quantity meter. The water that is subject to measurement may flow from a source to a residence or business by way of a water service pipeline. The measurement is usually expressed in cubic feet or gallons.  
       [0004] Measuring water volume has a number of practical uses and advantages. Water meters can be used to measure the amount of water usage for a residence or business, thus allowing the water provider to determine the amount of an invoice for a resident or business. Water meters can also be used as an aid in conserving natural resources by measuring and thus, controlling, the volume of water used for irrigation purposes. Also with respect to irrigation, water volume measurement can be used as an aid to prevent overwatering of produce and crops, thus preventing damage to such produce and crops. This damage prevention allows the producer to enjoy a more profitable business.  
       [0005] Since water meters have such important uses, it is highly advantageous to know that these instruments are accurately measuring the volume of water passing through them. Various systems have been employed to measure the accuracy of these instruments. One example of such a prior art system involves forcing water through a quantity meter and measuring the volume of the water as it exits the meter using a scale or volumetric tank.  
       [0006] This method generally involves an operator flowing water into a tank, where the tank has a known volume. More particularly, the tank is drained and sealed or closed. Then the operator ramps the flow rate to the desired test flow rate, and thereafter, allows the water to flow from the source, through a quantity meter being tested, and into the tank. The water flow is then stopped.  
       [0007] In the case of a tank, the volume is read from the tank by means of a sight glass. In the case of a scale, the volume can be measured since the density of water is known at various temperatures. In both cases, manual calculations are required. The weight of the water as indicated by the scale is converted to volume using the known density of the water at the current temperature. In the case of a tank, manual calculations were then performed to determine the volume recorded by the meter.  
       [0008] The scale and tank systems include inherent inaccuracies. The operator must use large volumes of water to overcome inaccuracies in a scale. For example, if a scale has an error of ±1%, the operator must use a larger weight of water in order to compensate for this inaccuracy. If the tank&#39;s meniscus does not accurately show the volume of water in a tank, these inaccuracies are multiplied because the volume measurement is taken at two points: once upon starting water flow, and again upon stopping. These processes are time-consuming, inefficient and are not as accurate as desired.  
       [0009] In order to shorten the amount of testing time, some systems test multiple water meters at the same time, sometimes as few as two water meters in a row, and sometimes as much as one hundred water meters in a row. Such testing systems include multiple pieces, i.e., one test device per water meter aligned in a row. This set-up requires valuable, additional workspace. Moreover, this type of system promotes the practice of an operator waiting until multiple meters are ready and assembled for testing in order to promote efficiency. Increased operator time generally means increased business operating costs. A need exists for a water meter testing device that is comprised of a single unit, and that can accurately test water meters. A need exists for such a testing device that does not require much operator time for each meter test.  
       [0010] Flow rate control is yet another important aspect of quantity meter testing. The flow rate should be constant in order to provide an accurate test. Some prior art testing devices attempt to address flow rate concerns by employing a fairly complex system of variable speed pumps and computer controls. In some cases, a water tower is used. These prior art systems tend to be expensive and require a large amount of space.  
       SUMMARY OF THE INVENTION  
       [0011] The present invention solves the problems set forth above by providing an accurate testing device for quantity water meters that can test multiple meters in a shortened time frame.  
       [0012] The present invention provides an apparatus and method that employs a motor control system coupled to a variable positive displacement water chamber system. Using this apparatus and method, the flow rate of water passing through the meter can be positively controlled. The water meter generates an output signal that is monitored by an electronic sensor. The information from the motor control system is compared with the meter output signal. Both the motor controller and the meter output sensor are of a high speed and accuracy, thereby providing for accurate meter testing.  
       [0013] An advantage of the present invention is to provide more accurate test results using smaller test volumes than current test devices allow. The operator is not required to compensate for errors associated with a scale or a tank&#39;s meniscus as set forth hereinabove. The present invention provides a method whereby only a small quantity of water must be used upon ramping the device to the required speed.  
       [0014] Embodiments of the present invention provide a device that provides a constant flow rate for testing quantity meters. The present invention provides a testing device that includes a servo motor for controlling flow rate. The motor provides a means for displacing water from a water chamber and into a quantity meter, thus providing a constant flow rate. A constant flow rate increases the accuracy of the system, thereby providing reliable results.  
       [0015] Another advantage of the present invention is the automation of the testing device, reducing operator time. The present invention does not require as much operator time as many prior art systems since, in one embodiment of the present invention, the operator is only required to clamp the quantity meter to the test. The test device provides the constant flow rate and performs the necessary calculation. Because of this reduced operator time, businesses are able to reduce operating costs.  
       [0016] Also, the test device of the present invention does not require much valuable workspace. The present invention requires much less space than many prior art systems, thus allowing the space to be used for other purposes.  
       [0017] Additional aspects, advantages and novel features of the embodiments will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by practice of the invention.  
       [0018] Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0019] The drawing figures depict preferred embodiments by way of example, not by way of limitation. In the drawings:  
     [0020]FIG. 1 is a schematic diagram illustrating a side view of one embodiment of the apparatus for testing water meters in the initial test preparation stage.  
     [0021]FIG. 2 is a schematic diagram illustrating a more detailed side view of the apparatus for testing water meters.  
     [0022]FIG. 3 is schematic diagram illustrating a side view of one embodiment of the apparatus for testing water meters in the clamping and purging stage, the next preparatory stage for meter testing.  
     [0023]FIG. 4 is schematic diagram illustrating a side view of one embodiment of the apparatus for testing water meters in the testing stage.  
     [0024]FIG. 5 is a schematic diagram illustrating a top view of one embodiment of the apparatus for testing water meters.  
     [0025]FIG. 6 is schematic diagram illustrating a side view of one embodiment of the apparatus for testing water meters when the test is complete. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0026] The present invention provides an apparatus and method for testing water flow measurement devices with a high degree of accuracy and repeatability.  
     [0027] The present invention is used for testing quantity meters to monitor accuracy and reliability. Although the description will largely relate to water meters, the present invention can be used to test any quantity meter that measures liquid volume. For example, the present invention could also be used to test other liquid quantity meters, e.g., oil quantity meters. The method employed in connection with the test apparatus is described generally in steps A through D.  
     [0028] A. Preparing for Testing. Referring now to FIG. 1, one embodiment of the testing apparatus is illustrated in a side view. The testing apparatus includes a motor control system  10  that is operatively coupled to a variable positive displacement water chamber system  20  that is further operatively coupled to a clamp assembly system  30  that allows for mounting of the test meter  5 . Check valve  310  is an optional device that provides back pressure to promote better meter performance and prevents undesired water drainage. The motor control system  10 , the variable positive displacement water chamber system  20  and the clamp assembly system  30  are mounted on channel  65 . The channel  65  is preferably made of aluminum. Although a single support device in the form of a channel is illustrated in the preferred embodiment, the invention can be practiced with multiple support devices.  
     [0029] B. Securing the Quantity Meter to the Test Device. Referring now to FIG. 2, illustrated is a detailed side view of the test apparatus. Water must be inserted into water cylinder  160  in order for the testing apparatus to operate. Water may be inserted into fill port  185  located on the cylinder end cap  200  of water cylinder  160 . A water supply such as a tube may be used to input water into the fill port  185 . Water cylinder  160  is filled with a liquid and the piston  162  is fully retracted to the illustrated position shown by the cut-out section of FIG. 2.  
     [0030] The test meter  5  may be secured to the single piece-test apparatus via the clamp assembly system  30 . This particular clamp assembly system  30  includes an adapter  220 , a clamp assembly base plate  210 , clamp assembly base plate spacer  240 , clamp assembly slide plate  230 , two washers  250 ,  252 , two shoulder bolts  260 ,  262 , double acting clamp cylinder  280 , cylinder mounting plate  290  and cylinder mounting plate support  300 .  
     [0031] Adapter  220  allows test meters of different sizes to be mounted for testing purposes. When the size of a test meter changes, the size of adapter  220  can also be changed to accommodate larger or smaller test meters. This particular embodiment of the clamp assembly system  30  shown in FIG. 2 is particularly suitable for testing the common water meter sizes of ¾ inch, ⅝ inch, and 1 inch. These measurements generally relate to the size of the outer thread of the opening at the end of the test meter  5 . Although the preferred embodiment is particularly suitable for use with test meters of various specific sizes, the present invention can be adapted for test meters of many sizes.  
     [0032] The operator may insert adapter  220  between the clamp assembly base plate  210  on one end and the clamp assembly slide plate  230  on the other end to accommodate various quantity meter sizes. Clamp assembly base plate  210  is mounted on clamp assembly base plate spacer  240  which is, in turn, mounted on channel  65 . The spacer  240  provides room between test meter  5  and channel  65  so that the test meter  5  is not obstructed by channel  65 . Spacer  240  also substantially aligns the horizontal center of test meter  5  with the horizontal center of water cylinder  160 , thus providing for accurate input of water into test meter  5 .  
     [0033] Clamp assembly slide plate  230  is mounted on a plate  270  preferably formed from an ultrahigh molecular weigh plastic, which is, in turn, mounted on channel  65 . Both the clamp assembly slide plate  230  and the plate  270  have holes bored therethrough so that they can be mounted on channel  65 , two washers  250 ,  252  being insertable through the clamp assembly slide plate  230 . Just below the washers  250 ,  252  shoulder bolts  260 ,  262  secure the washers  250 ,  252 , through plate  270  and clamp assembly slide plate  230 .  
     [0034] Clamp assembly slide plate  230  includes a hole bored therethrough for double acting clamp cylinder  280  so that double acting clamp cylinder  280  can be inserted therethrough. Double acting cylinder  280  is mounted on one end by clamp assembly slide plate and on the other end by cylinder mounting plate  290 . Double acting clamp cylinder  280  operates as an aid in supplying pressure against the test meter  5  by extending so that the smaller test meters are accommodated, and retracting so that larger meters are accommodated. Cylinder mounting plate  290  is supported by cylinder mounting plate support  300  which extends upward from the channel  65 . Cylinder mounting plate support  300  also includes an air cylinder that aids in adjustment for the size of the meter as set forth in more detail with respect to FIG. 5 hereinbelow. Check valve  310  is coupled to a pipe  320  which extends downward to channel  65 .  
     [0035] Referring now to FIG. 3, illustrated is a side view of the testing apparatus during the clamping and purging stage. Clamp cylinder  280  forms a seal  282  between the adapter  220  and test meter  5  so that water does not escape from the test apparatus during the upcoming test process. The inlet valve  190  is opened and the fill valve  192  is opened, thus allowing liquid to flow through the meter  5 . A drain valve (not shown) may be used as an aid in this operation by allowing water to flow and out of the drain and to purge air out of the meter before the test.  
     [0036] C. Testing. Once the test meter has been secured by the clamp assembly system  30  and water has been inserted into fill port  185 , the fill valve  192  is closed.  
     [0037] Referring back to FIG. 2, the servo motor  60  is set to rotate at a specified speed. The servo motor  60  is a part of the motor control system  10  that also includes a motor mount  70  that is mounted on channel  65 . Also included in the motor control system  10  is the output shaft  80  of servo motor  60  coupled to lead screw  100  by coupling  90 . Lead screw  100  is mounted on lead screw bearing block  110 . Lead screw  100  is enclosed in a shaft that is connected to the piston  162  of the water cylinder  160 , thus allowing the motor to control the lead screw&#39;s advancement toward the piston  162 . The motor control system  10  also includes transition block  130  having a linear guide  150  underneath for moving along linear guide track  140 , so that transition block  130  can move toward piston  162 .  
     [0038] The motor  60  may be a DC servomotor. Some standards require quantity meter testing at a particular flow rate, and the motor speed can be controlled such that the flow rate of water is controlled with high accuracy. The motor includes a register for assisting with calculations related to determining the accuracy of the test meter. Water flow can be controlled by the speed of the motor  60  which pushes the lead screw  100  into the water cylinder  160 . The water flows into the test meter  5  at the rate it is pushed through water cylinder  160 , such that a specific flow rate is established through test meter  5 .  
     [0039] Referring now to FIG. 4, as the output shaft  80  of motor  60  turns, the lead screw  100  advances toward the variable positive displacement water chamber system  20 . As lead screw  100  advances, the transition block  130  on which lead screw  100  is mounted, moves along with the lead screw  100 . A lead screw ball nut  120  secures lead screw  100  to transition block  130 .  
     [0040] Transition block  130  moves along with lead screw  100  under control of the motor  60  toward the cylinder  160 , thus accomplishing variable positive water displacement in cylinder  160 . Linear guide  150  has a square bottom with grooves on all four sides of the bottom. Linear guide  150  fits snugly enough within guide track  140  so that the guide  150  does not slip from the guide track  140 , but allows motion that is free enough such that guide  150  can slide freely along track  140 . Guide  150  also has a slippery plastic lining that matches the grooves in track  140 . This assembly allows rotary motion to be translated through lead screw  100  as opposed to rotary motion being translated through transition block  130 .  
     [0041] Near the end of the screw  100  closest to piston  162 , a second guide  156  is mounted on the screw thus aiding in guiding the length of the screw  100  toward variable positive displacement water chamber  20 . This guide  156  is enclosed in a shaft that is connected to the piston  162  of water cylinder  160 . In this view in FIG. 4, the piston  162  has advanced to displace water from cylinder  160 .  
     [0042] Now referring back to FIG. 2, variable positive displacement water chamber system  20  includes a water cylinder  160  having a piston  162  therein. The piston  162  may be a solid cylinder or disk that fits snugly into water cylinder  160  as long as it displaces the water that has been input. Water cylinder  160  is mounted on two cylinder end cap spacers  170 ,  180 , each cylinder end cap spacer being mounted onto channel  65 . Cylinder end cap spacer  170  shown near the right end of water cylinder  160 , as well as cylinder end cap spacer  170  shown near the left end of water cylinder  160 , lend space between the water cylinder  160  and channel  65  so that water cylinder  160  can operate freely without being obstructed by channel  65 .  
     [0043] The end cap spacers  170 ,  180  also allow the horizontal center of cylinder  160  to be substantially horizontally aligned with the horizontal center of test meter  5  on one end and the horizontal center of lead screw  100  on the other end. The spacers  170 ,  180  could be heightened or lowered to accommodate various set-ups depending on the height of other parts used.  
     [0044] Variable positive displacement water chamber system  20  also includes inlet valve  190  that allows water to be filled into cylinder  160  without draining. The inlet valve  190  permits fluid passage from the water cylinder  160  when water is being filled into the cylinder  160  through fill port  185 . Inlet valve  190  prevents water passage from the cylinder  160  during the test process.  
     [0045] Referring now to FIG. 5, illustrated is a top view of the test apparatus in one embodiment of the present invention. Electronic sensor  40  produces a signal that can be read by the register of motor  60  during the test process. The sensor  40  can be an optical sensor, a magnetic sensor or any other device that produces a signal that can be read by the motor  60 . The type of sensor used depends largely upon the type of test meter  5 . The sensor  40  should have the capability to read the test meter  5  without operator assistance. For magnetic test meters, a magnetic sensor may be used in order to read the test meter&#39;s proposed volumetric measurement. For test meters using wheels or impellers that rotate and display measurement, an optical sensor may be used.  
     [0046] The register of motor  60  reads these sensor signals as “pulses” that indicate the rotations of the test meter  5 . When the speed of the motor  60  is established, and thus a constant flow rate of water through cylinder  160 , the register of motor  60  memorizes the location of the piston  162  at the next meter pulse. After a preset number of pulses has been received, the motor&#39;s register determines the position of the piston  162  on the next pulse. The first position of the piston  162  is subtracted from the second position of the piston  162 . When this distance, i.e., the distance the piston  162  has advanced, is compared with the known volume of cylinder  160 , it provides the actual amount of liquid that passed through the test meter  5  from the first pulse to the last pulse. This amount is the test volume. Software may be used to perform the calculation for the test volume. The calculation may also be performed manually and/or using a calculator.  
     [0047] Each pulse from the electronic sensor  40  represents a specific quantity that was measured by the meter  5 . The number of pulses multiplied by the quantity represented by each pulse produces the measured volume. When the test volume is compared to the volume measured by the meter  5 , the accuracy of the volume measured by the meter  5  can be determined. Software may be used to determine the measured volume of the meter; the software may also be used to compare the test volume to the measured volume, thus determining the test meter&#39;s accuracy. The calculation may also be performed manually and/or using a calculator.  
     [0048] Attached to transition block  130  is an extended limit switch  155  that limits the extension of the screw  100  into lead screw bearing block  110 . This feature is a safety measure to stop the screw  100  from retracting into the motor  60 . On the other hand, retracted limit switch  165  limits the extension of lead screw  100  in the direction of water cylinder  160  during the test process, which has now been completed. Vent pressure test port  175  allows the pressure to vent from cylinder  160 .  
     [0049] Four stainless steels rods  195 ,  196 ,  198 , and  199  are located between drain port  205  and fill port  185 . Drain port  205  allows water to drain from water cylinder  160 . Drain port  205  has locking pins  215  secured on the outside of clamp assembly base plate  210  for securing the end of adapter  220  to drain port  205  and to prevent rotation of adapter  220 . Adapter  220  is mounted on the other end by clamp assembly slide plate  230  which also has locking pins  225  attached thereto for securing the adapter  220  to the clamp assembly slide plate  230 , thus preventing rotation of the adapter  220 .  
     [0050] Double acting clamp cylinders  280 ,  283  are mounted on the end closest to water cylinder  160  by gland  235  and gland mounting bracket  245 . Two double acting clamp cylinders  280 ,  283  are mounted on the other end to cylinder mounting plate supports  300 ,  305  which extend back on both sides of check valve  310  from double acting clamp cylinders  280 ,  283 . A “no meter” limit switch  265  operates to limit the extension of clamp cylinder. The “no meter” limit switch  265  is generally located at such a position that the smallest test meter suitable for the testing device is not exceeded by extension of the clamp cylinder  280 .  
     [0051] D. Completing the test. Referring now to FIG. 6, when the test is complete, the inlet valve  190  is closed. Clamp cylinders  280 ,  283  are retracted, thus allowing the meter  5  to be removed. The fill valve  192  is opened and the motor  60  is reversed. The cylinder  160  can now be filled with liquid in preparation for subsequent testing. After the test is complete, the piston  162  is retracted for the fully extended position of FIG. 6 to the retracted position of FIG. 2.  
     [0052] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.  
     [0053] Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.