Abstract:
A metering pulse transducer for utility meters, including meters for water, gas and electric service, includes a rotor ( 20 ) with five magnetically switchable elements ( 22-26 ) spaced around the axis of rotation ( 21 ), a sensing coil ( 27 ) disposed around the rotor ( 20 ), and two permanent magnets ( 29, 30 ) disposed diametrically across the rotor ( 20 ) and positioned with equal and opposite polarity such that their magnetic fields ( 51, 52 ) extend laterally to reach the path of travel ( 53 ) of the magnetically switchable elements ( 22-26 ), such that when the rotor is rotated, electric pulses are generated as a result of the magnetically switchable elements ( 22-26 ) passing the permanent magnets ( 29, 30 ). A rotor ( 20 ) having five switchable magnetic elements ( 22-26 ) disposed seventy-two degrees ( 72 °) apart generates ten pulses per revolution of the rotor ( 20 ). The rotor ( 20 ) can be used to directly drive a “least significant digit” analog meter dial, or it may be connected to a meter register drive train ( 36, 37 ), or may be used in a turbine-type meter ( 70 ).

Description:
TECHNICAL FIELD 
     The present invention relates to utility meters, such as water meters or meters for gas or electric service. The invention more particularly relates to a transducer for converting mechanical movements, such as revolutions of a metering element to electrical pulses which can be conditioned to become digital signals. 
     DESCRIPTION OF THE BACKGROUND ART 
     An example of a prior metering pulse generator is illustrated and described in Strobel et al., U.S. Pat. No. 4,868,566, issued Sep. 19, 1989, and assigned to the assignee of the present invention. A piezoelectric material is arranged as a thin, elongated layer on a cantilevered spring member. A tooth on a rotating sprocket contacts an extended end of the spring member to produce a bending movement, which is then followed by a rapid return movement. This generates a pulse signal which is amplified by an amplifier positioned on the spring member. 
     In this prior construction, the spring member provided a load on the torque of the meter mechanism. This can have an effect on accuracy of the meter at the low end of the flow measurement range. It would be desirable to reduce such torque loads as much as possible. While technologies such as optics eliminate mechanical loading, they introduce new issues such as batteries and other electrical power sources. 
     There are also known in the art of flow meters generally, a type of pulse generator utilizing magnetically switchable elements. Examples of such pulse generators are shown and described in Onoda et al., U.S. Pat. No. 4,265,127; Bohm et al., U.S. Pat. No. 4,579,008; Jerger et al., U.S. Pat. No. 4,793,192; Merriam, U.S. Pat. No. 5,311,581 and British Patent Specification GB2102129A. Many of these utilize magnetically switchable elements, and a basic pulse generator is disclosed in U.S. Pat. No. 3,780,313. 
     The prior art does not provide a suitable metering pulse transducer for producing pulses that can be conveniently digitized and transmitted in networks for the collection of metering data. Such transducers should be compact and lightweight, and the prior art devices are not suitable in this respect, because they do not most efficiently utilize the principles of generating and sensing signals using the switchable magnetic elements. Such devices should be easy to manufacture and low in cost, and many of the prior art devices are too expensive to manufacture or not sufficiently desirable for utility metering applications intended for the present invention. 
     SUMMARY OF THE INVENTION 
     The invention is embodied in a pulse transducer, which utilizes a compact rotor for carrying a plurality of magnetically switchable elements, and two magnets positioned adjacent the rotor for switching each element four times to produce two pulses in one revolution of a rotor. A compact and efficient sensor is provided for sensing pulses generated by the switching of the magnetically switchable elements as they are moved into and out of the magnetic fields of the two magnets. 
     The rotor assembly of the present invention provides very little drag and consumes very little torque in mechanical drive mechanisms. The rotor can be used to directly drive a least significant digit analog meter dial, or it may be connected to a meter register drive train to provide digitized electrical signals at the same time as mechanical meter movements are transmitted to a mechanical odometer or a mechanical register dial. The invention can also be embodied in a turbine-type flow meter, and other embodiments. 
     As compared with the prior art relating to switchable magnetic elements, the present invention is an improvement over devices which include only a single switchable magnetic element, or a magnetic pickup associated with only a single magnetic element. The prior art does not utilize two magnets to produce a switching of each magnetic element four times to produce two pulses in one revolution of a rotor. 
     The present invention also effectively uses one sensor coil in association with the two magnets and a plurality of switchable magnetic elements in a compact arrangement. 
     In a preferred embodiment of the invention, the number of switchable magnetic elements is five, so that ten electrical pulses are produced for each revolution of the rotor. This corresponds to a decimal number readout device. 
     The prior art devices do not generate ten pulses per revolution of a rotor carrying the magnetic elements. Indeed, in many prior art devices, the magnets may be moved instead of the switchable elements. Unless ten pulses are produced per cycle or revolution, mechanical or electrical conversion is required to produce a decimal pulse count. 
     The invention provides a more compact device than the prior art, making it suitable for use in meter registers which are relatively small instruments. 
     The invention is disclosed in terms of meter registers for use in measuring water consumption, but may also find application in the metering of utilities such as gas or electricity, and or in other types instrumentation in which it is desired to convert mechanical movement to electrical pulses. 
     Other objects and advantages will be apparent to those of ordinary skill in the art from the description of the preferred embodiments which follow. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate examples of the invention. Such examples, however, are not exhaustive of the various embodiments of the invention, and therefore, reference is made to the claims which follow the description for determining the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a first two embodiments of the present invention; 
     FIG. 2A is a top plan view of a third embodiment of the present invention; 
     FIG. 2B is a sectional view taken in the plane indicated by line  2 B— 2 B in FIG. 2A; 
     FIG. 3 is a top plan schematic view of a first variation of the embodiment of FIG. 1; 
     FIG. 4 is a sectional view in elevation of the embodiment of FIG. 3; 
     FIG. 5 is a top plan schematic view of a second variation of the embodiment of FIG. 1; 
     FIG. 6 is a sectional view in elevation of the embodiment of FIG. 5; 
     FIG. 7 is a schematic diagram of the operation of the embodiments of FIGS. 1-6; 
     FIG. 8 is a circuit for conditioning pulses from the device of the present invention to output a 1-millisecond pulse; and 
     FIG. 9 is a longitudinal section view of a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a top plan view of a meter register  10 , which incorporates the present invention in two different embodiments shown in FIGS. 3-4 and FIGS. 5-6, respectively. The meter register  10  includes a dial face  11  with decimal numbers  12  arranged in a circle and a dial hand  13  which rotates around a central axis. An odometer  14  is provided by a plurality of number wheels for respective decimal places as illustrated. 
     In certain meter registers, it is possible to include a plurality of such analog dials, such as formed by elements  11 ,  12  and  13 . One such analog dial is illustrated in FIG. 2A, including dial face  15 , indicia ring  16  and dial hand  17 . A mechanism of the invention is shown in FIG.  2 B. Such a mechanism can be connected to a dial hand  17  as shown in FIG. 2A, or it can be connected internally to a gear mechanism in the meter register  10  of FIG. 1, as shown more particularly in FIGS. 3-6. In either type of meter register (FIG. 1 or FIG.  2 ), the mechanism of the present invention can be coupled to the mechanism for counting the least significant digit of utility consumption. 
     Referring now to FIG. 2B, the invention is provided by a rotor  20  having an axis of rotation  21  and having a plurality of switchable magnetic elements 22-26 equally and angularly spaced by seventy-two degrees (72°) around the axis of rotation  21  (FIG.  2 A). The magnetically switchable elements  22 - 26  have a north-south polarity in a direction generally parallel to the axis of rotation  21 . 
     The magnetically switchable elements  22 - 26  are more particularly of a type disclosed in U.S. Pat. No. 4,247,601, in which a wire of Vicalloy alloy is annealed, work hardened and then cut into shorter lengths to provide magnetic elements having a central core formed along its axis and an outer shell disposed around the central core. The shell and the core are made of material in which the magnetic domains can be switched under the influence of a magnetic field. As a result, the magnetic domains in the shell and the core can have the same magnetic polarity or an opposite magnetic polarity, in each of two directions, providing for four possible magnetic states. The wires are each 0.010 inches in diameter and 0.250 inches in length. 
     A sensor in the form of a coil  27  with 4000 turns of #43 AWG is wound around an annular carrier  28  of synthetic insulating material, sometimes called a “bobbin.” As the switchable magnetic elements are switched a pulse will be induced in the coil  27 , and from there transmitted through leads  38   a ,  38   b.    
     Two permanent magnets  29 ,  30  are located adjacent the rotor  20  (FIG.  2 B), in diametrically opposite positions in the preferred embodiment, with each having a north (N) pole and a south (S) pole, such that their respective magnetic fields extend laterally to a region occupied by the switchable magnetic elements  22 - 26  in the rotor  20  (See FIG.  7 ). The two magnets  29 ,  30  are operated to switch the magnetic elements  22 - 26  as they pass by during rotation of the rotor  20 . 
     A first one of the two permanent magnets  29  is disposed generally parallel to the axis of rotation  21  with its north (N) pole and its south pole (S) oriented in a first direction. A second one of the two permanent magnets  30  is disposed generally parallel to the axis of rotation  21  with its north pole (N) and its south pole (S) oriented in an opposite direction from the first one of the two permanent magnets  29 . Each of the magnets  29 ,  30  has soft iron tabs  29   a ,  29   b , and  30   a ,  30   b , respectively, on top and bottom sides, the magnets  29 ,  30  being made in the form of cubes, and the tabs  29   a ,  29   b ,  30   a  and  30   b  being of a similar height and length, but of much narrower width than the faces of the cubes. The soft iron tabs  29   a ,  29   b , and  30   a ,  30   b  tend to concentrate the flux emanating from the two permanent magnets  29 ,  30 . Although permanent magnets  29 ,  30  are preferred, it would also be possible to use small electromagnets for elements  29  and  30 . 
     When the rotor  21  is rotated, a plurality of electrical pulses are generated in the coil  27  for each revolution of the rotor  21 , the plurality of electrical pulses being twice the number of magnetic elements  22 - 26  in the rotor  21 . The pulses are transmitted through the leads  38   a ,  38   b , seen in FIG. 2A to a circuit seen in FIG.  8 . 
     The rotor  21  has a drive pawl  31  (FIG. 2B) formed in a cavity  32  on an underside to be engaged by various drive mechanisms to be described in relation to FIGS. 3-6. 
     FIGS. 3 and 4 show an arrangement, where the rotor  20  of FIG. 2B is driven by a magnetic pickup  33  having north (N) and south (S) poles. The magnetic pickup  33  rotates with a magnetic driver  34  having north (N) and (S) poles, which rotates with operation of a meter movement in a flow meter  35  in response to flow represented by an arrow in FIG.  4 . This magnetically coupled mechanical movement is coupled through the magnetic pickup  33  to a series of nine gears  36  mounted on respective gear shafts  37  (numbered “1” to “9”) in a gear mechanism, the drive shaft “8” carrying a capstan  39 , which drives a toothed wheel  40 , which in turn drives the least significant wheel  42  in an odometer  41 , formed by a plurality of vertically arranged number wheels  42 . The odometer  41  is preferably one of the type described in U.S. Pat. No. 5,376,776, issued Dec. 27, 1994, and assigned to the assignee of the present invention. 
     A mechanism as described in relation to FIG. 2B is mounted on a rotating shaft  43  to be rotated with magnetic pickup  33 . An electrical output signal is taken from the coil  27  and transmitted to electrical circuitry (not shown) to provide electrical pulses commensurate with the mechanical output of the flow meter  35 . This electrical output in FIGS. 3-4 is said to be unscaled because it is provided before the gear mechanism translates the raw meter movements to the counts of the odometer  41 . 
     FIGS. 5 and 6 show a scaled version of the invention. In the scaled version, a device as shown in FIG. 2B is coupled to the gear shaft  8 , which directly drives the capstan  39 . This is the high resolution or scaled version because the rotor  20  will be rotated by meter movements through the gear mechanism which drives the odometer  41 . The operation of the flow meter  35 , the magnetic driver  34  and the magnetic pickup is the same as described in relation to FIG.  4 . 
     An advantage of the present invention is that the assembly of the rotor  20 , the coil assembly  27 ,  28  and the magnets  29 ,  30  provides very little drag and consumes very little of the torque produced in the mechanical gearing system. 
     FIG. 7 shows more particularly how the domains in one of the magnetic elements  22  are switched as they are rotated past the magnets  29 ,  30 . The dot represents a direction out of the plane of the drawing, while an “x” represents a direction into the plane of the drawing. In position # 1 , as the rotor  20  rotates, element  22  travels along path of travel  53  toward the first magnet  29 , the domains in the core  22   a  of the magnetically switchable elements  22 - 26  (only one of which is shown in FIG. 7) have a polarity represented by an “x”, while the domains in the shell  22   b  have a polarity represented by dots (opposite the polarity of the core) . When the element  22  moves into position # 2 , in the strongest portion of the H field  50  provided by magnet  29  (N polarity), the domains in the shell  22   b  will switch to a like polarity with the domains in the core  22   a  under the strong influence of the H field  50 . 
     The rotor (not shown) will next rotate until the magnetically switchable element  22  reaches position # 3 , away from the H field  50  of the magnet  29  and an approaching the H field  51  of the S-oriented magnet  30 . In position # 3 , the domains in the core  22   a  will switch to a polarity opposite the domains  22  in the shell  22   b . In position # 4 , in the strongest portion of H field  51  of the S-oriented magnet  30 , the domains in the shell  22   b  will switch to a direction the same as the direction of the domains in the core  22   a , but opposite from the direction of second position, due to the opposite polarity of the magnet  30 . When the rotor  20  then rotates back to the position # 1 , away from the H field  51  of the magnet  30  and approaching the N-oriented magnet  29 , the domains in the core  22   a  will switch polarity to a polarity opposite the domains in the shell  22   b.    
     The four magnetic switching events produce two electrically induced pulses for each magnetic element  22 - 26  for each revolution of the rotor  20 . The switching produces pulses of twenty microseconds at the sensor coil  27 . These pulses are transmitted to a pulse conditioning circuit  60  seen in FIG. 8, for translating the pulses into 1-millisecond square wave pulses. 
     When the domains of the core are switched under the influence of one of the magnetic fields of magnets  29  and  30 , they are switched with a sudden and dramatic effect referred to as an avalanche effect. This induces a relatively significant voltage in the sensor coil  27 , on the order of  2  AC volts (0 to peak) and approximately twenty microseconds in pulse width. The pulses will alternate between positive and negative polarity. The coil  27  is electrically connected to a full wave bridge rectifier  61  (FIG.  8 ). A resistor  62  and a capacitor  63  of suitable values are connected across the output of the rectifier  61 , which is also connected to a gate on a N-type FET (field effect transistor)  64 . The capacitor  63  is charged by the output of the rectifier  61 , and then discharges through the NFET  64  to increase the output pulse width to about one millisecond. The NFET  64  provides an open drain connection  65  to a connecting device, which may be a counter with a display, or may be a data collecting device for retransmitting the data over networks. The assignee of the present invention offers such data collecting and retransmitting devices under the trade designations TRACE®, ACCESSplus® and DIALOG®. Each pulse represents a unit or fractional part of a unit of utility consumption. 
     Referring to FIG. 9, the invention can also be applied to a turbine-type flow meter  70 . This meter  70  is mounted in a section of pipe  71 , preferably on the order of one to two inches in diameter, which acts as a meter housing. A sensor coil  72  is disposed around the outside of the pipe or housing  71 , in a carrier  73  that may be made integral with pipe  71  may be mounted on the pipe  71 . The sensor coil  71  has leads (not shown) connecting it to a circuit as previously described in relation to FIG. 8. A pair of magnets  74  and  75  are disposed diametrically across the pipe  71  to produce the H-fields discussed above. 
     A turbine-type rotor  76  is mounted in the pipe  71  in the flow stream. The rotor  76  has blades  78  and a number of switchable magnetic elements  77 , as described for the other embodiments above, preferably five, are mounted in respective blades  78  for rotation past the magnets  74  and  75 . The rotor  76  is mounted by a bushing  79  on a bearing sleeve  80  attached to a shaft  81 . The shaft  81  is has its opposite ends mounted in two hangers  82  and  83  which are attached at certain locations to the interior of the pipe  71 , but have flow passages  84  between fins  85 , so that fluid can flow through the meter. Also shown are an upstream, deflector  86  or hub and a downstream deflector  87  or hub, which are mounted on the shaft  81  and which are typical parts of turbine meters of this type. The flow of fluid through the device causes rotation of the rotor  76 , and ten pulses are produced in the coil  72  for each revolution of the rotor  76 . 
     The above description of several detailed embodiments provides several examples of the invention. For a definition of these and other embodiments which come within the scope of the invention reference is made to the claims which follow.