Automatic revolution counting and data transmission device
This application is a continuation, of application Ser. No. 07/877,877, filed May 4, 1992. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an automatic revolution counting and data transmission device. Specifically, the device is mounted to a wheel for counting the number of rotations of the wheel and transmitting that count to a remote station. 
     BACKGROUND OF THE INVENTION 
     In many industries there exists a need for a device capable of automatically 1) counting revolutions of some type of rotating shaft, 2) storing the count data, and 3) transferring the data into a computer data processing system. The degree of accuracy, or resolution, required various from a count of complete revolutions (low resolution) to a measurement of partial revolutions in very small increments. Once revolutions are counted by such a device, the information describing revolution counts should be transferred in some manner in a machine (computer) readable format for data processing. The invention described herein is capable of counting revolutions, storing the revolution count information, and automatically transmitting revolution count information to a receiver unit which is connected to a computing device. One embodiment of this invention is an electronic hubodometer for measuring revolutions of a wheel on a moving vehicle. Several types of mechanical hubodometers are known in practice. Conceptual proposals for electronic hubodometers are not unknown in technical literature. To date, however, all such devices have depended upon visual or optical (infra-red) readout of the information from the hubodometer. Exemplary hubodometers such as disclosed in U.S. Pat. No. 4,697,278 of Donald Fleischer and U.S. Pat. No. 4,989,222 of William Lutts et al. employ such optical transfer methods. Visual or optical transfer of data from a device mounted in an exposed position on the wheel of a vehicle is subject to continual problems due to buildup of dirt and road grime on the viewing window. The invention described herein overcomes this difficulty through the use of low power radio frequency link to transfer data to a receiving unit. 
     SUMMARY OF THE INVENTION 
     The invention consists of a housing and a small central shaft attached to the housing with the housing being permanently attached to the rotating object for which revolutions are to be counted. Inside the housing is an anti-rotation device with an attached electronic printed circuit board containing all electronic components and circuitry (p.c.) board remains stationary relative to the rotation of the housing around the p.c. board and in relation to the small shaft which passes through the center of the printed circuit board. Counting of rotations by the circuitry on the printed circuit board is accomplished by one of several means depending upon the accuracy required in the count data. For devices requiring count resolutions only in complete revolutions (such as the embodiment as a hubodometer) a magnet is attached to the rotating housing. This magnet then activates a reed switch which the electronic circuitry senses to count revolutions. For devices requiring a higher degree of accuracy, a slotted disk or a gear is attached to the rotating shaft which passes through the center of the p.c. board. An optical scanner is used to detect the slot&#39;s rotational movement or a gear tooth sensor is used to sense rotation of a gear. The number of slots in the rotating disk or the number of gear teeth is varied by the application. A microprocessor chip on the printed circuit board is used to control the logic for counting revolutions, to store the revolution count date in RAM memory, and the control and monitor the radio frequency receiver circuitry and data transmission circuitry, all contained on the p.c. board. 
     Operation of the invention is extremely simple. In its most basic embodiment the device will simply transmit an equipment identification number and a total number of revolutions any time it receives a coded transmission from a separate transmitter/receiver device which would normally be connected to a computer or computer terminal. Since a microprocessor is used within the invention, this processor can be used to maintain and then transmit other information that may be desirable for a particular application. Examples of this information are date and time, revolutions per time increment for various increments of time, and a maximum or minimum number of revolutions per time increment over some selected time period. The transmission range between the device and the separate transmitters/receivers unit can be varied depending upon requirements of a particular application. In the case of the embodiment as a hubodometer, this range is purposely kept small, approximately six feet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and for further details and advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a front view with cover in place; 
     FIG. 2 is a front view partly broken away to show the printed circuit (p.c.) board; 
     FIG. 3 is a front view further broken away showing the anti-rotation device which is behind the p.c. board; 
     FIG. 4 is a transverse sectional view; and 
     FIG. 5 is a systems overview showing the key functional electronic modules; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1-4, the hubodometer consists of an outer metal housing 1 welded or otherwise attached to a threaded central shaft 4. The shaft 4 attaches to the hub of a vehicle either through use of a bracket and bolt (not shown) or by screwing into a threaded receptacle located in the wheel structure itself. As the hub rotates, the shaft 4 and hence the outer metal housing 1 turn along with it. Inside the unit, underneath the plastic cover 2, is an anti-rotation mechanism 12, shown in FIG. 3. This mechanism 12 has mounting holes 5 to which a p.c. board 3 can be connected using spaces 17 and screws 16, shown in FIGS. 2 and 4. 
     The anti-rotation mechanisms 12 is designed to prevent the board 5 from rotating--or &#34;orbiting&#34;--with the central shaft 4 due to angular forces experienced as the shaft 4 spins. To accomplish this goal, a weight 19 is used to vary the center of gravity of the mechanism 12. The weight 19 is attached to a movable rod 20 and then springs 21 are used to maintain the position of the weight 19 near the center of the device. Hence, with no forces acting upon the device, the center of gravity is maintained near the center of the device. When the hub experiences angular forces, however, the weight 19 is thrown outward, thus adjusting the center of gravity to a lower point and preventing any angular acceleration experienced by the outer casing 1 from being transferred to the inner systems of the hub, which are mounted to the anti-rotation mechanism 12 and supported by the central shaft 4 for support in such a way as to minimize rolling friction. The anti-rotation mechanism 12 is kept on the shaft through the use of a retaining cap and a shaft cap 13, both of which are permanently attached to the central shaft 4. This configuration will allow pendulous movement about the shaft, but will prevent rotation. 
     In the embodiment shown, a permanent magnet 14 is attached to the plastic cover 2 (see FIG. 4). As the outer easing 1 rotates, the plastic cover 2 and hence magnet 14 rotate as well. Located at opposite ends of the p.c. board 3 are sensors 9, in this case magnetic reed switches, which detect the presence of the magnet 14 within a small proximity. Hence, a signal can be generated which relates directly to the revolution of the hub unit. Note that although in this case magnets and reed switches were employed, there are several other mechanical and electromagnetic sensors and emitters which could have been used, including, but not limited to, optical sensors, gear tooth sensors, Hall effect devices, contact sensors, and others. 
     After the aforementioned signal is generated, it must be processed into a suitable machine-readable format for use by the microcontroller. The signal must be lengthened, debounced, and output at the correct signal level. The signal conditioner 8 takes care of this task. 
     The heart of this system is a single chip microcontroller 7 (refer to FIG. 5), which includes onboard RAM (Random Access Memory) for storing data and onboard ROM (Read Only Memory) for storing the program. The processor 7 can control power conditioning and distribution; signal conditioning and signal processing functions, as well as control the receiver 11 and the transmitter 10 functions. Through the use of efficient power distribution algorithms, the controller 7 can extend battery life for many years. 
     The controller can be timed by a variety of methods such as RC or LC network, but is usually operated with a crystal. This enables accurate tracking of such variables as time, maximum revolutions in a given time frame, idle time, and many other functions. The controller 7 can then process this data into meaningful signals and broadcast that data to a master receiver unit using the transmitter 10 operating within a radio frequency range well below the aforementioned infrared frequency range disclosed as the operating range for the Fleischer patent above. 
     Full two way communication can be established with the device, thus enabling the unit to be reprogrammed, accept new parameters and instructions, store needed data, and so forth, without the necessity of changing processors, RAM or ROM chips, or otherwise intrusively interfering with the unit. In this way, the unit can be reprogrammed in the field without requiting that it be removed from service, thereby reducing the cost of upgrading the unit&#39;s capabilities at a future time. As stated previously, the processor transmits data to a nearby master unit within range. This transmission takes place in a machine readable format such a Pulse Width Modulation (PWM), Pulse Count Modulation (PCM), analog or digital transmission, or any other scheme capable of creating usable data. 
     The hub can be signalled to transmit its data at the proper time through the use of either a radio frequency beacon or a coded start signal which would be decoded by the processor 7 after being received by the receiver 11. The transmit signal is generated by a master receiver unit set up to receive the incoming data from the hub. The master receiver would itself be triggered to broadcast the beacon by a vehicle detector circuit, direct operator instruction, or other sensors to detect the presence of the hub unit. Upon receipt of the start signal, the hub can transmit an identification code, mileage data, status data, previously stored data, and any other information relative to its ability to collect data, including information from other sensors connected to the processor 7, but being in addition to the standard revolution counters 9. 
     Although preferred embodiments of the invention have been described in the foregoing Detailed Description and illustrated in the accompanying drawings, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions of parts and elements without departing from the spirit of the invention. Accordingly, the present invention is intended to encompass such rearrangements, modifications and substitutions of parts and elements as fall within the spirit of the scope of the invention.