Abstract:
A child position monitoring device monitors the position of a child by detecting the signal strength of a radio frequency carrier from a transmitter attached to the child. If the signal of the radio frequency carrier is to weak, the child is to far away from the adult who has the child position monitoring device. When this happens, the adult is informed that the child has wandered to far away through the use on an audio tone or through the use of vibrations coming from the device. Once the adult is notified that the child is too far away, the device also has a locating display for indicating the relative direction of the child with respect to the adult. The display uses eight LEDs arranged around an emblem used to represent the position of the adult. The LED which lights up indicates the relative direction of the child.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to location monitoring devices which are used to alert a user when another object or person is located outside a set proximity zone. More specifically, the present invention relates to those location monitoring devices which are compact, portable, and display the relative location of the other person once outside the proximity zone. 
     2. Description of the Prior Art 
     U.S. Pat. No. 4,593,273 issued Jun. 3, 1986 to Bernadine O. Narcisse discloses a proximity monitoring device in which a base unit is alerted whenever a mobile unit is outside of a certain range as set by a threshold detector on the mobile unit. 
     U.S. Pat. No. 3,333,271 issued Jul. 25, 1967 to Stephen J. Robinson et al. discloses a receiver system for measuring the angular direction of propagation of a transmitted frequency relative to the receiver system. 
     U.S. Pat. No. 4,021,807 issued May 3, 1977 to Jerry W. Culpepper et al. discloses a beacon tracking system in which the location and distance of a beacon can be monitored from a police cruiser. 
     U.S. Pat. No. 4,785,291 issued Nov. 15, 1988 to Candy C. Hawthorne discloses a proximity detector for monitoring the proximity of a child. 
     U.S. Pat. No. 4,476,469 issued Oct. 9, 1984 to David R. Lander discloses a locating device for finding commonly lost articles. 
     U.S. Pat. No. 5,021,794 issued Jun. 4, 1991 to Robert A. Lawrence discloses a personal emergency locator network which may be used to locate a lost child. 
     U.S. Pat. No. 4,704,612 issued Nov. 3, 1987 to Boy et al. discloses locating transmitter and receiver system for locating a hunting arrow in which the transmitter is located before it is shot. The receiver uses a directional antenna to determine the relative angular position of the receiver relative to the arrow having the transmitter located therein. 
     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. 
     SUMMARY OF THE INVENTION 
     The child position monitoring and locating device of the present invention monitors the distance a child wanders from device of the present invention. A transmitter is placed on the child which transmits a radio frequency carrier at a predetermined frequency and a predetermined signal strength. The device of the present invention is shaped like a conventional beeper and may be worn by an adult in charge of the child at the time. The device is water-proof and provides an alert signal indication to the adult whenever the child moves outside of a fixed range of the adult. The device allows the adult to set the fixed range within a given range of the device. The alert signal may selectively take the form of an audio signal or a vibration signal. 
     Once the adult is aware that the child is outside of the fixed range, a direction display on the front face of the device allows the adult to determine the relative angular direction of the child when the face of the display is placed in an upward horizontal position. The display has a center position representing the position of the adult using the device as well as a plurality of light emitting diodes (LEDs) surrounding the center position to indicate the direction of the child from the center position when a straight line is drawn from the center position to the LED which is lit. 
     Accordingly, it is a principal object of the invention to provide a small, compact, and easily carried child monitoring device for locating a child which has wandered from the adult using the device. 
     It is another object of the invention to provide the adult with an alert signal indication in the form of an audio signal or a vibration signal whenever the child is located outside of a fixed range from the adult. 
     It is a further object of the invention to of the present invention to provide a child position monitoring and locating device in which the fixed range for alerting the adult may be set by the adult. 
     It is a further object of the present invention to provide a child position monitoring and locating device which is water-proof. 
     It is still a further object of the present invention to provide a visual display of the relative angular position of the child with respect to the adult which is easily interpreted by the adult. 
     It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the present invention. 
     FIG. 2 is a front perspective view of the present invention. 
     FIG. 3 is a partial block diagram of the present invention. 
     FIG. 4 is a partial block diagram of the present invention. 
     FIG. 5 is a partial block diagram of the present invention. 
     FIG. 6 is a diagram illustrating the relationship between the relative angle of the LEDs on the display and angular position of the child with respect to the device of the present invention. 
     FIG. 7 is a decision table which may be used by the microprocessor to decide which LED to light-up. 
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a child position monitoring and locating device 1, herein referred to as a location monitoring device 1, allows an adult using the device 1 to monitor the distance a child wanders from device 1 of the present invention. The location monitoring device 1 has an outer housing H which is compact and portable and has the shape similar to that of the commonly used beepers. The housing H has a front side having a display D for indicating the direction of a locating transmitter (not shown). The locating transmitter could be any of the conventional transmitters used in proximity detectors which transmit radio frequency carriers, such as disclosed by Culpepper et al. The locating transmitter could be pinned onto the child or attached to the child in any conventional manner. 
     Once the location monitoring device 1 detects that the child has wandered to far from the adult having the device, an alert signal indicator is activated to inform the adult of the situation. With the display D in the horizontal position the adult can determine the direction of the child relative to the facing direction of the adult. In the center of the display D is an emblem E which represents the location of the adult. The adult is assumed to be facing in a given reference direction which is illustrated on the display D by a linear direction from the emblem E to the first light generator LED1. The light generator LED1 is preferably a light emitting diode (LED). One of the LEDs (LED1-LED8) lights up to indicate the direction of the child relative to the adult. For example, if LED3 lights up, the child is to the right of the adult. 
     As shown in FIG. 1, the location monitoring device 1 has a display 6 for indicating the maximum distance the child may be located from device 1 without activating the alert signal indicator. This distance may be increased by pressing the up button 5 or decreased by pressing the down button 4. When either the up or down button is pressed, the numeric value illustrated by display 6 is increased or decreased accordingly. Once the numeric value illustrated by the display 6 represents the desired maximum distance the child is allowed to be from the location monitoring device 1, then the enter button 3 is pressed to set the maximum distance the child may be located from the device 1 without activating the alert signal indicator as that distance represented by the numeric value shown on display 6. Display 6 is preferably includes four seven-segment LEDs or four seven-segment liquid crystal displays. 
     As shown in FIG. 1, the location monitoring device 1 also includes a switch 7 to activating an audio signal (e.g., a beep) or a vibration generator in accordance with the preference of the user. The location monitoring device 1 also includes an OFF/ON switch for alternatively connecting and disconnecting all electronic components of the device 1 to a portable power supply, e.g., a battery. As shown in FIG. 2, the location monitoring device also includes a clip 8 for connecting the device 1 to an article of clothing to the adult user of the device 1. 
     The location monitoring device 1 utilizes an orthogonal antenna array pair for receiving the radio frequency carrier of the locating transmitter as shown by Robinson et al., made of record and incorporated herein by reference (see FIG. 3 of Robinson et al.). As shown in FIG. 4 of Robinson et al., each of the antenna arrays have successive antenna pairs proceeding from the inner most pair, e.g., W 1  and X 1 , to the outer most pair most pair, e.g. W 4  and X 4 , connected to a unique phase discriminator, wherein each of successive antenna pairs of each antenna array has all other prior antenna pairs of the same antenna array located therebetween. Each phase discriminator is in turn connected to a logic circuit, and the four logic circuits connected an antenna array produces one Cartisean coordinate while the other four produce another Cartesian coordinate. Once the Cartisean coordinates are obtained, the angle of propagation of the radio frequency carrier can be obtained using simple trigonometry. 
     In the present invention, it is desirable not only to know the angle of propagation of the radio frequency carrier, but also the signal strength of the radio frequency carrier. A phase discriminator circuit which can also determine signal strength is shown in Culpepper et al., made of record and incorporated herein by reference. As shown in FIG. 7 of Culpepper et al., a phase discriminator circuit uses two triple conversion channels 104 and 106, each one feed with a particular antenna signal and a plurality of oscillator signals to down shift the signals coming from the antennas. Each of the triple conversion channels 104 and 106 have their outputs feed to a phase detector to produce the output of the phase discriminator of Culpepper et al. As disclosed by Culpepper et al., an automatic gain control (AGC) signal of a triple conversion channel is feed to a distance indicator 146 to provide a distance indication in accordance with signal strength, i.e., the average voltage level, of the AGC signal. 
     As shown in FIG. 3 of the present invention, a phase discriminator 10 utilizes the advantages of an AGC signal to produce a signal whose signal strength is indicative of the distance the locating transmitter is located from the location monitoring device. Since the locating transmitter transmits the radio frequency carrier at a predetermined signal strength, the distance of the locating transmitter can be determined. More specifically, a phase discriminator 10 is shown utilizing two triple conversion channels 18 and 20. One signal from an antenna of an antenna pair is feed to triple conversion channel 18, while the other antenna of that pair is feed to triple conversion channel 20. Oscillator circuitry 19 has three oscillator signal generators to down shift the frequency of the received radio frequency carrier. The outputs of triple conversion channels 18 and 20 are feed to phase detector 21 to produce an output of the phase discriminator 10. 
     As shown in FIG. 3 of the present invention, a line connection 12 is connected to the AGC output triple conversion channel 18. Line connection 12 is used to provide a signal strength indication of the radio frequency carrier as discussed above to the threshold detector 13. The threshold detector 13 compares the signal strength of the AGC output from line connection 12 with a predetermined signal strength from a variable resistor 14. Variable resistor 14 is adjustable to provide a variable predetermined signal strength to the threshold detector 13. If the AGC signal strength is less than the predetermined signal strength, then threshold detector 13 produces an alert signal A at its output. The alert signal A is selective delivered to one of the alert signal indicators including an audio generator 16 or a vibration device 17 in accordance with the setting of a switch 7, as discussed above. 
     It is only necessary for one of the discriminator circuits of one of the antenna array pairs to have a line connection 12 to produce the AGC signal at its output. For example, FIG. 4 of the present invention illustrates that the line connection 12 is connected to the phase discriminator circuit of the antenna pair W 1  and X 1 . All other phase discriminator circuits would be lacking the connection 12. 
     As shown in FIG. 5 of the present invention, the outputs of the phase discriminator circuits are provided to a microprocessor controller 22 to determine the propagation angle of the radio frequency carrier signal. Given a particular propagation angle, the microprocessor controller 22 provides the LED driver 23 with display digital control signals 15. For example, the display digital control signals may be made from eight binary digital signals D1-D8. If D1 is a one then LED1 is lit up; otherwise, it is not lit up. Likewise, if D2 is a one the LED2 is lit up; otherwise it is not lit up. This is true for all of the LEDs. 
     As shown in FIG. 6, for each unique propagation angle detected, a particular set of display digital control signals 15 is provided to the LED driver 23 by microprocessor controller 22. As shown in FIG. 7, and as discussed above, the adult user is assumed to be facing in a given reference direction which is illustrated on the display D by a linear direction from the emblem E to the first light generator LED1. 
     If the location monitoring device is used as disclosed above in the preferred embodiment, if the child is located to the exactly to the right of the adult then the propagation angle would be 90 degrees and the LED3 would be lit. If the child is approximately to the right of the adult, then the propagation angle is approximately 90 degrees. The LED3 would still light up if the propagation angle of the radio frequency carrier is within a given predetermined tolerance of 90 degrees. In this manner, the LED which is closest to representing the propagation angle as illustrated by the relationship of propagation angle and LED position as shown in FIG. 7, is the LED which is lit up. As shown in FIG. 6, if the propagation angle is between two LEDs within another given tolerance, both LEDs may be lit up. 
     As shown in FIG. 6, and discussed above, there exists a one to one correspondence between any given detected propagation angle and the display digital control signals 15. The data of FIG. 6 may be stored in a memory location of the microprocessor controller 22. Part of the memory data allows for the actuation of one of the LEDs, while other parts of the memory data allow for the actuation of two LEDs. For example, if the propagation angle is 341 degrees to 19 degrees only LED1 is lit, while if the angle is 26 degrees to 64 degrees only LED2 is lit, etc. However, if the propagation angle is 20 degrees to 25 degrees both LED1 and LED2 are lit, while if the angle is 65 degrees to 70 degrees both LED2 and LED3 are lit, etc. 
     The microprocessor controller 22 also controls the display 6 and receives inputs from the buttons 3-5. This is illustrated by user input/output interface 24 which interfaces with the microprocessor controller 22 via digital signals 26. The microprocessor controls the variable resistor 14 in accordance with digital signals 26. The alert signal A is also provided to the microprocessor controller 22 when generated by the threshold detector 13 to enable the microprocessor controller 22 to provide display digital control signals 15 to the LED driver 23 to light up one or more of the LEDs. 
     While a particular preferred embodiment has been presented, it is to be understood that the scope of the invention includes all modifications thereto within the spirit of the invention. For example, other light generators known in the art could be substituted for the LEDs. Further, while Robinson et al. disclose that the propagation angle can take on positive or negative values, e.g., ±180 degrees, it is simple convert this angle to a positive angle only if it were negative. For example, -90 degrees is equal to 270 degrees. 
     It is to be understood that the present invention is not limited to the sole embodiment described above, but encompasses any and all embodiments within the scope of the following claims.