Abstract:
This invention is an apparatus and method for determining the velocity of a projectile. A light curtain unit ( 20 ) creates two light curtains ( 46 ) ( 48 ) and two sensing planes ( 50 ) ( 52 ). The projectile causes light from the light curtain ( 46 ) ( 48 ) to be reflected into the detectors ( 22   a ) and ( 24   a ) of the sensing planes ( 50 ) ( 52 ). The time for a projectile to pass through one sensing plane to the other is measured and calculated for display by the Display Unit ( 10 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       FEDERALLY SPONSORED RESEARCH  
       [0002]     Not Applicable  
       SEQUENCE LISTING OR PROGRAM  
       [0003]     Not Applicable  
       BACKGROUND OF THE INVENTION-FIELD OF INVENTION  
       [0004]     This invention relates to an apparatus for determining a projectile&#39;s velocity, specifically to projectiles utilized in general sports and game play.  
       BACKGROUND OF THE INVENTION  
       [0005]     In sports and games involving projectiles such as baseball, tennis, golf etc., any increase in the velocity of the projectile is highly desired. Thereafter inventors have created several types of training aids to provide velocity indications to the user.  
         [0006]     U.S. Pat. No. 6,416,747 to Hardy (2002) discloses an infrared photodetector apparatus for measuring projectile velocity; however the apparatus is bulky, hard to setup and expensive to manufacture. U.S. Pat. No. 5,602,638 to Boulware (1997) discloses a system that is less bulky but still expensive to manufacture more over this system requires the size of the projectile to be known as the speed determination is based on the diameter of the projectile. Other patents such as U.S. Pat. No. 5,230,505 also discloses systems to measure a projectiles velocity but as a whole they are mainly applicable to pitching type games and sports such as baseball or softball and are impractical to modify for other games and sports such as tennis or golf etc.  
       BACKGROUND OF THE INVENTION-OBJECTS AND ADVANTAGES  
       [0007]     Accordingly, several objects and advantages of my invention are: 
        (a) to provide a training aid which will provide accurate indication of a projectile&#39;s velocity;     (b) to provide a training aid which will require a minimum of transmitters and receivers;     (c) to provide a training aid which will be adaptable to all projectile type sports and games; and     (d) to provide a training aid which is small and portable.        
 
         [0012]     Still further objects and advantages will become apparent from consideration of the ensuing description and drawings.  
       SUMMARY  
       [0013]     In accordance with the above-mentioned objects and advantages, the present invention consists of an apparatus for determining the velocity of a projectile moving along a trajectory, the apparatus comprising: 
        a first infrared light curtain, formed by the first array of infrared emitters, and a sensing plane, formed by the first array of light guiding openings and the first array of infrared detectors. The first sensing plane is formed perpendicular to the trajectory. A second infrared light curtain, formed by the second array of infrared emitters, and a sensing plane, formed by the second array of light guiding openings and the second array of infrared detectors. The second sensing plane is parallel to the first sensing plane and of a known distance from the first sensing plane;     the infrared detectors producing signals indicative of a projectile passing the sensing planes. The crossing of the first sensing plane causing a START signal and the crossing of the second sensing plane causing an END signal;     processing means for receiving the START and END signals and determining the velocity of the projectile as a function of the START-END duration with the known separation of the first sensing plane and the second sensing plane; and an output means for representing the velocity of the projectile.       
 
     
    
     DRAWINGS—FIGURES  
       [0017]      FIG. 1A  shows a perspective view of a training aid embodying the apparatus of the present invention.  
         [0018]      FIG. 1B  shows a block diagram of the different elements of the apparatus.  
         [0019]      FIGS. 2A, 2B ,  2 C,  2 D and  2 E shows different views of a training aid embodying the apparatus of the present invention.  
         [0020]      FIG. 3A  shows light rays perpendicular to a detector entering.  
         [0021]      FIGS. 3B and 3C  shows a configuration of light curtains. 
     
    
     DETAILED DESCRIPTION  
       [0022]      FIG. 1A  shows a training aid consisting of a Display Unit  10  connected to a Light Curtain Unit  20  via a length of wire  42 .  
         [0023]      FIGS. 2A, 2B ,  2 C,  2 D, and  2 E shows the Light Curtain Unit  20  in more detail.  FIGS. 3B and 3C  shows a view of a light curtain. The Light Curtain Unit  20  develops a first infrared light curtain  46  made up of an array of infrared light emitting diodes  32   a . A second infrared light curtain  48  is made up of an array of infrared light emitting diodes  30   a . The distance between the light emitting diodes making up the light curtains is S,  34 . S should be slightly less than the diameter of the projectile to be measured.  
         [0024]     A first sensing plane  50  is created by an array of light guiding openings  26   a  directly below, which is located an array of infrared detectors  24   a . A second sensing plane  52  is created by an array of light guiding openings  28   a  directly below, which is located an array of infrared detectors  22   a . The separation of the sensing screen is d  36 . d is approximately 2 inches in this embodiment.  
         [0025]     The light guiding opening  26   a  and  28   a  should have a depth at least 10 times the diameter of the opening. This will ensure that only light approximately perpendicular to the detector will be able to enter the opening. This is shown graphically in  FIG. 3A . The infrared detector  24   a  and  22   a  are commercially available infrared detectors with amplification and ambient light rejection circuitry built in.  
         [0026]      FIG. 1B  shows a block diagram of the Display Unit  10  and the Light Curtain Unit  20 . The Display Unit  10  consists of a processing unit  14  such as a micro-controller or a computer. A timer  16  counter is included clocked by a frequency source  18  of frequency f. The processing unit  14  activates a display unit  12 . The display unit  12  can be any visible digit display and or audio transducer. The processing unit  14  receives a Start signal  38  and an End signal  40  from the Light Curtain Unit  20 .  
         [0027]     Operations.  
         [0028]     The first  46  and second light curtains  48  are created when the infrared light emitting diodes  30   a  and  32   a  are driven by high current pulses. The pulse rate is set to match the pulse rate required by the detectors  24   a  and  22   a . The infrared light emitting diodes  30   a  and  32   a  has a beam spread of approximately +/−15 degrees and as such after a height of around 3 feet the light curtain is more light a light cloud with the infrared beams overlapping due to beam spread. Some infrared light emitting diodes have worst beam spreading characteristics and the ‘light cloud’ would be achieved at a lower distance from the diodes.  
         [0029]     Irrespective of which types of infrared light emitting diodes are used it is important for measurement accuracy that the sensing planes only respond to light near perpendicular to the detector. To achieve this an array of light guiding openings  26   a  and  28   a  is including in the composition of the sensing planes. By forming the openings such that the depth of the opening is at least 10 times the diameter of the opening means only light traveling perpendicular to the detector can be detected.  
         [0030]     As the projectile travels through its trajectory it enters the first light curtain  46 . The projectile will scatter or reflect the infrared light. Due to the composition of the sensing plane  50 , the reflected infrared light will not activate the detector  24   a  unless the reflected infrared light is perpendicular to the detector  24   a  i.e. the projectile is directly over the detector  24   a . The projectile will enter the second light curtain  52  and again will activate the detector  22   a  when it passes directly over the detector  22   a . The relative position of the projectile to the detector to activate the detector would approximately be the same since both sensing planes are the same.  
         [0031]     As the first sensing plane  50  detects the projectile a signal START  38  is transmitted to the Display Unit  10 . As the second sensing plane  52  detects the projectile a signal END  40  is transmitted to the Display Unit  10 .  
         [0032]     The processing unit  14  initiates a count on receipt of the START  38  signal and the count is terminated on receipt of the END  40  signal. The count is updated at a frequency determined by the clock source  18 .  
         [0033]     If the count is C, the clock frequency is f and the distance separating the sensing plane is d then the velocity is given by the following:  
         X   C     =     velocity   ⁢           ⁢   in   ⁢           ⁢   miles   ⁢           ⁢   per   ⁢           ⁢   hour   ⁢           ⁢     (   mph   )           
        X=(1/17.6*d*f)+k     {17.6 is 1 mph express as inch per sec;}    {k is a constant to account for delays in the measuring loop.}    {X becomes a constant since d, f and k are known}       
 
         [0038]     The processing unit  14  calculates the velocity based on the above formula and directs the display unit  12  to display a representation of the velocity.  
         [0039]     Conclusion, Ramifications and Scope of Invention.  
         [0040]     Thus the reader will see that the velocity determining apparatus of the invention provides a portable, accurate yet economical system. Furthermore the apparatus has the additional advantages in that 
        it provides an accurate indication of a projectile&#39;s velocity;     it provides a minimum of transmitters and receivers;     it will be adaptable to all projectile type sports and games; and     it is small and portable.        
 
         [0045]     While my above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible. For example, different enclosure for the first light curtain and a separate enclosure for the second light curtain; single unit combining the display unit with the light curtain unit, etc.  
         [0046]     Accordingly, the scope of the invention should be determined not by the embodiment illustrated, but by the appended claims and their legal equivalent.