Electricity: measuring and testing – Electrical speed measuring – Including 'event' sensing means
Reexamination Certificate
2000-12-21
2002-08-20
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including 'event' sensing means
C473S222000
Reexamination Certificate
active
06437559
ABSTRACT:
The present invention relates to the use of magnetic fields to measure the speed of a moving object, and in particular, to measure the speed at which a player swings the head of a golf club.
BACKGROUND OF THE INVENTION
Golf is a highly competitive sport in which a skilled amateur can challenge his professional counterparts because the basics to a good game of golf is “all in the swing.” A player with a long drive has a distinct advantage over a player with a shorter drive and the length of the drive is greatly related to the speed at which the club hits the ball. In addition to the speed of the club when it contacts the ball, a player is also interested in a consistent “back swing time.” The back swing time is the interval of time which elapses from when the club is drawn back from the ball until the ball is driven off the tee.
Currently, optical velocity meters or Doppler radar guns are used to measure golf club speed. An optical meter requires a strip of reflective tape mounted on the club so that motion of the club can be detected by the device. The radar gun must be placed several feet from the golfer to prevent the club from striking the gun. The optical meter can measure back swing time, but the radar gun cannot. Both devices are expensive and suitable for use on a practice tee, but are not suitable for use by a golfer during the course of playing a game.
It would be desirable to provide an improved apparatus for measuring the speed of a golf club which would be inexpensive to manufacture, small in size, and useable by a player during the course of a game.
SUMMARY OF THE INVENTION
Briefly, the present invention is intended to measure the speed of an object having a magnetically conductive element by passing the conductive element through a pair of oscillating magnetic fields. Specifically, the invention is used to measure the speed of a metal club head by positioning a pair of magnetic fields to cross the path of movement of the club head either immediately before or immediately after it strikes the golf ball.
In accordance with the invention, two oscillating magnetic fields are formed with the natural frequencies of the fields being equal to each other. When a magnetically conductive element, such as the head of a golf club, passes through one of the oscillating magnetic fields, the movement of the magnetically conductive object through the field steals energy away from the field, thereby altering the natural frequency of the field. The invention includes a detector for detecting a change in the natural frequency of oscillation of each of the fields and a clock for measuring the time that elapses between the interruptions of the first and second fields. The fields are spaced a predetermined distance from each other and, therefore, the speed of the club can be calculated by dividing the distance between the fields by the time required to pass between them.
The above described method is best carried out by providing a pair of oval shaped coils etched into the surface of a printed circuit board. To maximize sensitivity, the coils can be etched into both the upper and lower surfaces of the circuit board thereby doubling the number of turns. By etching the coils at opposite ends of a single circuit board, the distance between the coils is fixed.
The device need only detect the time required to cross the two fields. It is not necessary to detect the direction of motion. The circuit can therefore be simplified by arranging the coils in series with a common capacitor to thereby insure that the frequencies of the two coils are identical. Frequency changes are detected by a phase locked loop consisting of a digital phase detector and a voltage control oscillator (VCO). The phase locked loop matches the edges of the wave from the magnetic field with that of the VCO and generates an error voltage which is fed back to the VCO to maintain the frequency of the VCO equal to the natural frequency of the magnetic field formed by the coils. When a golf club enters the field of one of the coils, the frequency of the combined coils is altered causing the VCO to adjust the error voltage in response to the frequency change.
In accordance with the invention, the output from the phase locked loop is passed through a passive filter which assists in maintaining the matched frequencies and filters out extraneous noise. The output from the filter is passed through an amplifier which amplifies any spikes in voltage caused by a change in the frequency of the oscillating magnetic fields. The output from the amplifier is passed through a comparator for detecting voltage spikes above a given threshold where the threshold is indicative of a conductive object, such as the head of a golf club entering one of the magnetic fields. The output from the comparator is directed into a microprocessor having a clock which measures the time between spikes. The time between the spikes and the distance between the magnetic fields are then used to calculate the speed, and the calculated output is then displayed on an output in miles per hour or the like.
Although the invention is disclosed as usable to measure the speed of a golf club swing, the invention can be used to measure the speed of any projectile or the device used to impart speed to a projectile. Examples of alternate uses include measuring the speed of a baseball, a baseball bat, a tennis racket, a tennis ball, a foot ball, a soccer ball, a basketball, a shot put, a javelin, a track runner, or the hands and feet of one practicing karate.
REFERENCES:
patent: 4615526 (1986-10-01), Yasuda et al.
patent: 5935014 (1999-08-01), Lindsay
Gallas James M.
Panosh Richard
Zajac Gerry W.
Lefkowitz Edward
Marsh Robert L.
Zaveri Subhash
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