GB2208438A

GB2208438A - Apparatus for measuring the speed of a projectile

Info

Publication number: GB2208438A
Application number: GB8718633A
Authority: GB
Inventors: Tak-Hoi Wong
Original assignee: 3A ELECTRONICS Ltd
Current assignee: 3A ELECTRONICS Ltd
Priority date: 1987-08-06
Filing date: 1987-08-06
Publication date: 1989-03-30
Anticipated expiration: 2007-08-06
Also published as: GB8718633D0; GB2208438B

Abstract

Apparatus for measuring the speed of a projectile e.g. a ball comprises a first detector which is worn by a player or mounted for example on a bat and has a shock sensitive switch 7 so that when the ball is hit, a signal from the switch 7 starts a timer 5. A further detector mounted on a target has a shock sensitive switch which closes when the ball hits the target and causes a transmitter to send a signal to a receiver 4 in the first detector. The receiver 4 stops the timer 5 which then calculates the speed of the ball according to a predetermined algorithm and distance of travel. Provision may be made for inputting the distance into the timer 5, or a chart may be provided for conversion for different distances. <IMAGE>

Description

APPARATUS FOR MEASURING THE SPEED OF A PROJECTILE The present invention relates to a device for measuring the speed of a projectile such as a tennis ball, base ball, soft ball, football, basket ball, squash ball, hockey ball or golf ball.

It is known to provide a system of radar for determining the speed of a ball, and to provide a system on the ball itself for determining its speed.

Radar systems are expensive, and systems provided on the ball are limited to the particular ball and require retrieval of the ball.

The present invention provides an apparatus for measuring the speed of a projectile, comprising a first detector mountable at a point of projection of the projectile for detecting and signalling when said projectile is projected, a second detector mounted at a target for detecting and signalling when said projectile reaches said target, means for determining an elapsed time between signals from said first and second detectors and means for calculating a speed of said projectile from said elapsed time.

The first detector may be mounted on a bat or racket etc. used to hit the projectile or on an arm of the person throwing the projectile or hitting or with a bat or racket etc. The detector may also be mounted on the leg of a person kicking the projectile. The second detector may be mounted on a target at which the projectile is aimed. The detectors preferably utilise shock activated switches to signal when the projectile has been projected and has reached the target.

Alternatively, the target may comprise an infra-red beam or curtain which is detected by the second detector. When the projectile passes through the beam or- curtain, this is sensed by the second detector which signals that the projectile has reached the target.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which, Figure 1 is a schematic view of a detector/receiver of an apparatus according to the invention; Figure 2 is a schematic view of a detector of the detector/receiver of Figure 1; Figure 3 is a functional block diagram of circuitry of the receiver of Figure 1; Figure 4 is a schematic view of a detector/transmitter of an apparatus according to the invention; and Figure 5 is a functional block diagram of circuitry of the detector/transmitter of Figure 4.

In Figure 1, a detector/receiver 1 comprises a casing 2 housing a liquid crystal display 3, a UHF radio receiver 4, a timer 5, a power supply 6 and a shock sensitive switch 7. Switch 7 is shown in more detail in Figure 2. Also shown are an on/off switch 8 and a reset switch 9.

The casing 2 carries a strap (not shown) for attaching the casing to an arm or leg of a user, or to a racket handle etc. The casing may be installed in a racket handle etc. if desired.

Referring to Figure 2, a shock sensitive switch 7 comprises an electrically conducting resilient metal wire 10, typically steel, mounted at one end 10a onto a track of a printed circuit board (not shown). The wire has a dog leg 11 and carries a steel weight 12 at its opposite end 13. An electrically conducting cylinder 14 is mounted on another track of the printed circuit board and surrounds the weight 12.

When the housing 2 is subjected to shock the end 12 of the wire will swing or vibrate and the weight 12 will contact the cylinder 14 to make an electrical contact and send a signal to the timer 5.

Referring to Figure 4, a detector/transmitter 20 comprises a housing 21, a power supply 22, a tJF radio frequency transmitter 23 and a shock operated switch 24. The shock operated switch 24 comprises a resilient coiled spring 25 which is soldered at one end 28 to a track 26 on a printed circuit board 27.

The opposite end 24 of the spring 25 lays above another track 30. When the housing 21 is subjected to a shock the spring 25 will vibrate and contact the track 30 to make electrical contact between the two tracks 26, 30.

The operation of the device will now be described with particular reference to Figures 3 and 5 in its application to a tennis player. The detector/receiver 1 is mounted on the wrist of a wearer, on the arm which carries the tennis racket, and the detector/transmitter 20 is mounted on a target.

The detector transmitter is switch on, switch 8.

When the player hits the tennis ball the shock causes the switch 7 to close momentarily, sending a signal to timer 5, which begins counting. When the ball hits the target, the shock is sensed by the detector/transmitter 20, switch 24 closes momentarily and causes transmitter 23 to send a signal to the receiver 4. When receiver 4 receives the signal, it sends a stop signal to the timer 5. Timer 5 then calculates the speed of the tennis ball on the basis of a predetermined algorithm and distance of travel, and displays the calculated speed on display 3. The timer is then reset by the reset switch 9 to make ready for the next calculation.

Provision may be made for inputting the distance to be travelled by the ball into the timer 5. The timer may be arranted to calculate a speed for a fixed distance and a chart provided for conversion of the calculated result to different distances.

The switch 7 is arranged to be more sensitive than the switch 24, but the same type of switch may be used in the detector/receiver and the detector/transmitter. The receiver and transmitter may be connected by an electrical cable, or an ultrasonic signal may be transmitted between them.

The radio or ultrasonic signal may be coded to avoid interference with other devices.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims

1. Apparatus for measuring the speed of a projectile, comprising a first detector mountable at a point of projection of the projectile for detecting and signalling when said projectile is projected, a second detector mounted at a target for detecting and signalling when said projectile reaches said target, means for determining an elapsed time between signals from said first and second detectors and means for calculating a speed of said projectile from said elapsed time.

2. Apparatus as claimed in claim 1, wherein the first detector comprises a shock operated electrical switch.

3. Apparatus as claimed in claim 2, wherein the first detector is mountable on the body of a person projecting the projectile.

4. Apparatus as claimed in claim 2, wherein the first detector is mountable on a device for projecting the projectile.

5. Apparatus as claimed in any one of claims 1 to 4, wherein the second detector comprises a shock operated electrical switch.

6. Apparatus as claimed in claim 5, wherein the second detector is mountable on a said target.

7. Apparatus as claimed in any one of claims 1 to 6, wherein at least one of said detectors comprises a pendulum.

8. Apparatus as claimed in claim 7, wherein said pendulum comprises a conducting metal wire mounted at one end to form a terminal of a switch and carrying a weight at its other end, the arrangement being such that a shock causes said weight to swing to bring said wire into electrical contact with a second terminal to close the switch.

9. Apparatus as claimed in claim 7, wherein said weight is suspended within a conducting metal cylinder.

10. Apparatus as claimed in any one of claims 1 to 9, wherein at least one of said detectors comprises a resilient conductor mounted at one end to form a terminal of a switch and arranged to contact another terminal to momentarily close the switch when subjected to a shock.

11. Apparatus as claimed in claim 10, wherein the resilient conductor is a coiled spring.

12. Apparatus as claimed in any one of claims 1 to 11, wherein the means for determining the elapsed time comprises a timer which receives said signals..

13. Apparatus as claimed in claim 12, wherein the timer is housed with the first detector and signal from the second detector is transmitted to said first detector.

14. Apparatus as claimed in claim 13, wherein the transmitter is a radio transmitter and a radio receiver is provided at said first detector.

15. Apparatus as claimed in claim 1, wherein the target comprises an infra-red beam or curtain the interruption of which by the projectile is sensed by the second detector which signals that the projectile has reached the target.

16. Apparatus for measuring the speed of a projectile, comprising a first shock activated switch for signalling when the projectile has been projected, a counter activated by the signal from the first switch, a second shock activated switch for signalling when the projectile has reached a target, a transmitter for transmitting the signal from the second switch to a receiver electrically connected to the counter to determine the elapsed time between the first and second signals, means for calculating the speed of the projectile based on the elapsed time, and means for displaying the calculated speed.

17. Apparatus for measuring the speed of a projectile, substantially as hereinbefore described with reference to the accompanying drawings.