GB2079496A - Automatically controlled timing system - Google Patents

Abstract

A timing system for use in water sking and allied water sports employs two timers whose operation is controlled by a magnetic sensor (22) Fig. 1 mounted on a boat, the sensor (22) being responsive to magnets (26) mounted on a number of the buoys (10, 14, 18) which define a course to be followed by the boat. The arrangement is such that one timer is started and stopped at the entrance and exit points respectively of the course whilst the second timer is started at the entrance and midway points of the course whereby the first timer provides an indication of average boat speed over the course whilst the second timer provides a a midcourse indication of boat speed. <IMAGE>

Description

SPECIFICATION A timing system This invention relates to a timing system which is particularly suitable for use in water skiing and allied water sports where a measure of boat speed is required.

The invention is especially applicable to water skiing events such as slalom and jumping in which the boat speed must be maintained within certain limits for the run to be valid. For example, in the slalom event the boat traverses a course defined by successive pairs of buoys, the boat being driven between the buoys of each pair whilst the skier executes a slalom course defined by another set of buoys. To ensure that each competitor receives the same advantage, the boat is driven at a certain prescribed speed, for example 36 m.p.h., and stop watch timing has been used in the past to ensure that the average boat speed over the course does not deviate from the prescribed speed by more than a specified amount, e.g. plus or minus 0.2 m.p.h.

The stop watch-timed period is made by an on board official using buoys at the beginning and end of the course as reference points.

Hitherto this has been considered unsatisfactory as the accuracy of timing is dependent on the official's reflexes and may vary over the course of several runs. Also the average boat speed can only be checked after the boat has completed the course.

Attempts have been made to eliminate the human element in timing but no satisfactory proposal has yet been made. One timing system which has been adopted but which did not progress beyond the experimental stage involves providing inertia-type switches on the entrance and exit buoys of the course which were intended to close in response to rocking of the buoys during passage of the boat, switch closure being effective to trigger a radio transmitter and emit a signal for reception by a receiver on the boat. This system was found to be unsatisfactory for a number of reasons, e.g. the radio transmitter carried by the buoys has to be powered by as onshore power supply source making it necessary to connect each buoy to the supply source by supply lines of considerable length.

Also, the switches were found to be unreliable in that they did not always close in response to passage of the boat.

Another proposal which has been considered is the use of infra-red beams produced between the entrance and exit buoys. However, this has been rejected because of the difficulty of powering the buoy mounted beam transmitters and receivers and associated circuitry, battery power being undesirable because of the considerable increase in the weight of the buoys and hence risk of injury to the skiers in the event of collision at speed with a heavy buoy. Moreover, there is the added complication of achieving beam alignment with receivers due to vertical and tilting motion of the buoys when disturbed by the approaching boat and choppy water, and of protecting the electrical components from the inevitable enviromental hazards.

Thus, whilst the shortcomings of hand timing to check boat speeds have been recognized for many years, no satisfactory alternative has been found.

The object of the present invention is to provide an improved timing system which is capable of meeting the requirements of water skiing and allied water sports where a measure of boat speed is required.

According to the present invention I provide a timing system comprising timing means, at least one buoy provided with a magnet, and a magnetic sensor for mounting on a boat and adapted, in response to the presence of the boat in the proximity of said buoy, to generate a signal for starting and/or stopping timing of said timing means.

In practice, there will be at least two buoys each provided with a magnet so that one buoy can be used for starting the timing means and the other for stopping the timing means. For slalom skiing, at least one set of three such buoys is conveniently provided and the timing means preferably comprises two timers so that the buoys of the or each set may be used as entrance, exit and intermediate reference points, the arrangement being such that both timers are started as the boat passes the entrance buoy, one timer is stopped as the boat passes the intermediate buoy and the second timer is stopped as the boat passes the exit buoy. Thus, the second timer provides an indication of average boat speed over the full length of the course and the first timer provides an indication of average boat speed after part of the course has been traversed.This facility is particularly advantageous as it enables mid-course corrections to boat speed to be made to ensure that the average speed over the complete course is within the specified range for the prescribed speed. In some circumstances, e.g. the ski jump event, the intermediate buoy may not be required and, in this case, only the second timer is necessary.

Preferably each magnet is provided on the respective buoy in such a way that the magnetic field strength is substantially isotropic about a vertical axis of symmetry of the buoy.

Thus, detection of the magnetic field by the sensor is not affected by rotation of the buoy about its vertical axis when water borne. Alternatively, each magnet may create an anisotropic field, e.g. a bar magnet, and in this event special provision may be necessary to restrain the buoy against rotation when water borne, the arrangement being such that the dominant component of field strength is directed generally broadside on with respect to the direction of movement of the boat along the prescribed course.

A feature of the invention in a narrower aspect thereof is the provision of means for discriminating between the magnetic fields of the buoy mounting magnets and the magnetic fields originating from other sources. In practice a major source of extraneous magnetic fields will be the engine powering the boat and, in particular, the electrical ancillaries such as ignition coils and alternator associated with the engine. Preferably such discrimination is achieved by employing a magnetic sensor having directional properties and orienting the sensor so as to minimise the influence of magnetic fields originating from the engine and maximise the influence of magnetic fields originating from the buoy mounted magnets.

In the preferred embodiment, the sensor includes an electrical coil in which a back EMF is induced by the buoy mounted magnets as the boat moves past the buoys. To some extent, the desired sensor directional property can be achieved by using an elongated coil and arranging it broadside on relative to the boat. Surprisingly however it has been found that a pronounced directional effect is obtained if the coil is provided with a core of high magnetic permeability material and the core is arranged to project beyond one end of the coil. With such an arrangement, the coil surprisingly shows a marked sensitivity in the axial direction and the coil and core are therefore disposed broadside on with respect to the boat. The core may comprise a single ferrite rod or two or more ferrite rods located alongside each other.Preferably the core extends beyond the one end of the coil by at least 100% of the axial length of the coil and in general it would appear that the greater the projection of the core from the coil the more pronounced the directional effect; however, it will be appreciated that there will be a lower limit on how short the coil can be made if a reasonably strong induced signal is to be obtained.

In practice, when used in slalom skiing, the two generally parallel rows of buoys defining the course to be traversed by the boat will each inciude entrance, exit and intermediate buoys for triggering the timers in both directions of travel. When travelling in one direction, only the buoys in one of the rows will be used for controlling the timing means. To prevent interference from the buoy mounted magnets in the other row, the sensor is preferably mounted to one side of the boat and vertically inclined so as to point generally towards the magnets in the desired row. In this way the magnets in the other row are effectively laterally offset from the axis of the sensor thereby reducing their influence on the sensor.

The present invention contemplates the use of a permanent magnet/magnetic sensor arrangement which enables a signal to be produced even when the sensor is at least two feet from the magnet. In a prototype arrangement, it has been possible to obtain output signals from the sensor at up to a range of about 14 feet and, in general, the magnet/sensor arrangement will be such that a sensor output can be obtained at a range of up to 1,0 feet. The sensitivity of the sensor device may be selectively variable to define a maximum range within which the sensor can produce an output signal in response to detection of the magnet and this range is conveniently variable between two and ten feet.Thus, for example, electronic circuitry associated with the sensing element may include a threshold detector such as a Schmitt trigger and manually operable means may be provided to adjust the threshold detector or the incoming signal level so that the threshold detector only produces an output when the sensor is within the desired range relative to the magnet.

To promote further understanding of the invention, reference is now made to the accompanying drawings in which: Figure 1 is a diagrammatic view showing the course to be traversed by a boat whilst towing a water skier; Figure 2 is an end view showing the arrangement of the boat mounted sensor relative to magnets mounted on the buoys; Figure 3 is a view of a buoy having a magnet mounted thereon; Figure 4 is a longitudinal sectional view of an electrical coil forming part of the sensor; Figure 5 is an end view of the coil shown in Fig. 4; and Figure 6 is a schematic block diagram of circuitry used in processing the signal derived from the sensor.

Referring firstly to Fig. 1, the course to be traversed by a boat 20 is defined by successive pairs of buoys 10-18. When the boat is travelling in the direction indicated by the arrow, the buoys 10 constitute an entrance gate, the buoys 1 8 constituting an exit gate and the remaining pairs of buoys act as guides. When the boat is travelling in the opposite direction, it will be appreciated that the roles of the buoys 10 and 1 8 are reversed. In accordance with the invention, each of the buoys 1 0. 14 and 1 8 is provided with a permanent magnet for detection by a sensor 22 mounted on the boat.

As shown in Fig. 3, each buoy is generally rotationally symmetric about a vertical axis and may be manufactured as a plastics moulding. Each buoy is formed with a through bore at its lower end for reception of a pin 24 or the like by means of which the buoy can be anchored in place. Although, in the case of the buoys 10, 14 and 18 the permanent magnet can be mounted in any suitable manner, as shown in Fig. 3, the permanent magnet is conveniently in the form of a ring magnet which fits over the reduced diameter lower end of the buoy and is held in place by the pin 24. The magnet 26 produces a substantially isotropic magnetic field with respect to the vertical axis so that detection of the magnets by the sensor 22 is not affected by rotation of the buoys.

As shown in Fig. 2, the sensor 22 is mounted on one side of the boat and is conveniently supported in a bracket 28 which allows the sensor 22 to be tilted about a substantially horizontal fore-and-aft axis to allow the attitude of the sensor to be varied and, in particular, allow the sensor axis to be directed towards the magnets 26 associated with the buoys 10, 14 and 1 8 disposed on that side of the boat. Thus, as shown in Fig.

2, the sensor axis 30 is directed towards the magnets associated with the buoys on the left hand side of the course. When the boat is driven in the opposite direction however, it will be appreciated that the sensor axis 30 will then be directed towards the magnets associated with the buoys on the right hand side. The magnets are all of the same field strength and, it will be noted, are located beneath water level. Because the sensor 22 is mounted on one side of the boat and because the magnets all have the same strength, the sensor 22 can discriminate to some extent between the buoys of the left hand side and those on the right hand side; however, as will be explained further below, the discrimination is increased substantially by virtue of the inclination of the sensor 22 and its construction.

Referring now to Figs. 4 and 5, the sensor includes an electrical coil 32 wound on a cylindrical former 34 having end flanges 36.

The coil has a core of magnetically permeable material constituted, in the illustrated embodiment, by three ferrite rods 38 arranged in the manner shown so that the rods project substantially beyond the forward end of the coil, i.e. that end directed towards the magnets in use. This arrangement of the core has, as previously mentioned, been found to give a pronounced directional effect, i.e. the sensor being considerably more sensitive to magnetic sources lying along its axis. Thus, by appropriate location of the sensor, any extraneous magnetic fields emanating from the boat enging and electrical ancillaries may be eliminated.

As the sensor moves past one of the buoy mounted magnets, a back EMF will be induced in the coil 32 and this signal may be processed by the circuitry shown in Fig. 6 so as to provide control signals for a timing device. As shown in Fig. 6, the coil signal is fed to an amplifier 40 to increase the signal level and then to a filter 42 for filtering out extraneous RF signals. The circuitry may include a suitable feedback loop (not specifically shown) so as to filter out other undesirable transient signals which may arise from, for example, the ignition coil and alternator. The filtered signal is applied to a threshold detector 44 which may be in the form of a Schmitt trigger so that the detector 44 only produces an output in response to an input signal whose magnitude exceeds the threshold level (which may be adjustable).The output of the detector 44 is connected to a monostable multivibrator 46 which, in response to an output signal from the detector, provides a short duration pulse (for example 0.25 seconds) which is fed to a discriminator 48. The discriminator 48 serves to determine whether the pulse produced by the multivibrator 46 is the first, second or third of a series generated during one traverse of the course by the boat.

If the pulse corresponds to movement of the boat past the left hand buoy 10 and therefore constitutes the first pulse, the discriminator 48 produces simultaneous signals which are fed to two timers 50, 52 so as to initiate timing by boat timers. In response to the second pulse, the discriminator stops the timer 50 and also a display 54 associated with the timer 50. The second pulse, of course, corresponds to movement of the boat past the left hand buoy 14 and therefore the time recorded on the display 54 represents the time taken for the boat to move from buoy 10 to buoy 14. In response to the third pulse, the discriminator 48 stops timing of the timer 52 and also the display 56 associated with timer 52 thereby recording on display 56 the time taken for the boat to move from buoy 10 to buoy 18.

Thus, during each run, the display 54 provides a mid-course indication of the boat speed and the display 56 provides an overall indication of boat speed. The content of the displays 54 and 56 may be maintained until deliberately reset by means of a reset button accessible to an official. In practice, the reset button will be operated between successive runs after the times on the displays 54 and 56 have been noted. In a modification, the reset may take place automatically, e.g. after expiry of a predetermined time.

As described hereinbefore, the magnets are mounted on the buoys. However, they may be associated with the buoys in other ways, e.g.

clipped on, suspended from or mounted within the buoys.

From the foregoing, it will be noted that the invention provides an automatic timing system which, as well as providing an indication of the average boat speed over the complete course, may also provide a mid-course indication so that if at that stage the boat speed deviates from the prescribed speed, suitable adjustment can be made in order to compensate for the deviation and achieve an overall speed within the prescribed limits.

Claims (12)

1. A timing system comprising timing means, at least one buoy provided with a magnet, and a magnetic sensor for mounting on a boat and adapted, in response to the presence of the boat in the proximity of said buoy, to generate a signal for starting and/or stopping timing of said timing means.

2. A system as claimed in Claim 1 in which there are at least two buoys each provided with a magnet so that one buoy can be used for starting the timing means and the other for stopping the timing means.

3. A system as claimed in Claim 1 in which at least one set of three of the aforesaid buoys is provided and in which the timing means comprises two timers so that the buoys of the or each set may be used as entrance, exit and intermediate reference points, the arrangement being such that both timers are started as the boat passes the entrance buoy, one timer is stopped as the boat passes the intermediate buoy and the second timer is stopped as the boat passes the exit buoy.

4. A system as claimed in Claim 1, 2 or 3, in which each magnet is provided on the respective buoy in such a way that the magnetic field strength is substantially isotropic about a vertical axis of symmetry of the buoy.

5. A system as claimed in any one of Claims 1-4 including means for discriminating between the magnetic fields of the buoy mounting magnets and the magnetic fields originating from other sources.

6. A system as claimed in Claim 5 in which such discrimination is achieved by employing a magnetic sensor having directional properties.

7. A system as claimed in any one of Claims 1-6 in which the sensor includes an electrical coil in which a back EMF is induced by the buoy mounted magnets as the boat moves past the buoys.

8. A system as claimed in Claim 7 in which the cvoil is provided with a core of high magnetic permeability material and the core is arranged to project beyond one end of the coil.

9. A system as claimed in Claim 8 in which the core comprises a single ferrite rod or two or more ferrite rods located alongside each other.

10. A system as claimed in Claim 8 or 9 in which the core extends beyond the one end of the coil by at least 100% of the axial length of the coil.

11. A system as claimed in any one of Claims 1-10 in which the magnet/sensor arrangement is such that a detectable signal is produced by the sensor at ranges of up to at least 10 feet (approx. 3,000 mm).

12. A system as claimed in any one of Claims 1-10 including means for selectively determining with respect to the magnet the maximum range at which the sensor can produce a detectable signal.

1 3. A timing system substantially as here it before described with reference to, and as shown in, the accompanying drawings.